Peptide calibration standard kit 2

2,5-Dihydroxybenzoic acid
(DHB) and ethanol
were purchased from MilliporeSigma (St. Louis, MO). Hoechst 33342
was purchased from Life Technologies (Gaithersburg, MD). Peptide Calibration
Standard Kit II (angiotensin II, angiotensin I, substance P, bombesin,
ACTH clip 1–17, ACTH clip 18–39, somatostatin 28, bradykinin
fragment 1–7) was purchased from Bruker Corp. (Billerica, MA).
All reagents were used as received (>98% purity) without further
purification.

MALDI MS imaging was performed using an UltrafleXtreme MALDI TOF/TOF MS (Bruker Daltonics, USA) with a frequency tripled Nd:YAG solid-state laser (λ = 355nm). The laser was set to the 'Ultra' footprint setting at an ~100 μm diameter. Mass spectrometer calibration was performed using DHB matrix ions and a Peptide Calibration Standard Kit II (Bruker Daltonics). Tissue sections were analyzed in positive reflectron ion mode with 100 laser shots fired at 1000 Hz and imaged with a 100 μm or 400 μm laser step size. MSI data was analyzed using flexAnalysis 3.4 and flexImaging 4.1 (Bruker Daltonics). Additionally, accurate mass measurement and tandem MS analysis of tetrandrine metabolite were performed on a 9.4T solariX™ Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer equipped with a dual MALDI and ESI source (Bruker Daltonics, USA). Data were analyzed using Data Analysis 4.0 (Bruker). For 3D MALDI imaging of kidney, 7 kidney sections, in 300 µm steps throughout the half tissue volume, were subjected to MALDI MSI analysis. The data for all 7 sections were imported into the software SCiLS Lab version 2016b (SCiLS, Bremen, Germany) to reconstruct the original relations between the sections.