Ultrafast studies of solution dynamics

This is the final report of a one-year, Laboratory Directed Research and Development (LDRD) project at Los Alamos National Laboratory (LANL). Fast chemical dynamics generally must be initiated photochemically. This limits the applicability of modern laser methods for following the structural changes that occur during chemical and biological reactions to those systems that have an electronic chromophore that has a significant yield of photoproduct when excited. This project has developed a new and entirely general approach to ultrafast initiation of reactions in solution: laser-induced temperature jump (T-jump). The results open entire new fields of study of ultrafast molecular dynamics in solution. The authors have demonstrated the T-jump technique on time scales of 50 ps and longer, and have applied it to study of the fast events in protein folding. They find that a general lifetime of alpha-helix formation is ca 100 ns, and that tertiary folds (in apomyoglobin) form in ca 100 {mu}s

Resonance Raman study of the primary photochemistry of visual pigments. Hypsorhodopsin

We report here the first resonance Raman results of octopus hypsorhodopsin, a species formed photochemically at very low temperatures from visual pigments. A pump-probe technique was used to obtain Raman spectra from samples at 12 degrees K whose photostationary state mixtures were either hypsorhodopsin rich or hysorhodopsin poor. The data strongly suggest that the Schiff-base linkage between the chromophore of hysorhodopsin and apoprotein is protonated. Further, the results suggest that hypsorhodopsin's chromophore is in some torsionally distorted conformation, possibly having torsional departures from an all-trans isomeric form