摘要：

A crowded molecular environment, which is universally observed in biological cells, changes the thermodynamics and kinetics of biochemical reactions compared to bulk solution. Although molecular crowding has received significant attention, a fundamental explanation of the molecular crowding effect based on thermodynamic parameters, including enthalpy (Δ H ) and entropy changes (Δ S ), is insufficient. Herein, the complexation mechanism of zinc ions with quinolinol derivative in a molecular crowding environment was investigated using polyethylene glycol (PEG) based on the changes in Δ H and Δ S . For 1:1 complexation, which is only promoted by the osmotic pressure effect, Δ H and Δ S decreased with increasing PEG concentration ( C PEG ) because the number of dehydration molecules decreased. In the 1:2 complexation system, which is affected by the osmotic pressure and volume exclusion effects, no obvious dependences of Δ H and Δ S on C PEG were observed. This is because the osmotic pressure and volume exclusion effects contributed oppositely to Δ H and Δ S . The results presented herein provide fundamental knowledge for protein-metal interactions, and it is expected that these data will attract the attention of many physical chemists and biochemists.

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