Integrable derivations and formal groups in unequal characteristic

In this paper we study the link between formal group of dimension one and integrable derivations of a ring of unequal characteristic. Partially supported by M.U.R.S.T. (60%) and members of C.N.R.-G.N.S.A.G.A.     

Affinity of Tripodal and Linear Tetraamines for Silver(I) in Dimethyl Sulfoxide

The thermodynamic functions of the complexation of Ag(I) by the tripodal ligands, tris(2-(methylamino)ethyl)amine (Me₃tren) and tris(2-(dimethylamino)ethyl)amine (Me₆tren) (L), are determined in dimethyl sulfoxide (DMSO) by potentiometric and calorimetric techniques at 298.0 K and 0.1 mol⋅dm⁻³ ionic strength (Et₄NClO₄). A comparison is made between previous data concerning Ag(I) complex formation with the non-alkylated tripodal 2,2′,2″-triaminotriethylamine (tren), in order to analyze the influence of N-methylation on this type of branched donor, and with those relative to the linear triethylenetetramine (trien) and 1,1,4,7,10,10-hexamethyltriethylenetetramine (Me₆trien). The results are discussed taking into account different σ-donating properties, geometric arrangement of the ligands, steric repulsions and solvation effects.     

Development of a new analytical method for the determination of fumonisins B1 and B2 in food products based on high performance liquid chromatography and fluorimetric detection with post-column derivatization

A sensitive and selective analytical method was developed for the quantitative determination of fumonisins B(1) and B(2) in maize-based foods for direct human consumption. The method, based on high-performance liquid chromatography and fluorescence detection, presents a rapid and automated on-line post-column derivatization, performed with o-phtalaldehyde and N,N-dimethyl-2-mercaptoethylamine. Several factors affecting the separation and detection of fumonisins were investigated, including mobile phase composition, column features, derivatization agent flow-rate and both the excitation and the emission wavelengths. Optimal fluorescence detection was obtained by using a lambda(exc) of 343 nm and a lambda(em) of 445 nm. Under the optimized experimental conditions, a complete separation of fumonisins was obtained in less than 13 min by using a C(18) column and a gradient elution at 0.8 mL/min with methanol and 0.1M phosphate buffer at pH 3.15. The limits of detection for FB(1) and FB(2) were 4 and 5 microg/L corresponding to 5 and 6 microg/kg in matrix. Each fumonisin was determined in the range 40-320 microg/L that correspond to 50-400 microg/kg in matrix. The necessary requirements for accuracy, reproducibility and sensitivity were fulfilled and recovery values ranged from 87 to 94% for FB(1) and from 70 to 75% for FB(2) in cornflake samples at three fortification levels in the range 100-300 microg/kg. The potential of this method, combined with a simple clean-up procedure, was assessed by the measurements of FB(1) and FB(2) in maize-based products, such as maize flour, "polenta", tortillas and cookies.     

Assessment of protein-incorporated arginine methylation in biological specimens by CZE UV-detection

Protein arginine methyltransferases methylate post-translationally arginine residues in proteins to synthesize monomethylarginine (MMA), asymmetric dimethylarginine (ADMA), or symmetric dimethylarginine. Protein arginine methylation is involved in the regulation of signal transduction, RNA export, and cell proliferation. Moreover, upon proteolysis, arginines are released into the cytosol in which they exert important biological effects. Both MMA and ADMA are inhibitors of nitric oxide synthase and especially elevated levels of ADMA are associated with endothelial dysfunction and cardiovascular disease. Quantification of these analytes is commonly performed by HPLC after sample cleanup and derivatization. We propose a CE method in which these steps have been avoided and the procedure for sample preparation has been simplified. After acidic hydrolysis of proteins, samples were dried, resuspended in water, and directly injected in CE. A baseline separation of analytes was reached in a 60 cm x 75 microm id uncoated silica capillary, by using a Tris-phosphate run buffer at pH 2.15. This method allows an accurate assessment of protein arginine methylation degree in different biological samples such as whole blood, plasma, red blood cells, cultured cells, and tissue. Moreover, its good sensitivity permits to evaluate the methylation of a single protein type after the opportune purification steps. A method applicability concerns both clinical laboratories, where the evaluation of blood protein from numerous samples could be rapidly performed, and research laboratories where the factors affecting the arginine protein methylation degree could be easily studied.     

trans-W(Cmesityl)(dmpe)2H: revealing a highly polar W-H bond and H-mobility in liquid and solid state

The isotopomeric complexes trans-W(Cmesityl)[(C(H,D)3)2PCH2CH2P(C(H,D)3)2]2(H,D) 1-4 were prepared. 2 (W(Cmesityl)(dmpe)2D) was used to study the Deuterium Quadrupole Coupling Constant (DQCC) and the ionicity of the W-D bond (DQCC=34.1 kHz; ionicity 85%). 1 (W(Cmesityl)(dmpe)2H) shows several dynamic exchange processes in solution, such as HW/HW, HW/ortho-Memesityl, and HW/H2 exchanges observed by NMR in combination with deuterium labeling studies and double label crossover experiments. Except for the HW/H2, these reactions comprise elementary steps, which also appear along the isomerization pathway of 1 into (2,3,5-trimethylphenylcarbyne)(dmpe)2WH (5) at 60 degrees C. 5 was characterized by an X-ray diffraction study. In the solid state only an HW/Mep exchange process prevails appearing at higher temperatures, which was identified by NMR and by Quasielastic Neutron Scattering. The latter also provided an activation barrier of 5 kcal/mol and a "jump width" for the moving H nucleus in agreement with the HW...Mep distance of the X-ray diffraction study of 1.     

Retention indices in the analysis of food aroma volatile compounds in temperature-programmed gas chromatography: database creation and evaluation of precision and robustness

A retention index (RI) database containing 250 volatile compounds was created on a polar stationary phase column and validated for food aroma characterisation. Precision of the retention indices (RIs) was assessed by performing replicated injections of a representative number of volatiles under the same experimental conditions: differences lower than 1 U were observed for all the compounds. Robustness was evaluated by carrying out injections of the same set of volatile compounds under different experimental conditions, i.e. program temperature, column batches and instrumentation. Excellent results were obtained with a maximum difference in the RI values of 10 U. The capabilities of the created database for food aroma characterisation were finally evaluated by analysing the volatile fractions of different food matrices such as dry sausages, cheese and bread. A great number of volatile compounds were identified in the analysed samples on the basis of their RI, thus proving the usefulness of the RI collections in the field of food analysis.     

Determination of the oxidation stability of biodiesel and oils by spectrofluorimetry and multivariate calibration

Oxidation stability is an important quality parameter for biodiesel. In general, the methods used to evaluate the oxidation stability of oils and biodiesels are time-consuming. This work reports the use of spectrofluorimetry, a fast analytical technique, associated with multivariate data analysis as a powerful analytical tool to prediction of the oxidation stability. The prediction of the oxidation stability showed a good agreement with the results obtained by the EN14112 reference method Rancimat. The models presented high correlation (0.99276 and 0.97951) between real and predicted values. The R² values of 0.98557 and 0.95943 indicated the accuracy of the models to predict the oxidation stability of soy oil and soy biodiesel, respectively. The residual distribution does not follow a trend with respect to the predicted variables indicating the good quality of the fits.     

OFFgel-based multidimensional LC-MS/MS approach to the cataloguing of the human platelet proteome for an interactomic profile

The proteome of quiescent human platelets was analyzed by a shotgun proteomics approach consisting of enzymatic digestion, peptide separation based on isoelectric point by the use of OFFgel fractionation and, finally, RP nanoscale chromatography coupled to MS/MS detection (nano-LC-MS/MS). OFFgel fractionation in the first dimension was effective in providing an additional dimension of separation, orthogonal to RP nano-LC, thus generating an off-line multidimensional separation platform that proved to be robust and easy to set up. The analysis identified 1373 proteins with high confidence (false discovery rate<0.25%). The core set of 1373 human platelet proteins was investigated by Ingenuity Pathway Analysis software from which ten canonical pathways and eight networks have been validated, to suggest that platelets behave either as inflammatory or immune cells, and plasma membrane and cytoskeleton proteins play a fundamental role in their function. Moreover, toxicity pathway in agreement with network analysis, supports the concept that platelet life span is governed by an apoptotic mechanism.     

Nickel(II) 3,4;9,10-perylenediimide bis-phosphonate pentahydrate: a metal-organic ferromagnetic dye

The new metal-organic compound nickel(II) 3,4;9,10-perylenediimide bis-phosphonate pentahydrate, i.e. Ni(2)[(PDI-BP)(H(2)O)(2)]·3H(2)O (1), has been synthesized and its structural and magnetic properties have been studied. Reaction of 3,4;9,10-perylenediimide bis-phosphonate (PDI-BP, hereafter) ligand and nickel chloride in water resulted in the precipitation of a red and poorly crystalline solid (1). As the solid shows a poor crystalline organization of aggregates, the energy dispersive X-ray diffraction analysis (EDXD) technique has been used to obtain short-range order structural information of the single nanoaggregates by radial distribution function analysis. The overall structure of the compound is characterized by layers containing perylene planes shifted in the direction perpendicular to the stacking axes in such a way that only the outer rings overlap. The edges of the perylene planes are connected to the phosphonate groups through an imido group. The oxygen atoms of the [-PO(3)](2-) group and those of the water molecules are bonded to the nickel ions resulting in a [NiO(6)] octahedral coordination sphere. The Ni-O bond lengths are 0.21 ± 0.08 nm and the Ni-O-Ni angles of aligned moieties are 95 ± 2°. The oxygen atoms of the water molecules and the nickel atoms are nearly planar and almost perpendicular to the perylene planes forming chains of edge-sharing octahedra. The magnetic properties of (1) show the presence of intrachain ferromagnetic Ni-Ni interactions and a long-range ferromagnetic order below 21 K with a canting angle and with a spin glasslike behavior due to disorder in the inorganic layer. Hysteresis cycles show a coercive field of ca. 272 mT at 2 K that decreases as the temperature is increased and vanishes at ca. 20 K.