黑麦草叶片超氧化物歧化酶

采用硫酸铵分级沉淀和柱层析方法 ,从黑麦草叶片中分离得到纯的铜锌超氧化物岐化酶。经鉴定该酶是Cu·Zn SOD。测得其分子量约为 3 2 1 0 0 ,亚基分子量约 1 5 90 0。该酶的N 末端为丙氨酸 ,其紫外光区最大吸收峰在 2 5 4nm。该酶的热稳定性较好 ,65℃保温 1h仍保留活性 2 7%。氨基酸组成分析表明 ,黑麦草SOD由 2 1 2个氨基酸残基组成 ,而且不含色氨酸。     

外源铜增强天然铜锌超氧化物歧化酶断裂DNA的活性

铜锌超氧化物歧化酶（CuZnSOD）作为一种抗氧化酶, 最重要的功能是催化超氧阴离子歧化为过氧化氢和氧气。然而最近研究发现CuZnSOD具有过氧化物酶活性,能导致核酸、蛋白质和细胞膜的损伤。本工作采用光谱学和酶学方法研究外源Cu(Ⅱ)与CuZnSOD之间的相互作用,以及H₂O₂存在下外源Cu(Ⅱ)对 CuZnSOD断裂DNA活性的增强效应。比较CuZnSOD + nCu(Ⅱ) (n=0, 1, 2, 4, 6, 8)和单独Cu(Ⅱ)分别断裂DNA的活性,表明外源Cu(Ⅱ)的加入可显著增强CuZnSOD断裂DNA的活性。相对酶活力和稳态动力学的测定证实了这种增强效应。pH依赖性实验表明断裂DNA的最适pH范围为pH3.6-5.6和pH9.0-10,在不同的pH区域CuZnSOD + nCu(Ⅱ)断裂DNA途径可能不同。     

芽孢杆菌L4所产角蛋白酶的纯化工艺、理化性质及其应用研究

根据芽孢杆菌L4菌株发酵产生的角蛋白酶的分子量和等电点等特征,分别采用硫酸铵盐析沉淀,Sephadex G-75凝胶过滤、DEAE-cellulose 52离子交换和Sepharose 4B凝胶过滤等色谱层析对其进行分离纯化,经SDS-PAGE检测呈现单一条带,分子量为149kD;变性电泳结果显示,该酶由4个分子量约为37.5kD的亚基组成;采用等电聚焦电泳测得其等电点为7.76,并通过纸层析法初步确认该酶为高甘露糖型糖蛋白;最后通过羊毛水解实验确认该酶具有水解羊毛角蛋白的能力,在羊毛仿羊绒等领域具有一定的应用价值.     

蓖麻蚕脂肪体精氨酸酶的分离纯化及其性质的研究

本文利用丙酮处理,硫酸铵沉淀,DEAE纤维素层析,Sephadex G-50凝胶过滤等步骤提纯了蓖麻蚕精氨酸酶。该酶由两个分子量80,000的亚基组成,等电点为5.3,并测定了氨基酸组成。动力学实验表明酶的K_m值为20m M,精氨酸代谢的产物鸟氨酸及脯氨酸对该酶有竞争性抑制作用,最适pH为9.0,Mn~( )为酶表现活力所必需。苯甲磺酰氟及巯基乙醇可能通过作用于酶活性基团和影响其高级结构而抑制该酶。此外,还将蓖麻蚕精氮酸酶与大鼠及鸡肝脏精氨酸酶进行了一些比较。     

黑曲霉木聚糖酶同工酶的性质及圆二色谱分析

对黑曲霉木聚糖酶同工酶的酶学性质及圆二色谱(CD)进行了研究.结果表明,黑曲霉木聚糖酶粗酶液经离心、超滤及SephadexG-75凝胶层析后,分离得到了两个黑曲霉木聚糖酶同工酶组分XⅠ,XⅡ,其最适反应温度均为45℃～55℃,最佳反应pH值均为4 8～5 5,SDS-PAGE法测得XⅠ,XⅡ的相对分子质量分别为2.2×104和4.0×104.XⅠ与XⅡ的CD光谱表明,XⅠ,XⅡ分别在218和215nm处有最大负峰,说明β-折叠结构是组分XⅠ,XⅡ具有木聚糖酶活性的主要结构,也是它们发挥催化功能的结构基础.     

二价金属离子激活铜超氧化物歧化酶断裂DNA的活性

以铜超氧化物歧化酶(CunSOD, n＝1—4)作为野生型CuZnSOD突变体的一种模型, 研究了其在二价金属离子(Mg2+, Mn2+)存在下由非氧化途径断裂DNA的活性, 并与CuZnSOD和脱辅基SOD(apoSOD)进行了比较. 结果表明, 在Mg2+或Mn2+存在下, CunSOD断裂DNA的活性高于CuZnSOD和apoSOD, 并且DNA的断裂活性受二价金属离子浓度、pH及酶浓度等因素影响. 相对活性及动力学参数的测定结果表明, CunSOD断裂DNA的相对能力按Cu1SOD2SOD≈Cu4SOD3SOD的顺序变化.     

黄豆铁蛋白提取新方法及其与豌豆铁蛋白活性比较

铁蛋白是广泛存在于动物、微生物及植物体中的一种铁贮藏蛋白, 具有去除二价铁的毒性以及调节机体细胞铁代谢平衡的作用. 本文以黄豆种子为原料, 开发出黄豆铁蛋白提取新方法, 即将黄豆粗提液在55 ℃下加热15 min, 再将冷却后的上清液分别用500 mmol/L MgCl2和700 mmol/L柠檬酸三钠进行盐析. 离心得到的铁蛋白粗提液经透析后, 用DEAE-cellulose弱阴离子交换层析和Sephacryl S-300凝胶过滤层析进一步分离, 得到电泳纯的铁蛋白. Native-PAGE电泳测得分子量约为560000, SDS-PAGE电泳结果表明, 黄豆铁蛋白含有两种亚基, 分子量分别为28000和26500. 活性研究显示, 黄豆铁蛋白与豌豆铁蛋白铁氧化沉淀和还原释放反应的活性明显不同.     

游离125I与血浆蛋白的结合及其对血药浓度测定的影响

通过体内、外实验, 研究了游离125I与血浆蛋白的结合及其在三氯乙酸(TCA)沉淀后的沉淀百分率, 并与125I-RGD-Sak在SD大鼠中不同时间血药浓度的结果进行了比较. 结果表明, 游离125I能与血浆蛋白结合, 并为TCA所沉淀, 且在一定范围内, 游离125I与血浆蛋白结合后的沉淀百分率与温育时间及游离125I的活度无关. 体内、外实验中, 游离125I与血浆蛋白结合后的沉淀百分率分别为(1.26±0.14)%及(1.38±0.33)%. 沉淀物中含有吸附在沉淀物表面的游离125I, 该吸附需要用TCA沉淀2~3次才能去除. 采用125I核素示踪法进行生物类制品的药代动力学研究时, 应对游离125I的影响进行校正.     

双氧水分别与氯化亚铁和碘化钾反应的问题探究

FeCl2、KI分别与双氧水反应,生成Fe(OH)3沉淀和I2吗?通过实验对2个反应的复杂性进行了探索,并对实验现象进行了理论分析.     

伴大豆球蛋白亚基色谱分离和制备及结构表征

研究了色谱方法对伴大豆球蛋白组成3个亚基的分离纯化工艺条件,并利用圆二色光谱对纯化得到的3个亚基的二级结构和三级结构进行了表征.结果显示:利用离子交换色谱(DEAE-sepharose fast flow, DEAE为二乙氨乙基)和金属螯合层析(Immobilized metal affinity column, IMAC)相结合的方法,能将3个亚基组分完全分开,得到了能制备相对大量的3个亚基α′, α和β的稳定工艺,纯度为95%,回收率达75%.远紫外CD结果显示,在3个亚基的二级结构中, α螺旋较少,但都具有较高含量的β折叠和无规卷曲; 近紫外CD结果显示, 3个亚基在制备过程中因为尿素的变性作用,都已经散失了三级结构.     

二氧化碳和丙烯直接合成甲基丙烯酸的NiPMo/TiO2催化剂的研究

用溶胶-凝胶法以磷钼酸(MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2催化剂.使用ICP、 XRD、 TG-DTA、 IR、 TPD-MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能.杂多钼酸盐与TiO2通过O2-在TiO2表面发生了键合.在623 K下,杂多阴离子仍保持原有的Keggin结构.CO2在Lewis酸位Ni(Ⅱ)和Lewis碱位Ni-O-Mo的桥氧协同作用下生成CO2卧式吸附态Ni(Ⅱ)←O-(CO)←(O--Ni).丙烯有多种吸附态在催化剂上吸附.在563 K、 1 MPa和空速1500 h-1的反应条件下,丙烯的摩尔转化率为3.2%,产物MAA选择性为95%.     

Toward new camptothecins. Part 6: Synthesis of crucial ketones and their use in Friedländer reaction

In the context of the preparation of camptothecin and luotonin A analogs, the synthesis of some key keto-precursors and their use in Friedländer condensation are described. This paper also focuses on the stability of these keto intermediates and emphasizes the major differences between indolizinones and pyrroloquinazolinones series. Noteworthy is also the report of some original structures isolated as by-products of some experiments.     

α-Amino acid derived enaminones and their application in the synthesis of N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates and other heterocycles

A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives.     

Specific intramolecular aromatic CH insertion of diazosulfonamides

The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp³)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp²)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp²)?H and aliphatic 1,5- and 1,6-C(sp³)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp³)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp²)?H insertion.     

CoFe2O4自形成磁性液体场致结构化对磁化的影响

The Langevin paramagnetic theory can’t describe the relation between magnetization of ferrofluids and applied magnetic field. The structuralization of ferrofluids, which is considered the main influence factor of the magnetization, is regarded. The part of magnetization works is deposited when the structure is forming. This action influences the magnetization of ferrofluids directly or indirectly. On the base of the “compressing” model, the Langevin function that usually describes the magnetization of ferrofluid is modified, and a well-fitted curve is obtained. An equation of the relation between the equivalent volume fraction after being “compressed” and the intensity of magnetic field is discovered, which approximately describes the process of magnetization. The relation between the approximate initial susceptibility and the volume fraction can be obtained from modified formula.     

KMnO4-mediated oxidative CN bond cleavage of tertiary amines: Synthesis of amides and sulfonamides

KMnO₄-mediated oxidative CN bond cleavage of tertiary amines producing secondary amine was introduced, which was trapped by electrophiles (acyl chloride and sulfonyl chloride) to form amides and sulfonamides. The reaction could take place at mild condition, tolerating a wide range of function groups and affording products in moderate to excellent yields.     

Highly regioselective Buchwald–Hartwig amination at C-2 of 2,4-dichloropyridine enabling a novel approach to 2,4-bisanilinopyridine (BAPyd) libraries

The highly regioselective Buchwald–Hartwig amination at C-2 of the cheap and readily accessible reagent, 2,4-dichloropyridine with a range of anilines and heterocyclic amines is described. This new methodology is robust and provides a facile access to 4-chloro-N-phenylpyridin-2-amines on 0.25 mol scale. These intermediates undergo a further Buchwald–Hartwig amination at higher temperature to enable rapid exploration of the chemical space at C-4 and to provide a library of 2,4-bisaminopyridines.     

Chemistry of heterocyclic compounds at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, over 50 years (Review)

The review contains a concise historical account and information on the most significant researches undertaken by the staff at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences on the Chemistry of Heterocyclic Compounds. Dedicated to Academician of the Russian Academy of Sciences B. A. Trofimov on his 70th jubilee. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1443–1502, October, 2008.     

N-Heterocyclic carbene-palladacyclic complexes: synthesis,characterization and their applications in the C-N coupling and α-arylation of ketones using aryl chlorides

N-Heterocyclic carbene-palladacyclic complexes 3 were successfully achieved in a one-pot procedure under mild conditions. The structure of 3a was unambiguously confirmed by X-ray single crystal diffraction and it was an active catalyst in the Buchwald-Hartwig amination and α-arylation of ketones even at very low catalyst loadings (0.01?mol%).     

Iodine-mediated oxidative Pictet-Spengler reaction using terminal alkyne as the 2-oxoaldehyde surrogate for the synthesis of 1-aroyl-β-carbolines and fused-nitrogen heterocycles

An efficient iodine-mediated oxidative Pictet-Spengler reaction in dimethyl sulphoxide (DMSO) using terminal alkynes as the 2-oxoaldehyde surrogate for the synthesis of aryl (9H-pyrido[3,4-b]indol-1-yl)methanones is described. The scope of the protocol includes the total synthesis of Fascaplysin, Eudistomins Y₁ and Y₂. The methodology is extended for preparing pyrrolo[1,2-a]-quinoxaline and indolo[1,5-a]quinoxaline derivatives. The utility of 1-aroyl-β-carbolines was demonstrated by performing palladium-catalyzed β-carboline directed ortho-C(sp2)-H functionalization of the phenyl ring with thiomethyl (SMe) group using DMSO as source and for accessing 4-aryl-canthin-6-ones.