Maillard反应的高分子产物的研究进展

Maillard反应产物由于其天然性和独特的香味,使其在食品和烟草领域的应用倍受关注.目前,对Maillard反应产物中的小分子化合物的研究已经比较透彻,但是高分子产物的结构及形成机理尚不清楚.虽然Maillard高分子产物及其复杂,但人们通过膜透析、凝胶柱层析等分离方法,对其提纯分级后,再运用凝胶渗透色谱、元素分析、放射性同位素标记、紫外-可见光谱、红外光谱、核磁共振(NMR)、热裂解等分析手段对其进行表征,对Maillard高分子产物的结构和形成机理有了一定的了解.本文对Maillard反应的高分子产物的分离提纯方法、分析表征方法和分子结构的假设模型三方面的研究进展进行了综述.     

色谱手性分离研究

手性是自然界的基本属性之一,不同的手性单体具有不同的生理活性,将手性化合物有效的分离具有十分重要的意义.色谱法和膜分离法在拆分手性化合物中得到了越来越广泛的应用,也是我们课题组采用的主要方法.就近几年来拆分手性化合物的一些方法和研究成果本文进行综述,并对今后手性拆分技术的发展方向进行了展望.     

荧光法研究Ge-132对牛血清白蛋白Maillard反应的抑制作用

人体内氨基酸及蛋白质的非酶糖化反应(Maillard反应)与糖尿病及其并发症的关系已经引起广泛注意[1].有机锗化合物β-羧乙基锗倍半氧化物(Ge-132)具有预防糖尿病及调节糖代谢的作用[2].     

液相色谱手性拆分机理的热力学方法研究

手性识别是分子识别的一个重要组成部分。液相色谱手性拆分机理研究有助于色谱条件的优化和新型手性固定相的设计,也有助于理解手性识别机制。本文就线性色谱与非线性色谱条件下手性拆分过程对应热力学参数的推求方法进行了评述,阐述了相关热力学参数的涵义及其在色谱保留及手性拆分机理探讨中的应用,并展望了该领域的研究前景。     

液相色谱手性拆分机理的热力学方法研究

手性识别是分子识别的一个重要组成部分。液相色谱手性拆分机理研究有助于色谱条件的优化和新型手性固定相的设计,也有助于理解手性识别机制。本文就线性色谱与非线性色谱条件下手性拆分过程对应热力学参数的推求方法进行了评述,阐述了相关热力学参数的涵义及其在色谱保留及手性拆分机理探讨中的应用,并展望了该领域的研究前景。     

液相色谱手性拆分机理的热力学方法研究

手性识别是分子识别的一个重要组成部分.液相色谱手性拆分机理研究有助于色谱条件的优化和新型手性固定相的设计,也有助于理解手性识别机制.本文就线性色谱与非线性色谱条件下手性拆分过程对应热力学参数的推求方法进行了评述,阐述了相关热力学参数的涵义及其在色谱保留及手性拆分机理探讨中的应用,并展望了该领域的研究前景.     

一种新的液相色谱检测器——抑制化学发光反应检测器

化学发光分析法以其仪器设备简单、操作方便、分析快速、灵敏度高、线性浓度范围宽等显著优点,引起人们极大的兴趣。然而,由于化学发光反应固有的选择性差的缺点,使得这种高灵敏检测方法在分析应用中受到很大限制。如何将高灵敏度的化学发光检测法与高选择性的物理或化学手段相结合,这     

Atherton-Todd反应及其立体化学机理研究进展

本文总结了近几十年来对含有P-H键的四配位和五配位磷化合物的Atherton-Todd反应的研究,尤其对其立体化学反应机理研究进行了详尽的叙述.自发现Atherton-Todd反应之后,虽然对其反应机理进行了几十年的研究,但前期工作主要集中在反应中间体的研究.直至近十几年来,才分别对含有P-H键的四配位和五配位磷化合物的Atherton-Todd反应的立体化学机理进行了较详细的研究,但至今仍缺乏对其立体化学机理全面的综述和介绍,希望本文可以弥补文献不足,不仅对Atherton-Todd反应有个客观全面的介绍,而且对于其立体化学反应机理的研究也进行详细的综述.对于Atherton-Todd反应立体化学机理的深入研究将有助于设计合成新型的具有光学活性的四配位和五配位磷手性中心的化合物.     

Determination of acrylamide formed in asparagine/D-glucose maillard model systems by using gas chromatography with headspace solid-phase microextraction

A gas chromatographic method, along with a headspace solid-phase microextraction (HS-SPME), was developed for the determination of acrylamide formed in Maillard reaction model systems. The developed method was validated by liquid chromatography/mass spectrometry. A headspace sample was collected from an aqueous acrylamide solution (100 microg/mL) by SPME and directly injected into a gas chromatograph equipped with a nitrogen-phosphorus detector. The recovery of acrylamide from an aqueous solution was satisfactory, i.e, >93% under the conditions used. Acrylamide formed in an asparagine/D-glucose (molar ratio, 1/2) Maillard reaction model system heated at 150 and 170 degrees C for 20 min was collected and analyzed by the newly developed method using gas chromatography with nitrogen-phosphorus detection and HS-SPME. The amounts of acrylamide were 318 +/- 33 microg/g asparagine from a sample heated at 150 degrees C and 3329 +/- 176 microg/g asparagine from a sample heated at 170 degrees C. Addition of cysteamine or glutathione to the above model system reduced acrylamide formation. Acrylamide formation was not observed when cysteamine or glutathione was added to asparagine in the above model systems to obtain equimolar concentrations of both compounds. This newly developed method is simple and sensitive, and requires no solvent extraction.     

Vibrational spectra and stereochemistry of mono-and polysaccharides. II. α-anomers of D-glucose and D-galactose. Glucitol and galactitol

The IR and Raman spectra of D-glucose and D-galactose α-anomers are compared with the corresponding spectra of the related polyatomic alcohols glucitol and galactitol. Experimental data on the frequencies and modes of normal vibrations and on the contributions of normal vibrations involving particular skeletal CiOi and CiC(i+1) bonds to the potential energy distribution (PED) are compared with the results of theoretical calculations. The α-anomers of D-glucose and D-galactose with different configurations of the C4C4 and C4H4 bonds are characterized by substantially different sets of frequencies with prevailing contributions to PED from the CiOi and CiC(i+1) bonds. The similar bonds of glucitol and galactitol are also characterized by specific frequency sets. Particular CiOi and CiC(i+1) bonds have different numbers of “localized” frequencies. B. I. Stepanov Institute of Physics, Belarus Academy of Sciences. V. Tshebyatovski Institute of Low Temperatures and Structural Studies, Polish Academy of Sciences. Translated fromZhurnal Strukturnoi Khimii, Vol. 36, No. 3, pp. 431–442, May–June, 1995. Translated by I. Izvekova     

CdTe纳米晶与苯丙氨酸相互作用的研究

以巯基乙酸为稳定剂,在水相中合成了CdTe纳米晶,通过考察红外光谱、紫外光谱和光致发光光谱的变化,确定了苯丙氨酸(Phe)对CdTe纳米晶的光致发光效率以及稳定性的影响.结果表明苯丙氨酸与CdTe纳米晶之间存在着较强的相互作用,这种作用导致CdTe纳米晶的发光强度增大,稳定性增强,苯丙氨酸不仅是配位剂,它同时又起到了稳定剂的作用,并初步确认这种加强和稳定作用来自于苯丙氨酸和CdTe纳米晶之间所形成的配位键和静电作用以及苯丙氨酸与巯基乙酸之间形成的氢键.此外,苯丙氨酸的特殊结构对防止纳米晶的聚集有很大作用.     

Fluctuation dynamics of chemiluminescence in the maillard reaction

The general problems of information deriving from the oscillation kinetics of Belousov-Zhabotinsky reactions were discussed. The discussion was organized around a particular example of the complex fluctuation dynamics of the Maillard reaction, i.e., a multistage reaction between a carbonylcontaining compound and the nucleophilic amino group of an amino-containing compound at different temperatures, as visualized by chemiluminescence. Flicker-noise spectroscopy served as methodological background of the fluctuation analysis comprising the two main steps: separation of low-frequency components attributed to resonances and their interference, from the source signals and analysis of the remaining chaotic components. Possibility of modeling the chaotic dynamics of fluctuations of the measured dynamic variables in terms of anomalous diffusion was shown.     

Analogies between silicon and phosphorus stereochemistry—II : Influence of the attacking anion upon the stereochemistry of nucleophilic displacement at tetrahedral phosphorus

The stereochemistry of reactions of cyclic halogenophosphates with a representative series of p-substituted aryloxides emphasizes the relative influence of the attacking anion. For a given leaving group, the stereochemistry depends essentially upon the electronic character of the p-substituent and the ion-pair dissociation of the nucleophile. Both stereochemical and kinetic data rule out a cation-assisted mechanism to explain retention at phosphorus. Meanwhile, a comparison between S_N2(P) and S_N2(Si) suggests similar mechanisms in the two series. Retention and/or inversion are the consequence of two competing reactions of similar energies. The stereochemistry is determined by the factors which affect the approach of the nucleophile to give two initial intermediates of different geometries.     

On the stereochemistry of photoaddition between α,β-unsaturated ketones and olefins

The stereochemistry of the photoaddition between α,β-unsaturated ketones and olefins is discussed. It is shown that the stereochemistry of the product is determined by the relative stability of the excited state. This stability can be judged by the application of the principles of conformational analysis, coupled with the assumption that the β-carbon of the excited state is pyramidal and can select the more stable configuration. Many examples derived mainly from synthetic work performed at the University of New Brunswick during the last ten years are in agreement with these assumptions.     

Correlation between the stereochemistry and optical activity of chiral dimolybdenum tetracarboxylates and related compounds

Sector rules for chiral dimolybdenum tetracarboxylates and related compounds were derived using the one-electron model of optical activity. The correlation between the sign of the Cotton effect (CE) of the ^* transition and the stereochemistry of this type of binuclear clusters is expressed as a rule of 16 in which the positive sign of the EC corresponds to the negative sign of the pseudoscalar function xyz(x²-y²) of the cluster atoms. A negative sign of the CE was predicted for the ^* transition in cis-(L-isoleucine)₂(NCS)₄Mo₂.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1504–1507, July, 1990.We would like to thank M. A. Porai-Koshits and A. A. Levin for becoming acquainted with the research and discussing the results obtained.     

Diels-Alder reactions between dienamides and quinones: stereochemistry of the cycloadditions and cytotoxic activity of the adducts

Tetrahydronaphthoquinones and tetrahydroanthraquinones bearing an amido group have been prepared by Diels-Alder reactions between (E)-1-(N-carbobenzyloxyamino)-1,3-butadiene (2) or (E)-1-(N-benzoyl-N-benzylamino)-1,3-butadiene (5) and benzoquinone or 5-substituted naphthoquinones. The stereochemistry of the cycloadditions was investigated. A high regioselectivity was observed in the reaction of the diene carbamate 2 with 5-methoxy and 5-acetoxy naphthoquinones. This latter gave the unexpected 1,8-regioisomer 3d. The cycloadditions of the dienamide 5 with naphthoquinones 1 (R = OH, OMe, OAc) are regiospecific. Assignment of the structure of the tetrahydroanthraquinone 6b is in good agreement with the known directing effect of the 5-hydroxy group of juglone 1b in analogous Diels-Alder reactions. With 5-methoxy and 5-acetoxy naphthoquinones, the opposite regiochemistry observed is consistent with the electron-donating influence of the methoxy or acetoxy group, making the C-3 carbon atom more electron deficient. Aromatization of the adducts 6b and 7c was accompanied by an unusual elimination of the amido moiety. Thus, 1-hydroxy and 1-methoxy anthraquinones were obtained. Reactions of the dienes 2 and 5 with benzoquinone gave the tetrahydronaphthoquinones 9 and 10 with an endo stereospecificity. Oxidation of 9 by activated manganese dioxide gave the naphthoquinone 11. These compounds were submitted to in vitro cytotoxic assays towards murine L 1210 leukemia cells and clonogenic human tumor cell line MDA-MB 231. The naphthoquinone derivatives 9, 10 and 11 had significant activities with IC50 less than or equal to 0.4 microgram/ml towards these two tumor cell systems.