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Antibodies against different cytoskeletal proteins were used to study the cytoskeletal organization of human spermatozoa. A positive staining with actin antibodies was seen in both the acrosomal cap region and the principal piece region of the tail. However, no staining was obtained with nitrobenzoxadiazol-phallacidin, suggesting that most of the actin was in the nonpolymerized form. Most of the myosin immunoreactivity was confined to a narrow band in the neck region of spermatozoa. Tubulin was located to the entire tail, whereas vimentin was only seen in a discrete band-like structure encircling the sperm head, apparently coinciding with the equatorial segment region. Surface staining of the spermatozoa with fluorochrome-coupled Helix pomatia agglutinin revealed a similar band-like structure that codistributed with the vimentin-specific staining. Instead, other lectin conjugates used labeled either the acrosomal cap region (peanut and soybean agglutinins), both the acrosomal cap and the postacrosomal region of the head (concanavalin A), or the whole sperm cell surface membrane (wheat germ and lens culinaris agglutinins and ricinus communis agglutinin I). In lectin blotting experiments, the Helix pomatia agglutinin-binding was assigned to a 80,000-mol-wt polypeptide which, together with vimentin, also resisted treatment with Triton X-100.Only the acrosomal cap and the principal piece of the tail were decorated with rabbit and hydridoma antibodies against an immunoanalogue of erythrocyte c~-spectrin (p230). p230 appeared to be the major calmodulin-binding polypeptide in spermatozoa, as shown by a direct overlay assay of electrophoretic blots of spermatozoa with t251-calmodulin.The results indicate that spermatozoa have a highly specialized cytoskeletal organization and that the distribution of actin, spectrin, and vimentin can be correlated with distinct surface specializations of the sperm cells. This suggests that cytoskeleton may regulate the maintenance of these surface assemblies and, hence, affect the spermatozoan function.Mammalian spermatozoa are highly specialized cells which have many unique properties (for a review, see reference 18). The major compartments of a fully developed spermatozoon are the head, containing the nucleus and the sharply demarcated acrosomal and postacrosomal domains, the neck region, and the tail which contains mitochondria in its middle piece (18). The acrosomal region undergoes drastic changes during acrosomal reaction upon contact with the oocyte (18,30,64). These consist of a dissolution of the acrosomal plasma membrane and exposure of the acrosomal sac which subsequently becomes fused with the oocyte membrane (e.g., reference 30).Although the structure and function of spermatozoa have been the subjects of an intensive study during recent years, many aspects of their motility, activation, and membrane THE JOURNAL OF CELL BIOLOGY . VOLUME 99 SEPTEMBER 1984 1083-1091 © The Rockefeller University Press • 0021-9525/84/09/1083/09 $1.00 organization are still poorly unders...

Microfabricated cantilever sensors were used to measure the surface stress induced by protein adsorption onto a gold surface. Two proteins, immoglobulin G (IgG) and albumin (BSA), were studied. The change of surface stress upon adsorption of IgG was found to be compressive, whereas that of BSA was tensile. This difference is elucidated in terms of protein deformation and packing. Most stress change occurs not on adsorption but over very long time scales, up to 12 h, as protein conformational changes occur. The ability to monitor slow protein changes (e.g., from protein denaturing) is a particular strength of the technique.