Thermus thermophilus 木糖异构酶与木糖醇的分子对接及模型分析

在1BXB结构基础上, 通过分子对接方法构建木糖异构酶与抑制剂木糖醇的复合物模型, 为合理设计解除木糖醇对木糖异构酶的抑制及进一步揭示木糖醇对该酶抑制机理提供参考.     

HPLC法测定半纤维素水解液中糖的研究

研究了用ＨＰＬＣ分离测定毛竹水解液中的木糖、阿拉伯糖及葡萄糖等。探讨了试样的净化方法和分离条件，试样经活性炭和ＳｅｐＰａｋＧ８小柱净化，色谱柱为ＹＷＧ－ＮＨ２，１０μｍ，４．６×２５０，流动相为乙腈＋水＝８５＋１５，流量为０．８ｍＬ／ｍｉｎ，获最佳分离。木糖、阿拉伯糖、葡萄糖的平均回收率（％）分别为９９．１、１０１和９５．０，相对标准偏差为１．２５％、１．３９％和１．５３％。     

毛细管区带电泳法分离发酵液中的木糖和木糖醇

 建立了利用毛细管区带电泳分离发酵液中木糖和木糖醇的新方法。研究表明 :采用硼砂缓冲溶液时 ,木糖和木糖醇的分离度随硼砂浓度的增高而加大 ,在室温下硼砂最高浓度为 130mmol/L ;分离度还与溶液的 pH有关 ,在pH 9 5 5处分离度有最大值 ;缓冲液中十六烷基三甲基溴化铵的浓度为 4× 10 -6mmol/L～ 8× 10 -4 mmol/L时对分离度无显著影响 ;在优化的分离条件下 ,木糖和木糖醇可在 6min内基线分离。测定了发酵过程中样品各组分的含量和加标回收率 ,5次测定木糖的相对标准偏差 (RSD)为 1 42 %～ 3 11% ,回收率为 96 0 %～ 10 8 0 % 。     

电膜法生产木糖醇工艺

电膜法生产木糖醇工艺黄玉秀（华南理工大学应用化学系广州５１０６４１）关键词木糖，木糖醇，制备，电还原法１９９６－０９－１０收稿，１９９７－０１－２３修回目前生产木糖醇都用高压加氢法［１，２］．此法工艺流程长，对设备要求高，生产不安全．应用电膜法生产木...     

木糖和木糖醇的色谱模型

利用集总模型，以柱床的物料衡算方程式、吸附等温线模型、传质推动力及初始和边界条件组成木糖、木糖醇的色谱模型，用计算机模拟得到柱中液相浓度分布仿真结果。     

H点标准加入光度法同时测定葡萄糖和木糖

１引言葡萄糖和木糖是自然界中最常见的两种单糖，其结构和化学性质极为相似，用普通方法很难将其分离和分别测定。本文利用硫酸－苯酚与糖的显色反应，采用Ｈ点标准加入法对葡萄糖和木糖不经分离进行同时测定。本法简便、快速、结果准确，已应用于食用纤维的分析。２方法原理在二元混合物（组分为ｘ和ｙ，浓度为ＣｘＣｙ）体系中，将不同量已知浓度的ｘ分别准确加入到一系列混合体系中，然后分别在λ１和λ２处测量其分析信号Ａ１和Ａ２。其表达式为：Ａ１＝ｋｘ１Ｃｘ＋Ｋｙ１Ｃｙ＋Ｋｘ１Ｃｉｘ（１）Ａ２＝ｋｘ２Ｃｘ＋Ｋｙ２Ｃｙ＋ｋｘ…     

高效液相色谱法分析蜂蜜中的糖

本文研究了用四乙撑五胺（简称ＴＥＰＡ）作为胺基改善剂，在硅胶柱上定量分析蜂蜜含糖量的方法，并成功地分离了木糖、果糖、葡萄糖、蔗糖、麦芽糖和乳糖。对操作条件进行了探讨。采用示差折光检测器检测，含０．０１％ＴＥＰＡ的乙腈－水（７７＋２３）作流动相。六种糖的相对标准偏差均小于３．５％。     

反相高效液相色谱法测定吴茱萸及制剂中吴茱萸碱和吴茱萸次碱

用反相高效液相色谱法测定了吴茱萸及制剂中吴茱萸碱和吴茱萸次碱，建立了中药及制剂中吴茱萸碱、吴茱萸次碱分离、测定的色谱方法。色谱条件：ＯＤＳ柱，乙腈＋水＋四氢呋喃＋乙酸（５２＋４８＋１＋０．１）为流动相，紫外检测波长２８０ｎｍ。方法简便、灵敏、准确、快速。     

铕与醛糖及铕与D─核糖、L─氨基酸络合作用的伏安法研究

Ｅｕ（３＋）在ＨＡｃ－ＮａＡｃ（ｐＨ４．６）溶液中与五碳醛糖有弱的络合作用，用循环伏安法和微分脉冲极谱可以观察到Ｄ－核糖，Ｄ－阿拉伯糖，Ｄ－木糖对Ｅｕ（３＋）还原波形的络合影响，使还原和氧化过程变得较为可逆，其中Ｄ－核糖最为明显，而来苏糖无影响．Ｅｕ（３＋）与氨基酸在相同实验条件下有络合作用，且在汞电极上有吸附现象，因此分别加入Ｌ－苯丙氨酸、Ｌ－组氨酸和Ｌ－蛋氨酸等，进一步改善了Ｅｕ（３＋）的波形而接近于可逆氧化－还原过程，其中以Ｅｕ（３＋）－Ｄ－核糖－Ｌ－苯丙氨酸最明确。绘出了在电极表面形成三元络合物的示意图。     

离子交换树脂层析分离多元醇的研究

本文研兖了木糖醇、阿糖醇、山梨糖醇在离子交换树脂层析柱上的分离。探讨了树脂类型、洗脱剂流量和酸度及层析温度等对分离的影响。研究结果为工业规模分离多元醇提供了理论依据。     

高效液相色谱法测定大蒜及其制品中的大蒜素

采用人工合成的大蒜素做为标准品，建立了高效液相色谱法直接测定大蒜及其制品中的大蒜素含量的方法。使用Ｓｐｈｃｒｉｓｏｂ　ＯＤＳ２色谱柱，流动相为甲醇＋水＝６０＋４０，检测波长２５４ｎｍ，进样体积２５μＬ。大蒜素最小检测量为 ２．０ ｍｇ／Ｌ，相对标准偏差为２．８％，回收率为９０．４％～１０３．０％，线性范围为 ０～１２０ｍｇ／Ｌ     

Synthesis and Photoreaction of a-Methylene-γ-Butyrolactone-Psoralen Heterodimers

Three double-headed molecules were synthesized by linking a photoreactive linear (1, 2) or angular (3) furocou-marin via a linear 10- or 5-carbon chain to an electro-philic α-methylene-γ-butyrolactone. The photochemical behavior of these molecules was investigated in ethanol at 365 nm and the photocycloadducts obtained from each compound were isolated and characterized. In all cases, the photoreactivity results showed the 3,4-pyrone double bond of the psoralen (linear or angular) to be the most reactive and [2 + 2] intramolecular photocycloadducts between the 3,4-pyrone and the exomethylenic double bonds were obtained. With compounds 1 and 2, two kinds of intramolecular photocycloadducts were obtained, namely cissyn-exo derivatives in 46% and 36% yield, respectively, and trans-syn-exo derivatives in 14% and 18% yield, respectively. With compound 3, only the trans-syn-exo derivative was obtained in 33% yield.     

芳香族化合物生物降解性的QSBR研究

分别采用线性基团贡献法和人工神经网络法对芳香族化合物的生物降解最大去除率QTOD进行QSBR研究。得到不同基团对生物降解性的贡献顺序为 :C6H5>COOH >OH >CO >CH3 >C1 >NH2>NO2 。线性基团贡献法对于训练组和测试组的预测正确率分别为 86%和 80 % ,总的预测正确率达85 % ;而人工神经网络法的预测正确率分别为 94%、80 %和 92 %。结果表明 ,线性基团贡献法和神经网络法的预测效果均很好 ,而神经网络法的预测更精确。     

Synthesis and flocculation performance of graft and random copolymer microgels of acrylamide and diallyldimethylammonium chloride

Graft (from linear homopolymers) and random (from a linear random copolymer) copolymer microgels of diallyldimethylammonium chloride (DADMAC) and acrylamide were synthesized via a free-radical mechanism using a γ-radiation technique. These copolymer microgels were evaluated as flocculants on a model dilute TiO₂ colloid suspension using a turbidimeter and a disc centrifuge photosedimentometer, and their performances were compared with the linear homopolymers and their blends. It was found that microgels produced after an appropriate irradiation time showed improved flocculation behavior over their nonirradiated linear counterparts. The graft microgels performed better than the corresponding random microgels. For a γ-radiation dosage of 100 krad/h, the graft microgels obtained by irradiating a 30% DADMAC (by weight) homopolymer blend for 3 h showed the maximum reduction in the relative turbidity of the TiO₂ suspension as well as the largest fraction of larger particles flocculated. Received: 18 May 1999 Accepted in revised form: 1 June 1999     

固相萃取–高效液相色谱法测定豆芽中4-氯苯氧乙酸钠和6-苄基腺嘌呤的残留量

建立了测定豆芽中4-氯苯氧乙酸钠和6-苄基腺嘌呤的固相萃取–高效液相色谱法。样品以0.1 mol/L的盐酸溶液为提取剂,经C18固相萃取柱净化处理,以乙腈–10 mmol/L乙酸铵水溶液(体积比25∶75)为流动相,Tech Mate C_(18)–ST色谱柱分离,4-氯苯氧乙酸钠和6-苄基腺嘌呤的紫外检测波长分别为228 nm和267 nm,色谱峰面积外标法定量。在0.50~100.00 mg/L浓度范围内,4-氯苯氧乙酸钠的相关系数为0.999 8,精密度在1.3%~8.2%之间(n=6),回收率在103.1%~109.0%之间;在0.05~10 mg/L浓度范围内,6-苄基腺嘌呤相关系数为0.999 9,精密度在0.9%~3.8%之间(n=6),回收率在88.0%~95.4%之间。4-氯苯氧乙酸钠和6-苄基腺嘌呤的检出限(S/N=3)分别为0.24,0.02 mg/kg。该法可以同时完成豆芽中4-氯苯氧乙酸钠和6-苄基腺嘌呤的分析检测。     

毛细管电泳有效分离测定甜菊糖苷新方法的研究

本文采用100％二甲基甲酰胺（DMF）作为样品的溶剂,以Tris－硼砂作为分离甜菊糖苷的缓冲体系,探讨了进样量、柱温、电压、Tris-硼砂缓冲液浓度以及pH值等条件对甜菊糖苷分离结果的影响。通过优化各种分离条件,实现了毛细管电泳高效分离测定甜菊糖苷。     

微囊藻毒素分子印迹传感器的制备与应用

以邻氨基酚为单体,微囊藻毒素(MC-LR)为模板,采用循环伏安法在金电极的表面电聚合成膜分子印迹材料,制备了传感器。采用安培法对MC-LR进行检测。在制备影响条件最佳值(pH=4.5;单体/模板=1.4×108∶1;洗脱时间10 min)的基础上,对该传感器的线性范围、使用寿命、选择性等进行了研究,并与液相色谱方法进行对比,结果表明:该传感器对MC-LR具有良好的选择性和灵敏度,线性范围为0.05～0.35 mg/L;加标回收率为80%～105%;检出限为7.3μg/L。与液相色谱方法对比,当置信度为99%时,无系统误差。     

Simulation of size-exclusion chromatography distribution coefficients of comb-shaped molecules in spherical pores comparison of simulation and experiment

Simulations of the distribution coefficients of linear polymers and regular combs with various spacings between the arms have been performed. The distribution coefficients were plotted as a function of the number of segments in order to compare the size exclusion chromatography (SEC)-elution behavior of combs relative to linear molecules. By comparing the simulated SEC-calibration curves it is possible to predict the elution behavior of comb-shaped polymers relative to linear ones. In order to compare the results obtained by computer simulations with experimental data, a variety of comb-shaped polymers varying in side chain length, spacing between the side chains and molecular weights of the backbone were analyzed by SEC with light-scattering detection. It was found that the computer simulations could predict the molecular weights of linear molecules having the same retention volume with an accuracy of about 10%, i.e. the error in the molecular weight obtained by calculating the molecular weight of the comb-polymer based on a calibration curve constructed using linear standards and the results of the computer simulations are of the same magnitude as the experimental error of absolute molecular weight determination.     

Synthesis of cyclo-PLAI using a combination of solid- and solution-phase methods

Cyclo-PLAI was successfully synthesized using a combination of solid- and solution-phase methods. This current synthesis was found to be faster than the previously reported synthesis for the cyclic peptide. The linear precursor was synthesized on 2-chlorotrityl resin with Fmoc/t-Bu strategy. HATU/HOAt was employed as the coupling reagent in the amide bond formation on the resin. Cyclization of the linear precursor was experimented with HATU/HOAt reagents with different conditions. However, the linear precursor was best cyclized using HATU reagent in DIPEA by stirring the reaction mixture at 0?°C for 1?h and followed by stirring the reaction mixture at room temperature for 30?min, giving the cyclic product in 70% yield (calculated from the linear peptide). Both linear and cyclic products were characterized using HR-TOF-ESMS, ¹H-NMR, ¹³C-NMR, and compared with previously reported spectral data for the cyclic product.