Mass spectrometry imaging: a new vision in differentiating Schistosoma mansoni strains

Schistosomiasis is a neglected disease with large geographic distribution worldwide. Among the several different species of this parasite, S. mansoni is the most common and relevant one; its pathogenesis is also known to vary according to the worms' strain. High parasitical virulence is directly related to granulomatous reactions in the host's liver, and might be influenced by one or more molecules involved in a specific metabolic pathway. Therefore, better understanding the metabolic profile of these organisms is necessary, especially for an increased potential of unraveling strain virulence mechanisms and resistance to existing treatments. In this report, MALDI‐MSI and the metabolomic platform were employed to characterize and differentiate two Brazilian S. mansoni strains: males and females from Belo Horizonte (BH) and from Sergipe (SE). By performing direct analysis, it is possible to distinguish the sex of adult worms, as well as identify the spatial distribution of chemical markers. Phospholipids, diacylglycerols and triacylglycerols were located in specific structures of the worms' bodies, such as tegument, suckers, reproductive and digestive systems. Lipid profiles were found to be different both between strains and males or females, giving specific metabolic fingerprints for each group. This indicates that biochemical characterization of adult S. mansoni may help narrowing‐down the investigation of new therapeutic targets according to worm composition, molecule distribution and, therefore, aggressiveness of disease. Copyright © 2014 John Wiley & Sons, Ltd.     

Determination of heats of tautomerization nitrile-ketenimine by mass spectrometry

Tautomerism of some nitriles has been studied by mass spectrometry. The analysis of the corresponding mass spectra has allowed to assign some fragmentations to specific tautomers and to determine heats of tautomerization through temperature effects and electron energy studies. Experimental determinations are supported by theoretical calculations. The joint analysis of mass spectrometry and DFT-B3LYP data indicate that this tautomeric equilibrium can be studied by the experimental spectrometric strategy employed.     

Quantitative determination of the local structure of H2O on TiO2(1 1 0) using scanned-energy mode photoelectron diffraction

O 1s scanned-energy mode photoelectron diffraction has been used to determine the local structure of molecular water on TiO₂(1 1 0). The adsorption site is found to be atop five-fold coordinated surface Ti atoms, confirming the results of published total energy calculations and STM imaging. The Ti-O_w bondlength is found to be 2.21 ± 0.02 Å, much longer than Ti-O bondlengths in bulk TiO₂ and for the formate (HCOO-) species adsorbed on this surface. This is consistent with relatively weak bonding, and in general agreement with total energy calculations, although all of the published calculations yield bondlengths somewhat longer than the experimental value. Structural optimisation based on the photoelectron diffraction data also provides some information on the associated substrate relaxation. In particular, the bondlength of the five-fold coordinated surface Ti atom to the O atom directly below shows the same contraction (relative to the bulk) as is found for the clean surface, reinforcing the picture of rather weak bonding of the water to this same Ti surface atom.     

Mass spectrometry of beta-ketoesters. Some evidence of their tautomerism

Mass spectrometric evidence of tautomerism is reported for beta-ketoesters. The analysis of the corresponding mass spectra has allowed specific assignment of fragment ions to tautomers. The predictive value of this methodology is supported by the influence of substitution pattern of these compounds on these equilibria. Experimental data are strongly supported by Austin Model 1 semiempirical calculations indicating that mass spectrometry could be resourced as a tool for the investigation of tautomerism of neutral species in the gas phase.     

Synthesis of E-aryl ethenesulfonamides: a simple one-pot, two-step procedure from 1-hydroxy-1-arylalkanes

The unusual reactivity of 1-phenyl-1-ethanesulfonic acid in thionyl chloride was investigated. Mechanistic considerations led us to set up a new and efficient synthesis of E-arylethenesulfonamides starting from 1-hydroxy-1-arylalkanes. The easy availability of the starting materials and the straightforward, one-pot procedure make this process an attractive method for the preparation of these compounds currently largely employed in chemical and pharmaceutical fields.     

Surface‐Guided Formation of an Organocobalt Complex

Organocobalt complexes represent a versatile tool in organic synthesis as they are important intermediates in Pauson–Khand, Friedel–Crafts, and Nicholas reactions. Herein, a single‐molecule‐level investigation addressing the formation of an organocobalt complex at a solid–vacuum interface is reported. Deposition of 4,4′‐(ethyne‐1,2‐diyl)dibenzonitrile and Co atoms on the Ag(111) surface followed by annealing resulted in genuine complexes in which single Co atoms laterally coordinated to two carbonitrile groups undergo organometallic bonding with the internal alkyne moiety of adjacent molecules. Alternative complexation scenarios involving fragmentation of the precursor were ruled out by complementary X‐ray photoelectron spectroscopy. According to density functional theory analysis, the complexation with the alkyne moiety follows the Dewar–Chatt–Duncanson model for a two‐electron‐donor ligand where an alkyne‐to‐Co donation occurs together with a strong metal‐to‐alkyne back‐donation.     

Adsorption bond length for H2O on TiO2(110): a key parameter for theoretical understanding

Scanned-energy mode photoelectron diffraction results show the adsorption site of molecular water on TiO2(110) to be atop under-coordinated surface Ti atoms, confirming the results of total energy calculations and STM imaging. However, the Ti-O(water) bond length is 2.21 +/- 0.02 A, much longer than Ti-O bond lengths in strongly chemisorbed species on this surface, but significantly shorter than found in most total energy calculations. The need for theory to describe this weak bond effectively may be a key factor in the controversial problem of understanding this important surface reaction system.     

Tailor-made ultrathin manganese oxide nanostripes: 'magic widths' on Pd(1 1 N) terraces

The growth of ultrathin two-dimensional manganese oxide nanostripes on vicinal Pd(1 1 N) surfaces leads to particular stable configurations for certain combinations of oxide stripe and substrate terrace widths. Scanning tunneling microscopy and high-resolution low-energy electron diffraction measurements reveal highly ordered nanostructured surfaces with excellent local and long-range order. Density functional theory calculations provide the physical origin of the stabilization mechanism of 'magic width' stripes in terms of a finite-size effect, caused by the significant relaxations observed at the stripe boundaries.     

Cobalt oxide nanolayers on Pd(100): The thickness-dependent structural evolution

The growth of interface-stabilized cobalt oxide (CoO_x) nanolayers on Pd(100) has been investigated and their structures are reported as a function of coverage. Several different phases have been observed by LEED and STM experiments, and they have been characterized spectroscopically by photoemission and X-ray absorption. The data indicate that in the low coverage regime (up to Θ_Co ≈ 2–3 ML) rock-salt CoO type phases are formed (defective in the single layer regime, and stoichiometric in multilayers) with (100) or (111) termination. At higher coverage (Θ_Co ≈ 10–20 ML) spinel Co₃O₄(111) and CoO(100) layers have been detected, in ratios dependent on the preparation conditions. The observed structures are discussed in relation to similar structures reported recently for CoO_x films on Ir(100) [W. Meyer et al., J. Phys.: Condens. Matter 20 (2008) 265011].