Hydrotalcite catalysis in ionic liquid medium: a recyclable reaction system for heterogeneous Knoevenagel and nitroaldol condensation

Knoevenagel condensation proceeds efficiently in recyclable [bmim]PF₆ and [bmim]BF₄ without any catalyst, and hydrotalcites in ionic liquid serve as a safe and recyclable reaction system for both Knoevenagel as well as nitroaldol condensations.     

A new EPR dosimeter based on 2:1 mixture of Li2C2O4:Na2C2O4 for gamma and neutron dosimetry

Electron paramagnetic resonance (EPR) investigations of Li₂C₂O₄, Na₂C₂O₄ mixed in proportion 1:0, 0:1, 1:1, 2:1 and 3:1 were carried out to measure the absorbed dose from photons and thermal neutrons in a mixed radiation field. A single line spectrum of CO₂^? radical anion centered around g=2.0045±0.0005 was obtained in the respective cases on gamma and neutron irradiation. Except Na₂C₂O₄, other mixtures had shown increase in line width on neutron irradiation possibly due to relaxation effects. Of all combinations, the 2:1 mixture is the more sensitive material for gamma and thermal neutrons. Intensity of CO₂^? radical signal in 2:1 Li₂C₂O₄:Na₂C₂O₄ mixture was found to be linear from 0.006 to 11 kGy for gamma and 40–1530 kGy for thermal neutron doses. Radical signal was found to be stable over a period of 300 days with marginal fading of less than 1 percent. Experimental results thus obtained suggest 2:1 Li₂C₂O₄:Na₂C₂O₄ mixture as the potential neutron dosimeter for medium and high dose range.     

Redox-mediated Negative Differential Resistance (NDR) Behavior in Perylenediimide Derivative: A Supramolecular Approach

Deaggregated perylenediimide (PDI) derivatives exhibit exceptionally high quantum yields, photostability and appropriate molecular features for organic electronics. This work demonstrates a metal–dye–metal framework with a large and stable negative differential resistance (NDR) at ambient conditions, built using a supramolecular strategy. The deaggregation achieved through the encapsulation of the bay-substituted phenyl groups of aggregated (l/d )-Phe-PDI dyes by the β-CD macrocyclic host is validated through detailed spectroscopic and imaging techniques. The host–guest interaction resulted in a dramatic enhancement in the emission yield from 0.28 to 0.90. In the thin film deposits, the β-CD/(l/d )-Phe-PDI complex displayed well-connected sheet-like morphology, whereas the uncomplexed (l/d )-Phe-PDI dye remained as scattered lumps. The large and reversible I–V characteristics displaying strong NDR behavior is attributed to the oxidation/reduction processes involving the rigid π-rich PDI core and is stable at least for about six months at ambient conditions, a promising system for organic electronics applications.     

Laser Raman spectroscopic investigations of biodegradable vehicle of active agents eluting LVM 316 stainless steel cardiovascular stents for in vivo degradation characteristics

Laser Raman spectroscopy is an effective tool for the study of biodegradable polymers, which play a vital role in the new developments in coronary implants such as stents. There is much excitement around the potential capabilities of synthetic biodegradable polymers and the effect they will have on the design and function of implanted devices. In the present investigation, heparin‐conjugated biodegradable copolymers were evaluated for their durability as drug‐eluting stent coatings. Laser Raman spectroscopic studies were carried out and spectra recorded and analyzed of explanted stents coated with different amounts of polymer alone, showing the existence of different levels at different quantities of polymer. The polymer was detected on every stent analyzed. On the stents coated with a thick layer of polymer, a firm layer of polymer still existed on the stent. In contrast, this layer was degraded and spread around on the stents coated with only a thin layer of the polymer. This indicates that the polymers used in the stents in the present investigation exhibit acceptable biodegradability. Such polymers can be used as efficient drug carriers, as these materials show good degradation after the stipulated period. Copyright © 2009 John Wiley & Sons, Ltd.     

Degradation of Triclosan under Aerobic, Anoxic, and Anaerobic Conditions

Triclosan (2, 4, 4??-trichloro-2??-hydroxyl diphenyl ether) is a broad-spectrum antimicrobial agent present in a number of house hold consumables. Aerobic and anaerobic enrichment cultures tolerating triclosan were developed and 77 bacterial strains tolerating triclosan at different levels were isolated from different inoculum sources. Biodegradation of triclosan under aerobic, anoxic (denitrifying and sulphate reducing conditions), and anaerobic conditions was studied in batch cultures with isolated pure strains and enrichment consortium developed. Under aerobic conditions, the isolated strains tolerated triclosan up to 1?g/L and degraded the compound in inorganic-mineral-broth and agar media. At 10?mg/L level triclosan, 95?±?1.2% was degraded in 5?days, producing phenol, catechol and 2, 4-dichlorophenol as the degradation products. The strains were able to metabolize triclosan and its degradation products in the presence of monooxygenase inhibitor 1-pentyne. Under anoxic/anaerobic conditions highest degradation (87%) was observed in methanogenic system with acetate as co-substrate and phenol, catechol, and 2, 4-dichlorophenol were among the products. Three of the isolated strains tolerating 1?g/L triclosan were identified as Pseudomonas sp. (BDC 1, 2, and 3).     

G4 Sensing Pyridyl-Thiazole Polyamide Represses c-KIT Expression in Leukemia Cells

Specific sensing and functional tuning of nucleic acid secondary structures remain less explored to date. Herein, we report a thiazole polyamide TPW that binds specifically to c-KIT1 G-quadruplex (G4) with sub-micromolar affinity and ∼1 : 1 stoichiometry and represses c-KIT proto-oncogene expression. TPW shows up to 10-fold increase in fluorescence upon binding with c-KIT1 G4, but shows weak or no quantifiable binding to other G4s and ds26 DNA. TPW can increase the number of G4-specific antibody (BG4) foci and mark G4 structures in cancer cells. Cell-based assays reveal that TPW can efficiently repress c-KIT expression in leukemia cells via a G4-dependent process. Thus, the polyamide can serve as a promising probe for G-quadruplex recognition with the ability to specifically alter c-KIT oncogene expression.     

Emerging Approaches in Fermentative Production of Statins

Microbial metabolites have many important applications in pharmaceutical and health-care industry. The products of microbial origin are usually produced by submerged fermentation. The solid-state fermentation represents an alternative mode of fermentation, which is increasingly being employed as an alternative to submerged fermentation for metabolite production. The prospect of producing high-value product using low-value raw material offers a substantial premium to switch to these technologies. The cost of statins being one major factor, solid-state fermentation with agro-industrial residues as carbon, nitrogen and support matrix, promises to substantially lower the cost of production. Hence, newer approaches are required to exploit the agro-industrial residues for statin production. The development of these technologies offers an opportunity to exploit low-cost substrates without substantial investment in newer production methodologies. The emerging evidence of beneficial effect of statins in applications other than lipid lowering such as in Alzheimer disease, HIV, age-related dementia, and cancer chemotherapy makes it very important to develop methods for economic production of statins.     

Magnetically Recyclable Nano-Fe2O3-Catalyzed Chemoselective Synthesis and Antioxidant Activity of Diethyl (3-((5-Aryl-1H-1,2,4-triazol-3-yl)thio)propyl)phosphonates

An efficient, green, and chemoselective S-alkylation of 5-aryl-1H-1,2,4-triazole-3-thiones with diethyl (3-bromopropyl)phosphonate in water, catalyzed by nano-Fe₂O₃ under ligand- and base-free conditions, is reported. Clean reaction, less expensive catalyst, excellent yields, and easy workup are the advantages of the present method. The catalyst can be easily collected by a magnet and recycled without significant loss in catalytic activity. The newly synthesized compounds were screened for their antioxidant property by using 1,1-diphenyl-2-picrylhydrazyl (DPPH) scavenging assay. The majority of the compounds exhibited good antioxidant activity.