排序方式: 共有73条查询结果,搜索用时 31 毫秒
51.
Volker Schellenberger Ute Schellenberger Yuri V. Mitin Hans-Dieter Jakubke 《Monatshefte für Chemie / Chemical Monthly》1989,120(5):437-443
Summary The papain-catalyzed reaction of esters of Z-alanine with various arginine esters was investigated. Using H-Arg-OPr
i as a nucleophile the expected dipeptide product results in high yield. Otherwise, reactions with arginine esters of primary alkohols provide products undergoing further reactions. This allows the synthesis of N-protected peptide esters containing two or more arginine residues in a one-step reaction. The influence of reaction conditions on the process was investigated.
AbkürzungenDie IUPAC/IUB-Regeln für Aminosäure- und Peptidderivate wurden befolgt; vgl. Eur. J. Biochem.53, 1 (1975). Die verwendeten Aminosäuren hatten (L)-Konfiguration.-Glo-Gly-OH=Glykolylglycinester,-OCam=Carboxamidomethylester, -OBu i=Isobutylester,-OMe=Methylester,-OPr i=Isopropylester,Z=Benzyloxycarbonyl. 相似文献
52.
A rapid, easy and reproducible capillary electrophoresis (CE) method for the simultaneous determination of allantoin, choline and arginine in Rhizoma Dioscoreae was developed first time. Under the optimum condition, the three analytes could be well separated within 5 min in a 70 cm (60 cm effective length) x 75 microm i.d. capillary. The relative standard deviations for both migration time and peak height were less than 3.20%. The linear response range was 5.0-150, 0.9-100 and 1.0-200 microg/ml for arginine, choline and allantoin, respectively. The detection limit of three components was 2.0, 0.4 and 0.5 microg/ml for arginine, choline and allantoin, respectively. Contents of arginine, choline and allantoin in the crude drug of Rhizoma Dioscoreae could be easily determined by the proposed method with satisfactory results. 相似文献
53.
碱性蛋白质毛细管电泳分离研究 总被引:1,自引:0,他引:1
碱性蛋白质毛细管电泳分离研究任吉存,邓延倬,程介克(武汉大学化学系分析测试科学系,武汉,430072)关键词毛细管电泳,碱性蛋白质,吸附,精氨酸,赖氨酸蛋白质的吸附作用严重影响了毛细管电泳分离蛋白质的重现性[1].为此,人们寻找各种途径来克服蛋白质的... 相似文献
54.
The kinetics of uncatalysed and Cu(II) catalysed oxidation of arginine monohydrochloride was investigated. Both reactions follow a singular order dependence each in oxidant and substrate. An inverse order dependence is reported with the alkali concentration. A plot of observed rate constant versus Cu(II) concentrations Cu(II)2.0×10–5
M is linear; from the intercept the rate constant for the uncatalysed pathway was calculated. However, at high copper ion concentrations i.e. Cu(II)>2.0×10–5
M a fixed value of rate constant was found for all catalyst concentrations. Added neutral salts show an insignificant effect on the reaction rate. Mechanisms were proposed for both cases and rate expressions were derived by applying steady state assumptions.
Die Kinetik der alkalischen Chloramin-T-Oxidation von Arginin-monohydrochlorid mit und ohneCu(II) als Katalysator
Zusammenfassung Die Oxidation erfolgt sowohl mit als auch ohne Cu(II)-Katalysator in erster Ordnung bezüglich des Oxidationsmittels und des Substrats; inverse Ordnung wird bezüglich der Alkalikonzentration beobachtet. Bis zu einer Cu(II)-Konzentration von2×10–5 M ist die Geschwindigkeitskonstante der Katalysatorkonzentration proportional; darüber wird eine konstantbleibende Geschwindigkeit beobachtet, die nun von der Cu(II)-Konzentration unabhängig ist. Neutralsalze haben keinen Effekt auf die Geschwindigkeitskonstante. Es wird für den katalysierten und unkatalysierten Reaktionsablauf ein Mechanismus vorgeschlagen und ein mathematischer Ansatz präsentiert.相似文献
55.
Ricardo C. Santana Jesiel F. Carvalho Ivo Vencato Hamilton B. Napolitano Adailton J. Bortoluzzi Gastón E. Barberis Raul E. Rapp Mario C.G. Passeggi Rafael Calvo 《Polyhedron》2007
A novel dinuclear copper(II) complex with the amino acid l-arginine (l-arg), with mono and bidentate HPO42− oxoanions and an OH− anion. [Cu2(l-arg)2(μ-HPO4-O)(μ-HPO4-O,O′)(μ-OH)]− · (H3O)+ · 6H2O (1) was prepared and its structure was determined by X-ray diffraction methods. The two independent copper ions are in a distorted square pyramidal coordination, each bonded to one l-arginine molecule. These two Cu(l-arg) units are bridged by two monoatomic equatorial–apical oxygen ligands belonging to a monodentate hydrogenphosphate group, and to the hydroxyl group. The copper ions in the dinuclear unit at d = 3.1948(8) Å are also connected by two equatorial oxygen belonging to a bidentate hydrogenphosphate. This dinuclear character and bridging scheme, not common for metal–amino acid compounds, is a consequence of the properties of the phosphate anions. The magnetic susceptibility at temperatures between 2 and 300 K and the isothermal magnetization curves at T = 2.29(1) K with applied fields up to 9 T were measured. The magnetic data indicate an antiferromagnetic intradinuclear exchange coupling J/kB = −3.7(1) K and using a molecular field approximation we estimated a weaker ferromagnetic interaction J′/kB ∼ 0.3 K between neighbour dinuclear units. 相似文献
56.
精氨酸残基在质子化多肽RRMKWKK的气相碰撞诱导解离过程中的作用 总被引:1,自引:0,他引:1
用ESI/MS-MS方法研究了质子化多肽RRMKWKK 在低能气相碰撞诱导解离(CID)条件下的碰撞能和解离路径. 研究结果表明, [M+2H]2+和[M+3H]3+的CID断裂曲线和断裂位点相似. 但质子化多肽所含正电荷个数不同时, 产生同一碎片离子的初始碰撞能不同. 碱性氨基酸残基精氨酸(Arg)的支链是多肽RRMKWKK质子化时质子优先结合的位点, 导致含有Arg的多肽在气相碰撞诱导解离条件下解离时需要较高的碰撞能. 在用质谱方法研究含精氨酸残基的多肽时应选择质子个数比多肽中Arg个数多1个的母体离子. 质子化多肽RRMKWKK的结构AM1计算结果表明, 质子化RRMKWKK中两个相邻精氨酸在空间上相互分离, 库伦斥力的影响不足以改变质子的优先结合位点. 相似文献
57.
建立了一种新的基于碰撞诱导解离(CID)碎裂模式鉴定精氨酸-腺苷二磷酸(ADP)-核糖基化多肽的新方法. 首先,在碱性条件下将精氨酸-ADP-核糖基化血管紧张素-Ⅰ转变为鸟氨酸化血管紧张素-Ⅰ,或在磷酸二酯酶和碱性磷酸酶处理下水解为精氨酸核糖基化血管紧张素-Ⅰ,然后对上述2种衍生物进行基于CID碎裂模式的串联质谱分析. 结果表明,与未衍生的精氨酸-ADP-核糖基化血管紧张素-Ⅰ相比,在鸟氨酸化血管紧张素-Ⅰ和精氨酸核糖基化血管紧张素-Ⅰ的质谱图上发现大部分来自于肽骨架碎裂的离子峰,可提供足够的序列信息以确定精氨酸-ADP-核糖基化位点. 相似文献
58.
59.
Human peptidylarginine deiminases (hPADs) are a family of five calcium-dependent enzymes that facilitate citrullination, which is the post-translational modification of peptidyl arginine to peptidyl citrulline. The isozymes hPAD2 and hPAD4 have been implicated in the development and progression of several autoimmune diseases, including rheumatoid arthritis and multiple sclerosis. To better characterize the primary and secondary structure determinants of citrullination specificity, we mined the literature for protein sequences susceptible to citrullination by hPAD2 or hPAD4. First, protein secondary structure classification (α-helix, β-sheet, or coil) was predicted using the PSIPRED software. Next, we used motif-x and pLogo to extract and visualize statistically significant motifs within each data set. Within the data sets of peptides predicted to lie in coil regions, both hPAD2 and hPAD4 appear to favor citrullination of glycine-containing motifs, while distinct hydrophobic motifs were identified for hPAD2 citrullination sites predicted to reside within α-helical and β-sheet regions. Additionally, we identified potential substrate overlap between coil region citrullination and arginine methylation. Together, these results confirm the importance and offer some insight into the role of secondary structure elements for citrullination specificity, and provide biological context for the existing hPAD specificity and arginine post-translational modification literature. 相似文献
60.