Mentinova Marija, Han Hongling, McLuckey Scott A
Department of Chemistry, Purdue University, West Lafayette, IN 47907-2084, USA.
Rapid Commun Mass Spectrom. 2009 Sep;23(17):2647-55. doi: 10.1002/rcm.4172.
The dissociation chemistry of somatostatin-14 was examined using various tandem mass spectrometry techniques including low-energy beam-type and ion trap collision-induced dissociation (CID) of protonated and deprotonated forms of the peptide, CID of peptide-gold complexes, and electron transfer dissociation (ETD) of cations. Most of the sequence of somatostatin-14 is present within a loop defined by the disulfide linkage between Cys-3 and Cys-14. The generation of readily interpretable sequence-related ions from within the loop requires the cleavage of at least one of the bonds of the disulfide linkage and the cleavage of one polypeptide backbone bond. CID of the protonated forms of somatostatin did not appear to give rise to an appreciable degree of dissociation of the disulfide linkage. Sequential fragmentation via multiple alternative pathways tended to generate very complex spectra. CID of the anions proceeded through CH(2)-S cleavages extensively but relatively few structurally diagnostic ions were generated. The incorporation of Au(I) into the molecule via ion/ion reactions followed by CID gave rise to many structurally relevant dissociation products, particularly for the M+Au+H species. The products were generated by a combination of S-S bond cleavage and amide bond cleavage. ETD of the M+3H ion generated rich sequence information, as did CID of the electron transfer products that did not fragment directly upon electron transfer. The electron transfer results suggest that both the S-S bond and an N-C(alpha) bond can be cleaved following a single electron transfer reaction.
利用各种串联质谱技术研究了生长抑素-14的解离化学，这些技术包括低能束型和离子阱碰撞诱导解离（CID），用于该肽质子化和去质子化形式、肽-金络合物的CID以及阳离子的电子转移解离（ETD）。生长抑素-14的大部分序列存在于由Cys-3和Cys-14之间的二硫键定义的环内。要从环内产生易于解释的与序列相关的离子，需要切断二硫键的至少一个键和一个多肽主链键。生长抑素质子化形式的CID似乎并未导致二硫键发生明显程度的解离。通过多种替代途径的顺序碎片化往往会产生非常复杂的光谱。阴离子的CID广泛通过CH(2)-S裂解进行，但产生的结构诊断离子相对较少。通过离子/离子反应将Au(I)掺入分子中，随后进行CID，产生了许多与结构相关的解离产物，特别是对于M+Au+H物种。这些产物是通过S-S键裂解和酰胺键裂解的组合产生的。M+3H离子的ETD产生了丰富的序列信息，电子转移产物的CID也是如此，这些产物在电子转移时不会直接碎片化。电子转移结果表明，在单次电子转移反应后，S-S键和N-C(α)键都可以被切断。
