Matrix-assisted laser desorption/ionization description

Mass spectrometry methods based on soft ionization techniques, 59,61,88,89 matrix-assisted laser desorption ionization/time-of-flight (MALDI-TOF), have been successfully applied for the direct analysis of grape and wine extracts and for monitoring flavonoid reactions in model solution studies. They give access to the molecular weights of the different species present in a fraction or extract and, through fragmentation patterns, provide important information on their constitutive units. Description of the various MS techniques can be found in Chapters 1 and 2. 

In the proteomic analysis of the brain, two-dimensional gels for protein separation, followed by matrix-assisted laser desorption ionization time-of-flight mass spectrometry for protein identification, have mainly been employed. This classical proteomics approach allows for the quantification of changes in protein levels and modifications. Simultaneously, it is a robust, well-established method that finds wide application in the study of biological systems. In this article, we provide a description of the protocols of the proteomic analysis used in our laboratory and a summary of the major findings from our group and other neuroproteomics groups. 

This section will cover the two most popular ionization techniques for analyzing proteins by mass spectrometry electrospray ionization (ESI) and matrix-assisted laser desorption ionization (MALDI). A brief description of five common mass spectrometers that have been coupled to these ion sources will follow. 

The methods most widely in use now for understanding and monitoring chemical processes that affect our environment and the atmosphere are those of TDLAS, and remote absorption/Raman spectroscopy based on lidar (absoiption-Hdar/ Raman-lidar). Application examples of these two techniques are outlined in Sections 28.1—28.3 and Sections 28.4-28.6 respectively. The chapter will conclude with the description of some less-developed techniques, which, however, provide information not easily obtained, or not accessible at all. All of them are based on ionization in one form or other, and include laser-induced breakdown spectroscopy (LIBS), matrix-assisted laser desorption ionization (MALDl) and aerosol TOFMS (ATOFMS). Examples of these are provided in Section 28.7. 

This review provides an up-to-date overview of the application of analytical procedures based on MS for the characterization of organic natural materials in archaeological and historical objects. Applications that feature the use of gas chromatography/mass spectrometry (GC/MS), Py-GC/MS, high performance liquid chromatography combined with mass spectrometry (HPLC/MS), and direct MS analysis such as matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS), electrospray ionization mass spectrometry (ESI-MS), and direct exposure mass spectrometry (DE-MS) are sununarized to highlight the different information provided by each of the various analytical approaches. Case studies and examples are also presented and include a description of the molecular markers and of the molecular profiles that are used to identify the original materials. 

Currently, there are at least three ionization techniques routinely used in IMS (1) secondary ion mass spectrometry (SIMS), (2) matrix-assisted laser desorption ionization (MALDI), and (3) desorption electrospray ionization (DESI). Each of these ion sources has their own advantages and drawbacks thus, they are usually selected in the context of the imaged sample. In the following text, we provide a concise description of these devices. 

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