Construction and assessment of reaction models between F1F0-synthase and organotin compounds: molecular docking and quantum calculations

Structure and bonding in triorganotin chlorides: a perspective from energy decomposition analysis

The Sn-Cl chemical bond of four organotin halides (Me₃SnCl, Et₃SnCl, Bu₃SnCl, and Ph₃SnCl) was studied by using relativistic density functional theory in combination with a quantitative energy decomposition analysis to explain the formation of charged species. The σ orbital is the dominant contributor to the stabilization of the Sn-Cl bond, and the π-orbital interactions also have a significant contribution to the stabilization of Ph₃Sn⁺ cation when the aromatic groups are bonded to the tin atom. The aromaticity of the phenyl groups delocalizes the positive charge, donating electrons to tin atom by conjugation. Although Me₃SnCl and Ph₃SnCl are constituted by groups which the size of the substituents is different, the interaction energies obtained with the energy decomposition analysis present similar values, which also occur with the thermodynamic parameters. Graphical abstract Organotin compounds have widely studied as a potential antitumoral agent. The mechanism in triorganotin compounds includes the formation of cation species, R₃Sn⁺. This article studies the influence of the R groups on the rupture of Sn-Cl bond using the fragment analysis and quantitative energy decomposition analysis.

Evaluation of potential flavonoid inhibitors of glyoxalase-I based on virtual screening and in vitro studies

Glyoxalase-I (GLO-I) is a component of the ubiquitous detoxification system involved in the conversion of methylglyoxal (MG) to d-lactate in the glycolytic pathway. MG toxicity arises from its ability to form advanced glycation end products. GLO-I has been reported to be frequently overexpressed in various types of cancer cells. In this study, we performed structure-based virtual screening of focused flavonoids commercial library to identify potential and specific inhibitors of GLO-I. The compounds were ranked based on Glide extra precision docking score and five hits (curcumin, quercetin, morin, naringin and silibinin) were selected on the basis of their interaction with active site amino acid residues of GLO-I. Mixed mode QM/MM calculation was performed on the top-scoring hit to ascertain the role of zinc ion in ligand binding. In addition, the identified hits were subjected to MM/GBSA binding energy prediction, ADME prediction and similarity studies. The hits were tested in vitro for cell viability, and GLO-I inhibition. Naringin (ST072162) was found to be most potent inhibitor of GLO-I among the identified hits with highest glide XP dock score of -14.906. These findings suggest that naringin could be a new scaffold for designing inhibitors against GLO-I with potential application as anticancer agents.

Kinetic characterization of Ca²⁺-ATPase (SERCA1) inhibition by tri-n-butyltin(IV) chloride. A docking conformation proposal

Organotin compounds, such as tri-n-butyltin(IV) chloride (TBT), are widespread toxicants which disrupt different functions in living organisms. TBT interacts with lipid membranes and membrane proteins. The inhibition of the calcium ATPase from sarcoplasmic reticulum membranes by TBT was studied. It was found that the ATPase inhibition could not be reverted in a large time scale; moreover, an excess of TBT over enzyme did not fully inhibit the ATPase activity; therefore, it was concluded that TBT irreversibly inhibits the enzyme, and this inhibition is accompanied by a decrease in the effective TBT concentration. The residual ATP hydrolysis activity was measured at different TBT concentrations with time, and the protective effect of different calcium concentrations on the TBT inhibition was also determined. The simplest kinetic mechanism to successfully explain all the observations and the kinetic behavior was found to be a single irreversible step of the inhibitor binding to the enzyme accompanied with a first-order inhibitor inactivation. A fluorescence study of fluorescein-5-isothiocyanate-labeled enzyme revealed that TBT binding to the enzyme entails a conformational change related to the high- to low-affinity calcium-binding state transition (E1 to E2 transition), resembling the conformational change induced by vanadate linked to the formation of E2 V complex from E1 state. A docking study allowed us to propose a binding pocket for TBT in the membrane region of E1 close to the high-affinity calcium-binding sites, as well as to define the interactions with amino acid residues interfering with calcium sites occupancy.