Light Scattering Studies of DNA Dynamics

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The aqueous ionic milieu influences long-range intermolecular interactions between DNA molecules, the degree of expansion or condensation of the DNA molecular coil and the short range helical structure. Within each of these domains, there are striking transitions not yet clearly understood on the basis of existing polyelectrolyte theory or nucleic acid chemistry. Dr. Bloomfield's goal is to understand the forces mediating these transitions. Some of the techniques to be used are dynamic laser scattering, small angle X-ray and neutron scattering, UV-visible, CD and laser Raman spectroscopy and chemical probes. Theoretical techniques will also be used. DNA undergoes some striking phase changes. All of these transitions depend strongly on ionic strength as well as on other variables such as polymer concentration, molecular weight, temperature and specific ion effects. Molecular biology has thus far concerned itself primarily with coding- type data. However, at a higher level, the choice of a code which is used (i.e., the DNA) has control mechanisms built into it which are widely believed to involve in part, binding of other control molecules to the DNA, and in part, changes in the DNA conformation. Knowledge of ways in which DNAs are likely to interact must precede some types of understanding of control mechanisms and the experiments proposed here treat precisely this problem.***//