Biophysics (also biological physics or biophysical chemistry) is an interdisciplinary science that employs and develops theories and methods of the physical sciences for the investigation of biological systems . Studies included under the branches of biophysics span all levels of biological organization, from the molecular scale to whole organisms and ecosystems. Biophysical research shares significant overlap with biochemistry, nanotechnology, bioengineering, agrophysics and systems biology.

Molecular biophysics typically addresses biological questions that are similar to those in biochemistry and molecular biology, but the questions are approached quantitatively. Scientists in this field conduct research concerned with understanding the interactions between the various systems of a cell, including the interactions between DNA, RNA and protein biosynthesis, as well as how these interactions are regulated. A great variety of techniques are used to answer these questions.
Fluorescent imaging techniques, as well as electron microscopy, x-ray crystallography, NMR spectroscopy and atomic force microscopy (AFM) are often used to visualize structures of biological significance. Conformational change in structure can be measured using techniques such as dual polarisation interferometry and circular dichroism. Direct manipulation of molecules using optical tweezers or AFM can also be used to monitor biological events where forces and distances are at the nanoscale. Molecular biophysicists often consider complex biological events as systems of interacting units which can be understood through statistical mechanics, thermodynamics and chemical kinetics. By drawing knowledge and experimental techniques from a wide variety of disciplines, biophysicists are often able to directly observe, model or even manipulate the structures and interactions of individual molecules or complexes of molecules.

In addition to traditional (i.e. molecular and cellular) biophysical topics like structural biology or enzyme kinetics, modern biophysics encompasses an extraordinarily broad range of research. It is becoming increasingly common for biophysicists to apply the models and experimental techniques derived from physics, as well as mathematics and statistics, to larger systems such as tissues, organs, populations and ecosystems.

Focus as a subfield

Biophysics often does not have university-level departments of its own, but has presence as groups across departments within the fields of molecular biology, biochemistry, chemistry, computer science, mathematics, medicine, pharmacology, physiology, physics, and neuroscience. What follows is a list of examples of how each department applies its efforts toward the study of biophysics. This list is hardly all inclusive. Nor does each subject of study belong exclusively to any particular department. Each academic institution makes its own rules and there is much overlap between departments.

• Quantum Biophysics involves quantum information processing of coherent states, entanglement between coherent protons and transcriptase components and replication of decohered isomers to yield time-dependent base substitutions. These studies imply applicatons in quantum computing.

• Biology and molecular biology - Almost all forms of biophysics efforts are included in some biology department somewhere. To include some: gene regulation, single protein dynamics, bioenergetics, patch clamping, biomechanics.

• Structural biology - Ångstrom-resolution structures of proteins, nucleic acids, lipids, carbohydrates, and complexes thereof.

• Biochemistry and chemistry - biomolecular structure, siRNA, nucleic acid structure, structure-activity relationships.

• Computer science - Neural networks, biomolecular and drug databases.

• Computational chemistry - molecular dynamics simulation, molecular docking, quantum chemistry

• Bioinformatics - sequence alignment, structural alignment, protein structure prediction

• Mathematics - graph/network theory, population modeling, dynamical systems, phylogenetics.

• Medicine and neuroscience - tackling neural networks experimentally (brain slicing) as well as theoretically (computer models), membrane permitivity, gene therapy, understanding tumors.

• Pharmacology and physiology - channel biology, biomolecular interactions, cellular membranes, polyketides.

• Physics - biomolecular free energy, stochastic processes, covering dynamics.

• Agronomy Agriculture

Many biophysical techniques are unique to this field. Research efforts in biophysics are often initiated by scientists who were traditional physicists, chemists, and biologists by training.

Topics in biophysics and related fields

Famous biophysicists

• Luigi Galvani, discoverer of bioelectricity

• Hermann von Helmholtz, first to measure the velocity of nerve impulses; studied hearing and vision

• Alan Hodgkin & Andrew Huxley, mathematical theory of how ion fluxes produce nerve impulses

• Georg von Békésy, research on the human ear

• Bernard Katz, discovered how synapses work

• G. N. Ramachandran Computation of relative stability of Protein Structure, famous for Ramachandran plot.

• Hermann J. Muller, discovered that X-rays cause mutations

• George Palade Nobel Laureate in physiology or medicine for protein secretion and cell ultra-structure from electron microscopy studies

• Linus Pauling & Robert Corey, co-discoverers of the alpha helix and beta sheet structures in proteins

• J. D. Bernal, X-ray crystallography of plant viruses and proteins

• Rosalind Franklin, Maurice Wilkins, James D. Watson and Francis Crick, pioneers of DNA crystallography and co-discoverers of the structure of DNA. Francis Crick later participated in the Crick, Brenner et al. experiment which established the basis for understanding the genetic code

• Max Perutz & John Kendrew, pioneers of protein crystallography

• Sir John Randall, X-ray and neutron diffraction of proteins and DNA

• Ronald Burge, X-ray diffraction of nerve myelin, bacterial cell walls and membranes

• Allan Cormack & Godfrey Hounsfield, development of computer assisted tomography

• Kurt Wüthrich Nobel Laureate in physiology or medicine for 2D-FT NMR of protein structure in solution

• Paul Lauterbur & Peter Mansfield, development of magnetic resonance imaging

• Stephen D. Levene, DNA-protein Interactions, DNA looping, and DNA topology.

• Seiji Ogawa, development of functional magnetic resonance imaging

Other notable biophysicists

• Adolf Eugen Fick, responsible for Fick's law of diffusion and a method to determine cardiac output.

• Howard Berg, characterized properties of bacterial chemotaxis

• Steven Block, observed the motions of enzymes such as kinesin and RNA polymerase with optical tweezers

• Carlos Bustamante, known for single-molecule biophysics of molecular motors and biological polymer physics

• Steven Chu, Nobel laureate who helped develop optical trapping techniques used by many biophysicists

• Christoph Cremer, overcoming the conventional limit of resolution that applies to light based investigations (the Abbe limit) by a range of different methods

• Friedrich Dessauer, research on radiation, especially X-rays

• Julio Fernandez

• Govindjee, professor emeritus at the University of Illinois, research in photosynthesis and photosynthetic mechanisms by fluorescence and NMR methods

• Enrico Gratton research on frequency domain spectroscopy and correlation spectroscopy on biological and biomedical systems

• Stefan Hell, developed the principle of STED microscopy

• Richard Henderson, scientist at the MRC Laboratory of Molecular Biology, developed the use of cryo-EM to study membrane protein structures.

• John J. Hopfield, worked on error correction in transcription and translation (kinetic proof-reading), and associative memory models (Hopfield net)

• Martin Karplus, research on molecular dynamical simulations of biological macromolecules.

• Franklin Offner, professor emeritus at Northwestern University of professor of biophysics, biomedical engineering and electronics who developed a modern prototype of the electroencephalograph and electrocardiograph called the dynograph.

• Nicolas Rashevsky,, former Editor of the first journal of mathematical and theoretical biophysics entitled " The Bulletin of Mathematical Biophysics " (1940—1973) and author of the two-factor model of neuronal excitation, biotopology and organismic set theory.

• Arieh Warshel, the development of QM/MM approaches, paving the way for a quantitative understanding of enzymatic reactions, and allowing for the first consistent modeling of the catalytic effect of an enzyme; the introduction of MD simulations in biology; the introduction of consistent electrostatic calculations in proteins.

• Robert Rosen, theoretical biophysicist and mathematical biologist, author of: metabolic-replication systems, categories of metabolic and genetic networks, quantum genetics in terms of von Neumann's approach, non-reductionist complexity theories, dynamical and anticipatory systems in biology.

• Benoit Roux

• Mikhail Volkenshtein, Revaz Dogonadze & Zurab Urushadze, authors of the first quantum-mechanical model of enzyme catalysis, supported a theory that enzyme catalysis use quantum-mechanical effects such as tunneling.

• John Wikswo, research on biomagnetism and cardiac electrophysiology

• Douglas Warrick, specializing in bird flight (hummingbirds and pigeons)

• Ernest C. Pollard — founder of the Biophysical Society

• Marvin Makinen, pioneer of the structural basis of enzyme action

• Gopalasamudram Narayana Iyer Ramachandran, developer of the Ramachandran plot and pioneer of the collagen triple-helix structure prediction

• Doug Barrick, repeat protein folding

• Naomi Courtemanche, kinetics of leucine rich repeat protein folding

• Ellen Kloss, salt-dependence of leucine rich repeat protein folding

• Bertrand Garcia Moreno E., Dielectric Constant of Globular Protein 'hydrophobic' core

• Ludwig Brand, Time resolved fluorescence anisotropy decay in Biological systems

• Eduardo Ducla Soares, founder of IBEB (Institute of Biophysics and Biomedical Engineering)

See also

• Important publications in biophysics

• Important publications in biophysics