| Abstract: | Poly(vinyl alcohol) has been substituted with oligodeoxythymidylic acid and the resulting polyanion irreversibly attached to DEAE-cellulose via ionic bonding. Peptide-oligonucleotide interactions have been studied using a column chromatography technique with the PV(pT)n-DEAE-cellulose as stationary phase. Of all the naturally occurring amino acids, only tryptophan and to a lesser extent tyrosine intreact significantly with the immobilized oligodeoxythymidylic acid residues under the conditions for base pairing. The homopolymers of tryptophan and tyrosine undergo greater retardation than the monomers, such that the effect is not additive but multiplicative. Thus Tyr-Tyr-Tyr shows an eightfold and Trp-Trp-Trp an approximately 30-fold larger retardation than tyrosine and tryptophan, respectively. The peptide-oligonucleotide interaction decreases considerably when nonaromatic amino acids are present in the peptide. Consequently, naturally occurring peptides and proteins which contain relatively small amounts of tryptophan and tyrosine compared with the nonaromatic amino acids undergo at the most only slight retardation on the PV(pT)n-DEAE-cellulose. The retention of oligonucleotides and peptides containing these aromatic amino acids is due in both cases mainly to base stacking (roughly 67% of the total interaction) but involves different mechanisms. Thus, the peptides interact preferably with the cellulose matrix whereas the oligonucleotides with the immobilized oligonucleotides. Interaction via hydrogen-bond formation makes up the remaining 33% of the total interaction. The oligonucleotides and peptides of the mobile phase interact with each other also via this mechanism. The strength of the d(pA-A-A) interaction is roughly that of Trp-Trp whereas d(pA-A-A-A) is weaker than Trp-Trp-Trp. |
