Thermodynamic analyses of the specific interaction between C:C mismatch base pair and silver (I) cation: toward the efficient detection of single nucleotide polymorphism.

We examined the effect of silver (I) cation on the thermal stability of heteroduplex and homoduplex. Addition of silver (I) cation increased the melting temperature of heteroduplex containing C:C mismatch base pair by about 4 degrees C. The thermal stability of homoduplex and heteroduplexes containing other kinds of mismatch base pairs was not significantly changed by the addition of silver (I) cation. Isothermal titration calorimetric study demonstrated that silver (I) cation directly bound to C:C mismatch base pair in heteroduplex at a molar ratio of 1:1. The binding constant and the enthalpy change for the binding of silver (I) cation to C:C mismatch base pair was approximately 10(6) M(-1) and -3 kcal mol(-1), respectively. We conclude that silver (I) cation directly binds to C:C mismatch base pair in heteroduplex with high affinity and specificity. Our results certainly support the idea that the addition of silver (I) cation to C:C mismatch base pair in heteroduplex could be a convenient strategy for heteroduplex analysis and may eventually lead to progress in single nucleotide polymorphism genotyping.