Laskin Julia, Yang Zhibo, Chu Ivan K
Pacific Northwest National Laboratory, Fundamental Sciences Division, Richland, Washington, USA.
J Am Chem Soc. 2008 Mar 12;130(10):3218-30. doi: 10.1021/ja077690s. Epub 2008 Feb 12.
Time- and collision energy-resolved surface-induced dissociation (SID) of ternary complexes of Co(III)(salen)+, Fe(III)(salen)+, and Mn(III)(salen)+ with several angiotensin peptide analogues was studied using a Fourier transform ion cyclotron resonance mass spectrometer (FT-ICR MS) specially equipped to perform SID experiments. Time-resolved fragmentation efficiency curves (TFECs) were modeled using an RRKM-based approach developed in our laboratory. The approach utilizes a very flexible analytical expression for the internal energy deposition function that is capable of reproducing both single-collision and multiple-collision activation in the gas phase and excitation by collisions with a surface. The energetics and dynamics of competing dissociation pathways obtained from the modeling provides important insight on the competition between proton transfer, electron transfer, loss of neutral peptide ligand, and other processes that determine gas-phase fragmentation of these model systems. Similar fragmentation behavior was obtained for various Co(III)(salen)-peptide systems of different angiotensin analogues. In contrast, dissociation pathways and relative stabilities of the complexes changed dramatically when cobalt was replaced with trivalent iron or manganese. We demonstrate that the electron-transfer efficiency is correlated with redox properties of the metal(III)(salen) complexes (Co > Fe > Mn), while differences in the types of fragments formed from the complexes reflect differences in the modes of binding between the metal-salen complex and the peptide ligand. RRKM modeling of time- and collision-energy-resolved SID data suggests that the competition between proton transfer and electron transfer during dissociation of Co(III)(salen)-peptide complexes is mainly determined by differences in entropy effects while the energetics of these two pathways are very similar.
使用专门配备用于进行表面诱导解离（SID）实验的傅里叶变换离子回旋共振质谱仪（FT-ICR MS），研究了Co(III)(salen)+、Fe(III)(salen)+和Mn(III)(salen)+与几种血管紧张素肽类似物的三元复合物的时间分辨和碰撞能量分辨表面诱导解离（SID）。时间分辨碎裂效率曲线（TFECs）采用我们实验室开发的基于RRKM的方法进行建模。该方法对内能沉积函数采用了非常灵活的解析表达式，能够再现气相中的单碰撞和多碰撞活化以及与表面碰撞激发。从建模中获得的竞争解离途径的能量学和动力学为质子转移、电子转移、中性肽配体损失以及其他决定这些模型系统气相碎裂的过程之间的竞争提供了重要见解。不同血管紧张素类似物的各种Co(III)(salen)-肽系统获得了相似的碎裂行为。相比之下，当钴被三价铁或锰取代时，复合物的解离途径和相对稳定性发生了显著变化。我们证明电子转移效率与金属（III）（salen）配合物的氧化还原性质相关（Co > Fe > Mn），而复合物形成的碎片类型差异反映了金属-salen配合物与肽配体之间结合模式的差异。对时间分辨和碰撞能量分辨的SID数据进行RRKM建模表明，Co(III)(salen)-肽复合物解离过程中质子转移和电子转移之间的竞争主要由熵效应的差异决定，而这两种途径的能量学非常相似。
