Fact-checked by Grok 2 weeks ago

Biophysics

Biophysics is the branch of science that employs the principles, methods, and theories of physics to investigate living organisms and biological processes.^[1] It serves as an interdisciplinary field at the intersection of biology, physics, chemistry, mathematics, engineering, genetics, physiology, and medicine, focusing on quantitative analyses of biological phenomena such as protein and DNA structure, membrane physics, electrophysiology, gene expression, cellular metabolism, and macromolecular interactions.^[1] The origins of biophysics trace back to the mid-19th century in Germany, where polymath scientists like Hermann von Helmholtz applied physical laws to physiological studies, challenging vitalism and promoting a mechanistic view of life.^[2] Early milestones included Luigi Galvani's experiments on "animal electricity" in the late 18th century and the publication of the first English biophysics textbook in 1921 by David Burns.^[2] The modern field gained momentum in the mid-20th century, spurred by Erwin Schrödinger's influential 1944 book What is Life?, which argued that biological systems could be understood through physical principles like quantum mechanics.^[2] Post-World War II advancements in instrumentation, such as X-ray crystallography and nuclear magnetic resonance spectroscopy, fueled growth, leading to the establishment of dedicated biophysics programs at universities including the University of Michigan in the 1930s and Johns Hopkins University in 1957.^[3]^[4]^[1] Contemporary biophysics encompasses diverse subfields, including biophysical approaches to cell biology, which use physics-based methods to analyze cellular components; computational and theoretical biophysics, involving molecular modeling and multi-scale simulations for drug design; membrane biophysics, studying ion channels and lipid structures; structural biology, employing techniques like cryo-electron microscopy and NMR; and single-molecule biophysics, probing individual biomolecular dynamics.^[5] These areas enable the exploration of complex biological systems, from molecular interactions to network organization across scales.^[5] Biophysics has profoundly impacted medicine and technology, underpinning diagnostic tools such as MRI, CT scans, PET scans, and ultrasound imaging for disease detection.^[6] It has driven innovations in life-saving devices, including kidney dialysis machines, cardiac pacemakers, and defibrillators, while contributing to treatments for conditions like diabetes and cancer through radiation therapy and vaccines.^[6] In biotechnology, biophysical techniques facilitate drug discovery by revealing protein folding, bioenergetics, and interactions, supporting personalized medicine and the development of targeted therapies.^[7] Landmark achievements, such as the 1953 elucidation of DNA's double-helix structure via X-ray diffraction, exemplify how biophysics integrates physical tools to unlock biological secrets, fostering advancements in genomics, bioremediation, and biofuel production.^[6]

Definition and Scope

Core Concepts

Biophysics is defined as the application of physical principles, methods, and theories to the study of biological systems and processes, spanning molecular, cellular, and organismal levels. This discipline quantifies biological phenomena by integrating tools from physics, such as mechanics, thermodynamics, and statistical analysis, to elucidate mechanisms that govern life. Unlike traditional biology, which often focuses on descriptive observations, biophysics emphasizes quantitative modeling and prediction of biological functions based on underlying physical laws.^[8] Central to biophysics are concepts like structure-function relationships in biomolecules, where the three-dimensional architecture of proteins, nucleic acids, and lipids directly influences their biological roles. Energy transfer in living systems, governed by principles of thermodynamics and quantum mechanics, enables processes such as photosynthesis and cellular respiration, converting chemical or light energy into usable forms. Mechanical properties of biological materials, including elasticity and viscoelasticity, allow tissues and cells to withstand stresses while maintaining functionality.^[9]^[10] Representative examples illustrate these concepts: protein folding dynamics, where random coils achieve native conformations through energy minimization and hydrophobic interactions, as studied in thermodynamic models. Ion channel gating involves voltage- or ligand-induced conformational changes that control ion flow across membranes, critical for nerve signaling. DNA mechanics encompasses the bending, twisting, and stretching of the double helix, which facilitates processes like replication and transcription. Early insights into bioelectricity, such as Luigi Galvani's 18th-century frog leg experiments demonstrating electrical stimulation of muscle contraction, foreshadowed these quantitative approaches.^[11]^[12]^[13]^[14] Biophysics uniquely bridges spatial and temporal scales, from atomic interactions driving molecular assembly to emergent behaviors in whole organisms, providing a unified framework for understanding complexity in living systems.^[15]

Interdisciplinary Nature

Biophysics emerged as a distinct interdisciplinary field in the mid-20th century, driven by concurrent advances in physics and biology that necessitated a unified approach to studying living systems. Key influences included the development of electron microscopy in the 1940s, which enabled high-resolution imaging of biological structures at the nanoscale, such as viral particles and cellular components, and the 1953 discovery of the DNA double helix by Watson and Crick, which highlighted the need for physical principles to explain molecular architecture and function.^[16]^[17] These milestones, alongside post-World War II interest in radiobiology and molecular mechanisms, fostered biophysics as a bridge between quantitative physical sciences and the complexities of life processes.^[16] At its core, biophysics integrates physics, biology, chemistry, and mathematics to model and analyze biological phenomena, applying rigorous physical laws to problems traditionally viewed through a biological lens. For instance, quantum mechanics elucidates the near-perfect efficiency of photosynthesis, where excitons in light-harvesting complexes exploit quantum superposition to transfer energy rapidly and without loss to reaction centers in chloroplasts.^[18] Similarly, fluid dynamics principles describe blood flow in vascular systems, revealing how shear stress on endothelial cells regulates vessel dilation via nitric oxide production and influences processes like angiogenesis and plaque formation in atherosclerosis.^[19] These integrations demonstrate biophysics' role in providing mechanistic insights that transcend disciplinary boundaries, often incorporating mathematical frameworks for simulation and prediction.^[20] Biophysicists facilitate essential collaborations across fields, serving as intermediaries who design experiments with biologists—such as incorporating biophysical sensors into cellular studies—and develop theoretical models with physicists to interpret data on molecular dynamics.^[21] This teamwork accelerates discoveries, as seen in joint efforts to model protein folding or neural signaling, where biologists provide contextual expertise and physicists contribute analytical tools.^[20] However, interdisciplinarity presents challenges, particularly the demand for dual expertise that combines quantitative analysis, such as statistical mechanics and computational modeling, with biological intuition to interpret experimental outcomes in living systems.^[22] Training programs must address this by balancing curricula that sustain interest in both domains, ensuring practitioners can navigate the field's hybrid demands without siloing knowledge.^[22]

Historical Development

Foundations in Early Science

The foundations of biophysics trace back to the 17th century, when early scientists began applying principles of mechanics to biological systems. Galileo Galilei, in his 1638 work Dialogues Concerning Two New Sciences, explored the biomechanical implications of scaling laws, noting that the strength of bones in larger animals must increase disproportionately to their size to support weight, thereby laying groundwork for understanding structural adaptations in living organisms.^[23] Similarly, William Harvey's 1628 treatise Exercitatio Anatomica de Motu Cordis et Sanguinis in Animalibus described blood circulation using physical analogies, likening the heart to a mechanical pump that propels blood through a closed system, challenging prevailing Galenic views and introducing quantitative reasoning to physiological processes. These contributions marked an initial shift toward viewing biological phenomena through the lens of classical physics, emphasizing observable forces and motions over purely vitalistic explanations. The 19th century saw accelerated integration of physical laws into biology, particularly through studies of energy and cellular function. The formulation of cell theory by Matthias Schleiden in 1838 and Theodor Schwann in 1839, later extended by Rudolf Virchow in 1855, established cells as the fundamental units of life, influencing biophysical perspectives by framing cellular mechanics—such as division, structure, and force generation—as amenable to physical analysis.^[24] Hermann von Helmholtz advanced this integration in his 1847 paper Über die Erhaltung der Kraft, where he applied the principle of energy conservation to muscle work, demonstrating that the heat produced during contraction, the mechanical work output, and the chemical energy from metabolism are interconvertible without loss, thus quantifying physiological efficiency.^[25] Helmholtz further contributed by measuring nerve conduction velocity in 1850 using a frog sciatic nerve preparation, reporting speeds of approximately 27 meters per second, which provided empirical data on signal transmission and highlighted the applicability of physical measurement techniques to neural processes.^[26] Parallel developments in electrophysiology built on these ideas, with Julius Bernstein's 19th-century investigations into bioelectricity laying precursors to membrane theories. As a student of Emil du Bois-Reymond, Bernstein developed the differential rheotome in 1868 to isolate action currents in nerves and muscles, enabling precise recordings of electrical signals during physiological activity and establishing quantitative methods for studying excitability.^[27] These efforts culminated in broader debates on vitalism, where the rise of thermodynamics in the mid-19th century—exemplified by Helmholtz's work and James Prescott Joule's experiments on heat equivalence—challenged the notion of a non-physical life force by showing that vital processes, like fermentation and respiration, adhere to universal energy laws, paving the way for a mechanistic biophysics.^[28] This transition underscored biophysics' emergence as a discipline grounded in empirical, physical explanations of life.

Key Milestones in the 20th Century

In the 1920s and 1930s, the development of the ultracentrifuge by Theodor Svedberg marked a significant advance in determining the molecular weights of proteins, enabling precise measurements of macromolecules like hemoglobin and casein through sedimentation equilibrium and velocity techniques.^[29] Svedberg's invention, for which he received the 1926 Nobel Prize in Chemistry, provided biophysical insights into the size and purity of biological colloids, laying groundwork for studying protein structures. Erwin Schrödinger's 1944 book What Is Life? introduced quantum biology concepts to explain hereditary stability and order in living systems, positing that life maintains negative entropy through molecular-scale physical processes like aperiodic crystals for genetic information storage. This work inspired physicists and biologists to apply quantum mechanics and statistical physics to biological phenomena, influencing the molecular biology revolution.^[30] In the 1950s, X-ray diffraction studies by Rosalind Franklin and Maurice Wilkins produced critical images, such as Photo 51 in 1952, revealing the helical structure of DNA fibers and providing key data on its double-helical form with a 3.4 nm pitch.^[31] These findings, shared in 1953, were instrumental in elucidating DNA's structure alongside contributions from James Watson and Francis Crick, advancing biophysical understanding of genetic material.^[32] The institutionalization of biophysics accelerated in the late 1950s, with the Biophysical Society in the United States formally founded in 1958 following the First National Biophysics Conference in 1957, which drew nearly 500 attendees and established a dedicated forum for the field.^[33] Internationally, the first International Biophysics Congress convened in Stockholm in 1961, attended by over 1,000 delegates from 26 countries, fostering global collaboration and leading to the formation of the International Organization for Pure and Applied Biophysics (IOPAB).^[34] The Hodgkin-Huxley model, published in 1952, quantitatively described the ionic mechanisms underlying action potentials in squid giant axons using voltage-clamp data to formulate equations for sodium and potassium conductances, earning Alan Hodgkin and Andrew Huxley the 1963 Nobel Prize in Physiology or Medicine. This model was expanded in the 1960s and 1970s through computational simulations and further electrophysiological studies, becoming a cornerstone for excitable membrane biophysics. In 1976, Erwin Neher and Bert Sakmann developed the patch-clamp technique, allowing high-resolution recording of single-ion channel currents in cell membranes by isolating membrane patches with glass micropipettes, which revolutionized the study of ion channel function and earned them the 1991 Nobel Prize in Physiology or Medicine. This method enabled precise measurements of channel gating and conductance, transforming cellular biophysics in the late 20th century.

Fundamental Principles

Application of Physical Laws

Biophysics adapts classical and quantum physical laws to elucidate the mechanics of biological systems, where these principles provide the theoretical framework for understanding motion, fields, and transport at molecular and macroscopic scales. In biological contexts, these laws are often modified to account for the viscoelastic properties of tissues, the ionic composition of fluids, and the quantum effects in confined environments, enabling predictions of phenomena from cellular signaling to organismal movement. Newton's laws of motion form the cornerstone of biomechanics, describing the force balances that govern muscle contraction and locomotion. During muscle contraction, the sliding filament theory integrates Newton's second law (F = ma), where the net force from actin-myosin cross-bridges accelerates the shortening of sarcomeres, balancing internal tensions against external loads to produce controlled motion. In locomotion, Newton's third law explains propulsion through ground reaction forces equal and opposite to limb forces, as seen in bipedal walking where momentum conservation maintains stability during stride cycles. These applications highlight how inertial and frictional forces dictate energy efficiency in biological movement. Electromagnetism underpins bioelectric phenomena, with Maxwell's equations adapted to describe the propagation of electric fields in nerves and cardiac tissues immersed in conductive ionic solutions. In neural action potentials, the quasi-electrostatic approximation of Maxwell's equations (∇ · D = ρ, ∇ × E = -∂B/∂t ≈ 0 for low frequencies) models transmembrane currents as volume conductors, predicting signal propagation speeds along axons. Similarly, in the heart, these equations simulate the electrocardiogram by resolving extracellular potentials from synchronized cardiomyocyte depolarizations, accounting for tissue anisotropy and boundary conditions at the body surface. Quantum mechanics reveals non-classical behaviors in biological reactions, particularly tunneling, which enables particles to traverse energy barriers otherwise prohibitive at physiological temperatures. In enzyme catalysis, proton tunneling accelerates hydrogen transfer reactions, such as in alcohol dehydrogenase, where wavefunction overlap between reactant and product states lowers the effective activation energy, enhancing reaction rates by orders of magnitude compared to classical predictions. Electron transfer in cellular respiration, exemplified by the mitochondrial electron transport chain, relies on quantum tunneling between iron-sulfur clusters in complex I, facilitating rapid charge separation over distances of 10-14 Å with minimal thermal activation. A key application of classical mechanics in biophysics is the modeling of protein elasticity using Hooke's law, which posits that the restoring force F in a deformed elastic element is linearly proportional to the displacement x from equilibrium: F = -kx, where k is the stiffness constant. This law derives from the harmonic approximation of the potential energy landscape for small perturbations; consider a protein domain with potential energy U(x) expanded via Taylor series around the minimum at x=0: U(x) ≈ U(0) + (dU/dx)|{x=0} x + (1/2)(d²U/dx²)|{x=0} x². At equilibrium, the linear term vanishes (dU/dx|{x=0} = 0), yielding U(x) ≈ (1/2) k x² with k = d²U/dx²|{x=0}, so the force F = -dU/dx = -k x. In biology, this models the entropic elasticity of unfolded polypeptide chains or the enthalpic springs in folded domains; for instance, the giant protein titin in muscle sarcomeres behaves as a worm-like chain with effective spring constants around 100-1000 pN/nm, absorbing shock during contraction to prevent sarcomere overstretching and damage. Another example is the immunoglobulin domains in titin or spectrin in red blood cells, where Hookean behavior maintains cytoskeletal integrity under shear stresses, with unfolding forces measured at 100-200 pN before nonlinear effects dominate.^[35] Molecular transport within cells adheres to the diffusion equation, ∂C/∂t = D ∇²C, where C is concentration, t time, D the diffusion coefficient, and ∇² the Laplacian operator, capturing the random walk of solutes driven by thermal fluctuations. This partial differential equation arises from combining Fick's first law (flux J = -D ∇C) with the continuity equation (∂C/∂t = -∇ · J), yielding the parabolic form that predicts spreading from high to low concentration regions, as in the passive diffusion of ions across the cytoplasm or nutrients through membranes. In cellular contexts, D values range from 10^{-12} m²/s for proteins in viscous cytosol to 10^{-9} m²/s for small ions in water, establishing timescales for processes like signaling molecule dispersal over microns in seconds to minutes.

Thermodynamic and Statistical Mechanics

The first law of thermodynamics, expressing the conservation of energy, governs energy transformations in biological systems, ensuring that the total energy remains constant during metabolic processes. In cells, this principle manifests in the conversion of chemical energy from nutrient breakdown, such as glucose oxidation, into forms like ATP, which powers mechanical work in processes including molecular transport and biosynthesis, without net energy creation or destruction. Biological cells function as open systems where energy inflows from metabolism balance outflows through heat dissipation and work, maintaining overall conservation. The second law of thermodynamics introduces entropy as a measure of disorder, stating that entropy in an isolated system increases, but in open biological systems, local entropy decreases—such as during the ordered self-assembly of proteins or nucleic acids—are possible through coupling to entropy-increasing processes elsewhere, like metabolic waste heat production. In self-assembly, entropy drives the exploration of conformational space, with stochastic relaxation enabling transitions between states, as seen in the formation of viral capsids or enzyme complexes where informational constraints limit degeneracy. Biomolecular reactions, including those central to cellular function, are quantified by changes in Gibbs free energy, defined as ΔG = ΔH - TΔS, where ΔH is the enthalpy change, T is the absolute temperature, and ΔS is the entropy change; a negative ΔG indicates a spontaneous process under constant temperature and pressure. In ligand binding, such as a small molecule docking to a protein receptor, the binding free energy ΔG° = -RT ln K_b (with R as the gas constant and K_b the binding constant) determines affinity, often balancing enthalpic gains from hydrogen bonds or van der Waals interactions against entropic losses from reduced conformational flexibility or solvent release. For instance, in induced-fit binding mechanisms, ΔG° values are typically around -5 to -15 kcal/mol and can be primarily enthalpically driven through favorable interactions like hydrogen bonding.^[36] Statistical mechanics bridges microscopic molecular behaviors to macroscopic thermodynamic properties in biophysics, with the Boltzmann distribution providing the probability P_i of a system occupying a state i with energy E_i as P_i = (1/Z) e^{-E_i / kT}, where k is Boltzmann's constant and T is temperature; this distribution arises from maximizing entropy subject to fixed average energy, weighting low-energy conformations more heavily. In molecular conformations, such as those of RNA secondary structures or lattice-model proteins, the Boltzmann distribution predicts mutation-induced shifts by favoring high-frequency alternative states near the minimum-free-energy fold, outperforming purely phenotypic predictions in evolutionary contexts. Ensemble averaging, a core application, computes properties like average energy ⟨E⟩ = -∂(ln Z)/∂β (with β = 1/kT) over all conformations weighted by their Boltzmann probabilities, essential for protein folding where it reveals cooperative transitions and stability without simulating dynamics. The partition function Z = \sum_i e^{-E_i / kT} encapsulates the statistical weights of all accessible states, derived by considering a system in thermal contact with a reservoir: the probability of state i is proportional to the reservoir's degeneracy Ω(E_{tot} - E_i) ≈ e^{(E_{tot} - E_i)/kT}, leading to normalization Z = \sum_i e^{-E_i / kT} after ensemble averaging. In biology, Z sums over conformational states of biomolecules like proteins, but the exponential number of states (often >10^{100}) limits exact computation, necessitating approximations such as mean-field theories or reduced models that focus on native contacts; for disordered proteins, it highlights entropic contributions to transitions. The fluctuation-dissipation theorem extends this framework to relate equilibrium fluctuations, such as thermal noise in molecular concentrations, to dissipative responses, applied in biophysics to quantify cellular noise in processes like ion channel gating or colloidal motion within cells, where violations indicate non-equilibrium conditions. In active biological matter, including cytoskeletal filaments or microbial swarms, non-equilibrium thermodynamics describes sustained entropy production far from equilibrium, driven by ATP hydrolysis to maintain directed motion and pattern formation, contrasting passive systems.

Methods and Techniques

Experimental Approaches

Experimental approaches in biophysics encompass a suite of laboratory techniques designed to probe biological systems at molecular, cellular, and supramolecular scales by measuring physical properties such as forces, energies, distances, and currents. These methods rely on principles from physics, including optics, electromagnetism, and thermodynamics, to provide quantitative insights into dynamic processes that are often inaccessible to traditional biochemical assays. By enabling direct observation and manipulation of biomolecules in near-native conditions, these techniques have revolutionized the understanding of life's machinery, from protein folding to membrane transport. Spectroscopy techniques are fundamental for elucidating biomolecular structures and dynamics without disrupting the sample. Nuclear magnetic resonance (NMR) spectroscopy determines high-resolution atomic structures of proteins and nucleic acids in solution by exploiting the magnetic properties of atomic nuclei, revealing conformational ensembles and transient states that crystallography might miss. Fluorescence spectroscopy, often at the single-molecule level, tracks real-time dynamics such as enzyme turnover or protein conformational changes through the emission of light from fluorophore-labeled molecules. A key variant is Förster resonance energy transfer (FRET), which measures distances between donor and acceptor fluorophores in the 2–8 nm range, allowing quantification of intramolecular distances or intermolecular interactions with angstrom precision; for instance, single-molecule FRET (smFRET) has been used to monitor folding pathways of RNA and proteins, avoiding ensemble averaging artifacts.^[37] Microscopy methods extend these capabilities to visualize and manipulate structures at the nanoscale. Atomic force microscopy (AFM) employs a sharp cantilever tip to scan surfaces, generating topographic images with sub-nanometer resolution and simultaneously measuring mechanical properties like stiffness and adhesion in living cells or isolated biomolecules; it has been pivotal in mapping the cytoskeleton's architecture and unfolding forces of individual proteins.^[38] Optical tweezers use focused laser beams to trap and displace microscopic particles, such as single DNA molecules or motor proteins, applying piconewton forces while tracking displacements with nanometer accuracy; this has enabled studies of molecular motors like kinesin walking along microtubules, revealing stepping mechanisms and force-velocity relationships.^[39] Electrophysiology techniques directly interrogate electrical signaling in biological membranes. The voltage-clamp method, pioneered by Hodgkin, Huxley, and Katz, holds a cell's membrane potential constant using feedback electrodes while recording ionic currents through ion channels; this isolates channel kinetics, such as activation and inactivation rates, as seen in squid axon studies where sodium and potassium currents were characterized with millisecond temporal resolution. Modern implementations, like patch-clamp variants, apply this to single channels in isolated patches, quantifying conductance and selectivity for drug screening and disease modeling. Cryo-electron microscopy (cryo-EM) has transformed structural biology by imaging flash-frozen biological samples in vitreous ice, achieving near-atomic resolution (better than 3 Å) for large complexes without crystallization. Its development, recognized by the 2017 Nobel Prize in Chemistry awarded to Jacques Dubochet, Joachim Frank, and Richard Henderson, involved innovations in sample vitrification, image processing algorithms, and detector technology, enabling visualization of dynamic states in proteins like ion channels and ribosomes.^[40] Biophysical assays provide thermodynamic insights into interactions. Isothermal titration calorimetry (ITC) measures heat changes upon sequential ligand injections into a biomolecule solution, yielding binding affinities (Kd from nM to mM), stoichiometries, and enthalpy/entropy contributions in a single experiment; it has been essential for validating protein-ligand interactions in drug discovery, distinguishing specific from nonspecific binding.

Computational and Modeling Tools

Computational and modeling tools in biophysics encompass a range of algorithms and software designed to simulate dynamic processes at molecular and supramolecular scales, providing predictive insights into biological phenomena that are often inaccessible to direct experimentation. These tools leverage numerical methods to approximate physical laws governing biomolecular interactions, enabling the exploration of conformational changes, binding events, and transport mechanisms in complex environments. By integrating stochastic elements and hierarchical approximations, they bridge atomic-level details with larger-scale behaviors, facilitating the design of therapeutic interventions and the interpretation of experimental data. Molecular dynamics (MD) simulations form a foundational approach in computational biophysics, solving Newton's equations of motion to track the time evolution of atomic positions in proteins and other biomolecules under defined force fields. Force fields such as CHARMM parameterize interatomic potentials to represent bonded and non-bonded interactions, including van der Waals forces, electrostatics, and torsional energies, allowing for atomistic modeling of protein folding, stability, and ligand binding in explicit solvent environments.^[41] These simulations typically span nanoseconds to microseconds, revealing transient states like partially unfolded intermediates that inform biophysical mechanisms.^[42] To account for thermal fluctuations and solvent effects, MD often employs Langevin dynamics, which incorporates frictional damping and random forces to mimic Brownian motion. The governing equation is

m \frac{d\mathbf{v}}{dt} = -\gamma \mathbf{v} + \mathbf{F} + \xi(t),

where m is the particle mass, \mathbf{v} is velocity, \gamma is the friction coefficient (typically 0.001–0.01 ps^{-1} for water-like biological solvents), \mathbf{F} is the systematic force from the potential, and \xi(t) is a Gaussian white noise term with \langle \xi(t) \xi(t') \rangle = 2\gamma k_B [T](/page/Temperature) \delta(t - t') to satisfy the fluctuation-dissipation theorem at temperature T.^[43] This stochastic integration enhances sampling efficiency in viscous biological media, such as crowded cellular cytoplasms.^[44] Monte Carlo (MC) methods complement MD by focusing on equilibrium properties through stochastic sampling of configuration space, particularly useful for navigating rugged energy landscapes in protein folding. These algorithms generate trial moves—such as rotations, translations, or residue mutations—according to a probability distribution, accepting or rejecting them via the Metropolis criterion to maintain Boltzmann weighting: acceptance probability \min(1, \exp(-\Delta E / k_B T)), where \Delta E is the energy change.^[45] In biophysics, MC excels at exploring folding pathways and disordered states, using implicit solvent models to reduce computational cost while capturing entropic contributions to stability. Replica-exchange variants enhance ergodic sampling by swapping configurations between temperature ladders, accelerating convergence for systems like multi-domain proteins.^[46] Multiscale modeling addresses the limitations of single-resolution approaches by coupling simulations across length and time scales, from quantum mechanics/molecular mechanics (QM/MM) hybrids to continuum representations. In QM/MM, a reactive core (e.g., enzyme active site) is treated quantum mechanically for electronic structure and bond breaking, while the surrounding protein and solvent use classical molecular mechanics for efficiency, with boundary schemes like electrostatic embedding to handle interactions.^[47] This hybrid enables accurate prediction of reaction barriers in biophysical processes, such as proton transfer in photosystems. At coarser scales, continuum models approximate solvent as a dielectric medium and macromolecules as smoothed density fields, solving Poisson-Boltzmann equations for electrostatic potentials to study ion channels or membrane deformations without atomic detail.^[48] These methods scale to cellular-level phenomena, integrating discrete events with fluid dynamics. Machine learning has revolutionized biophysical modeling, exemplified by AlphaFold, introduced in 2020, which predicts protein structures from sequences with near-experimental accuracy by training on evolutionary data and structural databases. AlphaFold integrates biophysical constraints, such as stereochemical feasibility and residue-residue distance distributions derived from physical principles, within its attention-based neural network architecture to generate confident 3D models. A major update, AlphaFold3, released in May 2024, extends these capabilities to predict the joint structures of biomolecular complexes, including proteins with DNA, RNA, ligands, and ions.^[49]^[50] This approach has democratized structure prediction, aiding drug discovery by forecasting complexes that obey thermodynamic stability. Models from such tools are routinely validated against experimental structures from techniques like X-ray crystallography.

Major Subfields

Molecular and Structural Biophysics

Molecular and structural biophysics investigates the physical principles governing the architecture, conformational dynamics, and interactions of biomolecules such as nucleic acids, proteins, and lipid membranes at the atomic and molecular scales. This subfield employs theoretical models, simulations, and high-resolution experimental techniques to elucidate how structural features influence biological function, including folding pathways, binding affinities, and mechanical stability. By integrating concepts from statistical mechanics and quantum chemistry, researchers quantify properties like flexibility, energy landscapes, and intermolecular forces that underpin processes such as replication, signaling, and transport. For nucleic acids, DNA's structural integrity relies on its mechanical properties, modeled as a semi-flexible polymer using the worm-like chain framework, where the persistence length—typically around 50 nm under physiological conditions—characterizes the molecule's resistance to bending due to electrostatic repulsion and thermal fluctuations.^[51] Supercoiling mechanics further modulates DNA topology, introducing torsional stress that facilitates looping and compaction; negative supercoils, generated by enzymes like topoisomerases, reduce writhe and twist to promote site-specific interactions essential for gene regulation.^[52] These models predict that supercoiling alters local curvature, with experimental validations showing plectonemic structures under tension that enhance accessibility for transcription factors.^[53] In proteins, allostery enables cooperative responses to ligands through conformational shifts propagated across distant sites, as described by the Monod-Wyman-Changeux (MWC) model, which posits equilibrium between tense (T) and relaxed (R) states with symmetric subunit interactions.80285-6) This framework explains sigmoidal binding curves in hemoglobin, where oxygen affinity increases via subunit rearrangements, quantified by the allosteric constant L = [T]/[R]. Ramachandran plots delineate allowable backbone dihedral angles (\phi, \psi) based on steric constraints, revealing preferred regions for \alpha-helices (\phi \approx -[60](/page/60)^\circ, \psi \approx -[45](/page/45)^\circ) and \beta-sheets (\phi \approx -120^\circ, \psi \approx 120^\circ) that guide folding predictions and validation of structures from X-ray crystallography.80023-6) Lipid membranes exhibit fluidity modulated by composition and temperature, undergoing phase transitions from ordered gel (L_\beta) to disordered liquid-crystalline (L_\alpha) states, with the transition temperature T_m for dipalmitoylphosphatidylcholine around 41°C, influencing permeability and protein embedding.90020-0) Cholesterol intercalation broadens this transition, creating intermediate liquid-ordered phases that enhance bilayer rigidity while maintaining lateral mobility, as evidenced by fluorescence recovery after photobleaching studies showing diffusion coefficients of 1–10 \mum²/s in fluid phases. Single-molecule techniques, such as optical tweezers, have revealed heterogeneous unfolding pathways in proteins like ubiquitin, where force ramps expose intermediate states with lifetimes of milliseconds and rupture forces up to 200 pN, highlighting rugged energy landscapes that prevent aggregation. These insights inform drug design by identifying transient pockets—cryptic binding sites exposed during dynamics—that can be targeted to stabilize inactive conformations, as in inhibitors binding allosteric pockets of kinases with affinities in the nanomolar range.90566-3) Enzyme function is quantitatively described by Michaelis-Menten kinetics, derived from the steady-state assumption where the enzyme-substrate complex concentration remains constant:

v = \frac{V_{\max} [S]}{K_m + [S]}

Here, v is the reaction velocity, V_{\max} the maximum rate, [S] the substrate concentration, and K_m the Michaelis constant reflecting binding affinity; biophysical extensions incorporate diffusion-limited rates via Smoluchowski theory, yielding K_m values around 10–100 \muM for many hydrolases.03039-X)

Cellular and Systems Biophysics

Cellular biophysics examines the physical principles governing dynamic processes within individual cells and multicellular systems, integrating molecular components into functional networks for transport, signaling, and coordination. These processes rely on non-equilibrium dynamics, where energy dissipation drives phenomena such as force generation and pattern formation, often modeled using principles from nonequilibrium thermodynamics and nonlinear dynamics. Key examples include the interplay of cytoskeletal elements in maintaining cell shape and motility, as well as collective behaviors in bacterial populations that emerge from intercellular communication. The cytoskeleton provides mechanical support and enables intracellular transport through dynamic polymerization and motor-driven motion. Actin polymerization, a process central to cell protrusion and contraction, involves the assembly of globular actin (G-actin) monomers into filamentous actin (F-actin) polymers, with rates influenced by nucleotide hydrolysis and binding proteins that nucleate or cap filaments. This polymerization generates forces up to several piconewtons per filament, propelling cellular structures like lamellipodia. Complementary to actin networks, microtubule-based transport is powered by motor proteins such as kinesin, which hydrolyzes ATP to "walk" processively along microtubules at speeds of approximately 800 nm/s, facilitating cargo delivery over micrometer scales in the crowded cellular environment. These dynamics highlight how biophysical forces scale from molecular interactions to cellular-scale organization. Signal transduction in cells frequently manifests as propagating waves, particularly in calcium signaling, where localized releases trigger regenerative propagation across the cytoplasm. Calcium waves arise from calcium-induced calcium release (CICR) mechanisms in intracellular stores like the endoplasmic reticulum, modeled as an excitable medium where diffusion and feedback amplify perturbations into traveling fronts with speeds on the order of 10–20 μm/s. Feedback loops, including positive autoregulation via ryanodine receptors, sustain these waves, enabling coordinated responses such as muscle contraction or neuronal signaling. In excitable cellular systems, membrane potential dynamics underpin electrical signaling, described by the Hodgkin-Huxley model, which captures action potential initiation through voltage-gated ion channels. The Hodgkin-Huxley equations quantify how ionic currents alter membrane potential V, simplified here for cellular contexts as:

C_m \frac{dV}{dt} = I - \bar{g}_\mathrm{Na} m^3 h (V - E_\mathrm{Na}) - \bar{g}_\mathrm{K} n^4 (V - E_\mathrm{K}) - \bar{g}_\mathrm{L} (V - E_\mathrm{L}),

where C_m is membrane capacitance, I is applied current, \bar{g} terms are maximum conductances, E are reversal potentials, and m, h, n are gating variables obeying first-order kinetics that reflect channel opening probabilities. This framework, originally derived from squid axon data, extends to diverse cell types for modeling excitability in non-neuronal contexts like cardiac myocytes. Cell motility, exemplified by chemotaxis, involves directed migration along chemical gradients via reaction-diffusion mechanisms that couple sensing, signaling, and actuation. In bacteria like Escherichia coli, flagellar rotation biases random walks toward attractants, limited by the physical constraints of molecular sampling, where detection accuracy scales with receptor number and diffusion timescales, achieving precisions down to 1–2% concentration change over seconds. These systems form traveling bands or aggregates, as predicted by reaction-diffusion equations like the Keller-Segel model, where chemoattractant diffusion interacts with cellular flux to yield instabilities and pattern formation. At the systems level, multicellular coordination emerges from coupled oscillators and density-dependent signaling. Circadian rhythms in organisms arise from networks of coupled cellular clocks in the suprachiasmatic nucleus, where phase synchronization via intercellular signals like vasoactive intestinal peptide maintains ~24-hour periodicity, robust to perturbations through nonlinear oscillator interactions. In bacterial communities, quorum sensing enables collective decisions, such as biofilm formation or virulence, through autoinducer molecules like acyl-homoserine lactones that accumulate with density, triggering gene expression thresholds at concentrations around 10–100 nM to synchronize behaviors across populations. These examples illustrate how biophysical models of coupling reveal emergent properties, from temporal coherence to spatial organization in living systems.

Applications and Impacts

In Medicine and Biotechnology

Biophysics underpins advanced medical imaging techniques, providing the foundation for non-invasive diagnostics through the manipulation of physical properties in biological tissues. In magnetic resonance imaging (MRI), tissue contrast primarily stems from differences in the longitudinal (T1) and transverse (T2) relaxation times of water protons, which are influenced by biophysical factors such as molecular tumbling rates, hydrogen bonding, and interactions with macromolecules like proteins and lipids. These relaxation processes, governed by the quantum mechanical alignment of nuclear spins in a magnetic field, allow differentiation between tissues; for instance, fat exhibits shorter T1 times due to its higher molecular mobility compared to water in muscle. This biophysical basis enables high-resolution imaging of soft tissues, with seminal analyses highlighting how proton density and relaxation rates dictate signal intensity variations across anatomical structures.^[54]^[55] Ultrasound imaging similarly relies on biophysical principles of acoustic wave propagation, where sound waves interact with tissue interfaces through reflection, scattering, and attenuation, producing echoes that reveal internal structures. The speed of sound (approximately 1540 m/s in soft tissue) and impedance mismatches at boundaries, determined by tissue density and elasticity, generate the contrast needed for real-time visualization of organs and blood flow. Quantitative ultrasound techniques further exploit these interactions to estimate biophysical parameters like acoustic attenuation and backscatter coefficients, which correlate with tissue microstructure and pathology, such as fibrosis or tumors. These methods enhance diagnostic accuracy without ionizing radiation, leveraging the mechanical properties of tissues to achieve spatial resolutions down to millimeters.^[56]^[57] In therapeutics, biophysical modeling informs drug delivery systems, particularly liposomes and targeted nanoparticles, by optimizing their mechanical and transport properties for efficient payload release. Liposomes, spherical vesicles formed by phospholipid bilayers, exhibit tunable mechanics—such as bending rigidity and phase transition temperatures—that control encapsulation stability and triggered release under physiological conditions like pH changes or shear stress. Their biocompatibility arises from mimicking cell membranes, enabling fusion or endocytosis, while surface modifications enhance circulation half-life by reducing opsonization. Targeted nanoparticles, often polymeric or lipid-based, rely on size (typically 10-200 nm) and shape to exploit the enhanced permeability and retention effect in diseased vasculature, with biophysical surface charges influencing cellular uptake via receptor-mediated endocytosis. These designs minimize off-target effects, as demonstrated in oncology applications where ligand conjugation directs accumulation at tumor sites.^[58]^[59] Tissue engineering benefits from biophysical characterization of scaffolds, which must replicate the extracellular matrix's mechanical cues to guide cell behavior and regeneration. Scaffolds, often fabricated from polymers like collagen or poly(lactic-co-glycolic acid), require optimized porosity (70-90%) and stiffness (0.1-100 kPa) to facilitate nutrient diffusion, cell migration, and mechanotransduction signaling that promotes differentiation into specific lineages, such as osteoblasts for bone repair. Biophysical properties like viscoelasticity and degradation rate ensure gradual load transfer to regenerating tissue, preventing stress shielding that could lead to implant failure. These parameters are iteratively refined through experimental assays and simulations to match native tissue mechanics, accelerating applications in wound healing and organ repair.^[60]^[61] Optogenetics exemplifies biophysical innovation in neural therapeutics, employing light-sensitive proteins to precisely modulate neuronal activity since its inception post-2005. Channelrhodopsin-2, a microbial opsin, undergoes conformational changes upon blue light absorption, opening ion channels to depolarize neurons with millisecond precision and minimal thermal artifacts, enabling targeted control of circuits implicated in disorders like Parkinson's. This technique's biophysical foundation—light-induced photocurrents and membrane potential shifts—has transformed neuromodulation, allowing reversible excitation or inhibition without genetic alteration of non-target cells.^[62]^[63]

In Environmental and Evolutionary Biology

Biophysical principles have illuminated adaptations in photosynthetic systems, where quantum coherence enhances light-harvesting efficiency in natural environments. In photosynthetic complexes like those in green sulfur bacteria and marine algae, long-lived quantum coherences between excitons allow for robust energy transfer to reaction centers, minimizing losses from environmental noise such as thermal fluctuations. This coherence, observed at physiological temperatures, enables near-unity quantum yields by delocalizing excitations across multiple chromophores, facilitating adaptive responses to varying light intensities in ecosystems.^[64] Experimental spectroscopy has confirmed these effects persist for hundreds of femtoseconds, underscoring their role in ecological resilience for light-limited habitats.^[65] Evolutionary biomechanics employs allometric scaling to explain how body size influences locomotion and metabolic demands across species, revealing biophysical constraints on ecological niches. Kleiber's law posits that basal metabolic rate scales with body mass raised to the 3/4 power (B \propto M^{3/4}), linking geometric scaling of body mass with linear dimensions (M_b \propto L^3) to energy costs in movement. This relation arises from fractal-like vascular networks optimizing resource distribution, applying to locomotion where larger animals exhibit reduced mass-specific costs but increased absolute energy for transport, as seen in terrestrial and aquatic taxa adapting to foraging ranges. Such scaling informs evolutionary trade-offs, where deviations from 3/4 exponents in flying or swimming species reflect hydrodynamic or aerodynamic efficiencies.^[66]^[67] Biophysical mechanisms underpin environmental sensing in organisms, enabling navigation and homeostasis amid fluctuating conditions. In avian magnetoreception, the radical-pair mechanism in cryptochrome proteins within the retina converts Earth's magnetic field into chemical signals via spin-dependent recombination of radical pairs, allowing birds to detect field inclination for migratory orientation. This quantum process, sensitive to geomagnetic variations, integrates with visual cues for precise ecological navigation over thousands of kilometers. Similarly, thermoregulation involves biophysical models of heat exchange, where countercurrent vascular arrangements in endotherms minimize conductive losses, adapting to thermal gradients in habitats from polar to tropical zones.^[68]^[69] Climate change exerts biophysical pressures on ecosystems, altering molecular limits like membrane fluidity and driving evolutionary shifts in viral populations. Elevated seawater temperatures disrupt phospholipid saturation in coral holobionts, reducing membrane fluidity and impairing symbiont retention, which precipitates bleaching events as seen in post-2016 global anomalies. Lipidome analyses reveal upregulated unsaturated fatty acids as adaptive responses, yet chronic warming exceeds these thresholds, threatening reef biodiversity. In viral evolution, post-2020 biophysical fitness landscapes model spike protein mutations in SARS-CoV-2, quantifying how structural stability and binding affinity constrain adaptive paths, predicting immune escape trajectories under selective pressures like vaccination. These landscapes highlight rugged terrains where high-fitness peaks favor transmissibility, informing ecological dynamics of pathogen spread.^[70]^[71]

Current Challenges and Future Directions

Emerging Technologies

Cryo-electron tomography (cryo-ET) has emerged as a pivotal tool for visualizing macromolecular complexes in their native cellular environments, enabling in situ structural analysis at near-atomic resolution. Recent advancements, particularly post-2020, include improved sample preparation techniques such as cryo-focused ion beam milling and lift-out methods for tissues, which preserve cellular architecture while minimizing artifacts. These innovations have facilitated the mapping of dynamic processes like viral entry and organelle remodeling in intact cells, with resolutions approaching 2-4 Å for subtomogram averaging. For instance, parallel cryo-ET workflows have accelerated data acquisition, allowing tilt series collection in under 5 minutes per sample, thus broadening applications in structural cell biology.^[72]^[73]^[74] Super-resolution microscopy techniques, such as stimulated emission depletion (STED) and photoactivated localization microscopy (PALM), continue to push beyond the diffraction limit of ~200 nm, revealing nanoscale dynamics in living systems. Developments since 2020 emphasize live-cell compatibility and multicolor imaging, with STED achieving sub-20 nm resolution for tracking protein interactions in membranes. PALM variants, including DNA-PAINT, enable stochastic labeling for super-resolution over large fields of view, quantifying biomolecular distributions with single-molecule precision. These methods have been integrated with adaptive optics to correct aberrations in thick samples, enhancing their utility in biophysical studies of cytoskeletal mechanics and synaptic organization.^[75]^[76]^[77] Artificial intelligence, particularly neural networks, is transforming biophysical simulations by enabling data-driven parameterization of molecular force fields, surpassing traditional empirical approaches in accuracy and speed. Machine learning force fields (MLFFs), trained on quantum mechanical data, predict energies and forces for biomolecules with chemical accuracy, reducing simulation times from days to hours. For example, neural network architectures like graph neural networks have parameterized force fields for proteins and lipids, facilitating long-timescale simulations of folding and membrane permeation. These AI models integrate seamlessly with molecular dynamics engines, offering transferable predictions across diverse systems and accelerating drug design workflows.^[78]^[79]^[80] Quantum sensing using nitrogen-vacancy (NV) centers in diamond has advanced significantly since 2022, providing ultrasensitive detection of biomagnetic fields at the nanoscale. These defects enable magnetometry with sensitivities down to 50 pT/√Hz, allowing measurement of cellular magnetic signals from ion channels and neuronal activity without invasive probes. Hybrid approaches combining NV centers with optical readout have improved spatial resolution to ~10 nm, facilitating in vivo imaging of biomolecular dynamics. Such progress supports biophysical investigations into electromagnetic interactions in biological tissues, with applications in neuroscience and early disease detection.^[81]^[82]^[83] In synthetic biology, biophysical design principles guide the engineering of novel biomolecular systems by incorporating mechanics, thermodynamics, and kinetics into genetic circuits. Post-2020 efforts leverage these principles to create responsive synthetic receptors that sense mechanical forces or chemical gradients, enabling programmable cellular behaviors. For instance, de novo protein designs informed by biophysical constraints have produced modular tools for pathway optimization, enhancing efficiency in metabolic engineering. This integration fosters robust, scalable synthetic constructs for applications in biosensors and tissue engineering, including 2025 advances in automated DNA synthesis tools.^[84]^[85]^[86] Nanoscale robotics, exemplified by DNA origami nanostructures, has progressed toward functional molecular machines capable of autonomous operation. Advances since 2020 include fuel-driven walkers and rotors that achieve directed motion at speeds up to 10 nm/s, powered by chemical gradients or light. DNA origami scaffolds enable precise assembly of enzymatic cascades into robotic assemblies, mimicking cellular transport mechanisms. These machines demonstrate cargo delivery and self-replication at the single-molecule level, paving the way for therapeutic nanodevices.^[87]^[88]^[89]

Open Questions in Biophysical Research

One prominent open question in neural biophysics concerns the integration of microscopic ion dynamics with macroscopic network theories to explain consciousness. Circuit-level theories, such as apical amplification and dendritic integration theory, propose that consciousness arises from specific neural circuit interactions, yet linking these to underlying ion channel behaviors remains challenging due to the complexity of multiscale processes.^[90] An integrative multiscale framework highlights gaps in relating conscious experience to brain processes, including how ion fluxes influence network stability and global brain states.^[91] Recent studies emphasize the role of unmodeled biological details, like ion channel variability, in bridging cellular electrophysiology with emergent network phenomena, underscoring the need for models that capture this hierarchy without oversimplification.^[92] The biophysical conditions enabling self-replicating systems at the origin of life represent another unresolved frontier. Early protein folding processes may have driven the emergence of functional sequences from prebiotic molecules, but the precise environmental conditions—such as pH, temperature gradients, and molecular crowding—that stabilized these systems remain debated.^[93] Recent experiments demonstrate biochemistry-free self-reproduction in polymeric vesicles, suggesting that non-equilibrium thermodynamics could facilitate replication without enzymatic catalysis, yet scaling this to protocell complexity under plausible primordial settings is uncertain.^[94] These findings point to a core challenge: reconciling the rarity of functional biopolymers with the vast chemical space of early Earth, where self-replication likely required coupled physical and chemical drivers. Multiscale modeling in biophysics faces significant hurdles in bridging quantum-level interactions to macroscopic behaviors while preserving accuracy. The curse of dimensionality in reaction-diffusion systems, where reaction terms explode with molecular complexity, limits simulations of subcellular processes across spatial and temporal scales. Quantum biology principles highlight the need for frameworks that incorporate coherent effects in biomolecules like DNA without losing fidelity at cellular levels, as current methods often introduce approximations that propagate errors upward. Advances in computational protocols for solvated systems reveal the high effort required for transferable multiscale predictions, emphasizing gaps in handling solvent dynamics and quantum corrections in biological contexts.^[95] Debates in active matter theory center on its application to non-equilibrium organization in cellular systems. Active matter models describe self-organization in cytoskeletal networks and actomyosin dynamics, but controversies persist regarding how local energy inputs drive global patterns like oscillations during morphogenesis without external tuning. Surveys of active matter literature identify open questions on the universality of phase transitions in dense cellular environments, where hydrodynamic interactions and density fluctuations challenge existing theories of collective behavior.^[96] Computational tools for cellular biophysics underscore unresolved issues in solving active matter equations at realistic scales, particularly for predicting emergent structures in living tissues.^[97] Post-2023 inquiries into the biophysical limits of CRISPR efficiency question the molecular constraints on editing precision and throughput. Delivery barriers, such as endosomal escape and nuclear localization, cap in vivo efficiency below 50% in many targets, with off-target effects arising from Cas9-DNA dwell times and mismatch tolerances.^[98] Recent assessments highlight immunogenicity and vector constraints as key biophysical bottlenecks, limiting scalability for therapeutic applications despite advances in base editing.^[99] Areas of incompleteness in biophysical research include the understudy of non-model organisms and the integration of epigenetics with mechanical forces. Nontraditional species offer insights into diverse biophysical adaptations, yet research gaps persist due to challenges in genomic tools and imaging, leaving evolutionary variations in cellular mechanics underexplored.^[100] Overlooked biodiversity in biomimetic contexts reveals untapped potential for understanding force generation in non-model systems, where biophysical principles may differ from lab standards.^[101] Integrating epigenetics with mechanics involves unresolved questions on how chromatin modifications influence nuclear lamina interactions and heterochromatin domain formation, with polymer models predicting nanoscale effects but lacking experimental validation across cell types.^[102] Quantitative extraction of chromatin-lamina binding strengths highlights biophysical parameters that couple epigenetic states to mechanical stability, yet dynamic feedback loops remain poorly characterized.^[103] Emerging technologies like advanced imaging may address these gaps in the coming years, alongside 2025 progress in high-throughput biophysical measurements for RNA structures in non-model systems.^[104]

References

[1]
Biophysics - NCBI - NIH
Jan 2, 2004 · The discovery and application of physical principles, methods and theories relevant to the study of living organisms and life processes.
[2]
Biophysics - whence, whither, wherefore - or Hold that hyphen - PMC
Mar 2, 2011 · The term biophysics probably made its first appearance in Germany in the mid-19th century in the writings of a group of remarkable polymaths, ...
[3]
U-M Biophysics History - College of LSA
Biophysics at U-M started in Physics in the 1930s, with a 1949 Ph.D. program, a 1960 Biophysics Research Division, and became LSA Biophysics in 2007.
[4]
History - Biophysics | Johns Hopkins University
Johns Hopkins first offered biophysics in 1949, the department was established in 1957, and "fundamental studies" were formally established in 1956.
[5]
Research Areas | PhD Degree Program in Biophysics (BP)
1. Biophysical approaches to cell biology · 2. Complex biological systems · 3. Computational and theoretical biophysics · 4. Membrane biophysics · 5. Protein ...
[6]
[PDF] Biophysics revealed the structure of DNA
Biophysics gives us medical imaging technologies including MRI, CAT scans, PET scans, and sonograms for diagnos- ing diseases. It provides the life-saving ...
[7]
Applications of biophysical techniques in drug discovery and ... - NIH
The use of various biophysical techniques is discussed, including thorough assay development, primary screening, hit confirmation, and mechanistic ...
[8]
Q&A: What is biophysics? - PMC - PubMed Central
Mar 2, 2011 · Biophysics is the study of biological systems and biological processes using physics-based methods or based on physical principles.
[9]
What is Biophysics? - College of LSA
Biophysics applies physics, chemistry, math, and modeling to biological systems to understand their structure, dynamics, and function, using an ...
[10]
Physics of living systems - Nature
Jul 4, 2018 · From the dynamics of molecular motors converting electrochemical energy into mechanical forces to the large-scale coordination of ant ...
[11]
Protein Folding Thermodynamics and Dynamics: Where Physics ...
The role of theory in protein folding is to provide insights into thermodynamic, kinetic, and evolutionary mechanisms that are not directly available from ...
[12]
Biophysical Principles of Ion-Channel-Mediated Mechanosensory ...
Oct 1, 2019 · In this review, we revisit the biophysical principles that underlie the innate force-sensing ability of mechanosensitive channels.
[13]
DNA mechanics and its biological impact - PubMed - NIH
Mar 19, 2021 · DNA mechanical deformations are involved in interactions and manipulation. Variations in DNA's mechanical properties regulate genome-wide ...
[14]
Luigi Galvani - Magnet Academy - National MagLab
Luigi Galvani was a pioneer in the field of electrophysiology, the branch of science concerned with electrical phenomena in the body.
[15]
Introduction and Overview | Physics of Life
As will become clear, the intellectual agenda of biological physics is extremely broad, touching phenomena on scales ranging from molecules to ecosystems.
[16]
The Mid-Century Biophysics Bubble: Hiroshima and the Biological ...
Aug 6, 2025 · As contemporary literature repeatedly pointed out, the emergence of the field was heavily influenced by the interest in the biological ...
[17]
None
### Summary of Interdisciplinary Nature and Examples of Physical Models in Biological Problems
[18]
The Quantum Mechanics of Photosynthesis - AZoQuantum
Jan 28, 2022 · Quantum superposition offers a valid explanation as to why photosynthesis is highly efficient at converting sunlight into energy. Experimental ...
[19]
The biophysics and mechanics of blood from a materials perspective
We highlight how blood vessels provide a mechanosensitive barrier between blood and tissues and how changes in vessel stiffness and flow shear stress can be ...
[20]
What Is Biophysics? | The Biophysical Society
The structure of DNA was solved in 1953 using biophysics, and this discovery was critical to showing how DNA is like a blueprint for life. Now we can read ...
[21]
Biophysicists- The best of both worlds - Biophysical Society
... Biophysicists are scientists who talk about physics amongst biologists, who talk about biology amongst physicists, and who talk about the weather amongst ...
[22]
Perspectives of the Directors of the Molecular Biophysics Training ...
Another major challenge for biophysics training programs is in creating and sustaining interest and appreciation for both the biology and the physics ends of ...
[23]
[PDF] Growth and remodelling of living tissues: perspectives, challenges ...
Galileo Galilei (1564–1642) was interested in the strength of bones, particularly in the optimal strength-to-weight relation in animals of different sizes ...
[24]
Philosophy of Cell Biology
Oct 15, 2019 · But the cell did not become a focal unit for studying biological processes until Schleiden (1838) and Schwann (1839) advanced the cell theory ...<|separator|>
[25]
Hermann von Helmholtz - Stanford Encyclopedia of Philosophy
Feb 18, 2008 · Hermann von Helmholtz (1821–1894) participated in two of the most significant developments in physics and in the philosophy of science in the 19th century.Theory of Perception · Conservation laws... · Epistemology · Bibliography
[26]
How is information transmitted in a nerve? - PMC - NIH
In 1850, Hermann von Helmholtz designed an experiment to measure the velocity of the signal that propagates along the sciatic nerve of a frog [1–3].Missing: 1870s | Show results with:1870s
[27]
[PDF] Theory of action potentials | Romain Brette
Jun 9, 2016 · In 1939, Bernstein's membrane theory was tested and challenged by several studies in the squid giant axon. Cole and Curtis (1939) designed a ...
[28]
(PDF) Mechanism, vitalism and organicism in late nineteenth and ...
Aug 9, 2025 · In the early twentieth century philosophical Mechanism became the foundation of a 'new biology' that sought to establish the life sciences on the same solid ...Missing: biophysics | Show results with:biophysics
[29]
[PDF] THE SVEDBERG - The ultracentrifuge - Nobel Lecture, May 19, 1927
ULTRACENTRIFUGE. 83. Table 3 gives the molecular weights of the proteins hitherto studied by the centrifugation method. The values obtained by sedimentation ...Missing: Theodor 1920s 1930s
[30]
Schrödinger's What Is Life? at 75 - ScienceDirect.com
Jun 16, 2021 · By focusing on the nature of the hereditary molecule now known to be DNA, Schrödinger foreshadowed the agenda for the DNA-centric perspective ...
[31]
What Rosalind Franklin truly contributed to the discovery of DNA's ...
Apr 25, 2023 · In the early 1950s, the structure and function of DNA remained unclear. ... Black and white X-ray diffraction photograph of DNA from 1952.
[32]
Francis Crick, Rosalind Franklin, James Watson, and Maurice Wilkins
Sep 8, 2025 · After obtaining the Signer DNA in 1950, Wilkins collaborated closely with Gosling on X-ray diffraction studies. Together they were able to ...
[33]
The Society's History
The early efforts of these individuals culminated in the “First National Biophysics Conference”, held in Columbus, Ohio on March 4–6, 1957. The meeting was ...
[34]
Reliability and accuracy of single-molecule FRET studies for ...
Mar 27, 2023 · Our work demonstrates the ability of smFRET experiments to simultaneously measure distances and avoid the averaging of conformational dynamics ...
[35]
Biological physics by high-speed atomic force microscopy - Journals
Oct 26, 2020 · High-speed atomic force microscopy (HS-AFM) provides nanometre structural information and dynamics with subsecond resolution of biological systems.
[36]
Optical tweezers in single-molecule biophysics - Nature
Mar 25, 2021 · Optical tweezers are a method to exert forces or torques on individual molecules and/or to directly measure the forces or torques generated in ...
[37]
Cryo-electron microscopy wins chemistry Nobel - Nature
Oct 12, 2017 · Jacques Dubochet, Joachim Frank and Richard Henderson were awarded the prize on 4 October for their work in developing cryo-electron microscopy (cryo-EM).Missing: biophysics | Show results with:biophysics
[38]
CHARMM additive and polarizable force fields for biophysics and ...
The present paper offers a review of recent developments in the CHARMM additive force field, one of the most popular bimolecular force fields.
[39]
Current Status of Protein Force Fields for Molecular Dynamics - NIH
The current status of classical force fields for proteins is reviewed. These include additive force fields as well as the latest developments in the Drude and ...
[40]
Brownian Dynamics Simulations of Biological Molecules - PMC - NIH
Aug 28, 2019 · The starting point for Brownian dynamics (BD) is the Langevin equation, which is Newton's law of motion with several terms. There is the ...
[41]
Many-particle Brownian and Langevin Dynamics Simulations with ...
Apr 13, 2011 · Brownian Dynamics (BD) is a coarse-grained implicit-solvent simulation method that is routinely used to investigate binary protein association ...
[42]
Methods for Monte Carlo simulations of biomacromolecules - PMC
We provide an overview of the state-of-the-art MC methods designed for efficient sampling of biomacromolecules using implicit solvent models.
[43]
Sampling of the conformational landscape of small proteins ... - Nature
Oct 23, 2020 · We report the development of an all-atom Monte Carlo approach that permits the modelling of the large-scale conformational change of proteins.
[44]
Hybrid Quantum Mechanical/Molecular Mechanical Methods For ...
May 9, 2023 · Hybrid quantum mechanical/molecular mechanical (QM/MM) methods have become indispensable tools for the study of biomolecules.
[45]
Multiscale Methods for Macromolecular Simulations - PMC
In this article we review the key modelling tools available for simulating biomolecular systems. We consider recent developments and representative applications ...Missing: biophysics | Show results with:biophysics
[46]
Highly accurate protein structure prediction with AlphaFold - Nature
Jul 15, 2021 · AlphaFold greatly improves the accuracy of structure prediction by incorporating novel neural network architectures and training procedures ...
[47]
Ionic effects on the elasticity of single DNA molecules - PNAS
(iii) The elastic stretch modulus and persistence length display opposite trends with ionic strength—a direct contradiction of macroscopic elasticity theory. ( ...
[48]
DNA supercoiling: A regulatory signal for the λ repressor - PNAS
Oct 15, 2014 · Supercoiling is an indicator of cell health, it modifies the accessibility of chromatin, and coordinates the transcription of genes.
[49]
Structural diversity of supercoiled DNA | Nature Communications
Oct 12, 2015 · Using a combination of approaches we here show that supercoiling causes DNA to adopt large conformational variability. Unpaired bases and ...Missing: key | Show results with:key
[50]
https://www.nature.com/articles/s41586-024-07487-w
[51]
The biophysical basis of tissue contrast in extracranial MR imaging
The biophysical basis of proton-MR tissue contrast is reviewed. Differences in the molecular sizes of water, fat, and protein macromolecules affect the rate of ...
[52]
Ultrasound–biophysics mechanisms - ScienceDirect.com
Ultrasonic biophysics is the study of mechanisms responsible for how ultrasound and biological materials interact. Ultrasound-induced bioeffect or risk ...
[53]
Quantitative ultrasound imaging of soft biological tissues
Sep 9, 2021 · QUS techniques extract fundamental physical properties of tissues based on interactions between ultrasound waves and tissue microstructure.
[54]
Targeted liposomal drug delivery: a nanoscience and biophysical ...
This review article summarizes development of liposomal targeted drug delivery systems, with an emphasis on the biophysical properties of lipids.
[55]
Physical and Biophysical Characteristics of Nanoparticles: Potential ...
In this chapter, we discuss the role of various physical and biophysical characteristics of NPs that have implications in designing targeted drug delivery ...
[56]
Scaffolding in tissue engineering: general approaches and ... - NIH
This paper aims to review the functions of scaffolds and the major scaffolding approaches as important guidelines for selecting scaffolds.
[57]
Design Challenges in Polymeric Scaffolds for Tissue Engineering
This article provides a critical appraisal of how key biomaterial scaffold parameters, such as structure architecture, biochemistry, mechanical behavior, and ...Introduction · Scaffold Main Characteristics · Recent Progress in Scaffolds...
[58]
Millisecond-timescale, genetically targeted optical control of neural ...
Aug 14, 2005 · We demonstrate reliable, millisecond-timescale control of neuronal spiking, as well as control of excitatory and inhibitory synaptic transmission.
[59]
Optogenetic control of neural activity: The biophysics of microbial ...
Oct 13, 2023 · Optogenetics, the use of microbial rhodopsins to make the electrical activity of targeted neurons controllable by light, has swept through neuroscience.Optogenetic Control Of... · Opsin Classification And... · Photocurrent Magnitude And...
[60]
Methodology to Investigate Effect of Prosthetic Interface Design on ...
Jan 17, 2024 · To advance our understanding of prosthetic interface fit, tools are needed to evaluate the mechanical interaction at the prosthetic interface, ...
[61]
Biomechanical Stress Analysis of Platform Switch Implants of ... - NIH
Feb 24, 2022 · The purpose of this study was to evaluate and compare the strain developed in D2 and D3 types of bones on vertical loading by platform switch implants of ...Missing: biophysics | Show results with:biophysics
[62]
Quantum coherence spectroscopy reveals complex dynamics in ...
In this work, we provide experimental evidence of long-lived quantum coherence between the spectrally separated B800 and B850 rings of the light-harvesting ...
[63]
How Quantum Coherence Assists Photosynthetic Light Harvesting
Jan 26, 2012 · Quantum coherence enables rapid excitation transfer, modifying energy levels and combining transition dipole moments, increasing light ...
[64]
Kleiber's Law: How the Fire of Life ignited debate, fueled theory, and ...
The work of Max Kleiber (1893–1976) and others revealed that animal respiration rates apparently scale more closely as the 3/4 power of body size.
[65]
Allometric scaling of metabolic rate from molecules and ... - PNAS
A single three-quarter power allometric scaling law characterizes the basal metabolic rates of isolated mammalian cells, mitochondria, and molecules of the ...Missing: locomotion | Show results with:locomotion
[66]
Chemical magnetoreception in birds: The radical pair mechanism
Here, we present a physical chemist's perspective on the “radical pair mechanism” of compass magnetoreception in birds.
[67]
Biophysical models unravel associations between glucocorticoids ...
Oct 12, 2021 · Here we used biophysical models to calculate thermoregulatory costs (i.e. the amount of heat required to keep body temperature in homeostasis) ...
[68]
Lipidome analysis of Symbiodiniaceae reveals possible ...
Oct 16, 2019 · Our study provides novel insights into the heat tolerance of coral symbionts, contributing to the understanding of the potential of coral reef ecosystems.<|separator|>
[69]
The biophysical landscape of viral evolution - PNAS
Jun 24, 2024 · They develop a biophysical model that can predict the fitness of a mutant in the viral spike protein. The model describes the interaction ...Missing: post- | Show results with:post-
[70]
The big chill: Growth of in situ structural biology with cryo-electron ...
Dec 13, 2024 · In situ structural biology with cryo-electron tomography (cryo-ET) and subtomogram averaging (StA) is evolving as a major method to understand the structure, ...
[71]
Recent technical advances in cellular cryo-electron tomography
This review presents the fundamental principles and methodologies of cellular cryo-ET, highlighting recent developments in sample preparation, data collection, ...
[72]
Innovations in cryo-electron tomography for tissues - PubMed
Jul 7, 2025 · Advances in sample vitrification, cryo-focused ion beam (cryo-FIB) milling, and lift-out techniques have substantially improved tissue ...
[73]
Technological advances in super-resolution microscopy to study ...
Jan 20, 2022 · Here, we review the technical details behind the most common implementations of super-resolution microscopy and highlight some of the recent, promising ...
[74]
Resolution in super-resolution microscopy – facts, artifacts ...
May 27, 2025 · This paper compiles expert opinions on crucial, yet often overlooked, aspects of SRM that are essential for maximizing its benefits and advancing the field.
[75]
Surpassing the Diffraction Limit in Label-Free Optical Microscopy
Label-free super-resolution microscopy is evolving to offer detailed and dynamic imaging of living cells, surpassing the capabilities of conventional methods.
[76]
Fine-tuning molecular mechanics force fields to experimental free ...
Jan 8, 2025 · The prospect of improved accuracy through data-driven approaches has driven the development of neural MM force field parameterization approaches ...<|control11|><|separator|>
[77]
Quantum-based machine learning and AI models to generate force ...
Oct 10, 2022 · The AI-generated force field was effective in the fast and accurate generation of partial charges and other force field parameters for small ...
[78]
Molecular Simulations with a Pretrained Neural Network and ...
Aug 31, 2025 · Machine Learning Force Fields (MLFFs) promise to enable general molecular simulations that can simultaneously achieve efficiency, accuracy, ...Missing: biophysics parameterization
[79]
Hybrid quantum sensing in diamond - Frontiers
Feb 13, 2024 · This section reviews recent advances in hybrid sensing using NV centers in diamond, for measurement of temperatures, pressure, and bio- ...
[80]
Recent progress in hybrid diamond photonics for quantum ... - Nature
May 8, 2025 · An ensemble of NV centers is powerful to enhance the sensitivity of quantum sensing. Ensembles of NV centers in diamond can be produced through ...
[81]
Emerging Diamond Quantum Sensing in Bio-Membranes - PMC
The recent emerging diamonds hosting quantum defects (ie, nitrogen-vacancy (NV) center) demonstrate intriguing optical and spin properties.
[82]
The evolution of synthetic receptor systems - PMC - PubMed Central
Altogether, these explorations identify biophysical design principles which guide ... Synthetic Biology, doi: 10.1093/synbio/ysaa017 (2020). This study ...
[83]
De novo designed protein toolkit rewriting the rules of synthetic biology
Sep 13, 2025 · AI-driven de novo protein engineering is enhancing synthetic biology by enabling atom‑level design of customizable proteins beyond natural ...
[84]
Recent Advances in DNA Origami-Engineered Nanomaterials and ...
Mar 29, 2023 · This review focuses on the recent progress in DNA origami-engineered nanomaterials in the past five years, outlining the exciting achievements as well as the ...
[85]
Control and synchronization of rapid nanoscale DNA heat engine by ...
Jul 30, 2025 · Using a more rigid arm like 10HB or 16HB origami (22) can further enhance the performance of DNA hinge machines. We have also studied ...
[86]
Applications of DNA origami in biomedicine: advances, challenges ...
Oct 1, 2025 · The method, which is known as DNA origami, has emerged over the past few decades as a promising strategy for the fabrication of nanoscale ...
[87]
Origins of life: The Protein Folding Problem all over again? - PNAS
Aug 12, 2024 · We give a perspective that proteins and their folding processes are likely to have been the primary driver of the early stages of the origin of life.
[88]
Self-reproduction as an autonomous process of growth and ... - PNAS
May 27, 2025 · This study introduces a biochemistry-free method for creating self-reproducing polymeric vesicles. In this process, nonamphiphilic molecules are mixed and ...Missing: biophysical | Show results with:biophysical
[89]
Metareview: a survey of active matter reviews
A metareview article that surveys the existing review articles and books on active matter. Thereby, this article provides a useful starting point for finding ...
[90]
[PDF] Computational tools for cellular scale biophysics - Flatiron Institute
Jun 7, 2024 · This review comes from a themed issue on Cell Architecture (2024) ... [51,90]) should enable the high-fidelity solution of active matter problems ...
[91]
Nontraditional models as research tools: The road not taken - PMC
Oct 1, 2025 · Animal modeling in biosciences. Biomedical research is dominated by studies involving limited species only, that are typically recognized as the ...
[92]
Overlooked sources of inspiration in biomimetic research - Nature
Jul 15, 2025 · Biomimetics draws inspiration from biological organisms, yet only a small fraction of Earth's biodiversity has been explored for innovation.
[93]
Polymer model integrates imaging and sequencing to reveal how ...
Apr 23, 2025 · Our model predicts the formation of nanoscale heterochromatin domains and quantifies how domain size scales with epigenetic reaction rates.
[94]
Revealing the biophysics of lamina-associated domain formation by ...
Aug 25, 2025 · This approach allows us to quantitatively extract key biophysical parameters, such as chromatin-lamina interaction strengths and histone ...