M/Z: 444.0845

Mass spectrometry imaging of phospholipids in mouse urinary bladder (imzML dataset)
The spatial distribution of phospholipids in a tissue section of mouse urinary bladder was analyzed by MALDI MS imaging at 10 micrometer pixel size with high mass resolution (using an LTQ Orbitrap mass spectrometer).

R, ö, mpp A, Guenther S, Schober Y, Schulz O, Takats Z, Kummer W, Spengler B, Histology by mass spectrometry: label-free tissue characterization obtained from high-accuracy bioanalytical imaging. Angew Chem Int Ed Engl, 49(22):3834-8(2010)

Fig. S2: Single ion images of compounds shown in Fig. 1A-B : (upper left to lower right) m/z = 743.5482 (unknown), m/z = 741.5307 (SM (16:0), [M+K]+), m/z = 798.5410 (PC (34:1), [M+K]+), m/z = 616.1767 (heme b, M+), m/z = 772.5253 (PC (32:0), [M+K]+).

Stability of determined mass values was in the range of +/- 1 ppm over 22 hours of measurement (Fig. S4), with a standard deviation of 0.56 ppm. Accuracy data were obtained during tissue scanning experiments by monitoring the mass signal at nominal mass 798. The internal lock mass function of the Orbitrap instrument was used for automatic calibration during imaging measurements, using the known matrix-related ion signals at m/z = 137.0233, m/z = 444.0925 and m/z = 716.1246.

Fig 6c Fig. 6 MALDI-MSI of U13C-PC16:0/16:0 acyl chain remodeling. A: Averaged MALDI mass spectrum from lung tissue collected from mice euthanized 12 h after administration of D9-choline and U13C-DPPC–containing Poractant alfa surfactant. The ion at m/z 828.6321 is assigned as the [M+Na]+ ion of 13C24-PC16:0_20:4 formed by acyl remodeling of U13C-PC16:0/16:0. The “NL” value refers to the intensity of the base peak in the full range MS1 spectrum. B: MS/MS spectrum of precursor ions at m/z 828.5 ± 0.5 with fragment ions originating from [13C24-PC16:0_20:4+Na]+ annotated. Part-per-million (ppm) mass errors are provided in parentheses. C, D: MALDI-MSI data of [U13C-DPPC+Na]+ (blue), [PC36:4+Na]+ (green) and [13C24-PC16:0_20:4+Na]+ (red) in lung tissue collected from mice (C) 12 h and (D) 18 h after label administration. All images were visualized using total-ion-current normalization and hotspot removal (high quantile = 99%). MS/MS, tandem mass spectrometry; MSI, mass spectrometry imaging; PC, phosphatidylcholine; U13C-DPPC, universally 13C-labeled dipalmitoyl PC.

Supplementary Figure S8. MALDI-MSI data of mouse lung tissue administered with D9-choline and U 13C-DPPC–containing Poractant alfa surfactant (labels administered 18 h prior to sacrifice). Ion images of (a) m/z 796.6856 ([U13C-DPPC+Na]+), (b) m/z 756.5154 [PC32:0+Na]+ and (c) m/z 765.6079 ([D9-PC32:0+Na]+). (d) Overlay image of [U13C-DPPC+Na]+ (red) and [D9-PC32:0+Na]+ (green). Parts per million (ppm) mass errors are indicated in parentheses. All images were visualised using totalion-current normalisation and using hotspot removal (high quantile = 99%). DPPC = PC16:0/16:0.