Chemical and Biochemical Reference Data Division, National Institute of Standards and Technology, Gaithersburg, Maryland, USA.
J Am Soc Mass Spectrom. 2011 May;22(5):898-905. doi: 10.1007/s13361-011-0089-9. Epub 2011 Feb 25.
Bonds that break in collision-induced dissociation (CID) are often weakened by a nearby proton, which can, in principle, be carried away by either of the product fragments. Since peptide backbone dissociation is commonly charge-directed, relative intensities of charge states of product y- and b-ions depend on the final location of that proton. This study examines y-ion charge distributions for dissociation of doubly charged peptide ions, using a large reference library of peptide ion fragmentation generated from ion-trap CID of peptide ions from tryptic digests. Trends in relative intensities of y(2+) and y(1+) ions are examined as a function of bond cleavage position, peptide length (n), residues on either side of the bond and effects of residues remote from the bond. It is found that y(n-2)/b(2) dissociation is the most sensitive to adjacent amino acids, that y(2+)/y(1+) steadily increase with increasing peptide length, that the N-terminal amino acid can have a major influence in all dissociations, and in some cases other residues remote from the bond cleavage exert significant effects. Good correlation is found between the values of y(2+)/y(1+) for the peptide and the proton affinities of the amino acids present at the dissociating peptide bond. A few deviations from this correlation are rationalized by specific effects of the amino acid residues. These correlations can be used to estimate trends in y(2+)/y(1+) ratios for peptide ions from amino acid proton affinities.
在碰撞诱导解离（CID）中断裂的键通常会被附近的质子削弱，原则上，这个质子可以被产物碎片中的任意一个带走。由于肽键的解离通常是电荷导向的，因此产物 y-和 b-离子的电荷态相对强度取决于该质子的最终位置。本研究使用从胰蛋白酶消化的肽离子的离子阱 CID 生成的大型肽离子碎裂参考文库，检查了双电荷肽离子解离时 y-离子的电荷分布。研究了键断裂位置、肽长度（n）、键两侧的残基以及远离键的残基的影响与 y(2+)和 y(1+)离子相对强度之间的关系。结果发现，y(n-2)/b(2)解离对相邻氨基酸最敏感，y(2+)/y(1+)随肽长度的增加而稳定增加，N-末端氨基酸在所有解离中都有很大的影响，在某些情况下，远离键断裂的其他残基也会产生显著的影响。在肽中 y(2+)/y(1+)的值与在解离肽键处存在的氨基酸的质子亲和力之间存在良好的相关性。由于氨基酸残基的特定影响，这种相关性存在一些偏差。这些相关性可用于根据氨基酸质子亲和力估计肽离子中 y(2+)/y(1+)比值的趋势。
