Ultrafast charge transfer and solvation of DNA minor groove binder: Hoechst 33258 in restricted environments

Picosecond resolved photophysical studies on a DNA minor groove binder, H33258 in bulk buffer and various restricted media including DNA reveal excited state charge transfer as an important mode of excited state relaxation. The charge transfer is found to be essentially associated with intramolecular twisting of the probe, being absent in SDS micellar environment and in DNA where twisting is hindered. Solvation and rotational dynamics of the probe in various restricted media including DNA are explored. A significantly longer component (8.5 ns) in DNA-solvation dynamics, which is well known to be associated with δ-relaxation of the DNA, is identified.