TOPOGRAPHY OF NUCLEIC ACID HELICES IN SOLUTIONS .9. MODELS FOR INTERACTIONS OF OPTICALLY ACTIVE DIAMINES AMINO ACID AMIDES DIAMINO ACIDS AND LYSYL DIPEPTIDES WITH NUCLEIC ACID SYSTEMS

Molecular framework models of the complexes formed between the salts I, N+ +H3CHRCONHCH2CH2N +-Me2H-2Br-; II, N+H3C(COr)H(CH2)nN+H3-Cl-(n = 2, 3, and 4); III,N+H3C((CH2)4N+H3)HCONHCHRCO2- Cl-; and IV, N+H3CHRCH2N+H3-2Cl- (R = Me and CO2H) and adjacent phosphate anions of a helical polynucleotide chain have been examined in detail; 15-, 16-, 17-, and 18-membered rings are formed as the result of complexing the salts I-IV to the nucleic acid helix. It is shown that certain conformations are not as favorable as others. Moreover, it is possible to predict which of the two optical isomers of the salts I-IV should interact to a greater extent with a nucleic acid helix. The results using 11 different sets of optical isomers of the salts I-IV on three different helical structures, i.e., poly I-poly C, poly A-poly U, and calf thymus DNA, have been predicted correctly and consistently. © 1968, American Chemical Society. All rights reserved.