Effect of non‐complementary nucleotides on the rate of helix formation: Kinetics of formation of poly (I)·poly (C,I) and poly (I)·poly (C,U) complexes

Apparent second‐order rate constants for complex formation between poly (I) and poly (C) and copolymers of C containing non‐complementary I or U residues have been determined spectrophotometrically. The rate constants decrease as the concentration of either I or U in the C strands increases–the effect seems insensitive to the species of residue involved, when differences in the thermal stabilities of the poly (I) poly (C,I) and poly (I). poly (C,U) complexes are taken into account. These results suggest that low concentrations of relatively stable defects can alter the apparent kinetic “complexity” of polynucleotides as determined by hybridization methods (C₀t analysis).