Dynamical processes in proteins are studied by time-resolved fluorescence techniques. Fluorescence lifetimes and time-resolved fluorescence spectra can be measured on a picosecond time scale using a ps Ti:sapphire laser, both by time correlated single photon counting (time resolution about 15 ps), and by means of a fast-gated CCD camera (resolution 200 ps). Dynamics on a nano to millisecond time scale can be triggered by a Temperature Jump (T-jump) system, based on a Raman shifted nanosecond pulse from a Nd:YAG laser. Several systems are under investigation within the context of the Chemistry of Complex Molecules program in the chemistry department, in collaboration with the Molecular Toxicology and Biochemistry groups: substrate binding to cytochrome P4502D6, and chaperone-assisted folding dynamics of the capsid protein gp23 of the T4 bacteriophage. The T-jump method is currently used to study the dynamical behavior of melittin and flavodoxin (in collaboration with the Biology department) on a microsecond timescale. Fluorescence methods are also used to study ligand binding and conformational changes in the H1 histamine receptor, in collaboration with the Medicinal Chemistry group. Other topics of interest are excited-state proton transfer in salicylic acid derivatives and azo dyes, and photophysical properties of H1 agonists and antagonists.
Changes in fluorescence intensity of monomeric and tetrameric mellitin, following a
nanosecond temperature jump of ~6 °C. Monomeric melittin shows complicated behavior
on a microsecond time scale that is absent for the tetramer. With the current set-up it is
possible to measure changes in fluorescence intensity, and in fluorescence lifetimes.