Novel fluorescent conjugate containing glucose and NBD and its carrier-mediated uptake by tobacco cells

Some compounds that contain glucose groups can be transported across the plasma membrane into the cells through hexose transporters. To test the hypothesis that glucose-conjugated insecticides also have similar uptake and translocation properties, a novel fluorescent conjugate (12) was prepared by conjugating glucose and 7-nitrobenz-2-oxa-1,3-diazole with 4-iodo-1-phenylpyrazoles. Its fluorescence spectra and uptake by suspension-cultured tobacco (Nicotiana tabacum L.cv.) cells were studied. The fluorescence spectra showed long wavelengths with maximum emission at 530nm. After incubating tobacco cell suspensions in 10μM conjugate for 0.5h, green fluorescence of 12 was clearly visible in the cells under fluorescence microscopy. After 2h of incubation, more than 70% of 12 was absorbed. Carbonyl cyanide m-chlorophenylhydrazone, phloridzin and glucose drastically inhibited uptake. In concentration-dependent uptakes, the uptake rate of 12 showed a saturable component and was in accordance with Michaelis-Menten kinetics. The results proved that the glucose moiety can guide 12 into tobacco cells and that hexose transporters mediated the uptake.