Phase correction for collision model analysis and enhanced resolving power of Fourier transform ion cyclotron resonance mass spectra
Phase correction for collision model analysis and enhanced resolving power of Fourier transform ion cyclotron resonance mass spectra
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DOI：
10.1021/ac9808019
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发表时间：
1999-01-15
影响因子：
7.4
通讯作者：
Marshall, AG
中科院分区：
文献类型：
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作者：
Vining, BA;Bossio, RE;Marshall, AG
FT-ICR数据的相位校正产生了吸收光谱，与传统的幅值模式显示器相比，质量分辨率提高了2倍(峰值高度为一半)。这一改进相当于在不损失信噪比(S/N)的情况下使施加的磁场强度加倍，只要在FFT之前用相同数量的零填充时域数据，我们的简单、直观、用户交互的算法可以快速校正相位随频率的零或更高和一阶变化。我们发现，压力限制吸收模对幅值模线型的理论质量分辨能力的提高取决于碰撞机制：硬球的1.40倍对朗之万3(1/2)(离子：诱导偶极)，因此，电喷雾牛碳酸酐(类似于29 kDa)FT-ICR质谱峰的质量分辨能力的实验增强(1.43+/-0.09)直接支持硬球碰撞模型。相位调整的最佳实现要求如下：(A)激励和检测之间的延迟不到一个采样间隔的一半，以避免基线“滚动”和Gibb振荡；(B)精确的模数转换；(C)足够长的采集周期，以在半最大峰值高度产生每个吸收模式峰值宽度的多个数据点；以及(D)避免抑制初始时间域数据的FT-ICR变迹函数(例如Hamming和Hning)。脉冲单频激励(持续时间远小于奈奎斯特带宽的倒数)可以消除高于一阶的相位随频率的变化。相态FT-ICR光谱应特别适用于复杂混合物的分析，用于解决电喷多电荷大分子中的同位素分布问题，并用于表征离子碰撞(以及离子大小和形状)。
Phase correction of FT-ICR data yields an absorption spectrum that offers a gain by up to a factor of 2 in mass resolving power (at half-maximum peak height), compared to conventional magnitude-mode display. That improvement is equivalent to doubling the applied magnetic field strength, without loss in signal-to-noise (S/N) ratio, provided that the time-domain data are padded with an equal number of zeroes before FFT, Our simple, visual, user-interactive algorithm quickly corrects for zero-or der and first-order variation of phase with frequency. We find that the theoretical mass resolving power enhancement for pressure-limited absorption-mode over magnitude-mode line shape depends on the collision mechanism: factor of 1.40 for hard sphere vs 3(1/2) for Langevin (ion: induced dipole), Thus, the experimental enhancement in mass resolving power (factor of 1.43 +/- 0.09) for isotopically resolved peaks in the FT-ICR mass spectra of electrosprayed bovine carbonic anhydrase (similar to 29 kDa) directly supports the hard-sphere collision model. Optimal implementation of phasing requires the following: (a) a delay between excitation and detection of less than half of one sampling interval to avoid baseline "roll" and Gibb's oscillations; (b) accurate analog-to-digital conversion; (c) a sufficiently long acquisition period to yield several data points per absorption-mode peak width at half-maximum peak height; and (d) avoidance of FT-ICR apodization functions (e.g., Hamming and Hanning) that suppress the initial time-domain data. Pulsed single-frequency excitation (duration much less than the reciprocal of the Nyquist bandwidth) can eliminate higher than first-order variation of phase with frequency. Phased FT-ICR spectra should prove especially desirable for analysis of complex mixtures, for resolving isotopic distributions in electrosprayed multiply charged macromolecules and for characterizing ion collisions (and thus ion size and shape).