Antibacterial activity of cyclo(L-Pro-L-Tyr) and cyclo(D-Pro-L-Tyr) from <i>Streptomyces</i> sp<i>.</i> strain 22-4 against phytopathogenic bacteria

<p>Two bioactive cyclic dipeptides, cyclo(L-Pro-L-Tyr) and cyclo(D-Pro-L-Tyr), were isolated from the culture broth of <i>Streptomyces</i> sp. strain 22-4 and tested against three economically important plant pathogens, <i>Xanthomonas axonopodis</i> pv. citri, <i>Ralstonia solanacearum</i> and <i>Clavibacter michiganensis</i>. Both cyclic dipeptides were active against <i>X. axonopodis</i> pv. citri and <i>R. Solanacearum</i> with MIC of 31.25 <i>μ</i>g/mL<i>.</i> No activity could be observed against <i>C. michiganensis</i>.</p

Impacts of SCIG and DFIG on Voltage Stability in Greater Banjul Area Utility, The Gambia

Wind unpredictability impacts power stability especially, in high demand areas. Voltage instability is not a new phenomenon for utility providers but the impact is greater with the increase integration of renewable energy systems. The existing 1 MW wind farm consists of an aging fixed speed squirrel cage induction generator (SCIG). The SCIG are known to drain huge amount of reactive power from especially weak utility networks such as the one in Gambia. DIgSILENT Powerfactory was used to analyze the impact of low voltage ride through (LVRT) of 1 MW squirrel-cage induction generator (SCIG) and 1 MW doubly-fed induction generator (DFIG) on the GBA utility network. The results showed a reduction in reactive power absorbed by the generators thereby increasing voltage stability

SAXS reveals highly flexible interdomain linkers of tandem acyl carrier protein–thioesterase domains from a fungal non‐reducing polyketide synthase

Menisporopsin A is a fungal bioactive macrocyclic polylactone requiring only reducing (R) and non-reducing (NR) polyketide synthases (PKSs) to guide a series of esterification and cyclolactonization reactions with no structural information pertaining to these PKSs. Here we report the solution characterization of singlet and doublet acyl carrier protein (ACP2 and ACP1-ACP2)-thioesterase (TE) domains from NR-PKS, involved in menisporopsin A biosynthesis. Small angle X-ray scattering (SAXS) studies in combination with homology modelling reveal that these polypeptides adopt a distinctive Beads-on-aString configuration, characterized by the presence of highly flexible interdomain linkers. These models provide a platform for studying domain organization and interdomain interactions in fungal NR-PKSs, which may be of value in directing the design of functionally optimised polyketide scaffolds

52-week efficacy and safety of telbivudine with conditional tenofovir intensification at week 24 in HBeAg-positive chronic Hepatitis B

Background and Aims: The Roadmap concept is a therapeutic framework in chronic hepatitis B for the intensification of nucleoside analogue monotherapy based on early virologic response. The efficacy and safety of this approach applied to telbivudine treatment has not been investigated. Methods: A multinational, phase IV, single-arm open-label study (ClinicalTrials.gov ID NCT00651209) was undertaken in HBeAg-positive, nucleoside-naive adult patients with chronic hepatitis B. Patients received telbivudine (600 mg once-daily) for 24 weeks, after which those with undetectable serum HBV DNA (<300 copies/mL) continued to receive telbivudine alone while those with detectable DNA received telbivudine plus tenofovir (300 mg once-daily). Outcomes were assessed at Week 52. Results: 105 patients commenced telbivudine monotherapy, of whom 100 were included in the efficacy analysis. Fifty-five (55%) had undetectable HBV DNA at Week 24 and continued telbivudine monotherapy; 45 (45%) received tenofovir intensification. At Week 52, the overall proportion of undetectable HBV DNA was 93% (93/100) by last-observation-carried-forward analysis (100% monotherapy group, 84% intensification group) and no virologic breakthroughs had occurred. ALT normalization occurred in 77% (87% monotherapy, 64% intensification), HBeAg clearance in 43% (65% monotherapy, 16% intensification), and HBeAg seroconversion in 39% (62% monotherapy, 11% intensification). Six patients had HBsAg clearance. Myalgia was more common in the monotherapy group (19% versus 7%). No decrease in the mean glomerular filtration rate occurred in either treatment group at Week 52. Conclusions: Telbivudine therapy with tenofovir intensification at Week 24, where indicated by the Roadmap strategy, appears effective and well tolerated for the treatment of chronic hepatitis B. Trial Registration: ClinicalTrials.gov NCT0065120

HLA-Associated Immune Pressure on Gag Protein in CRF01_AE-Infected Individuals and Its Association with Plasma Viral Load

BACKGROUND: The human leukocyte antigen (HLA)-restricted cytotoxic T-lymphocyte (CTL) immune response is one of the major factors determining the genetic diversity of human immunodeficiency virus (HIV). There are few population-based analyses of the amino acid variations associated with the host HLA type and their clinical relevance for the Asian population. Here, we identified HLA-associated polymorphisms in the HIV-1 CRF01_AE Gag protein in infected married couples, and examined the consequences of these HLA-selected mutations after transmission to HLA-unmatched recipients. METHODOLOGY/PRINCIPAL FINDINGS: One hundred sixteen HIV-1-infected couples were recruited at a government hospital in northern Thailand. The 1.7-kb gag gene was amplified and directly sequenced. We identified 56 associations between amino acid variations in Gag and HLA alleles. Of those amino acid variations, 35 (62.5%) were located within or adjacent to regions reported to be HIV-specific CTL epitopes restricted by the relevant HLA. Interestingly, a significant number of HLA-associated amino acid variations appear to be unique to the CRF01_AE-infected Thai population. Variations in the capsid protein (p24) had the strongest associations with the viral load and CD4 cell count. The mutation and reversion rates after transmission to a host with a different HLA environment varied considerably. The p24 T242N variant escape from B57/58 CTL had a significant impact on the HIV-1 viral load of CRF01_AE-infected patients. CONCLUSIONS/SIGNIFICANCE: HLA-associated amino acid mutations and the CTL selection pressures on the p24 antigen appear to have the most significant impact on HIV replication in a CRF01_AE-infected Asian population. HLA-associated mutations with a low reversion rate accumulated as a footprint in this Thai population. The novel HLA-associated mutations identified in this study encourage us to acquire more extensive information about the viral dynamics of HLA-associated amino acid polymorphisms in a given population as effective CTL vaccine targets

Solution Structures of the Acyl Carrier Protein Domain from the Highly Reducing Type I Iterative Polyketide Synthase CalE8

Biosynthesis of the enediyne natural product calicheamicins γ1I in Micromonospora echinospora ssp. calichensis is initiated by the iterative polyketide synthase (PKS) CalE8. Recent studies showed that CalE8 produces highly conjugated polyenes as potential biosynthetic intermediates and thus belongs to a family of highly-reducing (HR) type I iterative PKSs. We have determined the NMR structure of the ACP domain (meACP) of CalE8, which represents the first structure of a HR type I iterative PKS ACP domain. Featured by a distinct hydrophobic patch and a glutamate-residue rich acidic patch, meACP adopts a twisted three-helix bundle structure rather than the canonical four-helix bundle structure. The so-called ‘recognition helix’ (α2) of meACP is less negatively charged than the typical type II ACPs. Although loop-2 exhibits greater conformational mobility than other regions of the protein with a missing short helix that can be observed in most ACPs, two bulky non-polar residues (Met992, Phe996) from loop-2 packed against the hydrophobic protein core seem to restrict large movement of the loop and impede the opening of the hydrophobic pocket for sequestering the acyl chains. NMR studies of the hydroxybutyryl- and octanoyl-meACP confirm that meACP is unable to sequester the hydrophobic chains in a well-defined central cavity. Instead, meACP seems to interact with the octanoyl tail through a distinct hydrophobic patch without involving large conformational change of loop-2. NMR titration study of the interaction between meACP and the cognate thioesterase partner CalE7 further suggests that their interaction is likely through the binding of CalE7 to the meACP-tethered polyene moiety rather than direct specific protein-protein interaction

Prevention of type 2 diabetes and its complications in developing countries: a review.

BACKGROUND: Type 2 diabetes mellitus (T2DM) is a significant global public health problem affecting more than 285 million people worldwide. Over 70% of those with T2DM live in developing countries, and this proportion is increasing annually. Evidence suggests that lifestyle and other nonpharmacological interventions can delay and even prevent the development of T2DM and its complications; however, to date, programs that have been specifically adapted to the needs and circumstances of developing countries have not been well developed or evaluated. PURPOSE: The purpose of this article is to review published studies that evaluate lifestyle and other non-pharmacological interventions aimed at preventing T2DM and its complications in developing countries. METHODS: We undertook an electronic search of MEDLINE, PubMed, and EMBASE with the English language restriction and published until 30 September 2009. RESULTS: Nine relevant publications from seven studies were identified. The reported interventions predominantly used counseling and educational methods to improve diet and physical activity levels. Each intervention was found to be effective in reducing the risk of developing T2DM in people with impaired glucose tolerance, and improving glycemic control in people with T2DM. CONCLUSIONS: The current evidence concerning the prevention of T2DM and its complications in developing countries has shown reasonably consistent and positive results; however, the small number of studies creates some significant limitations. More research is needed to evaluate the benefits of low-cost screening tools, as well as the efficacy, cost-effectiveness, and sustainability of culturally appropriate interventions in such countries

A conserved motif flags acyl carrier proteins for β-branching in polyketide synthesis

Type I PKSs often utilise programmed β-branching, via enzymes of an “HMG-CoA synthase (HCS) cassette”, to incorporate various side chains at the second carbon from the terminal carboxylic acid of growing polyketide backbones. We identified a strong sequence motif in Acyl Carrier Proteins (ACPs) where β-branching is known. Substituting ACPs confirmed a correlation of ACP type with β-branching specificity. While these ACPs often occur in tandem, NMR analysis of tandem β-branching ACPs indicated no ACP-ACP synergistic effects and revealed that the conserved sequence motif forms an internal core rather than an exposed patch. Modelling and mutagenesis identified ACP Helix III as a probable anchor point of the ACP-HCS complex whose position is determined by the core. Mutating the core affects ACP functionality while ACP-HCS interface substitutions modulate system specificity. Our method for predicting β-carbon branching expands the potential for engineering novel polyketides and lays a basis for determining specificity rules