Herrmann Kristin A, Kuppannan Krishna, Wysocki Vicki H
University of Arizona, Department of Chemistry, 1306 E. University Blvd., Tucson, AZ 85721-0041, USA.
Int J Mass Spectrom. 2006(249-250):93-105. doi: 10.1016/j.ijms.2005.12.047.
Doubly-protonated bradykinin (RPPGFSPFR) and an angiotensin III analogue (RVYIFPF) were subjected to hydrogen/deuterium (H/D) exchange with CD(3)OD in a Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer. A bimodal distribution of deuterium incorporation was present for bradykinin after H/D exchange for 90 s at a CD(3)OD pressure of 4 x 10(-7) Torr, indicating the existence of at least two distinct populations. Bradykinin ion populations corresponding to 0-2 and 5-11 deuteriums (i.e., D(0), D(1), D(2), D(5), D(6), D(7), D(8), D(9), D(10), and D(11)) were each monoisotopically selected and fragmented via sustained off-resonance irradiation (SORI) collision-induced dissociation (CID). The D(0)-D(2) ion populations, which correspond to the slower exchanging population, consistently require lower SORI amplitude to achieve a similar precursor ion survival yield as the faster-reacting (D(5)-D(11)) populations. These results demonstrate that conformation/protonation motif has an effect on fragmentation efficiency for bradykinin. Also, the partitioning of the deuterium atoms into fragment ions suggests that the C-terminal arginine residue exchanges more rapidly than the N-terminal arginine. Total deuterium incorporation in the b(1)/y(8) and b(2)/y(7) ion pairs matches very closely the theoretical values for all ion populations studied, indicating that the ions of a complementary pair are likely formed during the same fragmentation event, or that no scrambling occurs upon SORI. Deuterium incorporation into the y(1)/a(8) pseudo-ion pair does not closely match the expected theoretical values. The other peptide, doubly-protonated RVYIFPF, has a trimodal distribution of deuterium incorporation upon H/D exchange with CD(3)OD at a pressure of 1 x 10(-7) Torr for 600 s, indicating at least three distinct ion populations. After 90 s of H/D exchange where at least two distinct populations are detected, the D(0)-D(7) ion populations were monoisotopically selected and fragmented via SORI-CID over a range of SORI amplitudes. The precursor ion survival yield as a function of SORI amplitude falls into two distinct behaviors corresponding to slower- and faster-reacting ion populations. The slower-reacting population requires larger SORI amplitudes to achieve the same precursor ion survival yield as the faster exchanging population. Total deuterium incorporation into the y(2)/b(5) ion pairs matches closely the theoretical values over all ion populations and SORI amplitudes studied. This result indicates the y(2) and b(5) ions are likely formed by the same mechanism over the SORI amplitudes studied.
将双质子化的缓激肽（RPPGFSPFR）和一种血管紧张素III类似物（RVYIFPF）置于傅里叶变换离子回旋共振（FT-ICR）质谱仪中，与CD(3)OD进行氢/氘（H/D）交换。在4×10(-7)托的CD(3)OD压力下进行90秒的H/D交换后，缓激肽的氘掺入呈现双峰分布，表明至少存在两个不同的群体。分别对对应于0 - 2个和5 - 11个氘（即D(0)、D(1)、D(2)、D(5)、D(6)、D(7)、D(8)、D(9)、D(10)和D(11)）的缓激肽离子群体进行单同位素选择，并通过持续非共振照射（SORI）碰撞诱导解离（CID）进行裂解。对应于交换较慢群体的D(0) - D(2)离子群体，与反应较快的（D(5) - D(11)）群体相比，始终需要较低的SORI振幅才能实现相似的前体离子存活产率。这些结果表明，构象/质子化基序对缓激肽的裂解效率有影响。此外，氘原子在碎片离子中的分配表明，C末端精氨酸残基的交换比N末端精氨酸更快。在所有研究的离子群体中，b(1)/y(8)和b(2)/y(7)离子对中的总氘掺入与理论值非常接近，这表明互补对离子可能在同一裂解事件中形成，或者在SORI过程中没有发生重排。氘掺入y(1)/a(8)假离子对的情况与预期理论值不太匹配。另一种肽，双质子化的RVYIFPF，在1×10(-7)托的压力下与CD(3)OD进行600秒的H/D交换后，氘掺入呈现三峰分布，表明至少存在三个不同的离子群体。在检测到至少两个不同群体的90秒H/D交换后，对D(0) - D(7)离子群体进行单同位素选择，并在一系列SORI振幅范围内通过SORI-CID进行裂解。前体离子存活产率作为SORI振幅的函数呈现出两种不同的行为，分别对应于反应较慢和较快的离子群体。反应较慢的群体需要更大的SORI振幅才能达到与交换较快群体相同的前体离子存活产率。在所有研究的离子群体和SORI振幅中，y(2)/b(5)离子对中的总氘掺入与理论值密切匹配。这一结果表明，在所研究的SORI振幅范围内，y(2)和b(5)离子可能通过相同的机制形成。
