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Clathrin is the major protein of coated membranes involved in receptor-mediated endocytosis and other membrane-trafficking reactions. The basic clathrin molecule, the triskelion, consisting of three heavy chains (190kDa) and three light chains (23-27kDa), polymerizes into a wide range of fenestrated polyhedral surface lattices. The capacity of triskelions to assemble into closed dodecahedral shells that are extravagantly polymorphic implies that certain degrees of freedom must be present in their molecular structure. To investigate this proposition, we have made a systematic study of the flexibility and the variability in leg-length exhibited by isolated triskelions.Triskelions were isolated from bovine brain. Samples in 5mM Tris.HCl and 50% glycerol were nebulized on to freshly cleaved mica, rotary shadowed with platinum at an elevation angle of 8°, and lightly coated with carbon. The specimens were observed in a Philips EM400T electron microscope at a nominal magnification of 36,000x.

In the process of constant renewal of mammalian epidermis, cells divide and move upwards from the basal layer as they embark on a program of terminal differentiation. Cells located higher in the epidermis - the spinous, granular, and cornified layers - represent progressively later steps in this pathway. Commitment to terminal differentiation is accompanied by major changes in gene expression and morphology.Inter alia, large-scale synthesis of several proteins is initiated: these include filaggrin, a protein thought to be responsible for aggregating keratin filaments, and a recently discovered protein called loricrin, which has been implicated as a likely major component of the covalently cross-linked protein lining of the cornified cell envelope. We have used immunoelectron microscopy to investigate the biosynthetic pathways of filaggrin and loricrin.Immediately after sacrifice, skin samples were taken from newborn mice, and diced into blocks of 1-2 mm3. They were then either (i) fixed with 1% glutaraldehyde, 0.2% picric acid, in PBS and embedded in LR White, or (ii) fixed with 1% glutaraldehyde in PBS, and embedded in Lowicryl K4M. Essentially the same conclusions were reached from the experiments with both resins.

The introduction of silver-staining to detect electrophoretically separated proteins in polyacrylamide gels has provided a method that, with the most responsive proteins, is more sensitive by a factor of ∼100 than Coomassie Blue, the most commonly used organic stain. With silver staining, most proteins take on a brownish hue. However, under appropriate conditions, certain proteins have been found to exhibit distinct and vivid colors. Yellow, blue, red and green bands have all been observed. Colorability is a property with considerable analytical potential, in that it may become possible to infer chemical properties of proteins on the basis of their propensities for coloration upon silver-staining. Such information would considerably enhance the analytical capabilities of gel electrophoresis, which for the most part have been restricted to estimates of molecular weights and isoelectric points. To help realize this potential, we have investigated the physical basis of the colorability of proteins.