[Conformational transition of DNA within the B-family as revealed by anisotropy circular dichroism]

The native T2 DNA in solutions with different LiCl concentrations was oriented by pumping through a capillary device similar to that described in rf. 1. The change of the parallel, deltaepsilon parallel, and perpendicular, 2 delta epsilon perpendicular, components of circular dichroism tensor was studied as a function of salt concentration. Positive (delta epsilon parallel 280) and negative (2 delta epsilon perpendicular 280) components were shown to increase in absolute magnitude, so that there was a monotonous drop in the longwave band magnitude of the isotropic delta epsilon 280 as a result of compensation; the shortwave band magnitude of the isotopic delta 245 and its anisotropic components were constant. It is proposed that while the helix is winding as a result of LiCl rise progressive tilting of base pairs takes place. It was also shown that the glucosylated T2 DNA in solution is wound to a greater extent than the non-glucosylated DNA of the same GC-content.