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 outli ned. Some complications attributed to the erythrocyte glycocalyx are e xamined. In addition it is shown using neuraminidase as an example, th at 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 a ntibodies are accessible with this technique, The albumin in particula r is shown to exhibit a saturation of binding, the analysis of which i ndicates that the dissociation constant for erythrocytes was determine d to be 8 mu M and for lymphocytes to be almost 3 mu M. On the basis o f this comparison together with artificial membranes, the membrane pro tein components of the lymphocyte surface are implicated in the bindin g of albumin or the erythrocyte membrane proteins reduce the affinity of the cell surface for albumin.