The use of chromium(III) to supercharge peptides by protonation at low basicity sites.
The use of chromium(III) to supercharge peptides by protonation at low basicity sites.
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DOI：
10.1007/s13361-014-1020-y
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发表时间：
2015-02
影响因子：
3.2
通讯作者：
Cassady, Carolyn J.
中科院分区：
文献类型：
--
作者：
Feng, Changgeng;Commodore, Juliette J.;Cassady, Carolyn J.
在含有7个或更多残基的多肽溶液中加入硝酸铬极大地增加了通过电喷雾电离形成双质子化多肽[M+2H]2+的能力。测试化合物七丙氨酸只有一个高度碱性的位置(N-末端氨基)，并且在标准溶剂中几乎是唯一的单一质子化反应。当将铬(III)加入到溶液中时，会生成大量的[M+2H]2+，这涉及到肽骨架或C-末端的质子化。还研究了Al(III)、Mn(II)、Fe(III)、Fe(II)、Cu(II)、Zn(II)、Rh(III)、La(III)、Ce(IV)和Eu(III)的盐类。虽然几种金属离子对质子化有轻微的促进作用，但目前为止，铬(III)产生[M+2H]2+的能力最强。铬(III)不对多肽甲酯进行增压，这表明其机理与铬(III)与羧酸基的相互作用有关。其他因素可能包括六水合铬(III)的高酸性和铬(III)对还原的抵抗力。硝酸盐对质子化的促进作用强于氯盐，当物质的量比为10：1时，[M+2H]2+的生成强度最大。铬(III)还增加了许多其他小肽，包括高酸性物种。对于碱性多肽，铬(III)增加了电荷状态(2+对1+)，并使被质子化的多肽分子的数量增加了一倍或三倍。铬(III)不会增加细胞色素c和肌红蛋白的含量。由于[M+2H]2+通常比[M+H]+更容易解离，以及产生用于基于电子的解离技术的[M+2H]2+前体的能力，铬(III)增强[M+2H]2+强度的能力在串联质谱学中可能被证明是有用的。
The addition of chromium(III) nitrate to solutions of peptides with seven or more residues greatly increases the formation of doubly protonated peptides, [M+2H]2+, by electrospray ionization. The test compound heptaalanine has only one highly basic site (the N-terminal amino group) and undergoes almost exclusive single protonation using standard solvents. When Cr(III) is added to the solution, abundant [M+2H]2+ forms, which involves protonation of the peptide backbone or the C-terminus. Salts of Al(III), Mn(II), Fe(III), Fe(II), Cu(II), Zn (II), Rh(III), La(III), Ce(IV), and Eu(III) were also studied. While several metal ions slightly enhance protonation, Cr(III) has by far the greatest ability to generate [M+2H]2+. Cr(III) does not supercharge peptide methyl esters, which suggests that the mechanism involves interaction of Cr(III) with a carboxylic acid group. Other factors may include the high acidity of hexaaquochromium(III) and the resistance of Cr(III) to reduction. Nitrate salts enhance protonation more than chloride salts and a molar ratio of 10:1 Cr(III):peptide produces the most intense [M+2H]2+. Cr(III) also supercharges numerous other small peptides, including highly acidic species. For basic peptides, Cr(III) increases the charge state (2+ versus 1+) and causes the number of peptide molecules being protonated to double or triple. Chromium(III) does not supercharge the proteins cytochrome c and myoglobin. The ability of Cr(III) to enhance [M+2H]2+ intensity may prove useful in tandem mass spectrometry because of the resulting overall increase in signal-to-noise ratio, the fact that [M+2H]2+ generally dissociate more readily than [M+H]+, and the ability to produce [M+2H]2+ precursors for electron-based dissociation techniques.
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DOI：
10.1007/s13361-011-0319-1
发表时间：
2012-03-01
影响因子：
3.2
作者：
Douglass, Kevin Aart;Venter, Andre R.
通讯作者：
Venter, Andre R.
影响因子：
2.9
作者：
Davis, CM;Vincent, JB
通讯作者：
Vincent, JB
影响因子：
3.9
作者：
Davis, CM;Vincent, JB
通讯作者：
Vincent, JB
影响因子：
7.4
作者：
Cassou, Catherine A.;Sterling, Harry J.;Susa, Anna C.;Williams, Evan R.
通讯作者：
Williams, Evan R.
影响因子：
3.3
作者：
Bokatzian-Johnson, Samantha S.;Stover, Michele L.;Cassady, Carolyn J.
通讯作者：
Cassady, Carolyn J.