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Volumetric Characterization of Homopolymeric Amino Acids

Volumetric Characterization of Homopolymeric Amino Acids

Gholamreza D Noudeh, Nicolas Taulier, Tigran V Chalikian

Biopolymers. 2003 Dec;70(4):563-74.

PMID: 14648766

Abstract:

We have determined the partial molar volumes, expansibilities, and adiabatic compressibilities for poly(L-alanine), poly(L-proline), and poly(L-threonine) within the temperature range of 18-55 degrees C. In addition, we have determined at 25 degrees C changes in volume, DeltaV, and adiabatic compressibility, DeltaK(S), associated with the coil-to-helix transitions of poly(L-lysine) and poly(L-glutamic acid) and the alpha-to-beta transition of poly(L-lysine). We have interpreted our volumetric data as suggesting that poly(L-alanine) and poly(L-proline) are not fully unfolded and, probably, retain some solvent-inaccessible core. Further, we propose that poly(L-threonine) is fully unfolded with the majority of its atomic groups being solvent-exposed. Near zero changes in volume and compressibility accompanying the coil-to-helix transitions of poly(L-lysine) and poly(L-glutamic acid) suggest that, in the absence of fortuitous compensations, the coil-to-helix transitions of the polypeptides do not result in any significant enhancement of solute hydration. By contrast, the alpha-to-beta transition of poly(L-lysine) causes slight but statistically significant increases in volume and compressibility, an observation that may suggest that the beta-sheet conformation of poly(L-lysine) is slightly less hydrated than its alpha-helical conformation. In general, our results provide a quantitative volumetric description of the hydration properties of the homopolymeric polypeptides investigated. Such characterizations should prove useful in developing an understanding of the role that solvent plays in the stabilization/destabilization of folded protein structures and protein complexes.

Chemicals Related in the Paper:

Catalog Number	Product Name	Structure	CAS Number	Price
AP82822126	Poly-L-threonine		82822-12-6	Price

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