黑小麦麦麸戊聚糖的部分酸水解特征与甲基化分析

研究了黑小麦麦麸戊聚糖(AEPH)的部分酸水解特征及其糖链的取代度和取代方式等结构信息. 分别采用0.02, 0.1和0.2 mol/L的三氟乙酸(Trifluoroacetic acid, TFA)对AEPH进行部分酸水解, 结合甲基化分析、 GC-MS和HPLC等方法对AEPH的糖链结构和相对分子质量分布进行了分析. 结果表明, 戊聚糖AEPH的糖残基主要由阿拉伯糖(Araf)和木糖(Xylp)组成. 其取代度(A/X), 即Araf与Xylp的比值为0.60, 并具有较高的相对分子质量(M_w=3.81×10⁵). AEPH的主链由Xylp残基通过1→4连接形成木聚糖. 主链Xylp在O2, O3或O2/O3位被Araf单取代或双取代. 非取代(u)、 单取代(m)和双取代(d)Xylp残基的组成比例为57.7∶22.0∶6.2. 非取代与取代Xylp的比值为2.1, 双取代与单取代Xylp比值(d/m)为0.3. Araf主要以非还原性末端T-Araf以及通过1→2和1→5连接形成低聚阿拉伯糖的形式与主链Xylp相连, 或与T-Xylp相连形成戊聚糖分子的支链.     

当归多糖ASP3及其水解产物的NMR光谱分析

对当归多糖ASP3的糖链结构进行分析. 分别采用0.2 mol/L三氟乙酸(Trifluoroacetic acid, TFA)和内切-α-(1→4)-聚半乳糖醛酸酶(EndoPG)对ASP3进行部分酸水解和酶水解, 并对水解前后多糖组分的1D和2D NMR光谱特征进行分析. 实验结果表明, ASP3是一种果胶多糖. GalpA和Rhap位于多糖分子的主链, 由1→4-D-GalpA相连形成的“光滑区”(半乳糖醛酸聚糖)是其主要组成部分; 由α-(1→4)-GalpA通过O4位与α-(1→2)-和α-(1→2,4)-Rhap的O2位交替连接所形成的重复单元[→4)-α-GalpA-(1→2)-α-Rhap-(1→]构成具有较高分支的“毛发区”(富含中性糖侧链的鼠李半乳糖醛酸聚糖). Galp和Araf是中性糖侧链的主要组成, 通过Rhap残基的O4位与主链相连. 非还原性末端T-β-Galp, β-(1→3)-, β-(1→3,6)-, β-(1→4)-, β-(1→4,6)-Galp聚合形成以β-(1→3,6)-Galp为分支点的β-(1→6)-半乳聚糖和以β-(1→4,6)-Galp为分支点的β-(1→4)-半乳聚糖. T-α-Araf, α-(1→5)-Araf和α-(1→3,5)-Araf聚合形成以α-(1→3,5)-Araf为分支点的α-(1→5)-阿拉伯聚糖. 此外, 由α-(1→5)-阿拉伯聚糖通过α-(1→3)连接与β-(1→6)-半乳聚糖末端聚合形成阿拉伯半乳聚糖.     

Globo H四糖衍生物的高效合成

设计合成了2个Globo H四糖衍生物1和2, 将其作为标准样品可用于研究β1,3-葡萄糖醛酸(GlcA)转移酶及GlcA-3-O-硫酸化(Sulfo)转移酶在肿瘤组织内的特异性表达.     

新的α/β水解酶W14和W15的三维结构模建及分子对接研究

利用同源模建和分子动力学模拟方法, 模建了两个新发现的α/β水解酶超家族成员W14和W15的三维结构, 并通过与α-醋酸萘酯的对接研究, 从理论上提出Gly82和Val13为形成“氧洞”的关键残基,有利于稳定水解过程中的带负电的过渡态, 以及其它对复合物形成起到重要作用的氨基酸残基.     

聚苯乙烯热降解机理的理论研究

采用密度泛函理论B3LYP/6-311G（d）方法,对聚苯乙烯（PS）热降解反应机理进行了研究。PS热降解的主要产物是苯乙烯,其次是甲苯、α-甲基苯乙烯、乙苯和二聚体等芳烃化合物。PS热降解反应主要包括主链C-C键均裂、β-断裂、氢转移和自由基终止等反应。针对以上各类反应进行了路径设计和理论计算分析,对参与反应的分子的几何结构进行了优化和频率计算,获得了各热降解路径的标准动力学和热力学参数。计算结果表明,苯乙烯主要由自由基的链端β-断裂反应形成;二聚体主要由分子内1,3氢转移的反应形成;α-甲基苯乙烯由分子内的1,2氢转移后进行β-断裂形成;甲苯由苯甲基自由基夺取主链上的氢原子形成;乙苯由苯乙基自由基夺取氢原子形成。动力学分析表明,苯乙烯形成所需要的能垒低于其他产物形成所需要的能垒,故苯乙烯为主要的热降解产物;这与相关实验结果基本一致。     

猴金属硫蛋白MT1 α-结构域中Cys33和Cys34的突变对蛋白质稳定性的影响

重组猴金属硫蛋白MT1及其C33M,C34S和C33M/C34S突变体蛋白的蛋白质快速液相色谱(FPLC)分析表明,突变体蛋白C34S和C33M/C34S存在着两个稳定的流分f1和f2.CD光谱和重金属离子分析表明,突变体蛋白多流分不仅与半胱氨酸和Cd2+离子结合方式和构型有关,还与金属结合量有关.突变体蛋白多流分的结果表明,在把猴金属硫蛋白α-结构域中的Cys33和Cys34突变为非半胱氨酸残基以建立β-β结构域的金属硫蛋白时,可导致蛋白形成多种结构形式.这表明α-结构域在稳定金属硫蛋白的结构中起着重要的作用,半胱氨酸残基在肽链上的分布对金属硫蛋白的三级结构和金属硫簇的形成有重大的影响.     

骨螺紫及其铜配合物与人血清白蛋白相互作用的光谱学研究

采用荧光光谱法、紫外光谱法和傅里叶红外光谱法(FTIR)研究了模拟生理条件下人血清白蛋白(HSA)与骨螺紫(Mx)及其铜配合物(Mx-Cu²⁺)的相互作用. 根据荧光猝灭数据, 二元体系与三元体系中的作用机制均为静态猝灭, 在Cu²⁺存在下, HSA与Mx之间的结合常数与结合位点数明显加大, 结合两个体系的紫外吸收光谱可知, 在三元体系中, Cu²⁺与Mx形成配合物后再与HSA发生作用; 根据Förster能量转移理论, 求得Mx及Mx-Cu²⁺与HSA上氨基酸残基间的距离分别为r=2.82 nm和r=2.53 nm, 三元体系能量转移效率E′大于二元体系E, 说明Cu²⁺在结合作用中可能起到了能量转移介质的作用; 对Δλ=60 nm时的同步荧光光谱的分析表明, 在Mx及Mx-Cu²⁺作用下, HSA色氨酸残基的微区构象发生了变化, 色氨酸残基所处环境的极性增加; 运用FTIR技术定量测定了HSA与Mx及Mx-Cu²⁺作用后二级结构的变化, 发现2个体系中HSA二级结构变化情况基本一致, α-螺旋结构明显减少约8%, β-折叠也减少约1%, 而β-转角和无规卷曲分别增加了约6%和4%. 说明对HSA二级结构造成影响的主要因素是Mx, 它与HSA的结合使蛋白质分子中的肽链部分展开, 二级结构从α-螺旋和β-折叠向β-转角和无规卷曲结构转变, 分子结构的松散程度增加.     

手性Boc保护氨基酸修饰卟啉的合成及谱学研究

合成了α,α,α,β-四-[邻(叔丁氧羰丙氨酸)氨基苯基]卟啉H₂T(o-BocAla)APP(1)及其锌()配合物ZnT(o-BocAla)APP(Zn^-1),α,α,α,β-四-[邻(叔丁氧羰苏氨酸)氨基苯基]卟啉H₂T(o-BocThr)APP(2)及其锌(Ⅱ)配合物ZnT(o-BocThr)APP(Zn-2),α,α,α,β-四-[邻(叔丁氧羰酪氨酸)氨基苯基]卟啉H₂T(o-BocTyr)APP(3)及其锌()配合物ZnT(o-BocTyr)APP(Zn-3)等6种叔丁氧羰保护氨基酸修饰的卟啉.用元素分析、核磁共振、红外光谱、紫外-可见光谱以及圆二色谱等手段对其组成的结构进行了表征,并对其谱学性质进行了研究.     

野菊花中性多糖CIP-C的分离纯化及结构解析

以野菊花为原材料, 经热水提取、乙醇沉淀、DEAE-Sepharose Fast Flow和Sephacryl S-200 凝胶柱层析分离纯化, 得到1个水溶性的中性多糖CIP-C. 采用GC-MS、部分酸水解及甲基化分析等对该多糖的结构进行了解析. 结果表明, 该多糖主要由D-Man, D-Glc和D-Gal组成, 并含有少量的D-Fuc, L-Ara和D-Xyl, 其主链由β(或α)-D-1,4-Man, β-D-1,6-Glc和β-D-1,4-Gal组成, 而阿拉伯糖通过α-L-T-Araf和α-L-1,5-Araf连接形成阿拉伯聚糖支链或与β-D-1,4-Galp的O3位相连形成阿拉伯半乳聚糖支链.     

红外光谱酰胺Ⅲ带用于蛋白质二级结构的测定研究

用甲醇对BSA和RaseA等蛋白质进行变性处理,结合蛋白质酰胺带的拟合结果对酰胺带各二级结构的谱峰进行了初步指认:1330～1290cm^-1为α-螺旋;1295～1265cm^-1为β-转角;1270～1245cm^-1为无规卷曲;1250～1220cm^-1为β-折叠.依据这些谱峰归属,对一些已知二级结构的蛋白质进行了测定,所得结果与X射线衍射数据以及酰胺带的定量结果基本一致.     

桑叶多糖SJB的结构分析和蛋白酪氨酸磷酸酯酶PTP1B抑制活性

通过DEAE-纤维素和凝胶过滤柱色谱对桑叶碱提粗多糖进行分级分离, 获得均一多糖SJB, 进行结构鉴定. 采用蛋白酪氨酸磷酸酯酶PTP1B体外模型对SJB进行降血糖活性测定. 结果表明: SJB的相对分子质量为5.4×104, 由鼠李糖、阿拉伯糖、葡萄糖、半乳糖、半乳糖醛酸组成的酸性杂多糖; 主链由1,2-、1,2,4-连接的鼠李糖和1,4-、1,3,4-连接的半乳糖醛酸组成; 侧链包括末端、1,5-、1,3,5-连接的阿拉伯糖; 末端、1,4-连接的葡萄糖以及末端、1,3-、1,4-、1,6-连接的半乳糖, 主要通过鼠李糖的O4位和半乳糖醛酸的O3位与主链相连. 该多糖为首次从桑叶中获得的酸性杂多糖. 20 μg/mL SJB对PTP1B的抑制率为31.7%.     

黑果枸杞叶多糖LRLP3的结构、抗氧化活性及免疫活性

黑果枸杞叶经水提醇沉, 离子交换柱层析和凝胶柱层析分离纯化, 得到平均分子量为79400的均一多糖组分LRLP3. 对该多糖的理化性质、 结构、 抗氧化活性及免疫活性的研究结果表明, LRLP3为多分支结构, 主链为(1→3)βGalp, 大部分半乳糖6位存在分支; 支链由(1→6)βGalp, (1→4)βGalp, (1→3)βAraf, (1→3)αArap, (1→5)βAraf和(1→2,4)αRhap组成, 非还原末端由αAraf, βGalp和βGlcp组成. LRLP3具有较强的还原能力, 可显著清除1,1-二苯基-2-三硝基苯肼(DPPH)自由基、 羟自由基和超氧阴离子自由基, 有效抑制Cu²⁺/H₂O₂诱导的蛋白氧化损伤和H₂O₂诱导的细胞氧化损伤. LRLP3在体外对未经诱导和经刀豆蛋白(ConA)或脂多糖(LPS)诱导的小鼠脾细胞增殖均有促进作用.     

Structural Features of a Polysaccharide from Centella asiatica

Centella asiatica has been used as remedy for sodation, stabilization and against lepra, anabrosis1 in the oriental countries. The low-molecular-weight constituents in Centella asiatica have been investigated1. However, no polysaccharides have been reported. 1BI was the first polysaccharide isolated from C. asiatica, which had immunostimulating activity in vitro. In present study, we report the structural features of 1BI. Experimental Extraction, isolation and purification Dried C.…     

One-pot Synthesis of α,β-Dehydroamino Derivatives from β,β-Dicyanostyrene with 1,3-Dibromo-5,5-dimethylhydantoin Promoted by Mild Base

The reaction of β,β-dicyanostyrene derivatives(1) with 1,3-dibromo-5,5-dimethylhydantoin(DBDMH) was systematicly studied. The reaction could generate different products when promoted by different mild bases. When the reaction was promoted by NaOAc(100%, molar ratio to compound 1), β,β-dicyanostyrene derivatives could be directly converted into corresponding α,β-dehydroamino derivatives in good to excellent yields in one-pot. When the reaction was promoted by K₃PO₄(80%, molar ratio to compound 1), the corresponding α,β-dehydroamino and double-α,β-dehydroamino compounds were simultaneously obtained and the total conversion of β,β-dicyanostyrene derivatives was up to 90% or higher.     

Comparative Analysis of Polysaccharides from Two Ecological Types of Leymus chinensis

Leymus chinensis(Trin.) Tzvel., widely distributed at eastern Eurasian steppe and divided into gray-green type and yellow-green type, has different stress resistance to environment. In the present study, the water-soluble polysaccharides from two ecotypes of L. chinensis were analyzed in detail, and the differences between polysaccharides from the two ecotypes of L. chinensis in the yield, monosaccharide composition, molecular weight and structure were clarified. The polysaccharides of L. chinensis were composed of both neutral and acidic polysaccharides. The neutral polysaccharides contained mannose, glucose, galactose, xylose and arabinose, and mainly consisted of β-1,4-Glcp, α-1,3-Galp and α-1,2-Xylp residues. The acidic polysaccharides contained mannose, rhamnose, glucuronic acid, galacturonic acid, glucose, galactose, xylose and arabinose. However, the yields, monosaccharides contents and the molecular weights of the polysaccharides from the two ecotypes of L. chinensis were different. Moreover, the resistance type(gray-green type) of L. chinensis contained a number of α-1,3-Manp and reducing end of β-Glcp residues, and much more O-methyl groups than normal type(yellow-green type) of L. chinensis. The differences of the polysaccharides of the two ecotypes of L. chinensis might be due to the long-term environmental adaptability of plant, and the differences of the polysaccharides might influence the stress resistance of L. chinensis.     

The core structure of ukonan A, a phagocytosis-activating polysaccharide from the rhizome of Curcuma longa, and immunological activities of degradation products.

The controlled Smith degradation of ukonan A, a phagocytosis-activating polysaccharide isolated from the rhizome of Curcuma longa L., was performed. The reticuloendothelial system-potentiating, anti-complementary and alkaline phosphatase-inducing activities of ukonan A and its degradation products were investigated. Methylation analyses of both the primary and the secondary Smith degradation products indicated that the core structural features of ukonan A include a backbone chain mainly composed of beta-1,3-linked D-galactose, beta-1,4-linked D-xylose and alpha-1,2-linked L-rhamnose residues. All of the galactose units in the backbone carry side chains composed of alpha-L-arabino-beta-D-galactosyl or beta-D-galactosyl residues at position 6. Ukonan A has a remarkable effect on each of the three kinds of immunological activities. Periodate oxidation caused pronounced decrease or disappearance of the activities, but the controlled Smith degradation product having the core structure of polysaccharide showed considerable restoration of these activities.     

Isolation and structural characterisation of okara polysaccharides

Okara is a byproduct generated during tofu or soymilk production processes. Crude polysaccharide (yield 56.8%) was isolated by removing fat, protein and low molecular weight carbohydrates from initial okara. Crude okara polysaccharide was further divided into four soluble fractions and an insoluble residue fraction by extracting with 0.05 M EDTA + NH(4) oxalate, 0.05 M NaOH, 1 M NaOH and 4 M NaOH, with yields of 7.7%, 3.6%, 20.7%, 16.0% and 27.9%, respectively. Arabinose, galactose, galacturonic acid, xylose and glucose (only for the insoluble fraction) were the major constituent sugars. The primary sugar residues of okara polysaccharides were 1,4-linked β-galactopyranose, 1,5- and 1,3-linked α-arabinofuranose, 1,5-linked α-xylofuranose, 1,2-linked, 1,2,4-linked and terminal α-rhamnopyranose (or fucopyranose), and 1,4-linked β-glucopyranose (only for the insoluble fraction), indicating okara polysaccharides might contain galactan, arabinan, arabinogalactan, xylogalacturonan, rhamnogalacturonan, xylan, xyloglucan and cellulose.     

免疫亲和固相萃取-超高效合相色谱-串联质谱法同时测定牛奶中6种玉米赤霉醇类化合物残留

建立了免疫亲和固相萃取（IAC-SPE）-超高效合相色谱-串联质谱（UPC²-MS/MS）同时测定牛奶中α-玉米赤霉醇、β-玉米赤霉醇、α-玉米赤霉烯醇、β-玉米赤霉烯醇、玉米赤霉烯酮和玉米赤霉酮残留的分析方法。样品用去离子水稀释,经IAC-SPE富集净化后,采用Waters ACQUITY UPC² Torus 2-PIC色谱柱（50 mm×3.0 mm,1.7 μm）分离,以超临界CO₂和0.1%（v/v）甲酸甲醇溶液为流动相,经梯度洗脱后在ESI^-模式下检测。经过稀释离心的牛奶样品采用免疫亲和柱净化后没有明显的基质效应,6种目标化合物在1~200 ng/mL范围内线性关系良好,相关系数（r²）≥0.9957;6种目标化合物在3个加标水平下的平均回收率为75.9%~106.5%,日内和日间精密度均≤11.4%。该法专属性好,操作简便,有机溶剂使用量小,与已有的样品测定方法比较更绿色环保,可用于牛奶中α-玉米赤霉醇、β-玉米赤霉醇、α-玉米赤霉烯醇、β-玉米赤霉烯醇、玉米赤霉酮和玉米赤霉烯酮的残留检测。