低聚壳聚糖与α-丙氨酸/天冬酰胺的美拉德反应及其衍生物的抗氧化性能研究

研究低聚壳聚糖(COS)与α-丙氨酸/天冬酰胺的美拉德反应,考察了两个体系(低聚壳聚糖的羰基与氨基的物质量比均为1∶1)的pH、吸光度和荧光值的变化。醇沉法提取低聚壳聚糖衍生物CA和CN。对两种衍生物进行红外表征和分子量测定,并研究其对超氧阳离子O2-.、DPPH自由基的清除能力以及还原能力。结果显示:抗氧化能力强弱次序为CA>CN>COS,即美拉德反应后低聚壳聚糖衍生物抗氧化能力得到显著提高,且CA的抗氧化活性优于CN,表明与小分子氨基酸进行美拉德反应制得的壳聚糖衍生物具有更好的抗氧化性。     

基于与木糖进行美拉德反应的低聚壳聚糖衍生物的抗氧化性能研究

研究低聚壳聚糖与木糖的美拉德反应,考察了两种体系(低聚壳聚糖与木糖的质量比分别为1∶1和1∶3)反应过程中pH、吸光度及荧光值的变化,醇沉法提取4 h和8 h的低聚壳聚糖美拉德反应衍生物,分别为CX11-4、CX13-4、CX11-8和CX13-8。对衍生物进行红外表征和分子量测定,并研究其对羟基自由基.OH和DPPH的清除能力以及还原能力。结果显示:壳聚糖衍生物的抗氧化能力都明显优于低聚壳聚糖,抗氧化活性顺序为CX13-4>CX11-4,CX11-8>CX13-8。可见,壳聚糖美拉德衍生物的抗氧化活性不仅与反应物的比例有关,还与反应的时间有关。     

硫脲壳聚糖Zn(Ⅱ)配合物的制备、表征及生物活性

利用FT-IR、UV、TG-DTA和XRD手段,对合成的硫脲壳聚糖及硫脲壳聚糖-Zn(Ⅱ)配合物进行了表征,研究了壳聚糖、硫脲壳聚糖及硫脲壳聚糖-Zn(Ⅱ)配合物对细菌大肠杆菌、金黄色葡萄球菌和真菌黑曲霉的抑菌性能.结果表明:合成的硫脲壳聚糖-Zn(Ⅱ)配合物对大肠杆菌、金黄色葡萄球菌的抑菌性能比单一的壳聚糖、硫脲壳聚糖显著提高,对真菌黑曲霉亦具有较强的抑制作用.     

钝节拟丽藻抑菌作用及提取条件的优化

研究了钝节拟丽藻提取液的抑菌作用,优化了提取条件。结果表明,钝节拟丽藻乙醇提取液对金黄色葡萄球菌、枯草杆菌有明显抑制作用,对大肠杆菌、变形杆菌、酿酒酵母和黄曲霉无明显抑制作用。通过抑菌圈直径方法,对影响钝节拟丽藻抑菌物质提取的条件进行了单因素试验。正交试验中的固液比和提取温度影响样品提取液对金黄色葡萄球菌和枯草杆菌的抑菌效果,作用极显著,其交互作用对金黄色葡萄球菌和枯草杆菌的抑菌效果作用显著。最佳提取条件为固液比1∶20,提取温度85℃,50%乙醇溶剂,回流提取6 h。     

几种天然产物的抑菌性能研究

将羧甲基壳聚糖等四种天然产物作为供试样,分别测定其对大肠杆菌、金黄色葡萄球菌、绿脓杆菌、枯草杆菌的最低抑菌浓度,结果表明,四种供试样对其均有一定的抑制作用,其中壳寡糖对大肠杆菌、金黄色葡萄球菌、枯草杆菌的抑制作用最强,羧甲基壳聚糖、壳寡糖、白芨多糖对绿脓杆菌的抑制能力差不多。再根据单体实验结果,选择羧甲基壳聚糖、壳寡糖、白芨多糖进行两两复配实验,结果表明,壳寡糖与白芨多糖的复配液对于金黄色葡萄球菌、枯草杆菌有较明显的协同增效抑菌作用。     

壳聚糖中胺基对其抑菌性能的影响及与DNA的作用

采用抑菌圈法研究了壳聚糖对大肠杆菌(E.coli)和金黄色葡萄球菌(St.aureus)的抑菌活性。利用壳聚糖的席夫碱反应,对壳聚糖的胺基进行保护后,研究了壳聚糖中胺基对其抑菌性能的影响。同时,运用紫外吸收光谱和电化学的方法,研究了壳聚糖与DNA的相互作用,提出了壳聚糖对E.coli和St.aureus的抑菌机理。研究结果表明,壳聚糖对E.coli和St.aureus具有很好的抑制作用,且抑菌活性与其胺基有关;壳聚糖能与细胞内带负电的核酸结合,使细胞正常DNA复制生理功能受到影响,抑制细菌的繁殖,从而达到抑菌的目的。     

不同分子量壳聚糖对五种常见茵的抑制作用研究

体外抑菌法研究了六种不同相对分子量的壳聚糖对金黄色葡萄球菌、大肠杆菌、绿脓杆菌、白色念珠菌、变形杆菌的抑菌活性,并对壳聚糖的抑菌机理做了探讨.     

壳聚糖微球分散体系的抑菌性研究

以乳化交联法制备的壳聚糖微米微球(CMs)为试验材料,研究其对金黄色葡萄球菌和大肠杆菌的抑菌行为,并对其浓度因素、粒径因素和抑菌机理做了探讨。结果表明CMs的抑菌作用随其浓度的增加和粒径的减小而增强。在浓度<0.7 mg/mL时,CMs对细菌的生长具有先抑制后促进的作用;当浓度≥0.7 mg/mL时对细菌有杀灭作用。CMs对两种细菌的最小抑菌浓度和最小杀菌浓度分别为0.8、1.4 mg/mL和1.0、1.8 mg/mL,表明壳聚糖微球对金黄色葡萄球菌和大肠杆菌均具有明显的抑制作用,且金黄色葡萄球菌对微球抑制作用的反应比大肠杆菌更敏感。扫描电子显微镜观察发现,细菌能迅速贴附在CMs表面,并且贴壁后的细菌发生了明显的形态变化,有的甚至完全被破坏。     

高活性壳聚糖的制备及特性

壳聚糖经100kGy60Coγ-射线辐射处理后,在0.01g/L的浓度下,对金黄色葡萄球菌生长抑制作用增强100倍.辐照剂量增加或减少,壳聚糖的抑菌活性均随之大幅降低.经辐射处理后形成的壳聚糖片段分子量小于10万,对金黄色葡萄球菌无明显抑制作用.     

中药金银花药用成分的提取及抑菌实验的研究

为了研究金银花中抗菌消炎成分总黄酮、绿原酸的提取方法及其抑菌效果,本实验中用金银花的提取物对11种菌种进行筛选,并对其中有抑制作用的菌种进行了最小抑菌浓度的实验。结果表明金银花的提取物对金黄色葡萄球菌和大肠杆菌有较强的抑制作用,对金黄色葡萄球菌的MIC为6．25mg／ml,对大肠杆菌的MIC为12．5mg／ml。     

抗凝蛋白EH体外活性检测条件的建立

EH蛋白是一种水蛭素衍生物,它是在水蛭素的N端引入了一小段寡肽,该寡肽可被凝血因子XIa(factor XIa,FXIa)和Xa(factor Xa,FXa)裂解释放水蛭素的抗凝血酶活性.比较在不同条件下FXa裂解EH蛋白的效果,包括裂解时间(2h,4h,6h,8h,10h,20h)、裂解温度(25℃,37℃,40℃)...     

Extraction, purification and antibacterial activities of a polysaccharide from spent mushroom substrate

To contribute towards effective exploitation and utilization of spent mushroom substrate (SMS), a water-soluble polysaccharide named PL was isolated and purified from SMS. The total sugar content and monosaccharide composition were analyzed by phenol-sulfuric acid method and capillary electrophoresis, and infrared spectroscopy was also performed for structure characterization. The results showed that the total sugar content of crude polysaccharide from SMS was about 25.8%, the polysaccharide contained two fractions (PL1 and PL2), which was mainly composed of glucose, rhamnose and mannose with a molar ratio of 1:3.13:1.16. The attributions of the main absorptions of both PL1 and PL2 were characteristic of glycosidic structures, and the FT-IR spectra of PL2 and lentinan were very similar. Escherichia coli, Staphylococcus aureus and Sarcina lutea were used to study the antibacterial activity and minimal inhibitory concentrations (MICs) of the polysaccharide. The antibacterial activity of polysaccharide from SMS against E. coli was the strongest, while the weakest against S. lutea, and the MICs of PL2 were 12.5, 25 and 100 μg/mL, respectively.     

Increased antibacterial activity of 15-residue murine lactoferricin derivatives.

LFM W8 is a synthetic 15-residue lactoferricin derivative (H2N-EKCLRWQWEMRKVGG-COOH), corresponding to residues 16-30 of the mature murine lactoferrin protein except that the asparagine residue in position 8 of the native peptide is replaced with tryptophan. We have previously reported that the two tryptophan residues in positions 6 and 8 are of crucial importance for the antibacterial activity of many lactoferricin derivatives but, despite fulfilling this requirement, LFM W8 is inactive against Escherichia coli and Staphylococcus aureus. In order to solve this puzzle, a quantitative structure-antibacterial activity relationship study of synthetic LFM W8 derivatives was performed by replacing the glutamate residues in positions 1 and 9 with arginine or alanine, and the valine residue in position 13 with tyrosine. The results from the study were analyzed using multivariate data analysis. The derived mathematical model clustered the peptides into distinct groups which reflected their antibacterial activities, pointed out correlations between different structural parameters, highlighted the structural parameters that were important for antibacterial activity, and enabled us to predict the activity of a 15-residue bovine lactoferricin derivative. The results showed that net charge and micelle affinity, as determined from the ratio of alpha-helicity in sodium dodecyl sulfate micelles and in 1,1,1,3,3,3-hexafluoro-2-propanol, were the most important structural parameters affecting antibacterial activity. The most active derivative, LFM R1,9 W8 Y13, displayed a minimal inhibitory concentration of 10 and 12 microM against E. coli and S. aureus, respectively. This represented more than 50-fold and 40-fold increases in antibacterial activity, respectively, compared with LFM W8.     

Cu/PAA的制备及其抗菌性能研究

采用两步阳极氧化法制备出孔径为75nm的多孔阳极氧化铝(PAA75),并使用交流电沉积技术在PAA75孔道内装载纳米Cu。采用场发射扫描电镜(FESEM)观察样品微观形貌,进一步采用X射线衍射(XRD)、X射线光电子能谱分析(XPS)对材料化学组成及晶型进行了表征和分析。选用大肠杆菌(E.coli ATCC 8099)和金黄色葡萄球菌(S.aureus ATCC6538)测试Cu/PAA的抗菌性能。研究结果表明,本方法制备的Cu/PAA中Cu主要以Cu0存在,并且Al和Cu所占原子比为17.77∶0.71。体外抗菌测试表明,Cu(10s)/PAA对E.coli的1d、2d和3d抑菌率分别为82%±11%、78%±7%和45%±4%,对S.aureus的1d、2d和3d抑菌率分别为89%±4%、75%±8%和56%±11%。     

Antibacterial activity of 15-residue lactoferricin derivatives.

Lactoferricins are a class of antibacterial peptides isolated after gastric-pepsin digest of the mammalian iron-chelating-protein lactoferrin. For investigation of antibacterial activity, we prepared short synthetic derivatives of bovine, human, caprine, murine and porcine lactoferricins with 15-amino-acid residues of high sequence homology. The peptides corresponded to amino-acid residues 17-31 of the mature bovine lactoferrin. Only the bovine and caprine derivatives displayed measurable antibacterial activity, with the bovine one having a minimal inhibitory concentration of 24 microM and being 10 times more active than the caprine one against Escherichia coli. An alanine-scan of the bovine lactoferricin derivative was performed to identify specific amino acids that were important for the antibacterial activity. We found that neither of the two tryptophan residues (Trp 6 and Trp 8) present in the bovine lactoferricin derivative could be replaced by alanine without a major loss of antibacterial activity. The other lactoferricin derivatives tested contained only one tryptophan residue (Trp 6). Modified human, caprine and porcine lactoferricin derivatives containing two tryptophan residues (Trp 6 and Trp 8) displayed minimal inhibitory concentrations of 74, 174 and 219 microM, respectively, which represented up to a six-fold increase in antibacterial activity. The alanine-scan also revealed that the antibacterial activity was increased when acetamidomethyl-protected cysteine and unprotected glutamine (Cys 3 and Gln 7) were replaced with alanine. Only the bovine lactoferricin derivative and a few of its alanine-modified derivatives displayed measurable activity against Staphylococcus aureus.     

桂皮酸-8-羟基喹啉稀土配合物的合成、抑菌活性及其对DNA的作用

以稀土离子为模板,用桂皮酸、8-羟基喹啉为原料,在乙醇溶液中首次合成了两种稀土三元配合物,采用元素分析、摩尔电导、红外光谱、紫外光谱和荧光光谱进行表征,并研究了配合物对常见细菌大肠杆菌和金黄色葡萄球菌的抑菌活性以及与DNA的相互作用.结果表明:配合物的抑菌活性较配体和稀土离子均有提高,能使细胞正常的DNA复制生理功能受到影响.     

The effects of charge and lipophilicity on the antibacterial activity of undecapeptides derived from bovine lactoferricin.

We have investigated the effects of charge and lipophilicity on the antibacterial activity of an undecapeptide (FKCRRWQWRMK) derived from the sequence of bovine lactoferricin. We prepared ten analogues that were modified by the incorporation of Ala, Tyr, Trp, Met and Arg residues, which are amino acids known to be important for the antibacterial activity of longer derivatives of lactoferricins. All undecapeptides contained the native Trp residues in positions 6 and 8, and the Arg residues in positions 5 and 9. Generally, the Gram-positive bacterium Staphylococcus aureus was more susceptible to these undecapeptides than the Gram-negative bacteria, and a higher antibacterial activity was observed against Escherichia coli than against Pseudomonas aeruginosa. The only exception was the peptide Undeca 9 (RRWYRWAWRMR-NH2), which was almost equally active against all three test strains, displaying minimal inhibitory concentrations of 10 microg/ml (5.8 microM), 7.5 microg/ml (4.4 microM) and 5 microg/ml (2.9 microM) against Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus, respectively. The peptides Undeca 6 (YRAWRWAWRWR-NH2) and Undeca 7 (YRMWRWAWRWR-NH2) were the two most active undecapeptides against Staphylococcus aureus, both displaying a minimal inhibitory concentration of 2.5 microg/ml (1.5 microM). The study showed that a level was reached in which undecapeptides having a net charge above +4 and containing three or four Trp residues all displayed a high antibacterial activity. All undecapeptides prepared were essentially non-haemolytic, but undecapeptides containing more than three Trp residues displayed 50% haemolysis of human red blood cells at concentrations above 400 microg/ml (>230 microM).     

Mannich reaction derivatives of novobiocin with modulated physiochemical properties and their antibacterial activities

Synthetic derivatives of the natural product antibiotic novobiocin were synthesized in order to improve their physiochemical properties. A Mannich reaction was used to introduce new side chains at a solvent-exposed position of the molecule, and a diverse panel of functional groups was evaluated at this position. Novobiocin and the new derivatives were tested for their binding to gyrase B and their antibacterial activities against Staphylococcus aureus, Mycobacterium tuberculosis, Francisella tularensis and Escherichia coli. While the new derivatives still bound the gyrase B protein potently (0.07-1.8 μM, IC(50)), they had significantly less antibacterial activity. Two compounds were identified with increased antibacterial activity against M. tuberculosis, with a minimum inhibitory concentration of 2.5 μg/ml.