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71.
Bedford RB Bruce DW Frost RM Goodby JW Hird M 《Chemical communications (Cambridge, England)》2004,(24):2822-2823
Iron(III) salen and related complexes are active catalysts for the coupling, under mild and simple reaction conditions, of aryl Grignard reagents with primary and secondary alkyl halide substrates bearing beta-hydrogens. 相似文献
72.
De La Rosa Luis B. Reshamwala Sultan Latimer Vivian M. Shawky Bahaa T. Dale Bruce E. Stuart Earnest D. 《Applied biochemistry and biotechnology》1994,(1):483-497
The herbaceous crops that may provide fermentable carbohydrates for production of fuels and chemicals also contain 10–20%
protein. Protein coproduction with biomass-derived fuels and chemicals has important advantages: (1) food and fuel production
can be integrated, and (2) protein is a high-value product that may significantly improve overall process economics. We report
the results of an integrated approach to producing protein and fermentable sugars from one herbaceous species, Coastal Bermudagrass
(CBG). The ammonia fiber explosion (AFEX) process makes possible over 90% conversion of cellulose and hemicellulose to simple
sugars (about 650 mg reducing sugars/g dry CBG) at 5 IU cellulase/g vs < 20% conversion for untreated CBG. The AFEX treatment
also improves protein extraction from CBG; over 80% protein recovery is possible from AFEX-treated CBG vs about 30% recovery
from untreated CBG. 相似文献
73.
74.
Sibrina N. Collins Constance M. Brett Bruce E. Bursten 《Journal of Cluster Science》2004,15(4):469-487
The photochemical CO-loss products of the diruthenium complexes [CpRu(CO) 2]2 (5; Cp = 5-C5H5), [Cp*Ru(CO)2]2 (5*; Cp* = 5-C5(CH3)5) and CpCp*[Ru(CO)2]2 (5) have been studied experimentally in low-temperature (96 K) matrices in 3-methylpentane by using IR spectroscopy. It is proposed that all three complexes undergo single-CO-loss chemistry but that the products have different structures. The single-CO-loss product from 5 is proposed to have one bridging and two terminal carbonyl ligands, whereas 5* and 5 generate triply bridged CO-loss products similar to that observed from [CpFe(CO)2]2 and [Cp*Fe(CO)2]2. Double-CO-loss from 5* and 5*
9 is also apparently observed. Relativistic DFT calculations have been carried out on various isomers of the starting materials and on potential CO-loss products from 5. The calculations suggest that the triply bridged product Cp2Ru2(-CO)3 (6) might have a singlet ground state in contrast to the corresponding diiron complex Cp2Fe2(-CO)3 (3), which has a triplet ground state. 相似文献
75.
X-ray absorption near-edge spectra and temperature-programmed oxidation and reduction data demonstrate that Au(I) and Au(0) are both present in working MgO-supported gold catalysts for CO oxidation. EXAFS data indicate gold clusters with essentially the same average diameter (about 30 A) in each catalyst sample. Thus, the results provide no evidence of an effect of gold cluster size on the catalytic activity, but both the catalytic activity and the surface concentration of Au(I) were found to decrease with increasing CO partial pressure (as Au(0) was increasingly formed), demonstrating that the catalytic sites incorporate Au(I). 相似文献
76.
King RB 《Inorganic chemistry》2005,44(3):466-467
The metallaborane Cp4Co4B4H4 and the organometallic cluster Cp4Fe4C4H4 (Cp = eta5-cyclopentadienyl) not only are isoelectronic but also exhibit completely analogous eight-vertex bisdisphenoidal structures. Such structures, as well as the tetracapped tetrahedral structure of the Cp4Fe4(mu3-CO)4 precursor to Cp4Fe4C4H4, can be derived from a cube by insertion of diagonals in each of the six faces. Furthermore, the formation of Cp4Fe4C4H4 from Cp4Fe4(mu3-CO)4 can be described as a double diamond-square-diamond process preserving D2d symmetry throughout the process. 相似文献
77.
Structural characterization of lipopeptide biomarkers isolated from Bacillus globigii 总被引:2,自引:0,他引:2
Spectra obtained using matrix-assisted laser desorption/ionization (MALDI) mass spectrometry of Bacillus globigii (Bacillus subtilis niger) spores, vegetative cells and the culture supernatant show a cluster of biomarkers centered at a molecular mass of 1478 Da. Three biomarkers were isolated from the cell-free culture supernatant by solid-phase extraction and reversed-phase high-performance liquid chromatography, and characterized using various kinds of mass spectrometry. A Fourier transform mass spectrometer with a MALDI source was used to determine the monoisotopic protonated masses at 1463.8, 1477.8, and 1505.8 Da in order of elution. The mass differences of 14 and 28 Da suggest that they are homologous molecules. Alkaline hydrolysis of each species showed that it contained a lactone linkage. Strong acid hydrolysis released a fatty acid from an amide bond, consistent with a lipopeptide. A quadrupole time-of-flight instrument with a nanospray source was used to sequence the hydrolyzed forms of the three biomarkers. The cyclic lipopeptides were found to have amino acid sequences identical with those in fengycins and plipastatins, antimicrobial compounds with phospholipase inhibitor activity, previously identified in related species of Bacillus subtilis and Bacillus cereus. 相似文献
78.
Wenhui Zhang Bruce C. Noll Anthony S. Serianni 《Acta Crystallographica. Section C, Structural Chemistry》2007,63(10):o578-o581
The β‐pyranose form, (III), of 3‐deoxy‐d ‐ribo‐hexose (3‐deoxy‐d ‐glucose), C6H12O5, crystallizes from water at 298 K in a slightly distorted 4C1 chair conformation. Structural analyses of (III), β‐d ‐glucopyranose, (IV), and 2‐deoxy‐β‐d ‐arabino‐hexopyranose (2‐deoxy‐β‐d ‐glucopyranose), (V), show significantly different C—O bond torsions involving the anomeric carbon, with the H—C—O—H torsion angle approaching an eclipsed conformation in (III) (−10.9°) compared with 32.8 and 32.5° in (IV) and (V), respectively. Ring carbon deoxygenation significantly affects the endo‐ and exocyclic C—C and C—O bond lengths throughout the pyranose ring, with longer bonds generally observed in the monodeoxygenated species (III) and (V) compared with (IV). These structural changes are attributed to differences in exocyclic C—O bond conformations and/or hydrogen‐bonding patterns superimposed on the direct (intrinsic) effect of monodeoxygenation. The exocyclic hydroxymethyl conformation in (III) (gt) differs from that observed in (IV) and (V) (gg). 相似文献
79.
Khoudiakov M Parise AR Brunschwig BS 《Journal of the American Chemical Society》2003,125(15):4637-4642
Electroabsorption (Stark) spectroscopy has been used to study the dye sensitized interfacial electron transfer in an Fe(II)(CN)(6)(4)(-) donor complex bound to a TiO(2) nanoparticle. The average charge-transfer distance determined from the Stark spectra is 5.3 A. This value is similar to the estimated distance between the Fe(II) center of the complex and the Ti(IV) surface site coordinated to the nitrogen end of a bridging CN ligand in (CN)(5)Fe(II)-CN-Ti(IV)(particle). This finding suggests that the electron injection is to either an individual titanium surface site or a small number of Ti centers localized around the point of ferrocyanide coordination to the particle and not into a conduction band orbital delocalized over the nanoparticle. The polarizability change, Tr(Deltaalpha), between the ground and the excited states of the Fe(II)(CN)(6)(4)(-)-TiO(2)(particle) system is approximately 3 time larger than normally observed in mixed-valence dinuclear metal complexes. It is proposed that the large polarizability of the excited state increases the dipole-moment changes measured by Stark spectroscopy. 相似文献
80.
Vapor to liquid multicomponent nucleation is a dynamical process governed by a delicate interplay between condensation and evaporation. Since the population of the vapor phase is dominated by monomers at reasonable supersaturations, the formation of clusters is governed by monomer association and dissociation reactions. Although there is no intrinsic barrier in the interaction potential along the minimum energy path for the association process, the formation of a cluster is impeded by a free energy barrier. Dynamical nucleation theory provides a framework in which equilibrium evaporation rate constants can be calculated and the corresponding condensation rate constants determined from detailed balance. The nucleation rate can then be obtained by solving the kinetic equations. The rate constants governing the multistep kinetics of multicomponent nucleation including sensitivity analysis and the potential influence of contaminants will be presented and discussed. 相似文献