title: Impact of tissue surface properties on the desorption electrospray ionization imaging of organic acids in grapevine stem.
abstract: BACKGROUND
  Desorption electrospray ionization (DESI) imaging is a fast analytical technique used to assess spatially resolved biological processes over unmodified sample surfaces. Although DESI profiling experiments have demonstrated that the properties of the sample surface significantly affect the outcomes of DESI analyses, the potential implications of these phenomena in imaging applications have not yet been explored extensively.
  
  
  METHODS
  The distribution of endogenous and exogenous organic acids in pith and out pith region of grapevine stems was investigated by using DESI imaging, ion chromatography and direct infusion methods. Several common normalization strategies to account for the surface effect, including TIC normalization, addition of the internal standard in the spray solvent and deposition of the standard over the sample surface, were critically evaluated.
  
  
  RESULTS
  DESI imaging results show that, in our case, the measured distributions of these small organic acids are not consistent with their 'true' localizations within the tissues. Furthermore, our results indicate that the common normalization strategies are not able to completely compensate for the observed surface effect.
  
  
  CONCLUSIONS
  Variations in the tissue surface properties across the tissue sample can greatly affect the semi-quantitative detection of organic acids. Attention should be paid when interpreting DESI imaging results and an independent analytical validation step is important in untargeted DESI imaging investigations.
authors: Biostatistics and Data Management, Research and Innovation Centre - Fondazione Edmund Mach, S. Michele all'Adige, (TN), Italy.
authors: Yonghui
authors: Y
authors: Dong
authors: Bioorganic Chemistry Laboratory, Department of Physics, University of Trento, Povo, (TN), Italy.
authors: Graziano
authors: G
authors: Guella
authors: Biostatistics and Data Management, Research and Innovation Centre - Fondazione Edmund Mach, S. Michele all'Adige, (TN), Italy.
authors: Pietro
authors: P
authors: Franceschi
mesh_terms: D002264:Carboxylic Acids / Q000032:analysis* / Q000737:chemistry; D018547:Plant Stems / Q000737:chemistry*; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*; D013499:Surface Properties; D027843:Vitis / Q000737:chemistry*
chemical_list: D002264:Carboxylic Acids