Binding of Mn2+to Nucleic Acids

摘要

Measurements of the nuclear magnetic resonance relaxation timesT1andT2of the water protons in aqueous solutions of nucleic acids and magnetic metal ions allow one to determine details about the metalhyphen;ion binding. When Mn2+is bound, the rotation of its hydration sphere becomes slower, so that its effectiveness in reducing the protonT1from its value in pure water is enhanced. This relaxation enhancement has been measured for Mn2+bound to DNA, RNA, synthetic polynucleotides, andE. coliribosomes. Compared to water as unity, the enhancement factors range from 3.7 for polyuridylic acid to 16.7 for polyadenylic acid. The equilibrium constants for binding, and the concentration of binding sites have been calculated from the dependence of enhancement upon Mn2+concentration.