The reaction of glyoxal with nucleic acid components III. Kinetics of the reaction with monomers

1. The reaction of glyoxal with nucleic acid components has been studied spectrophotometrically. 2. The reactions of adenosine and cytidine with glyoxal are reversible. The equilibrium constants at pH 6.95 and 20° are 1.4 and 5.8, respectively. Adenosine and cytidine adducts are labile and cannot be isolated from the reaction mixtures. 3. The formation of the guanosine-glyoxal adduct is slower than those of adenosine and cytidine. The reaction product is much more stable. The stability of the adduct increases in borate buffers. 4. The rate of the guanosine reaction with glyoxal increases with increasing pH. The dependence of the reaction rate on pH in borate buffer is bell-shaped and has a maximum at pH 7.8. Ionic strength does not considerably affect the rate of the reaction.