title: Determination of a correction to improve mass measurement accuracy of isotopically unresolved polymerase chain reaction amplicons by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry.
abstract: The experimental determination of average mass by mass spectrometry is limited for large molecules due to the negative bias introduced by the natural distribution of isotopic abundances. This results in the measurement of the top-of-centroid (ToC) as opposed to the true centroid. We have developed a practical correction factor that is applied to the ToC measurement to largely remove the systematic bias introduced by nature. The correction factor is calculated easily using the average molecular mass (<100 kDa) of the analyte molecule and the full-width half maximum resolving power (<3,500) of the measurement. In addition, an approach to calculating resolving power is described that accurately predicts resolving power achievable for Fourier transform ion cyclotron resonance (FT-ICR) mass analysis of large molecules. A combination of internal calibration with a dual-electrospray source and application of the correction factor to average mass measurements improved the mass error from 192.5 to -35.0 ppm for a 44 kDa PCR amplicon.
authors.affiliation: Department of Biochemistry and Molecular Biology and the W.M. Keck FT-ICR Mass Spectrometry Laboratory, Mayo Proteomics Research Center, Mayo Clinic and Foundation, Rochester, MN 55905, USA.
authors.forename: Allison P
authors.initials: AP
authors.lastname: Null
authors.forename: David C
authors.initials: DC
authors.lastname: Muddiman
mesh_terms: D006801:Humans; D008970:Molecular Weight; D009696:Nucleic Acids / Q000032:analysis; D016133:Polymerase Chain Reaction; D011506:Proteins / Q000032:analysis; D015203:Reproducibility of Results; D021241:Spectrometry, Mass, Electrospray Ionization / Q000295:instrumentation / Q000379:methods*; D017550:Spectroscopy, Fourier Transform Infrared / Q000295:instrumentation / Q000379:methods*; D020080:Tandem Repeat Sequences / Q000235:genetics*
chemical_list: D009696:Nucleic Acids; D011506:Proteins