Determination of epristeride by its quenching effect on the fluorescence of L-tryptophan

A rapid, novel spectrofluorimetric method to determine epristeride （EP） in biological fluids and a pharmaceutical formulation was developed, based on the fact that fluorescence intensity of L-tryptophan could be quenched by EP in the medium of pH=9.0. The various factors influencing fluorescence quenching were discussed. The quenching mechanism was investigated with the quenching type, synchronous fluorescence spectra and quantum efficiency. Under the optimized conditions, fluorescence quenching value （AF^---FL_tryptophan--FEP_L_tryptophan） showed a good linear relationship with the EP concentration ranging from 0.4 to 12.0 lag/mL. The linearity, recovery and limit of detection demonstrated that the proposed method was suitable for EP determination in biological fluids and EP tablets. The method was successfully applied to the analysis of EP in real samples and the obtained results were in good agreement with the results of the official method.

Co-ordinated combination of Embden-Meyerhof-Parnas pathway and pentose phosphate pathway in Escherichia coli to promote L-tryptophan production

In this study,phosphoenolpyruvate and erythrose-4-phosphate are efficiently supplied by collaborative design of Embden-Meyerhof-Parnas(EMP)pathway and pentose phosphate(PP)pathway in Escherichia coli,thus increasing the L-tryptophan production.Firstly,the effects of disrupting EMP pathway on L-tryptophan production were studied,and the results indicated that the strain with deletion of phosphofructokinase A(i.e.,E.coli JW-5ΔpfkA)produced 23.4±2.1 g/L of L-tryptophan production.However,deletion of phosphofructokinase A and glucosephosphate isomerase is not conducive to glucose consumption and cell growth,especially deletion of glucosephosphate isomerase.Next,the carbon flux in PP pathway was enhanced by introduction of the desensitized glucose-6-phosphate dehydrogenase(zwf)and 6-phosphogluconate dehydrogenase(gnd)and thus increasing the L-tryptophan production(i.e.,26.5±3.2 g/L vs.21.7±1.3 g/L)without obviously changing the cell growth(i.e.,0.41 h^(-1) vs.0.44 h^(-1))as compared with the original strain JW-5.Finally,the effects of co-modifying EMP pathway and PP pathway on L-tryptophan production were investigated.It was found that the strain with deletion of phosphofructokinase A as well as introduction of the desensitized zwf and gnd(i.e.,E.coli JW-5 zwf243 gnd361ΔpfkA)produced 31.9±2.7 g/L of L-tryptophan,which was 47.0%higher than that of strain JW-5.In addition,the glucose consumption rate of strain JW-5 zwf243 gnd361ΔpfkA was obviously increased despite of the bad cell growth as compared with strain JW-5.The results of this study have important reference value for the following application of metabolic engineering to improve aromatic amino acids producing strains.

Morphological Control of Gold Nanoparticles by Green Synthesis Using L-Tryptophan and Other Additives

This study focuses on shape-controlled synthesis of gold nanoparticles, using the green reducing agent L-Tryptophan(L-Trp), which is non-toxic and eco-friendly. This specific agent was investigated to realize certain morphology controlling effects by changing the relative growth rates among various crystal planes. Experimental samples were characterized by transmission electron microscope, UV-Vis spectrophotometer and X-ray diffraction(XRD) for size and morphological information. The effects of the specific additives of PVP((C_6 H_9 NO)_n), CTAB(C_(16)H_(33)(CH_3)_3 NBr), and KBr were examined for their morphological control individually and synergistically in this system. Hexagonal gold nanoparticles were successfully obtained via the PVP/CTAB and PVP/KBr systems. Particular amounts of PVP/KBr produced various polyhedron structures, such as cubes, and others with triangular and rhombic straight-side cross sections.

Gold Nanoparticles of Multiple Shapes Synthesized in L-Tryptophan Aqueous Solution

In this paper, we describe a simple and efficient synthesis of gold nanoparticles(GNPs) of various shapes(spherical, rod-like, hexagonal, truncated triangular, and triangular) using Au(Ⅲ) reduction in aqueous solutions by L-tryptophan. We evaluated the influences of reaction temperature, foreign metal ions Ag(Ⅰ), and surfactants of nonionic(polyethylene glycol, PEG), anionic(sodium dodecyl sulfate, SDS), and cationic(cetyltrimethyl ammonium bromide, CTAB) on GNPs synthesis. We characterized the resultant GNPs using UV–visible adsorption spectroscopy, transmission electron microscopy/high-resolution transmission electron microscopy, scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, selected-area electron diffraction, and Fourier-transform infrared spectroscopy. We fabricated the variously sized GNPs by controlling the rate of the reduction of gold ions in aqueous solution by varying the reaction temperature: the higher the temperature, the smaller the gold nanospheres. We found the existence of Ag(Ⅰ) to reinforce the reduction of Au(Ⅲ) and to correspond with the appearance of some amorphous bimetallic Au/Ag nanoparticles. Additionally, we found the presence of surfactants to greatly influence the shape of the formed GNPs, especially the presence of CTAB, which results in the anisotropic growth of gold nanocrystals into hexagonal, truncated triangular, and triangular nanoplates. In addition, with the increase in CTAB concentration, we found the amount of gold nanoplates to first increase and then decrease. Finally, we performed preliminary explorations of the reduction process and morphological evolution to propose possible corresponding reduction and morphological evolution pathways.

Synthesis of Coumarin-functionalized Calix[4]arene and Selective Recognition for L-Tryptophan

5,11,17,23-Tetra-tert-butyl-25, 27-bis（7＇-methoxycoumarin-3＇-methyloxy）-26, 28-dihydroxycalix[4]arene was synthesized and characterized. The derivative could recognize L-tryptophan with a 1：1 complexing ratio and an apparent equilibrium constant of 111 L mol^-1 in DMF acetonitrile as solvent by UV-visible and fluorescent spectrophotometry.

Study on Interaction of L-Tryptophan with p-Suffonatocalix[4]arene by Spectrofluorometry

The interactions between L-tryptophan（L-Trp） and water-soluble p-sulfonatocalix[4]- arene （SCX4） were investigated by spectrofluorometry. The effect of pH was discussed. The interaction process was estimated from the thermodynamic viewpoint. The SCX4 was found to be able to adjust its conformation to fit the size of L-Trp, and the benzene of L-Trp penetrated into the hydrophobic cavity of SCX4. Meanwhile, the binding mechanism was further elucidated by IHNMR and molecular mechanics calculations.

Syntheses,Crystal Structures and Anticoagulant Activities of Two L-tryptophan Derivatives

Two new L-tryptophan derivatives,（S）-2-（4-acetoxybenzamido）-3-（1 H-indol-3-yl）propanoic acid（I） and（S）-2-（3-acetoxybenzamido）-3-（1H-indol-3-yl）propanoic acid（II）, were synthesized and characterized by FT-IR, NMR and MS. The single crystals were cultivated and determined with X-ray diffraction. It was determined that the two compounds crystallized in monoclinic space group P21. Compound I（C（21）H（20）N2O5, Mr = 380.39） with a = 8.5227（6）, b = 7.8310（6）, c = 15.2527（11） A°, Z = 2, V = 1017.81（13） A°^3, μ = 0.090 mm^-1, Dc = 1.241 g/cm^3, F（000） = 400, the final R = 0.0412 and w R = 0.1170 for all data. Compound II（C（21）H（20）N2O5, Mr = 380.39） with a = 9.5112（5）, b = 9.2197（4）, c = 10.9115（5） A°, Z = 2, V = 952.13（8） A°^3, μ = 0.096 mm^-1, Dc = 1.327 g/cm^3, F（000） = 400, the final R = 0.0377 and w R = 0.1009 for all data. The anticoagulant activities of L-tryptophan derivatives were evaluated by plasma re-calcification time（PRT） and blood concretion four items（APTT, PT, TT and FIB）. The results exhibited that L-tryptophan derivatives showed anticoagulant activity in normal coagulation pathway.

Conversion of L-Tryptophan into Melatonin Is the Possible Action Pathway Involved in the Effect of L-Tryptophan on Antidepressant-Related Behavior in Female Rats: Analysis of the Influence of Treatment Duration

The aim of this study was to determine the effect of pharmacological doses of melatonin (MEL) and L-tryptophan (L-TRP) on depression-like behavior in female rats submitted to the forced swimming test (FST) after 2, 4, 6 or 8 weeks of treatment. This will allow exploring the different mechanisms of L-TRP actions particularly that due to its conversion into MEL. For this purpose, four groups of 24 rats each were constituted;(Group 1: Control): received saline solution NaCl (0.9%), (Group 2: MEL4): received 4 mg/Kg of MEL, (Group 3: L-TRP4): received 4 mg/Kg of L-TRP and (Group 4: L-TRP20): received 20 mg/Kg of L-TRP. Animals of each group were distributed on 4 subgroups of 6 rats submitted to different time treatments. The duration of immobility (TIM) and struggling period (TST) of rats in FST were measured after 2, 4, 6 and 8 weeks of drug treatment and the effects of MEL and L-TRP were compared. Chronical administration of different doses of MEL or L-TRP failed to induce any anti-depressant activity in rats subjected to FST after 2 weeks of treatment. However, after 4 weeks, daily administration of MEL at 4 mg/Kg significantly reduced the immobility period and enhanced struggling time. After 6 weeks, MEL at 4 mg/Kg and L-TRP at 20 mg/Kg were both effective in reducing immobility and increasing struggling movement, their effects being statistically comparable. All treatments were able to significantly reduce immobility time and increase struggling duration after 8 weeks, but L-TRP at 4 mg/Kg was less potent than MEL and L-TRP at 20 g/Kg. The antidepressant-like activity of L-TRP was dose and time dependent, and that of MEL was time dependent. In conclusion, the study showed that at pharmacological doses, MEL and L-TRP have anti-depressant action, and such effect is dependent on time treatment;MEL?is more effective than L-TRP. In conclusion, L-TRP, through MEL, 5-HT or by itself could modulate aminergic neurotransmission in the different brain areas to ensure its behavioral effects.

Lipid-Polymer Membranes as Carriers for L-Tryptophan: Molecular and Metabolic Properties

Polymerized liposomes encapsulating L-tryptophan were studied with the aim to characterize them as drug delivery systems for the treatment of several metabolic diseases that need an increased systemic L-tryptophan concentration. polymerized liposomes were obtained by UV irradiation of vesicles containing 1,2-bis(10,12-tricosadiynoyl)-sn-glycero-3-phosphocholine (DC8,9PC) and 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) in a 1:1 molar ratio, in the presence of 10 and 50 mol% of L-tryptophan (respect to total lipid concentration). Polymerization efficiency was studied spectrophotometrically. Also, bilayer packing at the polar head region was followed with the Merocyanine 540 (MC540) and specific interactions in the lipopolymers were studied by FTIR. High L-tryptophan concentrations (50 mol% respect to total lipid concentration) induced a higher amount of six- and nine-unit polymers. This phenomenon was induced because the L-tryptophan located outside the lipid membrane was included in it during the polymerization process and was thus responsible for the better accommodate of the polar head region. This was not possible with the lower amount of L-tryptophan (10 mol%). The stability of lipopolymers with different amounts of L-tryptophan was studied through release profiles. Polymerized liposomes with 50 mol% of L-tryptophan were able to retain around 80% of the amino acid after 24 hours, whereas those with 10 mol % of the amino acid were able to retain 20%. The metabolic activity of the Caco-2 cell line was also studied. Cytotoxic effects were low in the presence of polymerized liposomes, rendering a maximum percentage of cell death of 30%. In summary, this work stresses the relevance of nonspecific drug-polymerized membrane binding on L-tryptophan pharmacological interaction with possible pharmaceutical applications in liposomal drug delivery. Moreover, the absence of significant cytotoxic effects allows the system proposed to be applied in human health.

Effects of aroP gene disruption on L-tryptophan fermentation

The production of L-tryptophan through che- mical synthesis, direct fermentation, bioconversion and enzymatic conversion has been reported. However, the role of the transport system for the aromatic amino acids in L- tryptophan producing strains has not been fully explored. In this study, the atop gene of the L-tryptophan producing Escherichia coli TRTH strain was disrupted using Red recombination technology and an atoP mutant E. coli TRTH AaroP was constructed. Fed-batch fermentation of E. coli TRTH △aroP was carried out in 30-L fermentor to investigate the L-tryptophan production. Compared with E. coli TRTH, the atoP mutant was able to maintain a higher growth rate during the exponential phase of the fermentation and the L-tryptophan production increased by 13.3%.

乙酰乙酸纤维素膜的手性传输性质研究

选用价格较低且易得的微晶纤维素作为实验原料,用酯交换法与乙酰乙酸叔丁酯反应,通过控制反应时间制备不同取代度的乙酰乙酸纤维素(CAA),并利用溶剂挥发法制得CAA膜.通过^(1)H NMR、FTIR、SEM和TGA等测试CAA膜的化学结构、形貌和热稳定性.使用渗析器测试CAA膜对D,L-色氨酸的渗透拆分性质,利用二元高压梯度高效液相色谱测试渗透液中D-色氨酸和L-色氨酸的浓度.针对手性传输性质,研究了不同取代度的CAA膜对D,L-色氨酸的拆分机理.研究发现,低取代度的CAA膜有更好的手性拆分性能,而高取代度的CAA膜由于接触水溶液后自由体积增大,色氨酸容易通过渗透过膜,分离性能降低.经过对CAA膜对D-色氨酸和L-色氨酸的渗透、分配和扩散系数的分析可知,高取代度的CAA膜的手性拆分性能主要是由扩散控制.其中低取代度(DS=0.57)的CAA膜的对映体过量百分比在6 h内保持100%,超过6 h略微下降,之后趋于稳定.本研究通过简单的调控CAA的取代度制备了具有一定拆分性能的手性分离膜,为手性分离膜的设计提供了思路.

食用菌中L-色氨酸HPLC检测方法的建立

建立了高效液相色谱(high performance liquid chromatography,HPLC)测定食用菌中L-色氨酸含量的方法,并进行了方法学验证。采用Acclaim^(TM)120 C18色谱柱(4.6 mm×250 mm,5μm),以0.05 moL·L^(-1)乙酸钠缓冲液(用冰乙酸将pH调至4.0~5.0)和纯甲醇为流动相(体积比为70∶30)等度洗脱,流速为1.0 mL·min^(-1),检测波长为280 nm,柱温为30℃,进样量为20μL。结果显示L-色氨酸在4~100μg·mL^(-1)线性关系良好,R^(2)>0.9955。精密度、重复性、24 h内稳定性的相对标准偏差均小于15%(n=6),加标回收率为87.5%(相对标准偏差为0.63%)。说明建立的高效液相色谱检测方法简单、快速、灵敏度高、特异性强、分离度好,适用于食用菌中L-色氨酸含量的测定。

A Glassy Carbon Electrode Modified with Cellulose Nanofibrils from Ammophila arenaria for the Sensitive Detection of L-Trytophan

L-tryptophan is an essential amino acid for human health. Nanofibrillated cellulose (NFC) from marram grass (Ammophila arenaria) extracted from plants harvested in the center of Tunisia was used for the first time for the modification of a glassy carbon electrode (GCE), for the sensitive detection of L-tryptophan (Trp). After spectroscopic and morphological characterization of the extracted NFC, the GC electrode modification was monitored through cyclic voltammetry. The NFC-modified electrode exhibited good analytical performance in detecting Trp with a wide linear range between 7.5 × 10−4 mM and 10−2 mM, a detection limit of 0.2 µM, and a high sensitivity of 140.0 µA∙mM−1. Additionally, the NFC/GCE showed a good reproducibility, good selectivity versus other amino acids, uric acid, ascorbic acid, and good applicability to the detection of Trp in urine samples.

基于纳米四氧化三铁改性的电化学传感器的构建及用于色氨酸检测的研究

色氨酸是人体内最重要的氨基酸,在人类生长发育中起着关键作用.本研究通过在碳布(CC)表面修饰纳米四氧化三铁(Fe_(3)O_(4)NMs),制备了一种基于Fe_(3)O_(4)NMs/CC的高灵敏度电化学传感器,用于色氨酸样本的检测.纳米Fe_(3)O_(4)为传感器提供了大电化学面积和高电催化性能,由于电极传质通道的增加,检测灵敏度得到显著提升.通过差分脉冲伏安法(DPV)检测不同浓度色氨酸产生的电流峰,在最优条件下,Fe_(3)O_(4)NMs/CC传感器对色氨酸的检测限(LOD)为1.68μM,检测线性浓度范围为5~200μM,灵敏度增加为1.01 mA/M·cm^(2).此外,对血清和尿液等样品的检测中,基于Fe_(3)O_(4)NMs/CC传感器也显示出良好的准确性和稳定性,说明该体系有可用于即时检测的潜力.

陶瓷超滤膜在5-羟基-L-色氨酸发酵产物提取中的应用

为提高5-羟基-L-色氨酸(5-hydroxy-L-tryptophan,5-HTP)提取分离效率,降低能耗和污染排放,选择陶瓷超滤膜应用于从发酵液中提取5-HTP的工艺,对陶瓷超滤膜的过滤条件进行优化.首先优选出适合的膜孔径为10 nm,进一步优化得到陶瓷超滤膜分离提取5-HTP的3个最优工艺参数:发酵液pH值3.5,跨膜压差0.75 MPa,料液过膜温度35℃.在此工艺条件下,5-HTP的透过率在92%以上,对游离蛋白质截留率达90%以上,满足进一步浓缩、结晶制备5-HTP的要求,达到了优化预期效果,为陶瓷超滤膜应用于从发酵液中工业化提取5-HTP提供了可靠依据.

L-色氨酸与结冷胶复配对瓦斯水合物生成动力学影响

为加快煤矿瓦斯高效清洁利用,利用静态甲烷水合物合成实验装置,在NiMnGa悬浮液中开展了结冷胶和L-色氨酸不同配比条件下的瓦斯水合过程动力学影响实验,探究结冷胶与L-色氨酸对瓦斯水合物生成动力学影响。结果表明:在质量分数为0.03%的L-色氨酸体系中,随着结冷胶质量分数的升高,水合物气体消耗量和气体消耗速率均降低,0.3%结冷胶体系促进效果较好,是0.6%体系气体消耗量的5.8倍;在结冷胶质量分数为0.3%的体系中加入少量L-色氨酸能够促进甲烷水合物生成动力学进程,0.5%L-色氨酸体系比单独结冷胶体系诱导时间缩短了95.56%,气体消耗量和气体消耗速率分别提高了22.9倍和36.1倍。该研究可为静态体系促进气体水合物快速生成提供参考。

可溶性油类和溶解性有机物对砂加载混凝沉淀处理高悬浮矿井水效果的影响

矿井水中可溶性油类和溶解性有机物含量对石英砂加载混凝沉淀效果的影响很少有系统的研究,影响机制也不清晰。为此,选用石英砂加载混凝处理高悬浮矿井水为研究对象,分析矿井水中乳化油、浓缩液、腐殖酸(humic acid,HA)、富里酸(fulvic acid,FA)和L-色氨酸(L-tryptophan,LA)含量对石英砂加载混凝处理高悬浮物矿井水效率的影响。分析结果表明:矿井水中乳化油、浓缩液和过量的HA含量不利于加载混凝沉淀处理的效率和沉淀速率。HA、LA和适量的FA含量并不能影响加载混凝沉淀处理高悬浮物矿井水的效率和沉降速率。响应面分析结果表明乳化油和浓缩液的浓度变化对砂加载混凝沉淀效率和过程的影响较大,而HA、FA和LA的浓度变化则对其影响较小。该结果为进一步认知砂加载混凝处理工艺,提升其处理效率,实现中国煤矿矿井水资源保护和合理化利用具有重要的意义。

高光谱图像技术在酱油中L-色氨酸含量分析中的应用

以3种市售酱油为研究对象,利用二极管阵列检测器结合外标法定量考察酱油中L-色氨酸含量;基于偏最小二乘法进行酱油中L-色氨酸含量预测。结果表明,在最大吸收波长302 nm、流动相pH 5.0、柱温37℃、流速1.2 mL/min、流动相为甲醇比例12%、乙酸钠缓冲液含量0.015 mol/L的乙酸钠缓冲液-甲醇、氢氧化钠浓度0.015 mol/L下进行酱油中L-色氨酸含量检测时效果最优;在光谱范围462~506 nm、612~698 nm、794~858 nm之间时,校正集相关系数为0.9851,均方根误差为0.491;预测集相关系数为0.9873,均方根误差为0.373,其模型精度最高。利用高光谱图像技术可以快速有效地进行酱油中L-色氨酸含量的测定,其结果可为酱油分析提供理论依据和数据支持。

配体对白蛋白稳定性影响的研究进展

应对人血白蛋白制备与储存过程中复杂的温度、光照等条件,提高白蛋白的稳定性十分必要。本文从配体与白蛋白结合的角度,阐述了配体对白蛋白的稳定效果和简单的稳定机制。通过综述对比可以得出,常见配体辛酸钠主要起到提升热稳定性作用,常见配体N-乙酰-L-色氨酸主要起到提升抗氧化性的作用,而相较于N-乙酰-L-色氨酸,近些年研究的N-乙酰-L-甲硫氨酸具有更好的抗氧化性和抗光氧化性。

冬虫夏草氨基酸成分的药理分析

按照天然冬虫夏草所含的18种氨基酸成分进行人工配伍(配Ⅰ),以小白鼠自发活动为指标,证明配Ⅰ具有与天然虫草相似的作用;但商品复合氨基酸注射液(虽然总氨基酸含量相等)却作用显著为弱。两种复合氨基酸中含量相差5倍以上者只有谷氨酸,色氨酸及酪氨酸,再以此3种氨基酸人工配伍(配Ⅱ)。亦获同样药理效应。经正交试验证明色氨酸为主要有效成分,并求得最佳剂量比例。用碳粒廓清法证明配Ⅱ对小白鼠无增强单核巨噬细胞吞噬功能。