STUDY OF DNA INTERNAL DYNAMICS BY QUASI-ELASTIC LIGHT-SCATTERING

We have studied the large-scale internal fluctuations in DNA coils by using quasi-elastic light-scattering spectroscopy. We have measured th e angular dependence of the first cumulant of the scattered-light auto correlation function. Within the q(3) domain of this dependence, we ob served the transition from the asymptotic behavior predicted for good solvents to the asymptotic behavior predicted for Theta conditions. Th is allowed us to determine the screening length of volume interactions in DNA chains. Analysis of the autocorrelation functions by a regular ization procedure allowed us to reconstruct the mode composition of th e scattered light and to determine the relaxation time of the fluctuat ions in the coil size. (C) 1997 Optical Society of America.