Fig. 2: 4D peak detection in human urine samples.
From: A mass spectrum-oriented computational method for ion mobility-resolved untargeted metabolomics

NIST human urine samples were acquired using TIMS with PASEF-DDA technology in positive mode and processed using Met4DX (n = 6 technical replicates). a–c The numbers of raw MS2 spectra (a), unique MS2 spectra (b), and assembled 4D features (c) in each sample replicate. Numbers represent mean ± SD (n = 6 technical replicates). d The total number of 4D features with a minimal fraction of 0.5 applied. e An example of kynurenic acid in urine sample was employed to demonstrate the bottom-up assembly algorithm for 4D peak detection in Mex4DX. Red arrow in the m/z-ion mobility data frame indicates the precursor data point for the unique MS2 spectrum. The combined symbols of open/closed cycles and the arrow in the unique MS2 spectrum represent a product ion scan to generate an MS2 spectrum from a fixed precursor ion.