腺嘌呤与3-[二(羧甲基)氨甲基]-1,2-二羟基蒽醌-3-甲基胺-N,N-二乙酸化学反应的UV光谱研究

核酸的基本结构是核苷酸.核苷酸(nucleotide)还可以进一步分解成核苷(nucleoside)和磷酸,核苷再进一步分解成碱基和戊糖.碱基又分为两大类:嘌呤碱和嘧啶碱.在有关的研究中对核酸和蛋白质探针的研究较多,如3-[二(羧甲基)氨甲基]-1,2二羟基蒽醌与蛋白质作用的研究[1]、脱氧核糖核酸与3氨基-6-二甲氨基2甲基吩嗪盐酸盐反应机理的研究[2]等,对核酸中碱基的研究已在起步中[3,4].     

血氨对运动应答的变化规律及应用方法研究

运动会使机体血氨升高,短时间剧烈运动主要来源于骨骼肌嘌呤核苷酸循环,长时间力竭性运动主要是由于支链氨基酸的大量降解;运动强度、持续时间、训练水平均会影响运动后血氨的变化情况,运动性疲劳也与氨的积累密切相关.因此,可以应用血氨指标评定运动强度和量度、训练水平、疲劳程度和机能状态.文中还对该指标在应用时几点须注意的问题进行了说明.     

肉鸭肝脏脂肪酸合成酶活性及脂肪酸合成途径的研究

利用放射线检测器和分光光度计,对肉鸭肝脏中参与脂肪酸合成的酶类:乙酰辅酶-A羧化酶,脂肪酸合成酶,NADP-苹果酸脱氢酶,葡萄糖-6-磷酸脱氢酶等酶的活性进行了测试分析.结果表明,肉鸭肝脏的各种脂肪酸代谢酶类的活性表现为:42日龄比21日龄的显著增加,显示随着日龄的增加,鸭肝脏合成脂肪的能力也显著增强.鸡的肝脏进行脂肪酸合成所必需的NADPH主要是由NADP-苹果酸脱氢酶参与的丙酮酸-苹果酸途径提供.与此相比,鸭的葡萄糖-6-磷酸脱氢酶的活性非常高,显示鸭的脂肪酸合成途径与鸡不同,脂肪酸的合成不仅仅有丙酮酸-苹果酸途径参与,戊糖磷酸循环也起到关键性的作用.     

细菌纤维素生物合成网络的构建及代谢通量分析

构建了木醋杆菌合成细菌纤维素(Bacterial Cellulose,简称 BC)的代谢网络.基于流量平衡模型,通过物料衡算和Lingo线性规划,得到发酵前期和后期BC合成的代谢通量分布.代谢通量分析结果表明,葡萄糖进入磷酸戊糖途径(PPP)和三羧酸(TCA)循环,前期菌体大量合成,BC产量较高;后期形成大量无效循环,BC产量降低.由于部分代谢流流向副产物和无效循环,减少了合成BC的代谢流,造成了碳源的浪费,所以需通过遗传改造、诱变或改变发酵条件等方法,减少副产物生成,提高BC的产率.     

环腺苷二磷酸核糖(cADPR)类似物的合成与诱导钙释放活性的研究

Ca2 信号传导通路是生物体内重要的胞内信号传导途径之一.局部钙信号主要来源于细胞内钙库释放,而这些钙信号受到各种第二信使的控制和Ca2 通道蛋白的调节.环腺苷二磷酸核糖(cADPR)作为烟酰胺腺嘌呤二核苷酸(NAD )的代谢物,发现于1987年,是一种信号传导分子,它广泛存在于各种生物系统中,通过介导兰诺定(RyR)受体调节钙动员活性.研究cADPR以及具有不同生物活性的类似物之间的构效关系是探究分子内钙释放机制的主要手段,另外,一些结构新颖的拮抗剂和激动剂可以作为研究细胞系统复杂机制的研究工具.作者概括性地介绍了cADPR结构类似物--N1-乙氧基甲基-环肌苷-5'-二磷酸核糖(cIDPRE)和N1-[(磷酰基-O-乙氧基)-甲基-N9-[(磷酰基-O-乙氧基)-甲基-次黄嘌呤-环磷酸焦酯(cIDPDE)的合成与性质.这两种类似物cIDPDE和cIDPRE可作为研究完整细胞钙信号系统的膜透性激动剂.     

谷氨酸棒杆菌发酵生产1,5–戊二胺的代谢流分析

为了提高糖类的利用效率,加强糖类代谢向生成尸胺的方向流动,提高尸胺产量,对谷氨酸棒杆菌合成尸胺的代谢网络进行分析,找出影响尸胺合成的代谢流量分配规律和关键节点,并通过改变溶氧及添加辅酶NADPH对关键节点进行验证.结果表明:6–磷酸葡萄糖和丙酮酸是影响碳源流向尸胺合成的关键节点,增强磷酸戊糖途径(HMP)和三羧酸循环(TCA)可以弱化由6–磷酸葡萄糖生成6–磷酸果糖和由丙酮酸生成乳酸,促进碳源向合成尸胺的方向流动,从而有效地提高尸胺产量(产量增幅为77.8%).该研究为高产尸胺的谷氨酸棒杆菌工程菌种改造以及发酵控制提供了理论基础.     

核糖核苷酸还原酶研究

核糖核苷酸还原酶广泛存在于各种生物中,是生物体内唯一的催化4种核糖核苷酸还原、生成相应的脱氧核糖核苷酸的酶。该酶是DNA合成和修复的关键酶和限速酶,对细胞的增殖和分化起着调控作用。不同生物中的RR根据其结合的金属辅助因子不同而分类。虽然不同类型RR之间的氨基酸序列相似性很低,但它们有十分相似的三级结构的活性中心和相同的催化功能。RR分子中包含2个变构位点,即酶活性中心和底物特异结合位点。活性中心通过生物有机自由基的作用催化核糖核苷酸还原;底物特异结合位点通过变构作用调控4种dNTPs在细胞内的平衡。因此,该酶不仅是研究DNA合成与修复、细胞增殖与分化及癌症的治疗与抗癌药物开发的重要靶点,同时也是研究酶的结构与功能以及酶的催化机理等的重要工具。本文总结了该酶的种类与分布、结构特征、催化机理及作为抗癌药物开发靶点等方面的研究进展。     

寡聚核糖核苷酸降解酶影响铜绿假单胞菌的能量代谢

铜绿假单胞菌是一种自然界中广泛存在的革兰氏阴性条件致病菌.在该菌的RNA代谢过程中,存在一种以NanoRNA(2-5nt的寡聚核糖核苷酸)为底物的寡聚核糖核苷酸降解酶(Oligoribonuclease, Orn).在本研究中,发现铜绿假单胞菌orn突变菌株的生长速度变慢,因此使用ATP,NADH检测试剂盒,利用酶标检测法和流式细胞分析研究Orn对细菌生理状态的影响.研究结果表明,铜绿假单胞菌orn基因的缺陷可以导致细菌胞内NADH和细菌细胞膜电位差的降低.这进一步导致细菌胞内ATP合成的降低,从而影响细菌的能量代谢.     

核能补剂对大鼠骨骼肌高能磷酸化合物变化的影响

通过实验观察了核能补剂对大鼠骨骼肌高能磷酸化合物变化的影响。大鼠反复进行3次2min的高速跑台运动,其运动后第24h腓肠肌中高能磷酸化合物的变化提示:核能补剂组骨骼肌中ATP的含量明显比复合肌酸组和空白对照组高(p<0.01);核能补剂组骨骼肌中PCr的含量明显比空白对照组高(p<0.01)。本实验证实了核能补剂能加快骨骼肌ATP的生成速度,并提高骨骼肌中磷酸肌酸的储量。     

5例原发性痛风患者HPRT基因的克隆和序列分析

原发性痛风是先天性嘌呤代谢缺陷症，与嘌呤代谢相关两次黄嘌呤—鸟嘌呤磷酸核糖转移酶(HPRT，EC2．4．2．8)、磷酸核糖焦磷酸合成酶(PRS)等缺陷有关。克隆了正常中国人和4个中国原发性痛风家族5位患的HPRT基因，序列分析表明，正常中国人及Case5患的HPRT编码区序列与报道的序列(GeneBank登录号M26434)完全一致，而在3个中国痛风家族4位患的HPRT基因编码区中共发现11个新突变，包括3个同义突变、1个元义突变和7个错义突变。这是关于中国大陆原发性痛风患HPRT基因突变的首次报道。     

糖类遗传与生命起源

从遗传学角度探讨了糖类与生命起源，讨论了遗传学上的再认识，提出糖类在遗传学上扮演着重要、核心的角色、糖类是生命起源物质，基因是糖类衍生物。生命诞生过程可能是：先有糖类、然后有氨基酸和碱基；磷酸及其盐类既是生命物质的组成部分、也是催化剂，阳光或地热为能源，于是诞生了基因。生命体是分子相互作用、有序组合、自我调控的耗散体系。     

Prediction of potential antimalarial targets of artemisinin based on protein information from whole genome of Plasmodium falciparum

On the basis of the genomic data and protein pathway information about Plasmodium falciparum clone 3D7 from the NCBI taxonomy database and the KEGG database, eight key protein enzymes in the signal pathways were selected to perform molecular docking with artemisinin. The binding modes obtained from the molecular docking suggested that purine nucleoside phosphorylase （pfNP）, peptide deformylase （pfPDF）, and ribose 5-phosphate isomerase （pfRpiA） may be involved in the antimalarial mode of action of artemisinin. Artemisinin exhibited its antimalarial activity probably by interfering with the metabolic pathways of purine, pyrimidine, methionine, glyoxylate and dicarboxylate, or pentose phosphate.     

嗜酸氧化亚铁硫杆菌的核糖-5-磷酸异构酶的同源建模研究

采用同源建模技术和分子动力学模拟方法,构建了嗜酸氧化亚铁硫杆菌Acidithiobacillus ferrooxidans(A.f)的核糖-5-磷酸异构酶(rpiA)基因编码的蛋白质三维分子结构模型。将结构模型进行绑定位点搜索并与底物核糖-5-磷酸(R5P)进行柔性分子对接,结果显示,R5P被招募到A.ferrooxidans的RpiA的活性位点并随后被激活;残基Asp81,Thr31,Lys121,Ser30,Glu103,Asp84,Lys94,Asp118,Lys7,Gly97,Gly29,Gly95,Thr28和H2O对底物绑定或催化起重要作用,其中,Gly97,Gly29,Gly95和Thr28是新识别的残基,它们在其他生物体的RpiA中相当保守但未被发现。     

Crystal structure of an RNA double helix incorporating a track of non-Watson-Crick base pairs

The crystal structure of the RNA dodecamer duplex (r-GGACUUCGGUCC)2 has been determined. The dodecamers stack end-to-end in the crystal, simulating infinite A-form helices with only a break in the phosphodiester chain. These infinite helices are held together in the crystal by hydrogen bonding between ribose hydroxyl groups and a variety of donors and acceptors. The four noncomplementary nucleotides in the middle of the sequence did not form an internal loop, but rather a highly regular double-helix incorporating the non-Watson-Crick base pairs, G.U and U.C. This is the first direct observation of a U.C (or T.C) base pair in a crystal structure. The U.C pairs each form only a single base-base hydrogen bond, but are stabilized by a water molecule which bridges between the ring nitrogens and by four waters in the major groove which link the bases and phosphates. The lack of distortion introduced in the double helix by the U.C mismatch may explain its low efficiency of repair in DNA. The G.U wobble pair is also stabilized by a minor-groove water which bridges between the unpaired guanine amino and the ribose hydroxyl of the uracil. This structure emphasizes the importance of specific hydrogen bonding between not only the nucleotide bases, but also the ribose hydroxyls, phosphate oxygens and tightly bound waters in stabilization of the intramolecular and intermolecular structures of double helical RNA.     

Localization of the malignant hyperthermia susceptibility locus to human chromosome 19q12-13.2

Malignant hyperthermia (MH) is an inherited human skeletal muscle disorder and is one of the main causes of death due to anaesthesia. The reported incidence of MH varies from 1 in 12,000 in children to 1 in 40,000 in adults. MH is triggered in susceptible people by all commonly used inhalational anaesthetics; it is characterized by a profoundly accelerated muscle metabolism, contractures, hyperthermia and tachycardia. Susceptibility to MH (MHS) is predicted by contracture tests on muscle tissue obtained by biopsy. An almost identical disorder known as porcine MH exists in pigs. The genetics of the porcine syndrome have been extensively studied; the locus controlling expression of porcine MH is genetically linked to the glucose phosphate isomerase locus (GPI). In man, GPI has been mapped to the q12-13.2 region of chromosome 19 (refs 10-12). We have now investigated genetic linkage in several extended Irish pedigrees in which MHS is segregating as an autosomal dominant trait. Here we show linkage between MHS and DNA markers from the GPI region of human chromosome 19 with a maximum log likelihood ratio (lod score) of 5.65 at the CYP2A locus. These results indicate that human and porcine MH are most probably due to mutations in homologous genes, and also provide a potentially accurate and noninvasive method of diagnosis for MHS.     

An electrochemical and Raman spectroscopic study on involvement of La3+ ions in lactate dehydrogenase catalysis

The influence of La 3+ on lactate dehydrogenase catalysis was investigated by electrochemical and FT-Raman techniques. The results showed that La 3+ ions bind preferably with phosphate moiety and ribose group (3′-OH) connected to nicotinamide in coenzyme NAD +/NADH, destabilize the enzyme-coenzyme complex and inhibit LDH activity.     

环己六醇在茶树儿茶素生物合成中的作用(英文)

术文利用放射性同位素生物标记法,对环己六醇在茶树儿茶素生物合成中的作用作了研究.提出了环已六醇至少通过两条路线参与儿茶素的生物合成;1.经由戊糖到PPP 途径;2.经由己糖到EMP 途径.然后,环已六醇逐渐转变形成莽草酸途径的先质,最后,通过莽草酸途径参入到儿茶素中.m—环已六醇直接形成茶多酚的可能性不大.     

Icariin on relaxation effect of corpus cavernosum smooth muscle

NO-cGMP pathway in penile corpus cavernosal smooth muscle plays an important role in penile erection. The level of cGMP is regulated by a balance between the rate of synthesis by guanylate cyclase and the rate of hydrolytic breakdown to guanosine 5′ monophosphate (GMP) by phosphodiesterase 5(PDE5). Icariin is isolated from natural drug Epimedii herba, it is shown to have the relaxation effect on corpus cavernosal smooth muscle of rabbit (IC50: 4×10⁻⁴ mol/L), and the mechanism of the relaxation effect of Icariin on corpus cavernosum believed to have the inhibiting effect on PDE5 and activation of NO-cGMP pathway to enhancing penile erection.     

How guanylate-binding proteins achieve assembly-stimulated processive cleavage of GTP to GMP

Interferons are immunomodulatory cytokines that mediate anti-pathogenic and anti-proliferative effects in cells. Interferon-gamma-inducible human guanylate binding protein 1 (hGBP1) belongs to the family of dynamin-related large GTP-binding proteins, which share biochemical properties not found in other families of GTP-binding proteins such as nucleotide-dependent oligomerization and fast cooperative GTPase activity. hGBP1 has an additional property by which it hydrolyses GTP to GMP in two consecutive cleavage reactions. Here we show that the isolated amino-terminal G domain of hGBP1 retains the main enzymatic properties of the full-length protein and can cleave GDP directly. Crystal structures of the N-terminal G domain trapped at successive steps along the reaction pathway and biochemical data reveal the molecular basis for nucleotide-dependent homodimerization and cleavage of GTP. Similar to effector binding in other GTP-binding proteins, homodimerization is regulated by structural changes in the switch regions. Homodimerization generates a conformation in which an arginine finger and a serine are oriented for efficient catalysis. Positioning of the substrate for the second hydrolysis step is achieved by a change in nucleotide conformation at the ribose that keeps the guanine base interactions intact and positions the beta-phosphates in the gamma-phosphate-binding site.