. Author manuscript; available in PMC: 2020 Jan 1.

Published in final edited form as: Int J Mass Spectrom. 2018 Oct 22;435:136–144. doi: 10.1016/j.ijms.2018.10.023

Table 1.

Error in mass accuracy between calculated & experimental m/z when ‘Q’ is present at position 20 in sheep albumin is compared to the error in accuracy when ‘K’ is supposed to replace ‘Q’. The deviation in the mass at m/z of 800 is within 6 ppm, which is sufficient to differentiate ‘K’ from ‘Q’.

Residue position from N-terminus	Amino acid	Experimental b³⁺	Calculated^a b³⁺	Calculated^b b³⁺	Error (ppm) between Calc’d^a and Expt’l b³⁺	Error (ppm) between Calc’d^b and Expt’l b³⁺
20	Q	790.3648	790.3686	790.3807	4.7488	20.0578
21	G	809.3720	809.3757	809.3878	4.5550	19.5456
22	L	847.0655	847.0704	847.0825	5.7689	20.0925
23	V	880.0877	880.0932	880.1053	6.2342	20.0203
24	L	917.7826	917.7879	917.8000	5.7602	18.9439

b³⁺ if ‘Q’ is present

b³⁺ if ‘K’ is present