28—EXAMINATION IN THE ELECTRON MICROSCOPE OFS-CARBOXYMETHYLKERATEINE-A AND OF THE HELIX-RICH FRACTION OBTAINED FROM IT BY PARTIAL PROTEOLYSIS

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Abstract
An account is given of an investigation in which the low-sulphur S-carboxy-methylkerateine fractions (SCMK-A) from wool, human hair, and ovine horn were dried from, solution at various pH values and the films so formed examined in the electron microscope, both negative-staining and platinum-shadowing techniques being used. Rod-shaped particles, spheroidal aggregates, and filaments were observed. At pH 2.5–3.5, spheroids predominated, and at pH 90 the rod-shaped particles predominated, whereas filament formation was favoured near neutrality. The filaments had diameters of 20–50 Å; the rod-shaped particles had diameters of about 20 Å and lengths ranging from less than 200 Å to about 800 Å, the most favoured lengths having a common factor of about 160 Å. The spheroids ranged in diameter from about 100 Å to about 600 Å and were usually flattened. The helix-rich fractions obtained by partial digestion of SCMK-A with Pronase P or chymotrypsin appeared to consist chiefly of rod-shaped particles at pH 6–9. The size of these particles (160–170 Å × 20 Å) was in good agreement with hydrodynamic measurements.