Direct analysis of fatty acid profile from milk by thermochemolysis-gas chromatography-mass spectrometry

The fatty acid composition of milk is of considerable interest due to their nutritional and functional properties. Although rapid milk fat separation and transesterification procedures have been developed, the overall procedure remains time consuming, specially, for the analysis of a large number of samples. In this work, a fast and simple method for direct profiling of fatty acids from milk using thermochemolysis has been developed. This method has the capability of directly analyse fatty acids from one drop of milk without fat extraction or cleanup. Our approach for thermochemolysis is based on thermal desorption integrated with a cold trap inlet. The optimized method does not present isomerisation/degradation of polyunsaturated fatty acid and shows milk fatty acid profiles comparable to the conventional method based on fat extraction and alkaline transesterification. Overall, this method has demonstrated significant potential for high throughput analysis of fatty acids in milk.     

Intramolecular hydroamination catalysis using trans-N,N′-dibenzylcyclam zirconium complexes

The syntheses of (Bn₂Cyclam)Zr(NMe₂)₂ (1), (Bn₂Cyclam)Zr(NH^2,6-MePh)Cl (2) and (Bn₂Cyclam)Zr(N^2,6-MePh) (3) are described. The reactivity of 1, 3, (Bn₂Cyclam)Zr(CH₂Ph)₂ (4) and ((C₆H₄CH₂)₂Cyclam)Zr (5) as hydroamination catalysts of aminoalkenes is reported. High conversions of the primary gem-disubstituted aminoalkenes in 5- or 6-member ring N-heterocycles were observed. Reactions of 1, 4 and 5 with CH₂CHCH₂CPh₂CH₂NH₂ gave (Bn₂Cyclam)Zr(NHR)₂ (6) (R = CH₂CPh₂CH₂CHCH₂) that on heating converts sequentially into the mono-ortho-metallated species ((C₆H₄CH₂)BnCyclam)Zr(NHR) (7) and the bis-ortho-metallated ((C₆H₄CH₂)₂Cyclam)Zr (5), simultaneously with the hydroamination product.     

Detection of altered extracellular matrix in surface layers of unstable carotid plaque: an optical spectroscopy, birefringence and microarray genetic analysis

Erosion and rupture of surface layers in atherosclerotic plaque can cause heart attack and stroke; however, changes in luminal surface composition are incompletely defined. Laser-induced fluorescence spectroscopy (LIFS), with limited tissue penetration, was used to investigate the surface of unstable carotid plaque and correlated with microscopy, birefringence and gene expression. Arterial matrix collagens I, III and elastin were assessed in unstable plaques (n = 25) and reference left internal mammary arteries (LIMA, n = 10). LIFS in addition to selective histological staining with picrosirius red, Movat pentachrome and immunostaining revealed decreased elastin and increased collagen I and III (P < 0.05) in carotid plaque when compared with LIMA. Within plaque, collagen I was elevated in the internal carotid region versus the common carotid region. Polarized light microscopy detected layers of aligned collagen and associated mechanical rigidity of the fibrous cap. Microarray analysis of three carotid and three LIMA specimens confirmed up-regulation of collagen I, III and IV, lysyl oxidase and MMP-12. In conclusion, LIFS analysis coupled with microscopy revealed marked regional differences in collagen I, III and elastin in surface layers of carotid plaque; indicative of plaque instability. Birefringence measurements demonstrated mechanical rigidity and weakening of the fibrous cap with complementary changes in ECM gene expression.     

Cryptococcus gattii: in vitro susceptibility to photodynamic inactivation

Cryptococus gattii is an emergent primary human pathogen that causes meningismus, papilledema, high intracranial pressure and focal involvement of the central nervous system in immunocompetent hosts. Prolonged antifungal therapy is the conventional treatment, but it is highly toxic, selects for resistant strains, contributes to therapy failure and has a poor prognosis. Photodynamic inactivation (PDI) offers a promising possibility for the alternative treatment of cryptococcosis. The aim of this study was to test the effectiveness of toluidine blue O (TBO) and light-emitting diode (LED) against C. gattii strains with distinct susceptibility profile to antifungal drugs (amphotericin B: 0.015-1.0 μg mL(-1); itraconazole: 0.015-2 μg mL(-1); fluconazole: 4-64 μg mL(-1)). Using 25 μM (6.76 μg mL(-1)) TBO and LED energy density of 54 J cm(-2) these fungal isolates presented variable susceptibility to PDI. The production of reactive oxygen species (ROS)/peroxynitrite was determined, and the catalase and peroxidase activities were measured. After PDI, high amounts of ROS/peroxynitrite are produced and higher catalase and peroxidase activities could be correlated with a lower susceptibility of C. gattii isolates to PDI. These results indicate that PDI could be an alternative to C. gattii growth inhibition, even of isolates less susceptible to classical antifungal drugs, also pointing to mechanisms related to their variable susceptibility behavior.     

Determination of parabens in shampoo using high performance liquid chromatography with amperometric detection on a boron-doped diamond electrode

Methylparaben (MePa), ethylparaben (EtPa) and propylparaben (PrPa) have been widely used, among others, as chemical preservatives in cosmetics, drugs and foods. As these compounds are linked with allergies, dermatitis and estrogenic properties, it is necessary to control the concentration of these substances in different matrices. The aim of this paper are: to evaluate the electrochemical behavior of parabens on the boron-doped diamond (BDD) electrode and the development of a chromatographic method, with electrochemical detection (HPLC-ED), for determination of parabens in shampoo. A BDD (8000 ppm) electrode was adapted in a thin layer mode analytical cell consisting of a stainless steel and a platinum wire as reference and auxiliary electrodes, respectively. Chromatographic separations were obtained with a reversed phase C8 analytical column and a mobile phase of 0.025 mol L⁻¹ disodium phosphate, pH 7.0, and acetonitrile (40:60, v/v), delivered at a flow rate of 1.0 mL min⁻¹. Sample preparation was performed by solid phase extraction using C18 cartridges and acetonitrile for elution. Benzylparaben was employed as internal standard. The HPLC-ED method developed, using the BDD electrode, was validated for the determination of parabens in shampoos and presented adequate linearity (>0.999), in the range of 0.0125-0.500% (w/w), detectability 0.01% (w/w), precision (RSD of 2.3-9.8%) and accuracy (93.1-104.4%) and could be applied for routine quality control of shampoos containing MePa, EtPa and PrPa.     

M?ssbauer spectroscopy for heavy elements: a relativistic benchmark study of mercury

The electrostatic contribution to the M?ssbauer isomer shift of mercury for the series HgF _n (n?=?1,?2,?4) with respect to the neutral atom has been investigated in the framework of four- and two-component relativistic theory. Replacing the integration of the electron density over the nuclear volume by the contact density (that is, the electron density at the nucleus) leads to a 10% overestimation of the isomer shift. The systematic nature of this error suggests that it can be incorporated into a correction factor, thus justifying the use of the contact density for the calculation of the M?ssbauer isomer shift. The performance of a large selection of density functionals for the calculation of contact densities has been assessed by comparing with finite-field four-component relativistic coupled-cluster with single and double and perturbative triple excitations [CCSD(T)] calculations. For the absolute contact density of the mercury atom, the Density Functional Theory (DFT) calculations are in error by about 0.5%, a result that must be judged against the observation that the change in contact density along the series HgF _n (n?=?1,?2,?4), relevant for the isomer shift, is on the order of 50?ppm with respect to absolute densities. Contrary to previous studies of the ⁵⁷Fe isomer shift (F Neese, Inorg Chim Acta 332:181, 2002), for mercury, DFT is not able to reproduce the trends in the isomer shift provided by reference data, in our case CCSD(T) calculations, notably the non-monotonous decrease in the contact density along the series HgF _n (n?=?1,?2,?4). Projection analysis shows the expected reduction of the 6s _1/2 population at the mercury center with an increasing number of ligands, but also brings into light an opposing effect, namely the increasing polarization of the 6s _1/2 orbital due to increasing effective charge of the mercury atom, which explains the non-monotonous behavior of the contact density along the series. The same analysis shows increasing covalent contributions to bonding along the series with the effective charge of the mercury atom reaching a maximum of around +2 for HgF₄ at the DFT level, far from the formal charge +4 suggested by the oxidation state of this recently observed species. Whereas the geometries for the linear HgF₂ and square-planar HgF₄ molecules were taken from previous computational studies, we optimized the equilibrium distance of HgF at the four-component Fock-space CCSD/aug-cc-pVQZ level, giving spectroscopic constants r _e = 2.007 ? and ?? _e = 513.5?cm^?1.     

Photofragmentation in selected tautomers of protonated adenine

The photofragmentation by UV excitation of selectively prepared 1(+) and 3(+) tautomers of protonated adenine is studied after excitation at a 266 and 263 nm wavelengths with two different experimental set-ups located in Seoul and Orsay. While the production of 1(+) tautomers with an electrospray ion source is now well accepted, calculations were used to ascribe the preparation of 3(+) tautomers from cold adenine dimers. The fragmentation patterns are rather similar for both tautomers, suggesting similar mechanisms as a statistical fragmentation in the ground electronic state after internal conversion.     

Outermost and inner-shell electronic properties of ClC(O)SCH2CH3 studied using HeI photoelectron spectroscopy and synchrotron radiation

A study of valence electronic properties of S-ethyl chlorothioformate (S-ethyl chloromethanethioate), ClC(O)SCH(2)CH(3), using HeI photoelectron spectra (PES) and synchrotron radiation is presented. Moreover, the photon impact excitation and dissociation dynamics of ClC(O)SCH(2)CH(3) excited at the S 2p and Cl 2p levels are elucidated by analyzing the total ion yield (TIY) spectra and time-of-flight mass spectra acquired in multicoincidence mode [photoelectron-photoion coincidence (PEPICO) and photoelectron-photoion-photoion coincidence (PEPIPICO)]. The HeI photoelectron spectrum is dominated by features associated with lone-pair electrons from the ClC(O)S- group, the HOMO at 9.84 eV being assigned to the n(π)(S) sulfur lone-pair orbital. Whereas the formation of C(2)H(5)(+) ion dominates the fragmentation in the valence energy region, the most abundant ion formed in both the S and Cl 2p energy ranges is C(2)H(3)(+). Comparison with related XC(O)SR (X = H, F, Cl and R = -CH(3), -C(2)H(5)) species reveals the impact of the alkyl chain on the photodissociation behavior of S-alkyl (halo)thioformates.