Guan Z, Hofstadler S A, Laude D A
Department of Chemistry and Biochemistry, University of Texas, Austin 78712.
Anal Chem. 1993 Jun 1;65(11):1588-93. doi: 10.1021/ac00059a018.
A single population of multiply charged protein ions formed by electrospray ionization (ESI) is subjected to multiple Fourier transform ion cyclotron resonance (FTICR) excitation and detection events without promoting ion loss from the trapped ion cell. This nondestructive approach to mass spectrometric detection will allow detection limits to be significantly reduced by averaging the repetitive time-domain response that follows each excitation event. Under appropriate conditions, unit remeasurement efficiency is observed for large proteins; for example, 250 consecutive remeasurements of a single population of bovine albumin dimer ions (MW 132,532) yield the expected 16-fold improvement in signal-to-noise ratio compared to a single measurement. Examples presented include a 14-fmol sample of horse myoglobin (MW 16,951), which yields a 15:1 S/N for 50 remeasurements compared to a single scan S/N of 2:1 and a 30-fmol sample of bovine albumin dimer which exhibits a S/N of 25:1 for 50 remeasurements compared to a single scan S/N of 3:1. Of both practical and theoretical interest is the observation of a rapid collision-mediated homogeneous relaxation process that can return these large ions to the center of the cell within a few hundred milliseconds after excitation.
通过电喷雾电离（ESI）形成的单一组多重带电蛋白质离子群体，在不促使离子从捕获离子池中损失的情况下，经历多次傅里叶变换离子回旋共振（FTICR）激发和检测事件。这种用于质谱检测的非破坏性方法，通过对每次激发事件后的重复时域响应求平均值，将显著降低检测限。在适当条件下，对于大分子蛋白质可观察到单位重测效率；例如，对单一组牛血清白蛋白二聚体离子（分子量132,532）进行250次连续重测，与单次测量相比，信噪比提高了预期的16倍。给出的例子包括14飞摩尔的马肌红蛋白（分子量16,951）样品，50次重测时信噪比为15:1，单次扫描信噪比为2:1；以及30飞摩尔的牛血清白蛋白二聚体样品，50次重测时信噪比为25:1，单次扫描信噪比为3:1。一个具有实际和理论意义的观察结果是，存在一种快速的碰撞介导的均匀弛豫过程，该过程可在激发后几百毫秒内使这些大分子离子回到离子池中心。
