Improving mass accuracy in matrix-assisted laser desorption ionization time-of-flight mass spectrometry analysis of pathogenic proteins using 6xHIS-tagged internal calibration.

Our In-Cal method using 6xHIS-tagged protein in MALDI-TOFMS allows successful mass calibration (<3.5 Da) of pathogenic proteins (>20 kDa) and provides high mass accuracy as much as that of medium- and high-resolution mass spectrometry.