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61.
The new Pd(II), Pt(II), Re(V), Mo(VI) and W(VI) complexes of 2-hydroxynicotinic acid (H2nicO), trans-[PdCl(HnicO)(PPh3)2]·0.75CH3CN (1), K[PdCl(HnicO)2]·H2O (2), [Pd(HnicO)2(bipy)] (3), cis-[PtCl(HnicO)(PPh3)2]·0.75CH3OH·0.5H2O (4), [PtCl(HnicO)(bipy)] (5), cis-[ReOI2(HnicO)(PPh3)] (6), Na2[Mo2O6(HnicO)2]·5H2O (7), Na2[Mo4O12(HnicO)2]·2H2O (8) and Na2[W2O6(HnicO)2]·5H2O (9) have been prepared. The crystal structures of 1 and 4, were determined by X-ray diffraction and show the HnicO− ligand coordinated to palladium or platinum through the nitrogen atom only. Infrared, Raman, 1H and 13C{1H} NMR spectroscopic data for the complexes are presented and are in agreement with the crystallographic results. 相似文献
62.
Thomasen H Meldgaard M Freitag M Petersen M Wengel J Nielsen P 《Chemical communications (Cambridge, England)》2002,(17):1888-1889
A novel class of 3',4'-trans-linked bicyclic nucleosides with locked S-type furanose conformations is introduced by synthesis of two model derivatives; one was obtained by cyclic ether formation and the other by ring-closing metathesis methodology. 相似文献
63.
Araujo MH Hitchcock PB Nixon JF Kuehner U Stelzer O 《Chemical communications (Cambridge, England)》2003,(9):1092-1093
Hydrozirconation of the eta 2-phosphaalkyne complex [Pt(dppe)(eta 2-tBuCP)] with [ZrHCl(eta 5-C5H5)2], followed by treatment with the chlorophosphaalkene ClP=C(SiMe3)2 affords the eta 2-2,3-diphosphabutadiene complex [Pt(dppe)(eta 2-tBuC(H)=PP=C(SiMe3)2]. In the presence of [Pt(PPh3)2] the latter undergoes an addition reaction with water to afford the structurally characterised Pt(II) complex [Pt(dppe)(tBuCH2P(O)HPC(SiMe3)2]. 相似文献
64.
Florian P. Weissenboeck Helena Schepers Prof. Dr. Andrea Rentmeister 《Angewandte Chemie (International ed. in English)》2023,62(23):e202301778
A major stage in the expression of genes is the translation of messenger RNA (mRNA), and the regulation of this process is essential for protein production in cells. How tightly controlled gene expression can be spatially and temporally, is particularly evident in polar cells and embryonic development. We need tools to dissect these complex processes, if we wish to understand the underlying links, especially the difficulties brought on by malfunction. External bioorthogonal triggers are very helpful in this area, if they let us precisely control where and when a process is started. Equipping nucleic acids with light-responsive groups has proven to be an effective approach to examine the dynamic regulatory route of mRNA translation in living cells. In this review, we present an overview of the most recent methods for optochemically controlling translation, focusing on cis-acting technologies. 相似文献
65.
Comparison of different strains of the yeastYarrowia lipolytica for citric acid production from glucose hydrol 总被引:3,自引:0,他引:3
Maria Wojtatowicz Waldemar Rymowicz Helena Kautola 《Applied biochemistry and biotechnology》1991,31(2):165-174
Four commercial strains and two mutants of the yeast species Yarrowia lipolytica were screened using batch fermentation. Strain Y. lipolytica A-101-1.14 (induced with UV irradiation) was found to be the most suitable for citric acid production from glucose hydrol (39.9% glucose and 2.1% other sugars), a byproduct of glucose production from potato starch. The specific rate of total citric and isocitric acid production was 0.138 g/g.h, the yield on consumed glucose 0.93 g/g, and the productivity achieved was as high as 1.25 g/L.h. All of the tested yeast strains were able to utilize only the glucose from the glucose hydrol medium. Thus, some residual higher oligosaccharides remained in the process effluent. 相似文献
66.
M. Alves Da Silva M. Helena Gil A. P. Piedade J. S. Redinha A. M. Oliveira Brett J. M. Caridade Costa 《Journal of polymer science. Part A, Polymer chemistry》1991,29(2):269-274
The immobilization of catalase on grafted membranes of poly(ethylene)-g-co-acrylic acid and poly(tetrafluoroethylene)-g-co-acrylic acid and their application in hydrogen peroxide electrochemical sensors is described. The introduction of carboxylic acid groups onto a hydrophobic support provides a good environment for subsequent enzyme immobilization. This single membrane, hydrogen peroxide sensor showed significant improvement with respect to the double membrane versions. The response is very rapid, the linear range being from 10 μM up to 6 mM, with a detection limit of 4.7 μM, and a lifetime of more than 4 months. 相似文献
67.
Kažoka Helena Turovska Baiba Upmanis Toms Orlova Natalja Vorona Maksims 《Chromatographia》2021,84(7):663-675
Chromatographia - Our previous studies concerning the enantioseparation of 4C-substituted pyrrolidin-2-one derivatives on coated polysaccharide-based chiral stationary phases have shown that... 相似文献
68.
Enolesters as chain end-functionalizing agents for the living ring opening metathesis polymerization
Peng Liu Mohammad Yasir Helena Kurzen Nils Hanik Mark Schäfer Andreas F. M. Kilbinger 《Journal of polymer science. Part A, Polymer chemistry》2017,55(18):2983-2990
Functional enolethers have previously been used to introduce functional end groups at the chain end of ruthenium carbene complex initiated living ring opening metathesis polymers. Here, we investigated whether the weaker π-donating enolesters could equally be used in regio selective reactions with ruthenium carbene complexes and thus as polymer end-functionalization reagents. Enolesters such as vinyl acetate, butenyl acetate, 3-(4-(tert-butoxy)phenyl)propenyl acetate and 6-(((benzyloxy)carbonyl)amino)hex-1-en-1-yl acetate were used as living ROMP terminating agents. All gave the expected end groups proving that enolesters are synthetically easily accessible targets for living ROMP end-functionalization. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2983–2990 相似文献
69.
Coro Echeverria Pedro L. Almeida Oscar F. Aguilar Gutierrez Alejandro D. Rey Maria Helena Godinho 《Journal of Polymer Science.Polymer Physics》2017,55(10):821-830
The shear rate dependence of material functions such as shear viscosity (η) and the first normal stress difference (N1) were given and interpreted earlier by Kiss and Porter. Their widely accepted work revealed the possibility of having a negative minimum of N1 for polymeric liquid crystals. In this work, we disclose for the first time the evidence of two negative N1 minima on a sheared cellulosic lyotropic system. The lower shear rate minimum is ascribed to the uncoiling of the cholesteric helix, as theoretically predicted earlier. Our findings contribute also to the understanding of the other minimum already reported in the literature and attributed to the nematic director tumbling mode. Moreover, the elastic change that the LC‐HPC sample undergoes during the helix unwinding of the cholesteric structure is also by means of oscillatory measurements. This study is a contribution for the understanding of the structure‐properties relationship linked with the complex rheological behavior of chiral nematic cellulose‐based systems and may help to improve their further processing. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 821–830 相似文献
70.
João Paulo R.F. André Hugh D. Burrows Carlos F.G.C. Geraldes Maria Da Graça M. Miguel M.Helena S.F. Teixeira L.F. Vilas Boas 《Polyhedron》1996,15(24):4331-4340
Complexation of europium(III) with glyceryl-1- and -2-phosphates has been studied by metal ion luminescence, 1H and 13C NMR spectroscopy and potentiometry. From the luminescence and NMR studies, the formation of a 1:1 inner-sphere complex, in which the glyceryl phosphate is directly bound to the metal, is confirmed. Similar apparent binding constants at pH 2 were obtained by the three methods. Values obtained by NMR at pH 2 are 53 M−1 and 12 M−1 for glyceryl-1- and -2-phosphate, respectively. By comparison with literature data on related systems it is suggested that the ligands bind through the phosphate group. To obtain structural information from the NMR data, complexation has also been studied with the lanthanide ions Dy(III), Er(III) and Gd(III) using both chemical shift and relaxation data. From this, metal-proton distance ratios have been calculated. Comparison of 1H and 13C NMR spectral data in the presence of paramagnetic lanthanides suggests conformational equilibria in the solutions. From the potentiometric studies, global formation constants have been determined, and speciation diagrams obtained over the pH range 1.5pH7.0 for ligand/metal ratios of 1 and 30. Implications of these results on lanthanide induced fusion of phospholipid membranes are discussed. 相似文献