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981.
Fábio C. Sampaio Paolo Torre Flávia M. Lopes Passos Célia Alencar de Moraes Patrizia Perego Attilio Converti 《Applied biochemistry and biotechnology》2007,136(2):165-181
To obtain in-depth information on the overall metabolic behavior of the new good xylitol producer Debaryomyces hansenii UFV-170, batch bioconversions were carried out using semisynthetic media with compositions simulating those of typical acidic
hemicellulose hydrolysates of sugarcane bagasse. For this purpose, we used media containing glucose (4.3–6.5 g/L), xylose
(60.1–92.1 g/L), or arabinose (5.9–9.2 g/L), or binary or ternary mixtures of them in either the presence or absence of typical
inhibitors of acidic hydrolysates, such as furfural (1.0–5.0 g/L), hydroxymethylfurfural (0.01–0.30 g/L), acetic acid (0.5–3.0
g/L), and vanillin (0.5–3.0 g/L). D. hansenii exhibited a good tolerance to high sugar concentrations as well as to the presence of inhibiting compounds in the fermentation
media. It was able to produce xylitol only from xylose, arabitol from arabinose, and no glucitol from glucose. Arabinose metabolization
was incomplete, while ethanol was mainly produced from glucose and, to a lesser less extent, from xylose and arabinose. The
results suggest potential application of this strain in xyloseto-xylitol bioconversion from complex xylose media from lignocellulosic
materials. 相似文献
982.
Subhi A. Al-Jibori Afra S. S. Al-Zaubai Modher Y. Mohammed Talal A. K. Al-Allaf 《Transition Metal Chemistry》2007,32(3):281-286
Palladium(II) and platinum(II) complexes containing the mixed ligands tertiary diphosphines Ph2P(CH2)
n
PPh2, (n = 1–4) and benz-1,3-imidazoline-2-thione, benz-1,3-oxazoline-2-thione or benz-1,3-thiazoline-2-thione have been prepared
and characterized by elemental analysis, magnetic susceptibility, molar conductance and i.r. spectral data. 31P–{1H}-n.m.r. data have been applied to characterize the produced linkage isomers. 相似文献
983.
Lylia Nini Abdul A Waheed Leelamma M Panicker Meggan Czapiga Jian-Hua Zhang William F Simonds 《BMC biochemistry》2007,8(1):18
Background
Heterotrimeric guanine nucleotide-binding regulatory proteins (G proteins), composed of Gα, Gβ, and Gγ subunits, are positioned at the inner face of the plasma membrane and relay signals from activated G protein-coupled cell surface receptors to various signaling pathways. Gβ5 is the most structurally divergent Gβ isoform and forms tight heterodimers with regulator of G protein signalling (RGS) proteins of the R7 subfamily (R7-RGS). The subcellular localization of Gβ 5/R7-RGS protein complexes is regulated by the palmitoylation status of the associated R7-binding protein (R7BP), a recently discovered SNARE-like protein. We investigate here whether R7BP controls the targeting of Gβ5/R7-RGS complexes to lipid rafts, cholesterol-rich membrane microdomains where conventional heterotrimeric G proteins and some effector proteins are concentrated in neurons and brain. 相似文献984.
T. Vlase Gabriela Vlase N. Doca C. Bolcu 《Journal of Thermal Analysis and Calorimetry》2005,80(1):59-64
Decomposition of dichlorodifluoromethane in thermal plasma was investigated theoretically by computing the equilibrium composition of the gas mixtures involving carbon, chlorine and fluorine in presence of argon (which is assumed to be the main plasma gas) and/or in addition of hydrogen and calcium together with hydrogen. The calculations were carried out for the temperature range between 500 and 6000 K and for the total pressure of the system of 1 bar. Use is made of the fact that a thermal plasma is a plasma in (local) thermal equilibrium, which makes possible the theoretical determination of its equilibrium composition at definite temperature by employing Gibbs free energy data for the compounds present in the system and assuming that the equilibrium of the system corresponds to its minimum energy state. The results of calculations show that toxic molecules and radicals can be, under convenient conditions (appropriate temperature and amount of added substances), converted into stable non-toxic species like CaF2 and CaCl2. 相似文献
985.
Polyethersulfone (PES)-modified epoxy systems with stepwise reaction were studied throughout the entire curing process by using optical microscopes, time-resolved light scattering (TRLS), and a rheolometry instrument compared with that of chainwise polymerization. The results suggested that the phase separation process is mainly controlled by the diffusion of epoxy oligomers for stepwise mechanism system and by that of epoxy monomers for chainwise mechanism system. In case of high PES content (SPES-20%) light-scattering results showed a viscoelastic phase separation and the characteristic relaxation time of phase separation can be described well by the WLF equation. However, in the case of low PES content (SPES-14%) secondary phase separation phenomenon was observed by Optical Microscope and further demonstrated by rheological study. 相似文献
986.
[VIVO(acac)2] reacts with the methanolic solutions of tridentate dibasic ONO donor hydrazone ligands derived from the condensation of
benzoyl hydrazine with either 2-hydroxyacetophenone (H2L1) or its para-substituted derivatives (H2L2–4) (general abbreviation H2L), in the presence of vanillin (Hvan) in equimolar ratio under aerobic conditions generating the mixed-ligand oxovanadium(V)
complexes of the type [VVO(L)(van)], (1)–(4) in good yield. All the complexes are diamagnetic and exhibit only ligand-to-metal charge transfer (l.m.c.t.) band near 510 nm
in addition to intra-ligand (π → π*) transition band near 330 nm in CH2Cl2 solution. 1H-n.m.r. spectra of the complexes in CDCl3 solution indicate the presence of two isomeric forms [(1A), (1B); (2A), (2B); (3A), (3B) and (4A), (4B)] in different ratios, which is explained by the interchange of the two binding sites of van− motif between its coordinated equatorial and axial positions. Complexes display two quasi-reversible one electron reduction
peaks near +0.10 V and near +0.30 V versus s.c.e. in CH2Cl2 solution which are attributed to the successive reduction of VV→ VIV and the VIV→ VIII motifs, respectively. λmax (for l.m.c.t. transition), and the two reduction potential values (E
1/2)I (average of the first step anodic and first step cathodic peak potentials) and (E
1/2)II (average of the second step anodic and second step cathodic peak potentials) of the complexes, are found to be linearly related
to the Hammett constants (σ) of the substituents in the aryloxy ring of the hydrazone ligands. λmax, (E
1/2)I and (E
1/2)II values show large dependence: dλmax/dσ = 37.29 nm, d(E
1/2)I/dσ = 0.21 V and d(E
1/2)II/dσ = 0.21 V, respectively, on σ. 相似文献
987.
Davor Margetić Ronlad N. Warrener Mirjana Eckert-Maksić Ivana Antol Zoran Glasovac 《Theoretical chemistry accounts》2003,109(4):182-189
DFT calculations of 7′–oxasesquinorbornenes and 7,7′-dioxasesquinorbornenes using the B3LYP/6–31G* method are reported.
All the investigated structures (syn- and anti- derivatives) showed significant non-planarity of the central double bond, with the exception of those anti-derivatives possessing symmetrical structures. The influence of the replacement of the methylene groups at position 7- of
the norbornene fragment with oxygen and the introduction of second and third (peripheral) double bonds and benzene rings on
the molecular and electronic structures of these molecules have also been investigated.
Received: 11 November 2002 / Accepted: 6 June 2002 /
Published online: 29 April 2003 相似文献
988.
Annika Niklasson Ingemar Kvarnström Björn Classon Bertil Samuelsson 《Molecules Online》1998,2(1):7-14
Phosphonomethyl substituted 2?,3?-Dideoxy-3?-C-hydroxymethylcytidines have been synthesized and evaluated for their anti HIV-1 activities. The sugar moiety was synthesized starting from (S)-5-hydroxymethylfuran-2-(5H)-one using photocatalyzed addition of methanol. Reduction of the lactone, condensation with silylated 4-methoxy-2(1H)pyrimidinone, followed by phosphonomethylation and deprotection gave the title compounds. The compounds were tested for inhibition of HIV-1 activity but did not show any significant antiviral activity. 相似文献
989.
The coordination compound [Co(C10H7COO)2(H2O)3]2n
· 4nH2O was prepared by the reaction of 1-naphthoic acid and cobalt(II) acetate tetrahydrate in basic solution, and was fully characterized
by X-ray diffraction, element analysis, FTIR, TG-DTA and luminescent spectra. In the crystal the six-coordinated Co(II) centers
are linked into one-dimensional zigzag chains by water molecules, which are further assembled into a two-dimensional network through weak inter-chain C–H···π interactions.
The solid complex exhibits favorable fluorescent properties similar to those of free ligand at room temperature, which can
be assigned to the intraligand electronic transfer. 相似文献
990.
Yong Li 《Theoretical chemistry accounts》2007,117(1):163-165
We present the theoretical results for the positions and widths of the initial anticrossing between Stark manifold n and n + 1 in sodium, obtained by using the method of diagonalization in which zero-field wave functions are chosen from a kind of atomic potential model. These results can provide the quantitative information for understanding the microwave ionization process, whose rate-limiting step is probably the n to n + 1 transition performed at the first crossing between the outermost states of these two manifolds. 相似文献