Changes in membrane fluidity induced by binding of immunoglobulins to sperm Fc receptors.

Receptors for Fc region of immunoglobulins (FcR) are reported to be present on spermatozoa, and also detected in seminal plasma, however their function is still not known. Since various changes in sperm membrane architecture during maturation and passage through female genital tract are reported, experiments were conducted to study the membrane fluidity changes in sperm subsequent to ligation of surface FcR with immunoglobulin and its derivatives. This paper reports that interaction with IgG restricts rotational mobility of cell surface proteins and membrane lipids as studied by EPR spectroscopy using spin probes. Decrease in fluidity was much more pronounced in the presence of aggregated IgG due to crosslinking of sperm FcR by aggregated IgG.

Characterization of a lectin from goat peripheral blood lymphocytes.

A D-glucose specific lectin was isolated from goat peripheral blood lymphocytes by affinity chromatography on N-acetyl D-glucosamine agarose gel. The fluorescence intensity of 4 methyl umbelliferyl D-glucose was quenched to about 62% on addition of the lectin. This lectin gave a single band corresponding to 112 kDa in SDS-PAGE irrespective of treatment with 2-mercaptoethanol. The molecular weight and the Stoke's radius of the lectin in the native conditions were found to be 114 kDa and 4.54 nm, respectively, as determined by gel filtration on Sephacryl S 500 column. The lectin was found to be a glycoprotein with 5.6% of neutral hexose content and 5.5% of sialic acid. The lectin agglutinated trypsinized rabbit erythrocytes and human type A erythrocytes. The hemagglutinating activity was dependent on the presence of divalent cations like Mn2+ and Ca2+. Optimum pH, ionic strength and temperature for rebinding of lectin to acid treated Sephadex G200 were found to be 7.5, 0.16 and 30-37 degrees C, respectively.

Carbohydrate induced modulation of cell membrane. IV: Interaction with mucin and fucoidan totally immobilizes the human platelet membrane.

P selectins and E selectins are cell adhesion molecules that mediate the interaction of platelets and endothelial cells with neutrophils and monocytes. The proposed ligands for these receptors contain the Le(x) core, sialic acid and sulfated fucose. In this paper we report that binding of sialic acid markedly restricts the mobility of membrane proteins and lipids as studied by EPR spectroscopy using spin probes. Binding of mucin and fucoidan totally restricts the mobility probably due to cross-linking of the surface lectins. Binding of these ligands also resulted in an increase in the cytoplasmic viscosity.

Carbohydrate induced modulation of cell membrane. V : ESR characterization of molecular mobility in lipid bilayer of human neutrophil plasma membrane.

Physiological changes in neutrophils after binding of sialic acid, mucin and fucoidan have been investigated using spin probes. Binding of sialic acid markedly reduces the mobility of neutrophil membrane proteins and lipids. Binding of mucin and fucoidan totally restricts the mobility probably due to cross linking of the surface lectins. Binding of these ligands also resulted in an increase in the cytoplasmic viscosity.