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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >A fast flow tube study of gas phase H/D exchange of multiply protonated ubiquitin
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A fast flow tube study of gas phase H/D exchange of multiply protonated ubiquitin

机译：快速流管研究多质子化泛素的气相H / D交换

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An electrospray ionization (ESI)/fast-flow technique has been applied to the study of gas phase hydrogen/deuterium (H/D) exchange kinetics. Multiply charged ubiquitin ions [ubiquitin + nH](n+), in charge states n = 7-13, were reacted with ND3. The behavior of ND3 as exchange reagent is different from that of the previously studied reagents, D2O and CH3OD. Contrary to those, the maximum number of exchanged hydrogen atoms and the overall exchange rate were observed to increase with increasing charge state of the ubiquitin ions. The results are reagent-dependent because the exchange mechanisms are different for the different reagents. This observation is in agreement with a recent conclusion by Beauchamp and co-workers that contrary to the assumption often expressed in earlier studies, H/D exchange kinetics may not directly reflect ion structures. The results for all three reagents are, however, consistent with observations of previous ion mobility experiments that with increasing charge state the conformers change from more compact, partially folded structures to elongated nearly linear ones. H/D exchange of (ubiquitin + 13H) (13+) with ND3 leads to two separated ion populations reflecting the possible existence of two conformers with different exchange rates. The ions (ubiquitin + 8H)(8+) and (ubiquitin + 11H)(11+) represent a partially folded structure and an unfolded structure, respectively, and were studied in greater detail. The relative abundances of ions were measured in steps of 0.5 m/z (mass-to-charge ratio), as a function of the ND3 flow rate. The experimental results were simulated by computer fitted curves based on a recently developed algorithm. The algorithm allows the extraction of sets of grouped rate constants. Eight rate constant groups were deduced for each of the two ions. These rate constants correspond to 32 and 44 H/D exchanges for the 8+ and 11+ charged ions, respectively. The results indicate higher individual rates for most of the exchanged atoms in the 11+, ion compared to the 8+ ion.
机译：电喷雾电离（ESI）/快速流动技术已应用于气相氢/氘（H / D）交换动力学的研究。电荷状态n = 7-13的带电荷的泛素离子[泛素+ nH]（n +）与ND3反应。 ND3作为交换试剂的行为与之前研究的D2O和CH3OD试剂不同。与之相反，观察到最大交换氢原子数和总交换率随泛素离子电荷状态的增加而增加。结果取决于试剂，因为不同试剂的交换机制不同。这项观察结果与Beauchamp及其同事的最新结论一致，即与先前研究中经常表达的假设相反，H / D交换动力学可能无法直接反映离子结构。但是，所有三种试剂的结果与先前离子迁移实验的观察结果一致，即随着电荷状态的增加，构象异构体将从更紧凑的部分折叠的结构变为几乎线性的细长结构。 （泛素+ 13H）（13+）与ND3的H / D交换导致两个分离的离子群，反映了可能存在具有不同交换速率的两个构象体。离子（泛素+ 8H）（8+）和（泛素+ 11H）（11+）分别代表部分折叠的结构和未折叠的结构，并进行了更详细的研究。根据ND3流速的函数，以0.5 m / z（质荷比）为步长测量离子的相对丰度。通过基于最近开发的算法的计算机拟合曲线对实验结果进行了仿真。该算法允许提取成组的速率常数集。推导了两个离子中的每一个的八个速率常数组。这些速率常数分别对应于8+和11+带电离子的32和44 H / D交换。结果表明，与8+离子相比，11+离子中大多数交换原子的单个速率更高。

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