| Abstract
| - The backbone states of B-DNA influence its helical parameters, groove dimensions, and overallcurvature. Therefore, detection and fine characterization of these conformational states are desirable. Usingroutine NMR experiments on a nonlabeled B-DNA oligomer and analyzing high-resolution X-ray structures,we investigated the relationship between interproton distances and backbone conformational states. Thethree H2‘i−H6/8i+1, H2‘ ‘i−H6/8i+1, and H6/8i−H6/8i+1 sequential distances were found cross-correlated andlinearly coupled to ε−ζ values in X-ray structures and 31P chemical shifts (δP) in NMR that reflect theinterconversion between the backbone BI (ε−ζ < 0°) and BII (ε−ζ > 0°) states. These relationships providea detailed check of the NMR data consistency and the possibility to extend the set of restraints for structuralrefinement through various extrapolations. Furthermore, they allow translation of δP in terms of BI/BII ratios.Also, comparison of many published δP in solution to crystal data shows that the impact of sequence onthe BI/BII propensities is similar in both environments and is therefore an intrinsic and general property ofB-DNA. This quantification of the populations of BI and BII is of general interest because these sequence-dependent backbone states act on DNA overall structure, a key feature for DNA−protein-specific recognition.
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