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排序方式: 共有116条查询结果,搜索用时 240 毫秒
1.
通过测定不同类型的单一及复配型表面活性剂水溶液的临界胶束浓度和表面张力,研究了它对W(甲维盐)=1%微乳剂的性能影响。膦酸酯类阴离子表面活性剂A的临界胶束浓度为1.79×10-4mol/L,表面张力为28.90mN/m;苯乙烯基酚聚氧乙烯聚氧丙烯醚嵌段型非离子表面活性剂B(EPE型)的临界胶束浓度为1.91×10-4mol/L,表面张力为20.70mN/m;按m(A)∶m(B)=2∶3形成的复配型表面活性剂2#的水溶液的临界胶束浓度为9.30×10-5mol/L,表面张力为25.66mN/m。当W(2#)=10%时,配制W(甲维盐)=1%的微乳剂物理稳定性最佳,各项指标均合格。对甘蓝小菜蛾幼虫的田间药效的试验,结果表明该药剂具有较强的杀虫作用和较长的持效期,具有较好的推广应用前景。 相似文献
2.
Christakopoulos P Katapodis P Hatzinikolaou DG Kekos D Macris BJ 《Applied biochemistry and biotechnology》2000,87(2):127-133
An α-l-arabinofuranosidase from Fusarium oxysporum F3 was purified to homogeneity by a two-step ion exchange intercalated by a gel filtration chromatography. The enzyme had
a molecular mass of 66 kDa and was optimally active at pH 6.0 and 60°C. It hydrolyzed aryl α-l-arabinofuranosides and cleaved arabinosyl side chains from arabinoxylan and arabinan. There was a marked synergistic effect
between the α-l-arabinofuranosidase and an endo-(1 →4)-β-d-xylanase produced by F. oxysporum in the extensive hydrolysis of arabinoxylan. 相似文献
3.
In an earlier binding study conducted in our laboratory using Thermobifida fusca cellulases Cel6B, Cel9A, and Cel5A (formally Thermomonospora fusca E3, E4, and E5), it was observed that binding capacities for these three cellulases were 18–30 times higher on BMCC than on Avicel. These
results stimulated an interest in how the difference in accessibility between the two cellulosic substrates would affect synergism
observed with cellulase mixtures. To explore the impact of substrate, accessibility on the extent of conversion and synergism,
three binary T. fusca cellulase mixtures were tested over a range of cellulase ratios and total molar cellulase concentrations on Avicel and BMCC.
Higher extents of conversion were observed for BMCC due to the higher enzyme to substrate ratio resulting from the higher
binding The processive endoglucanase, Cel9A, had four times the extent of conversion of the end endocellulase Cel5A, while
the exocellulase Cel6B had three times the extent of conversion of Cel5A. Approximately 500 nmol/g of the cel9A+Cel6B mixture
was needed to obtain 80% conversion, while the Cel6B+Cel5A and Cel9A+Cel5A mixtures required 1500 and 1250 nmol/g, respectively,
to obtain 80% conversion. Thus, it appears that the more accessible structure of BMCC, as reflected by its binding capacity,
results in relative higher processive activity. 相似文献
4.
It is commonly observed that the rate of enzymatic hydrolysis of solid cellulose substrates declines markedly with time. In
this work the mechanism behind the rate reduction was investigated using two dominant cellulases of Trichoderma reesei: exoglucanase Cel7A (formerly known as CBHI) and endoglucanase Cel7B (formerly EGI). Hydrolysis of steam-pretreated spruce
(SPS) was performed with Cel7A and Cel7B alone, and in reconstituted mixtures. Throughout the 48-h hydrolysis, soluble products,
hydrolysis rates, and enzyme adsorption to the substrate were measured. The hydrolysis rate for both enzymes decreases rapidly
with hydrolysis time. Both enzymes adsorbed rapidly to the substrate during hydrolysis. Cel7A and Cel7B cooperate synergistically,
and synergism was approximately constant during the SPS hydrolysis. Thermal instability of the enzymes and product inhibition
was not the main cause of reduced hydrolysis rates. Adding fresh substrate to substrate previously hydrolyzed for 24 h with
Cel7A slightly increased the hydrolysis of SPS; however, the rate increased even more by adding fresh Cel7A. This suggests
that enzymes become inactivated while adsorbed to the substrate and that unproductive binding is the main cause of hydrolysis
rate reduction. The strongest increase in hydrolysis rate was achieved by adding Cel7B. An improved model is proposed that
extends the standard endo-exo synergy model and explains the rapid decrease in hydrolysis rate. It appears that the processive
action of Cel7A becomes hindered by obstacles in the lignocellulose substrate. Obstacles created by disordered cellulose chains
can be removed by the endo activity of Cel7B, which explains some of the observed synergism between Cel7A and Cel7B. The improved
model is supported by adsorption studies during hydrolysis. 相似文献
5.
Mahmoud M. Al Omari Mohammad B. Zughul J. Eric D. Davies Adnan A. Badwan 《Journal of inclusion phenomena and macrocyclic chemistry》2006,54(3-4):159-164
Ternary complexes exploiting solubility synergism (SSn) between basic drugs and β-cyclodextrin (β-CD) in the presence of an organic hydoxy acid have been reported to provide the pharmaceutical technology with highly soluble ternary complexes, even with the least soluble β-CD. In this work, phase solubility techniques were used to study factors affecting SSn in aqueous solution, which may help in understanding the mechanism involved in ternary complex formation in solution, under equilibrium conditions. The equilibrium solubility of both β-CD and each of 8 structurally unrelated drugs were measured in tandem in the presence of different acid types at low and high pHs, and at different time intervals over a period of 1–40 days. The results indicate that SSn is evident regardless of acid type (organic and inorganic) at low pH, but the extent of SSn is acid type dependant and is limited by the drug salt solubility product constant (pK
sp). Among different drugs, no apparent trend exists between drug salt solubility and the extent of SSn, but lowering drug salt solubility by increasing pH depresses SSn. The results also reveal no apparent trend between the magnitude of the complex formation constant (K
ij) and SSn. For example, drugs of low K
ij values such as astemizole, cisapride and sildenafil do not show any SSn, yet ketotifen and pizotifen, which also have low K
ij values, exhibit substantial SSn. However, the solublizing power of β-CD represented by the slope of phase solubility diagram can be used as a marker for SSn (slopes exceeding 0.4 induce SSn). 相似文献
6.
A 1,4-β-d-glucan cellobiohydrolase (EC 3.2.1.91) and l,4-β-d-glucan glucanohydrolase (EC 3.2.1.4) were purified from the culture filtrates ofPenicillium funiculosum by using preparative isoelectric focusing. Both the enzymes were homogeneous on polyacrylamide gel with and without sodium
dodecyl sulphate. The mol wt of the cellobiohydrolase and endoglucanase were 14,400 and 25,000 respectively. The purified
enzymes were free of β-glucosidase activity. Acting in isolation, the cellobiohydrolase had little capacity for solubilizing
Avicel or Walseth cellulose, but showed increased rates of hydrolysis when combined with endoglucanase. Cellobiose inhibition
(50%) was observed in the initial rate of the hydrolysis of Walseth cellulose. It was also observed that cellobiohydrolase
initiates the attack on crystalline cellulose.
† NCL communication no. 3898. 相似文献
7.
8.
Li-cheng Wang Shu-juan Liu Ji-chao Zhang Zhen-quan Li Lei Wang 《Journal of Dispersion Science and Technology》2014,35(2):307-312
In order to study the synergism between alkybenzene sulfonate and alkybenzene sulfonate, five di-n-alkylbenzene sulfonates were used and the interfacial tensions of single sulfonates and their binary mixtures against a series of alkane homologues were measured. The effects of hydrophilic-lipophilic abilities of sulfonates and mixing ratio on synergism were discussed. It is revealed that the synergistic mechanism derives from the amelioration of the hydrophilic-lipophilic ability of the surfactant system, and the method to achieve synergism is adding the hydrophilic alkybenzene sulfonate to the lipophilic alkylbenzene sulfonate, and ultralow interfacial tensions can be obtained in proper mixing ratios. The results are useful for enhanced oil recovery. 相似文献
9.
Daniel Hernández-Valdés Ricardo Fernández-Terán Benjamin Probst Bernhard Spingler Roger Alberto 《Helvetica chimica acta》2020,103(10):e2000147
Reduction of CO2 to CO and H2O is a two electron/two proton process. For this process, multinuclear complexes offer advantages by concentrating reduction equivalents more efficiently than mononuclear systems. We present novel complexes with [Re(η6-C6H6)2]+ as scaffold conjugated to one or two catalytically active [Ru(dmbpy)(CO)2Cl2] subunits (dmbpy=5,5′-dimethyl-2,2′-bipyridine). The [Re(η6-C6H6)2]+ scaffold was chosen due to its very high photo- and chemical stability, as well as the multiple degrees of freedom it offers for any conjugated functionalities. High efficiency and selectivity for the reduction of CO2 to CO (over H2 or HCOOH) is reported. TONs and TOFs were found to be comparable or higher than for the catalyst subunit without the rhenium framework. Cooperativity in photo- and electrocatalysis is observed for the complex comprising two catalytic subunits. The synergistic communication between the two catalytic subunits is responsible for the observed enhancement in both photo- and electrocatalytic performance. Confirmation of electronic communication between the two [Ru(dmbpy)(CO)2Cl2] subunits as well as the elucidation of a possible mechanism was supported by electrochemistry, IR-spectroelectrochemistry and DFT studies. 相似文献
10.
An electron gas in crossed electric and magnetic fields of arbitrary strength is considered in the framework of nonequilibrium
statistical mechanics. It is known that more than one independent frequency existing in a system, which are of comparable
magnitude, can generate coherent synergic radiation. In the present system three independent frequencies exist: viz the synchrotron
frequency due to the magnetic field, the hopping frequency due to the electric field, and the plasma frequency. It is shown
that all these can combine to generate a new synergic coherent radiation. The results also show the possibility of interpreting
the quantum nature of Hall conductance as due to density function alone. Besides these, the solution admits the Schubnikov-de
Haas oscillation of the electrical conductivity due to change in the fields. 相似文献