The in vitro study of interaction between antacids and anti-diabetic drug sitagliptin in the treatment of type II diabetes.

Hyperglycemia is a long-lasting syndrome that occurs either when the pancreas cannot produce enough insulin, or the body cannot effectively utilize that insulin to regulate blood sugar levels. Non-insulin-dependent hyperglycemia, also known as type II diabetes, causes a common consequence of severe damage to many of the body's organs mainly the blood vessels and nerves. The majority of people around the world are suffering from non-insulin-dependent diabetes. The present work showed a great effort to investigate any possible interaction between antacids and sitagliptin (anti-diabetic drug) in the treatment of type II diabetes with gastrointestinal tract problems. The in vitro studies were carried out in simulated gastric juice pH 2.0 and intestinal pH 7.4 at 37oC. MgCO3, NaHCO3, Mg(OH)2, Al(OH)3 and CaCO3 were used as antacids in these studies. It has been observed that % release of sitagliptin was significantly enhanced in the presence of calcium carbonate and magnesium carbonates.

The LC-QTOF-MS/MS analysis of acid degradation products of Rifaximin, an antibiotic.

The present research aims to propose a simple and accurate technique for the analysis of Rifaximin in the presence of its stress degradation products and analysis of degradation products by LC-MS/MS analysis. Rifaximin was submitted to forced degradation under the acid hydrolysis condition as prescribed by the ICH. The extract was prepared by firstly treated with HCl and heated about 4 to 8 h. The filtrate was collected and separated using dichloromethane followed by evaporation in rotary evaporator to obtain a solid crude extract which was then stored under refrigeration at -80 °C. Liquid chromatography quadrupole time-of-flight mass spectrometry (LC-QTOF-MS/MS) was utilized to identify products in the drug sample. The data processing results revealed the presence of 9 products in the degraded sample of Rifaximin. This data article contains the m/z [M + H +] values, molecular formula, retention times and the comprehensive list of m/z values detected during the LC- QTOF- MS/MS analysis.

Molecular Determinants Conferring the Stoichiometric-Dependent Activity of α-Conotoxins at the Human α9α10 Nicotinic Acetylcholine Receptor Subtype.

α9α10 nicotinic acetylcholine receptors (nAChRs) putatively exist at different stoichiometries. We systematically investigated the molecular determinants of α-conotoxins Vc1.1, RgIA#, and PeIA inhibition at hypothetical stoichiometries of the human α9α10 nAChR. Our results suggest that only Vc1.1 exhibits stoichiometric-dependent inhibition at the α9α10 nAChR. The hydrogen bond between N154 of α9 and D11 of Vc1.1 at the α9(+)-α9(-) interface is responsible for the stoichiometric-dependent potency of Vc1.1.

Exploring the binding energy profiles of full agonists, partial agonists, and antagonists of the α7 nicotinic acetylcholine receptor.

Nicotinic acetylcholine receptors (nAChRs) belong to the Cys-loop receptor family and are important drug targets for the treatment of neurological diseases. However, the precise determinants of the binding efficacies of ligands for these receptors are unclear. Therefore, in this study, the binding energy profiles of various ligands (full agonists, partial agonists, and antagonists) were quantified by docking those ligands with structural ensembles of the α7 nAChR exhibiting different degrees of C-loop closure. This approximate treatment of interactions suggested that full agonists, partial agonists, and antagonists of the α7 nAChR possess distinctive binding energy profiles. Results from docking revealed that ligand binding efficacy may be related to the capacity of the ligand to stabilize conformational states with a closed C loop.

Role of CysI-CysIII Disulfide Bond on the Structure and Activity of α-Conotoxins at Human Neuronal Nicotinic Acetylcholine Receptors.

α-Conotoxins preferentially antagonize muscle and neuronal nicotinic acetylcholine receptors (nAChRs). Native α-conotoxins have two disulfide links, CI-CIII and CII-CIV, and owing to the inherent properties of disulfide bonds, α-conotoxins have been systematically engineered to improve their chemical and biological properties. In this study, we explored the possibility of simplifying the disulfide framework of α-conotoxins Vc1.1, BuIA, ImI, and AuIB, by introducing [C2H,C8F] modification to the CI-CIII bond. We therefore explored the possibility of using hydrophobic packing of standard amino acid side chains to replace disulfide bonds as an alternative strategy to nonnatural amino acid cross-links. The impact of CI-CIII disulfide bond replacement on the conformation of the α-conotoxins was investigated using molecular dynamics (MD) simulations and nuclear magnetic resonance chemical shift index study. Two-electrode voltage clamp techniques and MD simulations were used to study the impact of disulfide bond deletion on the activities of the peptides at human neuronal nAChRs. All disulfide-deleted variants except ImI[C2H,C8F] had reduced potency for inhibiting nAChRs. Our results suggest that the CI-CIII disulfide bond is important to stabilize the secondary structure of α-conotoxins as well as their interaction with neuronal nAChR targets. Results from this study enrich our understanding of the function of the CI-CIII disulfide bond and are useful in guiding future structural engineering of the α-conotoxins.

Investigation of α-conotoxin unbinding using umbrella sampling.

α-Conotoxins, a class of short and disulfide rich peptide toxins, specifically and potently block nicotinic acetylcholine receptors (nAChRs). In this study umbrella sampling was performed to study the unbinding pathways and potential of mean force (PMF) of α-conotoxin ImI and PNIA(A10L,D14K). Our results suggest that (i) the unbinding pathways of ImI and PNIA(A10L,D14K) are similar despite of their different disulfide framework and structure, and (ii) α-conotoxin unbinding requires large conformation perturbation of the C-loop and the backbone flexibility of the C-loop can affect the binding or unbinding kinetics of the α-conotoxins. In addition, (iii) umbrella sampling gave correct ranking of the binding affinities of ImI and PNIA(A10L,D14K) indicating its efficacy on prediction of the binding affinities of α-conotoxins and implicating its potential application in design of more potent α-conotoxin analogs.