微藻多糖生物活性研究进展

微藻是一种在海洋和陆地广泛存在的藻类,其含有的多糖一般为酸性杂多糖,具有多种生物活性。本文概述不同微藻多糖的结构特点和生物活性,并对其研究进展作一展望。     

多糖生物活性的研究进展

多糖具有多种生物活性作用,随着生物学、化学等学科的飞速发展,多糖的研究受到越来广泛的重视。多糖在抗肿瘤、抗病毒、降血糖、抗凝血、抗炎、抗衰老等方面发挥着重要的生物活性作用,所以多糖也逐渐成为当今新药开发的重要方向之一。但由于多糖结构的复杂性,多糖的构效关系研究并不完善,要真正彻底研究多糖的活性作用,还需要化学、生物学、药学以及药理学工作者的密切合作。     

芦笋多糖的研究进展

芦笋中的多糖具有多种生物学功能,如抗肿瘤、抗衰老、免疫调节等,在食品、医药等领域具有广阔的应用前景。此文对芦笋多糖的提取分离、结构分析及生物活性研究进展进行综述,为芦笋多糖的研究提供参考。     

活性海洋多糖的功能及结构研究概况

海洋生物多糖具有抗肿瘤、抗病毒、降血糖、调血脂、抗炎、抗衰老等多种生物活性作用,多糖的生物活性与其结构密切相关。本文总结了海洋多糖种类、生物活性、结构以及分析方法的研究进展,并概括的论述了活性多糖的构效关系。     

海参多糖结构表征的研究进展

海参多糖是1种富含硫酸基团的杂多糖，结构复杂，具有多种生物活性，其生物活性与海参多糖本身的化学组成、相对分子质量、硫酸化模式等结构特征息息相关。为了更好地研究海参多糖的生物活性，全面总结海参多糖结构的分析方法，综述海参中性聚糖、海参岩藻糖基化硫酸软骨素和海参岩藻聚糖硫酸酯的结构特征，以期为海参多糖的生物活性及构效关系等后续研究提供理论基础。     

海洋动物多糖研究进展

随着海洋生物资源进一步开发和糖化学与糖生物学研究的兴起,海洋生物多糖因具有独特的结构和多种生物活性而越来越受到人们的关注。本文主要对海洋动物多糖的提取分离、结构组成分析以及生物活性方面的研究进展加以综述,以期为海洋动物多糖的深入研究和开发提供参考。     

灵芝多糖的研究进展

灵芝多糖是灵芝中的一种重要活性物质,具有免疫调节、抗肿瘤、抗氧化、抗衰老以及活血化瘀等多种生物活性。灵芝多糖已成为目前研究的一大热点,具有很大的开发利用价值。本文综述了目前在灵芝多糖提取、分离纯化、含量测定、结构分析和生物活性方面的研究情况,并对灵芝多糖的发展利用前景做了展望。     

海藻多糖的化学结构及生物活性研究新进展

多糖是海藻中一类重要的生物活性物质,近年来已引起国内外学者的广泛重视。大量研究表明,海藻多糖化学结构新颖、复杂,具有免疫调节、抗肿瘤、抗氧化、抗病毒和防治心血管疾病等多种药理活性。本文主要从海藻多糖的化学结构和生物活性2个方面对海藻多糖的研究进展进行综述,为后期对海藻多糖的深入研究和开发功能性食品或药品提供一定的理论指导。     

香菇多糖结构修饰研究进展

目的　对香菇多糖化学结构的修饰方法及其生物活性进行系统总结。方法　通过查阅近年来中英文相关文献,对香菇多糖已经报道的化学结构修饰方法及修饰后的生物活性进行了系统分析,总结阶段性进展。结果　香菇多糖结构修饰方法有化学修饰,包括硫酸化、羧甲基化、磷酸化及与金属离子螯合法等,物理修饰和生物修饰法等。不同的修饰方法对香菇多糖的生物活性有较大的影响。结论　结构修饰及其药理活性的深入研究仍是香菇多糖一个重要的研究方向。     

海洋生物活性多糖的研究进展

随着海洋生物活性的研究进展，人类在海洋生物开发研究方面取得很大成就。多糖是海洋生物活性物质，研究表明具有多种生物活性和药用作用，如抗肿瘤、抗病毒、抗心血管疾病、抗氧化和免疫调节等。     

Effect of D-amino acid substitution on the stability, the secondary structure, and the activity of membrane-active peptide

Several diastereomers and an enantiomer of KKVVFKVKFKK, an antimicrobial peptide that acts on the lipid membrane of pathogens were synthesized to investigate the effect of D-amino acid substitution on stability, secondary structure, and activity. The stability of the peptide in serum was improved greatly by the D-amino acid substitutions. D-Amino acid substitutions at the N- and/or C-terminal of the peptide, which had little effect on the alpha-helical structure, and all D-amino acid substitutions that formed a left-handed alpha-helix maintained antimicrobial activity, whereas D-amino acid substitutions in the middle of the amino acid sequence disrupted the alpha-helical structure, resulting in the complete loss of activity. This result confirmed that the peptide did not interact with chiral receptors, enzymes, or any chiral component of the membrane. D-Amino acid substitutions at the termini reduced the inhibition of the activity by heat-inactivated serum, which indicated that local change of chirality or change of secondary structure induced by D-amino acid substitutions might affect the interactions between the peptide and certain components in the serum. The present study suggests that partial D-amino acid substitution is a useful technique to improve the in vivo activity of antimicrobial peptides.     

白桦脂酸衍生物的合成修饰及其抗菌活性研究

目的：设计白桦脂酸（BA）的新型衍生物结构，研究其及衍生物的体外抗菌活性。方法：通过Jones氧化反应、Claisen Schmidt缩合反应等得到目标化合物BA-01；采用96孔板的琼脂稀释法测定化合物对5种细菌的最小抑菌浓度（MIC）。结果：合成了一种具有新型结构的BA衍生物，且为首次报道的新化合物，其结构通过¹H NMR，¹³C NMR和MS（ESI）等表征分析确定。体外抗菌活性测试结果表明，目标化合物对3种革兰阳性菌均有显著的抑菌活性，其中对金黄色葡萄球菌的抑菌活性最高，其最小抑菌浓度（MIC）为12.5 μmol·L^-1，与BA相比显著提高。结论：合成修饰的新型结构中C-3位羟基的修饰以及C-2位上苯环的连接对其生物活性具有重要影响，值得进一步深入探究。     

Synthesis and antitumour activity of new derivatives of flavone-8-acetic acid (FAA). Part 4: Variation of the basic structure

A range of 11 derivatives of flavone-8-acetic acid (FAA) in which the structure has been substantially altered in different ways have been prepared and their anti-tumour activity evaluated in vitro against a panel of human and murine tumour cell lines and in vivo against MAC 15A. The generally poor activity observed shows that the basic structure cannot be altered much without destroying the activity.     

Model system to study the influence of aggregation on the hemolytic potential of silica nanoparticles

A well-defined silica nanoparticle model system was developed to study the effect of the size and structure of aggregates on their membranolytic activity. The aggregates were stable and characterized using transmission electron microscopy, dynamic light scattering, nitrogen adsorption, small-angle X-ray scattering, infrared spectroscopy, and electron paramagnetic resonance. Human red blood cells were used for assessing the membranolytic activity of aggregates. We found a decreasing hemolytic activity for increasing hydrodynamic diameter of the nanoparticle aggregates, in contrast to trends observed for isolated particles. We propose here a qualitative model that considers the fractal structure of the aggregates and its influence on membrane deformation to explain these observations. The open structure of the aggregates means that only a limited number of primary particles, from which the aggregates are built up, are in contact with the cell membrane. The adhesion energy is thus expected to decrease resulting in an overall lowered driving force for membrane deformation. Hence, the hemolytic activity of aggregates, following an excessive deformation of the cell membrane, decreases as the aggregate size increases. Our results indicate that the aggregate size and structure determine the hemolytic activity of silica nanoparticle aggregates.     

Comparative Study to Predict Dipeptidyl Peptidase IV Inhibitory Activity of β-Amino Amide Scaffold

Comparative study was performed on 34 β-amino amide derivatives as dipeptidyl peptidase IV inhibitors in order to determine their structural requirement to enhance the antidiabetic activities. Hologram quantitative structure activity relationships models utilized specialized fragment fingerprints (hologram length 353) which showed good predictivity with cross-validated q² and conventional r² values of 0.971 and 0.971, respectively. Models were validated and optimized by a test set of eight compounds and gave satisfactory predictive ability. Hologram quantitative structure activity relationships maps were helpful in prediction of the structural features of the ligands to account for the activity in terms of positively and negatively contributing towards activity. The information obtained from maps could be effectively use as a guiding tool for further structure modifications and synthesis of new potent antidiabetic agents.     

灯盏乙素苷元4’-N-取代氨甲基苯甲酸酯的合成与活性研究

目的合成具有较强神经细胞氧化损伤保护作用的灯盏乙素苷元4’-N-取代氨甲基苯甲酸酯衍生物。方法灯盏乙素苷元与N-取代氨甲基苯甲酸在偶联剂N,N’-二环己基碳酰亚胺(DCC)/二甲基吡啶(DMAP)的作用下缩合后者经过酰氯/甲醇体系脱保护基,获得目标化合物(6a～6c)。并对受试化合物进行了神经细胞氧化损伤保护活性研究。结果合成的化合物及中间体均经过1H-NMR,ESI-MS进行了结构表征,确证结构与目标产物一致,受试化合物均具有较好的抗氧化活性,其中化合物6c活性明显好于维生素E、灯盏乙素。结论 4’-N-取代氨甲基苯甲酸酯前药设计方法能用于灯盏乙素苷元结构修饰,所采用的合成方法具有较好的实用性,能用于灯盏乙素苷元4’-N-取代氨甲基苯甲酸酯的制备。     

THE INFLUENCE OF ESTERIFICATION OF CARBOXYL GROUPS OF RIBONUCLEASE-A ON ITS STRUCTURE AND IMMUNOLOGICAL ACTIVITY

The effect of modification of carboxyl groups of Ribonuclease-A^a on the enzymatic activity and the antigenic structure of the protein has been studied. Modification of four of the eleven free carboxyl groups of the protein by esterification in anhydrous methanol/0.1 M hydrochloric acid resulted in nearly 80% loss in enzymatic activity but had very little influence on the antigenic structure of the protein. Further increases in the modification of the carboxyl groups caused a progressive loss in immunological activity, and the fully methylated RNase-A exhibited nearly 30% immunological activity. Concomitant with this change in the antigenic structure of the protein, the ability of the molecule to complement with RNase-S-protein increased, clearly indicating the unfolding of the peptide “tail” from the remainder of the molecule. The susceptibility to proteolysis, accessibility of methionine residues for orthobenzoquinone reaction and the loss in immunological activity of the more extensively esterified derivatives of RNase-A are suggestive of the more flexible conformation of these derivatives as compared with the compact native conformation. The fact that even the fully methylated RNase-A retains nearly 30% of its immunological activity suggested that the modified protein contained antibody recognizable residual native structure, which presumably accommodates some antigenic determinants.     

Synthesis and antibacterial properties of pyrimidine derivatives

The paper presents the synthesis of 1,2,3,7-tetraaryl-1,2,3,4-tetrahydropyrimido[4,5-d]pyrimidines. The structures of the obtained compounds were confirmed by crystallographic and spectroscopic analyses, and their antibacterial activity was tested on 9 selected strains, comparing chemical structure changes with increased microbiological activity. It was confirmed that aromatic residues in the hydrogenated pyrimidine ring constitute a significant element influencing antibacterial activity. Electronegative radicals increase microbiological activity, but decrease solubility of the compounds. Therefore, substituents should be selected in a manner ensuring a balanced effect. The presented crystal structure of 6f includes two stereoisomers, which we decided to isolate and compare the microbiological properties in further studies.     

Computer methods for the assessment of toxicity.

Abstract The prediction of the biological activity of chemical compounds by means of mathematical models is discussed. Biological activity of chemicals, including their toxicity on man and other biological organisms and systems, involves too complex phenomena to presently be predictable by fundamental models such as ab initio quantum mechanical models or statistical mechanical models. Hence one takes recourse to semi-empirical and empirical models which relate the variation in chemical structure of chemical compounds to the variation in their measured biological activity, e.g. toxicity in one or several test systems. These models are “calibrated” on series of similar compounds with “known” toxicity, the training set. Thereafter the models can — in fortunate cases — be used to predict the toxicity of compounds which are structurally similar to the training set compounds. The formulation and applicability of semi-empirical and empirical models relating chemical structure to biological activity is discussed. Causes and remedies for commonly encountered fallacies are presented.