Abstract
A fluorescein derivative, sensor 1, was synthesized and characterized. It shows 50nm bathochromic shifts (from 346 to 400nm) with a change of solution color and a large increase in the fluorescence intensity upon binding zinc in 1:1 ethanol–hydroxyethyl piperazine ethanesulfonic acid buffer (v/v, pH 7.2) solution. It was demonstrated that changes are not due to the ring opening of the fluorescein spirolactam. The formation of 1–Zn2+ complex or fluorescein dianion adduct at higher pH was further confirmed by mass spectrometry. The fluorescein based molecular probe showed Zn2+ induced absorption and emission changes but does not undergo spirolactam ring opening (reversible) whereas ring opening (irreversible) and hydrolysis take place in alkaline pH region. Confocal microscopy experiments showed that 1 can be used for detection of Zn2+ levels (∼30μM) within living cells.
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