The proteins from a single 20-μm Merino wool fiber, after extraction at pH 8 with 8 Murea containing dithiothreitol, were radiolabelled by S-carboxymethylation with iodo(2-14C) acetate. The unfractionated mixture of proteins was examined by two- dimensional polyacrylamide gel electrophoresis, with the separation in the first dimension according to charge at pH 8.9 and in the second dimension according to apparent molecular weight by sodium dodecyl sulfate electrophoresis. Following electrophoresis the proteins were visualized by fluorography. Eight low-sulfur, eight high-sulfur, and ten high-tyrosine protein components were resolved. The method is extremely sensitive, with the proteins from approximately 4 cm of wool fiber being visualized in less than six hours. Because of the high sensitivity of the method, protein components in small samples—for example, those used in mechanical property measurements—can be examined.
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