Improved spatial resolution of matrix-assisted laser desorption/ionization imaging of lipids in the brain by alkylated derivatives of 2,5-dihydroxybenzoic acid.
BACKGROUND
Matrix-assisted laser desorption/ionization (MALDI) is one of the major techniques for mass spectrometry imaging (MSI) of biological systems along with secondary-ion mass spectrometry (SIMS) and desorption electrospray mass spectrometry (DESI). The inherent variability of MALDI-MSI signals within intact tissues is related to the heterogeneity of both the sample surface and the matrix crystallization. To circumvent some of these limitations of MALDI-MSI, we have developed improved matrices for lipid analysis based on structural modification of the commonly used matrix 2,5-dihydroxybenzoic acid (DHB).


METHODS
We have synthesized DHB containing -C6H13 and -C12H25 alkyl chains and applied these matrices to rat brain using a capillary sprayer. We utilized a Bruker Ultraflex II MALDI-TOF/TOF mass spectrometer to analyze lipid extracts and tissue sections, and examined these sections with polarized light microscopy and differential interference contrast microscopy.


RESULTS
O-alkylation of DHB yields matrices, which, when applied to brain sections, follow a trend of phase transition from crystals to an oily layer in the sequence DHB → DHB-C6H13 → DHB-C12H25 . MALDI-MSI images acquired with DHB-C12H25 exhibited a considerably higher density of lipids than DHB.


CONCLUSIONS
Comparative experiments with DHB and DHB-C12H25 are presented, which indicate that the latter matrix affords higher lateral resolution than the former.
Department of Environmental and Occupational Health, University of Pittsburgh, Pittsburgh, PA, 15219, USA; Center for Free Radical and Antioxidant Health, University of Pittsburgh, Pittsburgh, PA, 15219, USA.
D A
DA
Stoyanovsky
L J
LJ
Sparvero
A A
AA
Amoscato
R R
RR
He
S
S
Watkins
B R
BR
Pitt
H
H
Bayir
V E
VE
Kagan
D000818:Animals; D001923:Brain Chemistry; D005841:Gentisates / Q000737:chemistry*; D006651:Histocytochemistry / Q000379:methods*; D008055:Lipids / Q000032:analysis*; D008297:Male; D057054:Molecular Imaging / Q000379:methods; D051381:Rats; D017207:Rats, Sprague-Dawley; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods*
D005841:Gentisates; D008055:Lipids; C010925:2,5-dihydroxybenzoic acid