Blends of natural and synthetic polymers: A new route to novel biomaterials

Blends of natural and synthetic polymers were studied for potential applications in the biomedical field. Collagen and hyaluronic acid were mixed in aqueous solution with poly(vinyl alcohol) and poly(acrylic acid). The properties of the blends were studied by differential scanning calorimetry and dynamic mechanical thermal analysis. Some methods were also investigated to enhance the miscibility of the polymers in these blends.     

Binding models of reversible inhibitors to type-B monoamine oxidase

Interest in the inhibitors of type-B monoamine oxidase has grown in recent years, due to the evidence for multiple roles of one such agent (selegiline) in the pharmacological management of neurodegenerative disorders. A set of 130 reversible and selective inhibitors of MAO-B (including tetrazole, oxadiazolone, and oxadiazinone derivatives) were taken from the literature and subjected to a three-dimensional quantitative structure–activity relationship (3D-QSAR) study, using CoMFA and GOLPE procedures. The steric and lipophilic fields, alone and in combination, provided us with informative models and satisfactory predictions (q²=0.73). The validity of these models was checked against the 3D X-ray structure of human MAO-B. Flexible docking calculations, performed by using a new approach which took advantage from QXP and GRID computational tools, showed the diverse inhibitors to interact with MAO-B in a similar binding mode, irrespective of the heterocycle characterizing them. A significant trend of correlation was observed between estimated energies of the complexes and the experimental inhibition data.     

Microscopic model for thin film spreading

A microscopic, driven lattice gas model is proposed for the dynamics and spatiotemporal fluctuations of the precursor film observed in spreading experiments. Matter is transported both by holes and particles, and the distribution of each can be described by driven diffusion with a moving boundary. This picture leads to a stochastic partial differential equation for the shape of the boundary. Explicit analytic results are obtained which agree with the simulations of the lattice gas.     

Direct determination of kallikrein by high-performance liquid chromatography.

A direct and specific identification of porcine pancreatic kallikrein by high-performance hydrophobic chromatography is proposed; the minimum amount which can be injected is 2.5 U. An application to the quantitative determination of the enzyme by high-performance size-exclusion chromatography is reported; the method is precise with a mean coefficient of variation of 2.8% and the minimum amount which can be injected is 0.02 U of kallikrein. The results obtained with determinations in real biological samples (porcine pancreatic powder and human urine) are reported. The method is based on direct and specific chromatographic signals and does not destroy the biological activity of this enzyme.     

Non-phase-matched enhancement of second-harmonic generation in multilayer nonlinear structures with internal reflections

Traditional notions of second-harmonic generation rely on phase matching or quasi phase matching to achieve good conversion efficiencies. We present an entirely new concept for efficient second-harmonic generation that is based on the interference of counterpropagating waves in multilayer structures. Conversion efficiencies are an order of magnitude larger than with phase-matched second-harmonic generation in similar multilayer structures.     

Archaeo-metallurgical studies of tuyeres and smelting slags found at Tharros (north-western Sardinia, Italy)

A large number of pyrometallurgical materials such as tuyeres, slags and refractory tools likely associated with metal extraction processes have been found at Tharros (north-western Sardinia, Italy) during archaeological excavations stratigraphically related to the Phoenician–Punic period (VI–III centuries BC). Micro-chemical, micro-structural and mineralogical studies have been carried out by means of the combined use of X-ray diffraction (XRD), selected-area X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) combined with energy-dispersive X-ray analysis (EDS) in order to identify pyrometallurgical processes and main relevant technological parameters. The results reveal that tuyeres, slags and refractory tools can be associated with an iron ore smelting process to extract the metal by slagging the unwanted by-products. Moreover, temperature and duration of the smelting process have been estimated through mineralogical studies and by a comparative analysis between the micro-chemical and structural features of thermally treated refractory materials and tuyeres. The results disclose the high level of technological competence of the ancient metallurgists able to carry out complex high-temperature processes to extract iron from ores by separating the metal from unwanted siliceous species.     

Crucigasterins A-E, antimicrobial amino alcohols from the Mediterranean colonial ascidian Pseudodistoma crucigaster

Five new unsaturated 2-amino-3-alcohols, crucigasterins A-E (2-6), were isolated together with known related compound 7 from the Mediterranean ascidian Pseudodistoma crucigaster and characterised as diacetyl derivatives (2a-6a) by spectroscopic methods. The threo-relative configuration of the amino alcohol portion was inferred by NOE analysis of the oxazolidinone derivative of crucigasterin A (2) as well as by ¹³C NMR comparison with synthetic threo and erythro model compounds. The co-occurring metabolites were assumed to have the same relative configuration as 2 by comparison of the diagnostic carbon value of C-1. The absolute stereochemistry of compound 7 that had not been previously reported was determined by applying the modified Mosher’s method on the corresponding N-acetyl derivative. The same absolute configuration was suggested for the other co-occurring crucigasterins by biogenetic considerations. Antibacterial and antifungal activities of selected crucigasterins were also evaluated.