Interactions of macromolecules with the mammalian cell surface.
The characterisation of fluoresceinphosphatidylethanolamine (FPE) as a real-time indicator of the electrostatic nature of the cell membrane surface is described. The conditions appropriate for the labelling of cell membranes and the implementation of FPE as a tool to monitor the interactions of various proteins and peptides with membranes are outlined. Some complications attributed to the erythrocyte glycocalyx are examined. In addition it is shown using neuraminidase as an example, that some types of enzyme-catalysed reactions on the cell surface may be monitored in real time. It is also shown that information concerning the binding of several proteins such as serum albumin and monoclonal antibodies are accessible with this technique. The albumin in particular is shown to exhibit a saturation of binding, the analysis of which indicates that the dissociation constant for erythrocytes was determined to be 8 microM and for lymphocytes to be almost 3 microM. On the basis of this comparison together with artificial membranes, the membrane protein components of the lymphocyte surface are implicated in the binding of albumin or the erythrocyte membrane proteins reduce the affinity of the cell surface for albumin.
Wall
J
J
Department of Chemistry and Biological Chemistry, University of Essex, Colchester, U.K.
Ayoub
F
F
O'Shea
P
P
D000911:Antibodies, Monoclonal; D001402:B-Lymphocytes / Q000737:chemistry / Q000502:physiology; D002461:Cell Line, Transformed; D002462:Cell Membrane / Q000737:chemistry / Q000502:physiology*; D002478:Cells, Cultured; D004910:Erythrocyte Membrane / Q000737:chemistry / Q000502:physiology*; D005456:Fluorescent Dyes; D006681:HLA-D Antigens / Q000276:immunology; D006801:Humans; D007700:Kinetics; D008564:Membrane Potentials; D009439:Neuraminidase / Q000378:metabolism*; D010712:Phosphatidic Acids; D012794:Sialic Acids / Q000097:blood; D012996:Solutions; D013050:Spectrometry, Fluorescence
D000911:Antibodies, Monoclonal; D005456:Fluorescent Dyes; D006681:HLA-D Antigens; D010712:Phosphatidic Acids; D012794:Sialic Acids; D012996:Solutions; C063389:fluorescein phosphatidylethanolamine thiocarbamide; D009439:Neuraminidase