[<i>N</i><sup>ε</sup>-(γ-glutamyl) lysine] as a potential biomarker in neurological diseases : New detection method and fragmentation pathways
作者:Guylaine Hoffner、Yannik Hoppilliard、Guillaume van der Rest、Patrick Dansette、Philippe Djian、Gilles Ohanessian
DOI:10.1002/jms.1331
日期:2008.4
shown to be adequate markers for quantitation experiments. In order to gain a better understanding of the fragmentation processes, detailed quantumchemical calculations have been performed at levels which are expected to provide good accuracy. A thorough study has been carried out with a reduced model in which only the 'active' part of the molecule is retained. This allowed obtaining full mechanistic
蛋白质聚集体是许多中枢神经系统疾病(例如polyQ扩张疾病)的特征。通过转谷氨酰胺酶的作用形成的共价键被认为参与了这些聚集体的稳定化。转谷氨酰胺酶催化在谷氨酰胺基和多肽的赖氨酰残基的侧链之间形成交联。在神经元聚集体的最终蛋白水解消化物中,对异肽N(ε)-(γ-谷氨酰基)赖氨酸(iEK)的鉴定将证明转谷氨酰胺酶参与了神经系统疾病。为了鉴定和量化神经系统疾病患者的大脑中存在的iEK,开发了一种结合液相色谱和多步质谱的方法。由于聚集蛋白的消化物中可能存在iEK的等压肽,因此片段诊断离子的选择至关重要。这些离子是通过在iEK上进行质谱鉴定而确定的,该iEK在羧基官能团和末端胺上进行了衍生化以提高灵敏度。氘代分子以及(13)C(6)-和(15)N(2)-同位素异构体用于在多步裂解中衍生纤丝。已经鉴定出主要的碎片模式,因此显示出两个离子(m / z 396 [MH-56-42 u](+)和350 [MH-56-88
Modelling of prebiotic synthesis and selection of peptides under isothermal conditions and thermal cycling mode
作者:O. V. Demina、A. S. Kononikhin、A. V. Laptev、A. A. Khodonov、E. N. Nikolaev、S. D. Varfolomeev
DOI:10.1007/s11172-012-0060-3
日期:2012.2
The model peptide synthesis from mixtures of amino acids was carried out under the thermal cycling and isothermal modes. The compositions of the obtained mixtures of products and the primary amino acid sequence of the synthesized peptides were determined by Fouriertransformioncyclotronresonancemassspectrometry and tandem massspectrometry in combination with high-performance liquid chromatography
A novel enzyme that catalyzes the efficient hydrolysis of Glu-Glu was isolated from soybean cotyledons by ammonium sulfate fractionation and successive column chromatographies of Q-sepharose, Phenyl sepharose, and Superdex 200. The apparent molecular mass of this enzyme was found to be 56 kDa and 510 kDa by SDS-polyacrylamide gel electrophoresis and Superdex 200 HR 10/30 column chromatography respectively. The enzyme had high activity against Glu-p-nitroanilide (pNA) and Asp-pNA, whereas Leu-pNA, Phe-pNA, Ala-pNA, and Pro-pNA were not hydrolyzed. The synthetic dipeptides Glu-Xxx and Asp-Xxx were hydrolyzed, but Xxx-Glu was not. The digestion of a Glu-rich oligopeptide, chromogranin A (Glu-Glu-Glu-Glu-Glu-Met-Ala-Val-Val-Pro-Gln-Gly-Leu-Phe-Arg-Gly-NH2) using this purified enzyme was also investigated. Glutamic acid residues were cleaved one by one from the N-terminus. These observations indicate that the enzyme removes glutamyl or aspartyl residues from N-terminal acidic amino acid-containing peptides. It is thought that it was an N-terminal acidic amino acid-specific aminopeptidase from a plant.