Matrix-assisted laser desorption/ionization-imaging mass applications

Sugiura Y, Shimma S, Setou M. Two-step matrix application technique to improve ionization efficiency for matrix-assisted laser desorption/ionization in imaging mass spectrometry. Anal. Chem. 2006 78 8227-8235. 

In Chapter 4, titled Principles of Mass Spectrometry Imaging Applicable to Thin-Layer Chromatography, the authors first introduce a budding analytical approach known as imaging mass spectrometry (IMS) strategy and then present some successful examples of its practical applications. Then, they introduce in detail three mass spectrometric techniques as those routinely used within the framework of IMS. These are secondary mass spectrometry (SIMS), matrix-assisted laser desorption/ ionization (MALDI-IMS), and desorption electrospray ionization (DESI). Finally, the authors discuss the advances and bottlenecks of these techniques when applied to TLC. 

Matrix-assisted laser desorption ionization (M ALDI) has also been used for TLC/MS by Gusev et al. (61). Absolute detection limits of 2-4 ng were demonstrated for bradykinin, angiotensin, and enkephalin derivatives. Application of the MALDI support matrix to the TLC plate after separation is completed induces a planar diffusion of 1-1.5 mm. In an interesting application of the MALDI TLC/MS method, the mass spectra of ninhydrin-stained spots were obtained. Ions corresponding to the ninhydrin adducts with the sample molecules could be observed. A spatially resolved image for bradykinin on a TLC plate in a 2-(4-hydroxyphenylazo) benzoic acid matrix was also reported in this paper. 

The use of silver nanoparticles has also been described in matrix-assisted laser desorption/ionization (MALDI), a powerful laser-based soft ionization technique for mass spectrometric analysis and the investigation of peptides, proteins, nucleic acids, pharmaceuticals, bacterial characterization and imaging studies. Here, liquid-liquid microextraction base-modified silver nanoparticles were employed for the extraction of a hydrophobic peptide (gramicidin) from biological samples through hydrophobic interactions, prior to MALDI analysis (Figure 4.1) [41]. The application of silver nanoparticles was shown to provide an excellent sample cleanup procedure, and also assisted in the enhancement of signal of peptides and proteins. 

Sugiura, Y. Shimma, S. Setou, M. Two-Step Matrix Application Technique To Improve Ionization Efficiency for Matrix-Assisted Laser Desorption/Ioni-zation in Imaging Mass Spectrometry. Anal. Chem. 2006, 78.8227-8235. 

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