Pulsed Blue Laser Diode Thermal Desorption Microplasma Imaging Mass Spectrometry.

An ambient air laser desorption, plasma ionization imaging method is developed and presented using a microsecond pulsed laser diode for desorption and a flexible microtube plasma for ionization of the neutral desorbate. Inherent parameters such as the laser repetition rate and pulse width are optimized to the imaging application. For the desorption substrate, copper spots on a copper-glass sandwich structure are used.

LMD proteomics provides evidence for hippocampus field-specific motor protein abundance changes with relevance to Alzheimer's disease.

Background: Human hippocampal area Cornu Ammonis (CA) 1 is one of the first fields in the human telencephalon showing Alzheimer disease (AD)-specific neuropathological changes. In contrast, CA2 and CA3 are far later affected pointing to functional differences, which may be accompanied by differences in proteome endowment and changes.

Methods: Human pyramidal cell layers of hippocampal areas CA1, CA2, and CA3 from neurologically unaffected individuals were excised using laser microdissection.

Strategies for nonradioactive methods in the localization of phosphorylated amino acids in proteins.

Identification of O-phosphorylated amino acids within the primary structure of regulatory proteins is important in understanding the mechanisms by which their functions are regulated. In many cases radioactive labeling with [32P]phosphate is tedious or sometimes impossible. Therefore, we have established a series of new non-radioactive methods that permit the localization of phosphoserine, phosphothreonine, and phosphotyrosine.

Farnesylcysteine, a constituent of the alpha and beta subunits of rabbit skeletal muscle phosphorylase kinase: localization by conversion to S-ethylcysteine and by tandem mass spectrometry.

The primary structure of the alpha and beta subunits of phosphorylase kinase reveals that both proteins contain a carboxyl-terminal CA1A2X motif (where C is cysteine, A1 and A2 are aliphatic amino acids, and X is an uncharged amino acid), the recognition signal for a protein polyisoprenyltransferase. The product, a polyisoprenylated cysteine, can be detected by phenylthiocarbamoylamino acid analysis and by microsequencing following conversion to S-ethylcysteine. Mass spectrometry confirms a covalently linked farnesyl residue in both subunits.