Premium
Depolarized light scattering by amides and peptides
Author(s) -
Ingwall R. T.,
Flory P. J.
Publication year - 1973
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.1973.360120515
Subject(s) - chemistry , polarizability , amide , aqueous solution , rayleigh scattering , tensor (intrinsic definition) , anisotropy , dilution , dimethylacetamide , extrapolation , crystallography , analytical chemistry (journal) , solvent , thermodynamics , molecule , organic chemistry , physics , mathematics , quantum mechanics , pure mathematics , optics , mathematical analysis
Abstract The Rayleigh ratios R H have been measured for the depolarized scattering dilute solutions of N ‐ethylacetamide (EA), N ‐methylpropionamide (MP), and N ‐acetyl‐pyrrolidine (AP) in P ‐dioxane, and dilute aqueous solutions of N ‐methylacetamide (MA), N , N ‐dimethylacetamide (DMA), EA, and MP. Squares of the optical anisot‐ropies γ of the amides are obtained through extrapolation of these mesurements to infinite dilution. Values of γ 2 found for EA and MP in dioxane are in good agreement with calculations based principally on the previously evaluated polarizability tensor of the amide group in conjunction with CC and CH bond polarizabilities. The calculations also involve averaging over all conformations, each being weighted according to the estimated conformational energy. The mean‐squared optical anisotropies (γ 2 ) of the oligoglycines and oligoalanines are calculated by similarly averaging over all skeletal conformations. The anistropic polarizability tensor \documentclass{article}\pagestyle{empty}\begin{document}$ \hat \alpha $\end{document} for the prolyl structural unitis derived for γ 2 for AP. The much larger optical anisotropies exhibited by the amides when dissolved in water as compared with those observed in dixane are discussed.