Ultraviolet Photochemistry as a Probe of Polyribonucleotide Conformation

Publisher Summary This chapter discusses that exposure of nucleic acids to small doses of near-ultraviolet radiation brings chemical changes only in their pyrimidine moieties. The photochemistry of nucleic acids is discussed and analysis is made of the conformational determinants of the photoreactivity of pyrimidine residues. Selective photochemical modification of complex polynucleotides appears to occur only under particular conditions of solvent, temperature, wavelength, and exposure. The chapter aims to provide a background for future refinement of ultraviolet photochemistry as a probe of nucleic acid conformation. The chapter focuses primarily toward studies with polyribonucleotides. The chapter concludes that in evaluating the ultraviolet photochemistry of polyribonucleotides in terms of the conformational dependence of the known photoreactions, it appears that unequivocal results for various types of model polynucleotides may be lacking. More selective modification procedures evolve with the discovery of sensitization conditions that favor particular macromolecular conformations. In sensitization techniques also lies the possibility for extending near-ultraviolet photochemistry to the purine residues of nucleic acids.