Abstract
Triethyloxonium fluoroborate (TEOF), which is one of the ethylating agents, was substantially inactive to adenosine 5'-monophosphate (AMP) at various pHs. TEOF reacted on cytidine 2'(3')-monophosphate (CMP), uridine 2'(3')-monophosphate (UMP) and guanosine 5'-monophosphate (GMP) in pH 7-11 buffer solutions having a moderate ionic strength (μ≃0.6) to give the corresponding ethylated nucleotides. The extent of ethylation was influenced by the pH and especially the ionic strength of the buffer employed. At lower ionic strength (μ<0.2) TEOF was much less reactive toward CMP and UMP. When ribonucleic acid (RNA) was treated with TEOF in a buffer solution at pH 8.9 and μ=0.1 and hydrolyzed with hydrochloric acid, the resulting hydrolysate contained approximately 50% of the ethylated guanine residue by base analysis. Deoxyribonucleic acid (DNA) was ethylated to a similar extent under the same conditions. In both cases, the chromatographic analysis revealed that uracil (thymine), cytosine, and adenine residues were left practically intact. The ethylated DNA contained a small amount of dialyzable material which was identical with 7-ethylguanine. The physical properties showed that DNA on ethylation underwent partial loss of tertiary structure although the molecule retained considerable double strandedness.
