枸杞多糖的提取及含量和分子量分布的测定

根据多糖分子量不同在浓度不同的乙醇中溶解度不同，从宁夏枸杞子中分离得到一种临床效果较好的枸杞多糖，并测定了其含量和分子量分布。     

一种龙眼多糖分离纯化与结构解析

提取、分离水溶性龙眼多糖,经过DEAE-纤维素、Sephacryl S-400 HR柱纯化得到均一龙眼多糖LPB-2-M,采用高效凝胶渗透色谱法进行纯度鉴定和分子量测定,IR、1H-NMR定性分析。结果表明:龙眼多糖LPB-2-M总糖含量为84.32%,重均分子量Mw为80217Da,分散系数D=1.0348;含有较多β-型异构碳和吡喃环;热稳定较好,在230℃以下不易热分解。     

高效液相色谱法测定香菇多糖的分子量

本文建立了HPLC法测定香菇多糖的分子量的方法。采用GPC色谱柱,以醋酸盐缓冲溶液(0.2MpH值4.0)为流动相,示差折光检测器检测。结果表明:香菇多糖的分子量在3.9×104～8.0×105范围内具有良好的线性(r=0.99694)。测得样品分子量为7.1×105,精密度实验RSD为0.0983%。证明该法简便、快速、灵敏度高、重现性及稳定性均较好,可用于其它大分子量物质的分子量测定。     

罗汉果多糖的分离纯化及分析

采用热水法提取罗汉果多糖,用Sevag法去除蛋白质,通过用DEAE-纤维素柱和Sephadex G-200柱的分离纯化得到2个多糖组分。经测定,其相对分子质量分别为Mr1=430000,Mr2=650000。组分1的单糖组成：葡萄糖、半乳糖、木糖、阿拉伯糖、鼠李糖和葡萄糖醛酸;组分2的单糖组成;鼠李糖、葡萄糖醛酸。     

山药多糖的功效与提取纯化及含量测定

山药作为日常生活中一种常见的食材,口感细腻,营养丰富,具有增强人体免疫力、改善睡眠、补脾益肺等功效.现代医学研究表明,山药具有多种生物活性,并认为山药中的主要功效成分是山药多糖.本文对山药多糖的功效及其提取、纯化、含量测定方法研究予以综述.     

植物多糖的纯化工艺研究进展

现阶段纯化工艺一般为:脱脂、脱色、脱蛋白、分离。本文综述了纯化工艺中各步骤的常用方法及应用情况,分析它们的原理及优缺点并对发展前景做进一步探讨。     

白芨多糖的分子量测定及其吸湿保湿性评价

通过水提醇沉法制取白芨粗多糖,采用Sephadex G-200和Sephadex G-25凝胶柱层析对粗多糖进行纯化,通过红外光谱、高效液相色谱联用多角度激光散射(HPSEC-MALLS)法对纯化后多糖进行结构分析和分子量测定。考察了白芨多糖的吸湿保湿性能,并将其添加到化妆品面霜配方中进行皮肤水分测试。结果表明:红外图谱显示白芨多糖是吡喃型多糖,且含有甘露糖;白芨多糖的重均分子量Mw=9.545×104g/mol,数均分子量Mn=7.297×104g/mol;该分子量下的白芨多糖在相对湿度(RH)为43%时最大吸湿率为6.0%,保湿率为88.8%,在RH为81%时最大吸湿率为99.0%,保湿率为105.5%;皮肤水分测试结果表明含白芨多糖液的面霜具有良好的保湿效果。     

超高分子量聚乙烯分子量及分子量分布的测定

超高分子量聚乙烯UHMWPE的分子量和分子量分布直接影响其加工性能和机械性能,然而传统的凝胶色谱法(GPC)存在一定的局限性,粘均分子量难以全面反映UHMWPE的结构特点。为了开发出一种精度高、重复性好的UHMWPE分子量和分子量分布测试方法,本研究在常规高温GPC设备的基础上,基于溶液流动分级机理,选取了合适凝胶孔径的凝胶色谱柱,改善了普通GPC测试结果分子量分布偏宽的问题。并通过对UHMWPE/三氯苯溶解方法的深入研究,解决了普通GPC测试结果重复性差的问题。对UHMWPE新产品的研发和后期的加工有着重要的实际意义。     

灵芝多糖提取及纯化工艺研究

为了优化制备高纯度灵芝多糖的提取及纯化工艺,获得高纯度的灵芝多糖药学研究用样品.以灵芝子实体为原料,药用纯化水为溶剂,以固形物含量和多糖含量为考察指标,通过对比研究确定灵芝水提物生产的最优工艺条件.灵芝水提物制备的最佳工艺条件为:料液比1∶15、提取两次、第一次提取时间为4 h、第二次提取时间为3 h,得到水提物收率6...     

黄芪多糖的分离纯化及药理作用研究进展

目的:介绍黄芪多糖的分离纯化及药理作用研究进展。方法:检索近几年关于黄芪多糖分离纯化及药理作用的研究报道,进行归纳总结。结果:黄芪多糖具有抗氧化、抗肿瘤、降糖、抗菌、心血管保护等药理活性;黄芪多糖分离纯化方法主要有大孔吸附树脂分离技术、凝胶柱层析法、DEAE纤维素柱层析法、分级醇沉法等。结论:黄芪多糖药理及分离技术研究广泛,为其深入研究奠定基础,具有良好的发展前景。     

b型流感嗜血杆菌精制多糖分子大小分布及重均分子质量检测方法的改良

目的 改良HPLC(AKTA 层析)系统,采用HPLC-MALLS 系统检测b 型流感嗜血杆菌(Haemophilus influenzae type b,Hib)精制多糖的分子大小分布及重均分子质量(Mw),并进行方法的验证.方法 采用HPLC(AKTA层析)系统连接示差分析仪检测9批Hib精制多糖供试品的分配系数(...     

具有酪氨酸酶抑制作用的酵母多肽的分离纯化及分子量分布

为确定具有较好酪氨酸酶抑制作用的酵母多肽的分子量,对酵母多肽粗制品溶液以截留相对分子量为10 KDa、5 KDa、1 KDa的超滤膜进行超滤,采用生化酶法对不同超滤组分进行酪氨酸酶抑制活性检测。结果显示,各多肽组分的活性随相对分子量的减少而增大,活性多肽的相对分子量主要集中在1 KDa以下。对相对分子量1 KDa的多肽组分依次以DEAE-52阴离子交换柱层析法和Sephadex G-15凝胶层柱析法进行分离,最后得到4个洗脱组分,分别富集各洗脱组分并进行酪氨酸酶抑制活性研究。结果表明,组分d-1活性最佳,其IC50值为3.53 mg/mL。经高效液相空间排阻色谱分析,d-1组分多肽的相对分子质量主要集中在200~800 Da。     

凝胶色谱法测试PVC树脂平均分子质量及分子质量分布

叙述了凝胶色谱法的测试原理,介绍了用凝胶色谱测试PVC树脂平均分子质量及分子质量分布的方法。     

聚丙烯酰胺分子量测定准确度探讨

本文对流径时间、恒温温度,浓度等误差通过计算及实验检测分析其对分子量测定准确度的影响。     

聚丙烯熔体流动指数与分子量及其分布的关系

研究了聚丙烯(PP)的熔体流动指数(MI)与聚合物不同分子量之间的关联性,对于分子量分布较窄的PP,数均分子量(Mn)、重均分子量(Mw)和粘均分子量(Mv)均能较好的关联;反之,MI与Mn关联性下降,而MI与Mn和Mv的关联性仍很好,尤其是MI与Mv的关联性受分子量分布的影响很小;MI与Z均分子量的关联性很差。同时．确定了MI与各种分子量之间的关联式,该式用于本体PP工艺反应器内氢气浓度的计算和MI的预测,与实验测量结果吻合良好。     

Effects of molecular weight and molecular weight distribution on creep properties of polypropylene homopolymer

The molecular weights of the industrial-grade isotactic polypropylene (i-PP) homopolymers samples were determined by the melt-state rheological method and effects of molecular weight and molecular weight distribution on solid and melt state creep properties were investigated in detail. The melt-state creep test results showed that the creep resistance of the samples increased by M_w due to the increased chain entanglements, while variations in the polydispersity index (PDI) values did not cause a considerable change in the creep strain values. Moreover, the solid-state creep test results showed that creep strain values increased by M_w and PDI due to the decreasing amount of crystalline structure in the polymer. The results also showed that the amount of crystalline segment was more effective than chain entanglements that were caused by long polymer chains on the creep resistance of the polymers. Modeling the solid-state viscoelastic structure of the samples by the Burger model revealed that the weight of the viscous strain in the total creep strain increased with M_w and PDI, which meant that the differences in the creep strain values of the samples would be more pronounced at extended periods of time.     

GPC法测定苯丙树脂相对分子质量及其分布

建立了GPC凝胶渗透色谱法测定苯丙树脂相对分子质量及其分布的方法:采用Styragel Wat 044207(500~30 000)(THF),Wat 044210(5 000~600 000)(THF)及Wat044213(5 000~4 000 000)(THF)3根凝胶色谱柱串接,柱温35℃;四氢呋喃为流动相,流速1 mL/min;采用示差折光检测器,待测样品浓度0.03 g/mL,精密度和重现性实验结果表明:该方法数据可靠、重复性好、简单易行。     

Determining molecular weight scale and molecular weight distribution of ethylene-tetrafluoroethylene alternating copolymer via a rheological technique

A self-scaling rheology-based technique was developed to determine the molecular weight (MW) and molecular weight distribution (MWD) of ethylene-tetrafluoroethylene alternating copolymer (ETFE). The self-scaling technique makes determining MW and MWD with isolated completely rheological method possible. Moreover, the two key parameters (the plateau modulus and zero-shear viscosity) were obtained by more robust numerical technique, which let determining MW and MWD via rheological method initiated by Tuminello [Macromolecules 1993, 26, 499] being building on more robust and rigid basis. Our case overcomes the shortage of Tuminello's method and gives more practical and simply mean to analyze the MW scale and MWD in the production and application of ETFE. It is found that the peak MW of a ETFE (commercial grade: EP541) is 1.73 × 10⁵ g/mol, the MWD curve is a pattern with a slightly raised “shoulder” at high-molecular mass end, and a high peak on the median and the polydispersity is broad (the polydispersity index is near to 10.3). The wide polydispersity indicates the commercial ETFE combining good processability of relative lower MW molecules with physical properties of high MW ones. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Purification of peroxidase from Amsonia orientalis by three-phase partitioning and its biochemical characterization

The present work describes the purification and characterization of peroxidase from the medicinal plant, Amsonia orientalis, for the first time. The activity recovery for peroxidase was 162% with 12.5-fold purification. Optimal purification parameters were 20% (w/v) (NH₄)₂SO₄ saturation at pH 6.0 and 25°C with 1.0:1.0 (v/v) ratio of crude extract to t-butanol ratio for 30 min. The molecular mass of the enzyme was found to be ca. 59 kDa. Peroxidase showed K_m values of 1.88 and 2.0 mM for pyrogallol and hydrogen peroxide, respectively. FeSO₄, CuSO₄, HgCl₂, MnSO₄ and MgSO₄ did not inhibit the enzyme activity.     

Polystyrene-equivalent molecular weight versus true molecular weight in size-exclusion chromatography

The evaluation of the size-exclusion chromatography (SEC) concentration elution curves by means of a calibration dependence obtained in a given SEC set for a polymer different from the polymer to be analyzed results in an error in the determination of both molecular weight and molecular-weight distribution (MWD). The problem is analyzed assuming the validity of the universal-calibration concept. The differences between the true and apparent values of molecular weight, MWD and M_w/M_n depend on and are expressed in terms of the parameters of the Mark-Houwink-Kuhn-Sakurada equation, describing the molecular-weight dependence of intrinsic viscosity, for the polymer to be analyzed and the polymer used for calibration. The differences in molecular weight and the M_w/M_n ratio are typically tens of percent and, in extreme cases, can amount up to a factor of three for molecular weight and a factor of two for the M_w/M_n ratio.