Bisulfite Modification of Nucleic Acids and their Constituents

Abstract

Publisher Summary This chapter discusses that nucleic acids are labile in solutions of extreme pHs and at high temperatures; the chemical modification must preferably be performed at a pH region around neutrality and at a temperature near 37°C or below. Chemical reactions that satisfy these requirements have been developed and used in nucleic acid studies. Bisulfite deaminates cytosine to give uracil. The reaction conditions are satisfactorily mild, and no deamination of adenine or guanine moieties takes place under the conditions employed. Although bisulfite does react with uracil and thymine under similar conditions, the bisulfite adducts formed are easily reverted to the parent pyrimidines. Therefore, cytosine residues in nucleic acids can be selectively transformed into uracil residues by the use of bisulfite. The most important feature of bisulfite reactions is their strict selectivity for the single-stranded regions of nucleic acids. Thus, bisulfite is a reagent that meets in excellent fashion the requirements to serve as a probe of nucleic acid functions and structures. In spite of the fact that the bisulfite reactions of nucleic acid components were discovered only several years ago, extensive studies of the reaction at the polynucleotide level have already been made and a number of applications reported. These involve (1) application for synthetic purposes, (2) studies on physical and biochemical properties of bisulfite-treated polynucleotides, (3) cross-linking of nucleic acid with protein, (4) chemical modifications of transfer RNA with the purpose of elucidating functional sites and conformations, and (5) induction of mutation in microorganisms.