Two-dimensional graphene as a novel matrix for MALDI imaging mass spectrometry and biological mass spectrometry
Friesen, William L.
MetadataShow full item record
Mass spectrometry (MS) is a collection of techniques capable of determining the mass-to-charge ratio of ions and has a multitude of applications. Imaging mass spectrometry (IMS) is a technique that involves collection of mass spectra across the plane of a sample, assigning one mass spectrum to each pixel of an image, forming a map of ion intensities. Matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS), a very common ionization source for IMS, requires the use of a matrix to aid in the ionization of analyte molecules; however, their large crystals interfere with efforts to optimize spatial resolution and the solvents used in their application can result in analyte migration. Two-dimensional graphene sheets, which consist of an electrically and thermally conductive honeycomb lattice of sp 2 hybridized carbon, make an effective substitute for conventional MALDI matrices in many cases. The use of graphene remedied a number of issues, as it is applied without the use of solvents and allows the instrumental limits in spatial resolution to be achieved. Despite graphene’s interesting electrical properties, electron transfer appears to a minor channel for ionization, favoring cationization instead. In another application of mass spectrometry, MALDI-MS was used in the analysis of tryptic digests of Histones H3 and H4 following treatment with an arsenic compound. Central to the synthesis and structure of genetic material, Histones displaying abnormal modifications are suspected in the development of a number of cancers. Histones exposed to arsenic displayed altered modifications, particularly acetylation on certain lysine residues and methylation of a methionine, compared to the control. Future work will involve further application of graphene in actual imaging experiments and further exploring which molecule classes are ionized with graphene. Further experiments with arsenic-exposed histones will include statistical analysis and complimenting MALDI-MS analysis with electrospray ionization mass spectrometry.