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991.
Rustem Krykbaev Lori J. Fitz Padmalatha S. Reddy Aaron Winkler Dejun Xuan Xiaoke Yang Margaret Fleming Stanley F. Wolf 《Gene》2010
Acidic mammalian chitinase (AMCase), an enzyme implicated in the pathology of asthma, is capable of chitin cleavage at a low pH optimum. The corresponding gene (CHIA) can be found in genome databases of a variety of mammals, but the enzyme properties of only the human and mouse proteins were extensively studied. We wanted to compare enzymes of closely related species, such as humans and macaques. In our attempt to study macaque AMCase, we searched for CHIA-like genes in human and macaque genomes. We found that both genomes contain several additional CHIA-like sequences. In humans, CHIA-L1 (hCHIA-L1) is an apparent pseudogene and has the highest homology to CHIA. To determine which of the two genes is functional in monkeys, we assessed their tissue expression levels. In our experiments, CHIA-L1 expression was not detected in human stomach tissue, while CHIA was expressed at high levels. However, in the cynomolgus macaque stomach tissue, the expression pattern of these two genes was reversed: CHIA-L1 was expressed at high levels and CHIA was undetectable. We hypothesized that in macaques CHIA-L1 (mCHIA-L1), and not CHIA, is a gene encoding an acidic chitinase, and cloned it, using the sequence of human CHIA-L1 as a guide for the primer design. We named the new enzyme MACase (Macaca Acidic Chitinase) to emphasize its differences from AMCase. MACase shares a similar tissue expression pattern and pH optimum with human AMCase, but is 50 times more active in our enzymatic activity assay. DNA sequence of the mCHIA-L1 has higher percentage identity to the human pseudogene hCHIA-L1 (91.7%) than to hCHIA (84%). Our results suggest alternate evolutionary paths for human and monkey acidic chitinases. 相似文献
992.
以L-丙氨酸缓冲液为发芽剂,结合芬顿反应原理,观察发芽-氧化损伤效应对芽胞的杀灭效果,以期为新型炭疽疫源地净化方法的深入研究奠定基础。以腊样芽胞为试验菌,采用透射电镜、激光扫描共聚焦显微镜、活菌计数等方法观察芽胞发芽过程的超微结构、核酸含量变化,以及在芬顿反应的联合作用下发芽体的活性变化。在20~30 min的发芽过程中,芽胞核心密度降低,核心与皮质、皮质与外壁之间界限模糊,芽胞外壁和芽胞衣有破裂,通透性增加,进一步有皮质消失、细胞核与细胞质融合、细胞膜基本形成的现象;发芽体荧光强度不断增加,显示菌体中核酸的活性和含量不断增加;发芽体对化学因子的抗力明显下降,H2O2浓度为0.20 mol/L的Fenton反应系统作用60 min时,发芽体灭活可达到3.016个对数级。诱导发芽和反应的联合处理程序可显著提高芽胞的灭活水平。 相似文献
993.
994.
995.
猪肝酯酶是手性合成中重要的水解酶,在猪肝酯酶的催化下,苯乙二醇环碳酸酯发生水解,生成苯乙二醇。实验围绕影响猪肝酯酶催化反应活性的4个主要因素进行了系统研究,得到了最优的酶浓度(15g/L)、pH值(8.0)、温度(25~30℃)及有机溶剂种类和浓度(二氧六环,65%v/v),为猪肝酯酶催化苯乙二醇环碳酸酯反应的进一步研究奠定了基础。 相似文献
996.
997.
Yu Hirano Makoto Higuchi Hirozo Oh-oka Zheng-Yu Wang 《Journal of molecular biology》2010,397(5):1175-1187
In green sulfur photosynthetic bacteria, the cytochrome cz (cyt cz) subunit in the reaction center complex mediates electron transfer mainly from menaquinol/cytochrome c oxidoreductase to the special pair (P840) of the reaction center. The cyt cz subunit consists of an N-terminal transmembrane domain and a C-terminal soluble domain that binds a single heme group. The periplasmic soluble domain has been proposed to be highly mobile and to fluctuate between oxidoreductase and P840 during photosynthetic electron transfer. We have determined the crystal structure of the oxidized form of the C-terminal functional domain of the cyt cz subunit (C-cyt cz) from thermophilic green sulfur bacterium Chlorobium tepidum at 1.3-Å resolution. The overall fold of C-cyt cz consists of four α-helices and is similar to that of class I cytochrome c proteins despite the low similarity in their amino acid sequences. The N-terminal structure of C-cyt cz supports the swinging mechanism previously proposed in relation with electron transfer, and the surface properties provide useful information on possible interaction sites with its electron transfer partners. Several characteristic features are observed for the heme environment: These include orientation of the axial ligands with respect to the heme plane, surface-exposed area of the heme, positions of water molecules, and hydrogen-bond network involving heme propionate groups. These structural features are essential for elucidating the mechanism for regulating the redox state of cyt cz. 相似文献
998.
In several groups in the order Charadriformes, biparental care is followed by a period of male‐only care. Several hypotheses attempting to explain extended male parental care in shorebirds do not fit the Alcini. In a previous study of Brünnich’s Guillemots Uria lomvia and Razorbills Alca torda, we did not find support for female‐biased parental effort at the breeding site that would lead to males being in better condition to care for chicks at sea. However, in both species, males spent more off‐duty time at the breeding site than females, suggesting greater involvement in the defence of egg or chick, breeding site and mate. We predicted that there would be a male bias in size and aggressive behaviour associated with parental roles. To test this, body size and aggression of attending male and female Brünnich’s Guillemots and Razorbills were measured during incubation and brooding on the Gannet Islands, Labrador. Parental aggression was measured using natural observations of all agonistic interactions and, in Razorbills only, in situ responses to presentations of a predator model. In both species, males were significantly larger than females in culmen and gape length. Guillemot males initiated agonistic interactions more frequently than females during incubation. In contrast, female Guillemots were subjected to aggression more frequently than males and as a result were involved in more fights. In addition, the few chicks that were seen to die were being attended by single females. During the brooding period, Razorbill males responded aggressively to intruders more frequently than females, made more aggressive responses than females, and responded aggressively more frequently and more intensely than females to a predator model. In both species there was a similar male bias in morphology and behaviour that is consistent with male parents being more capable of protecting their chick, a probable advantage to chick survival during the uniparental care phase of some Charadriformes. 相似文献
999.
Rong-Shin Lin 《Inorganica chimica acta》2010,363(13):3523-2592
Condensation of tetraphenylporphyrin-2,3-dione with 1,10-phenanthroline-5,6-diamine provided porphyrinphenanthroline (2) as the desired ligand. Metallation of the porphyrinic site of 2 with CoCl2, NiCl2, ZnCl2 and CuCl2 afforded the corresponding metal complexes [Co(2)] (8a), [Ni(2)] (8b), [Zn(2)] (8c) and [Cu(2)] (8d), respectively. Subsequent reactions of these metalloporphyrins with [(COD)PdCl2] yielded the corresponding bimetallic complexes [Co/Pd (9a), Ni/Pd (9b), Zn/Pd (9c) and Cu/Pd (9d)] in high yields. The bimetallic complex 9e (Mg/Pd) was prepared directly by complexation of 2 with MgBr2 and [(COD)PdCl2]. All complexes were characterized by both spectroscopic and elemental analyses. In addition, crystal structure of 9c was determined to confirm its formulation. The use of these bimetallic complexes as pre-catalysts for Mizoroki-Heck coupling reaction has been examined. 相似文献
1000.
Chin-Pei Chang 《Inorganica chimica acta》2010,363(2):412-3748
The reaction of (η5-C5H4iPr)Co(PPh3)2 with PhCCPPh2 furnished two isomeric cyclobutadiene-substituted Cp′CoCb diphosphines, [(η5-C5H4iPr)Co(η4-1,2-(PPh2)2C4Ph2)] (5-cis) and [(η5-C5H4iPr)Co(η4-1,3-(PPh2)2C4Ph2)] (5-trans). Further reaction of 5-cis with one molar equivalent of Pd(COD)Cl2 gave palladium complex [(η5-C5H4iPr)Co(η4-1,2-(PPh2)2C4Ph2)-PdCl2] (6) in good yield. Both of the molecular structures of 5-cis and 6 were determined by single-crystal X-ray diffraction methods. Unexpectedly, the palladium complex 6 was found to be more efficient than the combination of the commonly used Buchwald’s ligand, biphenyl-2-yl-di-tert-butyl-phosphane, with Pd(OAc)2 as the catalytic precursor in the Suzuki-Miyaura reaction between ferroceneboronic acid and 4-bromoaldehyde. The X-ray structural analysis and DFT study of several palladium complexes containing sandwich-type diphosphine chelating ligands revealed that the variations in bite angles are much larger than those in bite distances. The more energetically favorable conformation in the Pd(II) complexes is the one with bite angle close to 90°. 相似文献