Cooperativity in bimetallic glutathione complexes

A sensitive electrochemical sensor for glutathione based on specific recognition induced collapse of silver-contained metal organic frameworks

An electrochemical sensor capable of detecting glutathione (GSH) with high sensitivity and selectivity was developed based on the unique novel electroactive silver-based metal organic framework (Ag-MOF). The Ag-MOF obtained by silver nitrate and 1,3,5-benzoic acid (H3BTC) was thoroughly characterized and was modified onto the electrode via facile drop-casting method. The electrochemical response of GSH on the Ag-MOF modified electrode showed a significant reduction in the current signal because the Ag-GSH complex had stronger specific affinity than Ag-H3BTC and resulted in the collapse of the Ag-MOF. This sensor demonstrated an extensive linear dynamic range of 0.1 nM-1 µM, along with the low detection limit of 0.018 nM. Additionally, it exhibited good reproducibility, stability, and resistance to interfering compounds. The Ag-MOF modified electrode demonstrated superior performance attributed to its rapid electron transfer rate, outstanding electrochemical redox activity, and specific recognition/competitive reaction. These factors improved both sensitivity and selectivity. The high anti-interference ability allowed for the selective detection of GSH in intricate surroundings. In the real sample testing, the RSD was lower than 3.1% and the recovery was between 98.1 and 103%. This research highlights the potential of Ag-MOFs in developing electrochemical sensors and their promising applications in determining GSH for food screening and early disease diagnosis.

Theoretical insight into the solvent effect of H2O and formamide on the cooperativity effect in HMX complex

The cooperativity effects of the H-bonding interactions in HMX (1,3,5,7-tetranitro-1,3,5,7-tetrazacyclooctane)∙∙∙HMX∙∙∙FA (formamide), HMX∙∙∙HMX∙∙∙H₂O and HMX∙∙∙HMX∙∙∙HMX complexes involving the chair and chair-chair HMX are investigated by using the ONIOM2 (CAM-B3LYP/6-31++G(d,p):PM3) and ONIOM2 (M06-2X/6-31++G(d,p):PM3) methods. The solvent effect of FA or H₂O on the cooperativity effect in HMX∙∙∙HMX∙∙∙HMX are evaluated by the integral equation formalism polarized continuum model. The results show that the cooperativity and anti-cooperativity effects are not notable in all the systems. Although the effect of solvation on the binding energy of ternary system HMX∙∙∙HMX∙∙∙HMX is not large, that on the cooperativity of H-bonds is notable, which leads to the mutually strengthened H-bonding interaction in solution. This is perhaps the reason for the formation of different conformation of HMX in different solvent. Surface electrostatic potential and reduced density gradient are used to reveal the nature of the solvent effect on cooperativity effect in HMX∙∙∙HMX∙∙∙HMX. Graphical abstract RDG isosurface and electrostatic potential surface of HMX∙∙∙HMX∙∙∙HMX.