Progress in the high resolution electron microscope studies of alpha Keratin

A scheme is suggested to assess quantitatively the effect of electron irradiation on molecular structure. In the case of alpha-Keratin, decay of the 5.1A meridional reflection (generally associated with the 'coiled-coil' system of α-helices) was assessed by a computer aided technique, from microdensitometer traces taken along the meridian in a series of electron diffraction patterns recorded under known instrumental conditions. The effect of preparative procedures such as 'staining' of biological specimens for electron microscopy, on the rate of decay of order in the specimen in the electron beam, was also investigated. In particular, the response to electron irradiation of Keratin in which the cystine linkages were reduced and specifically labelled by methylmercuric iodide, was examined. (R.L.)