A new chromanone acid from the bark of Calophyllum dryobalanoides

A new chromanone acid, calodryobalanoic acid, along with six known compounds, apetalic acid, isoblancoic acid, lupeol, 1-hydroxy-2-methoxyxanthone, 1,7-dihydroxy-3-methoxyxanthone, and 5,7,4′-trihydroxyflavanone, was isolated from the bark of Calophyllum dryobalanoides collected in Vietnam. The structure of the new compound was elucidated using mainly 1-D and 2-D NMR techniques (¹H and ¹³C NMR, HSQC, HMBC, COSY, and NOESY) and IR spectroscopy. The stereochemistry was determined on the basis of NMR results and DFT calculations.     

Cytotoxic tetraoxygenated xanthones from the bark of Garcinia schomburgkiana

Two new tetraoxygenated xanthones, 6-O-demethyloliverixanthone and schomburgxanthone, together with cowanin, cowanol, fuscaxanthones A and B, 3-isomangostin hydrate, and 1,7-dihydroxyxanthone, were isolated from the bark of Garcinia schomburgkiana. Their structures were elucidated using 1-D and 2-D NMR techniques as well as chemical methods. Five of the isolated compounds were tested regarding their cytotoxicity against HeLa cells and the results showed that fuscaxanthone B and cowanin possessed remarkable activity with IC₅₀ values of 2.4 ± 0.2 and 2.7 ± 0.3 μg/ml, respectively, using an MTT assay.     

Site-specific phosphorylation of protein phosphatase 1 regulatory subunit 12A stimulated or suppressed by insulin

Protein phosphatase 1 (PP1) is one of the major phosphatases responsible for protein dephosphorylation in eukaryotes. So far, only few specific phosphorylation sites of PP1 regulatory subunit 12A (PPP1R12A) have been shown to regulate the PP1 activity. The effect of insulin on PPP1R12A phosphorylation is largely unknown. Utilizing a mass spectrometry based phosphorylation identification and quantification approach, we identified 21 PPP1R12A phosphorylation sites (7 novel sites, including Ser20, Thr22, Thr453, Ser478, Thr671, Ser678, and Ser680) and quantified 16 of them under basal and insulin stimulated conditions in hamster ovary cells overexpressing the insulin receptor (CHO/IR), an insulin sensitive cell model. Insulin stimulated the phosphorylation of PPP1R12A significantly at Ser477, Ser478, Ser507, Ser668, and Ser695, while simultaneously suppressing the phosphorylation of PPP1R12A at Ser509 (more than 2-fold increase or decrease compared to basal). Our data demonstrate that PPP1R12A undergoes insulin stimulated/suppressed phosphorylation, suggesting that PPP1R12A phosphorylation may play a role in insulin signal transduction. The novel PPP1R12A phosphorylation sites as well as the new insulin-responsive phosphorylation sites of PPP1R12A in CHO/IR cells provide targets for investigation of the regulation of PPP1R12A and the PPP1R12A-PP1cδ complex in insulin action and other signaling pathways in other cell models, animal models, and humans.     

Xanthones from the bark of Garcinia pedunculata

Three new xanthones, pedunxanthones A–C (1–3), together with five known compounds, 1,5-dihydroxy-3-methoxy-6′,6′-dimethyl-2H-pyrano(2′,3′:6,7)-4-(3-methylbut-2-enyl)xanthone, 1,5-dihydroxy-3-methoxy-4-(3-methylbut-2-enyl)xanthone, dulxanthone A, garbogiol and oleanolic acid, were obtained from a petroleum ether extract of the bark of Garcinia pedunculata. The new structures were elucidated using spectroscopic methods, mainly 1-D and 2-D NMR.     

Mechanistic insights into the retaining glucosyl-3-phosphoglycerate synthase from mycobacteria

Considerable progress has been made in recent years in our understanding of the structural basis of glycosyl transfer. Yet the nature and relevance of the conformational changes associated with substrate recognition and catalysis remain poorly understood. We have focused on the glucosyl-3-phosphoglycerate synthase (GpgS), a "retaining" enzyme, that initiates the biosynthetic pathway of methylglucose lipopolysaccharides in mycobacteria. Evidence is provided that GpgS displays an unusually broad metal ion specificity for a GT-A enzyme, with Mg(2+), Mn(2+), Ca(2+), Co(2+), and Fe(2+) assisting catalysis. In the crystal structure of the apo-form of GpgS, we have observed that a flexible loop adopts a double conformation L(A) and L(I) in the active site of both monomers of the protein dimer. Notably, the L(A) loop geometry corresponds to an active conformation and is conserved in two other relevant states of the enzyme, namely the GpgS·metal·nucleotide sugar donor and the GpgS·metal·nucleotide·acceptor-bound complexes, indicating that GpgS is intrinsically in a catalytically active conformation. The crystal structure of GpgS in the presence of Mn(2+)·UDP·phosphoglyceric acid revealed an alternate conformation for the nucleotide sugar β-phosphate, which likely occurs upon sugar transfer. Structural, biochemical, and biophysical data point to a crucial role of the β-phosphate in donor and acceptor substrate binding and catalysis. Altogether, our experimental data suggest a model wherein the catalytic site is essentially preformed, with a few conformational changes of lateral chain residues as the protein proceeds along the catalytic cycle. This model of action may be applicable to a broad range of GT-A glycosyltransferases.     

Long-Lasting Insecticidal Hammocks for Controlling Forest Malaria: A Community-Based Trial in a Rural Area of Central Vietnam

Background

In Vietnam, malaria remains a problem in some remote areas located along its international borders and in the central highlands, partly due to the bionomics of the local vector, mainly found in forested areas and less vulnerable to standard control measures. Long Lasting Insecticidal Hammocks (LLIH), a tailored and user-friendly tool for forest workers, may further contribute in reducing the malaria burden. Their effectiveness was tested in a large community-based intervention trial carried out in Ninh Thuan province in Central Vietnam.

Methods and Findings

Thirty villages (population 18,646) were assembled in 20 clusters (1,000 individuals per cluster) that were randomly allocated to either the intervention or control group (no LLIH) after stratification according to the pre-intervention P. falciparum antibody prevalence (<30%; ≥30%). LLIH were distributed to the intervention group in December 2004. For the following 2 years, the incidence of clinical malaria and the prevalence of infection were determined by passive case detection at community level and by bi-annual malariometric surveys. A 2-fold larger effect on malaria incidence in the intervention as compared to the control group was observed. Similarly, malaria prevalence decreased more substantially in the intervention (1.6-fold greater reduction) than in the control group. Both for incidence and prevalence, a stronger and earlier effect of the intervention was observed in the high endemicity stratum. The number of malaria cases and infections averted by the intervention overall was estimated at 10.5 per 1,000 persons and 5.6/100 individuals, respectively, for the last half of 2006. In the high endemicity stratum, the impact was much higher, i.e. 29/1000 malaria cases and 15.7 infections/100 individuals averted.

Conclusions

LLIH reduced malaria incidence and prevalence in this remote and forested area of Central Vietnam. As the targets of the newly-launched Global Malaria Action Plan include the 75% reduction of the global malaria cases by 2015 and eventually the elimination/eradication of malaria in the long term, LLIH may represent an additional tool for reaching such objectives, particularly in high endemicity areas where standard control tools have a modest impact, such as in remote and forested areas of Southeast Asia and possibly South America.

Trial Registration

ClinicalTrials.gov {"type":"clinical-trial","attrs":{"text":"NCT00853281","term_id":"NCT00853281"}}NCT00853281     

Isolation of Pseudomonas stutzeri in wastewater of catfish fish-ponds in the Mekong Delta and its application for wastewater treatment

The aim of this study was to explore the potential for reducing soluble N load in fishpond wastewater using naturally occurring denitrifying bacteria. Twenty-seven isolates were selected from in wastewater (liquid/solid) of catfish-ponds located along the Tien river, in the Mekong Delta, Vietnam in SW-LB medium (artificial seawater Luria-Britani medium) supplemented with 10 mM NH₄ and NO₃ and twenty-five isolates were identified as Pseudomonas stutzeri based on similarity of PCR-16S rRNA using universal primers and specific primers. Four isolates were effective in lowering soluble N (NH₄, NO₂ and NO₃) levels in fishpond water from 10 mg/L to negligible amounts after four days. Further experiments are underway to determine the fate of N lost from solution and the relative activity of ammonia oxidation, and nitrite and nitrate reduction by P. stutzeri isolates.     

Chloro-oxime derivatives as novel small molecule chaperone amplifiers

Chloro-oxime derivatives were investigated as novel small molecule chaperone amplifiers. Lead optimization led to the discovery of compounds that displayed potent HSF1 activation activity, significant cytoprotection in MG-132 stress, ER stress and PolyQ stress cell models (EC₅₀ < 10 μM).     

Phage display screening against a set of targets to establish peptide-based sugar mimetics and molecular docking to predict binding site

A novel selection approach is presented to screen phage display peptide libraries against sets of receptors that share specificity for the same ligand. This strategy was applied to the discovery of glycomimetic peptides. Through these screens, a number of peptide clones were discovered that bind the lectins used in the screen, in a sugar competitive manner. In addition, the majority of the selected peptides demonstrate sugar type mimicry consistent with lectin specificity. Docking studies were conducted to establish whether the mimetic peptides bind to the lectin ConA at the sugar binding site or to a nearby, alternative site shown to bind to YPY-containing peptides previously discovered from single-target screens. Of the three cyclic peptides subjected to computational docking, CNTPLTSRC had the highest predicted affinity and CSRILTAAC demonstrated specificity for the sugar binding site comparable to the natural ligand itself.