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71.
72.
73.
Sokoloff MD Anjos JC Appel JA Bracker SB Browder TE Cremaldi LM Elliott JR Escobar CO Estabrooks P Gibney MC Hartner GF Karchin PE Kumar BR Losty MJ Luste GJ Mantsch PM Martin JF McHugh S Menary SR Morrison RJ Nash T Ong P Pinfold J Purohit MV Raab JR Santoro AF Sidhu JS Sliwa K Souza MH Spalding WJ Streetman ME Stundia AB Witherell MS 《Physical review letters》1986,57(24):3003-3006
74.
Biosynthesis of polyhydroxyalkanoates (PHAs) consisting of 3-hydroxyalkanoates (3HAs) of 4 to 10 carbon atoms was examined
in metabolically engineered Escherichia coli strains. When the fadA and/or fadB mutant E. coli strains harboring the plasmid containing the Pseudomonas sp. 61-3 phaC2 gene and the Ralstonia eutropha phaAB genes were cultured in Luria-Bertani (LB) medium supplemented with 2 g/L of sodium decanoate, all the recombinant E. coli strains synthesized PHAs consisting of C4, C6, C8, and C10 monomer units. The monomer composition of PHA was dependent on
the E. coli strain used. When the fadA mutant E. coli was employed, PHA containing up to 63 mol% of 3-hydroyhexanoate was produced. In fadB and fadAB mutant E. coli strains, 3-hydroxybutyrate (3HB) was efficiently incorporated into PHA up to 86 mol%. Cultivation of recombinant fadA and/or fadB mutant E. coli strains in LB medium containing 10 g/L of sodium gluconate and 2 g/L of sodium decanoate resulted in the production of PHA
copolymer containing a very high fraction of 3HB up to 95 mol%. Since the material properties of PHA copolymer consisting
of a large fraction of 3HB and a small fraction of medium-chain-length 3HA are similar to those of low-density polyethylene,
recombinant E. coli strains constructed in this study should be useful for the production of PHAs suitable for various commercial applications. 相似文献
75.
Designing artificial light harvesting systems with the ability to utilize the output energy for fruitful application in aqueous medium is an intriguing topic for the development of clean and sustainable energy. We report here facile synthesis of three prismatic molecular cages as imminent supramolecular optoelectronic materials via two-component coordination-driven self-assembly of a new tetra-imidazole donor (L) in combination with 180°/120° di-platinum(ii) acceptors. Self-assembly of 180° trans-Pt(ii) acceptors A1 and A2 with L leads to the formation of cages Pt4L2(1a) and Pt8L2(2a) respectively, while 120°-Pt(ii) acceptor A3 with L gives the Pt8L2(3a) metallacage. PF6− analogues (1b, 2b and 3b) of the metallacages possess a high molar extinction coefficient and large Stokes shift. 1b–3b are weakly emissive in dilute solution but showed aggregation induced emission (AIE) in a water/MeCN mixture as well as in the solid state. AIE active 2b and 3b in aqueous (90% water/MeCN mixture) medium act as donors for fabricating artificial light harvesting systems via Förster resonance energy transfer (FRET) with organic dye rhodamine-B (RhB) with high energy efficiency and good antenna effect. The metallacages 2b and 3b represent an interesting platform to fabricate new generation supramolecular aqueous light harvesting systems with high antenna effect. Finally, the harvested energy of the LHSs (2b + RhB) and (3b + RhB) was utilized successfully for efficient visible light induced photo-oxidative cross coupling cyclization of N,N-dimethylaniline (4) with a series of N-alkyl/aryl maleimides (5) in aqueous acetonitrile with dramatic enhancement in yields compared to the reactions with RhB or cages alone.Synthesis of Pt(ii) based metallacages as aggregation induced emissive supramolecular architectures for fabricating artificial light harvesting systems for cross coupling cyclization under visible light is achieved. 相似文献
76.
Mandal PK Kaluarachchi KK Ogrin D Bott SG McMurray JS 《The Journal of organic chemistry》2005,70(24):10128-10131
[reaction: see text] Azabicyclo[X.Y.0]alkane amino acids are rigid dipeptide mimetics that are useful tools for structure-activity studies in peptide-based drug discovery. Herein, we report an efficient synthesis of three diastereomers of 9-tert-butoxycarbonyl-2-oxo-3-(N-tert-butoxycarbonylamino)-1-azabicyclo[4.3.0]nonane (3S,6S,9S, 3S,6R,9R, and 3S,6R,9S). Methyl N-Boc-pyroglutamate is cleaved with vinylmagnesium bromide to produce an acyclic gamma-vinyl ketone. Michael addition of N-diphenylmethyleneglycine tert-butyl ester produces the N-Boc-delta-oxo-alpha,omega-diaminoazelate intermediate, which, on hydrogenloysis, gives the fused ring system. Acidolytic deprotection followed by Fmoc-protection provided building blocks suitable for solid-phase synthesis. 相似文献
77.
相转移催化合成对甲氧基肉桂酸-2-乙基己酯的研究 总被引:5,自引:1,他引:5
对甲氧基肉桂酸 2 乙基己酯是一种有效的UVB防晒剂[1 ,2 ] ,一般采用Claisen Schmidt缩合反应制得[3] ,但由于催化剂KOH处于水相 ,对反应物不能充分起到催化作用导致产率较低[4] 。我们利用乙二醇 (PEG)为相转移催化剂合成立体专一的反式对甲氧基肉桂酸 2 乙基己酯 ,产率提高到 72 .5 %。合成路线如下 :1 实验部分1 .1 仪器与试剂BIO RAPFT45 0红外光谱仪 ,用液膜法测试 ;Brurer AM 30 0超导核磁共振仪 (溶剂DC Cl3) ;MAT/44S ,GC MS型色质联用谱仪 ;试剂均为分析纯 ,上海化学试剂… 相似文献
78.
An optimized semi-automatic protocol for parallel synthesis of up to 96 peptide nucleic acids (PNA) or PNA-peptide conjugates using Boc-protection strategy has been developed using a robotic system. The approach is illustrated by synthesizing PNA and PNA-peptide libraries varying between 15 and 27 amino acid units. The peptides (NLS (nuclear localization signal) or Tat-peptide) were attached to N-terminus of the PNA. The method was found to be far superior to that based on the SPOT/Fmoc protocol by which PNA oligomers are synthesized on a modified cellulose membrane. On a 0.5 micromole scale the method typically yielded 2 mg product of 90% purity by HPLC/MALDI-TOF analysis. This approach is suitable for screening of a large number of PNA and/or peptide sequences for biochemical and biological studies. 相似文献
79.
A. K. Shukla S. Saini P. Kumar J. S. P. Rai A. K. Srivastava 《Journal of polymer science. Part A, Polymer chemistry》1989,27(3):807-815
Polymerization of vinyl acetate initiated by β-picolinium p-chlorophenacylide was carried out at 30, 35, and 40°C, using conventional dilatometric technique. The initiator and the monomer exponent values were 0.80 ± 0.15 and unity, respectively. The polymerization was inhibited in the presence of hydroquinone, but was favored by nonpolar solvent and polymerization temperature. The energy of activation was 90.3 KJ mol?1. An average value of k/kt for the present system was found to be 0.37 × 10?2. The results are explained in terms of a radical mode of polymerization with degradative initiator transfer; the principal mode of termination, however, was bimolecular. 相似文献
80.
In search for a cheaper anode catalyst for the oxidation of ethanol for development of direct alcohol fuel cells, Pd has been
considered here as an interesting substitute for Pt in Pt Ru binary electrodeposite. The binary catalyst when co-deposited
on nickel support has been found to increase the current density and decrease the anodic overvoltage significantly with respect
to pure Pt, Pd and Ni. Its electrocatalytic capability is also comparable with that of the Pt-Ru binary electrocatalyst on
Ni-support, when studied in 1 M EtOH containing 1 M NaOH solution. The effect of loading of Pd Ru electrocatalyst on Ni support has also been tested. The electrocatalytic activity
of the electrodes for oxidation of ethanol has been explained by studies of cyclic voltammetry, chronopotentiometry, steady-state
polarization, and conjugated scanning electron microscopy–energy dispersion X-ray spectroscopy. It has been found that electrode
containing the higher amount of deposit are less affected by carbonaceous poisons. 相似文献