Journal of Chromatography & Separation Techniques
Open Access
ISSN: 2157-7064
+44 1300 500008
ISSN: 2157-7064
+44 1300 500008
Cheng-Chih Hsu and Richard N Zare
National Taiwan University, Taiwan
Stanford University, USA
Posters & Accepted Abstracts: J Chromatogr Sep Tech
Molecular imaging of lipids and metabolites in tissues under ambient conditions is readily achieved using desorption electrospray ionization (DESI), but DESI is essentially blind to the presence of proteins. In 2013, we demonstrated that the use of nanospray desorption electrospray ionization (nanoDESI) in combination with an inverted microscope overcomes this problem and allows us to visualize proteins in tissue samples in a label-free manner at atmospheric pressure with only minimum sample preparation. However, this microscopy-guided approach is not efficient especially while imaging larger tissue sections. To improve the utility of this technique, we interfaced a 2D stage with nanoDESI to direct and for continuous mass spectrometry scannings on tissue sections. Multiple charged proteins with masses up to 15 kDa were successfully measured by nanoDESI using an LTQ Orbitrap mass spectrometers. In a mice brain section, expression of proteins was previously found by matrix-assisted laser desorption ionization (MALDI) mass spectrometry imaging, including ubiquitin, �²-thymosin, and myelin basic protein, were spatially-mapped, and the identified via top-down approaches. We also determined the location of methylation on myelin basic protein. This imaging modality was further implemented to MYC-induced lymphomas. We observed an array of truncated proteins in the region where normal thymus cells were infiltrated by tumor cells, in contrast to healthy tissue. The detection limits for cytochrome c and insulin are 10- 50 picomoles per mg of tissue, at which level many endogenous proteins are expressed in cells. It is expected that this new tool will provide important biological insight into cellular processes.
Email: ccrhsu@ntu.edu.tw