CONJUGATES OF FLUORESCEIN AND SAENTA (5'-S-(2-AMINOETHYL)-N-6-(4-NITROBENZYL)-5'-THIOADENOSINE) - FLOW-CYTOMETRY PROBES FOR THE ES NUCLEOSIDE TRANSPORTER ELEMENTS OF THE PLASMA-MEMBRANE

SAENTA was linked to the C-5 or C-6 positions of fluorescein through several structures to form conjugates that were bound tightly to plasma membrane sites associated with es nucleoside transport activity. The conjugates imparted fluorescence to cells that expressed es nucleoside transport activity and served as es-selective plasma membrane stains suitable for flow cytometry. Prior treatment of es-expressing cells with nitrobenzylthioinosine prevented fluorescent staining with the conjugates. Seven SAENTA-fluorescein conjugates served as now cytometric stains with high affinities for es sites, despite substantial differences in the SAENTA-fluorescein linkage structures.