Degree

Doctor of Philosophy (PhD)

Department

Chemistry

Document Type

Dissertation

Abstract

Abstract

Matrix assisted laser desorption ionization (MALDI) mass spectrometry (MS) can be used to obtain localization and chemical information of hydrophobic biomolecules on tissue samples.  A technique has been developed to modify a standard MALDI matrix that improves the selectivity for hydrophobic biomolecules on the tissue sample. The modification involves the use of a Group of Uniform Materials Based on Organic Salts (GUMBOS). GUMBOS are ionic liquids (IL) that are bulky organic ions with a counter ion that can be changed for tuning.  They are more stable than traditional matrices under vacuum.  Unlike traditional IL’s, the GUMBOS melting point ranges from 250C-250oC.  GUMBOS enhance the traditional matrix by increasing the signal intensity and signal-to-noise ratio while still providing excellent sensitivity and resolution.  GUMBO matrix performance was measured by counting the number of lipids detected on the tissue sample surface during MALDI-MS imaging.

Rat liver was purchased. 12 µm thick tissue samples were sliced and mounted on a glass slide coated in indium tin oxide (ITO). Experimental procedures outlined in previous studies were used to prepare the GUMBOS matrix.  The standard matrix was modified with a GUMBO.  A solution of alpha-Cyano-4-hydroxycinmic acid (CHCA) and a primary amine was prepared by dissolving an equimolar amount of the compounds in methanol.  The two solutions were then stirred together for 24 hours.  Rotary evaporation was used to remove methanol. An HTX automated sprayer was used to coat rat liver tissue samples with the matrix. All spectra were obtained using a MALDI-TOF mass spectrometer (RapiFlex, Bruker, Bremen, Germany) in positive ion reflectron mode.  Data were processed using FlexAnalysis 3.3 Software (Bruker). SCiLS Lab software (version 2024b, Bruker Daltonics, Billerica, MA, USA) was used for visualization and further analysis.

Experiments were aimed at demonstrating that the standard MALDI matrix CHCA could be modified to synthesize a GUMBOS MALDI matrix.  Experiments show that modifying the CHCA matrix with a GUMBO increases the hydrophobicity of the standard matrix.  Statistical data analysis shows that modification enhances selectivity of the matrix without hindering the sensitivity of the matrix.

Date

7-30-2026

Committee Chair

Garno, Jayne

LSU Acknowledgement

1

LSU Accessibility Acknowledgment

1

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