A method to prevent protein delocalization in imaging mass spectrometry of non-adherent tissues: application to small...

Area of Science:

• Biochemistry
• Analytical Chemistry
• Microscopy

Background:

• Matrix-assisted laser desorption/ionization (MALDI) imaging is crucial for analyzing biomolecules in tissues.
• Current methods face challenges like poor crystal formation, analyte delocalization, and tissue detachment, impacting image quality and spatial resolution.

Purpose of the Study:

• To compare different tissue mounting and washing techniques for MALDI imaging.
• To develop an optimized method for high-quality MALDI imaging of proteins in ocular tissues.

Main Methods:

• A novel method using conductive carbon substrates was developed, eliminating the need for thaw mounting or washing steps.
• This method minimizes protein delocalization and ensures strong tissue adherence to the target surface.
• The optimized protocol was applied to ocular lens sections from rat, mouse, and zebrafish.

Main Results:

• The new method yielded high-quality MALDI images with minimal to no analyte delocalization.
• Discrete localization of crystallin protein degradation products was observed in mouse and zebrafish lenses.
• Concentric rings of distinct protein content were identified, potentially explaining the refractive index gradient in vertebrate lenses.

Conclusions:

• The optimized MALDI imaging method using conductive carbon substrates significantly enhances image quality and reliability for ocular lens proteins.
• This technique provides novel insights into the spatial distribution of crystallin proteins and their degradation products in vertebrate lenses.
• The findings contribute to understanding the structural basis of lens refractive properties.