Direct analysis of isopropylthioxanthone (ITX) in milk by high-performance liquid chromatography/tandem mass spectrometry

A fast screening method is presented for detecting isopropylthioxanthone (ITX) contamination in milk. The method is based on direct high-performance liquid chromatography/tandem mass spectrometry (HPLC/MS/MS) analysis of milk samples. Sample preparation is limited to the addition of a deuterated ITX solution in acetonitrile that serves both as internal standard and to precipitate proteins. The method is highly accurate and sensitive. Isomeric specific analyses of 2-ITX and 4-ITX are possible at 6 microg/L levels with about 5% precision and accuracy. This approach has been used to check contamination in samples like milk, soy milk, baby milk, in their packaging material. Out of 37 milk samples analyzed, 16 were positive with concentrations ranging from 173-439 microg/L for 2-ITX and from <6 (lower than limit of quantification) to 25 microg/L for 4-ITX.     

A new dinuclear heme-copper complex derived from functionalized protoporphyrin IX

A new biomimetic model for the heterodinuclear heme/copper center of respiratory oxidases is described. It is derived from iron(III) protoporphyrin IX by covalent attachment of a Gly-L-His-OMe residue to one propionic acid substituent and an amino-bis(benzimidazole) residue to the other propionic acid substituent of the porphyrin ring, yielding the Fe(III) complex 1, and subsequent addition of a copper(II) or copper(I) ion, according to needs. The fully oxidized Fe(III)/Cu(II) complex, 2, binds azide more strongly than 1, and likely contains azide bound as a bridging ligand between Fe(III) and Cu(II). The two metal centers also cooperate in the reaction with hydrogen peroxide, as the peroxide adducts obtained at low temperature for 1 and 2 display different optical features. Support to this interpretation comes from the investigation of the peroxidase activity of the complexes, where the activation of hydrogen peroxide has been studied through the phenol coupling reaction of p-cresol. Here the presence of Cu(II) improves the catalytic performance of complex 2 with respect to 1 at acidic pH, where the positive charge of the Cu(II) ion is useful to promote O-O bond cleavage of the iron-bound hydroperoxide, but it depresses the activity at basic pH because it can stabilize an intramolecular hydroxo bridge between Fe(III) and Cu(II). The reactivity to dioxygen of the reduced complexes has been studied at low temperature starting from the carbonyl adducts of the Fe(II) complex, 3, and Fe(II)/Cu(I) complex, 4. Also in this case the adducts derived from the Fe(II) and Fe(II)/Cu(I) complexes, that we formulate as Fe(III)-superoxo and Fe(III)/Cu(II)-peroxo exhibit slightly different spectral properties, showing that the copper center participates in a weak interaction with the dioxygen moiety.     

Zinc phthalocyanines-mediated photodynamic therapy induces cell death in adenocarcinoma cells

A panel of eight Zn-phthalocyanines (Zn-Pcs) (1)-(8), differently substituted on the benzo units, was synthesized either by direct cyclic-tetramerization of substituted phthalonitriles (compounds 1 and 2), or leading from the easily available tetrasulphonyl phthalocyanine to yield the sulfonamido derivatives 3 and 4, or else via the chloromethylation of precedent Zn-Pc followed by reaction with nucleophiles affording the dicationic Zn-Pcs (5) and (6) or the neutral Zn-Pcs (7) and (8). The phototoxicity of these new compounds was evaluated in vitro on human colon adenocarcinoma cell line (HCT116), and their effect compared with those induced by porfimer sodium. The results are reported as IC₅₀ values, following exposure of the cells to different Zn-Pcs concentration and irradiation with a 500 W tungsten/halogen white lamp. The cationic Zn-Pc (5) and (6) together with the Zn-Pc (7), featuring 12 methoxy groups, were found good or fairly good photosensitizers while the more lipophilic Zn-Pcs (1)-(4) and (8) were found devoid of activity.     

Microwave-assisted synthesis of 2-aminothiophene-3-carboxylic acid derivatives, 3H-thieno[2,3-d]pyrimidin-4-one and 4-chlorothieno[2,3-d]pyrimidine

A two-minute microwave irradiation allowed the synthesis of several 2-aminothiophene-3-carboxylic acid derivatives. Their efficient transformation to thieno[2,3-d]pyrimidin-4-one and the corresponding 4-chloro derivative is also reported under microwave irradiation.     

Molecular Recognition of Amino Acids by Copper(II) Complexes of 6(A),6(X)-Diamino-6(A),6(X)-dideoxy-beta-cyclodextrin (X = B, C, D)

The three regioisomers of beta-cyclodextrin 6-difunctionalized with NH(2) groups (6(A),6(X)-diamino-6(A),6(X)-dideoxy-beta-cyclodextrin, A,X-CDNH(2), X = B, C, or D) were synthesized. Their binary and ternary copper(II) complexes with amino acids were characterized by ESR and electronic spectroscopy. Furthermore, the binary copper(II) complexes were used as eluent in ligand exchange chromatography (LEC), to resolve racemates of unmodified amino acids. HPLC separation of enantiomers of aromatic amino acids was obtained only when the complex [Cu(A,B-CDNH(2))](2+) was used as eluent. The two complexes with the other two regioisomers did not show chiral recognition ability. Circular dichroism (c.d.) spectroscopy studies of the ternary complexes with D- and L-amino acids carried out in the presence and in the absence of 1-adamantanol, suggested a recognition mechanism that involves the cyclodextrin cavity, only in the case of ternary A,B-CDNH(2) complexes.     

Interpretation of Quantum Nonlocality by Conformal Quantum Geometrodynamics

The principles and methods of the Conformal Quantum Geometrodynamics (CQG) based on the Weyl’s differential geometry are presented. The theory applied to the case of the relativistic single quantum spin \(\frac{1}{2}\) leads a novel and unconventional derivation of Dirac’s equation. The further extension of the theory to the case of two spins \(\frac{1}{2}\) in EPR entangled state and to the related violation of Bell’s inequalities leads, by a non relativistic analysis, to an insightful resolution of the enigma implied by quantum nonlocality.     

Real-time manipulation of gold nanoparticles inside a scanning electron microscope

The forces needed to overcome static friction and move 150 nm diameter Au nanoparticles on an oxidized Si substrate were measured in Normal and Shear oscillation modes inside a scanning electron microscope (SEM) in real time. The experimental setup consisted of a quartz tuning fork (QTF) mounted onto a high-precision 3D nanomanipulator used with a glued silicon or tungsten tip as a force sensor. Static friction was found to range from tens of nN to several hundred nN. Large variations in static friction values were related to differences in particle shape. Kinetic friction tended to be close to the detection limit and in most cases did not exceed several nN. The influence of thermal treatment in reducing the static friction of nanoparticles was considered.     

Y(P,V)O4:Dy phosphors for white light generation: Emission dynamics and host effect

The structural characteristics and optical spectra of Y(P,V)O₄:Dy³⁺phosphors obtained by solid state reaction, sol-gel and hydrothermal routes have been investigated and compared. The luminescence features of these materials show a complicate dependence on the composition, synthetic method and excitation conditions. The emission performance depends on different effects: host luminescence, energy transfer to the doping ions and host dependence of the Dy³⁺ emission properties. These effects have been rationalized in order to provide useful information for the development of a suitable material for the white light emitting phosphors technology.     

Energy and density analysis on the H2 molecule from the united atom to dissociation: The Σ, Π, Δ, ϕ, and Γ manifolds

We present 140 accurate potential energy curves, PECs, for the Σ, Π, Δ, ?, and Γ manifolds for the H₂ molecule, mapping all the states with energy below the H ground state. The full configuration interaction, nonrelativistic Born–Oppenheimer computations are performed with large and optimized basis sets of Slater‐type and spherical Gaussian functions; these new basis sets are somewhat larger than those used in recent published studies on the 60 Σ state PECs. The full CI computations are performed twice, with Hartree–Fock and with Heitler–London‐type functions, allowing the identification of the ionic component in the total energy. The computed energies are within 10^?5 hartree from the most accurate PECs in literature. We aim (a) at the evaluation of the PECs starting at very short and unexplored internuclear distances (0.01 bohrs) and ending at full dissociation, (b) at the systematic prediction of high excited state PECs dissociating as 1s + 4l and 1s + 5l, and (c) at the characterization of the evolution of the 140 PEC electronic densities from united atom to dissociation. With this work we fill a gap in today literature, which has dealt mainly with low excited states, generally excluding short internuclear distances. The electronic configuration at the united atom persists as dominant configuration well beyond the equilibrium separation, and it switches to that at dissociation often with energy patterns seemingly irregular, in particular when the values of the principal quantum number at dissociation and at the united atom differ by one or more unit. The Hund's singlet‐triplet splitting, which propagates from the united atom to the molecule, is discussed. The singlet and triplet states are rather close in energy in the Π manifolds, and approach degeneracy in the Δ and ? manifolds, to become fully degenerate in the Γ manifolds. Discussions on the correlation energy correction, adiabatic correction, spectroscopic constants and on general features of the H₂ excited states are presented. The H₂ molecule is a system, which—to be understood—needs consideration of both the very short internuclear distances in approaching the united atom and of the very high excited states below H. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011     

Zinc(II) complexes of ubiquitin: speciation, affinity and binding features

Intraneuronal inclusions consisting of hypermetallated, (poly-)ubiquitinated proteins are a hallmark of neurodegeneration. To highlight the possible role played by metal ions in the dysfunction of the ubiquitin-proteasome system, here we report on zinc(II)/ubiquitin binding in terms of affinity constants, speciation, preferential binding sites and effects on protein stability and self-assembly. Potentiometric titrations allowed us to establish that at neutral pH only two species, ZnUb and Zn(2)Ub, are present in solution, in line with ESI-MS data. A change in the diffusion coefficient of ubiquitin was observed by NMR DOSY experiments after addition of Zn(II) ions, and thus indicates metal-promoted formation of protein assemblies. Analysis of (1)H, (15)N, (13)Cα and (13)CO chemical-shift perturbation after equimolar addition of Zn(II) ions to ubiquitin outlined two different metal-binding modes. The first involves a dynamic equilibrium in which zinc(II) is shared between a region including Met1, Gln2, Ile3, Phe4, Thr12, Leu15, Glu16, Val17, Glu18, Ile61 and Gln62 residues, which represent a site already described for copper binding, and a domain comprising Ile23, Glu24, Lys27, Ala28, Gln49, Glu51, Asp52, Arg54 and Thr55 residues. A second looser binding mode is centred on His68. Differential scanning calorimetry evidenced that addition of increasing amounts of Zn(II) ions does not affect protein thermal stability; rather it influences the shape of thermograms because of the increased propensity of ubiquitin to self-associate. The results presented here indicate that Zn(II) ions may interact with specific regions of ubiquitin and promote protein-protein contacts.