Highly selective Off-On fluorescent probe for histidine and its imaging in living cells

A naphthalimide-based fluorescent probe CP has been synthesized with simple steps. It can selectively and sensitively recognize copper ions (Cu2+) in HEPES buffer (50 mM, pH 7.2). The fluorescence intensity of CP is linearly proportional to the concentration of Cu2+ ranging from 0-8.3 mu M (correlation coefficient R-2=0.9808). The resulted complex CP@Cu can serve as a turn-on fluorescent probe for the detection of histidine and histidine rich proteins in broad pH application range. Upon the addition of histidine, the fluorescence intensity of CP@Cu exhibits a linear correlation with the concentration of histidine ranging from 0-200 mu M (correlation coefficient R-2=0.9912). Moreover, CP@Cu has potential for imaging histidine in vitro experiments and has promise in real sample applications with great validity. (C) 2014 Elsevier B.V. All rights reserved.