Keratin Derivatives Research Articles

The Conformation of a Soluble Wool Keratin Derivative

The conformation of a low-sulphur soluble wool keratin derivative (SCMKA) has been studied by optical rotatory dispersion. On the assumption that the overall conformation consists of a mixture of a-helical and random-coil regions, this protein has a helical content of about 50% in aqueous solution at pH 9�1; this helical content does not vary with the degree of severity of the preparative procedure. The protein may be reversibly converted to the random-coil form by heating to 70�0, or by treatment with urea at concentrations exceeding 6r.r. An increase in pH to 12�5 causes very little change in conformation, such change as does occur being reversible. The maximum helical content which has been induced by solvents into the protein is about 62% in 2-chloroethanol. This probably represents the upper limit of the helical content of this protein as it occurs in the fibre. The changes in the conforma. tion of the protein which occur in several other solvents are briefly discussed.

Acrylonitrile-Stabilized Wool Keratin Derivatives

Acrylonitrile-Stabilized Wool Keratin Derivatives

The binding of dyes by soluble wool keratin derivatives

The binding of three acid dyes of slightly differing composition to a soluble wool keratin derivative has been measured by the dialysis-equilibrium method. The data satisfy the Klotz-Scatchard equation for the binding of small ions to proteins but the maximum amount of dye bound is much less than that equivalent to the number of basic side chains on the protein, given by amino acid analysis. It seems likely that the guanidino groups of the arginine residues are not able to bind dye anions, and it is suggested that this occurs because they are more firmly bound to other groups on the protein. Intermolecular bonding of this type would account for the high degree of aggregation shown by the soluble wool protein. The influence of pH and ionic strength on the binding of the three dyes is discussed in relation to their chemical structure.

Soluble wool proteins III. Optical rotation

The optical rotations, [α]D, of three soluble wool keratin derivatives have been measured in a large number of solvents using the sodium D line. A wide range of values was recorded. The values obtained for [α]D varied from -100� in typical protein denaturing agents such as 8M urea and 6M guanidine hydrochloride to near zero in some organic solvent mixtures. The results are interpreted in terms of the percentage of the polypeptide in the helical configuration. The relation between the optical rotation and the effectiveness of a solvent in disaggregating these proteins is discussed. The optical rotations of the proteins derived from wool appear to be influenced by the methods used to solubilize the proteins.

Keratin Derivatives Extracted From Wool with Alkaline Thioglycollate Solutions

In extension of previous work (Gillespie and Lennox 1953), the conditions under which proteins may be extracted from washed Merino wool have been further examined. Approximately 65 per cent. of the wool can be dissolved by a 40-min extraction at 50�C with O�1M thioglycollate at an initial pH of 12� 6. Electrophoresis at pH 11 in thioglycoIlate-glycine buffer indicated the presence of seven minor and one major component, the latter amounting to 41 per cent. of the wool. The minor components can be completely removed from the wool by five 2,O-min extractions with O�1M thioglycollate at an initial pH of 10�5. Extraction of the residue at pH 12�3 yields the major component. This moves as a single peak on electrophoresis between pH 8�0 and 12�0 in the presence of various buffers. It has a mobility of -7�2 X 10-5 cm2 V-I sec- I at a protein concentration of 0�5 per cent. in thioglycollate-glycine buffer of ionic strength O� 22 at pH 11� O. At higher protein concentrations there is anomalous behaviour on the descending boundary and tills can be prevented by increasing the ionic strength or replacing thioglycollic acid with mercapto-ethanol. The ascending pattern is unaltered by these changes or by increased protein concentration.

The Amino Acid Composition of Keratins II. The Amino Acid Composition of a Keratin Derivative Extracted From Wool With Alkaline Thioglycollate Solution

The amino acid composition of a protein component of Merino 64's quality wool, which moves as a single peak on electrophoresis in alkaline thioglycollate solutions, has been determined. The results, which are summarized in Table 1, show that the purified protein fraction contains more aspartic acid, glutamic acid, leucine, lysine, and amide nitrogen, and less cystine, proline, serine, and tryptophan, than the parent wool from which it was extracted.

The Molecular Weight At the Air-Water Interface of Some Keratin Derivatives Extracted From Wool

Using the monolayer technique, number-average molecular weights have been determined for a series of extracts of wool prepared by successive treatments with alkaline sodium thioglycollate. The molecular weights of these extracts have been discussed in relation to their electrophoretic patterns. The change in the number-average molecular weight in the successive extracts has been correlated with the presence of certain electrophoretic components. The possibility of extraction of lipoidal or other non-protein material from the cortical cell walls is discussed. A reversible dissociation of the major electrophoretic component at high pH was observed.

Preparation of an electrophoretically homogeneous keratin derivative from wool

Preparation of an electrophoretically homogeneous keratin derivative from wool