Biophysics

Biophysics (also biological physics) is an interdisciplinary science that applies the theories and methods of physics to questions of biology.

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Scope

Biophysics research today is comprised of several specific biological studies which neither share a unique identifying factor nor subject themselves to clear and concise definitions. The studies included under the umbrella of biophysics range from sequence analysis to neural networks. Biophysics is also concerned with creating mechanical limbs and nanomachines to regulate biological functions, although currently these are more commonly referred to as belonging to the fields of bioengineering and nanotechnology respectively.

Biophysics typically addresses biological questions that are similar to those in biochemistry, but the questions are asked at a molecular level. Traditional studies in biochemistry and molecular biology are conducted using statistical ensemble experiments, typically using pico- to micro-molar concentrations of macromolecules. Because the molecules that comprise living cells are so small, techniques such as PCR amplification, gel blotting, fluorescence labeling and in vivo staining are used so that experimental results are observable with an unaided eye or, at most, optical magnification. Using these techniques, researchers in these subjects attempt to elucidate the complex systems of interactions that give rise to the processes that make life possible. By drawing knowledge and experimental techniques from a wide variety of disciplines, biophysicists are able to indirectly observe or model the structures and interactions of individual molecules or complexes of molecules.

In addition to things like deciphering a protein structure or measuring the kinetics of interactions, biophysics is also understood to encompass research areas that apply models and experimental techniques derived from physics (e.g. electromagnetism and quantum mechanics) to larger systems such as tissues or organs (hence the inclusion of basic neuroscience as well as more applied techniques such as fMRI).

Focus as a subfield

Biophysics often does not have university-level departments of its own, but have presence as groups across departments within the fields of 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 mixing between departments.

• 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 - angstrom-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.

Many biophysical techniques are unique to this field. Many of the research traditions in biophysics were initiated by scientists who were straight physicists, chemists, and biologists by training.

Topics in biophysics and related fields

• Animal locomotion
• Cellular biophysics
• Molecular biophysics
• Channels, receptors and transporters
• Electrophysiology
• Cell membranes
• Bioenergetics
• Gravitational biology
• Molecular motors
• Muscle and contractility
• Nucleic acids
• Photobiophysics and biophotonics
• Proteins
• Radiobiology
• Signaling
• Supramolecular assemblies
• Spectroscopy, imaging, etc.
• Systems neuroscience
• Neural encoding
• Bionics
• Polysulphur membranes
• Biosensor and Bioelectronics

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
• Hermann J. Muller, discovered that X-rays cause mutations
• Linus Pauling & Robert Corey, co-discoverers of the alpha helix and beta sheet structures in proteins
• Fritz-Albert Popp, pioneer of biophotons work
• 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 genetic code
• Max Perutz & John Kendrew, pioneers of protein crystallography
• Allan Cormack & Godfrey Hounsfield, development of computer assisted tomography
• Paul Lauterbur & Peter Mansfield, development of 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
• Friedrich Dessauer, research on radiation, especially X-rays
• Julio Fernandez
• 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
• Benoit Roux
• Mikhail Volkenshtein, Revaz Dogonadze & Zurab Urushadze, authors of the 1st Quantum-Mechanical (Physical) Model of Enzyme Catalysis, supported a theory that enzyme catalysis use quantum-mechanical effects such as tunneling.
• John P. Wikswo, research on biomagnetism
• 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

References

• Perutz M.F. Proteins and Nucleic Acids, Elsevier, Amsterdam, 1962
• Perutz MF (1969). "The haemoglobin molecule". Proceedings of the Royal Society of London. Series B 173 (31): 113-40. PMID 4389425
• Dogonadze R.R. and Urushadze Z.D. Semi-Classical Method of Calculation of Rates of Chemical Reactions Proceeding in Polar Liquids.- J.Electroanal.Chem., 32, 1971, pp. 235-245
• Volkenshtein M.V., Dogonadze R.R., Madumarov A.K., Urushadze Z.D. and Kharkats Yu.I. Theory of Enzyme Catalysis.- Molekuliarnaya Biologia (Moscow), 6, 1972, pp. 431-439 (In Russian, English summary)
• Rodney M. J. Cotterill (2002). Biophysics : An Introduction. Wiley. ISBN 978-0471485384. 
• Sneppen K. and Zocchi G., Physics in Molecular Biology, Cambridge University Press, 2005. ISBN 0-521-84419-3
• Glaser R., Biophysics, Springer, 2001, ISBN 3-540-67088-2

See also

• Important publications in biophysics (biology)
• important publications in biophysics (physics)

• Biophysical Society