Topography of nucleic acid helices in solutions. II. Structure of the double‐stranded rA–rU, rI–rC, acid rA, and the triple‐stranded rA–rU 2 and rA–rI 2 helices
1967; Wiley; Volume: 5; Issue: 8 Linguagem: Inglês
10.1002/bip.1967.360050807
ISSN1097-0282
Autores Tópico(s)HIV/AIDS drug development and treatment
ResumoAbstract Information concerning the structures of rA–rU, rA–rU 2 rI–rC, rA–rI 2 , and acid rA helices in solutions is reported. Through the use of diquaternary ammonium salts of the general structure, \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm R}_1 {\rm R}_2 {\rm R}_3 \mathop {\rm N}\limits^ + ({\rm CH}_2 )n\mathop {\rm N}\limits^ + {\rm R}_1 {\rm R}_2 {\rm R}_3 \cdot 2{\rm Br}^ - $\end{document} (I), it is shown that ( 1 ) the distances between adjacent negatively charged oxygen atoms on the helix increases in the following order rA–rI 2 < rI–rC < rA–rU ⩽ rA–rU 2 ; ( 2 ) the density of the helices increases in the order. rA–rI 2 < rA–rU < rA–rU 2 < rI–rC; ( 3 ) there is a large hydrophobia site in rA–rI 2 and possibly also in rA–rU, rA–rU 2 , and rI–rC helices; ( 4 ) the results of the interactions between the salts of type I and the helices may be formulated in semi‐quantitative terms by the use of two parameters, α, and β which are shown to be related to the charge separation and the density of the helices, respectively; ( 5 ) the studies in solutions compare favorably with the x‐ray studies on the fibers; and ( 6 ) the acid rA helix differs significantly from the other helices by the fact that the electrostatic interstrand interactions between the negatively charged oxygen atom of a phosphate group and the positively charged 10‐amino group of adenine contribute significantly to the stabilization of the helix, and thus it is found that the presence of the salts, I, leads to a significant destabilization of the acid rA helix.
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