Nitroarenes are less preferred in drug discovery due to their potential to be mutagenic. However, several nitroarenes were shown to be promising antitubercular agents with specific modes of action, namely, nitroimidazoles and benzothiazinones. The nitro group in these compounds is activated through different mechanisms, both enzymatic and non‐enzymatic, in mycobacteria prior to binding to the target of interest. From a whole‐cell screening program, we identified a novel lead nitrobenzothiazole (BT) series that acts by inhibition of decaprenylphosphoryl‐β‐d ‐ribose 2′‐epimerase (DprE1) of Mycobacterium tuberculosis (Mtb). The lead was found to be mutagenic to start with. Our efforts to mitigate mutagenicity resulted in the identification of 6‐methyl‐7‐nitro‐5‐(trifluoromethyl)‐1,3‐benzothiazoles (cBTs), a novel class of antitubercular agents that are non‐mutagenic and exhibit an improved safety profile. The methyl group ortho to the nitro group decreases the electron affinity of the series, and is hence responsible for the non‐mutagenic nature of these compounds. Additionally, the co‐crystal structure of cBT in complex with Mtb DprE1 established the mode of binding. This investigation led to a new non‐mutagenic antitubercular agent and demonstrates that the mutagenic nature of nitroarenes can be solved by modulation of stereoelectronic properties. 相似文献
Di-block copolymers of poly(ethylene oxide) (PEO) and glycopolymers at three different pendant spacer lengths of glucose moiety were synthesized by deacetylation of pendant moieties of 2,3,4,6-tetra-O-acetyl-d-glucopyranosides which were prepared by reversible addition-fragmentation chain-transfer (RAFT) process. The water soluble deacetylated copolymers, PEO-b-poly(acryl-d-glucopyranoside) (PEO-b-PAG, 2a), PEO-b-poly[4′-(acryloxy)butyl-d-glucopyranoside] (PEO-b-PABG, 2b), and PEO-b-poly[6′-(acryloxy)hexyl-d-glucopyranoside] (PEO-b-PAHG, 2c) were characterized in comparison with acetylated copolymers by spectroscopic and gel permeation chromatography methods. In order to assess the biocompatibility of these three di-block copolymers, the adhesion (%), viability (%), and proliferation assays were carried out in MC3T3 cells in-vitro at different concentrations from 10 nM to 1000 μM. Qualitative analysis of cell cytoskeletal organization was obtained by immunostaining with talin and integrin α5. It was clearly indicative of well spreading of cells in the presence of all glycopolymers at lower concentrations but with an increase in the concentration (10 and 100 μM) showed significant change in the cell surface morphologies, despite having good cell adhesion and viability as compared to the control conditions. The use of di-block glycolpolymers at?≤?100 μM of the concentration showed very good osteoblast cells adhesion and viability response; however at higher concentrations (1000 μM) of glycopolymers > 80% of cells lost their viability. 相似文献
For the synthesis of multisubstituted dispirocyclohexane derivatives, a Rauhut–Currier‐initiated organocascade reaction between 2‐arylideneindan‐1,3‐diones and activated alkenes in the presence of diazabicyclo[2.2.2]octane (DABCO) was demonstrated. The functionalized dispirocyclohexanes with a wide range of substituents were obtained in satisfactory to excellent chemical yields (58–99%) with high chemo‐ and diastereoselectivities (>95:5 dr). This organocatalytic reaction proceeded smoothly through Michael/Michael cyclization, which involves the formation of three new carbon‐carbon bonds with simultaneous construction of two all‐carbon spiro quaternary centers.
With the pervasive generation of information from a wide range of sensors and devices, there always exist a large number of input features in databases, thus complicating machine learning problem formulation. However, certain features are relatively impertinent to specific problems, which may degrade the performances of classifiers in terms of prediction accuracy, sensitivity,specificity, and recall rate. The main goal of a multi-objective optimization problem is to identify the subsets of the given features. To this end, a hybrid cat swarm optimization(HCSO) algorithm is proposed in our paper for performance improvement of the basic cat swarm optimization(CSO) that incorporates guided and competitive inherent characteristics into the original CSO. The performance of HCSO has been tested by finding the optimal feature subset for 15 benchmark datasets. The number of class labels for these datasets varies between 2 and 40. The time complexity analysis of both CSO and HCSO has also been evaluated. Moreover, the performance of the proposed algorithm has been compared with that of simple CSO and other state-ofthe-art techniques. The performances obtained by HCSO have an average 2.68% improvement with a standard deviation of 2.91.The maximum performance improvement is up to 10.09% in prediction accuracy. Tested on the same datasets, CSO has yielded improvements within the range of-7.27% to 8.51% with an average improvement 0.9% and standard deviation 3.96. The statistical tests carried out in the experiments prove that HCSO manifests a moderately better feature selection capacity than that of its counterparts. 相似文献
Manufacture of thermoplastic composites is expensive because of the difficulty of impregnating the resin into the fibers. Powder processing shows great promise as an impregnation technique for cost-effective manufacturing. This paper discusses an electrostatic powder spray impregnation technique that uses glass fibers. A geodesic fiber spreader is used to spread the fibers locally in the region of maximum powder deposition. A negative corona electrostatic spray gun is employed to charge and direct the powder for coating both sides of the spread fiber tow. The process has been used to impregnate glass fibers with poly(aryl ether ketone ketone) powder. The effect of the powder mass flow, corona voltage, and fiber tow velocity on powder deposition has been investigated. Particle image velocimetry is utilized to determine particle velocities. Compression molded panels have been produced and tested in three point bending. 相似文献
Based onin-situ Mössbauer and X-ray diffraction studies, it is shown that in the Fe/TiO2 catalyst, the anatase-rutile transformation of the TiO2 support is facilitated by the Fe2+ ions formed during the reduction. The transformation occurs at lower temperatures in Th/TiO2 and Cu/TiO2 compared to pure TiO2. In general, the transformation of anatase to rutile seems to occur at or below the temperature (770 K) at which strong-metal-support-interaction manifests itself.Contribution No. 718 from the Solid State and Structural Chemistry Unit. 相似文献
This review reports on recent advances in the design of biodegradable polymers built from petroleum and renewable resources using reactive extrusion processing. Reactive extrusion represents a unique tool to manufacture biodegradable polymers upon different types of reactive modification in a cost‐effective way. Partially based on our ongoing research, ring‐opening polymerization of biodegradable polyesters will be approached as well as the chemical modification of biodegradable polymers, particularly natural polymers. The development of environmentally friendly polymer blends as well as (nano)composites from natural polymers, including natural fibers and nanoclays, through reactive extrusion, as an efficient way to improve the interfacial adhesion between these components, will be also discussed.
A general and complete methodology is presented to facilitate systematic modeling and design of polymer processes during the early development period. To capture and handle the subjective type of uncertainty, embedded in the preliminary process development, fuzzy theories are used as a basis to model and design the process in the presence of ambiguity and vagueness. Physical membership functions are developed for mapping the relation between process variables and the associated fuzzy uncertainties. Based on the qualitative results generated using our previously proposed “linguistic based preliminary design method,” the process modeling can be followed even in the absence of any process governing equations. The modeling is carried out by establishing an appropriate fuzzy reasoning system which provides a specific functional mapping that relates input process variables to one (or more than one) output performance parameter(s). A reduced yet feasible domain is generated by our qualitative design scheme to constrain the process variables. Now, any optimization routine can then be employed to search for a proper process design. We demonstrate the effectiveness of the proposed methodology by its application to a typical compression molding process. 相似文献