Fundamental Sciences Division, Pacific Northwest National Laboratory, Richland, Washington 99352, United States.
J Am Chem Soc. 2010 Nov 17;132(45):16006-16. doi: 10.1021/ja104438z. Epub 2010 Oct 26.
The effect of the basic residue on the energetics, dynamics, and mechanisms of backbone fragmentation of protonated peptides was investigated. Time-resolved and collision energy-resolved surface-induced dissociation (SID) of singly protonated peptides with the N-terminal arginine residue and their analogues, in which arginine is replaced with less basic lysine and histidine residues, was examined using a specially configured Fourier transform ion cyclotron resonance mass spectrometer (FTICR-MS). SID experiments demonstrated different kinetics of formation of several primary product ions of peptides with and without arginine residue. The energetics and dynamics of these pathways were determined from Rice-Ramsperger-Kassel-Marcus (RRKM) modeling of the experimental data. Comparison between the kinetics and energetics of fragmentation of arginine-containing peptides and the corresponding methyl ester derivatives provides important information on the effect of dissociation pathways involving salt bridge (SB) intermediates on the observed fragmentation behavior. Because pathways involving SB intermediates are characterized by low threshold energies, they efficiently compete with classical oxazolone and imine/enol pathways of arginine-containing peptides on a long time scale of the FTICR instrument. In contrast, fragmentation of histidine- and lysine-containing peptides is largely determined by canonical pathways. Because SB pathways are characterized by negative activation entropies, fragmentation of arginine-containing peptides is kinetically hindered and observed at higher collision energies as compared to their lysine- and histidine-containing analogues.
研究了碱性残基对质子化肽的骨架断裂的能量学、动力学和机制的影响。使用特殊配置的傅里叶变换离子回旋共振质谱仪（FTICR-MS），研究了具有和不具有 N 末端精氨酸残基的单质子化肽及其类似物（其中精氨酸被碱性较弱的赖氨酸和组氨酸残基取代）的时间分辨和碰撞能分辨的表面诱导解离（SID）。SID 实验表明，具有和不具有精氨酸残基的肽的几种初级产物离子的形成具有不同的动力学。这些途径的能量学和动力学是通过 Rice-Ramsperger-Kassel-Marcus（RRKM）对实验数据的建模来确定的。对含精氨酸肽和相应的甲酯衍生物的碎裂动力学和能量学进行比较，提供了关于涉及盐桥（SB）中间体的解离途径对观察到的碎裂行为的影响的重要信息。由于涉及 SB 中间体的途径的特征是低阈值能量，因此它们在 FTICR 仪器的长时间尺度上与含精氨酸肽的经典恶唑酮和亚胺/烯醇途径有效地竞争。相比之下，含组氨酸和赖氨酸的肽的断裂主要由经典途径决定。由于 SB 途径的特征是负活化熵，因此与含赖氨酸和组氨酸的类似物相比，含精氨酸的肽的断裂在动力学上受到阻碍，并且在较高的碰撞能下观察到。
