Pulse fluorimetry of N-(1-pyrenesulfonyl)dipalmitoyl-L-alpha-phosphatidylethanolamine in concanavalin A-stimulated human lymphocytes.

Human peripheral lymphocytes were cultured with a fluorescent probe, N-(1-pyrenesulfonyl)dipalmitoyl-L-alpha-phosphatidylethanolamine, and with concanavalin A. Fluorescence microscopic observations revealed that in lymphoblasts, pyrenesulfonyl dye was distributed mainly in vacuoles whereas in normal cells cultured without concanavalin A the dye was distributed exclusively in plasma membranes. The fluorescence spectra of the pyrenesulfonyl group incorporated into the cells exhibited two emission maxima, band A (monomer fluorescence of the pyrenesulfonyl group at about 400 nm) and band B (dimer fluorescence of the dye at about 500 nm). The values of the fluorescence lifetime measured at bands A and B indicated that in the absence of concanavalin A, the environment surrounding the pyrenesulfonyl group at the lipid/water interface became more hydrophilic with cultivation time. Concanavalin A made the environment of the interface more hydrophobic than that of lymphocytes cultured without concanavalin A. Fluorescence polarization measured at band A revealed that the mobility of pyrenesulfonyl monomers at the aqueous interface of the membranes was reduced upon concanavalin A stimulation.