Loo J A, Loo R R, Udseth H R, Edmonds C G, Smith R D
Chemical Sciences Department, Pacific Northwest Laboratory, Richland, WA 99532.
Rapid Commun Mass Spectrom. 1991 Mar;5(3):101-5. doi: 10.1002/rcm.1290050303.
Electrospray-ionization (ESI) mass spectrometry is used to monitor higher order structural changes of polypeptides induced by alteration of the pH or organic solvent composition in the protein solution environment. A bimodal charge-state distribution is observed in the ESI mass spectrum of ubiquitin (relative molecular mass 8565) in solutions containing small amounts (less than 20%) of organic solvents. The distribution of peaks at high m/z (low-charge state) is found to represent the protein in its native, globular state; the higher-charge-state distribution is characteristic for a more extended conformation. Addition of methanol denaturant in excess of 40% v/v is needed to eliminate the low-charge-state distribution completely. Lesser amounts of acetonitrile, acetone, or isopropanol (approximately 20%) are required to denature the ubiquitin protein. Other proteins showing conformational effects in their ESI mass spectra are also illustrated. While the ESI spectra are related to solution phase structure, ESI-tandem mass spectrometry of multiply charged molecular ions of different conformation is suggested as a probe of gas-phase protein three-dimensional structure.
电喷雾电离（ESI）质谱用于监测在蛋白质溶液环境中，pH值或有机溶剂组成的改变所诱导的多肽高阶结构变化。在含有少量（小于20%）有机溶剂的溶液中，泛素（相对分子质量8565）的ESI质谱中观察到双峰电荷态分布。发现高m/z（低电荷态）处的峰分布代表处于天然球状状态的蛋白质；较高电荷态分布是更伸展构象的特征。需要添加超过40% v/v的甲醇变性剂才能完全消除低电荷态分布。使泛素蛋白变性需要较少的乙腈、丙酮或异丙醇（约20%）。还展示了其他在ESI质谱中显示构象效应的蛋白质。虽然ESI光谱与溶液相结构有关，但不同构象的多电荷分子离子的ESI串联质谱被认为是气相蛋白质三维结构的一种探测手段。
