PROTEIN FLUORESCENCE, DYNAMICS AND FUNCTION - EXPLORATION OF ANALOGY BETWEEN ELECTRONICALLY EXCITED AND BIOCATALYTIC TRANSITION-STATES

With the advent and development of time-resolved spectroscopic techniq ues and substantial progress in understanding of photophysical and pho tochemical phenomena, a new goal may be achieved: modeling of biochemi cal reaction or its elementary step by a photochemical event occurring within the probe, bound to a protein molecule. The probe may be locat ed in a well-determined site of the protein matrix and report on the m odulation of the reaction rate by the matrix and by the surrounding so lvent, or by interactions in multiprotein complexes and in biomembrane s. The advantages of this approach are obvious: in contrast to ordinar y biochemical reaction, the excited-state reaction may be started by a short light pulse, and its kinetics may be observed directly with hig h resolution in time. In addition, if the reaction rate is influenced by the dynamics of the protein matrix, these dynamics may be studied s imultaneously with the reaction, by using the same or a similar probe and within the same time range. In this review, the prospects for appl ication of probes exhibiting electron transfer, proton transfer, molec ular rotations and isomerizations are presented and discussed. The gen eral problem of photochemical modeling of biochemical reactions is dis cussed. This modeling may result in deeper understanding of enzyme cat alyzed reaction mechanisms.