Figure 3.

Interspersed d(AGG) trinucleotides lower the melting temperature of G′2 tetraplex d(CGG)₁₈. Duplicate samples of bimolecular tetraplex structures of 5′-³²P-labeled tail d(CGG)₁₈ and tail d(A/CGG)₁₈ 1:7 were formed as described in Figure 1 and suspended at 30 µM each in TE buffer containing 50 mM NaCl. Tetraplexes of tail d(CGG)₁₈ and tail d(C/AGG)₁₈ 1:7 constituted 33.5 and 14.5%, respectively, of the total DNA input. Aliquots of the DNA solutions were incubated for 10 min at the indicated increasing temperatures. Tetraplex DNA was resolved from denatured DNA single-strands by electrophoresis through a non-denaturing 8% polyacrylamide gel and proportions of the remaining tetraplex structures were quantified by phosphorimaging analysis. Values shown are averages of two independent determinations at each temperature.