Shimadzu Research Laboratory (Europe) Ltd., Manchester M17 1GP, U.K.
School of Material Science and Chemical Engineering, Ningbo University, Ningbo, Zhejiang 315211, China.
J Am Soc Mass Spectrom. 2021 May 5;32(5):1145-1154. doi: 10.1021/jasms.0c00445. Epub 2021 Apr 19.
Orbital frequency analyzer (OFA) is one of the electrostatic ion trap mass analysers for FTMS, which offers ultrahigh mass resolution and high ion charge capacity. In order to analyze multiply charged proteins and other large biological particles by means of charge detection mass spectrometry, a data processing algorithm was created to suit the image charge signal of nonharmonic waveform nature. The algorithm is capable of detecting collisions between ions and residual gas molecules, to determine lifetime of ions, and to evaluate the charge and mass values for ions having lifetime above a threshold. With the filtering of the lifetime and charge value, the chemical noise from small molecules and protein fragments can be eliminated in the reconstructed spectrum, facilitating measurement of protein content at a very low concentration, down to tens of nanomolars. The standard deviation of charge measurement is between 1.1 to 1.8 e for ions with oscillation lifetimes from 1 to 0.4 s, and this in turn determines the CDMS spectrum mass peak width. It has been found that the lower voltage setting of the OFA results in a larger population of ions surviving for longer times and thus produces narrower mass peak width. While OFA is able to run multiplexed CDMS without ion motion interference, coexisting ions of the same or very close / can cause interference between their image charge signals, which increases the error in charge determination.
轨道频率分析仪 (OFA) 是用于 FTMS 的静电离子阱质量分析器之一，它提供超高的质量分辨率和高的离子电荷容量。为了通过电荷检测质谱法分析多电荷蛋白质和其他大型生物颗粒，创建了一种数据处理算法，以适应非谐波波形性质的图像电荷信号。该算法能够检测离子与残余气体分子之间的碰撞，确定离子的寿命，并评估寿命超过阈值的离子的电荷和质量值。通过寿命和电荷值的过滤，可以在重建的光谱中消除小分子和蛋白质片段的化学噪声，从而可以在非常低的浓度（低至数十纳摩尔）下测量蛋白质含量。对于振荡寿命为 1 到 0.4 秒的离子，电荷测量的标准偏差在 1.1 到 1.8 e 之间，这反过来又决定了 CDMS 光谱质量峰宽。已经发现，OFA 的较低电压设置会导致更多的离子存活更长时间，从而产生更窄的质量峰宽。虽然 OFA 能够在没有离子运动干扰的情况下运行多路复用的 CDMS，但相同或非常接近的共存离子/可能会导致它们的图像电荷信号之间的干扰，从而增加电荷确定的误差。
