RADIATIONLESS DECAY FROM THE LIGAND-TO-METAL CHARGE-TRANSFER STATE INTHE BLUE COPPER PROTEIN PLASTOCYANIN

The cysteine S(p pi) --> Cu(2+)d(x2-y2) ligand-to-metal charge-transfe r (LMCT) state in plastocyanin exhibits a time-resolved pump-probe spe ctrum that has excited-state absorption and stimulated-emission compon ents to the blue and red, respectively, of the absorbtion maximum. The LMCT state returns to the ground state by populating the d(xz+yz) --> d(x2-y2) ligand-field (LF) state. The lack of hole-burned features in the time-resolved spectra implies the presence of intramolecular vibr ational redistribution and/or protein-matrix solvation dynamics on a t ime scale that is shorter than the 125 fs lifetime of the LMCT state. (C) 1997 Elsevier Science B.V.