L—胱氨酸提取工艺研究

本文研究了从废羊毛和人的毛发中提取L——胱氨酸的生产工艺,并进行了从牛羊的蹄角中提取L—胱氨酸的试验。与文献中工艺记载的产率相比,该试验工艺的L—胱氨酸产率有明显提高。

生产L—胱氨酸的方法

本发明涉及L-胱氨酸的制备及提纯,特别是一种从富含α-角蛋白的人发、畜发(猪发、废羊毛、羽毛梗等)的原料中提取L-胱氨酸的生产方法,其专利号为92113884.9 L-半胱氨酸的学名为L-巯基丙氨酸,是α-氨基酸的一种,它是医药和人工营养所不可缺少的重要的氨基酸,在医、药、食品及化妆品生产中应用广泛。而生产L-半胱氨酸是以L-胱氨酸为原料经化学还原或电解还原获得。随着人们对L-半胱氨酸的需求量的不断增加,对L-胱氨酸的消耗量也不断增大。现有以毛发(人发、畜毛)为原料,经酸水解。

角质蛋白水解提取氨基酸

L—胱氨酸和L—精氨酸盐酸盐是重要的化工产品,广泛应用在医药、食品、化妆品等方面,需求量不断增加。目前,我国人发、鸡毛等角质蛋白资源丰富,我国已成为生产L—胱氨酸和L—精氨酸盐酸盐的大国。但国内生产厂家普遍存着L—胱氨酸收率低、母液中的其它氨基酸没有提出而被放掉的问题。

Application of L-Cys-Capped CdS Nanoparticles in Determination of Nucleic Acid by Resonance Light-Scattering Technique

Aim To determine nucleic acid （DNA） using Nanometer-sized L-cysteine-capped CdS particles by resonance light scattering （RLS） method. Methods The nano-particles synthesized by a colloidal aqueous method were water-soluble, stable, and highly luminescent. The RLS of L-Cys-CdS particles were greatly quenched by DNA in Tris-HCl solutions. The intensity of RLS at 344 nm was proportional to the concentration of DNA. Results The linearity range of the calibration curve was 0. 01 - 1.0 μg·mL^-1 for calf thymus DNA and 0. 04 - 1.5 μg· mL^-1 for salmon sperm DNA. The detection limits （3 δ） were 8 ng·mL^-1 for calf thymus DNA and 10 ng·mL^-1 for salmon sperm DNA. Conclusion This method is simple, sensitive, and capable of avoiding the use of toxic dyes.

PREPARATION AND CHARACTERIZATION OF WATER-SOLUBLE NEAR-INFRARED EMITTING PbS QUANTUM DOTS

A new facile method for preparing water-soluble near-infrared （NIR）-emitting PbS quantum dots （QDs） is proposed by using N-acetyl-L-cysteine （NAC, a derivate of L-cysteine） as its stabilizer. The influence of the precursor Pb/S molar ratio, the Pb/NAC molar ratio, and the pH of original solution on optical properties is explored. Results show that aqueous PbS QDs with strong NIR fluorescence can be prepared and their photoluminescence emission peaks can be tuned from 895 nm to 970 nm. Studies indicate that such aqueous QDs have a potential application in biomedical imaging, especially in noninvasive in vivo fluorescence imaging. In addition, the resulting PbS QDs are further characterized by a transmission electron microscopy and X-ray diffraction analysis.

N-acetyl-L-cysteine combined with mesalamine in the treatment of ulcerative colitis: Randomized,placebo-controlled pilot study

AIM: To evaluate the effectiveness and safety of oral N-acetyl-L-cysteine (NAC) co-administration with mesalamine in ulcerative colitis (UC) patients. METHODS: Thirty seven patients with mild to moderate UC were randomized to receive a four-wk course of oral mesalamine (2.4 g/d) plus N-acetyl-L-cysteine (0.8 g/d) (group A) or mesalamine plus placebo (group B). Patients were monitored using the Modified Truelove-Witts Severity Index (MTWSI). The primary endpoint was clinical remission (MTWSI ≤ 2) at 4 wk. Secondary endpoints were clinical response (defined as a reduction from baseline in the MTWSI of ≥ 2 points) and drug safety. The serum TNF-α, interleukin-6, interleukin-8 and MCP-1 were evaluated at baseline and at 4 wk of treatment. RESULTS: Analysis per-protocol criteria showed clinical remission rates of 63% and 50% after 4 wk treatment with mesalamine plus N-acetyl-L-cysteine (group A) and mesalamine plus placebo (group B) respectively (OR = 1.71; 95% CI: 0.46 to 6.36; P = 0.19; NNT = 7.7). Analysis of variance (ANOVA) of data indicated a significant reduction of MTWSI in group A (P = 0.046) with respect to basal condition without significant changes in the group B (P = 0.735) during treatment. Clinical responses were 66% (group A) vs 44% (group B) after 4 wk of treatment (OR = 2.5; 95% CI: 0.64 to 9.65; P = 0.11; NNT = 4.5). Clinical improvement in group A correlated with a decrease of IL-8 and MCP-1. Rates of adverse events did not differ significantly between both groups. CONCLUSION: In group A (oral NAC combined with mesalamine) contrarily to group B (mesalamine alone), the clinical improvement correlates with a decrease of chemokines such as MCP-1 and IL-8. NAC addition not produced any side effects.

Simultaneous determination mercury species of Su-He-Xiang-Wan in rat tissues by HPLC-CVG-AFS

A simple and sensitive high performance liquid chromatography-chemical vapour generation-atom fluorescent spectrometry （HPLC-CVG-AFS） method was developed and validated for simultaneous determination mercury species in Su-He-Xiang-Wan （SHXW） and in tissues of rats, respectively. The species of mercury were separated by a Venusil MP-C 18 （5μm, 150 mm×4.6 ram） column with the optimized mobile phase containing 5% （w/v） acetonitrile, 0.01 mol/L L-cysteine and 0.06 moL/L ammonium acetate. The tissues of rats were freeze-dried after giving the medicine for 10 d, and then added into the solution containing 10% （w/v） HC1, 1% （w/v） sulfocarbamide and 0.15% （w/v） KC1 for increasing extraction rate. The resolutions of Hg2＋, MeHg and EtHg were 1.5 and 2.9, respectively. The detection limits of Hg2＋, MeHg and EtHg were 2.0, 1.0 and 0.9 ng/mL, respectively. The relative standard deviation （RSD） of inter- and intra-day precisions ranged from 1.56% to 2.86%. The recovery rates of three different adding level were 87%-101% （n=6）, and the RSDs were smaller than 8.2%. The results show that no MeHg and EtHg were detected in rat tissues. Only soluble mercury （Hg2＋） was determined for the mercury species of SHXW in rat tissues.

DFT Study of Geometrical and Vibrational Features of Sulfur Containing Amino Acids in Hydrated Media： L-Cysteine and L-Methionine

Geometry optimization at the B3LYP/6-31＋＋G＊ level of theory has been undertaken on clusters containing L-Met （L-methionine） or L-Cys （L-cysteine） surrounded by eight water molecules. The comparison of the structural parameters of L-Met and L-Cys with X-ray experimental values is in good agreement within 4.8%. This result shows that the privileged positions of water molecules and the possible hydrogen bonding network formed around the backbone of both AAs （amino acids） are adequate. Subsequent calculations of the harmonic vibrational modes followed by a post-processing treatment enable us to assign the vibrational modes of L-Met and L-Cys surrounded explicitly by eight water molecules. The frequencies of the assigned modes are in good agreement with available IR （infra red） and Raman values within 5%.

Ultra-low charge transfer resistance carbons by onepot hydrothermal method for glucose sensing

Hydrothermal carbon （HTC） is typically well- dispersed, but it remains a great challenge for HTC to become conductive. Co-doping with heteroatoms has been confirmed to be an effective strategy to significantly promote the electrical conductivity of carbon. Moreover, there is no simple and green method to construct sensitive HTC based electro- chemical biosensors until now. In this paper, N and S dual-doped carbon （NS-C） with ultra-low charge transfer resistance is easily synthesized from L-cysteine and glucose in a hydrothermal reaction system. The morphology, structural prop- erties and electrochemical properties of the as-prepared NS-C are analyzed. In comparison with the undoped hydrothermal （UC） modified glassy carbon electrode （GCE）, the charge transfer resistance of UC （476 Ω） is ten times the value of NS- C （46 Ω）. The developed biosensor shows a better performance to detect glucose in a wide concentration range （50-2500 μmol L^-1） with the detection limit of 1.77 μmol L^-1 （S/N-3） and a high sensitivity （0.0554 μA cm^-2μmol^-1 L）. The apparent Michaelis-Menten constant value of GCE/NS-C/GOx/nafion modified electrode is 0.769 mmol L^-1, indicating a high affinity of glucose oxidase to glucose. These results demonstrate that the hydrothermal method is an effective way for prepar- ing high electrical conductivity carbon with excellent performances in biosensor application.