Soluble wool Proteins. II. Light scattering and viscosity in formic acid and dichloroacetic acid solutions

Abstract

The light scattering and viscosity behaviour of S-carboxymethylkerateine 2 (SCMK2) and α-keratose have been investigated in formic and dichloroacetic acids. The viscosity at 25 °C of formic acid solutions of SCMK2 and α-keratose showed a large decrease with time over a period of 4 weeks. On the other hand, no parallel changes in light scattering were observed and no conclusive evidence for peptide bond hydrolysis could be found. Time effects in dichloroacetic acid were negligible. SCMK2, but not α-keratose, behaved as a polyelectrolyte in formic acid, the reduced viscosity increasing at low concentrations an effect which was eliminated by the addition of salt. The effects of salt concentration on the plots of K₉₀c/R₉₀ against c for solutions of SCMK2 in formic acid were typical of those for highly charged proteins in aqueous solution. Solutions of α-keratose in formic acid and of both proteins in dichloroacetic acid did not show these effects at low ionic strengths. The solvents employed did not disaggregate the wool proteins to the same extent as 8M urea, 10M acetic acid, or sodium dodecyl sulphate. Variability of the physical properties of different preparations in the two non-aqueous acids is attributed to varying degrees of aggregation.