Deuterium substitution molecular conformation

Thus, identification of all pairwise, interproton relaxation-contribution terms, py (in s ), for a molecule by factorization from the experimentally measured / , values can provide a unique method for calculating interproton distances, which are readily related to molecular structure and conformation. When the concept of pairwise additivity of the relaxation contributions seems to break down, as with a complex molecule having many interconnecting, relaxation pathways, there are reliable separation techniques, such as deuterium substitution in key positions, and a combination of nonselective and selective relaxation-rates, that may be used to distinguish between pairwise, dipolar interactions. Moreover, with the development of the Fourier-transform technique, and the availability of highly sophisticated, n.m.r. spectrometers, it has become possible to measure, routinely, nonselective and selective relaxation-rates of any resonance that can be clearly resolved in a n.m.r. spectrum. 

Recently, it was shown that spin-label ESEEM of partly deuterated systems is helpful for studying different aspects of intermolecular interactions, molecular assemblies and conformation in complex biological media. A short survey has been published by one of us, covering structural ESEEM studies of this kind in biological membranes that appeared before 2012. In this review, we discuss recent applications of spin-label ESEEM with deuterium substituted molecules, covering also other experimental fields. Also, special attention is paid here to discussion of experimental approaches and limitations, and the theoretical background of the method. 

Deuterium NMR of polyphosphazenes substituted by perdeutero or selectively deuterated ethyls was interpreted by threefold jumps among the three conformational minima [30]. Molecular mechanics models gave support to a concerted motion of the ethyls surrounding the main chain, which is thus embedded in a "soft cylindrical environment, fitting a hexagonal lattice. 

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