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.     

一种新的磷酸根离子敏感电极研究

一种新的磷酸根离子敏感电极研究肖丹，俞汝勤，李军，袁孔铨（湖南大学化学化工系，长沙，４１００８２）关键词磷酸根，离子选择电极，磷酸二氢根磷酸根离子浓度的测定在化学化工、环境保护、生命科学和临床医学等领域有着重要的意义。对磷酸根离子敏感电极的研究和探索...     

Analysis of betamethasone, dexamethasone and related compounds by liquid chromatography/electrospray mass spectrometry

A reversed-phase high-performance liquid chromatography/electrospray ionisation mass spectrometry (HPLC/ESI-MS) method has been developed to conclusively differentiate the epimers betamethasone and dexamethasone and various esterification products (betamethasone and dexamethasone 21-acetate, betamethasone and dexamethasone 21-phosphate, betamethasone 17-valerate, betamethasone 21-valerate and betamethasone 17,21-dipropionate) in counterfeit drugs. Good separation with baseline resolution of all epimers or isomers was obtained on a Zorbax Eclipse XDB or Luna C8 column, using a step gradient with mobile phases of 0.05 M ammonium acetate and acetonitrile. Betamethasones can also be distinguished by the relative abundance of their m/z 279 ion in the positive electrospray tandem mass spectra. The LC/MS or LC/MS/MS method developed was successfully applied to the analysis of drug product samples, i.e. creams and tablets.     

Polymer-Titanium hybrids obtained by radical polymerization and Sol-Gel process

The possibility to prepare hybrids made by poly(vinyl acetate) (PVAc), poly(methyl methacrylate) (PMMA) and/or poly(ethyl acrylate) (PEtA) with TiO₂ was studied. The processes of polymer formation-radical polymerization and sol-gel process for inorganic network —were achieved simultaneously. Due to a high reactivity of titanium isopropoxide (TIP) in the sol-gel process, a complexant comonomer, allyl acetoacetate (AlAcAc), was used. Covalent bonds between polymer and inorganic chains were obtained by addition of trialkoxysilane derivates with vinyl (VTES) or methacryloyl (MPTS) groups. The presence of TIP inhibits the radical polymerization of vinyl acetate (VAc). The PVAc-TiO₂ hybrids were produced by the sol-gel process of TIP in the presence of pre-obtained PVAc. Except for VTES and MPTS, trialkoxysilane derivates with methyl (MeTES), octyl (OTES) and phenyl (PTES) groups were used. The thermal stability of hybrids is strongly affected by TiO₂ presence and by the type of trialkoxysilane derivates. The thermal stability of PVAc hybrids decreases in the presence of TiO₂ inorganic network. The glass transition temperature of polymers increases in the presence of the inorganic network.     

Fragmentation processes of methylbutyl trifluoroacetates studied by tandem quadrupole mass spectrometry and isotope labeling

The fragmentation patterns of 3-methyl-2-butyl trifluoroacetate and 2-methyl-2-butyl trifluoroacetate were investigated by GC/MS/MS, with electron impact and collision-induced dissociation, on regular and isotope-labeled (deuterium and ¹⁸O) esters. The atoms found in various fragments could be traced back to specific positions in the parent molecules. In this way, molecular rearrangements potentially occurring during the formation of esters by trifluoroacetolysis of 3-methyl-2-butyl p-toluenesulfonate or trifluoroacetic acid addition to various 2-methylbutenes could be shown. Rearrangements also occurred during the fragmentation, particularly during the expulsion of the small fragments CO, C₂H₄ and F₂CO. For the decompositions of oxygen-containing ions these rearrangements were highly specific. By contrast, alkyl cations lead to fragments that are fully scrambled (statistical label distribution). Alkene radical cations ([C_nH_2n]^{+ ˙}) fragment to daughter ions that are extensively, but less than statistically scrambled. Hydrogen scrambling may also occur in fluoroalkyl cation fragments.     

榆耳水溶性多糖的结构特征

用3%三氯醋酸从榆耳子实体中提取出水溶性粗多糖,经乙醇分级、SepharoseCL6B纯化得到单一组分GIA.SepharoseCL6B柱层析测得GIA的相对分子质量为1 26×105.GC分析表明GIA由Man和Glc两种单糖构成,其物质的量比为1 42∶1.多糖GIA经部分酸水解、高碘酸氧化、Smith降解和甲基化分析其结构主要为β(1→3)Man和β(1→3)Glc,且在6～0处构成分枝结构,平均每11个己糖残基有2个分枝,多糖GIA的支链部分由(1→4)Glc构成,末端残基为Man,Glc.     

Charge transfer and electron backdonation in metallofullerenes encapsulating NSc3

Orbital interaction analysis is employed to understand the complex charge transfer mechanism operative in endohedral metallofullerenes of composition NSc₃@C_n (n = 68, 78). This phenomenon combines substantial electron transfer from the core to the cage with electron backdonation, involving the interaction between the occupied orbitals of the negatively charged cage and the unoccupied d orbitals of the positively charged core. This electron backdonation differs fundamentally from conventional orbital hybridization, which takes place primarily between the HOMO of the metal core and the LUMO of the fullerene cage. These findings imply the pronounced stability of NSc₃@C_n (n = 68, 78), especially for NSc₃ encapsulated in the non-IPR C₆₈ enclosure, as experimentally established.     

Single and double hydrogen migration in the fragmentation of 3-methyl-2-butyl trifluoroacetate

Three of the main oxygen-containing fragments resulting from 3-methyl-2-butyl trifluoroacetate (11) had been identified previously as the 1-triflnoroacetoxyethyl cation (m/z 141, 12, product of simple cleavage), and the products of single (m/z 142) and double hydrogen transfer (m/z 143, protonated ethyl trifluoroacetate). Collisionally activated dissociation of m/z 142 and the isotopomers resulting from 11-2-d, 11-1-d₃, 11-5,6-d₆, and 11-¹⁸O₂ has established that m/z 142 is the oxygen protonated 1-trifluoroacetoxyethyl free radical (17) formed by hydrogen shift irom a γ-methyl group to oxygen in the molecular ion, rather than in a complex (18) between 12 and the 2-propyl free radical, as expected based on a mechanistic model existing in the literature. The second hydrogen transferred originates in the other γ-methyl group; its migration may occur, but does not have to, in the complex between 17 and a molecule of propene, prior to dissociation of the two fragments. Collision-activated dissociation has now shown that the m/z 140 ion observed in the spectrum is the molecular ion of vinyl trifluoroacetate, possibly formed by a hydrogen transfer from 12 to the 2-propyl radical in the complex 18. The hydrogen migration to oxygen exhibits no isotope effect, whereas the transfers to carbon atoms exhibit small primary and α secondary kinetic isotope effects. Exclusive migration of the tertiary hydrogen from C(3) occurs in the formation of 2-methylbutene cation radical (m/z 70) from the molecular ion. The hydrocarbon ion fragments and the heteroatom-containing fragments are formed from 11 by disjoint pathways.     

对固体圆二色光谱测试方法的再认识——兼谈“浓度效应”

对近期发展的固体圆二色(CD)光谱测试方法进行了概述、评价和比较, 着重探讨了“浓度效应”的存在使固体CD光谱失真的原因. 通过对本课题组和其他作者已报道的四种化合物的固体CD谱再测试的反思, 强调了依手性化合物的手性光谱学性质不同, 根据浓度梯度实验选择其合适测试浓度的必要性. 对固有手性的阻转异构化合物(S)-1,1'-联二萘酚(S-BINOL)进行了成膜法固体CD谱浓度梯度测试, 发现所得固体薄膜CD谱中也存在着“浓度效应”     

对固体圆二色光谱测试方法的再认识——兼谈“浓度效应”

对近期发展的固体圆二色(CD)光谱测试方法进行了概述、评价和比较, 着重探讨了“浓度效应”的存在使固体CD光谱失真的原因. 通过对本课题组和其他作者已报道的四种化合物的固体CD谱再测试的反思, 强调了依手性化合物的手性光谱学性质不同, 根据浓度梯度实验选择其合适测试浓度的必要性. 对固有手性的阻转异构化合物(S)-1,1'-联二萘酚(S-BINOL)进行了成膜法固体CD谱浓度梯度测试, 发现所得固体薄膜CD谱中也存在着“浓度效应”