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Ion-molecule reactions between the α-phenylvinyl cation (α-PVC) and mono-substituted benzenes have been investigated using a quadrople ion-trap mass spectrometer. The α-PVC, generated by chemical ionization from phenylacetilene, was found to react selectively with mono-substituted benzenes bearing electron withdrawing groups to give the product ions [M + 103](+) and the trans-vinylating product ions [M + 25](+). To characterize the reaction products, a combination of collision-induced dissociation, isotope-labeling experiments and model compounds were used. The results indicate, in addition to direct heteroatom alkylation, high extent of ortho attack. We attributed the positional selectivity of the α-PVC to the nature of the substituent on the neutral molecule. In particular, hydroxy and amino groups promoted the alkenylation at ortho position., (Copyright © 2011 John Wiley & Sons, Ltd.)

Tandem mass spectrometry has been applied to differentiate three sets of o-, m- and p-methyl, -methoxy and -nitro-substituted-6-phenyl-dibenzo(d,f)(1,3)dioxepines. Collision-induced dissociation (CID) experiments have been carried out on 2-phenylbenzo[b]furan fragment ions, which originate from the decomposition of the molecular ions after their EI-induced isomerization to spirocyclic structures. With the exception of m- and p-methylphenylbenzo[b]furan isomers, which display identical CID mass spectra, the three isomeric methoxy- and nitrophenylbenzo[b]furan fragment ions display very characteristic CID behavior which allows unequivocal differentiation of the 6-phenyl-dibenzo(d,f)(1,3)dioxepine isomers. 6-(o-nitrophenyl)-dibenzo(d,f)(1,3)dioxepine isomer, does not form a 2-(o-nitrophenyl)benzo[b]furan ion and, therefore, it can be differentiated from the m- and p- isomers based on the mere EI mass spectra. Furthermore, it shows a characteristic ion most likely due to an ortho effect between the nitro group and the dioxepine ring. Multiple stage mass spectrometric techniques (MSn), labeled derivatives and reference compounds were used in order to gain additional information on the structures of product ion from the CID fragmentation., (Copyright (c) 2008 John Wiley & Sons, Ltd.)

The mass spectrometric behaviour of a series of 6,6-disubstituted dibenzo(d,f)(1,3)dioxepine derivatives have been studied. The fragmentation patterns were described and discussed in detail with the aid of labelled compounds, accurate mass measurements and collisionally induced dissociation experiments performed using an ion trap.

The distribution of m1-m4 muscarinic acetylcholine receptors was investigated by immunolight and electron microscopy in rat dorsal root ganglia, by using subtype-specific antibodies. The light microscopic observations show that both the intensity and the localisation of immunolabeling of the four muscarinic subtypes are different. The m2 receptor is the most represented; m2 and m4 receptor proteins are principally expressed in the small-medium type neurones, while m1 and m3 receptor proteins are more homogeneously distributed among the neuronal population of the ganglion. On the contrary, there are no relevant differences in the subcellular distribution. Ultrastructural analysis shows that immunolabeling is associated with the Nissl bodies, budding Golgi cisterns, and as far as the m2 receptor is concerned, just beneath the plasmalemma with discrete loci along the neuronal plasma membrane. Unmyelinated nerve fibres are always immunopositive for all muscarinic receptor subtypes, suggesting an active transport for all subtypes. Occasionally perineuronal satellite cells surrounding large neurones are immunopositive for the m2 receptor, while both myelinating and non-myelinating Schwann cells faintly express all muscarinic receptor subtypes. These observations, together with previous data concerning pharmacological and functional characterisation of muscarinic acetylcholine receptors in dorsal root ganglion, suggest that sensory neurones are able to respond to acetylcholine. The presence of m2 and m4 immunoreactivity in the small type neurones and in their fibres involved in nociceptive response, suggest that these receptors may participate in the modulation of transduction of noxious stimuli from the periphery to the spinal cord. m1 and m3 receptors, having a more homogeneously distribution, may be involved in transduction of different kinds of stimuli.