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We present estimates of the bond-length and bond-angle parameters for the nitrogenous base side groups of nucleic acids. These values are the result of a statistical survey of small molecules in the Cambridge Structural Database for which high-resolution X-ray and neutron crystal structures are available. The statistics include arithmetic means and standard deviations for the different samples, as well as comparisons of the population distributions for sugar- and non-sugar-derivatized bases. These accumulated data provide appropriate target values for refinements of oligonucleotide structures, as well as sets of standard atomic coordinates for the five common bases.
Clowney et al. (Mon,) studied this question.