Analytical Sciences

Abstract − Analytical Sciences, 32(8), 887 (2016).

A Label-free, Highly Sensitive and Selective Detection of Hemin Based on the Competition between Hemin and Protoporphyrin IX Binding to G-Quadruplexes
Bei Hua KANG, Na LI, Shi Gang LIU, Nian Bing LI, and Hong Qun LUO
Key Laboratory of Eco-Environments in Three Gorges Reservoir Region (Ministry of Education), School of Chemistry and Chemical Engineering, Southwest University, Chongqing 400715, China
Herein is reported a simple and label-free fluorescent detection method for hemin based on using protoporphyrin IX (PPIX) as a fluorescent signal reporter. PPIX emits weak fluorescence in an aqueous solution. When PPIX binds to G-quadruplexes, the fluorescence intensity of PPIX is greatly increased. While in the presence of target hemin, hemin competes with PPIX toward G-quadruplexes because its affinity to G-quadruplexes is higher than that of PPIX. With the formation of the hemin-G-quadruplex complex, PPIX is released to the solution from the G-quadruplex accompanied by quenching of the fluorescence of the system. This fluorescence change of the system can be used to monitor hemin with a low detection limit of 36 nM. In addition, the possible binding sites for PPIX binding to the G-quadruplex are discussed based on competition between hemin and PPIX. What is more, this method might pave the way for applying G-quadruplexes and PPIX to more sensing systems.