16 research outputs found

    Variations in the SDN Loop of Class A Beta-Lactamases: A Study of the Molecular Mechanism of BlaC (Mycobacterium tuberculosis) to Alter the Stability and Catalytic Activity Towards Antibiotic Resistance of MBIs

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    The emergence of multidrug-resistant (MDR) and extensively drug-resistant (XDR) tuberculosis calls for an immediate search for novel treatment strategies. Recently, BlaC, the principal beta-lactamase of Mycobacterium tuberculosis, was recognized as a potential therapeutic target. BlaC belongs to Ambler class A, which is generally susceptible to the beta-lactamase inhibitors currently used in clinics: tazobactam, sulbactam, and clavulanate. Alterations at Ser130 in conserved SDN loop confer resistance to mechanism-based inhibitors (MBIs) commonly observed in various clinical isolates. The absence of clinical evidence of S130G conversion in M. tuberculosis draws our attention to build laboratory mutants of S130G and S130A of BlaC. The study involving steady state, inhibition kinetics, and fluorescence microscopy shows the emergence of resistance against MBIs to the mutants expressing S130G and S130A. To understand the molecular reasoning behind the unavailability of such mutation in real life, we have used circular dichroism (CD) spectroscopy, differential scanning calorimetry (DSC), molecular dynamics (MD) simulation, and stability-based enzyme activity to compare the stability and dynamic behaviors of native and S130G/A mutant form of BlaC. A significant decrease in melting temperature (BlaC T M 60°C, S130A T M 50°C, and S130G T M 45°C), kinetic instability at higher temperature, and comparative dynamic instability correlate the fact that resistance to beta-lactam/beta-lactamase inhibitor combinations will likely not arise from the structural alteration of BlaC, therefore establishing confidence that this therapeutic modality can be potentially applied as a part of a successful treatment regimen against M. tuberculosis

    Infrastructure in India: The economics of transition from public to private provision

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    Indian infrastructure is in a state of flux. The provisioning of infrastructure services in India is steadily moving away from the realm of government to that of private sector. The critical issue has been getting economic structures right; in those sectors where there has been a recognition (and systemic implementation) of the principles of appropriate market structures, competition, and measured regulatory oversight, development has been rapid. The outcomes have varied by sector, with Indian telecom providing services that are globally cost-effective and electricity remaining a nightmare for consumers and a major bottleneck for India's continuing growth. While a few ports have significantly increased their efficiency, the ports sector overall remains behind international benchmarks. The initial remarkable spurt in the National Highways Development Project enabled (and probably to an extent, fuelled) growth, and brought in some of India's most innovative policy responses, but there has been a slowdown in momentum in expanding the programme. In recent years, there has simply not been the requisite (political) commitment to ownership of the innovation and motivation that is needed to sustain the pace of reform in key infrastructure sectors.Infrastructure Risk Market structure Regulation

    Biogeochemical Controls on the Release and Accumulation of Mn and As in Shallow Aquifers, West Bengal, India

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    HIGHLIGHTSManganese and arsenic concentrations are elevated in Murshidabad groundwater.Manganese release appears to be independent of dissolved organic matter quality.Mineral precipitation and dissolution reactions impact fate of manganese.Arsenic concentrations are related to dissolved organic matter quantity and quality.The prevalence of manganese (Mn) in Southeast Asian drinking water has recently become a topic of discussion, particularly when concurrent with elevated arsenic (As). Although Mn groundwater geochemistry has been studied, the link between dissolved organic matter (DOM) quality and Mn release is less understood. This work evaluates characteristics of DOM, redox chemistry, and the distribution of Mn within Murshidabad, West Bengal, India. Shallow aquifer samples were analyzed for cations, anions, dissolved organic carbon, and DOM properties using 3-dimensional fluorescence excitation emission matrices followed by parallel factor modeling analyses. Two biogeochemical regimes are apparent, separated geographically by the river Bhagirathi. East of the river, where Eh and nitrate (NO3−) values are low, humic-like DOM coexists with high dissolved Mn, As, and Fe. West of the river, lower dissolved As and Fe concentrations are coupled with more protein-like DOM and higher NO3− and Eh values. Dissolved Mn concentrations are elevated in both regions. Based on the distribution of available electron acceptors, it is hypothesized that groundwater east of the Bhagirathi, which is more reducing and enriched in dissolved Fe and Mn but depleted in NO3−, is chemically dominated by Mn(IV)/Fe(III) reduction processes. West of the river where NO3− is abundant yet dissolved Fe is absent, NO3− and Mn(IV) likely buffer redox conditions such that Eh values are not sufficiently reducing to release Fe into the dissolved phase. The co-occurrence of humic-like DOM with dissolved As, Fe, and Mn in the more reducing aquifers may reflect complex formation between humic DOM and metals, as well as electron shuttling processes involving humic DOM, which may enhance metal(loid) release. Saturation indices of rhodochrosite (MnCO3) suggest that precipitation is thermodynamically favorable in a greater proportion of the more reducing sites, however humic DOM–Mn complexes may be inhibiting MnCO3 precipitation. Where dissolved arsenic concentrations are low, it is postulated that Mn(IV) reduction is oxidizing As(III) to As(V), increasing the potential for re-adsorption of As(V) onto relatively stable, un-reduced or newly precipitated Fe-oxides. Manganese release appears to be independent of DOM quality, as it persists in both humic and protein-like DOM environments
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