Investigating effect of mutation on structure and function of G6PD enzyme: a comparative molecular dynamics simulation study.

Several natural mutants of the human G6PD enzyme exist and have been reported. Because the enzymatic activities of many mutants are different from that of the wildtype, the genetic polymorphism of G6PD plays an important role in the synthesis of nucleic acids via ribulose-5-phosphate and formation of reduced NADP in response to oxidative stress. G6PD mutations leading to its deficiency result in the neonatal jaundice and acute hemolytic anemia in human. Herein, we demonstrate the molecular dynamics simulations of the wildtype G6PD and its three mutants to monitor the effect of mutations on dynamics and stability of the protein. These mutants are Chatham (A335T), Nashville (R393H), Alhambra (V394L), among which R393H and V394L lie closer to binding site of structural NADP+. MD analysis including RMSD, RMSF and protein secondary structure revealed that decrease in the stability of mutants is key factor for loss of their activity. The results demonstrated that mutations in the G6PD sequence resulted in altered structural stability and hence functional changes in enzymes. Also, the binding site, of structural NADP+, which is far away from the catalytic site plays an important role in protein stability and folding. Mutation at this site causes changes in structural stability and hence functional deviations in enzyme structure reflecting the importance of structural NADP+ binding site. The calculation of binding free energy by post processing end state method of Molecular Mechanics Poisson Boltzmann SurfaceArea (MM-PBSA) has inferred that ligand binding in wildtype is favorable as compared to mutants which represent destabilised protein structure due to mutation that in turn may hinder the normal physiological function. Exploring individual components of free energy revealed that the van der Waals energy component representing non-polar/hydrophobic energy contribution act as a dominant factor in case of ligand binding. Our study also provides an insight in identifying the key inhibitory site in G6PD and its mutants which can be exploited to use them as a target for developing new inhibitors in rational drug design.

Exploring 3-Benzyloxyflavones as new lead cholinesterase inhibitors: synthesis, structure-activity relationship and molecular modelling simulations.

In this protocol, a series of 3-benzyloxyflavone derivatives have been designed, synthesized, characterized and investigated in vitro as cholinesterase inhibitors. The findings showed that all the synthesized target compounds (1-10) are potent dual inhibitors of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) enzymes with varying IC50 values. In comparison, they are more active against AChE than BChE. Remarkably, amongst the series, the compound 2 was identified as the most active inhibitor of both AChE (IC50 = 0.05 ± 0.01 µM) and BChE (IC50 = 0.09 ± 0.02 µM) relative to the standard Donepezil (IC50 = 0.09 ± 0.01 for AChE and 0.13 ± 0.04 µM for BChE). Moreover, the derivatives 5 (IC50 = 0.07 ± 0.02 µM) and 10 (0.08 ± 0.02 µM) exhibited the highest selective inhibition against AChE as compared to the standard. Preliminary structure-activity relationship was established and thus found that cholinesterase inhibitory activities of these compounds are highly dependent on the nature and position of various substituents on Ring-B of the 3-Benzyloxyflavone scaffolds. In order to find out the nature of binding interactions of the compounds and active sites of the enzymes, molecular docking studies were carried out.[Formula: see text]HIGHLIGHTS3-benzyloxyflavone analogues were designed, synthesized and characterized.The target molecules (1-10) were evaluated for their inhibitory potential against AChE and BChE inhibitory activities.Limited structure-activity relationship was developed based on the different substituent patterns on aryl part.Molecular docking studies were conducted to correlate the in vitro results and to identify possible mode of interactions at the active pocket site of the enzyme.Communicated by Ramaswamy H. Sarma.

Synthesis, characterization and anti-cancer properties of water-soluble bis(PYE) pro-ligands and derived palladium(ii) complexes.

The two cationic palladium(ii) complexes, [Pd(Len)2][OTf]2 (4) and [Pd(Lphen)2][OTf]2 (5), were synthesized by treatment of bis(benzonitrile)dichloropalladium(ii) with [H2Len][OTf]2 (2) or [H2Lphen][OTf]2 (3), respectively, in the presence of a weak base. The pro-ligands 2 and 3 were synthesized by melt reactions between N-methyl-4-chloropyridinium triflate (1) and the amines ethylenediamine or phenylenediamine, respectively. The water-soluble compounds 2-5 were fully characterized, including by single-crystal X-ray crystal structure determinations for 2-4. UV-Vis and fluorescence spectroscopy were used to study the binding interactions of 2-5 with CT-DNA. The spectroscopic data suggested the presence of intercalative and groove binding modes and this was supported by molecular docking studies. The in vitro cytotoxicity studies (IC50 values) showed that the human breast cancer cell lines MCF-7 and T47D were more sensitive towards 3, 4 and 5 than cisplatin. The cytotoxicity of the new compounds decreased in the order 5 > 4 > 3 > 2. Furthermore, the annexin V-FITC staining method strongly suggested the presence of phosphatidylserine (PS) on the outer membrane of the treated cells, which is a hallmark of apoptosis.