A high yield method for the direct amidation of long-chain fatty acids

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.     

原子荧光光谱法测定灵芝中汞

用双道原子荧光分光光度计,断续流动程序和消解体系,测定灵芝中的汞,试验回收率在89.2%-106.3%之间.     

表面活性素分子结构对其胶束化行为的影响

采用表面张力、界面张力、荧光、动态光散射(DLS)和冷冻刻蚀电镜(FF-TEM)等方法, 研究了由Bacillus subtilis HSO121所产生的一组表面活性素的胶束化行为. 通过对表面活性素溶液表面张力、表面活性素对水/正己烷界面张力的影响、表面活性素胶束微极性以及胶束粒径和形态的研究, 发现随着表面活性素脂肪链长度的增加, 其表界面活性增强, 溶液中趋向于形成更大的聚集体.     

狭缝滞留吸附性质的理论研究

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.     

Kinetic Modeling of Esterification Reaction of Surfactin-C15 in Methanol Solution

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.     

Effects of Different Amino Acids in Culture Media on Surfactin Variants Produced by <Emphasis Type="Italic">Bacillus subtilis</Emphasis> TD7

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.     

Structural Characterization of Lipopeptides from Brevibacillus brevis HOB1

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.     

氢化物发生-原子荧光法测定中药中痕量砷

采用HNO3—HCIO4体系消解中药样品，优化实验条件，建立了氢化物发生-原子荧光法测定中药中痕量砷的方法。砷的相关系数为0．9993，检出限为0．36μg／L，茶叶(GBW08505)验证结果与推荐值一致，相对标准偏差为0．89％。该方法灵敏、简便、快速、准确，对于实际样品的测定得到了满意的结果。     

环脂肽氨基酸顺序的质谱测定

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.     

Synthesis and biological evaluation of novel derivatives of desloratadine

Series of novel derivatives of desloratadine designed as arginine vasopressin receptor antagonists were synthesized and structurally characterized by melting points,~1H NMR and HRMS.Their in vivo diuretic activities were evaluated on rats,and several target compounds showed promising diuretic results, especially compounds 8,18,27 and 31.Further in vitro bonding assay and cAMP assay showed that these compounds had a higher affinity to vasopressin V2 receptor than VI a receptor.Our studies indicated that desloratadine may be an active substructure for novel arginine vasopressin receptor antagonist development.