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741.
Taylor EA Clinch K Kelly PM Li L Evans GB Tyler PC Schramm VL 《Journal of the American Chemical Society》2007,129(22):6984-6985
Transition state analogues of PNP, the Immucillins and DADMe-Immucillins, were designed to match transition state features of bovine and human PNPs, respectively. A third generation of inhibitors has been designed that contain an acyclic iminoalcohol to replace the cyclic mimic of the ribooxacarbenium ion at the transition states of PNPs. The best third generation inhibitor is equivalent to the best inhibitors found in the previous transition state analogues. 相似文献
742.
Reaction products resulting from small molybdenum suboxide cluster anions and carbon monoxide were studied with both mass spectrometry and anion photoelectron (PE) spectroscopy. In addition to the C6O6- product proposed previously, a number of unsaturated carbonyls were identified as terminal products in these reactions. A new PE spectrum of what may be C6O6-, in which the contribution from the Fe(CO)4- contaminant is subtracted, is reported. Additionally, the PE spectra of Mo(CO)5-, MoO(CO)3-, and MoO2(CO)n- (n=1 and 2) are presented, along with a new PE spectrum of an additional contaminant, Ni(CO)3-. Evidence of photodissociation of MoO(CO)3- to MoO-+3 CO is observed in the PE spectrum of MoO(CO)3-. 相似文献
743.
Ultrasound generated by means of laser-based photoacoustic principles are in common use today and applications can be found both in biomedical diagnostics, non-destructive testing and materials characterisation. For certain measurement applications it could be beneficial to shape the generated ultrasound regarding spectral properties and temporal profile. To address this, we studied the generation and propagation of laser-induced ultrasound in a planar, layered structure. We derived an analytical expression for the induced pressure wave, including different physical and optical properties of each layer. A Laplace transform approach was employed in analytically solving the resulting set of photoacoustic wave equations. The results correspond to simulations and were compared to experimental results. To enable the comparison between recorded voltage from the experiments and the calculated pressure we employed a system identification procedure based on physical properties of the ultrasonic transducer to convert the calculated acoustic pressure to voltages. We found reasonable agreement between experimentally obtained voltages and the voltages determined from the calculated acoustic pressure, for the samples studied. The system identification procedure was found to be unstable, however, possibly from violations of material isotropy assumptions by film adhesives and coatings in the experiment. The presented analytical model can serve as a basis when addressing the inverse problem of shaping an acoustic pulse from absorption of a laser pulse in a planar layered structure of elastic materials. 相似文献
744.
Martínez-López AL Carvajal-Millan E Lizardi-Mendoza J López-Franco YL Rascón-Chu A Salas-Muñoz E Barron C Micard V 《Molecules (Basel, Switzerland)》2011,16(10):8410-8418
The oxidative gelation of maize bran arabinoxylans (MBAX) using a peroxidase/H(2)O(2) system as a free radical-generating agent was investigated. The peroxidase/H(2)O(2) system led to the formation of dimers and trimer of ferulic acid as covalent cross-link structures in the MBAX network. MBAX gels at 4% (w/v) presented a storage modulus of 180 Pa. The structural parameters of MBAX gels were calculated from swelling experiments. MBAX gels presented a molecular weight between two cross-links (Mc), a cross-linking density (ρ(c)) and a mesh size (x) of 49 × 103 g/mol, 30 × 10-6 mol/cm3 and 193 nm, respectively. 相似文献
745.
Carvalho TC Simão MR Ambrósio SR Furtado NA Veneziani RC Heleno VC Da Costa FB Gomes BP Souza MG Borges dos Reis E Martins CH 《Molecules (Basel, Switzerland)》2011,16(1):543-551
Six pimarane-type diterpenes isolated from Viguiera arenaria Baker and two semi-synthetic derivatives were evaluated in vitro against a panel of representative microorganisms responsible for dental root canal infections. The microdilution method was used for the determination of the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) against Porphyromonas gingivalis, Prevotella nigrescens, Prevotella intermedia, Prevotella buccae, Fusobacterium nucleatum, Bacteroides fragilis, Actinomyces naeslundii, Actinomyces viscosus, Peptostreptococcus micros, Enterococcus faecalis and Aggregatibacter actinomycetemcomitans. The compounds ent-pimara-8(14),15-dien-19-oic acid, its sodium salt and ent-8(14),15-pimaradien-3β-ol were the most active, displaying MIC values ranging from 1 to 10 μg mL-1. The results also allow us to conclude that minor structural differences among these diterpenes significantly influence their antimicrobial activity, bringing new perspectives to the discovery of new chemicals for use as a complement to instrumental endodontic procedures. 相似文献
746.
Nakata S Matsushita M Sato T Suematsu NJ Kitahata H Amemiya T Mori Y 《The journal of physical chemistry. A》2011,115(26):7406-7412
The excitation of the photosensitive Belousov-Zhabotinsky (BZ) reaction induced by light stimulation was systematically investigated. A stepwise increase in the light intensity induced the excitation, whereas a stepwise decrease did not induce the excitation. The threshold values for the excitation were found to be a function of the initial and final light intensities, time variation in light intensity, and the concentration of NaBrO(3). The experimental results were qualitatively reproduced by a theoretical calculation based on a three-variable Oregonator model modified for the photosensitive BZ reaction. These results suggest that although the steady light irradiation is known to inhibit oscillation and chemical waves in the BZ system under almost all conditions, the stepwise increase in the light irradiation leads to the rapid production of an activator, resulting in the photoexcitation. 相似文献
747.
Danilo Addari Adriana Mignani Erika Scavetta Domenica Tonelli Antonella Rossi 《Surface and interface analysis : SIA》2011,43(4):816-822
In this work, a Ni/Al hydrotalcite (HT) was used as glucose oxidase (GOx) immobilizer. Small‐area and angle‐resolved X‐ray photoelectron spectra were recorded on HTs electrosynthesized on Pt in the absence and in the presence of GOx, and compared with those obtained for a Pt surface, modified with the electrosynthesized HT, on which a drop of GOx solution was deposited. The simultaneous electrodeposition of HT + GOx resulted in a compact deposit, thicker than the XPS sampling depth (>10 nm), that is not homogeneous in the lateral and in‐depth composition. The presence of GOx can be deduced comparing the N1s spectra of HT and HT + GOx: in the latter, the N1s component at 400 eV binding energy (BE) is predominant whilst, depending on the analyzed point, a small or no contribution from the component at 407.2 eV, due to nitrate, is revealed. Angle‐resolved XPS provides evidence on the in‐depth composition of anions, cations and GOx. The results highlight the crucial role played by nickel in GOx immobilization. On the basis of the results, it can be suggested that enzyme activity is unevenly distributed and is localized in small areas, where Ni concentration is higher. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
748.
van Hove ER Smith DF Fornai L Glunde K Heeren RM 《Journal of the American Society for Mass Spectrometry》2011,22(10):1885-1890
Surface treatment of biological tissue sections improves detection of peptides and proteins for mass spectrometry imaging.
However, liquid surface treatments can result in diffusion of surface analytes and fragile tissue sections can be easily damaged
by typical washing solvents. Here, we present a new surface washing procedure for mass spectrometry imaging. This procedure
uses solvent wetted fiber-free paper to enable local washing of tissue sections for mass spectrometry imaging and tissue profiling
experiments. In addition, the method allows fragile tissues that cannot be treated by conventional washing techniques to be
analyzed by mass spectrometry imaging. 相似文献
749.
Erika Scavetta Lorella Guadagnini Adriana Mignani Domenica Tonelli 《Electroanalysis》2008,20(20):2199-2204
An amperometric biosensor based on Pt electrodes modified with a thin film of a Ni, Al layered double hydroxide (LDH), submitted to a preliminary oxidative treatment in order to have the nickel centers at the oxidation state +4, and glucose oxidase (GOx) is presented. The oxidized LDH acts both as a system to support the enzyme and as a barrier to anions since it acquires an overall negative charge, as demonstrated by electrochemical impedance spectroscopy. Even if the biosensor response is due to the detection of H2O2 at anodic potentials, glucose can be accurately determined in the presence of ascorbic acid or other interferences, commonly present in real matrices in anionic form, since they can not reach the electrode surface. The effectiveness of the developed biosensor has been demonstrated by measuring glucose in samples of fruit juices containing ascorbic acid at high levels. 相似文献
750.
Erika Szunyogová Dagmar Mudroňová Katarína Györyová Radomíra Nemcová Jana Kovářová Lenka Piknová-Findoráková 《Journal of Thermal Analysis and Calorimetry》2007,88(2):355-361
Spectroscopic (IR), thermoanalytical (TG/DTG, DTA) and biological methods
were applied to investigate physicochemical and biological properties of seven
zinc(II) complex compounds of the following formula Zn(HCOO)2·2H2O
(I), Zn(HCOO)2·tph (II), Zn(CH3COO)2·2H2O (III), Zn(CH3COO)2·tph
(IV), Zn(CH3COO)2·2phen
(V), Zn(CH3CH2COO)2·2H2O
(VI), Zn(CH3CH2CH2COO)2·2H2O (VII), where tph=theophylline, phen=phenazone. The formation of various
intermediates during thermal decomposition suggests the dependence on the
length of aliphatic carboxylic chain and type of N-donor ligand (tph, phen).
The final product of the thermal decomposition was ZnO. The antimicrobial
activity of these complexes were tested against G+
and G– bacteria. Strong inhibitive effect
was observed towards E. coli, salmonellae
and Staph. aureus. 相似文献