桂皮酸-镧(Ⅲ)配合物与鲱鱼精DNA的相互作用

制备了桂皮酸-镧(III)配合物,通过紫外-可见光谱法研究了桂皮酸与La(III)的相互作用,发现La(III)与桂皮酸可形成1∶2的配合物,该配合物的摩尔吸光系数ε=4.9×106L/(mol·cm)。此外,采用紫外吸收光谱、荧光光谱和粘度法,研究了配合物与鲱鱼精DNA之间的相互作用。结果显示配合物与DNA作用的结合常数K=4.47×103L/mol,DNA与配合物的作用摩尔比为1∶3,作用模式为插入作用。     

顺式铂自旋标记配合物对人红细胞膜通透特性的研究

合成了顺式铂自肇标记配合物,实现了用电子顺磁共振方法直接研究药物通诱人红细胞膜的特性。结果表明：２０μｍｏｌ／Ｌ的铂自旋标记配合物通透的半寿命为数分钟。不同的配合结构表现不同的通道特性,提示可能存在药物小分子与膜分子之间的静电相互作用及配位相互作用,从脂质体ＤＰＰＣ相变特性的研究可知：铂自旋标记配合物比之母体配合物,使ＤＰＰＣ相变温度升高更多,从而影响跨膜通透的速率,因此有助于降低药物毒性。     

桂皮酸-8-羟基喹啉稀土配合物的合成、抑菌活性及其对DNA的作用

以稀土离子为模板,用桂皮酸、8-羟基喹啉为原料,在乙醇溶液中首次合成了两种稀土三元配合物,采用元素分析、摩尔电导、红外光谱、紫外光谱和荧光光谱进行表征,并研究了配合物对常见细菌大肠杆菌和金黄色葡萄球菌的抑菌活性以及与DNA的相互作用.结果表明:配合物的抑菌活性较配体和稀土离子均有提高,能使细胞正常的DNA复制生理功能受到影响.     

膜上相互作用对平板双分子层脂膜电性质的影响

以平板双分子层脂膜作为生物膜的简单模型,建立用平板双分子层脂膜电性质研究药物－生物膜相互作用的方法。研究以具有典型特征的物质－表面活性剂、自由基、金属手性配合物与平板膜的相互作用引起膜电性质的规律性改变;重组人Ｂ型血红细胞膜与溶液中抗Ｂ单克隆抗体发生特异相互作用时,膜电阻快速下降,下降的速率与加入的抗体量成正相关。在研究发生在平板膜上的典型反应的基础上,通过对膜电性质的监测和分析,从而确认平板双分     

生物无机化学在生活中的应用——金属蛋白质和金属酶

生物无机化学是研究生命体系中金属离子及其配合物存在状态和功能的科学,是配位化学和生命科学交叉的前沿学科。金属离子在生命体系中主要是通过金属离子与体内的酶、蛋白或核酸的相互作用以及存在体内的金属蛋白、金属酶行使其功能,因此通过现代物理方法来研究它们的结构、构象以及结构与功能的关系十分重要。     

壳聚糖Fe（Ⅲ）配合物的合成、表征及抑菌性能

合成了壳聚糖Fe(Ⅲ)配合物,利用IR、UV、和TG-DTA对配合物进行了表征.研究了壳聚糖及壳聚糖铁(Ⅲ)配合物对常见的两种细菌(大肠杆菌、金黄色葡萄球菌)的抑菌性能.结果表明:水溶性的壳聚糖在配合前后,其结构表征发生了一定的变化,并且壳聚糖铁(Ⅲ)配合物的抑菌性能比水溶性壳聚糖本身显著提高(P＜0.05).     

水飞蓟宾微量元素配合物的合成及其抗菌抗肿瘤活性研究

合成水飞蓟宾钙、铁、锌、硒、铬、钴配合物6个中药新药,采用IR、UV、Lc-MS、EDTA络合滴定和元素分析仪表征配合物化学结构,结果显示合成的配合物配位比为2∶1(水飞蓟宾∶微量元素),且小鼠急性毒性实验显示6个配合物均无明显毒性。采用倍比稀释法测定配合物对枯草杆菌等9种致病菌的抑制活性,发现其最小抑菌浓度MIC均低于水飞蓟宾,抗菌活性提升至2～4倍;采用MTT法测定配合物对5株肿瘤细胞增殖的影响,发现其半数抑制浓度IC_(50)均小于水飞蓟宾,抗肿瘤活性提升至1.11～1.53倍。综上,水飞蓟宾与微量元素形成配合物后,其抗菌及抗肿瘤活性均增强。     

若干铜配合物歧化超氧离子的活性

合成了若干含氮的铜配合物,用核黄素-蛋氨酸-光照法测定其歧化超氧离子的活性,与超氧化物歧化酶作了对照,发现双核的铜配合物比单核的铜配合物有较高的活性,铜的双核咪唑桥配合物的活性高于结构相近的单核配合物。     

DL─蛋氨酸的希夫碱的铜（Ⅱ）、锌（Ⅱ）配合物的抑菌作用

合成ＤＬ─蛋氨酸与邻香草醛缩合成铜（Ⅱ）、锌（Ⅱ）配合物,经化学分析、电子、红外光谱、热分析测定,对配合物进行了组成和结构分析。测定了配合物对金黄色葡萄球菌、大肠杆菌和枯草杆菌的抑制作用。     

Co2+-Tyr配合物的合成及X射线衍射分析

研究了Co2+-Tyr配合物的合成方法,探讨了合成工艺的主要影响因素,确定了最佳反应时间、温度、pH值及原料配比,采用X射线衍射光谱及元素分析对配合物结构进行了分析鉴定,结果表明Co2+能与Tyr形成配合物。     

Chirality as a tool in nucleic acid recognition: principles and relevance in biotechnology and in medicinal chemistry

The understanding of the interaction of chiral species with DNA or RNA is very important for the development of new tools in biology and of new drugs. Several cases in which chirality is a crucial point in determining the DNA binding mode are reviewed and discussed, with the aim of illustrating how chirality can be considered as a tool for improving the understanding of mechanisms and the effectiveness of nucleic acid recognition. The review is divided into two parts: the former describes examples of chiral species interacting with DNA: intercalators, metal complexes, and groove binders; the latter part is dedicated to chirality in DNA analogs, with discussion of phosphate stereochemistry and chirality of ribose substitutes, in particular of peptide nucleic acids (PNAs) for which a number of works have been published recently dealing with the effect of chirality in DNA recognition. The discussion is intended to show how enantiomeric recognition originates at the molecular level, by exploiting the enormous progresses recently achieved in the field of structural characterization of complexes formed by nucleic acid with their ligands by crystallographic and spectroscopic methods. Examples of application of the DNA binding molecules described and the role of chirality in DNA recognition relevant for biotechnology or medicinal chemistry are reported.     

Type IIE and IIF restriction endonucleases interacting with two recognition sites in DNA

Recently, it was revealed that restriction endonucleases widely used in genetic engineering and molecular biology are diverse not only in DNA sequence specificities but also in mechanisms of their interaction with DNA. In the review type IIE and IIF restriction endonucleases which require the simultaneous interaction with two copies of their recognition sequence for effective hydrolysis of DNA are considered. Crystal structures of these enzymes and their complexes with DNA as well as stepwise interaction with DNA, mechanisms of catalysis and enzyme-mediated DNA looping are discussed. A novel type of DNA-protein recognition was found for type IIE endonucleases when two copies of the same DNA sequence specifically interact with two different amino acid sequences and two structural motifs located in one polypeptide chain.     

Transformation in pneumococcus: nuclease resistance of deoxyribonucleic acid in the eclipse complex.

Donor deoxyribonucleic acid strands in the eclipse phase of genetic transformation of pnuemococcus (Streptococcus pneumoniae) are purified as a complex with a cf the deoxyribonucleic acid strand in this complex to digestion by nucleases was shown to be 50- to 1,000-fold less than that of uncomplexed single strands of deoxyribonucleic acid. Deoxyribonuclease I, micrococcal nuclease, Neurospora endonuclease, nuclease P1, and the major endogenous nuclease of cell-free extracts were studied. Sensitivity to nuclease attack was not uniform along the deoxyribonucleic acid strand; sequences of strongly protected bases were separated by more sensitive regions. The minimum size of protected fragments was about 70 bases. A complex of protein with the protected deoxyribonucleic acid segments was obtained after partial digestion. The sizes of these complexes, of the protected deoxyribonucleic acid segments, and of the protein subunit released by complete nuclease digestion, are all approximately identical, as determined by gel exclusion chromatography. Deoxyribonucleic acid strands of eclipse complex were also shown to be particularly well protected from attack by the major pneumococcal endonuclease in cell extracts.     

Comparison of the requirements for ribonucleic acid synthesis with the requirements for deoxyribonucleic acid synthesis in animal tissues

Ribonucleic acid polymerase and deoxyribonucleic acid polymerase have been partially purified from bovine lymphosarcoma, lymph node, and thymus. An examination of the deoxyribonucleic acid requirements of the two enzymes indicates that “native” deoxyribonucleic acid is the preferred template for ribonucleic acid synthesis; heat-denatured deoxyribonucleic acid is considerably less active. The primer requirements for deoxyribonucleic acid synthesis differ: “native” deoxyribonucleic acid is usually inactive, while denatured deoxyribonucleic acid is active. The two enzymes also differ in pH optima and in their requirements for metal cofactors.     

Incorporation and excision of 5-fluorouracil from deoxyribonucleic acid in Escherichia coli.

When Escherichia coli are grown in the presence of 5-fluorouracil, the 5-fluorouracil is incorporated almost exclusively into ribonucleic acid as fluorouridylate. In this study, small but detectable amounts were incorporated into ribonucleic acid as fluorocytidylate and into deoxyribonucleic acid as fluorodeoxyuridylate and fluorodeoxycytidylate. The amount of 5-fluorouracil found in deoxyribonucleic acid as fluorodeoxyuridylate increased 50-fold when the cells were deficient in both deoxyuridine triphosphatase and uracil-deoxyribonucleic acid glycosylase activities. Therefore, the same mechanisms which excluded uracil from deoxyribonucleic acid in vivo also excluded 5-fluorouracil. Even though purified uracil-deoxyribonucleic acid glycosylase excised 5-fluorouracil from deoxyribonucleic acid at only 5% the rate with which it excised uracil, most of the 5-fluorouracil excised from deoxyribonucleic acid in vivo was apparently excised directly by uracil-deoxyribonucleic acid glycosylase rather than by repair initiated by excision of uracil.     

Effect of intercalators on the properties of liquid-crystalline dispersions of nucleic acid-chitosan complex

Molecules of deoxyribonucleic acid and synthetic polydeoxyribonucleotides (NA) in the particles of liquid-crystalline dispersions resulting from interaction with chitosan are accessible to interaction with intercalators. The intercalation is accompanied by alteration in the direction of spatial twist of cholesterics of NA-chitosan complexes. This effect is absent in the case of "classical" cholesterics produced from NA molecules via phase exclusion, i.e., the cholesteric structure of NA-chitosan complex is very "labile" as distinct from "classical" cholesteric NA.     

Cyanobacterial ribonucleic acid polymerases recognize lambda promoters.

We compared the initiation specificities in vitro of deoxyribonucleic acid-dependent ribonucleic acid polymerases purified from two cyanobacteria, Fremyella diplosiphon and Anacystis nidulans, and from Escherichia coli. A restriction fragment made from lambda deoxyribonucleic acid was used as a template. The cyanobacterial and E. coli ribonucleic acid polymerases recognized the same lambda promoters but exhibited different sensitivities to the inhibitor heparin, suggsesting differences in the structure of the initiation complexes.     

Purification of polypeptide P6 with a molecular weight of 6,000 from the vegetative chromosomes of Bacillus subtilis.

Folded chromosomes were prepared as membrane-associated complexes from vegetative cells of Bacillus subtilis by stepwise sucrose gradient centrifugation. From nucleoids, a deoxyribonucleic acid-bound polypeptide with a molecular weight of 6,000 (P6) was purified by KCl-(NH4)2SO4 salting out, diethylaminoethyl cellulose column chromatography, and deoxyribonucleic acid cellulose column chromatography. The amino acid composition of polypeptide P6 was determined.