Incompatible and Contradictory Retrodictions in the History Approach to Quantum Mechanics

We illustrate two simple spin examples which show that in the consistent histories approach to quantum mechanics one can retrodict with certainty incompatible or contradictory propositions corresponding to non-orthogonal or, respectively, orthogonal projections.     

Generalized limit analysis in poroplasticity by mathematical programming

Classical limit analysis of structures by the statical approach computationally means maximization of a load multiplier under equilibrium and yield condition constraints, namely convex mathematical programming. In elastoplasticity, generalizations of limit analysis had been proposed in order to achieve, still by load factor constrained optimization, the safety factor with respect to plastic collapse. This paper presents similar generalization in two-phase poroelastoplasticity. A method is here developed (and validated by numerical application to a masonry dam) apt to assess the safety factor of a structure interpretable as a poroplastic system, with respect to both plastic collapse and critical thresholds on deformations, by solving a nonconvex nonsmooth constrained optimization problem usually referred to in the literature as “mathematical program under equilibrium constraints”. Piece-wise linearization of yield surfaces and reduction of yield planes by a “sifting” procedure are adopted to reduce computing efforts.     

A computational workflow for the design of irreversible inhibitors of protein kinases

Design of irreversible inhibitors is an emerging and relatively less explored strategy for the design of protein kinase inhibitors. In this paper, we present a computational workflow that was specifically conceived to assist such design. The workflow takes the form of a multi-step procedure that includes: the creation of a database of already known reversible inhibitors of protein kinases, the selection of the most promising scaffolds that bind one or more desired kinase templates, the modification of the scaffolds by introduction of chemically reactive groups (suitable cysteine traps) and the final evaluation of the reversible and irreversible protein–ligand complexes with molecular dynamics simulations and binding free energy predictions. Most of these steps were automated. In order to prove that this is viable, the workflow was tested on a database of known inhibitors of ERK2, a protein kinase possessing a cysteine in the ATP site. The modeled ERK2-ligand complexes and the values of the estimated binding free energies of the putative ligands provide useful indicators of their aptitude to bind reversibly and irreversibly to the protein kinase. Moreover, the computational data are used to rank the ligands according to their computed binding free energies and their ability to bind specific protein residues in the reversible and irreversible complexes, thereby providing a useful decision-making tool for each step of the design. In this work we present the overall procedure and the first proof of concept results.     

PHOTOSENSITIZATION OF AMINO ACIDS BY DI-CYAN-HEMIN: KINETIC AND EPR STUDIES

Abstract— The low spin hemin derivative di-cyan-hemin can sensitize the photooxidation of amino acids. The efficiency of this dye as a photosensitizer is generally lower than that of other porphyrins such as hematoporphyrin in aqueous solution, but it is significantly enhanced by addition of ethanol. On the basis of the identified photooxidation end-products of some amino acids, photooxidation kinetic data and EPR measurements, it appears that methionine is quantitatively converted to methionine sulfoxide by a pure Type II (singlet oxygen) mechanism, whereas in the case of cysteine and tryptophan a mixed Type ILType II mechanism is probably operative.     

Photohemolysis of erythrocytes enriched with superoxide dismutase, catalase and glutathione peroxidase

Abstract— Cationic liposomes have been used to introduce into human erythrocytes variable amounts of the enzymes superoxide dismutase, catalase and glutathione peroxidase. The behaviour of the enzyme-enriched erythrocytes toward photohemolysis sensitized by protoporphyrin IX has been studied in comparison to that of erythrocytes treated with empty liposomes. The erythrocytes with increased catalase and glutathione peroxidase activity were more resistant to photohemolysis. In contrast, the erythrocytes enriched with superoxide dismutase hemolyzed faster. The association of two enzymes at a time was also studied     

Ion trap mass spectrometry in the structural analysis of haemoglobin peptides modified by epichlorohydrin and diepoxybutane

Ion trap mass spectrometry has been shown to be particularly suitable for the structural analysis of high molecular weight peptides directly fragmented in the mass analyser without needing further sub-digestion reactions. Here we report the advantages of using multi-stage ion trap mass spectrometry in the structural characterisation of haemoglobin alkylated with epichlorohydrin and diepoxybutane. Alkylated globins were digested with trypsin and the peptide mixtures were analysed by MS(3). This technique allows the sequential fragmentation of peptides under analysis, giving rise to MS(3) product ion spectra with additional information with respect to MS(2) mass spectra. The results obtained complete the previously reported structural characterisation of alkylated haemoglobin, demonstrating the potential of ion trap mass spectrometry.     

Segregation and phase transition in mixed lipid films

Energy dispersion X-ray diffraction (EDXD) was applied to investigate the structure of partly dehydrated mixed films formed by the phospholipid dimyristoyl phosphatidylcoline (DMPC) and any of the three diastereomers of the dicationic gemini surfactant (2S,3S)-2,3-dimethoxy-1,4-bis(N-hexadecyl-N,N-dimethylammonium) butane dibromide. As the surfactant to lipid molar ratio (R(S/L)) increases, the gemini monotonically solubilizes the lipid bilayer promoting the formation of a cubic phase of space group Pmn segregating from the residual lamellar phase of the lipid. Finally, at R(S/)(L) = 1, the phase transition is complete. The mixed film at the highest surfactant to lipid molar ratio (R(S/L) = 2.3) was hydrated by a vapor saturated atmosphere. At full hydration, a cubic to lamellar phase transition occurs. Coarse grain dynamic investigations, carried out as a function of both the surfactant to lipid molar ratio and the number of water molecules for amphiphile unit, allowed us to elucidate the structure of the emerging cubic phase and the hydration-induced structural pathway of the cubic to lamellar phase transition observed by EDXD.