ISSN:
0022-3832
Keywords:
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Physics
Notes:
Two soluble wool proteins, S-carboxymethylkerateine 2 (SCMK) and α-keratose, have been studied by viscosity, sedimentation, and diffusion methods. In aqueous buffers both proteins exist in an aggregated state with a wide distribution of particle size depending on the pH and ionic strength of the buffer. SCMK gives one peak in the ultracentrifuge except in the presence of 2 M guanidine hydrochloride, where two are observed. α-Keratose gives two polydisperse components under most conditions studied. Increase of ionic strength causes aggregation and increased heterogeneity of both SCMK and α-keratose. When stored at 25°C. both proteins show a decrease in viscosity and this has been shown for α-keratose to reflect an aggregation process which is more rapid a t pH 7.0 than a t pH 11. Disaggregation of both proteins can be brought about by either 8 M urea or by sodium dodecyl sulfate in amount equivalent to 2 moles of detergent per positive site on the protein, to give a more homogeneous protein of particle weight 45,000-50,000, both proteins under these conditions yielding one peak in the ultracentrifuge. Even further reduction in molecular size can be brought about by alkali at pH 13.0. The hydrodynamic parameters have been calculated where possible and interpreted on the basis of a spheroidal model for the molecule. In 8 M urea the molecules appear to be in a greatly expanded state, whereas the complexes with sodium dodecyl sulfate are more compact, having smaller axial ratios and hydrodynamic volumes. The possibility that the molecules exist as random coils in solution has been discussed.
Additional Material:
2 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/pol.1956.120219904
