QUANTUM-DYE LABELED PROTEINS FOR GLYCOBIOLOGY - A VIABLE NONRADIOACTIVE ALTERNATIVE TRACER

Quantum dye (QD), a macrocyclic europium-chelate, developed as a cytol ogical marker, has never been used for quantitative applications. It w ould be ideal, however, if the same tracer can be used for both qualit ative and quantitative purposes. We have labeled some lectins and neog lycoproteins with QD for the purpose of quantitative analyses in glyco biology, and tested its suitability in three different areas in glycob iology: (1) glycosyltransferase, (2) an animal lectin mannose-binding protein, and (3) the Gal/GalNAc receptor of rat liver membrane. Useful ness of QD-labeled lectins was amply demonstrated by the quantificatio n of galactosyltransferase activity using QD-soybean agglutinin and QD -RCA120 (Ricinus communis agglutinin), We also showed that QD-labeled neoglycoproteins, QD-Man-BSA and QD-Gal-BSA, can replace radioiodinate d counterparts in the binding assays of animal lectins (serum mannose binding protein and hepatic Gal/GalNAc receptor.) The advantage of QD and other europium labels is that it does not decay as radioiodides do . The long shelf-life results in more consistent results from repeated experiments.