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81.
82.
Mariko Kitajima Satoko Ohara Noriyuki Kogure Dammrong Santiarworn Hiromitsu Takayama 《Tetrahedron》2013
Six new β-carboline-type indole alkaloid glycosides, ophiorrhisides A–F (1–6), were isolated from Ophiorrhiza trichocarpon (Rubiaceae) collected in Thailand. Ophiorrhisides A (1) and B (2) possess a lactam function in the C ring and a unique biose residue in the molecule. Ophiorrhiside F (6) has a highly oxidized C ring with a 1,2-dicarbonyl function at C-5 and C-6 positions as well as a double bond between C-3 and C-14. 相似文献
83.
84.
Andrzej Wisniewski Eugenia Skorupowa Janusz Sokolowski Lech Rozanski Daniel Glod Gerard Descotes 《Journal of carbohydrate chemistry》2013,32(1):73-83
Abstract Conditions have been established for the microsyntheses of dianhydro-hexitols by reaction of 1, 4-monoanhydro-D, L-galactitols and 1, 5-monoanhydro-D-galactitol as well as of 1, 4- and 1, 5-monoanhydro-D-glucitols and -D-mannitols with tosyl chloride in pyridine followed by cyclization of the resulting 6-O-tosyl derivatives in methanolic solution of sodium methoxide. The dianhydrohexitols were formed by intramolecular nucleophilic substitution of the C-6 O-tosyl group with a properly stereochemically oriented hydroxyl group. Components of the mixtures were separated by capillary gas chromato-graphy using columns coated with SP-2340 and identified by GC-MS. The identities of the synthesized dianhydrohexitols were confirmed by comparison with the GC retention times and mass spectra of authentic samples. 相似文献
85.
Shulan Cai Jianzhang Li Bin Xie Leijin He Xiaolan Zhang 《Journal of Dispersion Science and Technology》2014,35(1):93-97
A macrocyclic ligand was synthesized and characterized. The kinetics of hydrolysis of bis(p-nitrophenyl)phosphate (BNPP) in the catalytic system containing macrocyclic ligand and praseodymium(III) was investigated. The analysis of specific absorption spectrums of the hydrolytic reaction systems indicated that key intermediates made up of BNPP and praseodymium(III) complexes are formed in the reaction process of BNPP catalytic hydrolysis. In this, the mechanism of BNPP catalytic hydrolysis proposed is based on the analytic result of specific absorption spectrum, and the corresponding kinetic constants are calculated. The results showed that the praseodymium(III) complexes as hydrolase mimics exhibit good catalytic activity and similar catalytic character to natural enzyme. 相似文献
86.
87.
Yang W Zhou YF Dai HP Bi LJ Zhang ZP Zhang XH Leng Y Zhang XE 《Analytical and bioanalytical chemistry》2008,390(8):2133-2140
Methyl parathion hydrolase (MPH) is an enzyme that catalyzes the degradation of methyl parathion, generating a yellow product
with specific absorption at 405 nm. The application of MPH as a new labeling enzyme was illustrated in this study. The key
advantages of using MPH as a labeling enzyme are as follows: (1) unlike alkaline phosphatase (AP), horseradish peroxidase
(HRP), and glucose oxidase (GOD), MPH is rarely found in animal cells, and it therefore produces less background noise; (2)
its active form in solution is the monomer, with a molecular weight of 37 kDa; (3) its turnover number is 114.70 ± 13.19 s−1, which is sufficiently high to yield a significant signal for sensitive detection; and (4) its 3D structure is known and
its C-terminal that is exposed to the surface can be easily subjected to the construction of genetic engineering monocloning
antibody–enzyme fusion for enzyme-linked immunosorbent assay (ELISA). To demonstrate its utility, MPH was ligated to an single-chain
variable fragment (scFv), known as A1E, against a white spot syndrome virus (WSSV) with the insertion of a [–(Gly–Ser)5–] linker peptide. The resulting fusion protein MPH-A1E possessed both the binding specificity of the scFv segment and the
catalytic activity of the MPH segment. When MPH-A1E was used as an ELISA reagent, 25 ng purified WSSV was detected; this was
similar to the detection sensitivity obtained using A1E scFv and the HRP/Anti-E Tag Conjugate protocol. The fusion protein
also recognized the WSSV in 1 μL hemolymph from an infected shrimp and differentiated it from a healthy shrimp.
Figure The 3-D structure of MPH. (a) monomer showing C- and N-terminals; (b) the crystal structure of the dimer
W. Yang and Y.-F. Zhou contributed equally to this work. 相似文献
88.
《Mendeleev Communications》2023,33(1):109-111
Antimycobacterial activity of certain ureas as well as spirocyclic piperidines described in the literature prompted us to synthesize and test a series of hybrids of spirocyclic piperidine with ureas. Surprisingly, no activity was detected against Mycobacterium tuberculosis. However, significant antibacterial activity was identified and confirmed against common gram-positive as well as gram-negative bacteria. 相似文献
89.
Leif‐A. Garbe Katja Morgenthal Katrin Kuscher Roland Tressl 《Helvetica chimica acta》2008,91(6):993-1007
Epoxides of fatty acids are hydrolyzed by epoxide hydrolases (EHs) into dihydroxy fatty acids which are of particular interest in the mammalian leukotriene pathway. In the present report, the analysis of the configuration of dihydroxy fatty acids via their respective hydroxylactones is described. In addition, the biotransformation of (±)‐erythro‐7,8‐ and ‐3,4‐dihydroxy fatty acids in the yeast Saccharomyces cerevisiae was characterized by GC/EI‐MS analysis. Biotransformation of chemically synthesized (±)‐erythro‐7,8‐dihydroxy(7,8‐2H2)tetradecanoic acid ((±)‐erythro‐ 1 ) in the yeast S. cerevisiae resulted in the formation of 5,6‐dihydroxy(5,6‐2H2)dodecanoic acid ( 6 ), which was lactonized into (5S,6R)‐6‐hydroxy(5,6‐2H2)dodecano‐5‐lactone ((5S,6R)‐ 4 ) with 86% ee and into erythro‐5‐hydroxy(5,6‐2H2)dodecano‐6‐lactone (erythro‐ 8 ). Additionally, the α‐ketols 7‐hydroxy‐8‐oxo(7‐2H1)tetradecanoic acid ( 9a ) and 8‐hydroxy‐7‐oxo(8‐2H1)tetradecanoic acid ( 9b ) were detected as intermediates. Further metabolism of 6 led to 3,4‐dihydroxy(3,4‐2H2)decanoic acid ( 2 ) which was lactonized into 3‐hydroxy(3,4‐2H2)decano‐4‐lactone ( 5 ) with (3R,4S)‐ 5 =88% ee. Chemical synthesis and incubation of (±)‐erythro‐3,4‐dihydroxy(3,4‐2H2)decanoic acid ((±)‐erythro‐ 2 ) in yeast led to (3S,4R)‐ 5 with 10% ee. No decano‐4‐lactone was formed from the precursors 1 or 2 by yeast. The enantiomers (3S,4R)‐ and (3R,4S)‐3,4‐dihydroxy(3‐2H1)nonanoic acid ((3S,4R)‐ and (3R,4S)‐ 3 ) were chemically synthesized and comparably degraded by yeast without formation of nonano‐4‐lactone. The major products of the transformation of (3S,4R)‐ and (3R,4S)‐ 3 were (3S,4R)‐ and (3R,4S)‐3‐hydroxy(3‐2H1)nonano‐4‐lactones ((3S,4R)‐ and (3R,4S)‐ 7 ), respectively. The enantiomers of the hydroxylactones 4, 5 , and 7 were chemically synthesized and their GC‐elution sequence on Lipodex® E chiral phase was determined. 相似文献
90.
Lei Y Mulchandani P Chen W Mulchandani A 《Applied biochemistry and biotechnology》2007,136(3):243-250
A whole cell-based amperometric biosensor for highly selective, sensitive, rapid, and cost-effective determination of the
organophosphate pesticides fenitrothion and ethyl p-nitrophenol thiobenzenephosphonate (EPN) is discussed. The biosensor comprised genetically engineered p-nitrophenol (PNP)-degrading bacteria Pseudomonas putida JS444 anchoring and displaying organophosphorous hydrolase (OPH) on its cell surface as biological sensing element and carbon
paste electrode as the amperometric transducer. Surface-expressed OPH catalyzed the hydrolysis of organophosphorous pesticides
such as fenitrothion and EPN to release PNP and 3-methyl-4-nitrophenol, respectively, which were subsequently degraded by
the enzymatic machinery of P. putida JS444 through electrochemically active intermediates to the TCA cycle. The electrooxidization current of the intermediates
was measured and correlated to the concentration of organophosphates. Operating at optimum conditions, 0.086 mg dry wt of
cell operating at 600 mV of applied potential (vs Ag/AgCl reference) in 50 mM citratephosphate buffer, pH 7.5, with 50 μM CoCl2 at room temperature, the biosensor measured as low as 1.4 ppb of fenitrothion and 1.6 ppb of EPN. There was no interference
from phenolic compounds, carbamate pesticides, triazine herbicides, or organophosphate pesticides without nitrophenyl substituent.
The service life of the biosensor and the applicability to lake water were also demonstrated. 相似文献