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翻訳と辞書　辞書検索 [ 開発暫定版 ] スポンサード リンク Hydrogen–deuterium exchange ： ウィキペディア英語版 Hydrogen–deuterium exchange Hydrogen–deuterium exchange (also called H–D or H/D exchange) is a chemical reaction in which a covalently bonded hydrogen atom is replaced by a deuterium atom, or vice versa. Usually the examined protons are the amides in the backbone of a protein. The method gives information about the solvent accessibility of various parts of the molecule, and thus the tertiary structure of the protein. Hydrogen exchange was first shown and explored by Kaj Ulrik Linderstrøm-Lang. ==Exchange reaction== In solution, amide hydrogens in the peptide bonds of proteins exchange protons with the solvent. By changing the solvent from H2O to D2O, deuterons will be incorporated in the amide positions and the exchange reaction can be followed. Most often, deuterium is added to a protein in H2O by diluting the H2O solution with D2O (e.g. tenfold). Usually exchange is performed at physiological pH (7.0–8.0) where proteins are in their most native ensemble of conformational states. See also . Because the exchange reaction can be either acid or base catalyzed, it is strongly pH dependent. For the backbone amide hydrogens, the minimum exchange rate occurs at approximately pH 2.6, on average. By performing the exchange at neutral pH and then rapidly changing the pH, the exchange rates of the backbone amide hydrogens can be dramatically slowed, or quenched. The pH at which the reaction is quenched depends on the analysis method. For detection by NMR, the pH may be moved to around 4.0–4.5. For detection by mass spectrometry, the pH is dropped to the minimum of the exchange curve, pH 2.6. In the most basic experiment, the reaction is allowed to take place for a set time before it is quenched. The deuteration pattern of a quenched protein can be stably maintained in aprotic environments. However, analysis of the deuteration is usually performed in an aqueous solution, which means that exchange will continue at a slow rate even after the reaction is quenched. Reversion of deuterated positions after the quench step is referred to as ''back-exchange'' and various methods have been devised to correct for this. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Hydrogen–deuterium exchange」の詳細全文を読む スポンサード リンク 翻訳と辞書 : 翻訳のためのインターネットリソース Copyright(C) kotoba.ne.jp 1997-2016. All Rights Reserved.