Cardiolipin profile changes are associated to the early synaptic mitochondrial dysfunction in Alzheimer's disease.

Brain mitochondria are fundamental to maintaining healthy functional brains, and their dysfunction is involved in age-related neurodegenerative disorders such as Alzheimer's disease (AD). In this study, we conducted a research on how both non-synaptic and synaptic mitochondrial functions are compromised at an early stage of AD-like pathologies and their correlation with putative changes on membranes lipid profile, using 3 month-old nontransgenic and 3xTg-AD mice, a murine model of experimental AD. Bioenergetic dysfunction in 3xTg-AD brains is evidenced by a decrease of brain ATP levels resulting, essentially, from synaptic mitochondria functionality disruption as indicated by declined respiratory control ratio associated with a 50% decreased complex I activity. Lipidomics studies revealed that synaptic bioenergetic deficit of 3xTg-AD brains is accompanied by alterations in the phospholipid composition of synaptic mitochondrial membranes, detected either in phospholipid class distribution or in the phospholipids molecular profile. Globally, diacyl- and lyso-phosphatidylcholine lipids increase while ethanolamine plasmalogens and cardiolipins content drops in relation to nontransgenic background. However, the main lipidomic mark of 3xTg-AD brains is that cardiolipin cluster-organized profile is lost in synaptic mitochondria due to a decline of the most representative molecular species. In contrast to synaptic mitochondria, results support the idea that non-synaptic mitochondria function is preserved at the age of 3 months. Although the genetically construed 3xTg-AD mouse model does not represent the most prevalent form of AD in humans, the present study provides insights into the earliest biochemical events in AD brain, connecting specific lipidomic changes with synaptic bioenergetic deficit that may contribute to the progressive synapses loss and the neurodegenerative process that characterizes AD.

Identification of free radicals by spin trapping with DEPMPO and MCPIO using tandem mass spectrometry.

This study evaluates the use of a pyrroline (DEPMPO) and an imidazole (MCPIO) spin trap for the detection of hydroxyl and biomolecule (a peptide and a phospholipid) free radical adducts by Electrospray Ionization Mass Spectrometry (ESI-MS). The hydroxyl and biomolecule free radical adducts were detected using a QTOF and a linear ion trap (LIT) mass spectrometers. In the presence of hydroxyl radical, the mass spectrum obtained for each of the spin traps, DEPMPO and MCPIO, showed the presence of ions that could be attributed to hydroxyl and peroxyl radicals. Further characterisation by tandem mass spectrometry (ESI-MS/MS) revealed also the presence of hydroxy-hydroxyl adducts. Based on the results here described, we show that DEPMPO is a better spin trap for free radicals trapping and detection by mass spectrometry mainly because adducts show increased signal intensity. The ESI-MS spectra obtained for DEPMPO and MCPIO in the presence of biomolecule radicals (peptide and phospholipid) show molecular ions of DEPMPO and MCPIO adducts, which were characterised by tandem mass spectrometry. Both carbon centered radicals and oxygen centered radicals were efficiently trapped by the two spin traps and analysis of QTOF-MS/MS mass spectra allowed the location of the radical position in either the peptide or in the phospholipid fatty acyl chain. However, the tandem mass spectra of MCPIO adducts were more informative than DEPMPO adducts. The LIT-MS/MS spectra only shows typical peptide and phospholipid fragmentation, which difficult the structural characterisation of the spin adduct. In this study, the DEPMPO and MCPIO adducts were identified either in the nitrone or in the hydroxylamine form, which are ESR silent forms. The results described here show that both spin traps coupled with detection by mass spectrometry are valuable tools for trapping radicals of biomolecules. Furthermore, the acquired data provide valuable information on the presence of adducts (hydroxyl and biomolecule) that are Electron Spin Resonance (ESR) silent. This is especially important considering the complexity of the radical species in biological environment and the presence of reducing compounds that convert the spin adducts to silent ESR forms.

Detection and characterization of cyclic hydroxylamine adducts by mass spectrometry.

Two cyclic hydroxylamines (cHA) bearing pyrrolidine (CPH) and piperidine moieties (TMTH) were evaluated to trap hydroxyl, peptide and phospholipid free radicals using mass spectrometry for their detection. The cHA ionized as [M+H](+) ions, showing higher relative abundances when compared to the DMPO, probably due to higher ionization efficiency. In the presence of hydroxyl radicals, both cHA generated new ions that could be attributed to loss of (*)H and (*)CH(3), most likely deriving from decomposition reactions of the nitroxide spin adduct. Addition of cHA to Leucine-enkephalin and palmitoyl-lineloyl-glycerophosphatidylcholine free radicals promoted the formation of cHA biomolecule adducts, which were confirmed by MS/MS data. Results suggest that the cHA are not suitable for hydroxyl radical trapping but can be used for trapping biomolecule radicals, having the advantage, over the most used cyclic nitrones, of being water soluble. The biomolecule adducts identified by MS are ESR silent, evidencing the importance of MS detection.

A thieno-2H-chromene alpha-amino acid derivative: synthesis and photochromic properties.

[structure: see text] A new photochromic thieno-2H-chromene alpha-amino acid derivative was prepared by C-N palladium-catalyzed cross-coupling of a bromothieno-2H-chromene with the aminated aromatic side chain of the methyl ester of a N,N-diprotected amino acid. Its good photochromic properties demonstrated by flash photolysis and continuous irradiation indicate a possible application in ophthalmic lenses. It may also be inserted into peptides to give photoinduced reversible structural changes.

Electrospray tandem mass spectrometry of 2H-chromenes.

Several 2H-chromenes derived from carbazoles were analyzed by electrospray tandem mass spectrometry. The 2H-chromenes constitute an important class of compounds that exhibit photochromic activity. The fragmentation pathways of the protonated molecular species [M+H]+ were studied, and main fragmentation pathways of these compounds were identified. Fragmentation pathways of [M+D]+ ions were also studied in order to obtain information about the location of the ionizing proton or deuteron. It was found that the proton is not preferentially located on the nitrogen atom. The charge is preferentially located as a tertiary carbocation, resulting from the uptake of the proton (or deuteron) by the zwitterionic open structure of the chromenes. The major fragmentation occurred by cleavage of the gamma-bond relative to the carbocation center, leading to a fragment at m/z 191 (C5H11+ or C14H9N+), which are the most abundant fragment ions for almost all compounds. The presence of substituents in the chromene ring does not change this behavior. Other observed common fragmentation pathways included loss of CH3* (15 Da), loss of CO (28 Da), combined loss of CO and CH3 (43 Da), and loss of the phenyl ring via combined loss of C6H4 and CH3* (-91 Da) and combined loss of C6H6 and CO (-106 Da).