assuming the ylide mechanism of exchange reaction it is suggested that the lower rate of 1h leads to 3h exchange in c ( 8 ) h-groups of purinic residues in polynucleotides of a-form ( rna and other polyribonucleotides ) as compared to those of b-form ( dna and other polydeoxyribonucleotides ) might be accounted for by decreased availability of c ( 8 ) h-groups for oh-ions of the solvent due to a different microenviroment of these groups in a- and b-type helixes .
C0032550
polynucleotides
C0032590
polyribonucleotides