Newton Kelly A, Amunugama Ravi, McLuckey Scott A
Department of Chemistry, Purdue University, West Lafayette, IN 47907-2084, USA.
J Phys Chem A. 2005 Apr 28;109(16):3608-16. doi: 10.1021/jp044106i.
Gas-phase reactions of multiply protonated polypeptides and metal containing anions represent a new methodology for manipulating the cationizing agent composition of polypeptides. This approach affords greater flexibility in forming metal containing ions than commonly used methods, such as electrospray ionization of a metal salt/peptide mixture and matrix-assisted laser desorption. Here, the effects of properties of the polypeptide and anionic reactant on the nature of the reaction products are investigated. For a given metal, the identity of the ligand in the metal containing anion is the dominant factor in determining product distributions. For a given polypeptide ion, the difference between the metal ion affinity and the proton affinity of the negatively charged ligand in the anionic reactant is of predictive value in anticipating the relative contributions of proton transfer and metal ion transfer. Furthermore, the binding strength of the ligand anion to charge sites in the polypeptide correlates with the extent of observed cluster ion formation. Polypeptide composition, sequence, and charge state can also play a notable role in determining the distribution of products. In addition to their usefulness in gas-phase ion synthesis strategies, the reactions of protonated polypeptides and metal containing anions represent an example of a gas-phase ion/ion reaction that is sensitive to polypeptide structure. These observations are noteworthy in that they allude to the possibility of obtaining information, without requiring fragmentation of the peptide backbone, about ion structure as well as the relative ion affinities associated with the reactants.
多质子化多肽与含金属阴离子的气相反应代表了一种操纵多肽阳离子化剂组成的新方法。与常用方法（如金属盐/肽混合物的电喷雾电离和基质辅助激光解吸）相比，这种方法在形成含金属离子方面具有更大的灵活性。在此，研究了多肽和阴离子反应物的性质对反应产物性质的影响。对于给定的金属，含金属阴离子中配体的身份是决定产物分布的主要因素。对于给定的多肽离子，阴离子反应物中带负电荷配体的金属离子亲和力与质子亲和力之间的差异对于预测质子转移和金属离子转移的相对贡献具有参考价值。此外，配体阴离子与多肽中电荷位点的结合强度与观察到的簇离子形成程度相关。多肽的组成、序列和电荷状态在决定产物分布方面也可发挥显著作用。除了在气相离子合成策略中的有用性外，质子化多肽与含金属阴离子的反应代表了一种对多肽结构敏感的气相离子/离子反应实例。这些观察结果值得注意，因为它们暗示了在不需要肽主链断裂的情况下获得有关离子结构以及与反应物相关的相对离子亲和力信息的可能性。
