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New Substrate (new + substrate)
Selected AbstractsUse of Allenylphosphonates as New Substrates for Phosphane-Catalyzed [3+2] and [4+2] AnnulationsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 22 2008Armen Panossian Abstract The suitability of allenylphosphonates as substrates in phosphane-catalyzed annulation reactions has been investigated. Despite their lower reactivity relative to allenyl esters, allenylphosphonates overall display the anticipated behavior: pyrrolines, tetrahydropyridines, and cyclopentenes bearing phosphoryl functions were obtained from imines, ,,,-unsaturated esters, and enones in Bu3P- or iBu3P-promoted reactions. Enantioselective variants of these cyclization reactions afforded enantiomeric excesses of up to 90,% when phosphepine A2 was used as the chiral catalyst. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] ChemInform Abstract: Use of Allenylphosphonates as New Substrates for Phosphane-Catalyzed [3 + 2] and [4 + 2] Annulations.CHEMINFORM, Issue 48 2008Armen Panossian Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Chemiluminescent assay of alkaline phosphatase using dihydroxyacetone phosphate as substrate detected with lucigeninLUMINESCENCE: THE JOURNAL OF BIOLOGICAL AND CHEMICAL LUMINESCENCE, Issue 1 2002Amane Kokado Abstract A sensitive and simple chemiluminescent assay (CL) for alkaline phosphatase (ALP) using dihydroxyacetone phosphate or its ketal (DHAP or DHAP-ketal) was developed. New substrates were transformed to dihydroxyacetone (DHA) after they were hydrolysed by ALP, which reacts with lucigenin and produces strong chemiluminescence. Under the optimum assay condition, the detection limits were 3.8,×,10,19 and 1.5,×,10,18 moles of ALP, respectively. The coefficients of variation (CV) at each points on the standard curve were 0.8,5.4% and 1.8,7.1% (n,=,6), respectively. The mechanism of lucigenin CL with DHA was investigated by ESR spectrometry using the spin-trapping method. The mechanism was speculated as follows: the O2, generated by the reaction of DHA and O2 in alkaline solution reacts with lucigenin, and then emit light. The proposed CL assay was applied to the enzyme immunoassay of 17,-oestradiol, using ALP as a label enzyme. The measurable range of 17,-oestradiol was 15,4000,pg/mL, and the proposed method was four times more sensitive than the colorimetric assay for ALP by using 4-nitrophenyl phosphate as substrate. Copyright © 2002 John Wiley & Sons, Ltd. [source] Enhanced Fluorescence Microscopic Imaging by Plasmonic Nanostructures: From a 1D Grating to a 2D Nanohole ArrayADVANCED FUNCTIONAL MATERIALS, Issue 6 2010Xiaoqiang Cui Abstract A two-dimensional (2D) plasmonic coupling nanostructure for enhanced fluorescence observation using a microscope is presented. The substrate contained periodically assembled nanohole arrays with a pitch of 400,nm and a depth of 25,nm. In comparison with one-dimensional (1D) gratings, this new substrate presented an excellent surface plasmon coupling ability to illuminate light from all directions. Under an optical microscope, an enhancement in the fluorescence intensity of up to 100 times compared with a plain glass slide was observed. The ability to markedly increase the fluorescence intensity means this technique has great potential for application in biodiagnostics, imaging, sensing, and photovoltaic cells. [source] A novel technique to monitor carboxypeptidase G2 expression in suicide gene therapy using 19F magnetic resonance spectroscopyNMR IN BIOMEDICINE, Issue 5 2009Laura Mancini Abstract Development and evaluation of new anticancer drugs are expedited when minimally invasive biomarkers of pharmacokinetic and pharmacodynamic behaviour are available. Gene-directed enzyme prodrug therapy (GDEPT) is a suicide gene therapy in which the anticancer drug is activated in the tumor by an exogenous enzyme previously targeted by a vector carrying the gene. GDEPT has been evaluated in various clinical trials using several enzyme/prodrug combinations. The key processes to be monitored in GDEPT are gene delivery and expression, as well as prodrug delivery and activation. {4-[bis(2-chloroethyl)amino]-3,5-difluorobenzoyl}-L-glutamic acid, a prodrug for the GDEPT enzyme carboxypeptidase-G2 (CPG2; Km,=,1.71,µM; kcat,=,732,s,1), was measured with 19F magnetic resonance spectroscopy (MRS). The 1,ppm chemical shift separation found between the signals of prodrug and activated drug (4-[bis(2-chloroethyl)amino]-3,5-difluorobenzoic acid) is sufficient for the detection of prodrug activation in vivo. However, these compounds hydrolyze rapidly, and protein binding broadens the MR signals. A new CPG2 substrate was designed with hydroxyethyl instead of chloroethyl groups (Km,=,3.5,µM, kcat,=,747,s,1). This substrate is nontoxic and stable in solution, has a narrow MRS resonance in the presence of bovine and foetal bovine albumin, and exhibits a 1.1,ppm change in chemical shift upon cleavage by CPG2. In cells transfected to express CPG2 in the cytoplasm (MDA MB 361 breast carcinoma cells and WiDr colon cancer cells), well-resolved 19F MRS signals were observed from clinically relevant concentrations of the new substrate and its nontoxic product. The MRS conversion half-life (470,min) agreed with that measured by HPLC (500,min). This substrate is, therefore, suitable for evaluating gene delivery and expression prior to administration of the therapeutic agent. Copyright © 2009 John Wiley & Sons, Ltd. [source] Studies on the effect of pH, temperature and metal ions on the production of pectinase from tamarind kernel powder by submerged fermentation using Aspergillus foetidus (NCIM 505)ASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 2 2010P. E. JagadeeshBabu Abstract Filamentous fungi Aspergillus foetidus NCIM 505 was studied for its capacity to produce exo-pectinase in submerged fermentation (SMF) from a new substrate of tamarind kernel powder (TKP). The process was further studied to optimize the initial operating variables like pH, time and temperature. Maximum pectinolytic activity was reached at 72 h of growth and the best fungal strain was found to be A. foetidus NCIM 505. Further, to increase the production rate of pectinase, the effects of metal ions were studied. Metal ions like Cu++, Mg++, Fe++, Co++ and Zn++ at different concentrations were used. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source] Synthesis and Characterization of a C(6) Nucleoside Analogue for the in vivo Imaging of the Gene Expression of Herpes Simplex Virus Type-1 Thymidine Kinase (HSV1 TK)CHEMISTRY & BIODIVERSITY, Issue 3 2006Anass Johayem Abstract The synthesis and biological evaluation of ,6-(1,3-dihydroxyisobutyl)thymine' (DHBT; 1), which corresponds to 6-[3-hydroxy-2-(hydroxymethyl)propyl]-5-methylpyrimidine-2,4(1H,3H)-dione, is reported. DHBT (1) was designed as a new substrate for herpes simplex virus type-1 thymidine kinase (HSV1 TK). The compound was found to be exclusively phosphorylated by HSV1 TK, and to exhibit good binding affinity (Ki,=,35.3±1.3,,M). Cell-proliferation assays with HSV1-TK-transduced human osteosarcoma cells (143B-TK+-HSV1-WT) and with both human-thymidine-kinase-1-negative (143B-TK,) and non-transduced parental (MG-63) cells indicate that 1 is less cytotoxic than the standard drug Ganciclovir. Thus, DHBT (1) represents a promising precursor of a nontoxic reporter probe for the monitoring of HSV1 TK gene expression by means of positron-emission tomography (PET). [source] The role of refugia and dispersal in primary succession on Mount St. Helens, WashingtonJOURNAL OF VEGETATION SCIENCE, Issue 5 2003R.N. Fuller Taxonomy follows the Integrated Taxonomic Information System (ITIS) (http://www.itis.usda.gov) Abstract. An intense lateral blast devastated Mount St. Helens in 1980, but forest understory species survived in some north-slope ,refugia'. We explored the effects of refugia on colonization of barren pumice in 1997 and 1998, 18 yr after the eruption. The seed rain of 23 colonizers came mostly from populations that had previously established in refugia. Parachutists had small, vagile seeds, parasailors had winged seeds, and tumblers were blown along the ground. The latter two groups are heavier and dispersed more slowly, but are more likely to survive. The proportion of the vegetation represented by wind-dispersed species increased with distance from refugia. Parachutist's density declined with time and proximity to refugia. As vegetation adjacent to refugia developed, populations of parasailors and tumblers expanded, foreshadowing their dominance in more remote pumice. Refugia played a critical role in determining the rate and course of succession by providing fertile islands that permitted pioneers and dry meadow species to establish near barren pumice. Species that survived in refugia played a negligible role in colonization. This study showed that when refugia contrast sharply with new substrates, they accelerate recovery by facilitating the invasion of pioneer species. [source] | ||||||||||