Molecules

 1.     The molecules of living matter have a complexity not found in inanimate nature. New methods for dealing with them lead to a third kind of biophysics which seeks, in combination with biochemistry, to understand properties of organic inatter in terms of the atomic make-up, the reactions, and the arrangements of these giant molecules. Fluorescent imaging techniques, as well as electron microscopy, x-ray crystallography, NMR spectroscopy, atomic force microscopy (AFM) and small-angle scattering (SAS) both with X-rays and neutrons (SAXS/SANS) are often used to visualize structures of biological significance. Protein dynamics can be observed by neutron spin echo spectroscopy. Conformational change in structure can be measured using techniques such as dual polarization interferometry, circular dichroism, SAXS and SANS. 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 entities which can be understood e.g. through statistical mechanics, thermodynamics and chemical kinetics. Although many of the attributes of living matter can be analyzed through such systems, life is a coordinated activity of entire organisms never fully under the experimenter's control. The alteration in physical thinking needed to deal with this situation may prove to be the most important consequence of our growing concern with living matter.