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Topography of Nucleic Acid Helices in Solutions. VI. The Eflect of Amino Acid Derivatives on the RNAse-Catalyzed Hydrolysis
Demonstration of an Assymetric Surface of Polyadenylic Acid.
It has been shown recently that the amino acid amides of the general structure, I, NH3CHRCONHCHzCH2NMe2H -2Rr-interact strongly with nurleic acid helices.' By examining the effect of the amides, I, on the melting temperature, T,, of the helixcoil transition of various nucleic acid helices it was demonstrated that the extent of stabilization of the helical structure depends not only on the nature of the amino acid but also on the particular enantiomer. For example, the L-amino acid derivatives, i.e., alanine, a-aminobutyric, proline, and lysine stabilized the double stranded polyrihocytidylic-polyriboinosinic acid (rI-rC) to a greater extent than the corresponding D-amino acid derivatives. Similar observations, i.e., greater stabilization by the L-derivatives, was also noted for the triple stranded rA-rU2, and the double-stranded calf thymus DNA.' The results may be interpreted in terms of relative stabilization of the douhlestranded nucleic acid helices hy the L-amino acid amides, I, or in terms of relative stahilization of the random coils by the D-amino acid amides, I, and/or-both. In order to assess the contribution of the latter, i.e., relative stahilization of the random coils by the L-and D-amino acid derivatives, we have examined the effect of the amides, I, on the RNAse-catalyzed hydrolysis of polyadenylic acid. Gabbay and Shimshakz have shown that diquaternary ammonium salts of the general structure, IllR2R3N(CH2)n-