Conformational analysis of the endogenous μ-opioid agonist endomorphin-1 using NMR spectroscopy and molecular modeling

AbstractEndomorphin-1 (Tyr-Pro-Trp-Phe-NH2) is a highly selective and potent agonist of the μ-opioid receptor. To identify structural attributes unique to this opioid peptide and potential sites of recognition, a conformational analysis has been performed using multidimensional NMR and molecular modeling techniques. The spectroscopic results, derived from experiments in both DMSO and water, indicate that endomorphin-1 exists in the cis- and trans-configuration with respect to the Pro-omega bond in approximately 25% and 75% populations, respectively. In DMSO, the cis-configuration adopts a compact sandwich conformation in which the Tyr and Trp aromatic rings pack against the proline ring, whereas the trans-configuration adopts an extended conformation. Although non-random structure was not observed in water, condensed phase molecular dynamics calculations indicate that trans-isomers dominate the population in this higher dielectric medium. Structural comparison of the cis- and trans-configurations with morphine and selective μ-peptide ligands PL-017 and d-TIPP, as well as the δ-selective peptide ligands TIPP (δ-antagonist, μ-agonist) and DPDPE were also performed and suggest the trans-isomer is likely the bioactive form. A hypothesis is proposed to explain μ- and δ-selectivity based on the presence of spatially distinct selectivity pockets among these ligands

Initial Validation of Brief Measures of Suicide Risk Factors: Common Data Elements used by the Military Suicide Research Consortium.

The Military Suicide Research Consortium (MSRC) developed a 57-item questionnaire assessing suicide risk factors, referred to as the Common Data Elements (CDEs), in order to facilitate data sharing and improve collaboration across independent studies. All studies funded by MSRC are required to include the CDEs in their assessment protocol. The CDEs include shortened measures of the following: current and past suicide risk, lethality and intent of past suicide attempts, hopelessness, thwarted belongingness, anxiety sensitivity, posttraumatic stress disorder symptoms, traumatic brain injury, insomnia, and alcohol abuse. This study aimed to evaluate the psychometric properties of the CDE items drawn from empirically validated measures. Exploratory factor analysis was used to examine the overall structure of the CDE items, and confirmatory factor analyses were used to evaluate the distinct properties of each scale. Internal consistencies of the CDE scales and correlations with full measures were also examined. Merged data from 3,140 participants (81.0% military service members, 75.6% male) across 19 MSRC-funded studies were used in analyses. Results indicated that all measures exhibited adequate internal consistency, and all CDE shortened measures were significantly correlated with the corresponding full measures with moderate to strong effect sizes. Factor analyses indicated that the shortened CDE measures performed well in comparison with the full measures. Overall, our findings suggest that the CDEs are not only brief but also provide psychometrically valid scores when assessing suicide risk and related factors that may be used in future research

Post-exercise muscle glycogen synthesis with glucose, galactose and combined galactose-glucose ingestion

Ingested galactose can enhance post-exercise liver glycogen repletion when combined with glucose but effects on muscle glycogen synthesis are unknown. In this double-blind randomised study participants (7 men, 2 women; VO2max: 51.1 (8.7) ml·kg-1·min-1) completed 3 trials of exhaustive cycling exercise followed by a 4-h recovery period, during which carbohydrates were ingested at the rate of 1.2 g·kg-1·h-1 comprising glucose (GLU), galactose (GAL) or galactose+glucose (GAL+GLU; 1:2 ratio). The increase in vastus lateralis skeletal-muscle glycogen concentration during recovery was higher with GLU relative to GAL+GLU (contrast: +50 mmol∙(kg DM)-1; 95%CL 10, 89; p=0.021) and GAL (+46 mmol∙(kg DM)-1; 95%CL 8, 84; p=0.024) with no difference between GAL+GLU and GAL (-3 mmol∙(kg DM)-1; 95%CL -44, 37; p=0.843). Plasma glucose concentration with GLU was not significantly different vs GAL+GLU (+0.41 mmol∙L-1; 95%CL -0.13, 0.94) but was significantly lower in GAL (-1.16 mmol∙L-1; 95%CL -0.53, -1.80) and lower in GAL vs GLU (-0.75 mmol∙L-1; 95%CL -1.34, 0.17). Plasma insulin was higher in GLU+GAL and GLU compared to GAL but not different between GLU+GAL and GLU. Plasma galactose concentration was higher in GAL compared to GLU (3.35 mmol∙L-1; 95%CL 3.07, 3.63) and GAL+GLU (3.22 mmol∙L-1; 95%CL 3.54, 2.90) with no difference between GLU+GAL (0.13 mmol∙L-1; 95%CL -0.11, 0.37) and GLU. Compared to galactose or a galactose+glucose blend, glucose feeding was more effective in post-exercise muscle glycogen synthesis. Comparable muscle glycogen synthesis was observed with galactose-glucose co-ingestion and exclusive galactose-only ingestion

Thiazolides as novel antiviral agents. 2. Inhibition of Hepatitis C virus replication

We report the activities of a number of thiazolides [2-hydroxyaroyl-N-(thiazol-2-yl)amides] against hepatitis C virus (HCV) genotypes IA and IB, using replicon assays. The structure–activity relationships (SARs) of thiazolides against HCV are less predictable than against hepatitis B virus (HBV), though an electron-withdrawing group at C(5′) generally correlates with potency. Among the related salicyloylanilides, the m-fluorophenyl analogue was most promising; niclosamide and close analogues suffered from very low solubility and bioavailability. Nitazoxanide (NTZ) 1 has performed well in clinical trials against HCV. We show here that the 5′-Cl analogue 4 has closely comparable in vitro activity and a good cell safety index. By use of support vector analysis, a quantitative structure–activity relationship (QSAR) model was obtained, showing good predictive models for cell safety. We conclude by updating the mode of action of the thiazolides and explain the candidate selection that has led to compound 4 entering preclinical development

Tween-Embedded Microemulsions—Physicochemical and Spectroscopic Analysis for Antitubercular Drugs

The microemulsion composed of oleic acid, phosphate buffer, ethanol, and Tween (20, 40, 60, and 80) has been investigated in the presence of antitubercular drugs of extremely different solubilities, viz. isoniazid (INH), pyrazinamide (PZA), and rifampicin (RIF). The phase behavior showing the realm of existence of microemulsion has been delineated at constant surfactant/co-surfactant ratio (Km = 0.55) with maximum isotropic region resulting in the case of Tween 80. The changes in the microstructure of Tween 80-based microemulsion in the presence of anti-TB drugs have been established using conductivty (σ) and viscosity (η) behavior. The optical microscopic images of the system help in understanding the effect of dilution and presence of drug on the structure of microemulsion. Partition coefficient, particle size analysis, and spectroscopic studies (UV–visible, Fourier transform infrared, and 1H NMR) have been performed to evaluate the location of a drug in the colloidal formulation. To compare the release of RIF, PZA, and INH from Tween 80 formulation, the dissolution studies have been carried out. It shows that the release of drugs follow the order INH>PZA>RIF. The kinetics of the release of drug has been analyzed using the Korsmeyer and Peppas equation. The results have given a fair success to predict that the release of PZA and INH from Tween 80 microemulsion is non-Fickian, whereas RIF is found to follow a Fickian mechanism