Determination of the stability of coal-oil mixtures (COM) by infrared analysis

The stability of coal-oil mixtures (COM) may be assessed by using infrared (i.r.) spectroscopy. An i.r. spectrum of a COM has analytical bands at 540 cm^?1 for coal and at 810 cm^?1 for oil; these bands are used to determine the change in concentration of coal in a COM with time. The i.r. spectra provides information on the possible interactions between the two materials and an indication of the physico-chemical properties of such mixtures.     

A model of the endogenous glucose balance incorporating the characteristics of glucose transporters

This paper describes the development and preliminary test of a model of the endogenous glucose balance that incorporates the characteristics of the glucose transporters GLUT1, GLUT3 and GLUT4. In the modeling process the model is parameterized with nine parameters that are subsequently estimated from data in the literature on the hepatic- and endogenous- balances at various combinations of blood glucose and insulin levels. The ability of the resulting endogenous balance to fit blood glucose measured from patients was tested on 20 patients. The fit obtained with this model compared favorably with the fit obtained with the endogenous balance currently incorporated in the DIAS system.     

Message Encryption by Phase Modulation of a Chaotic Optical Carrier

We present a numerical and experimental evaluation of message encryption by phase modulation, using a chaotic optical carrier generated by a laser subject to delayed optical feedback. This method offers better security than the conventional amplitude masking, where the signal is simply added to the chaotic waveform     

Design and Synthesis of Oligopeptidic Parvulin Inhibitors

Pin1 catalyzes the cis-trans isomerization of pThr-Pro or pSer-Pro amide bonds of various proteins involved in several physio/pathological processes. In this framework, recent research activity is directed toward the identification of new selective Pin1 inhibitors. Here, we developed a set of peptide-based Pin1 inhibitors. Direct-binding experiments allowed the identification of the peptide-based inhibitor 5 k (methylacetyl-l -alanyl-l -histidyl-l -prolyl-l -phenylalaninate) as a potent ligand of Pin1. Notably, 5 k binds Pin1 with higher affinity than Pin4. The comparative analysis of molecular models of Pin1 and Pin4 with the selected compound gave a rational explanation of the biochemical activity and pinpointed the chemical elements that, if opportunely modified, may further improve inhibitory potency, pharmacological properties, and selectivity of future peptide-based parvulin inhibitors. Since 5 k showed limited cell penetration and no antiproliferative activity, it was conjugated to a polyarginine stretch (R8), known to promote cell penetration of peptides, to obtain the R8–5 k derivative, which displayed antiproliferative effects on cancer cell lines over non-tumor cells. The effect of R8 on cell proliferation was also investigated. This work warrants caution about applying the R8 strategy in the development of cell-penetrating antiproliferative peptides, as it is not inert.     

Stable isotopes of Cu and Zn in higher plants: evidence for Cu reduction at the root surface and two conceptual models for isotopic fractionation processes

Recent reports suggest that significant fractionation of stable metal isotopes occurs during biogeochemical cycling and that the uptake into higher plants is an important process. To test isotopic fractionation of copper (Cu) and zinc (Zn) during plant uptake and constrain its controls, we grew lettuce, tomato, rice and durum wheat under controlled conditions in nutrient solutions with variable metal speciation and iron (Fe) supply. The results show that the fractionation patterns of these two micronutrients are decoupled during the transport from nutrient solution to root. In roots, we found an enrichment of the heavier isotopes for Zn, in agreement with previous studies, but an enrichment of isotopically light Cu, suggesting a reduction of Cu(II) possibly at the surfaces of the root cell plasma membranes. This observation holds for both graminaceous and nongraminaceaous species and confirms that reduction is a predominant and ubiquitous mechanism for the acquisition of Cu into plants similar to the mechanism for the acquisition of iron (Fe) by the strategy I plant species. We propose two preliminary models of isotope fractionation processes of Cu and Zn in plants with different uptake strategies.     

Donnan membrane approach: from equilibrium to dynamic speciation

Metal ion toxicity is not simply related to the total concentration but to the free or labile metal ion concentration. One of the techniques that can measure the free metal ion concentration is the Donnan Membrane Technique (DMT). However, this method has limitations in terms of a relatively high detection limit (in relation to typical environmental concentrations) and a long equilibration time. We have therefore developed the Flux Donnan Membrane (FDM) Technique, which is a dynamic modification of the standard DMT with improved detection limits and a more rapid response. We show that experimental calibrations of metal ion transport in the FDM can be used to measure [M]free under conditions of either solution-controlled or membrane-controlled diffusive transport. The FDM was used to measure cobalt binding isotherms by a humic substance over a large range of free Co concentrations and pH.     

Modeling the interactions between humics, ions, and mineral surfaces

Model VI and the NICA-Donnan model are two successful models presently available for describing metal ion binding by humic materials. Both models deal with the complexity of the underlying processes (intrinsic heterogeneity, partial correlation between affinity distributions, variable stoichiometry, electrostatics) in a pragmatic way. The parameters of the NICA-Donnan model and their determination are discussed. The current interpretation of the ion-specific "non-ideality" parameters, ni, found in the NICA-Donnan model, emphasizes their role in determining the stoichiometry for the competitive binding of ions. The ratio nM/nH is reflected in the corresponding exchange ratios and the pH dependence of the metal ion binding. Experimental complications occur in testing models. Although Model VI and the NICA-Donnan models have much in common, there are differences that may become more apparent as the models are more widely tested. Recently ion binding to complexes of humics and oxides has been described by combining the NICA-Donnan model (ion binding to humics) with the CD-MUSIC model (ion binding to oxides). The impact of humic to oxide binding on both cation and anion binding is briefly discussed.     

Conformational analysis of potent sweet taste ligands by nuclear magnetic resonance, computer simulations and X-ray diffraction studies

Four potent sweet-tasting molecules, N-(3,3-dimethylbutyl)-L-aspartyl-L-phenylalanine methylester 1 (7000 times more potent than sucrose), N-(3,3-dimethylbutyl)-L-aspartyl-D-valine (S)-alpha-ethylbenzylamide 2 (3000 time more potent than sucrose), L-aspartyl-D-valine (R)-alpha-methoxymethylbenzylamide 3 (1350 times more potent than sucrose and L-aspartyl-(1R,2S,4S)-1-methyl-2-hydroxy-4-phenylhexylamide 4 (2500 times more potent than sucrose) were studied by 1H NMR and computer simulations. These flexible molecules adopt multiple conformations in solution. The "L-shaped" structure, which we believe to be responsible for sweet taste is accessible to all four compounds in solution. Extended conformations with the AH and B-containing moieties in the +y-axis and the hydrophobic group X pointing in the y-axis have also been observed for all four sweeteners. For compounds 1 and 3, the solid-state conformations were determined by X-ray diffraction studies. These results demonstrate that compounds 1 and 3 adopt an "L-shaped" structure even in the crystalline state. The extraordinary potency of the N-alkylated compound 1 compared with the unsubstituted Asp-Phe-OMe may be explained by the effect of a second hydrophobic binding domain in addition to interactions arising from the "L-shaped" structure.     

Behavior of functional compounds during freeze concentration of tofu whey

The liquid waste generated from tofu production, denominated as Tofu Whey (TW), contains important amounts of isoflavones that can be evaluated by various separation techniques. In this work TW was concentrated by falling-film freeze concentration from 1.9 to 15.5 °Brix, up to levels of 208 mg of isoflavones per 100 g solids. The levels of isoflavones, proteins, sugars, calcium and magnesium were determined both in the ice and in the concentrate obtained. It was found by rheological characterization that TW shows a Newtonian behavior at concentrations between 1.9 and 15.5 °Brix with freezing points of −0.6 to −2.7 °C.