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A new approach utilizing high‐resolution proton NMR in structural analysis of intercalation complexes of natural DNA
Author(s) -
Chandrasekaran S.,
Kusuma S.,
Boykin David W.,
Wilson W. David
Publication year - 1986
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/mrc.1260240713
Subject(s) - intercalation (chemistry) , chemistry , phenanthrene , titration , acridine , proton nmr , proton , carbon 13 nmr , crystallography , stereochemistry , inorganic chemistry , organic chemistry , quantum mechanics , physics
Abstract Protons on the antimalarial intercalator quinacrine and a substituted phenanthrene intercalator were monitored on titration with sonicated DNA. The titrations were carried out below the DNA T m but at a temperature, ionic strength, and intercalator concentration sufficient to give fast exchange conditions and a minimum of dimerization of the planar aromatic intercalators. Line widths were kept within reasonable limits by using sonicated DNA, high temperature, fast exchange conditions and an excess of intercalator over DNA binding sites. Proton assignments were made using analysis of chemical shifts, coupling patterns, NOE and 2D methods. 2D COSY experiments on DNA‐intercalator complexes were performed to assist in assigning protons for the bound intercalator. Line broadening with quinacrine is more severe than with the phenanthrene, and the acridine essentially represents the limit of the NMR titration method. The phenanthrene intercalator, on the other hand, illustrates the power of the method, particularly when analyzing a series of compounds. Using chemical shift changes of the phenanthrene on titration with DNA and space filling molecular modeling studies, we have been able to propose a general structure for the phenanthrene intercalation complex.