CD studies of double‐stranded polydeoxynucleotides composed of repeating units of contiguous homopurine residues

Abstract

Abstract Double‐stranded synthetic polydeoxynucleotides of the general form poly[d(G n C n )] · poly[d(G n C n )], poly[d(G n C)] · poly[d(GC n )], and poly[d(A n T n )] · poly[d(A n T n )] have been synthesized. When n = 4 or larger, the CD spectra of polymers of the form poly[d(G n C n )] · poly[d(G n C n )] or poly[d(G n C)] · poly[d(GC n )] closely resemble the spectrum of poly[dG] · poly[dC], suggesting that a string of four continguous guanosine residues is sufficient to induce a conformation resembling that of the polypurine · polypyrimidine. With polymers of the form poly[d(A n T n )] · poly[d(A n T n )], however, the CD spectrum only gradually approaches that of poly[dA] · poly[dT].