Recently, mass-spectrometry methods show its utility in tumor boundary location.The effect of differences between research and clinical protocols such as low-and high-resolution measurements and sample storage have to be understood and taken into account to transfer methods from bench to bedside. In this study, we demonstrate a simple way to compare mass spectra obtained by different experimental protocols, assess its quality, and check for the presence of outliers and batch effect in the dataset. We compare the mass spectra of both fresh and frozen-thawed astrocytic brain tumor samples obtained with the inline cartridge extraction prior to electrospray ionization. Our results reveal the importance of both positive and negative ion mode mass spectrometry for getting reliable information about sample diversity. We show that positive mode highlights the difference between protocols of mass spectra measurement, such as fresh and frozen-thawed samples, whereas negative mode better characterizes the histological difference between samples. We also show how the use of similarity spectrum matrix helps to identify the proper choice of the measurement parameters, so data collection would be kept reliable, and analysis would be correct and meaningful.
K E Y W O R D Sbrain tumor, data conversion, inline cartridge extraction, low-and high-resolution comparison, spectra stability and reproducibility
| INTRODUCTIONFast tissue profiling methods for mass spectrometers allowed developing methods of rapid analysis of biological substances. [1][2][3][4][5][6][7] There are a lot of attempts to incorporate mass spectrometry into the clinical routine for surgery assistance purposes. [8][9][10][11][12] Mass spectra of complex mixtures of biological molecules, even those whose mass is up to 1000 Da, is still rather a difficult task, because of the enormous diversity of molecules contained in biological tissues. 13,14 Despite the common practice of LC-MS/MS to be used as an instrument for accurate identification of complex mixture components, it could not be used as a routine technique for rapid analyses. 15 Therefore, rapid analyses
It is known that aspartic acid isomerization process plays a role in aging processes and may be used as a marker for aging of natural materials. As for Alzheimer's disease, the most abundant modification in the peptide profile is the aspartate isomerization of amyloid-β. Liquid chromatography-electrospray ionization-mass spectrometry/mass spectrometry-based approaches with Collision Induced Dissociation (CID) or Electron Capture Dissociation (ECD) fragmentation provide a good and precise method for the relative quantitation of iso- to normal amyloid-β peptides but require additional time consuming steps. In this study, MALDI-TOF/TOF-matrix-assisted laser desorption ionization time-of-flight tandem mass spectrometry (MS) method was developed as a high-throughput approach for the relative quantitation of the isomerized form of the amyloid-β peptide.
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