Binding Mode Investigations on the Interaction of Lead(II) Acetate with Human Chorionic Gonadotropin Hao Zhang Yang Liu Rui Zhang Rutao Liu Yadong Chen 10.1021/jp505565s.s001 https://acs.figshare.com/articles/journal_contribution/Binding_Mode_Investigations_on_the_Interaction_of_Lead_II_Acetate_with_Human_Chorionic_Gonadotropin/2264830 Lead exposure could induce endocrine disruption and hormonal imbalance of humans, resulting in detrimental effects on the reproductive system even at low doses. However, mechanisms of lead actions remain unknown. This article investigated lead interactions with human chorionic gonadotropin (HCG) as a conceivable mechanism of its reproductive toxicity by spectroscopic technique, isothermal titration calorimetry (ITC), molecular docking study, and enzyme-linked immunosorbent assay (ELISA). Fluorescence measurements showed that lead acetate dynamically quenched intrinsic fluorescence of HCG through collisional mechanism with the association constant (<i>K</i><sub>SV</sub>) in the magnitude of 10<sup>3</sup> L/mol at the detected temperatures (298, 303, and 310 K). ITC and molecular docking results revealed lead acetate could bind into 5 binding sites of HCG through electrostatic effects (<i>Δ<i>H</i></i> < 0, <i>Δ<i>S</i></i> > 0) and hydrophobic forces (<i>Δ<i>H</i></i> > 0, <i>Δ<i>S</i></i> > 0). The conformational investigation of HCG by UV–vis absorption spectroscopy, circular dichroism spectroscopy, and ELISA indicated lead acetate changed the secondary structure of HCG by loosening and destruction of HCG skeleton and increasing the hydrophobicity around Tyr residues and resulted in the decreased bioactivities of HCG. This work presents direct interactions of lead with sex hormones and obtains a possible mechanism on lead induced reproductive toxicity at the molecular level. 2014-08-14 00:00:00 5 binding sites Human Chorionic GonadotropinLead exposure Fluorescence measurements sex hormones Binding Mode Investigations KSV collisional mechanism Tyr residues spectroscopic technique UV titration calorimetry docking study ELISA docking results 310 K ITC dichroism spectroscopy chorionic gonadotropin HCG skeleton acetate