Interaction Between Tyrosine and Divalent Sulfur in Fluorescence Quenching and in the Photochemistry of Ribonuclease

Abstract

Abstract— –Ribonuclease is inactivated in aqueous solution by u.v. light through different mechanisms according to whether divalent sulfur or aromatic amino acids are the primary light absorbers. At 284 nm, absorbed mainly by tyrosine, the presence of O2 inhibits photoinactivation and H2S formation, but does less so at 254 or 313 nm. Based on data with model substances containing disulfide groups a mechanism is indicated in which excited tyrosine is quenched through electron transfer to adjacent divalent sulfur within the protein. Disulfide compounds are shown to be very efficient quenchers of tyrosine fluorescence.

Esr Studies of the Low Temperature Irradiation of Keratin and Its Component Amino Acids

“…Thus the tyrosine chromophore ejects an electron into the matrix, this electron is attracted by the high affinity sulphur groups in competition with the dielectric traps in the matrix to produce the disulphide anion radical. This conclusion is in accordance with the proposals of Grossweiner and Usui [34] and Arian et al [35].…”

Near-infrared Fourier transform Raman and conventional Raman studies of calf gamma-crystallins in the lyophilized state and in solution

“…The present demonstration of the absence of a disulfide linkage in native -y-II crystallin is also important in ascertaining whether lens crystallins contribute only to the structural characteristics of the lens or they are also metabolically active (24). The presence of such a linkage in -y-II crystallin would imply its involvement in oxidation/ reduction and possibly in free-radical quenching reactions (49,50). Although -y-crystallins scavenge hydrated electrons more efficiently than a-crystallin (25), the unusual stability of y-crystallins against oxidative SH to SS conversion argues against their role in redox reactions.…”

Comparative study on the structure and stability of bovine seminal ribonuclease, its monomeric bis(S-carboxymethylated-31,32) derivative, and bovine pancreatic ribonuclease

“…In fact, it has been shown that sulfur-containing molecules quench the fluorescence of tyrosine and tryptophan (Arian et al, 1970;Bent & Hayon, 1975;Longworth, 1968). More recently (Morgan et al, 1978), it has been proposed that fluorescence quenching in pancreatic RNase A is due to the existence of regions in which the side chains of sulfur-containing amino acids (cystines and methionines) alternate in space with side chains of tyrosine, leading to an S-a interaction which causes quenching of tyrosine fluorescence.…”