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981.
982.
One of the most significant weaknesses in modern day water quality management is the detection of microbiological indicators. Microbial tests are normally conducted off-site, often resulting in long turn-around time, risk of contamination, cross contamination and adulteration. Here Stephen Brown and Moe Hussain present a thought provoking case study where limitations in current analytical technologies for water monitoring had fatal results and discuss new approaches to microbiological monitoring that might prevent similar disasters occurring in the future. 相似文献
983.
A kinetic study of the silver(I)-catalyzed oxidation of tris(1,10-phenanthroline)iron(II) with peroxodiphosphate was carried out by estimating tris-complex at 510 nm. The reaction is found to conform to the rate law (i). with K2 and K3 being the acid dissociation constants of H3P2O8? and H2P2O82?, respectively. The silver(I) catalysis in the reaction has been explained on the basis of complex formation between pdp and silver(I). 相似文献
984.
New picoline adducts with carbamic acid [(furan-2-yl)methylene]hydrazide–CuII (CFMH) (1); thiocarbamic acid [(furan-2-yl)methylene]hydrazide–CuII (TFMH) (2); carbamic acid [(furan-2-yl)ethylidene]hydrazide–CuII (CFEH) (3), thiocarbamic acid [(furan-2-yl)ethylidene]hydrazide–CuII (TFEH) (4); carbamic acid [(thiophene-2-yl) methylene]hydrazide–CuII (CTMH) (5), thiocarbamic acid [(thiophene-2-yl)methylene]hydrazide–CuII (TTMH) (6), carbamic acid [(thiophene-2-yl)ethylidene]hydrazide–CuII (CTEH) (7), thiocarbamic acid [(thiophene-2-yl)ethylidene]hydrazide–CuII (TTEH) (8) have been prepared and characterized by analytical, i.r., electronic, e.s.r. and c.v. spectral data. The electronic spectra suggest distorted octahedral geometry for all the picoline adducts. E.s.r. g
values lie between 2.251–2.286 at l.n.t. All the adducts undergo a quasi-reversible one-electron reduction in the range +0.47 to +0.51 V versus s.c.e., attributable to the CuIII/CuII redox couple. The electron transfer is much faster in the semicarbazone complexes than in the thiosemicarbazone complexes. All adducts showed increased nuclease activity in the presence of oxidant; the nuclease activity is compared with that of the parent copper(II) complexes. 相似文献
985.
ViqarUddin Ahmad Umar Farooq Ahmed Abbaskhan Javid Hussain MuhammadAthar Abbasi SarfrazAhmad Nawaz M.Iqbal Choudhary 《Helvetica chimica acta》2004,87(3):682-689
Six diterpenoids ( 1 – 6 ) belonging to the clerodane and tetracyclic diterpene types were isolated from the CHCl3 extract of Ballota limbata. The structures of the new compounds 1 and 4 – 6 (named ballatenolide A and limbatenolides A–C, resp.) were established by their spectral data, and their relative configuration was determined by 2D NMR. Compounds 2 and 3 were identified as known clerodanes. Compound 1 had a unique feature, i.e., an α,β‐unsaturated γ‐lactone moiety at C(4)/C(6), whereas limbatenolides A–C ( 4 – 6 ) belonged to the rare class of tetracyclic diterpenoids, which are known to occur only in the genus Ballota. All of the isolated compounds showed inhibitory potential in a cholinesterase‐inhibition assay. 相似文献
986.
Gupta AK Palit M Dubey DK Raza SK 《European journal of mass spectrometry (Chichester, England)》2005,11(1):119-125
A series of organophosphorus compounds related to PB-1 toxin [O,O-diphenyl N- cyclooctylphosphoramidate] occurring in dinoflagellate algae as fish toxin have been synthesized and subjected to mass spectral studies under electron ionization. The fragmentation pattern obtained for the compounds has been substantiated by performing tandem mass spectrometry experiments in product ion scan mode. 相似文献
987.
Microbial hydroxylation of pregnenolone derivatives 总被引:1,自引:0,他引:1
Choudhary MI Batool I Shah SA Nawaz SA Atta-ur-Rahman 《Chemical & pharmaceutical bulletin》2005,53(11):1455-1459
Pregnenolone and pregnenolone acetate were incubated with the fungi Cunninghamella elegans, Rhizopus stolonifer and Gibberella fujikuroi. Incubation of with C. elegans yielded metabolites, 3beta,7beta,11alpha-trihydroxypreg-5-en-20-one, 3beta,6alpha,11alpha,12beta,15beta-pentahydroxypreg-4-en-20-one and 3beta,6beta,11alpha-trihydroxypreg-4-en-20-one, while incubation with G. fujikuroi yielded two known metabolites, 3beta,7beta-dihydroxypregn-5-en-20-one and 6beta,15beta-dihydroxypreg-4-ene-3,20-dione. Metabolites and were found to be new. Fermentation of by C. elegans yielded four known oxidative metabolites, androsta-1,4-diene-3,17-dione, 6beta,15beta-dihydroxyandrost-4-ene-3,17-dione and 11alpha,15beta-dihydroxypreg-4-ene-3,20-dione. Fermentation of with R. stolonifer yielded two known metabolites, 11alpha-hydroxypreg-4-ene-3,20-dione and. Compounds were screened for their cholinesterase inhibitory activity in a mechanism-based assay. 相似文献
988.
989.
The analytical properties of 1-phenyl-1,2-propanedione-2-oxime thiosemi-carbazone (PPDOT) are described for the first time. The reagent gives colour reactions with copper(II) and nickel(II) in sodium acetate-acetic acid buffer medium. The copper complex shows maximum absorbance at 465 nm while the nickel complex at 395 nm. Therefore, these colour reactions have been advantageously used for the simultaneous spectrophotometric determination of copper(II) and nickel(II) in synthetic mixture and also in edible oils and seeds. 相似文献
990.
Tyrosinase inhibitors from Rhododendron collettianum and their structure-activity relationship (SAR) studies 总被引:1,自引:0,他引:1
Ahmad VU Ullah F Hussain J Farooq U Zubair M Khan MT Choudhary MI 《Chemical & pharmaceutical bulletin》2004,52(12):1458-1461
A new coumarinolignoid 8'-epi-cleomiscosin A (1) together with the new glycoside 8-O-beta-D-glucopyranosyl-6-hydroxy-2-methyl-4H-1-benzopyrane-4-one (2) have been isolated from the aerial parts of Rhododendron collettianum and their structures determined on the basis of spectroscopic evidences. Tyrosinase inhibition study of these compounds and their structure-activity relationship (SAR) were also investigated. The compounds exhibited potent to mild inhibition activity against the enzyme. Especially, the compound 1 showed strong inhibition (IC50=1.33 microM) against the enzyme tyrosinase, as compared to the standard tyrosinase inhibitors kojic acid (IC50=16.67 microM) and L-mimosine (IC50=3.68 microM), indicating its potential used for the treatment of hyperpigmentation associated with the high production of melanocytes. 相似文献