排序方式: 共有17条查询结果,搜索用时 31 毫秒
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Man-Yu Wang Hong-Ze Gang Lei Zhou Jin-Feng Liu Bo-Zhong Mu Shi-Zhong Yang 《国际化学动力学杂志》2020,52(2):99-108
The amidation of long-chain fatty acids is the key step for preparing surfactants with excellent interfacial activity. Gas chromatography–mass spectrometry was employed to detect the reactants and products in the direct amidation reactions. The conversion and the concentration of the amides in the reaction process were also investigated to determine the best catalyst, the reaction rate constants, and activation energy. It was identified that the amidation reaction of the long-chain phenyl fatty acid was a zero-order reaction and 3,4,5-trifluorophenylboronic acid was the most effective catalyst by which the activation energy reduced to 55.79 kJ/mol from 95.44 kJ/mol. The method can be applied to other long-chain fatty acids, saturated or unsatureated. The turning-over-temperature was 156°C, over which high yields can be achieved without any catalyst. These provide a reference for the preparation of long-chain fatty acid amides. 相似文献
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针对Gibbs系综狭缝空间的单原子分子吸附系统, 引入了分子间作用对数的校正因子对格子空间的密度泛函理论(LDFT, lattice density functional theory)进行了修正. 利用连续迭代的方法, 探讨了狭缝滞留吸附行为的微观机理. 对比了修正前后的LDFT理论对滞留吸附行为的预测结果, 发现差别较大. 原LDFT理论由于平均场近似的处理, 对滞留吸附行为预测存在系统误差. 相似文献
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Surfactin in methanol solution with acid would be spontaneously esterified into the mono- or dimethyl ester surfactin even at a temperature as low as 4 °C because there were two free carboxyl groups in the peptide loop of surfactin. Using trifluoroacetic acid as the catalyst, the esterification and the contents change in surfactin-C15, mono- and dimethyl ester surfactin-C15 with time were investigated at 4, 25, and 45 °C, respectively. The kinetic model was established for prediction of the esterification degree under experimental conditions. At 4, 25, and 45 °C, more than 10 % of the surfactin-C15 in methanol solution in the presence of 0.05 % trifluoroacetic acid was changed into the esterified surfactin-C15 after 37.6, 14.1, and 7.4 h, respectively. The maximum of intermediate of the mono-methyl ester surfactin-C15 was observed at 4, 25, and 45 °C after 25, 10, and 5 days, respectively. Our results indicated that the time for preparation should be strictly controlled to avoid an unexpected esterification of surfactin during its storage and experimental treatment, and the kinetic results could be adopted as the reference condition for preparation of monomethyl ester surfactin-C15. 相似文献
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Jin-Feng Liu Juan Yang Shi-Zhong Yang Ru-Qiang Ye Bo-Zhong Mu 《Applied biochemistry and biotechnology》2012,166(8):2091-2100
Surfactin produced by Bacillus subtilis has different variants, which are affected by the composition of substrate available. To demonstrate the effects of amino
acids on surfactin variants, B. subtilis TD7 was cultivated under the same conditions but with different amino acids supplied in media, respectively, and the type
as well as the proportion of surfactin variants produced was analyzed with electrospray ionization mass spectrometry and gas
chromatography–mass spectrometry. The result shows that the addition of different amino acids significantly influences the
proportion of surfactin variants with different fatty acids. When Arg, Gln, or Val was added to the culture medium of B. subtilis TD7, the proportion of produced surfactin variants with even β-hydroxy fatty acids significantly increased, while the addition
of Cys, His, Ile, Leu, Met, Ser, or Thr enhanced the proportion of surfactin variants with odd β-hydroxy fatty acids markedly.
This result may be of some reference value in enhancing the production of specific surfactin variants as well as in the research
on the relationship between culture media and the corresponding products of a certain bacterium. 相似文献
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Ji Wang Namir I. A. Haddad Shi-Zhong Yang Bo-Zhong Mu 《Applied biochemistry and biotechnology》2010,160(3):812-821
Brevibacillus brevis HOB1 was isolated from the formation water of an oil field and found to produce lipopeptides. The separation of lipopeptides was successfully achieved by reversed-phase high-performance liquid chromatography (HPLC) leading to nine separated peaks. The chemical structures of these lipopeptides were studied by means of electrospray ionization mass spectrometry (ESI-MS), gas chromatography-mass spectrometry (GC/MS), HPLC and electrospray ionization tandem mass spectrometry (ESI-MS/MS). As the results, all the lipopeptides had peptide parts with the same amino acid composition of Asp, Glu, Val, and Leu in the molar ratio 1:1:1:4, while the lipid part was composed of C13–C15 β-hydroxy fatty acids. As the sequence of fraction 1 was determined to be N-Glu-Leu-Leu-Val-Asp-Leu-Leu-C, the same as surfactin, they were proposed to be surfactin isoforms. Fraction 4 (C15 surfactin) exhibited a good surface activity of 26.8 mN/m with CMC of 9?×?10?6 M. Surfactin is a powerful biosurfactant possessing biological activities. As far as we know, Br. brevis is a new surfactin-producing species. 相似文献
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环脂肽氨基酸顺序的质谱测定 总被引:8,自引:1,他引:7
从一株枯草芽孢杆菌的培养液中分离得到一种生物表面活性剂,红外光谱、茚三酮显色及质谱分析表明它是一种具有环状结构的脂肽.质谱显示脂肽的脂肪酸部分为β-羟基脂肪酸;氨基酸分析表明肽部分由4个亮氨酸、1个天门东氨酸、1个缬氨酸和1个谷氨酸组成.利用串联飞行时间质谱测定了环脂肽的分子量及质谱图.根据分子量的氮规则和质谱碎片产生的简单断裂、双氢转移机制、McLafferty等单氢重排机制,直接确定了未水解的环脂肽中脂肪链的长度以及氨基酸连接的顺序.质谱中的峰可以得到合理解释.确定了该环脂肽的环状结构. 相似文献
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修正的格子空间的密度泛函理论在狭缝中的应用 总被引:2,自引:0,他引:2
对描述单原子分子溶液在狭缝中的吸附现象的格子空间的密度泛函理论 (LDFT, lattice density functional theory)进行了修正, 在系统Helmholtz函数的推导中引入了平均场近似校正和Gibbs-Helmholtz方程. 对比Monte Carlo (MC)模拟结果, 发现LDFT理论对吸附分子在狭缝中的吸附浓度分布的预测与模拟数据有较大的偏差, 而修正模型的结果与模拟数据吻合较好 .随着体相浓度的变化,分子在狭缝中具有多级吸附行为, 具体表现为在特定体相浓度区, 对相同的体相浓度,狭缝中同时存在不同的分子浓度分布, 而在Gibbs等温线上可以明显看出多级吸附的性质. 对比修正前后的结果发现,两者均可以预测多级吸附行为, 但仍存在着较大的差异. 相似文献