毛细管电泳法测定苷肽胶囊中3种核苷酸

提出了毛细管电泳法同时分离测定苷肽胶囊中3种核苷酸腺嘌呤-5′-单磷酸、胞嘧啶-5′-单磷酸和鸟嘌呤-5′-单磷酸含量的方法。以15 mmol.L-1硼砂+35 mmol.L-1碳酸钠+60 mmol.L-1羟丙基-β-环糊精混合溶液为电解质溶液,运行电压30 kV,于254 nm波长处进行紫外检测。3种核苷酸的线性范围依次为5.0～80.0,8.0～80.0,8.0～80.0 mg.L-1,检出限(3S/N)依次为2.0,3.0,3.0 mg.L-1。采用该方法对苷肽胶囊样品中3种核苷酸的含量分别进行了测定,所得加标回收率在92.1%～102.7%之间,相对标准偏差(n=5)均小于等于5.0%。     

核酸化学研究--Ⅰ.结晶的5′-O-三苯甲基和5′-O-单对甲氧三苯甲基核糖核苷-3′-磷酸盐

本文报导了采用单对甲氧三苯甲基氯或三苯甲基氯与3′-单核糖核苷酸直接反应的方法,合成的产物通过适当的溶剂处理获得了结晶的5′-O-单对甲氧三苯甲基保护的3′-胞核糖核苷酸、3′-尿核糖核苷酸、3′-腺核糖核苷酸以及5′-O-三苯甲基保护的 N-乙酰基-3′-鸟核糖核苷酸等化合物,既简化步骤、缩短时间,又提高了产物的纯度和得率.     

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。     

稀土元素对3′-腺嘌呤及3′-鸟嘌呤核苷酸的水解断裂作用

用核磁共振(NMR)波谱、HPLC和化学定磷法研究了稀土元素对3′-腺嘌呤核苷酸(3′-AMP)及3′-鸟嘌呤核苷酸(3′-GMP)的水解断裂作用,结果表明:不同稀土元素对3′位核苷酸断裂有较强的特异性,在37℃,pH 9的条件下,使3′-AMP断裂为腺嘌岭核苷(A)及无机磷,使3′-GMP断裂为鸟嘌呤核苷(G)及无机磷,其断裂作用远大于5'位核苷酸,并对其水解断裂进行了研究.     

4,4′-二氨基二苯胺的合成

探索了以苯胺和对硝基氯苯为原料合成4,4′-二氨基二苯胺(3)的最佳反应条件,重要中间体和目标产物经元素分析和IR表征.3是合成苯胺低聚体或共聚物的最基本原料.     

低聚乳酸的制备及其对家禽的脱毛性能

以D,L-乳酸(2)为原料,丙三醇(1)固定羧基制得低聚乳酸(3),其结构经MS表征.最佳反应条件为:2141.5 mol,n(2)∶n(1)=30,于(150～160)℃/(0.5～3.0)kPa条件下反应20 h,收率93.0％.首次将3或其复配物4[m(3)∶m(碳酸钙)∶m(环氧大豆油)=100∶15∶3]应用于家禽脱毛,结果表明,3和4的脱毛效果良好.     

3,3′-(1,1′-二苯基-4,4′-二基)-二丙烯酸的合成新方法

通过Heck反应,以4,4′-二碘联苯和丙烯酸为原料,壳聚糖负载钯为催化剂,合成了3,3′-(1,1′-二苯基-4,4′-二基)-二丙烯酸.考察了反应温度、时间、原料配比等因素对产率的影响.结果表明最佳反应条件为:反应温度为100℃,时间为20h,原料配比为1∶3.测试了壳聚糖负载钯催化剂的重复使用性能,并用IR、1 H NMR和MS对产物进行了表征.     

4′-(二茂铁基)-2,2′∶6′,2″-三联吡啶钴(Ⅱ)配合物混合价态的电荷转移

设计合成了4′-(二茂铁基)-2,2′∶6′,2″-三联吡啶钴(Ⅱ)配合物1以及参比配合物4′-(4-甲苯基)-2,2′∶6′,2″-三联吡啶钴(Ⅱ)配合物2和2,2′∶6′,2″-三联吡啶钴(Ⅱ)配合物3,配合物1中二茂铁基给电子基团的引入使其在可见光区的吸收明显增强,并在部分氧化时呈现混合价态的电荷转移(MVCT)吸收.     

家蚕和苜蓿银纹夜蛾核型多角体病毒P10基因的研究

从AcMNPV基因组DNA中克隆筛选得到含P10基因的EcoR I-P片段,以此作为探针克隆得到BmNPV P10基因片段,测定了其全核苷酸序列。PCR点突变BmNPV P10基因启始密码子ATG区,ATG突变的同时形成一个Bgl Ⅱ酶切位点,突变后的启动子及其5′端作为5′端交换臂和AcMNPV的P10基因3′端作为3′端交换臂构建成一个非融合通用转移载体pBmAcPV1.该载体可以在Sf细胞中和野生型AcMNPV DNA共转染重组表达外源基因,也可以在Bm细胞中和野生型BmNPV DNA重组表达外源基因。CAT基因在BmNPV P10 ATG突变后的启动子的控制下在家蚕细胞中得到高效表达     

2′-5′寡腺苷酸的有机合成与修饰

本文主要综述了三方面的内容:(1)2′-5′寡腺苷酸的生物学意义。(2)2′-5′寡腺苷酸的有机合成,特别是磷酸三酯法和铅离子(Pb~(++))催化法。(3)2′-5′寡腺苷酸结构与功能的关系,如5′端磷酸基,3′端羟基以及碱基与功能的关系。     

Dynamics and thermodynamics of dimerization of parallel G-quadruplexed DNA formed from d(TTAGn) (n=3-5)

Parallel G-quadruplexes formed from oligonucleotide sequences, d(TTAGn), where n = 3-5, have been shown to form a dimer through end-to-end stacking of 3'-terminal G-tetrads. The monomers and dimers of the G-quadruplexes are in dynamic equilibrium with an exchange rate of approximately 1 s-1. A thermodynamic study demonstrated that the dimerization of the G-quadruplexes is largely enthalpic in origin.     

Selective phosphate protection: a novel synthesis of double-labeled oligonucleotides

[structure: see text] A novel, selective labeling of oligonucleotides with two different reporter groups is described. The oligonucleotide is synthesized using a stable 2-(4-methoxybenzamido)ethyl protection for a selected internucleosidic thiophosphate (PS) and a labile 2-(N-isopropyl-4-methoxybenzamido)ethyl for the 3'-terminal PS and internucleosidic phosphates. The latter group and the base protection are removed, and the 3'-terminal PS is labeled. The former protection is then cleaved by a prolonged ammonolysis, and the second reporter is introduced at the internucleosidic PS.     

α:β Selectivity in the synthesis of 3-substituted, 4-methyl umbelliferone glycosides of N-acetyl glucosamine and chitobiose

The influence of phenolic acceptor nucleophilicity; for example, 3-substituted, 4-methylumbelliferones, and glycosyl donor electrophilicity; for example, 3- and 4-substituted N-acetylglucosamines, on glycosylation stereochemistry has been evaluated. In a systematic comparison, the stereochemical outcome as well as the reaction yield appeared to be influenced by the 3- and 4-substituents of the donor as well as the 3-substituent of the aryl acceptor. In the context of synthesizing a fluorogenic substrate for oligosaccharyltransferase, an α-glycoside was desired. Although most acceptor–donor pairs led to predominantly or exclusively the β-glycoside, reaction of the most activated (3,4-di-O-benzyl) donor and the least nucleophilic acceptor (3-Br), resulted in a 1:1 ratio of α,β arylglycosides.     

Theoretical study of the o-OH participation in catechol ester ammonolysis

The possible catalytic effect of the vicinal hydroxyl group during the ammonolysis of acetylcatechol has been studied by first principle calculations. A very efficient intramolecular catalysis was found to occur when the catechol ester o-OH group is deprotonated: the activation energy of the ammonolysis decreases by 24 kcal mol(-1) as compared to that of acetylphenol ammonolysis. Using this value, the o-oxyanion-catalysed intramolecular ammonolysis was estimated to be orders of magnitude faster than the ammonolysis of acetylphenol or nonionised acetylcatechol. The analogy with the aminolysis of peptidyl-tRNA that occurs during protein biosynthesis implies several orders of magnitude acceleration due to complete or partial deprotonation of its 3'-terminal adenosine 2'-OH providing a mechanistic possibility for general acid-base catalysis by the ribosome.     

Synthesis of the 3′-terminal nonadecanucleotide (58–76) of yeast alanine tRNA

Two new procedures for the 3′-phosphorylation of oligoribonucleotide have been worked out. By using donor with a 3′-terminal phosphate group, in low donor / acceptor ratio (1:1.1 to 1:2), nonadecanucleotide AUUCCGGACUCGUCCACCAp, which corresponds to the 3′-terminal nucleotide sequence 58–76 of yeast alanine tRNA, has been synthesized in good yields (87–90%)through ligation by T₄ RNA ligase of four component fragments: AUUC, CGGA, CUCGUCCA and CCAp.     

Molecular complexes of non-chelating polydentate Lewis bases with group 13 Lewis acids: crystal structure and computed energy of stepwise donor–acceptor bond formation

The crystal structures of five donor–acceptor (DA) complexes of 1:1 and 2:1 composition between E(C₆F₅)₃ (E = B, Al, Ga and In) and pyrazine (pyz) as a non-chelating bidentate nitrogen-containing donor, as well as the GaI₃ pyz GaI₃ complex have been established for the first time. A joint analysis of the experimental structural data and the results of computations at the M06-2X/def2-TZVP level of theory reveals that with an increase in the number of acceptor molecules in the DA complex, the DA bond distances increase, while the DA bond energies and Wiberg bond indexes decrease, indicating a weaker bonding. The previously reported ‘inverse’ relationship between the Lewis acidity and the capacity of a polydentate donor to complex with multiple Lewis acids is not confirmed.     

Synthesis of an mRNA fragment of alanyl-tRNA synthetase gene in Escherichia coli using the 6-methyl-3-pyridyl group for protection of the imide functions of uridine and guanosine

The synthesis of 5'-GpGpUpGpU-3' is reported to demonstrate the synthetic use of the 6-methyl-3-pyridyl group for the protection of the O-4 and O-6 imide functions of uridine and guanosine, respectively. The 2'- and 5'-hydroxyl functions of the key intermediates were protected with two acid-labile groups: 3-methoxy-1,5-dicarbomethoxypentane-3-yl (MDMP) and 9-(4-octadecyloxyphenyl)xanthen-9-yl (C18Px), respectively. The internucleotide phosphotriesters were protected with 2-chlorophenyl and the 9-fluorenylmethyl group was employed for 3'-terminal phosphate protection.     

Donor effect on supramolecular structures of silver(I) perchlorate complexes of macrocycles with O2S2X (X=S, O and NH) donor sets

By virtue of simple one donor variations of O(2)S(2)X-donor macrocycles (L(1): X=S, L(2): X=O and L(3): X=NH) towards silver(I) perchlorates, four supramolecular complexes (1-3) with different topologies have been isolated; L(1) afforded solvent- and anion-free sandwich complex (1), otherwise L(2) and L(3) gave the dimeric (2a), 1-D polymeric (2b), and tetrameric bowl-type (3) complexes with solvent or anion coordination.     

Coordination driven self-assembly of four new molecular boats using a flexible imidazole-containing donor linker

Using a metal-ligand coordination bonding approach, the self-assembly of four new metallamacrocycles from Pd(ii)-based 90 degrees acceptors and a diimidazole donor ligand 1,3-bis(imidazole-1-ylmethyl)-2,4,6-trimethylbenzene (L) has been achieved. The assemblies are characterized fully by NMR and electrospray ionization-mass spectroscopic (ESI-MS) analysis and in two cases the X-ray single-crystal structure analysis established the gross structures. The selective formation of a diimidazole-based linker (L) containing macrocycle [(en)Pd(micro-L)2Pd(en)]4+ from a 1 : 1 : 1 mixture of cis-Pd(en)(NO3)2, and 1,2-bis(4-pyridyl)ethane is also established. Measuring the binding constants established the stronger Pd- binding force compared to traditional Pd-N(pyridyl linker) interaction, which reveals the possibility of using imidazole donor ligands as potential linkers or even better ligands compared to the widely used pyridyl donor ligands in the construction of metal-based large supramolecular assemblies.     

Spectral properties of new N,N'-bis-alkyl-1,4,6,8-naphthalenediimide complexes

The photophysical properties of two N,N'-bis-alkyl-1,4,6,8-naphthalenediimide (DCN1 and DCN2) have been studied in chloroform and N,N-dimethylformamide solvents. The ability of DCN2 in N,N-dimethylformamide to detect metal cations have been monitored by the fluorescence emission spectroscopy. It has been shown that the fluorescent intensity is very sensitive to the concentration of Fe3+ cations. The reaction of iodine with N,N'-bis-alkyl-1,4,6,8-naphthalenediimide in chloroform solution have been investigated by spectrophotometric method. The results indicate the formation of two CT-complexes [(DCN1)I]+.I3- and [(DCN2)I]+.I3- at donor:acceptor molar ratio of 1:2. The [(DCN1)I]+.I3- shows the characteristic absorptions of I3- ion at 290 and 360 nm while the charge-transfer transition of [(DCN2)I]+.I3- occurs at 310 nm. Three characteristic bands at the far infrared region in each iodine complex are observed around 135, 105 and 85 cm-1 due to nuas (I-I), nus (I-I) and delta (I3-), respectively with C2v symmetry. The values of the complex formation constant, K, and the absorptivity, epsilon have been calculated.