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. Author manuscript; available in PMC: 2014 Jun 15.
Published in final edited form as: Methods. 2013 Mar 13;61(3):219–226. doi: 10.1016/j.ymeth.2013.03.004

Figure 1.

Figure 1

Sample complexity prevents identification of peptides from complex samples based solely on accurate precursor mass measurements. Precursor masses from all tryptic fragments from the Human 2009 database with charge states +2 to +4 that fall between m/z 350 and 1500 were considered. Precursor masses were binned into windows generated at four different resolutions. As the number of peptides per bin increases the percentage of total peptides accounted for increases. At 10ppm a vanishingly small percentage of peptides are the sole occupant of their bin making it nearly impossible to accurately identify peptides based on their precursor mass alone. At 1ppm this figure is improved to roughly 5%. This problem is exacerbated when post translational modifications and missed or non-tryptic cleavages are included.