Analytical Methods for the Characterization of Vegetable Oils

The determination of the authenticity of extra virgin olive oils (EVOOs) has become more interesting in recent years. Italy is the first country in Europe in terms of number of Protected Designation of Origin (PDO) oils, which connects consumers to a feeling of tradition and thus to higher quality standards. This work focused on the consideration of the inorganic content as a possible marker of EVOOs. Ten vegetable oils (VOs), eight Italian EVOOs and seven not Italian EVOOs were analyzed. After pretreatment by acid mineralization, Al, Ba, Ca, Cu, Fe, K, Li, Mg, Mn, Na, P, Sb, Se and Zn were determined by ICP-OES. The electrochemical properties of a selected group of EVOOs and other vegetal oils of different botanical origin were investigated by voltammetry. Carbon paste electrodes (CPEs) were prepared. The features observed in the voltammograms reflect the reactions of electroactive compounds, which are present in the oils. A chemometric treatment of the results was performed to assess the possibility to distinguish (i) the region of provenience considering the inorganic profile; and (ii) the plant species from which each oil was obtained on the basis of the current profile registered during voltammetric analysis. Inorganic composition seems to be a useful marker for the assessment of the geographical origin of an EVOO. The EVOO-CPEs voltammetry seems to have a good ability to distinguish the plant species of origin. This method could be useful to monitor the conservation status of the oils, as the redox profile is linked to the oxidative degradation state.     

Sharp Asymptotics for the Partition Function of Some Continuous-time Directed Polymers

This paper is concerned with two related types of directed polymers in a random medium. The first one is a d-dimensional Brownian motion living in a random environment which is white-noise in time and homogeneous in space. The second is a continuous-time discrete-space Markov process on ℤ ^d , in a random environment with similar properties as in continuous space, albeit defined only on . The case of a space-time white noise environment can be achieved in this second setting. By means of some Gaussian tools, we estimate the free energy of these models at low temperature, and give some further information on the strong disorder regime of the objects under consideration. Frederi Viens’ research partially supported by NSF grants no.: DMS 0204999 and DMS 0606615.     

Excited-state absorption and ultrafast relaxation dynamics of porphyrin, diprotonated porphyrin, and tetraoxaporphyrin dication

The relaxation dynamics of unsubstituted porphyrin (H2P), diprotonated porphyrin (H4P2+), and tetraoxaporphyrin dication (TOxP2+) has been investigated in the femtosecond-nanosecond time domain upon photoexcitation in the Soret band with pulses of femtosecond duration. By probing with spectrally broad femtosecond pulses, we have observed transient absorption spectra at delay times up to 1.5 ns. The kinetic profiles corresponding with the band maxima due to excited-state absorption have been determined for the three species. Four components of the relaxation process are distinguished for H2P: the unresolvably short B --> Qy internal conversion is followed by the Qy --> Qx process, vibrational relaxation, and thermalization in the Qx state with time constant approximately 150 fs, 1.8 ps, and 24.9 ps, respectively. Going from H2P to TOxP2+, two processes are resolved, i.e., B --> Q internal conversion and thermal equilibration in the Q state. The B --> Q time constant has been determined to be 25 ps. The large difference with respect to the B --> Qy time constant of H2P has been related to the increased energy gap between the coupled states, 9370 cm-1 in TOxP2+ vs 6100 cm-1 in H2P. The relaxation dynamics of H4P2+ has a first ultrafast component of approximately 300 fs assigned as internal conversion between the B (or Soret) state and charge-transfer (CT) states of the H4P2+ complex with two trifluoroacetate counterions. This process is followed by internal CT --> Q conversion (time constant 9 ps) and thermalization in the Q state (time constant 22 ps).     

Relaxation properties of porphyrin, diprotonated porphyrin, and isoelectronic tetraoxaporphyrin dication in the S2 state

The fluorescence spectra of unsubstituted porphyrin (H2P), diprotonated porphyrin (H4P2+), and isoelectronic tetraoxaporphyrin dication (TOxP2+) have been measured in solution at room temperature. The S2-->S0 fluorescence has been observed, much more intense for TOxP2+ than for H4P2+ and H2P. In the TOxP2+ case, the S2-->S0 fluorescence spectrum is remarkably sharp and shows an excellent mirror symmetry with respect to S0-->S2 absorption. On the contrary, the spectra of H4P2+ and H2P are shifted and more extended with respect to the absorption counterparts. The differences have been attributed primarily to the change of the equilibrium geometry upon excitation, larger in H2P and H4P2+ than in TOxP2+ and in the case of H4P2+ to the nonplanar conformation of the macrocycle. Also the S1-->S0 spectra of H2P, H4P2+, and TOxP2+ have been measured and more qualitatively discussed. The S1 and S2 fluorescence decays have been observed for H4P2+ and TOxP2+ exciting with ultrashort pulses. The S2 lifetime of TOxP2+ is of the order of the temporal resolution of our experimental apparatus, whereas that of H4P2+ is shorter. The S2-->S0 quantum yield of TOxP2+ has been estimated to be 0.035, approximately 3 orders of magnitude higher than that of H4P2+. It is proposed on the basis of ab initio model calculations that excited states of the H4P2+(CF3COO-)2 complex with charge-transfer character are responsible of the increased extension of the S2-->S0 spectrum with respect to that of H2P.     

Determination of viable <Emphasis Type="Italic">Escherichia coli</Emphasis> using antibody-coated paramagnetic beads with fluorescence detection

A rapid and convenient assay system was developed to detect viable Escherichia coli in water. The target bacteria were recovered from solution by immunomagnetic separation and incubated in tryptic soy broth with isopropyl-β-d-thiogalactopyranoside, which induces formation of β-galactosidase in viable bacteria. Lysozyme was used to lyse E. coli cells and release the β-galactosidase. β-Galactosidase converted 4-methylumbelliferyl-β-d-galactoside to 4-methylumbelliferone (4-MU), which was measured by fluorescence spectrophotometry using excitation and emission wavelengths of 355 and 460 nm, respectively. Calibration graphs of 4-MU fluorescence intensity versus E. coli concentration showed a detection range between 8 × 10⁴ and 1.6 × 10⁷ cfu mL⁻¹, with a total analysis time of less than 3 h. The advantage of this method is that it detects viable cells because it is based on the activity of the enzyme intrinsic to live E. coli.     

Multiple liquid chromatography separations and nanoESI-ion trap detection of plasma proteins in search of stroke biomarkers: A pilot study

Stroke is the most common cause of morbidity and death in the Western world, following ischemic heart disease and cancer. Stroke can be of two types, ischemic or hemorrhagic, with ischemic stroke accounting for approximately 85% of the total number of strokes. Well-recognized environmental risk factors for stroke include hypertension, smoking, diabetes mellitus, atrial fibrillation, and atherosclerosis. Computed tomography (CT) scanning is used to diagnose hemorrhagic stroke but is relatively ineffective and may remain normal in patients with mild ischemic strokes. Magnetic Resonance Imaging (MRI) is more sensitive in detecting ischemia than CT, especially in the diagnosis of mild stroke but it is still not 100% sensitive or precise. A simple and low-cost, rapid blood test to confirm a clinical and imaging diagnosis of ischemic stroke would be extremely useful. Based on this, the central idea of this paper is to develop a method that would be applicable to a statistically viable sample set to provide candidate biomarkers for distinguishing stroke types. In search of these candidate biomarkers, different analytical separation techniques have been used to screen for major differences in the proteomes of patients plasma samples with proteomics for identification.     

Deaminative meta-C–H alkylation by ruthenium(ii) catalysis

Precise structural modifications of amino acids are of importance to tune biological properties or modify therapeutical capabilities relevant to drug discovery. Herein, we report a ruthenium-catalyzed meta-C–H deaminative alkylation with easily accessible amino acid-derived Katritzky pyridinium salts. Likewise, remote C–H benzylations were accomplished with high levels of chemoselectivity and remarkable functional group tolerance. The meta-C–H activation approach combined with our deaminative strategy represents a rare example of selectively converting C(sp³)–N bonds into C(sp³)–C(sp²) bonds.

Precise structural modifications of amino acids are of importance to tune biological properties or modify therapeutical capabilities relevant to drug discovery.     

Volatile compounds in virgin olive oil: occurrence and their relationship with the quality

The stimulation of the human sensory receptors by volatile compounds present in virgin olive oils gives rise to the sensory attributes that describe its delicate and fragrant aroma. The composition of the volatile compounds and their biogenesis is briefly illustrated. Analytical methodologies for evaluating the volatile fraction and the sensory properties of virgin olive oils are elucidated. Compounds responsible for typical flavours are examined and the influence of the main factors on the composition of volatile compounds is discussed. The origin of off-flavours are also described and the consequent changes of volatile composition and of sensory characteristics are analysed. The relationships between volatile compounds and sensory attributes are discussed.     

Chirality and fragrance chemistry: stereoisomers of the commercial chiral odorants Muguesia and Pamplefleur

[structure: see text] The work describes the enzyme-mediated preparation and the odor evaluation of the single stereoisomers of the commercial odorants Muguesia and Pamplefleur. The synthetic approach to Muguesia stereoisomers helped to clear the assignment of the relative configuration of intermediate diols 5. The odor response of Pamplefleur isomers was found to be rather unusual. No stereoisomer prevailed, but each one played a definite role in establishing the odor sensation of the final blend.     

Peptide and protein separations by capillary electrophoresis in the presence of mono- and diquaternarized diamines

Two compounds, derivatives of 1,4-diazobicyclo[2,2,2]octane (DABCO), have been evaluated as potential quenchers of silanol interactions with peptides and proteins during their capillary zone electrophoresis (CZE) separations. They are: 1-(4-iodobutyl)4-aza-1-azoniabicyclo[2,2,2]octane iodide (M7C4I) and 1,4-didecyl-1,4-diazoniabicyclo [2,2,2]octane dibromide (C10M7C10). The first compound is known to react with the wall, by forming a covalent bond via alkylation of silanols. On the contrary, the second one (C10M7C10) can only loosely interact with silica due to lack of reactive iodine and to a much too short distance (a C(2)) between the two quaternary nitrogens. Very good peptide maps of protein digests can be obtained in isoelectric glutamic acid (Glu) buffer, at pH 3.52 by utilizing the M7C4I. However, in the case of total tissue extracts, excellent resolution is obtained only with the first eluting part of the analyte spectrum (i.e., peptides and smaller proteins). With larger proteins, interaction with the wall and loss of resolution is experienced. When using the C10M7C10, good resolution of di- and tripeptides is obtained, while a loss of resolution is observed with entire protein digest. M7C4I does not seem to interact with the peptide/protein analytes, and simply repels them from the wall via its positive charges; it is believed that disalt (C10M7C10) acts by interacting with the same compounds, possibly by forming micelles in solution.