MALDI mass spectrometry imaging of proteins exceeding 30,000 daltons.
BACKGROUND
Since its introduction 10 years ago by Caprioli and associates, MALDI mass spectrometry imaging has enabled spatial analysis of drugs, lipids, peptides, and polypeptides. In polypeptides, the detectable mass range is limited to small proteins with a mass less than 25 kDa. This is a limitation, as many proteins, including cytokines, growth factors, enzymes, and receptors have molecular weights, exceeding 25 kDa. In the present work, we report the development of a novel strategy to observe higher mass proteins up to 30 kDa.


METHODS
We investigated the development of sample preparation methods based on hexafluoroisopropanol (1,1,1,3,3,3-hexaluoro-2-propanol) and 2,2,2-trifluoroethanol solvents for protein solubilization optimized for high-mass proteins.


RESULTS
We were, for the first time in mass spectrometry imaging, able to detect to proteins up to 70 kDa directly from tissue. These developments indicate future avenues by which the sensitivity of protein mass spectrometry imaging can be further improved. We applied these developments to ovarian cancer and demonstrate that protein are similar to that which can be obtained using 2D gel based analyses.


CONCLUSIONS
Increasing the possibility of detecting proteins and high-mass proteins is key for developing direct tissue proteomics and especially any potential functional investigation. These data will open the door of a novel step in mass spectrometry imaging.
Franck
Julien
J
Universite Nord de France, CNRS, MALDI Imaging Team, Laboratoire de Neuroimmunologie et Neurochimie Evolutives, Universite Lille 1, Lille, France.
Longuespée
Rémi
R
Wisztorski
Maxence
M
Van Remoortere
Alexandra
A
Van Zeijl
René
R
Deelder
André
A
Salzet
Michel
M
McDonnell
Liam
L
Fournier
Isabelle
I
D000818:Animals; D014408:Biomarkers, Tumor / Q000032:analysis; D001921:Brain / Q000378:metabolism; D005260:Female; D006801:Humans; D008297:Male; D008970:Molecular Weight; D009363:Neoplasm Proteins / Q000378:metabolism; D010051:Ovarian Neoplasms / Q000378:metabolism; D020005:Propanols; D011506:Proteins / Q000032:analysis* / Q000737:chemistry*; D040901:Proteomics; D051381:Rats; D017208:Rats, Wistar; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods*; D014020:Tissue Extracts / Q000378:metabolism; D014270:Trifluoroethanol; D006845:Hydrocarbons, Fluorinated
D014408:Biomarkers, Tumor; D009363:Neoplasm Proteins; D020005:Propanols; D011506:Proteins; D014020:Tissue Extracts; D014270:Trifluoroethanol; C001337:hexafluoroisopropanol; D006845:Hydrocarbons, Fluorinated