ポスター発表
- 第3日 5月17日（木） ポスター会場
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3P-27 PDF
“Je t'aime… moi non plus": the love-hate relationship of charge states and mass defects of polymer ions
The Kendrick mass defect (KMD) analysis is a powerful processing tool for complex mass spectra but so far conducted exclusively on singly charged ions from MALDI-MS data. In case of multiple charging, ion series at charge state z surprisingly split in z lines in the KMD plot in lieu of one line for singly charged counterparts. Unfortunately, an “isotopic misalignment" may go with this “isotopic split". Homologous ions line up obliquely instead of horizontally in opposition to the basics of a KMD analysis. We propose a mathematical origin for the beneficial isotopic split and for the associated isotopic misalignment found to arise from the indivisibility of the rounded mass of the repeat unit by the charge state. Two solutions are also discussed to either remove the isotopic misalignment using a fractional base unit or the isotopic split itself using a newly developed “remainders of KM" plot. Depending on their need, users facing multiple charging can choose to compute 1) a regular KMD plot to deconvolute the charge-state distribution instantly by counting lines or 2) a resolution-enhanced KMD plot for an isotopically-resolved selection of homologous ions or 3) a RKM plot to filter a full distribution with no interferences.