Effect of Some Macrocyclic Ligands on the Rate of Reduction of Perchlorate Ion by Titanium(III)

Complexation with cyclam increases the rate of reduction of perchlorate ion by TiIII (in acidic, aqueous, 4 mol dm-3 LiCl Solutions at 25 °C) relative to the rate of the corresponding reduction of Ti3+. A modified cyclam with pendant amine and p-aminobenzyl functional groups is more effective in this regard than is cyclam itself. Both redox reactions are acid catalyzed. The data is consistent with involvement of an intermediate containing two TiIII centers

Chemical Sensor for Haemodialysis Application

Abstract The water used to supply a haemodialysis center requires particular mode of treatment in order to achieve the best technical, economic and therapeutic distribution. Dialysis patients come in contact weekly with a large amount of water through the dialysis apparatus. It is therefore essential that this solution has a high quality and purity in terms of proper electrolyte composition, low concentration or absence of organic and inorganic chemical pollutants, low concentration or absence of bacteria, yeasts, fungi and endotoxins. The chemical and microbiological quality of water intended for medical and biomedical treatments, such as haemodialysis, is generally defined on the basis of a plurality of international reference standards (ASTM International standards D1193 and D5196; International Pharmacopoeia and European Pharmacopoeia CAP / NCCLS 1988). In this work the authors have designed an electrochemical device used to characterize pure and ultrapure water for biomedical applications (Patent: TO2014A000765). The results obtained show a good ability of the device in the discrimination of different bacteria and of their concentration (CFU); Pseudomonas and E-coli have been here tested

Theoretical modeling of UV-Vis absorption and emission spectra in liquid state systems including vibrational and conformational effects: the vertical transition approximation

In this paper we describe in detail a general and efficient methodology, based on the perturbed matrix method and molecular dynamics simulations, to model UV-Vis absorption and emission spectra including vibrational and conformational effects. The basic approximation used is to consider all the chromophore atomic coordinates as semiclassical degrees of freedom, hence allowing the calculation of the complete spectral signal by using the electronic vertical transitions as obtained at each possible chromophore configuration, thus including the contributions of vibrations and conformational transitions into the spectrum. As shown for the model system utilized in this paper, solvated 1-phenyl-naphthalene, such an approximation can be rather accurate to reproduce the absorption and emission spectral line shape and properties when, as it often occurs, the vertical vibronic transition largely overlaps the other non-negligible vibronic transitions

Deconstructing the governing dissipative phenomena in the nanoscale

An expression describing the controlling parameters involved in short range nanoscale dissipation is proposed and supported by simulations and experimental findings. The expression is deconstructed into the geometrical, dynamic, chemical and mechanical properties of the system. In atomic force microscopy these are translated into 1) tip radius and tip-sample deformation, 2) resonant frequency and oscillation amplitude and 3) hysteretic and viscous dissipation. The latter are characteristic parameters defining the chemical and mechanical properties of the tip-sample system. Long range processes are also discussed and footprints are identified in experiments conducted on mica and silicon samples. The present methodology can be exploited to validate or invalidate nanoscale dissipative models by comparing predictions with experimental observables

Salification Controls the In-Vitro Release of Theophylline

Sustained released formulation is the most used strategy to control the efficacy and the adverse reactions of an API (active pharmaceutical ingredient) with a narrow therapeutic index. In this work, we used a different way to tailor the solubility and diffusion of a drug. Salification of Theophylline with Squaric Acid was carried out to better control the absorption of Theophylline after administration. Salification proved to be a winning strategy decreasing the dissolution of the APIs up to 54% with respect to Theophylline. Most importantly, this was accomplished in the first 10 min of the dissolution process, which are the most important for the API administration. Two polymorphs were identified and fully characterized. Theophylline squarate was discovered as trihydrate (SC-XRD) and as a metastable anhydrous form. Indeed, during the Variable Temperature-XRPD experiment, the trihydrate form turned back into the two starting components after losing the three molecules of water. On the other hand, the synthesis of the trihydrate form was observed when a simple mixing of the two starting components were exposed to a high humidity relative percentage (90% RH)

Renormalization group approach to vibrational energy transfer in protein

Renormalization group method is applied to the study of vibrational energy transfer in protein molecule. An effective Lagrangian and associated equations of motion to describe the resonant energy transfer are analyzed in terms of the first-order perturbative renormalization group theory that has been developed as a unified tool for global asymptotic analysis. After the elimination of singular terms associated with the Fermi resonance, amplitude equations to describe the slow dynamics of vibrational energy transfer are derived, which recover the result obtained by a technique developed in nonlinear optics [S.J. Lade, Y.S. Kivshar, Phys. Lett. A 372 (2008) 1077].Comment: 11 page

Influence of conformational fluctuations on enzymatic activity: modelling the functional motion of beta-secretase

Considerable insight into the functional activity of proteins and enzymes can be obtained by studying the low-energy conformational distortions that the biopolymer can sustain. We carry out the characterization of these large scale structural changes for a protein of considerable pharmaceutical interest, the human $\beta$-secretase. Starting from the crystallographic structure of the protein, we use the recently introduced beta-Gaussian model to identify, with negligible computational expenditure, the most significant distortion occurring in thermal equilibrium and the associated time scales. The application of this strategy allows to gain considerable insight into the putative functional movements and, furthermore, helps to identify a handful of key regions in the protein which have an important mechanical influence on the enzymatic activity despite being spatially distant from the active site. The results obtained within the Gaussian model are validated through an extensive comparison against an all-atom Molecular Dynamics simulation.Comment: To be published in a special issue of J. Phys.: Cond. Mat. (Bedlewo Workshop

Calculation of the optical rotatory dispersion of solvated alanine by means of the perturbed matrix method

Abstract The zwitterionic form of aqueous L L-alanine is chosen as a benchmark for the theoretical evaluation of the optical rotatory dispersion (ORD) in solution, as provided by a simple application of the perturbed matrix method (PMM). Results show the applicability of this procedure, suggesting that its use might provide a general theoretical-computational tool for describing, at atomic-molecular level, the optical activity of a molecule in a complex environment

Statistical mechanics and thermodynamics of magnetic and dielectric systems based on magnetization and polarization fluctuations:Application of the quasi-Gaussian entropy theory

The quasi-Gaussian entropy (QGE) theory employs the fact that a free-energy change can be written as the moment-generating function of the appropriate probability distribution function of macroscopic fluctuations of an extensive property. In this article we derive the relation between the free energy of a system in an external magnetic or electric field and the distribution of the “instantaneous” magnetization or polarization at zero field. The physical-mathematical conditions of these distributions are discussed, and for several continuous and discrete model distributions the corresponding thermodynamics, or “statistical state,” is derived. Some of these statistical states correspond to well-known descriptions, such as the Langevin and Brillouin models. All statistical states have been tested on several magnetic and dielectric systems: antiferromagneti