title: Determination of accurate protein monoisotopic mass with the most abundant mass measurable using high-resolution mass spectrometry.
abstract: While recent developments in mass spectrometry enable direct evaluation of monoisotopic masses (M(mi)) of smaller compounds, protein M(mi) is mostly determined based on its relationship to average mass (Mav). Here, we propose an alternative approach to determining protein M(mi) based on its correlation with the most abundant mass (M(ma)) measurable using high-resolution mass spectrometry. To test this supposition, we first empirically calculated M(mi) and M(ma) of 6158 Escherichia coli proteins, which helped serendipitously uncover a linear correlation between these two protein masses. With the relationship characterized, liquid chromatography-mass spectrometry was employed to measure M(ma) of protein samples in its ion cluster with the highest signal in the mass spectrum. Generally, our method produces a short series of likely M(mi) in 1-Da steps, and the probability of each likely M(mi) is assigned statistically. It is remarkable that the mass error of this M(mi) is as miniscule as a few parts per million, indicating that our method is capable of determining protein M(mi) with high accuracy. Benefitting from the outstanding performance of modern mass spectrometry, our approach is a significant improvement over others and should be of great utility in the rapid assessment of protein primary structures.
authors.affiliation: Institute of Biochemistry and Molecular Biology, National Yang-Ming University, Taipei 112, Taiwan.
authors.forename: Ya-Fen
authors.initials: YF
authors.lastname: Chen
authors.forename: C Allen
authors.initials: CA
authors.lastname: Chang
authors.forename: Yu-Hsuan
authors.initials: YH
authors.lastname: Lin
authors.forename: Yeou-Guang
authors.initials: YG
authors.lastname: Tsay
mesh_terms: D002853:Chromatography, Liquid / Q000379:methods*; D029968:Escherichia coli Proteins / Q000032:analysis / Q000737:chemistry; D013058:Mass Spectrometry / Q000379:methods*; D008970:Molecular Weight; D011506:Proteins / Q000032:analysis* / Q000737:chemistry
chemical_list: D029968:Escherichia coli Proteins; D011506:Proteins
keywords: High-resolution mass spectrometry; Monoisotopic mass; Most abundant mass