Negative ion mass spectra of Cys-containing peptides. The characteristic Cys gamma backbone cleavage: a joint experimental and theoretical study.
Negative ion mass spectra of Cys-containing peptides. The characteristic Cys gamma backbone cleavage: a joint experimental and theoretical study.
复制标题
含半胱氨酸肽的负离子质谱。
DOI：
10.1002/rcm.1360
复制
发表时间：
2004
期刊：
影响因子：
--
通讯作者：
J. Bowie
中科院分区：
文献类型：
--
作者：
D. Bilusich;C. Brinkworth;J. Bowie
Cys残基引发含Cys肽的[M-H]（-）阴离子的特征性骨干断裂。实验和理论的结合表明，这些过程是由c端CONH（-）基团（在本研究中，所有肽都有c端CONH(2)基团）和Cys侧链上的SH之间的分子识别引发的，从而形成S-H…O=C氢键。这个过程是60 kJ mol（-1）的放热过程（在HF/6-31G(d)//AM1理论水平上计算）。这种反应中间体的结构具有酰胺基团的NH（-）和Cys残基的中心CH锁定在一定位置，使得这些基团影响S(N)2过程形成中间体，该中间体可以(i)解离产生RNH（-）种[δ离子(吸热37 kJ mol(-1)，势垒为132 kJ mol(-1))]；或（ii）在中间体中作用去质子化以消除RNH(2)，使γ骨干裂解阴离子在放热反应中释放40 kJ mol(-1)，势垒为132 kJ mol（-1）。5种含cys肽的[M-H]（-）阴离子的碰撞诱导质谱均含有γ和（γ - h (2)S）阴离子。其中三个光谱也显示出较不受欢迎的δ解理阴离子。
The Cys residue initiates characteristic backbone cleavages of [M-H](-) anions of Cys-containing peptides. A combination of experiment and theory suggests that these processes are initiated by molecular recognition between the C-terminal CONH(-) group (in this study all peptides have C-terminal CONH(2) groups) and the SH in the Cys side chain to form an S-H...O=C hydrogen bond. This process is exothermic by 60 kJ mol(-1) (calculations at the HF/6-31G(d)//AM1 level of theory). The structure of this reactive intermediate has the NH(-) of the amide group and the central CH of the Cys residue locked into position such that these groups effect an S(N)2 process to form an intermediate which can either (i) dissociate to give an RNH(-) species [the delta ion (process endothermic by 37 kJ mol(-1) with a barrier of 132 kJ mol(-1))], or (ii) effect deprotonation within the intermediate to eliminate RNH(2) to give the gamma backbone cleavage anion in a reaction exothermic by 40 kJ mol(-1) with a barrier of 132 kJ mol(-1). Collision-induced mass spectra of the [M-H](-) anions of five selected Cys-containing peptides all contain gamma and (gamma-H(2)S) anions. Three of these spectra also show the less favoured delta cleavage anions.