A neutralization-reionization and reactivity mass spectrometry study of the generation of neutral hydroxymethylene

Neutral hydroxymethylene HCOH is an important intermediate in several chemical reactions; however, it is difficult to observe due to its high reactivity. In this work, neutral hydroxymethylene and formaldehyde were generated by charge exchange neutralization of their respective ionic counterparts and then were reionized and detected as positive‐ion recovery signals in neutralization–reionization mass spectrometry in a magnetic sector instrument of BEE geometry. The reionized species were characterized by their subsequent collision‐induced dissociation mass spectra. The transient hydroxymethylene neutral was observed to isomerize to formaldehyde with an experimental time span exceeding 13.9 µs. The vertical neutralization energy of the HCOH^+? ion has also been assayed using charge transfer reactions between the fast ions and stationary target gases of differing ionization energy. The measured values match the result of ab initio calculations at the QCISD/6‐311 + G(d,p) and CCSD(T)/6‐311 + + G(3df,2p) levels of theory. Neutral hydroxymethylene was also produced by proton transfer from CH₂OH⁺ to a strong base such as pyridine, confirmed by appropriate isotopic labeling. There is a kinetic isotope effect (KIE) for H⁺ versus D⁺ transfer from the C atom of the hydroxymethyl cation of ～3, consistent with a primary KIE of a nearly thermoneutral reaction. Copyright © 2011 John Wiley & Sons, Ltd.     

Cyanide–Arene Meisenheimer Complex Generated in Electrospray Ionization Mass Spectrometry Using Acetonitrile as a Solvent

The C – C bond formation activated under negative electrospray ionization of an acetonitrile solution of 1,3,5-trinitrobenzene is reported. The solvent function is to provide a source of cyanide ion, a highly problematic reagent, which is found to attack the electron-deficient aromatic ring to form a covalently bound anionic complex (Meisenheimer complex). The structure of the complex is elucidated by means of collision induced dissociation mass spectrometry and IR multiple photon dissociation spectroscopy in the ‘fingerprint’ region.

Metal containing nanosized systems for MR-Molecular Imaging applications

This review aims at assessing the role of nanosized systems as MR-imaging reporters in Molecular Imaging applications.The possibility of delivering a high number of imaging agents at the target of interest appears the solution of choice to overcome the drawback associated with the low sensitivity of the MRI approach. The use of metal-based particles entered very early in the armoury of MRI contrast agents with the Superparamagnetic Iron Oxides’ family that are still among the most sensitive systems. The review devotes much attention to the design and use of self-assembled systems based on lipophilic molecules, reporting examples taken by products and processes developed in the authors’ laboratory. The imaging reporters are invariantly represented by highly stable lanthanide(III) complexes. In general, whether is the paramagnetic lanthanide(III) ion, the particles act as T₂-susceptibility agents, whose contrasting abilities increase by increasing the magnetic field strength. In the case of Gd(III)-complexes, the systems mainly act as T₁-relaxation agents, whose efficiency is eventually enhanced by the long reorientational time of the supramolecular aggregate. In addition to tackle sensitivity issues, such systems may also be designed in order to become responsive to a specific physical or biochemical parameter of the microenvironment in which they distribute. Moreover, nanosized carriers for Gd(III)-complexes based on naturally occurring systems (apoferritin and lipoproteins) have also been considered for targeting specific epitopes on diseased cells.Finally, liposomes have been exploited to generate a novel class of highly sensitive CEST (Chemical Exchange Saturation Transfer) agents dubbed LIPOCEST. Such systems are characterized by a shifted resonance for the large pool of water molecules entrapped in the liposomal cavity that can be selectively irradiated in order to transfer saturated magnetization to the bulk water signal.     

Synthesis of some oligopyridine-galactose conjugates and their metal complexes: a simple entry to multivalent sugar ligands

Some galactose-oligopyridine conjugates were readily assembled by combining differently functionalized oligopyridines with peracetylated galactose derivatives. Variation in the structure of the components and of the linkers employed for their connection afforded adducts of different size, shape, and conformational mobility. Complexation of the bipyridine ligands with CuOTf and of the terpyridine ligand with Zn(OTf)₂ afforded the corresponding peracetylated 2:1 and 1:1 complexes, respectively, as single species. Their structures were determined to be tetrahedral (Cu complexes) and trigonal-bipyramidal (Zn complex), on the basis of spectroscopic evidence. Removal of the acetyl protecting groups from the ligands afforded the corresponding polyols. The terpyridine-Zn(II) complex, unlike the bipyridine-Cu(I) complexes maintained their structures upon removal of the acetyl protecting groups.     

Ultrastructural and functional characterization of circulating hemocytes from the freshwater crayfish Astacus leptodactylus: cell types and their role after in vivo artificial non-self challenge

The freshwater crayfish Astacus leptodactylus (Eschscholtz, 1823) is an important aquacultured decapod species as well as an invasive species in some European countries. In the current investigation we characterized the different classes of circulating blood cells in A. leptodactylus by means of light and electron microscopy analysis and we explored their reaction to different latex beads particles in vivo by total and differential cell counts at 0.5, 1, 2 and 4h after injections. We identified hemocytes by granule size morphometry as hyaline hemocytes with no or rare tiny granules, small granule hemocytes, unimodal medium diameter granule hemocytes and both small and large granule containing hemocytes. The latter granular hemocytes showed the strongest phenoloxidase l-DOPA reactivity both in granules and cytoplasm. A. leptodactylus respond to foreign particles with strong cellular immune responses. All treatments elicited a total hemocyte increase with a conspicuous recruitment of large granule containing hemocytes. All hemocyte types mounted some phagocytic response but the small granule hemocytes were the only ones involved in phagocytic response to all foreign particles with the highest percentages. These results (1) depict the variability in decapod hemocyte functional morphology; (2) identify the small granule hemocyte as the major phagocytic cell; (3) suggest that the rather rapid recruitment of large granule hemocyte in all treatments plays a relevant role by this hemocyte type in defense against foreign particles, probably in nodule formation.     

Direct quantitative evaluation of complex substances using computer screen photo-assisted technology: the case of red wine

The combination of computer monitors and webcams has been recently demonstrated to behave as a sort of spectrophotometer able to classify and recognize substances according to their light absorption and emission properties. This measurement technique is known as computer screen photoassisted technique (CSPT).In this paper, it is demonstrated for the first time and in the case of a complex sample such as red wine, that also quantification of integral parameters (colour indicators) and specific compounds (total anthocyanins and polyphenols) is possible through a multivariate analysis of CSPT fingerprints. Most of the properties of the method are due to the combination of light emission and absorption properties that are captured by the CSPT platform. Thanks to this combination, a CSPT fingerprint may contain a comparable amount of information with respect to standard spectrophotometers.Wine measurements were performed on intact samples without the intervention of chemical mediators. The regression models, built by Partial Least Squares, obtained errors of estimation of colour parameters, total polyphenols and anthocyanines that are comparable with those typical of the standard methods in use.Since computation functionalities, video capture and display are embedded in a steadily growing number of ubiquitously distributed equipments (from portable computers to cellular phones), these results indicate a viable methodology for low-cost and largely diffused analytical capabilities.     

Compound I of naked heme (iron protoporphyrin IX)

Gaseous iron protoporphyrin IX (heme) ions, Fe(PP-IX)+, obtained by electrospray ionization of a methanol solution of hemin chloride, are allowed to react with ozone, forming a species that is tentatively assigned the structure of an oxo complex, namely, an oxo iron(IV) protoporphyrin IX radical-cation species, (PP-IX).+FeIV=O. This species, representing the naked core of the putative active oxidant (compound I) of heme enzymes, is characterized by its reactivity behavior in Fourier transform ion cyclotron resonance mass spectrometry, performing as an active O-atom donor. A quite distinct reactivity is displayed by an isomeric species, holding the additional oxygen on the porphyrin frame, Fe(PP-IX(O))+. This isomer undergoes a ligand addition process, as was previously observed for Fe(PP-IX)+.