@article{xi_knizner_garrard_muddiman_2023, title={Automatic z-Axis Correction for IR-MALDESI Mass Spectrometry Imaging of Uneven Surfaces}, volume={6}, ISSN={["1879-1123"]}, DOI={10.1021/jasms.3c00151}, abstractNote={Two-dimensional mass spectrometry imaging (2D MSI) experiments mainly involve samples with a flat surface and constant thickness, but some samples are challenging to section due to the texture and topography. Herein, we present an MSI method that automatically corrects for discernible height differences across surfaces during imaging experiments. A chromatic confocal sensor was incorporated into the infrared matrix-assisted laser desorption electrospray ionization (IR-MALDESI) system to measure the sample surface height at the location of each analytical scan. The height profile is subsequently used for adjusting the z-axis position of the sample during MSI data acquisition. We evaluated this method using a tilted mouse liver section and an unsectioned Prilosec tablet due to their exterior quasi-homogeneity and height differences of approximately ∼250 μm. MSI with automatic z-axis correction showed consistent ablated spot sizes and shapes, revealing the measured ion spatial distribution across a mouse liver section and a Prilosec tablet. Conversely, irregular spots and reduced signals with large variability were observed when no z-axis correction was applied.}, journal={JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY}, author={Xi, Ying and Knizner, Kevan T. T. and Garrard, Kenneth P. P. and Muddiman, David C. C.}, year={2023}, month={Jun} }
 @article{joignant_knizner_xi_muddiman_2023, title={Evaluating the optimal tissue thickness for mass spectrometry imaging using infrared matrix-assisted laser desorption electrospray ionization}, volume={37}, ISSN={["1097-0231"]}, DOI={10.1002/rcm.9638}, abstractNote={RationaleInfrared matrix‐assisted laser desorption electrospray ionization (IR‐MALDESI) utilizes a 2970 nm mid‐IR laser to desorb samples with depth resolutions (Z) on the order of micrometers. Conventionally, 5–20 μm thick tissue sections are used to characterize different applications of the IR‐MALDESI source, but an optimal thickness has not been systematically investigated.}, number={22}, journal={RAPID COMMUNICATIONS IN MASS SPECTROMETRY}, author={Joignant, Alena N. and Knizner, Kevan T. and Xi, Ying and Muddiman, David C.}, year={2023}, month={Nov} }
 @article{joignant_xi_muddiman_2023, title={Impact of wavelength and spot size on laser depth of focus: Considerations for mass spectrometry imaging of non-flat samples}, volume={3}, ISSN={["1096-9888"]}, DOI={10.1002/jms.4914}, abstractNote={Abstract}, journal={JOURNAL OF MASS SPECTROMETRY}, author={Joignant, Alena N. N. and Xi, Ying and Muddiman, David C. C.}, year={2023}, month={Mar} }
 @article{xi_sohn_joignant_cologna_prentice_muddiman_2023, title={SMART: A data reporting standard for mass spectrometry imaging}, volume={58}, ISSN={["1096-9888"]}, DOI={10.1002/jms.4904}, abstractNote={Abstract}, number={2}, journal={JOURNAL OF MASS SPECTROMETRY}, author={Xi, Ying and Sohn, Alexandria L. and Joignant, Alena N. and Cologna, Stephanie M. and Prentice, Boone M. and Muddiman, David C.}, year={2023}, month={Feb} }
 @article{xi_muddiman_2021, title={Enhancing Metabolomic Coverage in Positive Ionization Mode Using Dicationic Reagents by Infrared Matrix-Assisted Laser Desorption Electrospray Ionization}, volume={11}, ISSN={["2218-1989"]}, DOI={10.3390/metabo11120810}, abstractNote={Mass spectrometry imaging is a powerful tool to analyze a large number of metabolites with their spatial coordinates collected throughout the sample. However, the significant differences in ionization efficiency pose a big challenge to metabolomic mass spectrometry imaging. To solve the challenge and obtain a complete data profile, researchers typically perform experiments in both positive and negative ionization modes, which is time-consuming. In this work, we evaluated the use of the dicationic reagent, 1,5-pentanediyl-bis(1-butylpyrrolidinium) difluoride (abbreviated to [C5(bpyr)2]F2) to detect a broad range of metabolites in the positive ionization mode by infrared matrix-assisted laser desorption electrospray ionization mass spectrometry imaging (IR-MALDESI MSI). [C5(bpyr)2]F2 at 10 µM was doped in 50% MeOH/H2O (v/v) electrospray solvent to form +1 charged adducted ions with anionic species (−1 charged) through post-electrospray ionization. This method was demonstrated with sectioned rat liver and hen ovary. A total of 73 deprotonated metabolites from rat liver tissue sections were successfully adducted with [C5(bpyr)2]2+ and putatively identified in the adducted positive ionization polarity, along with 164 positively charged metabolite ions commonly seen in positive ionization mode, which resulted in 44% increased molecular coverage. In addition, we were able to generate images of hen ovary sections showing their morphological features. Following-up tandem mass spectrometry (MS/MS) indicated that this dicationic reagent [C5(bpyr)2]2+ could form ionic bonds with the headgroup of glycerophospholipid ions. The addition of the dicationic reagent [C5(bpyr)2]2+ in the electrospray solvent provides a rapid and effective way to enhance the detection of metabolites in positive ionization mode.}, number={12}, journal={METABOLITES}, author={Xi, Ying and Muddiman, David C.}, year={2021}, month={Dec} }