Total Mass Difference Statistics Algorithm: A New Approach to Identification of High-Mass Building Blocks in Electrospray Ionization Fourier Transform Ion Cyclotron Mass Spectrometry Data of Natural O

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• 作者：Erast V. Kunenkov ; Alexey S. Kononikhin ; Irina V. Perminova ; Norbert Hertkorn ; Andras Gaspar ; Philippe Schmitt-Kopplin ; Igor A. Popov ; Andrew V. Garmash ; Evgeniy N. Nikolaev
• 刊名：Analytical Chemistry
• 出版年：2009
• 出版时间：December 15, 2009
• 年：2009
• 卷：81
• 期：24
• 页码：10106-10115
• 全文大小：266K
• 年卷期：v.81,no.24(December 15, 2009)
• ISSN：1520-6882

文摘

The ultrahigh-resolution Fourier transform ion cyclotron resonance (FTICR) mass spectrum of natural organic matter (NOM) contains several thousand peaks with dozens of molecules matching the same nominal mass. Such a complexity poses a significant challenge for automatic data interpretation, in which the most difficult task is molecular formula assignment, especially in the case of heavy and/or multielement ions. In this study, a new universal algorithm for automatic treatment of FTICR mass spectra of NOM and humic substances based on total mass difference statistics (TMDS) has been developed and implemented. The algorithm enables a blind search for unknown building blocks (instead of a priori known ones) by revealing repetitive patterns present in spectra. In this respect, it differs from all previously developed approaches. This algorithm was implemented in designing FIRAN-software for fully automated analysis of mass data with high peak density. The specific feature of FIRAN is its ability to assign formulas to heavy and/or multielement molecules using “virtual elements” approach. To verify the approach, it was used for processing mass spectra of sodium polystyrene sulfonate (PSS, M_w = 2200 Da) and polymethacrylate (PMA, M_w = 3290 Da) which produce heavy multielement and multiply-charged ions. Application of TMDS identified unambiguously monomers present in the polymers consistent with their structure: C₈H₇SO₃Na for PSS and C₄H₆O₂ for PMA. It also allowed unambiguous formula assignment to all multiply-charged peaks including the heaviest peak in PMA spectrum at mass 4025.6625 with charge state 6− (mass bias −0.33 ppm). Application of the TMDS-algorithm to processing data on the Suwannee River FA has proven its unique capacities in analysis of spectra with high peak density: it has not only identified the known small building blocks in the structure of FA such as CH₂, H₂, C₂H₂O, O but the heavier unit at 154.027 amu. The latter was identified for the first time and assigned a formula C₇H₆O₄ consistent with the structure of dihydroxyl-benzoic acids. The presence of these compounds in the structure of FA has so far been numerically suggested but never proven directly. It was concluded that application of the TMDS-algorithm opens new horizons in unfolding molecular complexity of NOM and other natural products.