Matrix-Assisted Laser Desorption/Ionization Imaging Mass Spectrometry for the Investigation of Proteins and Peptides

Abstract

Mass spectrometry (MS) is an excellent technology for molecular imaging because of its high data dimensionality. MS can monitor thousands of individual molecular data channels measured as mass-to-charge (m/z). We describe the use of matrix-assisted laser desorption/ionization (MALDI) MS for the image analysis of proteins, peptides, lipids, drugs, and metabolites in tissues. We discuss the basic instrumentation and sample preparation methods needed to produce high-resolution images and high image reproducibility. Matrix-addition protocols are briefly discussed along with normal operating procedures, and selected biological and medical applications of MALDI imaging MS are described. We give examples of both two- and three-dimensional imaging, including normal mouse embryo implantation, sperm maturation in mouse epididymis, protein distributions in brain sections, protein alterations as a result of drug administration, and protein changes in brain due to neurodegeneration and tumor formation. Advantages of this technology and future challenges for its improvement are discussed.

Nanomanipulation-Coupled Matrix-Assisted Laser Desorption/ Ionization-Direct Organelle Mass Spectrometry: A Technique for the Detailed Analysis of Single Organelles

“…It is for these reasons that a different source for ionizing and analyzing extracted cellular content was desired, leading to the work presented here. MALDI mass spectrometry imaging (MALDI-MSI) has become revolutionary in mapping lipids [19], proteins [20], and other small molecules [21] in tissues, and additionally in combination with liquid chromatography [22]. However, its spatial resolution for single cell and organelle imaging has been limited by dispersement of analytes during spotting of matrix and laser spot size [23].…”

Desorption electrospray ionization imaging mass spectrometry of lipids in rat spinal cord

“…Matrix-assisted laser desorption/ ionization (MALDI) and secondary ion mass spectrometry (SIMS) imaging have been used extensively. MALDI imaging is applicable to large molecules such as proteins [33][34][35][36][37][38][39][40] and peptides and can provide a spatial resolution of 100 m [39]; experiments are typically conducted under high vacuum and after application of an organic matrix to the sample to assist in ionization. Although the method has been primarily applied to proteins, MALDI has seen increasingly wide use in the investigation of distributions of lipids [41- 48], drug molecules from tissue surfaces [49 -54], and in a variety of other applications [55,56].…”

Characterization of secreted proteins of 2-cell mouse embryos cultured in vitro to the blastocyst stage with and without protein supplementation

“…The generated peptides were extracted with 50 % acetonitrile/0.1 % formic acid, and dried before reconstituting in 0.1 % formic acid. The peptides were separated on a C18 column (ResPrep C18 column, Bellefonte, PA, USA) and subjected to nano high performance liquid chromatography (HPLC, Accella, Thermo Fisher) and electro spray ionization (ESI) tandem mass spectrometry (LC-ESI-MS-MS) with a linear trap quadrupole instrument (LTQ, Thermo Fisher Scientific, Waltham, MA) [10][11][12][13]. Tryptic peptides extracted from identical sectors of the same media categories were combined to increase the concentration of the peptides 3-fold prior to mass spectrometry on the LTQ.…”