Mass measurement errors of Fourier-transform mass spectrometry (FTMS): distribution, recalibration, and application.
The hybrid linear trap quadrupole Fourier-transform (LTQ-FT) ion cyclotron resonance mass spectrometer, an instrument with high accuracy and resolution, is widely used in the identification and quantification of peptides and proteins. However, time-dependent errors in the system may lead to deterioration of the accuracy of these instruments, negatively influencing the determination of the mass error tolerance (MET) in database searches. Here, a comprehensive discussion of LTQ/FT precursor ion mass error is provided. On the basis of an investigation of the mass error distribution, we propose an improved recalibration formula and introduce a new tool, FTDR (Fourier-transform data recalibration), that employs a graphic user interface (GUI) for automatic calibration. It was found that the calibration could adjust the mass error distribution to more closely approximate a normal distribution and reduce the standard deviation (SD). Consequently, we present a new strategy, LDSF (Large MET database search and small MET filtration), for database search MET specification and validation of database search results. As the name implies, a large-MET database search is conducted and the search results are then filtered using the statistical MET estimated from high-confidence results. By applying this strategy to a standard protein data set and a complex data set, we demonstrate the LDSF can significantly improve the sensitivity of the result validation procedure.
Zhang
Jiyang
J
Beijing Proteome Research Center, Beijing Institute of Radiation Medicine, Beijing 102206, China.
Ma
Jie
J
Dou
Lei
L
Wu
Songfeng
S
Qian
Xiaohong
X
Xie
Hongwei
H
Zhu
Yunping
Y
He
Fuchu
F
D002138:Calibration; D030562:Databases, Protein; D005583:Fourier Analysis; D006801:Humans; D013058:Mass Spectrometry / Q000295:instrumentation / Q000379:methods; D010455:Peptides / Q000032:analysis; D040901:Proteomics / Q000295:instrumentation* / Q000379:methods; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
D010455:Peptides