Harrison Alex G
Department of Chemistry, University of Toronto, Toronto, ON, Canada.
Mass Spectrom Rev. 2009 Jul-Aug;28(4):640-54. doi: 10.1002/mas.20228.
Modern soft ionization techniques readily produce protonated or multiply protonated peptides. Collision-induced dissociation (CID) of these protonated species is often used as a method to obtain sequence information. In many cases fragmentation occurs at amide bonds. When the charge resides on the C-terminal fragment so-called y ions are produced which are known to be protonated amino acids or truncated peptides. When the charge resides on the N-terminal fragment so-called b ions are produced. Often the sequence of y and b ions are essential for peptide sequencing. The b ions have many possible structures, a knowledge of which is useful in this sequencing. The structures of b ions are reviewed in the following with particular emphasis on the variation of structure with the number of amino acid residues in the b ion and the effect of peptide side chain on b ion structure. The recent discovery of full cyclization of larger b ions results in challenges in peptide sequencing. This aspect is discussed in detail.
现代软电离技术很容易产生质子化或多质子化的肽段。这些质子化物种的碰撞诱导解离（CID）常被用作获取序列信息的方法。在许多情况下，酰胺键处会发生断裂。当电荷位于C端片段时，会产生所谓的y离子，已知其为质子化氨基酸或截短的肽段。当电荷位于N端片段时，会产生所谓的b离子。通常，y离子和b离子的序列对于肽段测序至关重要。b离子有许多可能的结构，了解这些结构在这种测序中很有用。以下将对b离子的结构进行综述，特别强调b离子结构随氨基酸残基数目的变化以及肽侧链对b离子结构的影响。最近发现较大的b离子会完全环化，这给肽段测序带来了挑战。将详细讨论这一方面。
