以胸腺嘧啶核苷酸钙盐为材料的Oligo(dT)-纤维素的制备

分离生物体内的mRNA是深入研究遗传信息翻译过程的首要条件,因而为分离mRNA所特需的Oligo(dT)—纤维素在核酸研究中极为重要。目前,一般在制备这种纤维素时,都采用胸腺嘧啶核苷酸铵盐或钠盐。但这两种原料不易多得,而胸腺嘧啶核     

Structure of Poly (dT)·Poly (dA)·Poly (dT)

Abstract

The molecular structure of poly (dT)·poly (dA)·poly (dT) has been determined and refined using the continuous x-ray intensity data on layer lines in the diffraction pattern obtained from an oriented fiber of the DNA. The final R-value for the preferred structure is 0.29 significantly lower than that for plausible alternatives. The molecule forms a 12-fold right- handed triple-helix of pitch 38.4 Å and each base triplet is stabilized by a set of four Crick-Watson-Hoogsteen hydrogen bonds. The deoxyribose rings in all the three strands have C2′-endo conformations. The grooveless cylindrical shape of the triple-helix is consistent with the lack of lateral organization in the fiber.     

Structures for the polynucleotide complexes poly(dA) · poly(dT) and poly(dT) · poly(dA) · poly(dT)

X-ray diffraction analyses of fibers of polydeoxyadenylic acid · polydeoxythymidylic acid show that this molecule exists as a 10-fold double-helix with axial rise per nucleotide $\text{h = 3.24}\text{to}\text{3.29}\text{A}\text{?}$. The structure is very similar to B-DNA ($\text{h = 3.37}\text{A}\text{?}$) in having C3-exo furanose rings and base-pairs positioned centrally on the helix axis, but distinctive enough to have two packing modes, neither of which has been observed for B-DNA. Although the triple-stranded poly(dT) · poly(dA) · poly(dT) also has a large value of h(3.26 Å), each of the chains is a 12-fold helix of the A-genus with C3-endo furanose rings and bases displaced several Angstrom units from the helix axis.     

以CB—F83—Oligo（dT）—纤维素批量亲和层析分离poly（A）RNA

Poly(A)RNA分离是反向转录cDNA,构建cDNA文库以及进行差异杂交等的基础工作,也是改善RNA凝胶吸Ep和S_1核酸酶保护实验质量的基本措施。Poly(A)RNA的分离主要采用Oligo(dT)-纤维素柱亲和层析的方法。我们在非洲爪赡卵母细胞及早期胚胎Poly(A)RNA的分离过程中,先后使用了Poly(A)Quick Column(Stratagene产品)和 Oligo(dT)Cellulose,Type 7(pharmacia产品)柱亲和层析以及CB-F 83-Oligo(dT)-纤     

Interaction of 9-O-(ω-amino) alkyl ether berberine analogs with poly(dT)·poly(dA)*poly(dT) triplex and poly(dA)·poly(dT) duplex: a comparative study

Isoquinoline alkaloids and their analogs represent an important class of molecules for their broad range of clinical and pharmacological utility. These compounds are of current interest owing to their low toxicity and excellent chemo preventive properties. These alkaloids can play important role in stabilising the nucleic acid triple helices. The present study has focused on the interaction of five 9-O-(ω-amino) alkyl ether berberine analogs with the DNA triplex poly(dT)·poly(dA)*poly(dT) and the parent duplex poly(dA)·poly(dT) studied using various biophysical techniques. Scatchard analysis of the spectral data indicated that the analogs bind both to the duplex and triplex in a non-cooperative manner in contrast to the cooperative binding of berberine to the DNA triplex. Strong intercalative binding to the DNA triplex structure was revealed from ferrocyanide quenching, fluorescence polarization and viscosity results. Thermal melting studies demonstrated higher stabilization of the Hoogsteen base paired third strand of the DNA triplex compared to the Watson–Crick strand. Circular dichroism studies suggested a stronger perturbation of the DNA triplex conformation by the alkaloid analogs compared to the duplex. The binding was entropy-driven in each case and the entropy contribution to free energy increased as the length of the alkyl side chain increased. The analogs exhibited stronger binding affinity to the triple helical structure compared to the parent double helical structure.     

Melting Behavior and Stability of (dA)8·(dT)8 Double Helix

Abstract

Melting behavior and stability of double helix of octadeoxyribonucleotides, (dA)₈·(dT)₈, have been studied by a UV measurement and a calculation of nearest-neighbor model. The helix of (dA)₈·(dT)₈ exhibited the thermodynamic parameters similar to those of B-form DNA.     

微波辅助法制备细菌纤维素-纳米银(BC-AgNps)复合材料及其表征

以细菌纤维素(BC)为模板,不同质量浓度的AgNO₃(10、50和200 mg/L)为原料,采用微波辅助法制备细菌纤维素-纳米银(BC-AgNps)复合材料后,再对BC-AgNps进行表征,最后考察它的抑菌性能。经电感耦合等离子质谱检测,复合材料中银含量分别为1.11、2.15和4.86 mg/g;扫描电子显微镜结果显示,AgNps均匀分散在BC上,没有团聚现象发生;使用X线衍射仪及紫外可见光谱均可检测到明显的AgNps特征峰且没有杂峰生成,热稳定性没有发生明显改变。所制备的复合材料具备优良的抑菌性能,对大肠杆菌的抑制率在99%以上,对金黄色葡萄球菌的抑菌率分别为39.90%、95.74%和99.87%,抑菌率随反应体系AgNO₃浓度的增加而提高。     

对(艹孟)烷-3,8-二醇的合成与应用研究进展

对(艹孟)烷-3,8-二醇是一种具有生物活性的化合物,主要来源于柠檬桉精油,可直接用于香水、杀虫剂和药品等.通常采用化学和生物化学的方法合成对(艹孟)烷-3,8-二醇,以替代从柠檬桉叶油分离得到的天然产品.以香茅醛为原料通过Prins环缩合和水解,或者通过Solanum aviculare悬浮培养方式进行生物转化得到对(艹孟)烷-3,8-二醇;通过薄荷醇的氧化,或者以2-丁烯醛为原料与甲基锂、NaClO2等试剂经过较长步骤也可合成对(艹孟)烷-3,8-二醇.对(艹孟)烷-3,8-二醇可应用于制造驱虫剂、凉味剂、药物或者化妆品的添加剂以及海水防护涂料添加剂等.     

交联醇脱氢酶聚集体的制备及其在(R)-4-氯-3-羟基丁酸乙酯合成中的应用

基于基因组序列数据库挖掘新酶的技术,从白色念珠菌Candida albicans基因组中克隆了一条新型醇脱氢酶(CADH)基因,并在大肠杆菌Escherichia coli Rosetta(DE3)中表达。为克服游离酶稳定性差、不能重复使用的缺点,探索并优化了交联醇脱氢酶聚集体(CLEAs-CA)的制备条件。结果表明:重组CADH对底物四氯乙酰乙酸乙酯(COBE)的比活力为1.8 U/mg,产物(R)-4-氯-3-羟基丁酸乙酯((R)-CHBE)的对映体过量值大于99%。CLEAsCA沉淀剂选择为60%饱和度的(NH_4)_2SO_4,交联剂为10 mmol/L戊二醛。在固定化操作前,加入50 mmol/L异丙醇和0.1 mmol/L NAD~+对CADH催化活性位点、辅酶结合位点进行保护,CLEAs-CA的活力回收率提高了48.3%。将CLEAs-CA用于不对称合成(R)-CHBE,经过19次的重复使用,CLEAs-CA的活性仍保留有50%。     

铜(II)-酪氨酸螯合物合成与分析

研究了铜(II)-酪氨酸螯合物的合成方法,探讨了影响合成工艺的主要因素,确定了原料配比、pH值、温度、反应时间等最佳合成条件.采用X射线衍射光谱对螯合物进行了表征,结果表明铜(II)能与酪氨酸形成螯合物.     

铬(Ⅲ)-天冬氨酸螯合物合成与分析

研究了铬(Ⅲ)-天冬氨酸螯合物的合成方法,探讨了影响合成工艺的主要因素,确定了原料配比、pH值、最佳反应时间及温度,采用X射线衍射光谱对螯合物进行了表征,结果表明铬(Ⅲ)能与天冬氨酸形成螯合物。     

Charge Transport in Poly(dG)–Poly(dC) and Poly(dA)–Poly(dT) DNA Polymers

We investigate the charge transport in synthetic DNA polymers built up from single type of base pairs. In the context of a polaronlike model, for which an electronic tight-binding system and bond vibrations of the double helix are coupled, we present estimates for the electron-vibration coupling strengths utilizing a quantum-chemical procedure. Subsequent studies concerning the mobility of polaron solutions, representing the state of a localized charge in unison with its associated helix deformation, show that the system for poly(dG)–poly(dC) and poly(dA)–poly(dT) DNA polymers, respectively possess quantitatively distinct transport properties. While the former supports unidirectionally moving electron breathers attributed to highly efficient long-range conductivity, the breather mobility in the latter case is comparatively restrained, inhibiting charge transport. Our results are in agreement with recent experimental results demonstrating that poly(dG)–poly(dC) DNA molecules acts as a semiconducting nanowire and exhibit better conductance than poly(dA)–poly(dT) ones.     

盐酸4-(β-氨乙基)苯乙酸的合成

以苯乙晴为原料,经水解、氯甲基化、取代、还原四步反应制得盐酸4-(β-氨乙基)苯乙酸。并对文献方法进行了改进。     

神经介素U(neuromedin U)研究概况

神经介素 (ｎｅｕｒｏｍｅｄｉｎ)是一组平滑肌刺激性多肽 ,通常分成四类 :韩蛙皮素类、肛褶蛙肽类、神经紧张素类、神经介素Ｕ (ｎｅｒｕｏｍｅｄｉｎＵ ,ＮＭＵ) .在这组多肽中 ,神经介素Ｕ最后被发现 ,并因其子宫收缩活性而得名 .神经介素Ｕ是Ｍｉｎａｍｉｎｏ等在 1985年首次从猪脊髓中发现并分离提纯到的多肽 (包括ＮＭＵ 8和ＮＭＵ 2 5 ) ,随后又相继从大鼠、几内亚小猪、狗、家兔、鸡和澳大利亚树蛙等物种中分离得到 .ＮＭＵ产生于一个由 174个氨基酸组成的前体 .该前体包含一个疏水信号肽和几个二元蛋白酶加工位点 ,这些二元加工位…     

细菌纤维素的合成与调控进展

细菌纤维素是1种天然的高纯度生物多聚物,与木质纤维素相比,其生产和加工过程更为方便和环保,因此已成为1种极有潜力的生物材料。葡糖酸醋杆菌是目前已知的产纤维素能力最高的菌株。综述了葡糖酸醋杆菌的细菌纤维素合成和调控机制以及为提高产量所进行的基因工程手段和培养方法。     

生物素-亲和素系统及其应用(续一)

<正> 三、用生物素标记的的凝集素和 ABC定位组织切片中的糖基 用异常敏感、特异和简单的生物素标记的外凝集素和ABC技术可以定位组织中的糖基。发现在良性和恶性组织中花生受体的     

生物素-亲和素系统及其应用(续二)

<正> 八、生物素衍生物 (一)生物素化大分子 用于生物素化的生物大分子物质最常见的是抗体。由于抗体分子上的氨基基团极易被活化生物素即生物素酸-N-羟基丁二酰亚胺(BNHS)所酰化,从而可使一个抗体分子接上多个抗生物素蛋白分子起反应。通常选用抗抗体(第二抗体)接上生物素,以便使用于不同的抗原-抗体反应体系。     

β-二酮亚胺-铁(Ⅱ)羰基配合物的合成及其表征

β-二酮亚胺配体(ArN(R)CCH(R)NAr,R=CH_3,H,Ar=2,6-二异丙基苯胺,苯胺,2,6-二甲基苯胺等等)可与不同金属配位形成多种配合物,上述配合物因其特殊的反应性能引起了研究者的广泛关注。本文以环戊二烯氯代羰基铁与β-二酮亚胺配体(ArN (R)CCH(R)NAr,R=CH_3,Ar=2,6-二甲基苯胺)反应生成铁的金属配合物,并对其产物进行了IR,1HNMR表征。     

同聚DNA分子poly(dA)·poly(dT)主链的振动位移

基于同聚DNA分子poly(dA).poly(dT)的螺旋对称性,利用晶格动力学方法,计算了DNA分子poly(dA).poly(dT)主链振动的本征矢,探讨了振动位移矢量和线二色光谱的关系。结果表明,对应着磷酸双氧的反对称振动谱线可以用于直接确定磷酸根的取向,精度小于1°。其它谱线必须通过对分子的简正分析来帮助确定分子的结构。