TY - JOUR T1 - Chemical Methylation of Synthetic Polynucleotides JF - Molecular Pharmacology JO - Mol Pharmacol SP - 585 LP - 592 VL - 2 IS - 6 AU - DAVID B. LUDLUM Y1 - 1966/11/01 UR - http://molpharm.aspetjournals.org/content/2/6/585.abstract N2 - Polynucleotides were methylated in aqueous solution at 25° with methyl methanesulfonate. The reactions followed second-order kinetics, with relative reactivity of bases decreasing in the order: guanine > cytosine > adenine > uracil. Light scattering and viscosity techniques showed no changes in physical structure of polyuridylic acid, indicating that no methylation of the phosphodiester bond had occurred. Both polyadenylic and polycytidylic acids showed a decrease in molecular dimensions at low levels of methylation, presumably resulting from protonation of the substituted bases. As reported previously, polyadenylic acid showed a tendency to aggregate, but there was no evidence for such aggregation with methylated polycytidylic acid. ACKNOWLEDGMENT This work was supported by Grant PRA-10 from the American Cancer Society and by Public Health Service Grant No. GM-12416 from the National Institute of General Medical Sciences. ER -