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.

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.

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%.

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。

L-色氨酸促进二氧化碳水合物生成特性实验研究

深海水合物法封存二氧化碳(CO_(2))被视为极具潜力的碳封存技术,而实现CO_(2)水合物(以下简称“水合物”)快速生成是该技术推广应用的关键。采用恒温恒容法研究了L-色氨酸溶液在不同质量分数和搅拌状态下对水合物生成动力学的影响。同时研究了L-色氨酸溶液对水合物宏观形态的影响。结果表明,0.10%L-色氨酸溶液和纯水在静止状态下,液体表面形成一层水合物膜,阻止气液进一步接触,且水合物生成量较少,对水合物生成没有促进作用;质量分数为0.15%~0.50%的L-色氨酸溶液对水合物生成有促进作用,但促进效果不稳定;1.00%L-色氨酸溶液对水合物成核和生长速率具有显著促进作用,相比纯水显著增加了水合物生成量。开启搅拌可大幅提高纯水和0.50%L-色氨酸溶液的水合物生长速率,增加纯水中水合物生成量,但对0.50%L-色氨酸溶液中水合物生成量几乎没有影响。水合物倾向于首先在气液固三相界面成核,初期以二维横向模式生长,添加L-色氨酸可改变水合物宏观形态。分析认为,L-色氨酸的疏水端吸附在水合物晶体表面,使水合物疏松多孔,亲水端与水分子结合,增强了水合物表面亲水性,强化了气液接触,最终促进水合物生成。研究结果对开发新型绿色水合物动力学促进剂与促进CO_(2)捕集技术发展有理论指导意义。

基于β-环糊精修饰的碳量子点对D,L-色氨酸的识别和L-色氨酸定量分析

目的建立基于β-环糊精(β-CD)修饰碳量子点(CQDs)的D,L-色氨酸(D,L-Trp)手性药物识别荧光分析方法,并实现L-色氨酸(L-Trp)的定量分析。方法以碳纤维为碳源,采用硝酸氧化法制备CQDs,利用EDC/NHS化学偶联法将乙二胺-β-CD修饰到CQDs表面,成功制备β-CD/CQDs复合物,构建D,L-Trp对映体手性识别荧光传感器。采用紫外-可见吸收光谱、荧光光谱、红外光谱及X射线电子能谱等技术评价CQDs及β-CD/CQDs复合物的理化性能,并进行合成与识别条件优化。结果在pH值为5.5或6.0和反应温度为40℃的条件下,β-CD/CQDs复合物能够很好地识别D,L-Trp手性,且L-Trp在6~38μmol/L与荧光强度呈良好线性关系(r=0.998),检测限为0.94μmol/L。结论建立的手性药物识别荧光方法具有良好的特异性,能够实现对D,L-Trp的识别以及对L-Trp的定量分析。

L-色氨酸对早期断奶仔猪肠道消化及免疫功能的影响

该试验旨在探讨L-色氨酸对早期断奶仔猪的肠道消化及免疫功能的影响。选取36头产期相近、胎次相似的刚出生健康仔猪,随机分为早期断奶组、正常断奶组、色氨酸组;早期断奶组:仔猪14日龄断奶;正常断奶组:仔猪35日龄断奶;色氨酸处理组:仔猪14日龄断奶后,每天灌胃L-色氨酸溶液;仔猪35日龄安乐死,取血清、空肠组织、空肠黏膜以及肠道食糜,测仔猪空肠黏膜消化酶活性、肠道食糜SIgA等的差异变化。结果显示,色氨酸能够提高肠道消化酶活性,色氨酸具有促进肠道食糜SIgA的水平。添加色氨酸可以有效增强肠道的消化及免疫功能。

黄蜀葵花总黄酮抗氧化及抗抑郁作用研究

对黄蜀葵花总黄酮抗氧化和抗抑郁作用进行研究。采用小鼠强迫游泳实验(FST)、悬尾实验(TST)、旷场实验(OFT)作为行为学实验模型考察黄蜀葵花总黄酮的抗抑郁作用;利用试剂盒检测小鼠血清中超氧化物歧化酶(SOD)活力、丙二醛(MDA)的含量考察黄蜀葵花总黄酮体内抗氧化作用;采用高效液相色谱法测定小鼠血清中色氨酸(Trp)、犬尿氨酸(Kyn)的含量及比值。结果表明:与普通组相比,黄蜀葵花总黄酮各组有效缩短了小鼠TST、FST的静止时间;黄蜀葵花总黄酮高剂量组(200 mg/kg)能有效降低小鼠血清中MDA质量含量,改善小鼠血清中SOD活力,提高小鼠血清中Trp/Kyn的比值。黄蜀葵花黄酮具有抗抑郁作用,其作用机制可能与黄酮的抗氧化作用、色氨酸与犬尿氨酸的代谢途径有关。

基于紫色杆菌素生物合成途径的L-色氨酸生物传感器的构建

结合生物传感器进行高通量筛选是鉴定L-色氨酸高产菌株的有力工具,但现有的L-色氨酸生物传感器普遍存在工作范围和动态范围都较低的缺点。在大肠杆菌中表达紫色杆菌素生物合成途径,测试不同来源的VioA酶,结合RBS工程,开发了一种新型酶偶联L-色氨酸生物传感器。测试发现来自Chromobacterium violaceum的VioA酶可使该传感器的检测上限扩大至10 g/L外源添加的L-色氨酸;将其RBS的初始翻译速率降低到约2000时,传感器的动态范围扩大到55倍;通过肉眼可直观地区分L-色氨酸产量不同的大肠杆菌菌株。这种新型的L-色氨酸生物传感器可结合高通量筛选等手段,在鉴定L-色氨酸及其高附加值衍生物高产菌株等方面发挥巨大作用。

基于肠道类器官解析益生菌调节肠嗜铬细胞合成5-HT的效应物质

5-羟色胺(5-hydroxytryptamine,5-HT)是由一种占比不到肠上皮细胞数量1%的肠嗜铬(enterochromaffin,EC)细胞产生的神经递质,其中色氨酸羟化酶1(tryptophan hydroxylase 1,TPH1)是5-HT合成途径的限速酶。特定的益生菌能够调节EC中Tph1基因的表达,维持肠道正常的5-HT合成。然而,其作用机制尚不明确。该研究利用代谢物组学技术对益生菌发酵产物中的主要活性物质进行分析,并基于小肠类器官建立了代谢产物和Tph1基因表达之间的互作量效关系,明确了L-乳酸、乙酸是益生短双歧杆菌调节肠道5-HT合成的关键效应物质。研究结果明确了特定功能益生菌发挥生理作用的物质基础,为同类功能益生菌的定向筛选提供了理论支撑。

L-色氨酸分离纯化工艺改进的探讨

随着L-色氨酸发酵水平的不断提高,发酵液后提取的分离纯化将成为决定生产成本的关键因素。本文通过分析对比连续离交技术和色谱技术,对L-色氨酸分离纯化的工艺做进一步的探讨。

氮掺杂碳量子点@花状氧化锌检测L-色氨酸

通过水热法制备N-CQDs@ZnO复合材料,使用傅里叶变换红外光谱、X射线衍射仪、荧光光谱、紫外-可见光吸收光谱、透射电镜对复合材料进行表征.然后,将复合材料修饰在玻碳电极上,构筑一种用于检测L-色氨酸的新型电化学传感平台,采用循环伏安法(CV)、差分脉冲伏安法(DPV)、电化学阻抗法(EIS)进行电化学研究.在优化条件下,N-CQDs@ZnO4/GCE对于L-色氨酸的检出限为32 nmol·L-1,灵敏度为0.78μAμmol·L-1cm-2,该传感器成功应用于血清中L-色氨酸的检测.