羟乙基化牛膝多糖的合成及其活性研究

以环氧乙烷为羟乙基化试剂，在碱性水溶液中，对牛膝多糖进行羟乙基化，经 过丙酮沉淀、膜分离、Sephadex G-25柱层析等分离方法得到羟乙基化牛膝多糖纯 品，检测其理化性质，并通过甲基化、GC-MS分析，初步确证糖链中羟乙基主要取 代在葡萄糖6位和困糖的1位上。药理实验表明，羟乙基化牛膝多糖对荷Lewis肺癌 小鼠NK活性具有一定促进作用。     

羧甲基壳聚糖衍生物及其振动光谱的理论研究

用量子化学从头算STO 3G法研究了羧甲基壳聚糖及其衍生物的结构和稳定性，计算结果表明:1)壳聚糖单体经羧甲基化后，得到2种可能的产物，其中羧甲基在壳聚糖单体2位氨基上的取代产物较6位羟基上的取代产物稳定； 2)以羧甲基壳聚糖为母体经加成反应，得到羧甲基壳聚糖衍生物（2 羟基 3 丁氧基）丙基 羧甲基壳聚糖的2个异构体， 其中构型1更稳定.在优化构型的基础上，计算所得的构型1的振动光谱与实验结果相吻合.     

基于MALDI-TOF质谱技术分析人宫颈癌 HeLa细胞N-糖链结构轮廓

以微量HeLa细胞(10⁷个)为对象, 经细胞裂解、还原羧甲基化、胰酶降解和Oasis-HLB柱提取分离得到总糖肽后, 用PNGase F酶解释放N-糖链. 对所得N-糖链用Sep-Pak C₁₈柱纯化后进行完全甲基化衍生, 再采用基质辅助激光解吸电离-飞行时间质谱(MALDI-TOF MS)分析HeLa细胞表面N-糖链的结构轮廓. 结果表明, 在获得的34种N-糖链中, 除高甘露糖型、二天线、三天线、四天线和五天线等N-糖链外, 还出现了在某种程度上与肿瘤发生转移相关的特殊平分型和Lewis结构. 利用MALDI-TOF MS技术可快速分析微量癌细胞表面N-糖链的结构轮廓, 为进一步寻找肿瘤糖链标志物及肿瘤的早期预防诊断提供技术支持.     

新型血浆代用品羧甲基糖淀粉的研究--Ⅰ.化学部分

本文报导了新型血浆代用品羧甲基糖淀粉钠及其原料糖淀粉的化学性质.从玉蜀黍淀粉经适度的酸水解,丁醇络合,分离得适当分子量和直链纯度的糖淀粉,再进行有控制的羧甲基化而制得有一定取代度的羧甲基糖淀粉钠.我们测定了糖淀粉的特性粘数和碘吸附量,并由此选择了作为血浆代用品原料所需要的平均分子量和直链纯度的糖淀粉的分离条件.     

库仑滴定法测定羧甲基壳聚糖的含量

正羧甲基壳聚糖(CMC)为壳聚糖的羧甲基化衍生物~([1-2]),其极性较强、易溶于水,已广泛用于制药、生物医用材料开发等领域~([3-5])。由于药物中羧甲基壳聚糖含量会直接影响其抗菌、抗感染的临床作用效果,因此对羧甲基壳聚糖进行准确定量显得尤为重要。目前相关行业标准采用凯氏定氮法间接测定     

羧甲基壳聚糖制备中的溶剂影响及精制方法研究

研究了有机溶剂中两步法制取羧甲基壳聚糖的反应过程.采用有机溶剂溶胀、氢氧化钠碱化、氯乙酸改性、乙醇溶析等步骤制备了高取代度羧甲基壳聚糖.考察了碱用量、氯乙酸用量和有机溶剂类型三个因素对羧甲基壳聚糖取代度的影响.通过比较二甲基亚砜、异丙醇、丙酮和乙醇四种有机溶剂中壳聚糖羧甲基化取代度变化规律,分析了羧甲基化的机理.实验结...     

超声波辐射制备羧甲基壳聚糖

应用超声波辐射方法制备水溶性的羧甲基壳聚糖,利用胶体滴定法测定产物中羧基含量,探讨超声波作用下,反应时间、反应温度及反应物投料比对羧甲基化程度的影响。结果表明,在其它反应条件相同时,使用超声波辐射比使用机械搅拌提高羧甲基取代程度,反应时间缩短５ｈ。     

玉米芯水溶性多糖的分离纯化和抗凝血活性研究

从玉米芯中提取到水提水溶性粗多糖,通过乙醇分级、冻融、凝胶过滤层析,生物测定导向等手段,分离到一种能延长体外凝血时间,而且具有外源抗凝血功能的多糖CCⅢ.CCⅢ对活化部分凝血酶原时间(APTT)无显著影响,但可显著延长体外抗凝血时间(PT).将CCⅢ纯化,经糖组成分析、甲基化、高碘酸氧化、Smith降解和GC-MS分析,确定该多糖结构为:β-(1→4)Glc,(1→3)Xyl构成主链,Glc在6-O处有分枝.平均每10个糖残基有1个分枝,支链由β-(1→3)Xyl,(1→3)Glc构成.     

碘甲基化法合成D-葡萄庚酮糖

以碘甲基化法增长碳链合成了D-葡萄庚酮糖。首先以D-葡萄糖酸内酯为原料,在N-甲基吗啡啉催化下进行三甲基硅烷醚保护,产率95%;然后通过正丁基锂/二碘甲烷生成的碘甲基锂试剂对酯羰基加成增长碳链,再在碱性环境中水解得2,7-脱水-β-D-吡喃葡萄庚酮糖,两步产率62%;最后经稀酸水解合成D-葡萄庚酮糖,产率90%(总产率53%)。对D-葡萄庚酮糖和2,7-脱水-β-D-吡喃葡萄庚酮糖的乙酰化产物进行了NMR表征。     

当归多糖ASP3的甲基化分析

通过部分酸水解和甲基化分析, 结合GC-MS测试手段, 对当归多糖ASP3的糖链结构进行了研究. 采用0.2 mol/L三氟乙酸(Trifluoroacetic acid, TFA)对ASP3进行了部分酸水解, 对水解前后的多糖组分进行甲基化分析. 结果显示: ASP3的糖残基主要由D-GalpA, D-Galp, L-Araf和L-Rhap组成, 主链由1,4-D-GalpA连接, 形成“光滑区”半乳糖醛酸聚糖, 由1,4-D-GalpA通过O-4位与1,2-; 1,2,4-L-Rhap的O-2位交替连接形成含有较多分支的“毛发区”鼠李半乳糖醛酸聚糖. 58.8%的Rhap残基发生O-4位取代(1,2,4-L-Rhap). 由T-, 1,5-, 1,3,5-Araf和T-, 1,3-, 1,3,6-, 1,4-, 1,4,6-D-Galp聚合形成的阿拉伯半乳聚糖、半乳聚糖以及阿拉伯聚糖是ASP3侧链的主要组成, 通过Rhap残基的O-4位与主链相连.     

Carboxymethylated cyclodextrin derivatives as chiral NMR discriminating agents

Procedures to prepare cyclodextrins with carboxymethyl groups incorporated selectively at the primary (6-position) or secondary (2-position) are described. Complexation properties of the primary and secondary carboxymethylated derivatives of α-, β-, and γ-cyclodextrins are compared to native cyclodextrins and indiscriminately substituted carboxymethylated cyclodextrins, using pheniramine, chlorpheniramine, and brompheniramine as substrates. The stoichiometry of association of these substrates with the α-cyclodextrins is 1:1, whereas with the γ-cyclodextrins, a 2:1 substrate:cyclodextrin complex forms. Data for the β-cyclodextrins suggest that there is a mix of 1:1 and 2:1 substrate–cyclodextrin complexes. The position of the carboxymethyl groups on the cyclodextrin does not appear to alter the geometry of substrate–cyclodextrin association. The effectiveness of the carboxymethylated cyclodextrins as chiral NMR discriminating agents is compared with the native cyclodextrins. In all cases, the indiscriminately substituted α-, β-, and γ-cyclodextrins are more effective at enantiodistinction with the cationic substrates than native cyclodextrins or the derivatives with carboxymethyl groups at the primary or secondary positions. Among α-, β-, and γ-indiscriminately substituted cyclodextrins, there was no clearly optimal candidate for chiral NMR discrimination studies. The indiscriminately substituted carboxymethyl cyclodextrins are effective water-soluble chiral NMR discrimination reagents for cationic substrates.     

Synthesis and use of carboxymethylated lignosulfonates

The conditions for preparing carboxymethylated lignosulfonate derivatives were examined. The complexation of carboxymethyl groups of lignosulfonates with tanning chromium compounds was demonstrated. The possibility of using modified lignosulfonates in leather retanning and filling was shown.     

Human plasma lecithin:cholesterol acyltransferase. Preparation and use of immobilized p-aminophenylarsenoxide as a catalytic site-directed covalent ligand in enzyme purification.

A method is described for the preparation of p-aminophenylarsenoxide-linked carboxymethyl (CM) Bio-Gel A and its use as a specific, catalytic site-directed affinity chromatography ligand in the final stages of the purification of human plasma lecithin:cholesterol acyltransferase (LCAT) (EC 2.3.1.43). Previous mechanistic studies by us demonstrated that phenylarsenoxide derivatives, which are highly specific for vicinal thiols, could inhibit LCAT via a covalent interaction with the sulphydryl groups of the two catalytic cysteine residues and that this inhibition could be rapidly and completely reversed upon addition of 2,3-dimercaptopropanesulphonic acid. The ligand was covalently linked to CM Bio-Gel A activated through an N-hydroxysuccinyl ester formed by N-hydroxysuccinimide and dicyclohexylcarbodiimide in dry dimethyl sulphoxide; 87% of the added p-aminophenylarsenoxide was coupled to the CM Bio-Gel A in 3 h at 25 degrees C giving 2.3 mg of p-aminophenylarsenoxide per ml of gel. Homogeneous LCAT free of apo A-I, apo E, apo D and albumin was obtained in an 11% yield and purified 15,013-fold overall. A 13-fold purification was obtained by chromatography upon p-aminophenylarsenoxide-CM Bio-Gel A. This method is a useful final step in LCAT purification and will prove valuable in the purification of other proteins and compounds containing vicinal thiols.     

Synthesis of poly(L‐lactide)‐grafted pullulan through coupling reaction between amino group end‐capped poly(L‐lactide) and carboxymethyl pullulan and its aggregation behavior in water

Poly(L ‐lactide) (PLLA) with terminal primary amino groups (PLLA‐NH₂) was synthesized and used to construct PLLA‐grafted pullulan (Pul‐g‐PLLA). It consisted of a hydrophilic carboxymethyl Pul (CM‐Pul) main chain and hydrophobic PLLA graft chains that were created through a direct coupling reaction between PLLA‐NH₂ and CM‐Pul using 2‐ethoxy‐1‐(ethoxycarbonyl)‐1,2‐dihydroquinoline as a condensation reagent. Pul‐g‐PLLAs with over 78 wt % sugar unit content were found to form nanometer‐sized aggregates in water. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5482–5487, 2004     

羧甲基木薯淀粉的取代方式研究

采用高效液相色谱(HPLC)和核磁共振波谱(^1HNMR)分析了混水/有机介质中合成羧甲基木薯淀粉的取代方式。发现HPLC是一种测定不同条件下合成的羧甲基木薯淀粉取代度(DS)的可靠方法。在测量的范围内,未取代、一取代、二取代和三取代无水葡萄糖单元的摩尔分数分布和Spurlin模型非常吻合。用高分辨率500MHz^1HNMR分析了木薯淀粉羧甲基过程的取代度和反应顺序。依据淀粉和羧甲基淀粉(CMS)的结构确定了各个峰位置。比较所得数据发现：依据HPLC计算的DSHPLC小于从500MHz^1HNMR计算所得的DSNMR。无水葡萄糖单元中C2、C3和C6的羧甲基化反应顺序为C6＞C2＞C3。     

Reduction of disulfide bonds in inactivated swine pepsin

Summary By the determination of (carboxymethyl)cysteine in the hydrolyzate of reduced and carboxymethylated pepsin and by the titration of SH groups in reduced pepsin with p-(chloromercuri)benzoate, it was shown that reduced pepsin contains six cysteine mercapto groups.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 825–829, May, 1965 Original article submitted August 28, 1964This article is published in accordance with a resolution of the Conference of Chief Editors of Journals of the Academy of Sciences of the USSR of June 12, 1962, as a dissertation paper by E. D. Levin.     

Deposition of silver nanoparticles on cellulosic fibers via stabilization of carboxymethyl groups

The stabilizing role of carboxymethyl groups on the conformal deposition of Ag NPs over cellulosic fibers was elucidated while developing a method for the deposition of silver nanoparticles (NPs) on cellulose acetate (CA), cellulose and partially carboxymethylated cellulose (CMC) electrospun fibers. CMC fibers were prepared through judicious anionization of deacetylated cellulose acetate fibers. Ag NPs were chemically reduced from silver nitrate using sodium borohydride and further stabilized using citrate. Ag NPs were directly deposited onto CA, cellulose and CMC electrospun fibers at pH conditions ranging from 2.5 to 9.0. The resulting composites of Ag/fiber were characterized by field emission scanning electron microscopy (FESEM) and energy-dispersive X-ray spectroscopy (EDX). The results revealed that the amount of Ag agglomerates and NPs deposited on CMC fibers was higher than that deposited on cellulose fibers at similar pH conditions, and that barely any Ag agglomerates or NPs were deposited on the CA fibers. These results implied that functional groups on the cellulose backbone played two important roles in the deposition of NPs as follows: (1) Hydrogen bonding was the main driving force for agglomeration of NPs when the medium pH was below 4.4, which corresponds to the pKa of carboxylic acid groups; (2) Carboxymethyl groups could replace citrate groups as stabilizers allowing the fabrication of a uniform and evenly distributed Ag NPs layer over CMC fibers at higher pH values. This report also highlights the importance of the substrate’s surface charge and that of the pH of the medium used, on the deposition of NPs. The composite of Ag NPs on CMC electrospun fibers appears to be a promising candidate for wound dressing applications due to its superior antibacterial properties originated by the uniform and even distribution of Ag NPs on the surface of the fibers and the wound healing aptness of the CMC fibers.     

Acid hydrolysis of carboxymethylcellulose of low degree of substitution

Cotton cellulose was swollen in a sodium hydroxide solution and carboxymethylated by a two-bath method for different periods of time for each process. The kinetics of acid hydrolysis and the crystallinity of the swollen and carboxymethylated samples were measured. The proportion of broken bonds, rate constants for hydrolysis, and permeability of cellulose to hydrolyzing agents were calculated. The susceptibility of glycosidic linkages to acid hydrolysis was improved by carboxymethylation more than by swelling in alkali. The increased accessibility of carboxymethylcellulose to acid was regarded as a consequence of increased intra-and intercrystalline swelling and of the glycosidic bonds' weakness caused by the electron-attracting carboxymethyl group on the C-6 position.     

Preparation of Immobilized Metal Affinity Chromatographic Packings by Immobilization of Carboxymethylated Asparate (CM-Asp) Based on Monodisperse Hydrophilic Non-porous Beads and Their Application

The hydrophilic immobilized metal affinity chromatographic packing was prepared by immobilization of carboxymethylated asparate (CM‐Asp) as chelating ligand and Ni²⁺ as center ion on the base of monodispersed, 3.0 µm non‐porous monodisperse poly(glycidylmethacrylate‐co‐ethylenedimethacrylate) (P_GMA/EDMA) particles. The retention behavior of proteins and the effect of pH on the retention in the range from 4.0 to 9.0 were investigated on both the naked and metal ion chelated columns. Four proteins were quickly separated in 2.0 min with linear gradient elution at a flow rate of 3.0 mL·min^?1 by using the synthesized Ni²⁺‐CM‐Asp‐P_GMA/EDMA packings. The separation time was shorter than other immobilized metal affinity chromatography reported in the literature. The Ni²⁺‐CM‐Asp‐P_GMA/EDMA column was further investigated for the rapid separation and purification of copper‐zinc superoxide dismutase (Cu,Zn‐SOD) from the blood of pig in 3.0 min with only one step. The results obtained were satisfactory.