Yan Jia,Peng Li,Wei Song,Guangjiu Zhao,Daoyuan Zheng,Dongmei Li,Yanni Wang,Jiayue Wang,Chunyan Li,Keli Han
S-Adenosylhomocysteine hydrolase (SAHase) is a cellular enzyme that plays a key role in the methylation process, and a potential drug target in the discovery of antiviral and anticancer agents. There is increasing interest in determining its activity in the biological and clinical fields with chemosensors but with limited success so far. Herein, we designed and developed for the first time an off/on-type of fluorogenic substrate (NADE) that is directly responsive to SAHase activity. NADE used 1,8-naphthalimide as the signal reporter and adenosine (Ade) as the reaction center; removal of the Ade moiety enhanced the fluorescence by >10-fold. Kinetic study showed that NADE followed a non-Michaelis–Menten pattern that corresponded to the allosteric behavior of SAHase. NADE showed excellent selectivity and functioned efficiently in cells, allowing the microscopic imaging of SAHase activity. NADE can also be used to identify and measure the effectiveness of inhibitors in a markedly superior way. In a word, NADE would be broadly useful in clinical applications and academic studies.
Shanshan Huang,Xujuan Lv,Yuwei Zhang,Juan Wang,Xueji Zhang,Daoqing Fan
The level alterations of antioxidants are highly associated with various oxidative stress-related diseases, food quality and drug safety problems, which enables the reliable and accurate determination of total antioxidant capacity (TAC) become progressively significant. Herein, for the first time, we explored the catalytic effect of MnSiO 3 nanozyme with oxidase-like activity towards different fluorescent substrates, and introduced ratiometric fluorescence to MnSiO 3 -based biosensing. By harnessing MnSiO 3 -propelled catalytic oxidation of two fluorescent substrates with contrary responses (Scopoletin, SC and o-phenylenediamine, OPD), we constructed a facile, cost-effective ratiometric fluorescent (RF) platform for TAC measurement. In the absence of antioxidants, SC and OPD can be oxidized, and the synergistic effect of fluorescence resonance energy transfer (FRET) and inner-filter-effect (IFE) between SC and oxidized OPD (Ox-OPD) will result in the weak fluorescence of Ox-SC at 465 nm and the strong one of Ox-OPD at 562 nm, respectively. However, the addition of antioxidants will dissociate MnSiO 3 , generating the recovered high/low fluorescence values of both substrates. Through monitoring the FI 465 /FI 562 changes, the RF analysis of different antioxidants (Cys, AA, GSH) with satisfactory sensitivity is performed and the TAC measurements in diverse real samples (human serums, beverages, and drugs) are successfully accomplished. Moreover, the system demonstrates high selectivity and could compete with the commercial TAC test kits.
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