Organic Chemical Approach To Photo-Cross-Links Of Nucleic Acids To Proteins

Abstract

Various proteins are known to be linked covalently to nucleic acids under UV irradiation. The photo-cross-links occurs from the interacting states between nucleic acids and proteins. The present approach to this problem involves the characterization and identification of photoproducts obtained from model systems using simple pyrimidine bases and amino acids as well as some mechanistic aspects. 5-Bromouracil or its derivatives undergoes selective photocoupling to tnyptophan, indoles and some electron-rich aromatics under various irradiation conditions, where four modes of reactions were observed: involvement of (1) triplet bromouracil, (2) a double electron transfer in the presence of an electron carrier, (3) mixed aggregate formation in aqueous frozen solution, and (4) fluorescence quenching of the aromatics by bromouracil. Other topics of the photochemistry of pyrimidine bases, including synthesis of fluorescent uracils using photo-cross-coupling with 5-chloro- and 5-iodouracils, photoreactions between a 4-thiouracil and L-lysine and between thymine and L-tryptophan, and synthesis and behaviors of model compounds for stacking interactions between 5-bromouracil (or thymine) and tryptophan. Pergamon Press Ltd. © IUPAC