TESTING APPLICATION OF THE FILTER DIAGONALIZATION METHOD TO FTMS

滤波器对角化方法在FTMS中的测试应用

• 批准号: 7955922
• 负责人: PETER B. O'CONNOR
• 金额: $ 0.19万
• 依托单位: BOSTON UNIVERSITY MEDICAL CAMPUS
• 依托单位国家: 美国
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-06-01 至 2010-05-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7955922
• 关键词: Algorithms; Amaze; Back; Biology; Boston; Caliber; Charge; Computer Retrieval of Information on Scientific Projects Database; Computer software; Cyclotrons; Data; Data Analyses; Electrons; Frequencies; Funding; Grant; Housing; Institution; Ions; Isotopes; Length; Mass Spectrum Analysis; Medicine; Methods; Nipples; Noise; Ocular orbit; Pattern; Phase; Publishing; Quantum Mechanics; Research; Research Personnel; Resolution; Resources; Sampling; Shapes; Signal Transduction; Source; Substance P; System; Techniques; Testing; United States National Institutes of Health; Universities; base; cesium iodide; computerized data processing; density; instrument; open source; research study; simulation; tool

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The Filter Diagonalization Method (FDM) is a recently developed signal processing algorithm based on quantum mechanic's mathematical formalism of the harmonic inversion problem. FDM is shown to provide extremely high precision in finding resonance frequencies with 1ppm accuracy on small number of transient data points e.g. 10k. It was used in frequency shift chasing experiments for the purposes of determining intra-transient frequency shifts and using them for reference deconvolution and study of space charge effect. In this study we used an in-house C++ implementation of the FFT Square Window FDM, which will be available as open source software in an upcoming release of the Boston University Data Analysis (BUDA) system. Theoretical spectra were generated by using in-house simulation software with 1 mega-point length and 1 MHz sampling rate. Real spectra of Substance P were acquired on homebuilt ESI FTMS instrument (1 mega-point length with 1MHz acquisition rate). Frequency chasing experiments were performed on transient domains ranging from 1000 to 20000 data points starting with the 0 offset and shifting depending on the experiment from 1 to 200 data points into the transient. Kwin used ranges from 4-11 points. FDM shows amazing precision and high resolution on small number of data points. FDM is much slower and not as stable as FFT and for that reason cannot compete directly with FFT. However FDM proves to be a good tool for reconstructing frequency shift plots. On theoretical spectra it showed ability to trace frequency shifts of .005 Hz with signal:noise ratio of 2. A substance P spectrum was used in the frequency chasing experiment (figure 1). The isotopic beat pattern is faithfully reproduced in both abundance and frequency shifts. Space charge, even for such a simple spectrum, are approximately 400 ppm even though post FFT, it is possible to get 1ppm mass accuracy on this spectrum. This result indicates that the FFT effectively averages out these cyclic frequency shifts to achieve its results. FDM, therefore, is a new tool for study space charge. The frequency shift plots, if they are shown to be consistent, could be used in reference deconvolution. The application of FDM in extreme space charge conditions, such as those caused by the famous "nipple effect" has been carried out. The results were recently published in JASMS (2009, 20, 247-256). The spontaneous loss of coherence catastrophe (SLCC), colloquially known as the "nipple effect", describes a phenomenon in FT-ICR mass spectrometry, where the transient collapses and dies out quickly, forming a nipple-like shape. Although SLCC is a frequently observed, space-charge related effect in FT-ICR MS, it is also one that is poorly studied. In this study, the FDM is used to study the SLCC. Because FDM's resolution depends not on the length of the transient signal, but rather on the local peak density, it is capable of operating on very short transients. It is also reliable under noisy conditions, and reproduces complete information about a peak. All of these factors make it an ideal technique for studying rapid space charge induced frequency modulations in FT-ICR MS. It was found that frequency spikes correlated with amplitude minima before the SLCC, which agreed with the known observation that frequency increases at lower space-charge conditions. The fact that this correlation flipped over at the SLCC suggested that the isotope ion packets were temporarily coming back into phase (high space charge) at the amplitude minima. It was proposed that this may occur only when the magnetron orbit diameter is similar to that of the cyclotron orbit. This claim was supported by the electron promoted ion coherence (EPIC) experiments, which showed that the SLCC is observed only when there is a strong magnetron component. These findings reinforced the need for reduction of magnetron drift and space-charge induced frequency modulation when pursuing the higher mass accuracy and resolving power capabilities of the FT-ICR MS. Using the FDM based frequency shift analysis, we have also shown the ability to determine how axial oscillations perturb the cyclotron frequency. This is a far smaller effect than the isotopic beat pattern effect previously shown, so in order to do it, we had to use a peak without isotopes, and Cesium Iodide was able to provide a nice cluster peak for just this purpose.

这个子项目是许多研究子项目中的一个 由NIH/NCRR资助的中心赠款提供的资源。子项目和 研究者（PI）可能从另一个NIH来源获得了主要资金， 因此可以在其他CRISP条目中表示。所列机构为 研究中心，而研究中心不一定是研究者所在的机构。 滤波对角化方法（FDM）是近年来发展起来的一种基于量子力学谐波反演问题数学形式的信号处理算法。FDM被证明提供极高的精度，在寻找谐振频率与1 ppm的精度上的少量的瞬态数据点，例如10 k。 它被用于频移追踪实验，目的是确定瞬态内频移，并将其用于参考反卷积和空间电荷效应的研究。 在这项研究中，我们使用了FFT方形窗口FDM的内部C++实现，该实现将在即将发布的波士顿大学数据分析（BUDA）系统中作为开源软件提供。通过使用内部模拟软件以1兆点长度和1 MHz采样率生成理论光谱。P物质的真实的光谱是在自制的ESI FTMS仪器（1兆点长度，1 MHz采集速率）上获得的。频率追踪实验进行瞬态域范围从1000至20000数据点开始的0偏移和移位取决于实验从1到200数据点到瞬态。Kwin使用的范围从4-11点。 FDM在少量数据点上显示出惊人的精度和高分辨率。FDM比FFT慢得多，也不如FFT稳定，因此不能直接与FFT竞争。然而，FDM被证明是一个很好的工具，用于重建频移图。在理论频谱上，它显示出跟踪.005 Hz频率偏移的能力，信噪比为2。 在频率追踪实验中使用了P物质光谱（图1）。同位素拍频模式在丰度和频率偏移上都被忠实地再现。即使对于这样简单的光谱，空间电荷也约为400 ppm，即使在FFT后，也可以在该光谱上获得1 ppm的质量精度。该结果表明FFT有效地平均了这些循环频率偏移以实现其结果。 因此，有限差分法是研究空间电荷的新工具。如果频移图被证明是一致的，则可以用于参考反卷积。 有限差分法在极端空间电荷条件下的应用，如著名的“乳头效应”所造成的。研究结果最近发表在JASMS（2009，20，247-256）上。 自发性相干突变损失（SLCC），俗称“乳头效应”，描述了FT-ICR质谱中的一种现象，其中瞬态崩溃并迅速消失，形成乳头状形状。虽然SLCC是FT-ICR MS中经常观察到的空间电荷相关效应，但它也是研究较少的效应。 在本研究中，有限差分法被用来研究SLCC。由于FDM的分辨率不取决于瞬态信号的长度，而是取决于局部峰值密度，因此它能够在非常短的瞬态下工作。它在噪声条件下也是可靠的，并且再现关于峰值的完整信息。所有这些因素使其成为一个理想的技术，用于研究快速空间电荷诱导的频率调制FT-ICR MS。有人发现，频率尖峰与振幅最小值前的SLCC，这与已知的观察，即频率增加，在较低的空间电荷条件。这种相关性在SLCC翻转的事实表明，同位素离子包在振幅最小值时暂时回到相位（高空间电荷）。有人提出，这可能只发生在磁控管轨道直径是类似的回旋加速器轨道。电子促进离子相干（EPIC）实验支持了这一说法，该实验表明，SLCC仅在强磁控管分量时才被观察到。这些发现加强了在追求FT-ICR MS的更高质量精度和分辨能力时减少磁控管漂移和空间电荷诱导的频率调制的需要。 使用基于频移分析的FDM，我们还展示了确定轴向振荡如何扰动回旋频率的能力。 这是一个比之前显示的同位素拍频效应小得多的效应，所以为了做到这一点，我们必须使用一个没有同位素的峰，碘化铯能够为此提供一个很好的簇峰。