INTERACTION OF FORMALDEHYDE WITH NUCLEIC-ACIDS AND THEIR STRUCTURAL COMPONENTS IN THE PRESENCE OF AMINES .5. H-3 -] H-1 HYDROGEN ISOTOPE-EXCHANGE AT THE C-8 ATOM OF DATP, ADENOSINE, ADENINE, GUANOSINE, AND POLY(A)

Addition of formaldehyde together with an aliphatic amine having an amino terminal amino group (Gly, its methyl and ethyl esters, Gly-Gly-Gly tripeptide, taurine, ethanolamine, methylamine, ethylamine) to [8-H-3]dATP, [8-H-3]A, or [8-H-3]poly(A) under conditions close to physiological (pH 5.5-9.0, 40-50 degrees C) initiates fast H-3 --> H-1 hydrogen isotope exchange at the C-8 atom of the adenine residue. The rate of hydrogen exchange is more than two orders of magnitude less when a secondary amine is used instead of a primary amine. In contrast, hydrogen exchange at the C-8 atom was slow for: 1) guanosine with formaldehyde-Gly or formaldehyde-sarcosine; 2) adenosine with formaldehyde-sarcosine. The mechanism of fast hydrogen exchange at the C-8 atom of 9-substituted adenines under the conditions of the Mannich reaction via the formation of N-6,N7-cyclic derivative intermediates is discussed.