Counteranion dependent protonation and aggregation of tetrakis(4-sulfonatophenyl)porphyrin in organic solvents

The tetrabutylammonium salt of 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin (TPPS) is soluble in dichloromethane, and the general properties of this compound have been investigated as function of various added acids HX (X = Cl, Br, I, CF(3)COO, CF(3)SO(3), TFPB) through UV-vis absorption spectroscopy, steady state fluorescence emission, and resonance light-scattering (RLS) techniques. Upon addition of HX, the initial monomeric free base TPPS is readily converted in an aggregated species, whose spectroscopic features are independent of the nature of the counteranion X. All the spectroscopic evidence suggest a J-type arrangement of chromophores in this aggregate, involving strong hydrogen bonds, electrostatic, and dispersive interactions. In the specific case of chloride and bromide, in the presence of a TBAX excess, the addition of the corresponding acid leads to a monomeric ion-pair between the TBA cations and the diacid TPPS, whose central core is strongly interacting with the halide. On further increasing the acid concentration in these latter solutions, fully protonated species are formed that eventually start to aggregate.     

Exotic properties and potential applications of quantum metamaterials

We discuss here potential venues for applications and exotic features of quantum metamaterials. We explore the coupling of conventional electromagnetic metamaterials with quantum emitters and the wave properties of quantum metamaterials obtained by tailoring their effective band structure. We discuss anomalous enhancement effects in the quantum emission properties of individual and collections of small emitters in the presence of metamaterials, as well as matter-wave cloaking and anomalous tunneling phenomena for quantum mechanical waves in artificial materials with exotic band structures.     

Self-similar p-adic fractal strings and their complex dimensions

We develop a geometric theory of self-similar p-adic fractal strings and their complex dimensions. We obtain a closed-form formula for the geometric zeta functions and show that these zeta functions are rational functions in an appropriate variable. We also prove that every self-similar p-adic fractal string is lattice. Finally, we define the notion of a nonarchimedean self-similar set and discuss its relationship with that of a self-similar p-adic fractal string. We illustrate the general theory by two simple examples, the nonarchimedean Cantor and Fibonacci strings. The text was submitted by the authors in English.     

Correlation between hydrogen/deuterium exchange and Amide I band intensity in hemoglobin aqueous solution under static or 50 Hz magnetic field

Samples of hemoglobin in deuterium oxide solution (D₂O) and in bidistilled H₂O water solution, both at the concentration of 100 mg/ml, were exposed to a static magnetic field at 100 mT; analogous samples were exposed to 50 Hz magnetic field at 1 mT. Fourier Transform Infrared (FTIR) Spectroscopy was used to analyze separately the response of the secondary structure of this protein (diluted in both aqueous solutions) to separated exposure to both magnetic fields. The most relevant result which was observed after exposures was the significant increasing in intensity of the Amide I band, which was already explained in previous studies assuming that proteins α-helix aligned along the direction of the applied magnetic field due to its large dipole moment. In particular, in this study it was shown that hydrogen/deuterium exchange induced a reduction of the increasing of Amide I vibration band. This result can be explained assuming that Amide hydrogens of hemoglobin exchange with solvent deuterium atoms, causing an increase in mass of the protein and a correlated increasing in inertia of the α-helix, reducing significantly the torque effect of the applied magnetic field.     

Local coordination and dynamics in liquid antimony trichloride/water mixture

Summary EXAFS Rayleigh wing and Raman-scattering data in SbCl₃/H₂O mixture are presented. The measurements, carried out at the PULS facility on the ClK-edge and on theL _{I, II, III}-edges as a function of temperature, allow us to define the local order around the absorber. In particular, clear evidence exists that intramolecular Sb−Cl and intermolecular Sb...Cl distances and coordination, similar to the ones existing in pure SbCl₃, are present. The data analysis reveals also that the water molecules are linked to the chlorine, giving rise to a cross-link between the antimony trichloride chains. The light scattering response confirms these structural hypotheses, indicating that the primitiveC _3v symmetry of the SbCl₃ molecule is lowered by the water presence. Evidence also exists that new vibrational bands are originated by the chlorine-water bonds. Finally we detected a phononlike contribution, in the low-frequency region, that gives an effective Raman vibrational density of states.

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Riassunto Nel presente lavoro si presentano e si discutono i risultati di misure EXAFS, di Rayleigh wing e di scattering Raman nella miscela SbCl₃/H₂O. Le misure EXAFS, eseguite presso i laboratori PULS di Frascati, sia sullo spigoloK del cloro che sugli spigoliL _{I, II, III} dell’antimonio, permettono di ottenere informazioni sull’ordine locale del sistema. In particolare si evidenziano formazioni di legami intramolecolari Sb−Cl ed intermolecolari Sb...Cl che sono simili nelle distanze e nella coordinazione a quelli esistenti nel fuso. Si definisce anche il ruolo dell’acqua che, coordinandosi con i clori, agisce da ponte tra catene di tricloruro di antimonio. Le misure di scattering di luce confermano le ipotesi strutturali emerse dai risultati di spettroscopia EXAFS: la simmetria originaleC _3v della molecola SbCl₃ si abbassa nell’interazione con l’acqua. Inoltre nuove bande vibrazionali appaiono negli spettri Raman, legati all’interazione cloro-acqua. Infine nella regione spettrale a bassa frequenza si evidenziano modi cooperativi connessi con la presenza di una densità di stati vibrazionali.

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Резюме В работе приводятся данные для рзлеевского крыла EXAFS и комбинационного рассеяния в смеси SbCl₃/H₂O. Измерения наK-кра Cl иL _{I, II, III}-краях, как функция температуры, позволяют нам определить локальный порядок около поглотителя. В частности, отмечается, что внутримолекулярные Sb−Cl и межмолекулярные Sb...Cl расстояния и координация оказываются сходными с величинами, существующими в чистом SbCl₃. Анализ данных также показывает, что молекулы воды связаны с хлором, что приводит к кросс-связи межлу цепочками SbCl₃. Рассеяние света подтверждает эти структурые гипотезы, указывая на то, что примитивнаяC _3v симметрия молекулы SbCl₃ уменьшается из-за присутствия воды. Также подтверждается, что образуются новые колебательные зоны благодаря связям хлора с водой. В заключение, мы детектируем фононно-подобный вклад в низкочастотной области, который дает эффективную плотность рамановских колебательных состояний.

     

Metal-mediated self-assembly of tetrapyridyl porphyrins by Na+ ions

In the presence of the sodium salt of a bulky anion, which allows the solubility of Na(+) in low polarity solvents, various tetra(4-pyridyl)porphyrin derivatives can spontaneously self-assemble from CH(2)Cl(2) into supramolecular nanostructures exhibiting a long-range order, through the coordination of Na(+) ions by the pyridyl moieties at the macrocycle periphery.     

Radiation-induced polymerization for the immobilization of penicillin acylase

The immobilization ofEscherichia coli penicillin acylase (EC 3.5.1.11) was investigated by radiation-induced polymerization of 2-hydroxyethyl methacrylate at low temperature. A leak-proof composite that does not swell in water was obtained by adding the crosslinking agent trimethylolpropane trimethacrylate to the monomer-aqueous enzyme mixture. Penicillin acylase, which was immobilized with greater than 70% yield, possessed a higherK _m value toward the substrate 6-nitro-3-phenylacetamidobenzoic acid than the free enzyme form (K _m = 1.7 × 10⁻⁵ and 1 × 10⁻⁵M, respectively). The structural stability of immobilized penicillin acylase, as assessed by heat, guanidinium chloride, and pH denaturation profiles, was very similar to that of the free-enzyme form, thus suggesting that penicillin acylase was entrapped in its native state into aqueous free spaces of the polymer matrix.