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101.
NMR spectroscopy was used to characterize the hepatitis C virus (HCV) NS3 protease in a complex with the 24 residue peptide cofactor from NS4A and a boronic acid inhibitor, Ac-Asp-Glu-Val-Val-Pro-boroAlg-OH. Secondary-structure information, NOE constraints between protease and cofactor, and hydrogen-deuterium exchange rates revealed that the cofactor was an integral strand in the N-terminal beta-sheet of the complex as observed in X-ray crystal structures. Based upon chemical-shift perturbations, inhibitor-protein NOEs, and the protonation state of the catalytic histidine, the boronic acid inhibitor was bound in the substrate binding site as a transition state mimic. In the absence of cofactor, the inhibitor had a lower affinity for the protease. Although the inhibitor binds in the same location, differences were observed at the catalytic site of the protease.  相似文献   
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Sulfolipids have recently emerged as promising antiHIV and antitumor therapeutics. These lipids have been found in association with the photosynthetic apparatus in most photoautotrophic organisms. To date there have been no quantitative studies on the effect of environmental factors on the production of sulfolipid. In this study, we present results on the effect of light irradiance on the production of sulfolipids using the cyanobacteriumAnabaena 7120. The cyanobacteria are grown in a 2 L fedbatch photobioreactor at various external-light intensities. Total lipids are extracted using the Folsch procedure and sulfolipids are quantified using thin-layer chromatography and scanning densitometry. We have achieved a maximum of 14 mg sulfolipid/g dry weight of cell. Our results indicate that there are two stages in the specific rate of production of sulfolipids, one in the declining exponential-growth phase of the cells and the other in the light-limited stage of growth.  相似文献   
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Operations research (OR) methodologies in optimization have been extensivelyapplied to problems in different agricultural value chains in recent years. Wetake a critical stock take of such applications to date, and reflect on theircontribution to value chain sustainability and resilience. The stock take showsthat the rate of industry or policy adoption has been limited, partly due to thecomplex interactions across the segments of agricultural value chains, and themathematical representation being different to the way the decision makerunderstands the problem. OR practice in agriculture is also being asked to covergreater spatial scales and engage more stakeholders, and is required to embraceresilience and sustainability objectives. A single-minded focus on optimizingparts of these complex systems without considering the whole system is no longeradequate, and new methods and approaches are required. Complex systems sciencemethods are being applied to analyse the dynamics of complexsocial–ecological systems, and are starting to find a home in industrialsupply chain analysis. We demonstrate how three complex system methods,agent-based modelling, dynamical systems modelling and network analysis, can beapplied to agricultural value chains as a means of gaining insights into systemdynamics under different and dynamic conditions. The relevance and utility of ORin ensuring the success of agricultural value chains into the future willrequire practitioners to understand and model value chains as complex adaptivesystems.  相似文献   
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A VUV absorption spectroscopy facility designed for ultra‐high spectral resolution is in operation as a dedicated branch on the DESIRS beamline at Synchrotron SOLEIL. This branch includes a unique VUV Fourier transform spectrometer (FTS) and a dedicated versatile gas sample chamber. The FTS instrument can cover a large UV–VUV spectral range from 4 to 30 eV, with an ultimate line width of 0.08 cm?1 on a large spectral window, ΔE/E = 7%, over which all spectral features can be acquired in a multiplex way. The performance can be considered to be a middle ground between broadband moderate‐resolution spectrometers based on gratings and ultra‐high‐spectral‐resolution VUV tunable‐laser‐based techniques over very narrow spectral windows. The various available gaseous‐sample‐handling setups, which function over a wide range of pressures and temperatures, and the acquisition methodology are described. A selection of experimental results illustrates the performance and limitations of the FTS‐based facility.  相似文献   
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Several reference materials and associated reference values have been recommended for the purposes of calibration and/or validation of differential scanning calorimetry (DSC). However, issues of available sample purity, reference-property value accuracy, and potential undesired reactions between reference materials and the materials used for sample pans have not been considered sufficiently in some of the recommendations of property values for the materials. These limitations attenuate greatly the usefulness of many of these reference material recommendations. Indeed, the state of uncertainty regarding true reference property values can be shown to be a limiting factor in the uncertainty of measurements made with DSC. NIST has certified the temperatures and enthalpies of fusion of two new Standard Reference Materials, SRMs 2234 and 2235, in order to help alleviate some of the difficulty.  相似文献   
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