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61.
A new coruleoellagic acid derivative, 3,3′,4,4′,5′-pentamethylcoruleoellagic acid (1) together with nine known compounds, hexamethylcoruleoellagic acid (2), 3,4,3′-tri-O-methylellagic acid (3), heptaphylline (4), 7-methoxymukonal (5), dentatin (6), sinapaldehyde (7), gallic acid (8), 2,6-dimethoxy-4H-pyran-4-one (9) and β-sitosterol (10) were isolated from the stems of Rhodamnia dumetorum. Their structures were identified by physical and spectroscopic data (IR, 1D and 2D NMR, and MS). Compounds 1, 2 and 7-10 were tested for antibacterial activity against six pathogenic bacterial strains (Bacillus cereus, Escherichia coli, Pseudomonas aeruginosa, Salmonella enterica serovar Typhimurium, Staphylococcus aureus, and Methicillin resistant S. aureus (MRSA)). 相似文献
62.
63.
Maria E. A. De Carvalho M. C. Monteiro G. L. Sant'Anna Jr. 《Applied biochemistry and biotechnology》1999,79(1-3):723-733
The enzyme laccase was produced by the white-rot fungus Trametes versicolor in repeated batches cultures with immobilized mycelium. Two different culture conditions were used. Enzymes produced were
evaluated regarding their stability a thigh temperatures (55°C and 65°C) and at alkaline conditions (pH 7.0 and pH 8.0) having
in view the application of these enzymes in biobleaching of hardwood Kraft pulp.
Biobleaching experiments were divided in two parts, enzymatic prebleaching followed by chemical bleaching. In the enzymatic
prebleaching the enzyme laccase was used at two conditions of pH and temperature, whereas the reaction time was fixed at 1h
in all pretreatments. In the chemical bleaching the DEDED and DEpDED sequences were used.
The enzyme action was evaluated by Kappa number, viscosity, and brightness at the end of bleaching sequences. There were obtained
values of Kappa numbers lower than control assays, viscosities compatible with industrial pulps, and brightness higher than
controls, when pulps were pretreated for 1 h with laccase at pH 8.0 and 55°C. 相似文献
64.
“Thermometers” of speculative frenzy 总被引:1,自引:0,他引:1
65.
We study two types of generalized Baxter–Wu models, by means of transfer-matrix and Monte Carlo techniques. The first generalization allows for different couplings in the up- and down-triangles, and the second generalization is to a q-state spin model with three-spin interactions. Both generalizations lead to self-dual models, so that the probable locations of the phase transitions follow. Our numerical analysis confirms that phase transitions occur at the self-dual points. For both generalizations of the Baxter–Wu model, the phase transitions appear to be discontinuous. 相似文献
66.
This paper describes electrochemical behavior of laccase from the fungus Trametes versicolor. The issues related to discrimination of the redox potentials corresponding to copper centers T1 and T2/T3 in the active site and possible mechanism of intramolecular electron transfer have been discussed. The electron‐transfer rate constant for laccase immobilized on carbon electrode is 3.4 s?1. The bioelectrocatalytic activity of the enzyme was studied in the presence of 1,4‐hydroquinone (HQ). The kinetics of HQ oxidation is very fast (KM=3.8 μM). However, the catalytic activity of laccase in the presence of high concentration of HQ decreases drastically. It is suggested that the T2/T3 copper center is able to accept electrons from HQ molecules directly via intramolecular channel. 相似文献
67.
由野生及突变株云芝IBL-04制得细胞外锰过氧化物酶(MnPs),并经过硫酸铵沉淀、透析、离子交换和凝胶渗透层析法等步骤提纯.纯化的酶在十二烷基硫酸钠-聚丙烯酰胺凝胶电泳(SDS-PAGE)上于43 kDa区域呈现单一谱带,它适宜的pH值和温度分别为5.0和40°C.突变株MnPs表现出比野生株MnPs更宽的活性pH值范围和更高的热稳定性.从所选突变株所得纯化的MnPs表现出与野生株MnP几乎相同的电泳性质、稳态动力学、金属离子和EDCs降解效率.该生物酶与Mn2+一起催化的反应速率最快,但最高的亲和性对应于ABTS、甲氧基羟苯基乙二醇、4-氨基苯酚和活性染料. Mn2+和Cu2+可显著提高MnPs的活性,但Zn2+, Fe2+, EDTA和半胱氨酸则会不同程度地抑制其活性, Hg2+是最强的活性抑制剂.所有来源的MnPs均可有效催化EDCs、壬基苯酚和二氯苯氧氯酚降解,处理3 h可除去80%以上,在MnPs-介质体系中可进一步提高到90%.综上,云芝MnPs生物酶具有较高的pH适用性和热稳定性、独特的Michaelis-Menten动力学参数和高的EDCs去除效率等特点,因而有望工业化应用. 相似文献
68.
3 -(CH2)21-SH) were investigated by IR-vis sum frequency generation (SFG). Well-ordered monolayers and films with submonolayer coverage
with a high number of gauche conformations were prepared on polycrystalline gold substrates. Exposure to a saturated mercury
atmosphere induces a major reorganization of the adsorbate phase indicated by a decrease of the average cant angle. Additionally,
well-ordered films show an increase of gauche defects upon amalgamation. In contrast, films with submonolayer coverage exhibit
an improvement of molecular order. The experiments suggest that amalgamation flattens the corrugation potential of the substrate
and yields a separation of the thiol layer into areas of low thiol density with highly disordered alkyl chains and of higher
density than on gold with an orientation of the molecules similar to what is observed on silver substrates.
Received: 13 November 1998 相似文献
69.
Leyla Gidi Jessica Honores José Ibarra María Jesús Aguirre Roxana Arce Galo Ramírez 《Electroanalysis》2022,34(7):1163-1173
In this work, the determination of gallic acid was performed using surface-renewable carbon paste electrodes fabricated with multi-walled carbon nanotubes (MWCNT) and a mixture of N-octylpyridinium hexafluorophosphate (OPyPF6) ionic liquid with mineral oil (MO) as binder. This system shows remarkable amperometric sensor characteristics and promotes a better electronic transfer. An electroanalytical study of gallic acid shows a linear range from 4.98±0.25 to 74.1±2.2 μmol L−1, with R2=0.9958 and an experiment a limit of detection of 2.70±0.08 μmol L−1 (S/N=3), and a sensitivity of 0.029 μA μmol−1 L. 相似文献
70.
The averaged spin-spin correlation function squared
is calculated for the ferro-magnetic random bond Potts model in two dimensions. The technique being used is the renormalization group plus conformal field theory. The results are of the E-expansion type fixed point calculation, E being the deviation of the central charge (or the number of components) of the Potts model from the Ising model value. Calculations are done both for the replica symmetric and the replica symmetry broken fixed points. The results obtained allow for numerical simulation tests to decide between the two different criticalities of the random bond Potts model. 相似文献