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991.
Dr. Nina Perkas Judith Grinblat Prof. Aharon Gedanken 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(15):4575-4582
Titanium oxide (TiO2) nanoparticles (NPs) in their two forms, anatase and rutile, were synthesized and deposited onto the surface of cotton fabrics by using ultrasonic irradiation. The structure and morphology of the nanoparticles were analyzed by using characterization methods such as XRD, TEM, STEM, and EDS. The antimicrobial activities of the TiO2–cotton composites were tested against Escherichia coli (Gram‐negative) and Staphylococcus aureus (Gram‐positive) strains, as well as against Candida albicans. Significant antimicrobial effect was observed, mainly against Staphylococcus aureus. In addition, the combination of visible light and TiO2 NPs showed enhanced antimicrobial activity. 相似文献
992.
Alexander Higelin Ulf Sachs Sarah Keller Prof. Dr. Ingo Krossing 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(32):10029-10034
In a new oxidative route, Ag+[Al(ORF)4]? (RF=C(CF3)3) and metallic indium were sonicated in aromatic solvents, such as fluorobenzene (PhF), to give a precipitate of silver metal and highly soluble [In(PhF)n]+ salts (n=2, 3) with the weakly coordinating [Al(ORF)4]? anion in quantitative yield. The In+ salt and the known analogous Ga+[Al(ORF)4]? were used to synthesize a series of homoleptic PR3 phosphane complexes [M(PR3)n]+, that is, the weakly PPh3‐bridged [(Ph3P)3In–(PPh3)–In(PPh3)3]2+ that essentially contains two independent [In(PPh3)3]+ cations or, with increasing bulk of the phosphane, the carbene‐analogous [M(PtBu3)2]+ (M=Ga, In) cations. The MI? P distances are 27 to 29 pm longer for indium, and thus considerably longer than the difference between their tabulated radii (18 pm). The structure, formation, and frontier orbitals of these complexes were investigated by calculations at the BP86/SV(P), B3LYP/def2‐TZVPP, MP2/def2‐TZVPP, and SCS‐MP2/def2‐TZVPP levels. 相似文献
993.
Christian Hils Emma Fuchs Franziska Eger Dr. Judith Schöbel Dr. Holger Schmalz 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(25):5611-5614
Multiresponsive polymers that can respond to several external stimuli are promising materials for a manifold of applications. Herein, a facile method for the synthesis of triple-responsive (pH, temperature, CO2) poly(N,N-diethylaminoethyl methacrylamide) by a post-polymerization amidation of poly(methyl methacrylate) (PMMA) is presented. Combined with trivalent counterions ([Fe(CN)6]3−) both an upper and lower critical solution temperature (UCST/LCST)-type phase behavior can be realized at pH 8 and 9. PMMA and PMMA-based block copolymers are readily accessible by living anionic and controlled radical polymerization techniques, which opens access to various responsive polymer architectures based on the developed functionalization method. This method can also be applied on melt-processed bulk PMMA samples to introduce functional, responsive moieties at the PMMA surface. 相似文献
994.
Villamena FA Rockenbauer A Gallucci J Velayutham M Hadad CM Zweier JL 《The Journal of organic chemistry》2004,69(23):7994-8004
The nitrone 5-carbamoyl-5-methyl-1-pyrroline N-oxide (AMPO) was synthesized and characterized. Spin trapping of various radicals by AMPO was demonstrated for the first time by electron paramagnetic resonance (EPR) spectroscopy. The resulting spin adducts for each of these radicals gave unique spectral profiles. The hyperfine splitting constants for the superoxide adduct are as follows: isomer I (80%), a(nitronyl)(-)(N) = 13.0 G and a(beta)(-)(H) = 10.8 G; isomer II (20%), a(nitronyl)(-)(N) = 13.1 G, a(beta)(-)(H) = 12.5 G, and a(gamma)(-)(H) = 1.75 G. The half-life of the AMPO-O(2)H was about 8 min, similar to that observed for EMPO but significantly shorter than that of the DEPMPO-O(2)H with t(1/2) approximately 16 min. However, the spectral profile of AMPO-O(2)H at high S/N ratio is distinguishable from the spectrum of the (*)OH adduct. Theoretical analyses using density functional theory calculations at the B3LYP/6-31+G//B3LYP/6-31G level were performed on AMPO and its corresponding superoxide adduct. Calculations predicted the presence of intramolecular H-bonding in both AMPO and its superoxide adduct. The H-bonding interaction was further confirmed by an X-ray structure of AMPO, and of the novel and analogous amido nitrone 2-amino-5-carbamoyl-5-methyl-1-pyrroline N-oxide (NH(2)-AMPO). The thermodynamic quantities for superoxide radical trapping by various nitrones have been found to predict favorable formation of certain isomers. The measured partition coefficient in an n-octanol/buffer system of AMPO was similar to those of DMPO and DEPMPO. This study demonstrates the suitability of the AMPO nitrone for use as a spin trap to study radical production in aqueous systems. 相似文献
995.
In order to investigate experimentally inaccessible, molecular-level detail regarding interleaflet interaction in membranes, we have run an extensive series of coarse-grained molecular dynamics simulations of phase separated lipid bilayers. The simulations are motivated by differences in lipid and cholesterol composition in the inner and outer leaflets of biological membranes. Over the past several years, this phenomenon has inspired a series of experiments in model membrane systems which have explored the effects of lipid compositional asymmetry in the two leaflets. The simulations are directed at understanding one potential consequence of compositional asymmetry, that being regions of bilayers where liquid-ordered (L(o)) domains in one leaflet are opposite liquid-disordered (L(d)) domains in the other leaflet (phase asymmetry). The simulated bilayers are of two sorts: 1) Compositionally symmetric leaflets where each of the two leaflets contains an identical, phase separated (L(o)/L(d)) mixture of cholesterol, saturated and unsaturated phospholipid; and 2) Compositionally asymmetric leaflets, where one leaflet contains a phase separated (L(o)/L(d)) mixture while the other contains only unsaturated lipid, which on its own would be in the L(d) phase. In addition, we have run simulations where the lengths of the saturated lipid chains as well as the mole ratios of the three lipid components are varied. Collectively, we report on three types of interleaflet coupling within a bilayer. First, we show the effects of compositional asymmetry on acyl chain tilt and order, lipid rotational dynamics, and lateral diffusion in regions of leaflets that are opposite L(o) domains. Second, we show substantial effects of compositional asymmetry on local bilayer curvature, with the conclusion that phase separated leaflets resist curvature, while inducing large degrees of curvature in an opposing L(d) leaflet. Finally, in compositionally symmetric, phase separated bilayers, we find phase asymmetry (domain antiregistration) between the two leaflets occurs as a consequence of mismatched acyl chain-lengths in the saturated and unsaturated lipids. 相似文献
996.
Susan L. Bontems Judith Stein Michael A. Zumbrum 《Journal of polymer science. Part A, Polymer chemistry》1993,31(11):2697-2710
α,ω-Divinyl-terminated polydimethylsiloxane polymers with low polydispersivity were synthesized via anionic polymerization of hexamethylcyclotrisiloxane (D3). Five “monodisperse” polymers with different molecular weights were hydrosilylated with tetrakisdimethylsiloxysilane in the presence of platinum catalysts and inhibitors to form crosslinked networks. Control studies to determine the effect of platinum, silicon hydride, and heat were performed to verify that no redistribution occurred during hydrosilylation. The properties of these cured samples were characterized chemically by degradation with trifluoromethanesulfonic acid in the presence of hexamethyldisiloxane, infrared spectroscopy, and nuclear magnetic spectroscopy. Mechanical properties were studied by measurements of Shore A hardness, dynamic shear modulus, and tensile modulus. The relationship between the molecular weight of the vinyl polymer and the final properties of the cured networks was measured. © 1993 John Wiley & Sons, Inc. 相似文献
997.
Identification of inhibitory components toxic toward zymomonas mobilis CP4(pZB5) xylose fermentation 总被引:2,自引:0,他引:2
Thilini D. Ranatunga Judith Jervis Richard F. Helm James D. McMillan Christos Hatzis 《Applied biochemistry and biotechnology》1997,67(3):185-198
Zymomonas mobilis CP4(pZB5) is a recombinant bacterium that can produce ethanol from both xylose and glucose. The ethanol-producing efficiency
of this organism is substantially impeded by toxic substances present in pretreated hydrolyzates or solid biomass substrates.
Acetic acid and furfural (a pentose degradation product) are highly toxic to this organism at levels envisioned for a pretreated-hardwood
liquid hydrolyzate. In addition, lignin degradation products and 5-hydroxymethylfurfural (a hexose degradation product) have
a moderately toxic effect on the organism. Of the compounds studied, organic acids and aldehydes were found to be more inhibitory
than lignin acids or the one alkaloid studied. Acetone:water and methanol extracts of solid biomass samples from red oak,
white oak, and yellow poplar are toxic toZymomonas cell growth and ethanol production, with the extracts from white oak being the most toxic. 相似文献
998.
Trapp M Gutberlet T Juranyi F Unruh T Demé B Tehei M Peters J 《The Journal of chemical physics》2010,133(16):164505
We investigated molecular motions on a picosecond timescale of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) model membranes as a function of hydration by using elastic and quasielastic neutron scattering. Two different hydrations corresponding to approximately nine and twelve water molecules per lipid were studied, the latter being the fully hydrated state. In our study, we focused on head group motions by using chain deuterated lipids. Information on in-plane and out-of-plane motions could be extracted by using solid supported DMPC multilayers. Our studies confirm and complete former investigations by Ko?nig et al. [J. Phys. II (France) 2, 1589 (1992)] and Rheinsta?dter et al. [Phys. Rev. Lett. 101, 248106 (2008)] who described the dynamics of lipid membranes, but did not explore the influence of hydration on the head group dynamics as presented here. From the elastic data, a clear shift of the main phase transition from the P(β) ripple phase to the L(α) liquid phase was observed. Decreasing water content moves the transition temperature to higher temperatures. The quasielastic data permit a closer investigation of the different types of head group motion of the two samples. Two different models are needed to fit the elastic incoherent structure factor and corresponding radii were calculated. The presented data show the strong influence hydration has on the head group mobility of DMPC. 相似文献
999.
Judith Vancostenoble 《Acta Mathematica Hungarica》2000,89(1-2):71-92
We study the controllability problem of the one-dimensional damped wave equation $$\rho {\text{(}}x{\text{)}}u_{tt} - \frac{d}{{dx}}{\kern 1pt} {\kern 1pt} {\kern 1pt} \left( {p(x)u_x } \right){\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} + {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} 2d(x)\rho (x)u_t + q(x)\rho (x)u = h(x,t),{\text{ }}x \in {\text{(0,1)}}$$ This equation describes the forced motion of a nonhomogeneous string subject to a viscous damping. It is proved that the solution can be exactly controlled in finite time by means of distributed control forces h which vanish outside of any fixed nonempty subinterval of (0, 1). Moreover the optimal time of controllability is given. 相似文献
1000.
Hölbling M Masters SL Flock M Baumgartner J Hassler K Robertson HE Wann DA 《Inorganic chemistry》2008,47(8):3023-3033
Ab initio calculations were carried out to investigate the potential-energy surface for internal rotation of the methylated digermanes hexamethyldigermane Me(3)GeGeMe(3) ( 1), dichlorotetramethyldigermane Me(2)ClGeGeClMe(2) ( 2), and tetramethyldigermane Me(2)HGeGeHMe(2) ( 3). Different basis sets [6-31+G(d), SDD, aug-cc-pVTZ] were employed at the DFT and MP2 levels of theory to optimize structures and to calculate energies and vibrational frequencies. For 1, one minimum representing a staggered structure was located on the potential-energy surface. For 2 and 3, antiperiplanar conformations with C 2 symmetry were found to be the global minima. Additionally, synclinal minima were located for 2 and 3 when certain basis sets were employed. Determination of structural parameters in the gas phase by gas electron diffraction confirmed the computed predictions for all three compounds. For 2 and 3, the ratios of antiperiplanar to synclinal conformer were detected to be 90:10 (328 K) and 72:28 (293 K), respectively, by gas electron diffraction. The experimentally determined GeGe bond lengths in 1, 2, and 3 in the gas phase are 241.4(1), 242.7(2) (averaged for antiperiplanar and synclinal), and 241.7(1) pm (equal for antiperiplanar and synclinal). Only averaged structures were observed, using Raman spectroscopy, for 2 and 3 because the wavenumber differences are small between conformers and there is only a small contribution from the second conformer in each case. For 2, the crystal structure was also determined by X-ray diffraction. An anticlinal structure (with Cl atoms eclipsing the C atoms) was found with a GeGe bond length of 242.1 pm. 相似文献