Biopolymers optically active compounds

Apart from intrinsically asymmetric chromophores, it is the existence of a dissymmetry in the space around the chromophores that makes their electronic transitions optically active. This dissymmetry is the result of the presence of one or more asymmetric centres (usually carbon atoms) and thus depends on structural factors (configuration, conformation). If the experimental or external conditions are modified (solvent, temperature, solution-composition), then there is a change in the conformational equilibrium which has some effect on the optical activity, thus justifying the interest of ORD and CD in the structural analysis of optically active compounds and particularly of helical conformation or helix-coil transitions of biopolymers. 

The measurement of vibrational optical activity has already proven to be a valuable tool in determining the structures of chiral compounds. Even relatively complicated natural compounds of medium size and the large biopolymers can reveal some of their structural secrets upon analysis of the VGA spectra. A bundle of theoretical models has been developed. Together with the fact that chiral substances become increasingly important for the chemical and pharmaceutical industry and have to be analysed somehow, the importance of vibrational optical activity, considered as a laboratory curiosity only some ten years ago, is to be expected to grow rapidly. 

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