酵母丙氨酸转移核糖核酸3′-半分子(36—76)的合成

本文报告用T_4RNA连接酶将相应于酵母丙氨酸转移核糖核酸(tRNA_y~(Ala))3′-半分子(36—76)的三个寡核昔酸大片段——10(36—45)(Ⅰ),12(46—57)(Ⅱ)和19p(58—76)(Ⅲ)——从3′-端向5′-端延伸逐个连接合成了这个tRNA的3′-半分子(36—76)。首先在供受体配比为1:1.5的情况下,采取三步连续反应,即19p(Ⅲ)的5′-磷酸化,然后与12(Ⅱ)的连接和连接反应产物的5′-磷酸化等反应,一次制备分离的方法,以70％的总得率合成了5′-磷酸化的三十一核苷酸(46—76)(Ⅳ)。然后,以(Ⅳ)作为下一步反应的供体和三倍量的10(Ⅰ)连接,以67％的产率合成了具有四十一核苷酸的tRNA_y~(Ala)的3′-半分子(36—76)(Ⅴ)。将这个合成的3′-半分子,5′-磷酸化以后,与天然的5′-半分子连接,人工半合成了tRNA_y~(Ala)整分子,经生物活力测定,这个人工半合成的tRNA_y~(Ala)具有接受[~3H]-丙氨酸、并能将接受的丙氨酸转移到蛋白质分子中去的生物活力。     

ASSAY OF BIOLOGICAL ACTIVITY OF SYNTHETIC YEAST ALANINE TRANSFER RNA (tRNA_y~(Ala))

The biological activity of the synthetic tRNA_y~(Ala) was studied with an extremely sensitive method, tRNA_y~(Ala). accepted alanine in the presence of rat liver aminoacyl-tRNA_y~(Ala)-synthetase (this was called the accepting actvity). The aminoacylated tRNA_y~(Ala) was conveniently precipitated by ethanol with good recovery. The efficiency of transferring alanine from the aminoacylated tRNA_y~(Ala) into the protein was determined in in vitro rabbit reticulocyte lysate cell-free protein-synthesizing system (this was called the incorporation activity). Both accepting and incorporation activities could be determined in one assay with only 5-7 pmoles of tRNA_y~(Ala) either in ligation mixture or in purified form.Our results show that the accepting activities of the synthetic products were 51.6-65.6% and 91.3-106.0% of that of natural and reconstituted natural tRNA_y~(Ala) respectively. The efficiency of the incorporation of alanine in the aminoacylated tRNA_y~(Ala) into the protein was 61.6-63.1%, corresp     

酵母丙氨酸转移核糖核酸的人工全合成

本文报道采用有机合成与酶促合成相结合的方法,按照R.Holley等测定又经他人修正的一级结构,人工全合成了酵母丙氨酸转移核糖核酸(tRNA_y~(Ala))的工作。我们合成的tRNA_y~(Ala)与天然的tRNA_y~(Ala)具有相同的化学组成(含有全部修饰核苷酸)和结构,并有完整的生物活力,即在大鼠肝氨酰基tRNA合成酶的催化下,能接受丙氨酸,而且在兔网织红细胞裂解液体系中能将所携带的丙氨酸参入到蛋白质中去。在进行全合成以前,曾分别进行了两种人工半合成,即将天然的5′半分子与人工的3′半分子和人工的5′半分子与天然的3′半分子进行连接,都取得有生物活力的整分子tRNA_y~(Ala)。据我们了解,这是世界上第一次用人工方法合成的具有生物功能的核糖核酸。     

腺嘌呤核苷的环磷酰化反应

腺嘌呤核苷3’,5’-环磷酸(c-AMP)的磷酸衍生物可能作为c-AMP在体内的模拟物或贮存形式,因此研究c-AMP磷酸衍生物的合成及其生物活性,有可能为发现新药开辟途径.作者曾报道c-AMP的磷酯和磷酰胺的合成,并发现这类衍生物对肿瘤细胞的DNA和RNA的合成有较强抑制作用.本文讨论了含有不同离去基团的三价磷试剂与2'-保护的核苷反应,可以直接环合生成各种核苷3’,5’-环亚磷酸衍生物,后者进一步与碘或硫反应可     

酵母丙氨酸转移核糖核酸5′-半分子(1—35)的合成

本文报道了应用T_4RNA连接酶将酵母丙氨酸转移核糖核酸(tRNA_y~(Ala))5′-半分子中的三个寡核苷酸片段[—13(Ⅰ);14—22(Ⅱ);23—35(Ⅲ)]连接成5′-半分子的工作。由于寡核苦酸片段的纯度高,多核苷酸激酶和T_4RNA连接酶的质量好,采用连续反应的方法,简化了分离步骤,使产物的得率大大提高,二十二核苷酸的连接率是75％,三十五核苦酸的连接率是90％,以第一步反应原料为基数计算,最终产物的总得率是21％。经连接点和末端核苷酸分析,证明它的结构是正确的。将合成的5′-半分子与天然的3′-半分子在T_4RNA连接酶的催化下连接成人工半合成的完整tRNA_y~(Ala),具有接受[~3H]-丙氨酸和将[~3H]-丙氨酸转移到蛋白质中的生物活力。     

人工合成的酵母丙氨酸转移核糖核酸的生物活力测定

本文报道了用一种高灵敏度的方法测定人工合成的酵母丙氨酸转移核糖核酸(tRNA_y~(Ala))的生物活力。tRNA_y~(Ala)在大鼠肝氨酰基tRNA合成酶的催化下接受丙氨酸后,用操作简便而回收率较高的酒精沉淀法回收氨酰化产物,最后,在兔网织红细胞裂解液无细胞蛋白合成体系中,测定氨酰化产物中的丙氨酸转移到蛋白质中去的能力——参入活力。这方法不仅可以测定分离纯化的tRNA_y~(Ala)的活力,而且也可以测定经T_4RNA连接酶连接两个半分子后的反应混合物中产物tRNA_y~(Ala)的活力。利用这方法,已成功地测定了微至5—7 pmoles的人工全合成tRNA_y~(Ala)的接受活力和参入活力两组数据。测定结果表明,全合成tRNA_y~(Ala)的接受活力是天然分子的51.6—65.6％,是经拆合的天然分子的91.3—106.0％。其氨酰化产物中的[~3H]-Ala在兔网织红细胞裂解液中的利用率为61.6—63.1％,是天然分子的90.6—91.7％,是经拆合的天然分子的97.2—115.8％。     

SYNTHESIS OF THE 3'-HALF MOLECULE OF YEAST ALANINE tRNA

This paper deals with the synthesis of the 3'-half molecule of yeast alanine transfer RNA (tRNA_y~(Ala)) by ligation with T_4 RNA ligase of three component oligonucleotide fragments corresponding to nucleotides 36-45(Ⅰ), 46-57(Ⅱ) and 58-76(Ⅲ) in succession extending from the 3'-end to the 5'-end. First, in a ratio of acceptor to donor at 1.5 to 1, we adopted a method of three successive reactions, namely, the 5'-phosphorylation of the nonadecamer (Ⅲ), ligation with the dodecamer(Ⅱ) and the 5'-phosphorylation of the ligation product formed; with one isolation step and obtained the 5'-phosphorylated 31mer(46-76) (Ⅳ) in an overall yield of 70%. Then the 31met(Ⅵ) as a donor was ligated with 3 times of decamer(Ⅰ) to form the 41met(36-76) (Ⅴ), the 3'-half molecule of tRNA_y~(Ala)). The yield was 67%. After 5'-phosphorylation, (Ⅴ) was ligated with the natural 5'-half molecule to form the semi-synthetic tRNA_y~(Ala)), which was biologically active, i. e. accepting and transferring (~3H)-alanine into p     

修饰核苷酸的生物功能——Ⅱ.酵母tRNA~(Ala)类似物(A_(34)或G_(34)代替I_(34))的合成及生物活性

酵母tRNA~(Ala)的5′-半分子类似物(A_(34)或G_(34)代替I_(34))与3′-半分子在T_4 RNA连接酶催化下连接成酵母tRNA~(Ala)类似物(A_(34)或G_(34)代替I_(34))的整分子。合成的酵母tRNA~(Ala)类似物,在凝胶电泳上具有与天然酵母tRNA~(Ala)相同长度位置,其纯度为95％左右,连接点、末端分析都是对的。测定了这类似物的生物活力,即在大鼠肝氨酰基tRNA合成酶的催化下,接受丙氨酸的能力与天然重组的酵母tRNA~(Ala)没有明显变化,而在兔网织细胞裂解液体系中能将所携带的丙氨酸参入到蛋白质中去的能力,A_(34)代替I_(34)的只有天然或天然重组酵母tRNA~(Ala)的1/3,而G_(34)代替I_(34)的为90％左右。着重讨论了A或G代替I_(34)后,参入活力变化不同的原因。     

5-卤代-2’-脱氧-2’-β-氟-4’-叠氮嘧啶核苷的合成与抗乙肝病毒活性研究

以(间氯)苯甲酰基保护的2’-脱氧-2’-β-氟-4’-叠氮尿苷为起始原料,经过硝酸铈铵(CAN)介导的卤代、三氮唑活化、胺化、脱保护合成了一系列5-卤代的2’-脱氧-2’-β-氟-4’-叠氮嘧啶核苷类化合物.体外生物活性评价研究表明, 5-氯代(6a)和5-碘代(6c)核苷衍生物具有很好的抗乙肝病毒活性,而且细胞毒性较小.     

核苷5'-硫代磷酰氨基酸酯电喷雾质谱研究

核苷磷酰氨基酸酯化合物是1类倍受重视的药物,特别是它可作为寡聚核苷酸的类似物用于反义药物[1].核苷逆转录酶抑制剂被批准用于治疗爱滋病(AIDS),目前普遍使用的抗HIV核苷类似物中,2',3'-双脱氧核苷(ddNs)具有良好的疗效[2],它的抗病毒的可能机理是在细胞激酶的作用下,5'-羟基发生相继的磷酸化生成三磷酸核苷,然后通过HIV-逆转录酶进入病毒DNA的合成,由于ddNs 3'-位没有相应的羟基存在,使得病毒DNA的合成得以终止.     

聚乳酸-聚乙二醇-聚乳酸三嵌段共聚物的降解性能

以辛酸亚锡为引发剂,聚乙二醇大分子为共引发剂进行现交酯开环聚合,制备了系列聚乳酸（PLA）－聚乙二醇（PEG）－聚乳酸（PLA）三嵌段共聚物。从共聚物在生理盐水 中降解时特性粘度[η],质量和热行为的变化,考察了PEG分子量和丙交酯／PEG（摩尔比）对共聚物降解行为的影响,结果表明,PEG嵌段对共聚物的降解速率有重要影响,丙交酯／PEG一定时,PEG分子量越大,共聚物越容易降解,PEG嵌段长度一定时,丙交酯／PEG越大,共聚物降解速率越小。     

Thermodynamics of G-3(D4) and G-6(D4) carbosilanecyclosiloxane dendrimers

Temperature dependences of the heat capacity of G-3(D₄) and G-6(D₄) carbosilanecyclosiloxane dendrimers are studied for the first time by precision adiabatic vacuum and differential scanning calorimetry in the range of 6 to 350–450 K. Physical transformations in the investigated temperature range are observed and their standard thermodynamic characteristics are determined and discussed. Standard thermodynamic functions for a mole unit are calculated from the experimental data: C _p ^○ (T), H ^○(T), ? H ^○(0), S ^○(T) ? S ^○(0), and G ^○(T) ? H ^○(0) in the range of T → 0 to (350–449) K and standard entropies of formation at 298.15 K. Low-temperature (T ≤ 50 K) heat capacity is analyzed using the Debye theory of heat capacity of solids and the multifractal model. The values of fractal dimensionality D are determined and some conclusions on the topology of the investigated structures are drawn. The corresponding thermodynamic properties of the investigated carbosilanecyclosiloxane dendrimers under study are compared.     

二维(2D)沸石与三维(3D)沸石的制备及催化研究进展

如今在能源紧缺和“双碳”背景下, 能源清洁高效利用显得异常重要. 沸石催化剂是在能源加工过程中提高产出和品质的重要手段, 现已成为该领域的研究热点. 随着对沸石研究的进一步深入, 它们的性质和结构逐渐清晰, 广泛应用于催化、吸附、分离等行业. 独特晶体结构的二维沸石, 它们的片层结构在降低分子传输路径的同时, 可增大活性位点的可及性, 降低了积碳率, 具有较大应用潜力. 此外, 通过改变结构导向剂的结构可以拓宽二维沸石的种类, 符合工业上适应范围广的特点. 在此, 综述了两种维度分子筛的发展过程, 阐明了它们在不同领域中催化转化的构-效关系, 以及二维沸石的制备路径. 整理了合成机理并分析了二维沸石在比表面积和活性位点可及性上的优势, 为二维沸石分子筛在工业中的应用提供借鉴.     

Polyfunctional Two- (2D) and Three- (3D) Dimensional Oxalate Bridged Bimetallic Magnets

Summary.  We report major results concerning polyfunctional two- (2D) and three- (3D) dimensional oxalate bridged bimetallic magnets. As a consequence of their specific organisation they are composed of an anionic sub-lattice and a cationic counter-part. These bimetallic polymers can accommodate various counter-cations possessing specific physical properties in addition to the magnetic ones resulting from the interactions between the metallic ions in the anionic sub-lattice. Thus, molecular magnets possessing paramagnetic, conductive and optical properties are presented in this review. Corresponding author. E-mail: train@ccr.jussieu.fr Received April 11, 2002; accepted May 27, 2002     

A simple route to novel D spherosilicones; the first crystallographic structures of D(6) and D(8) cages

The synthesis, characterisation and crystal structure of D(8) and D(6) cages from the corresponding bis(dialkoxy)methane is reported.     

Preparation and Characterization of Poly(D,L-Lactide) (PLA) and Poly(D,L-Lactide)-Poly(Ethylene Glycol) (PLA-PEG) Nanocapsules Containing Antitumoral Agent Methotrexate

Summary: The aims of the present work were to prepare and characterize nanocapsules containing antitumoral agent methotrexate (MTX) from poly(D ,L -lactide) (PLA) and poly(D ,L -lactide)-poly(ethylene glycol) diblock copolymer (PLA-PEG) with the purpose of administrating this drug by topical ocular route for primary ocular lymphoma treatment. Nanocapsules were prepared by the interfacial deposition of preformed polymer. The influences of the initial amount of MTX on the encapsulation efficiency, drug recovery and drug content, as well as the physicochemical properties of the particles were evaluated. The particle mean diameters were 246 and 146 nm, and zeta potential values were −38.8 and −33.6 mV, for the MTX-loaded nanocapsules prepared from PLA and PLA-PEG, respectively. The methotrexate content in the particles increased with the increasing in the drug amount added to the formulations, but the drug recovery decreased significantly. After 4 h of in vitro release, 28 and 86% of MTX was released from PLA and PLA-PEG nanocapsules, respectively.     

Absolute configuration of D(2)-symmetric fullerene C(84)

The D(2)-symmetric isomer of fullerene C(84) predominantly found in soots is inherently chiral. We determine its absolute configuration by comparison of the experimental electronic circular dichroism (CD) spectrum with time-dependent density functional calculations.     

二维相关振动光谱技术

从发展历史、计算方程、性质规则等方面系统地介绍了近年来发展起来的二维相关光谱技术.结合各种常见的一维振动光谱, 如红外、拉曼、荧光、近红外-红外等光谱举例阐述了二维振动光谱的优势及其普适性.介绍了在广义二维相关光谱理论上最新延伸发展起来的二维样品-样品相关技术和二维杂化相关技术的基本理论, 并将之与传统的二维变量-变量相关技术(广义二维相关光谱)进行了比较.