The Alkali-Stable Dinucleotide Sequences in 18 s + 28 s Ribonucleates From Wheat Germ

The 2′-O-methyl substitution of ribose residues of ribonucleate chains can give rise to 16 alkali-stable dinucleotides having the general structure NxpNp in which N is any of the four major ribonucleosides and Nx is the 2′-O-methyl derivative of any of the four major ribonucleosides. Quantitative data are presented which show that all of these 16 alkali-stable dinucleotides occur in characteristic amounts in alkali hydrolyzates of the 18 S + 28 S ribonucleates from wheat germ. The alkali-stable dinucleotides cumulatively account for 3 mole% of the total nucleotides of the 18 S + 28 S wheat germ ribonucleates. The relative amounts of the four 2′-O-methyl ribosides responsible for the alkali stability of the dinucleotides have been shown to be distinctly different from the relative amounts of the four corresponding normal ribosides which participate in either the alkali-stable dinucleotide sequences or in the ribonucleate chains as a whole. Quantitative end group data show that the alkali-stable dinucleotide sequences occur internally in high molecular weight ribonucleate chains. Preliminary data are presented on the occurrence of alkali-stable trinucleotides in alkali hydrolyzates of the 18 S + 28 S wheat germ ribonucleates.