中性蛋白酶的单甲氧基聚乙二醇修饰

目的利用单甲氧基聚乙二醇(mPEG)化学修饰中性蛋白酶,并考察修饰酶的酶学性质。方法采用氰脲酰氯对mPEG5000进行活化,再对中性蛋白酶进行化学修饰,制得mPEG-中性蛋白酶,并比较中性蛋白酶在修饰前后的红外光谱和酶学性质。结果中性蛋白酶的修饰率为41.7%;红外光谱分析表明,修饰酶红外光谱图的多处特征峰有较大的改变;其最适温度和最适pH值未发生变化,但修饰酶的热稳定性显著提高。结论确定了经mPEG化学修饰中性蛋白酶的最适温度和最适pH值,获得的修饰酶热稳定性高于天然酶。     

单甲氧基聚乙二醇修饰蚓激酶的制备及性质研究

采用以三聚氯氰活化的单甲氧基聚乙二醇(mPEG-5000),对从赤子爱胜蚓体内提取的抗血栓酶——蚓激酶进行了化学修饰,以期降低其抗原性及增加它的稳定性。实验表明,在37℃下,15.0mL,pH9.2,0.1mol?L?1的硼酸缓冲液中,按每1.0mg的蚓激酶加入25.5mg活化的mPEG,水浴保温1h,经透析、超滤浓缩、冻干得mPEG修饰酶,测得蚓激酶的修饰率为63.2%,酶活回收率为56.6%。在此基础上,对修饰蚓激酶的性质进行了研究。结果显示,修饰后的蚓激酶对底物的亲和力有所增加(天然酶表观米氏常数Km值为0.267mg.mL?1,修饰酶Km'值为0.115mg.mL?1);修饰蚓激酶的抗胰蛋白酶水解能力、热稳定性均优于天然酶;同时修饰酶的抗原性有了较大程度的降低,与抗血清的结合能力大约是天然酶的25.0%左右。     

单甲氧基聚乙二醇化学修饰人血清白蛋白及产物性能表征

用三光气活化的单甲氧基聚乙二醇5000 （mPEG）和N-羟基琥珀酰亚胺（NHS）反应制备单甲氧基聚乙二醇琥珀酸亚胺酯（SC-mPEG）,SC-mPEG修饰人血清白蛋白（HSA）制备mPEG-HSA.傅里叶变换红外光谱仪（FT-IR）、紫外分光光度计（UV）和高效液相色谱仪（HPLC）对产物结构予以分析表征.结果表明,已经成功得到目标产物,mPEG的平均活化度为75％,SC-mPEG与HSA的平均偶联度为45％.     

单甲氧基聚乙二醇氨基的制备

通过两步反应制备了相对分子质量(简称分子量)为5 000的单甲氧基聚乙二醇氨基(m PEG5k-EDA)。首先以单甲氧基聚乙二醇5 000(m PEG5k)和对甲苯磺酰氯(p-Ts Cl)为原料,反应得到活性中间体m PEG5k-OTs,然后通过与乙二胺的亲核取代反应获得目标产物,并通过正交实验确定了最佳反应条件:m PEG5k-OTs与乙二胺的摩尔比为1∶25、反应温度为80℃和反应时间为24 h。产物和中间体的结构通过IR和1HNMR进行表征,并通过SDS-PAGE碘染色法检测产物分子量的变化情况。结果表明,通过该方法能简便快捷地制备m PEG5k-EDA,在最优实验条件下,目标产物的总收率高达76.8%,且SDS-PAGE检测表明,产物纯度较高,不含交联副产物。     

干扰素聚乙二醇修饰的研究进展

干扰素(Interferon,IFN)是一类具有抗病毒、免疫调节、抑制细胞增殖等多种生物活性的细胞因子,而体内循环半衰期短限制了其在临床上的应用。聚乙二醇(Polyethylene glycol,PEG)修饰可以有效地改善干扰素的理化性质和生物学特性,延长体内循环半衰期。本文综述了聚乙二醇修饰干扰素的研究进展,着重介绍了聚乙二醇修饰化学的发展,α、β、γ干扰素各自不同的聚乙二醇化学修饰方法,并对聚乙二醇化干扰素的发展趋势进行了展望。     

胰高血糖素样肽-1在乙醇中的聚乙二醇修饰

以乙醇为溶剂,单甲氧基聚乙二醇琥珀酰亚胺碳酸酯(mPEG-SC)为修饰剂,对胰高血糖素样肽-1(GLP-1)进行了修饰反应条件的优化,同时对单修饰产物Mono-PEG-GLP-1进行分离纯化,并考察了其体外稳定性和体内活性. 得到的优化反应条件为：GLP-1浓度1 mg/mL, mPEG-SC与GLP-1摩尔比1:1, 37℃下反应24 h,该产物最高转化率达77%. 采用冷冻离心方式对Mono-PEG-GLP-1进行初步分离和浓缩,然后经反相液相色谱进一步高效纯化,纯度可达97%以上. 体外实验表明,Mono-PEG-GLP-1在血清中具有更好的稳定性及更强的抗胰蛋白酶消化能力. 体内动物实验表明,Mono-PEG-GLP-1具有更好的降血糖作用.     

聚乙二醇修饰技术研究进展

介绍了聚乙二醇修饰技术在蛋白质和多肽类等药物中的应用,论述了聚乙二醇修饰对蛋白质和多肽类等药物性质的影响,修饰技术在药物研究中的应用。     

马来酸单聚乙二醇单甲醚酯的合成工艺

在自制催化剂、溶剂甲苯存在下,由马来酸酐与聚乙二醇单甲醚(400)通过直接酯化法合成马来酸单聚乙二醇单甲醚酯。当马来酸酐与聚乙二醇单甲醚摩尔比为(1.05—1.1)∶1时,控制温度100—105℃,反应7 h,合成的马来酸单聚乙二醇单甲醚酯的产率可以达到98%。通过红外光谱分析,发现所合成的酯的官能团分布和进口日本酯(NKesterM-90)非常接近,证明所合成的马来酸单聚乙二醇单甲醚酯满足预定的制备要求。     

聚乙二醇修饰重组人粒细胞集落刺激因子反应过程的优化

采用单甲氧基聚乙二醇(mPEG)修饰重组人粒细胞集落刺激因子rhG CSF，考察了各因素对蛋白质平均修饰度及体外生物活性的影响，并对修饰产物的稳定保存条件进行了初步探讨. 通过四因素四水平正交法和单因素实验结合，优化修饰条件为：PEG与G CSF摩尔比为25:1, pH 7.6的硼酸盐缓冲环境，反应时间40 min，反应温度22℃. 在此条件下，PEG-G-CSF的平均修饰度为50%，活性可保留40%左右. 研究还发现，不同的添加剂影响PEG-G-CSF的保存稳定性，人血清白蛋白和甘露醇是两种效果最好的保护剂，在它们的存在下，PEG-G-CSF溶液在4℃放置一个月后活性保留92%，三个月后保留51%.     

应用活化mPEG5000修饰HCG及其活性研究

活化甲基聚乙二醇5000（mPEG5000）与高比活人绒毛膜促性腺素（HCG）纯品交联，利用放射受体测定法检测了修饰剂mPEG5000用量与HCG活性保留率的关系，并发现经mPEG5000修饰后HCG的活性稳定性增强，表现为对pH变化和胃蛋白酶破坏的耐受力增大，使之更适于临床使用。     

不饱和阳离子水性聚氨酯改性蒙脱土的制备与性能研究

合成出一种不饱和水基阳离子聚氨酯树脂（UCWPU）,以其作为插层剂并采用超声波助混技术对蒙脱土（MMT）进行有机改性,通过阳离子交换制备出含有不饱和官能团的活性有机蒙脱土（OMMT）。采用傅里叶变换红外光谱（FTIR）、广角X射线衍射（XRD）、透射电镜（TEM）、热失重分析（TGA）和显微电泳法等检测手段分别对改性后蒙脱土的结构、性能进行了分析表征。结果表明,改性后的蒙脱土层间距由原来的1．21nm增大到2．13nm,阳离子聚氨酯改性的蒙脱土粒子电性显正电。FT—IR和TGA测试结果表明UCWPU分子链稳定存在于蒙脱土层问。     

3,4'-ODA改性PPTA的制备及其性能研究

采用低温溶液缩聚法,在刚性的聚对苯二甲酰对苯二胺(PPTA)聚合体系中引入柔性第三单体3,4'-二氨基二苯醚(3,4'-ODA),得到了比浓对数黏度较高的改性PPTA树脂,讨论了3,4'-ODA含量对改性PPTA的比浓对数黏度、结晶性能、热性能和溶解性能以及改性PPTA薄膜的表面形态和力学性能的影响。结果表明:随着3,4'-ODA含量的增加,PPTA的溶解性变好,能够有效推迟聚合反应相转变的时间,提高相对分子质量;当3,4'-ODA摩尔分数为0~5%时,随着3,4'-ODA含量的继续增加,改性PPTA相对分子质量呈现先增加后下降的趋势,结晶度从54.21%下降为44.73%,但却仍能保持良好的耐热性能,最大分解温度均在590℃左右;引入少量的3,4'-ODA后,改性PPTA溶解性变好且制得的薄膜力学性能良好;当3,4'-ODA摩尔分数为2%时,改性PPTA比浓对数黏度最大为3.57,其薄膜的强度和模量最高,强度为96.30 MPa,模量为2.67 GPa。     

Thermostability of modified enzymes: a detailed study

Three enzymes (lysozyme, EC 3.2.1.17; α‐chymotrypsin, EC 3.4.21.1; and Candida rugosa lipase, EC 3.1.1.3) have been modified in order to alter their surface hydrophobic/hydrophilic balance in opposite directions, by chemoenzymatic glycosylation and chemical binding of polyethylene glycol (PEG). The thermal stability in aqueous environment of the produced biocatalysts was studied, and two different approaches were considered: the determination of half‐life times and the mechanistic analysis of the deactivation kinetics. The comparison of half‐life times indicated that an increase in enzyme surface hydrophobic character induced a remarkable amelioration in thermostability, while the increase in hydrophilic character produced the opposite effect. However, the investigation of kinetic and thermodynamic parameters of enzyme deactivation revealed, in some cases, secondary stabilisation effects during some step of the mechanism, which would not have been detected if only half‐life times had been considered. © 1999 Society of Chemical Industry     

聚乙二醇改性环氧丙烯酸阴极电泳涂料用乳液的制备

以聚醚多元醇改性环氧丙烯酸酯为主体树脂制备了阴极电泳涂料用乳液。讨论了聚醚多元醇的种类和用量对改性环氧丙烯酸乳液及其涂膜性能的影响,以及扩链反应温度和时间对环氧基转化率的影响。通过红外光谱(FT-IR)和热重分析(TG)对改性前后的环氧丙烯酸阳离子树脂进行了表征。试验发现,以PEG1000为扩链剂,用量为13%~14%,在90°C下反应4h,制得的改性环氧丙烯酸乳液平均粒径65.49nm,ζ电位58.3mV,乳液黏度0.21Pa.s,常温下放置300d未分层。改性后的阴极电泳涂料漆膜柔韧性为0.5mm,附着力0级,硬度2H,冲击强度50kg.cm,耐水性达到208h,性能明显优于改性前的漆膜。     

Preparation and characterization of polyethylene–clay nanocomposites by using chlorosilane‐modified clay

Clay was modified by trimethylchlorosilane; after modification, hydroxyl groups at the edge of layers were reacted and CEC value was drastically decreased. Polyethylene–clay composites were prepared by melt compounding. Wide angle X‐ray diffraction (WAXD) and transmission electron microscopy (TEM) showed that intercalated nanocomposites were formed using organoclay ion‐exchanged from chlorosilane‐modified clay, but conventional composites formed using organoclay directly ion‐exchanged from crude clay. Dynamic mechanical analysis (DMA) of PE and PE–clay composites was conducted; the results demonstrated that nanocomposites were more effective than conventional composites in reinforcement and addition of organoclay resulted in the increase of glass transition temperature (T_g), but crude clay had no effect on T_g of PE–clay composites. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 676–680, 2004     

Preparation and characterizations of organic fluorine–silicon and polytetrafluoroethylene modified polyester

Hydrophobically modified polyester was synthesized via copolymerization between hydroxy‐fluorosilicone polymer (FGX) and bis(2‐hydroxyethyl) terephthalate (BHET), which was named as CMPET. The relations between surface properties of CMPET and FGX viscosity and dosage were studied by contact angle measurements. An optimized synthesis route was determined. b‐CMPET with better hydrophobic property was obtained by adding polytetrafluoroethylene (PTFE) into CMPET. A full characterization were given to both CMPET and b‐CMPET, including ¹H‐NMR, ESCA, mechanical properties, water absorption, contact angle and surface energy analysis. It was found that chemical bondings were formed between FGX and BHET in c‐CMPET via copolymerization. The addition of 12% FGX with viscosity of 2000CP after the system pressure reached the low pressure for 20 min is an optimum condition. The modified polyester (CMPET‐12) shows the best hydrophobic effect. Blending a certain amount of PTFE powder with low‐surface energy can further enhance the hydrophobic properties of CMPET, due to a strong tendency of PTFE migrate to the sample surface together with organic fluorine–silicon segments. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011