Chemical Synthesis of Proteins Containing 300 Amino Acids

Chemical synthesis of proteins containing up to 300 amino acids may cover 30%-50% of all the proteins encountered in biomedical studies and may provide an alternate approach to the usually used recombinant expression technology, vastly expanding the chemical space of the latter. In the present review article, we tried to survey the recent progresses made for more rapid synthesis of increasingly long peptides and more efficient ligation of multiple peptide segments. The developments of seminal methods by many research groups have greatly contributed to the recent breakthroughs in the successful total synthesis of a number of functionally important proteins, such as oligoubiquitins, bacterial GroEL/ES chaperones, and mirror-image DNA polymerases. Through these studies, a potential bottleneck has also been recognized for the chemical synthesis of large proteins, namely, how to ensure that each peptide segment from a large protein avoids unfavorable aggregation when dissolved in aqueous solution. Many new methods, such as removable backbone modification(RBM) strategy have been developed to overcome this bottleneck, while more studies need to be carried out to develop more effective and less costly methods that ultimately, may lead to fully automatable chemical synthesis of customized proteins of 300 amino acids bearing any artificial designs.     

Polarographic Study of the Antioxidant Activity of Amino Acids and Proteins

Classical polarography and cyclic voltammetry were used to study the effect of a series of water-soluble amino acids and serum albumins on oxygen reduction in aqueous solutions. Positive or negative shifts of the reduction potential of oxygen were revealed, depending the nature of the compounds. The feasibility of polarographic methods for studying antioxidant properties of compounds was demonstrated.     

蛋白质二级结构的氨基酸紧邻位效应和二肽构象因子

提出了蛋白质二级结构中的氨基酸C端和N端邻位因子以及二肽构象因子. 基于对蛋白质数据库PDB105版全库的分析, 讨论了N端和C端邻位对氨基酸二级结构倾向性的影响, 讨论了二肽序的二级结构倾向性. 发现有些氨基酸的邻位因子对和二肽序对的二级结构构象因子差别较大, 表明这些氨基酸对其N端和C端邻位的影响不对称.     

Photocatalytic Modification of Amino Acids,Peptides, and Proteins

In the last decade, visible-light photoredox catalysis has emerged as a powerful strategy to enable novel transformations in organic synthesis. Owing to mild reaction conditions (i.e., room temperature, use of visible light) and high functional-group tolerance, photoredox catalysis could represent an ideal strategy for chemoselective biomolecule modification. Indeed, a recent trend in photoredox catalysis is its application to the development of novel methodologies for amino acid modification. Herein, an up-to-date overview of photocatalytic methodologies for the modification of single amino acids, peptides, and proteins is provided. The advantages offered by photoredox catalysis and its suitability in the development of novel biocompatible methodologies are described. In addition, a brief consideration of the current limitations of photocatalytic approaches, as well as future challenges to be addressed, are discussed.     

氨基酸缓蚀剂在盐酸溶液中对钢的缓蚀作用

应用极化曲线、电化学阻抗谱等测试技术,研究了以谷氨酸作缓蚀剂在10%盐酸介质中对X65钢的缓蚀作用,测试腐蚀参数包括腐蚀电位(Ecorr)、极化电阻(Rp)、缓蚀效率(η)等.研究表明:该缓蚀剂是一种抑制阴极为主的混合型缓蚀剂,在较低的浓度具有良好缓蚀效果;缓蚀效率随着浓度的增加而提高,并在0.3g.L-1时达到最大值(90%以上).     

The Effect of Column and Eluent Fluorination on the Retention and Separation of non-Fluorinated Amino Acids and Proteins by HPLC

The effect of column and eluent fluorination on the retention and separation of non-fluorinated amino acids and proteins in HPLC is investigated. A side-by-side comparison of fluorocarbon column and eluents (F-column and F-eluents) with their hydrocarbon counterparts (H-column and H-eluents) in the separation of a group of 33 analytes, including 30 amino acids and 3 proteins, is conducted. The H-column and the F-column contain the n-C₈H₁₇ group and n-C₈F₁₇ group, respectively, in their stationary phases. The H-eluents include ethanol (EtOH) and isopropanol (ISP) while the F-eluents include trifluoroethanol (TFE) and hexafluorosopropanol (HFIP). The 2 columns and 4 eluents generated 8 (column, eluent) pairs that produce 264 retention time data points for the 33 analytes. A statistical analysis of the retention time data reveals that although the H-column is better than the F-column in analyte separation and H-eluents are better than F-eluents in analyte retention, the more critical factor is the proper pairing of column with eluent. Among the conditions explored in this project, optimal retention and separation is achieved when the fluorocarbon column is paired with ethanol, even though TFE is the most polar one among the 4 eluents. This result shows fluorocarbon columns have much potential in chromatographic analysis and separation of non-fluorinated amino acids and proteins.     

氨基酸与蛋白质体系热容研究

氨基酸与蛋白质都是生命现象和分子生物学研究的最基本和最重要的研究对象.利用热力学方法,特别是从热容的角度出发对其研究,对深入了解蛋白质的折叠与伸展、变性机理、稳定性及生命体的新陈代谢等问题均具有一定的意义.近年来,研究者们对蛋白质或氨基酸体系的热容研究做了大量工作,取得了很大进展,本文对此进行了概述。     

A New Strategy for the Destabilization of Double-Stranded Nucleic Acids by Phenylalkylamine Derivatives

Drastic reduction in the melting points indicates considerable destabilization of double-stranded (ds) nucleic acids by stabilization of unfolded polymer parts with phenylalkylamine derivatives. These ligands cannot intercalate into ds duplex forms, but can stack with unfolded parts if the spacers separating the phenyl rings have the appropriate length.     

Induction of Asymmetry by Amino Acids

Since the stereoisomers of molecules with one or more asymmetric centers often exhibit different biological activities (e.g. thalidomide, pheromones), stereoselective synthesis as a method of preparative chemistry is rapidly attaining importance. Of the numerous drugs prepared by total synthesis that contain at least one asymmetric center, only about 20% have so far been used in sterically pure form. Amino acids constitute the greatest “chiral pool” of compounds whose enantiomers can be obtained commercially in large amounts; they are gradually being used more and more frequently as auxiliary agents or educts in asymmetric syntheses.     

蛋白质功能化新策略:嵌入非天然氨基酸

天然蛋白质由20种天然氨基酸组成,这些蛋白质的构筑基元包含功能基团:羧基、氨基、巯基、硫醚、羟基、碱性胺、烷基和芳基。然而,这些有限的功能基团却不足以完成生物体内所有的生物学功能。为了更好地让生命的体现者--蛋白质完成更加精确和多样的生物学功能,自然界会对蛋白质进行翻译后的修饰,包括:磷酸化,甲基化,乙酰化或者羟基化,甚至在某些情况下,进化出一种新型的翻译机制以便插入硒代半胱氨酸或者吡咯霉素。受此启发,生物化学家发展出各种生物或化学方法来改变或插入新的蛋白质构筑基元,使天然蛋白质完成其相应的生物学功能或者使其具有某些特殊的性质,甚至是创造一种新酶。该文将简单介绍这些蛋白质修饰策略以及该领域的最新进展。     

氨基酸改性聚乳酸

为了改善聚乳酸降解速度慢、细胞亲和性差等方面的不足,氨基酸对聚乳酸的改性工作正在得到人们越来越多的关注.本文综述了氨基酸对聚乳酸改性的各种方法,以及各种氨基酸改性聚乳酸材料的性能与应用.其中,较为常见的改性方法是合成聚(乳酸-氨基酸).展望氨基酸改性聚乳酸类生物降解材料的未来,降低合成成本是广泛应用的关键.因此,虽然目前广泛应用的聚(乳酸-氨基酸)合成途径是氨基酸环状衍生物(尤其是吗啉-2,5-二酮)开环聚合法,但经济有效地以氨基酸、乳酸等为原料的直接聚合法值得关注.     

Recent Advances in Photoinduced Modification of Amino Acids,Peptides, and Proteins

The chemical modification of biopolymers like peptides and proteins is a key technology to access vaccines and pharmaceuticals. Similarly, the tunable derivatization of individual amino acids is important as they are key building blocks of biomolecules, bioactive natural products, synthetic polymers, and innovative materials. The high diversity of functional groups present in amino acid-based molecules represents a significant challenge for their selective derivatization Recently, visible light-mediated transformations have emerged as a powerful strategy for achieving chemoselective biomolecule modification. This technique offers numerous advantages over other methods, including a higher selectivity, mild reaction conditions and high functional-group tolerance. This review provides an overview of the most recent methods covering the photoinduced modification for single amino acids and site-selective functionalization in peptides and proteins under mild and even biocompatible conditions. Future challenges and perspectives are discussed beyond the diverse types of photocatalytic transformations that are currently available.     

Analysis of Saccharides by the Addition of Amino Acids

In this work, we present the detection sensitivity improvement of electrospray ionization (ESI) mass spectrometry of neutral saccharides in a positive ion mode by the addition of various amino acids. Saccharides of a broad molecular weight range were chosen as the model compounds in the present study. Saccharides provide strong noncovalent interactions with amino acids, and the complex formation enhances the signal intensity and simplifies the mass spectra of saccharides. Polysaccharides provide a polymer-like ESI spectrum with a basic subunit difference between multiply charged chains. The protonated spectra of saccharides are not well identified because of different charge state distributions produced by the same molecules. Depending on the solvent used and other ions or molecules present in the solution, noncovalent interactions with saccharides may occur. These interactions are affected by the addition of amino acids. Amino acids with polar side groups show a strong tendency to interact with saccharides. In particular, serine shows a high tendency to interact with saccharides and significantly improves the detection sensitivity of saccharide compounds.

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Na和Cl对CDI活化的酸性及碱性氨基酸聚合反应的高效促进效应

含有Na⁺（K⁺）及Cl^-等无机离子的水溶液是所有生化反应的反应体系，因而也是地球上最重要的反应体系。目前科学界对这一体系中上述离子与离子之间、离子与水分子之间、离子与生物分子之间的弱相互作用的了解还非常有限，很多离子特异性现象的机理至今仍不清楚。结合我们近期发现在水溶液中Na⁺（K⁺）及Cl^-等简单离子对带相反电荷氨基酸成肽的高效促进效应，本文希望强调水溶液体系中Na⁺（K⁺）及Cl^-等简单离子与多肽及蛋白之间的弱静电相互作用对蛋白及多肽结构及功能的重要性。本文还讨论了水溶液中的这些弱静电相互作用在生命起源及生命现象中的意义。     

高效液相色谱法测定羊水中兴奋性氨基酸、抑制性氨基酸的含量

建立了反相高效液相色谱法测定羊水中兴奋性氨基酸天门冬氨酸、谷氨酸,抑制性氨基酸甘氨酸含量的方法,色谱柱为LUNAC18柱(4.6mm×250mm,5μm),流动相为乙腈水(V/V),按低压梯度洗脱,梯度系统0～4min,乙腈40%;4～20min,乙腈40%～52%;20～30min,乙腈52%～60%;30～40min,乙腈60%～40%。流速0.8mL/min,柱温40℃,紫外检测波长260nm;进样量10μL。结果显示,天门冬氨酸、谷氨酸和甘氨酸三者的线性范围均为2.5～85mg/L;标准加入的回收率为99.6%～102.6%。本方法灵敏度高、测定结果可靠。用本方法对201例不同孕期的羊水作兴奋性和抑制性氨基酸检测,发现羊水中3种氨基酸随妊娠进展而增加的趋势,胎儿畸形或宫内缺氧时羊水中这3种氨基酸水平明显升高。     

手性氨基酸的毛细管电泳拆分研究

以咔唑-9-乙基氯甲酸酯（CEOC）作柱前荧光衍生试剂,在毛细管区带电泳和胶束电动色谱条件下,以不同配比的β-环糊精（β-CD）和脱氧胆酸钠（SDC）作手性选择剂,在两种不同分离模式下,对氨基酸衍生物进行了手性分离,同时对分离过程中的相关参数进行了优化,分别实现了8种和10种氨基酸的快速手性分离。     

一些土壤和有机肥中氨基酸测定方法研究

一些土壤和有机肥中氨基酸测定方法研究袁吕江，熊凤麒，王正银（西南农业大学中心实验室重庆６３０７１６）（西南农业大学土化系重庆６３０７１６）关键词液相色谱法，氨基酸，土壤，有机肥１前言我国耕作土含氮量为０．４～３．８ｇ／ｋｇ［１］，其中９０％～９８％为...