Casein proteolysis in human milk: tracing the pattern of casein breakdown and the formation of potential bioactive peptides

The protein and peptide fraction of human milk samples collected from mothers of pre- and full-term infants in the first week after parturition was analysed by use of liquid chromatography-mass spectrometry and tandem mass spectrometry. By characterising the peptide sequence, we defined the pathway of casein hydrolysis which leads to the formation of small peptides through intermediate oligopeptides. It was found that the action of a plasmin-like enzyme acting on specific lysine residues is the primary step in casein degradation. This is followed by endopeptidases and/or exopeptidases mediated cleavage of the oligopeptides which, in turn, produces a multiplicity of short peptides differing by one or more amino acid residues. In this process, a series of potentially bioactive peptides (opioid, phosphopeptides) and their precursors are produced.     

Sonochemical Synthesis and Structural Characterization and DFT Calculations of a Novel Nano Flower Pb(II) Coordination Compound [Pb(phen)2(4-abs)2]n

Nano-structures of a new coordination polymer of divalent Pb with the ligands 1,10-phenanthroline (phen) and 4-aminobenzene sulfonic acid (4-abs), [Pb(phen)₂(4-abs)₂]_n (1), were synthesized by a sonochemical method that produced a coordination polymer of nanometer size. The new nano-structure was characterized by scanning electron microscopy, X-ray powder diffraction and IR spectroscopy and elemental analysis. Compound 1 was structurally characterized by single crystal X-ray diffraction and showed that the coordination number of the Pb(II) ions is six; i.e. (PbN₄O₂). Compound 1 also has a stereochemically active lone pair of electrons and a hemi-directed coordination sphere. The chains interact with each other through π–π stacking to create a 3D framework. The structure of 1 was optimized by density functional theory calculations. The calculated structural parameters and IR spectra of 1 are consistent with the crystal structure.     

A New Family of Conformationally Constrained Bicyclic Diarylprolinol Silyl Ethers as Organocatalysts

Simple chemical manipulations of trans‐4‐L ‐hydroxy proline allow the access to a new family of bicyclic silyl ether organocatalysts that display some remarkable features. Apart from being extremely stable to hydrolytic conditions and possessing excellent catalytic performances, the rigidity of the bicyclic structure imposes a synclinal endo disposition of the bulky substituents with respect to the pyrrolidine ring, opposed to the more stable synclinal exo conformations of Jørgensen–Hayashi catalysts.     

Natural convection in horizontal annuli: a lower bound for the energy

Natural convection in the gap between two infinitely long horizontal coaxial cylindrical surfaces, each of which is maintained at constant temperature, is studied. If the inverse relative gap width is large, relevant steady convective flow and considerable heat transfer are observed, even for extremely small Rayleigh numbers Ra. A lower bound for the norm of the velocity and of the temperature is rigorously found by studying an approximation problem, which is a good model in the parameter range where steady stable flow occurs. The lower bound depends on only, and is an increasing function of . This means that the bound can be arbitrarily increased via the geometry only, no matter how small the temperature difference is, and independently of the Prandtl number Pr.     

Ozonation kinetics of cork-processing water in a bubble column reactor

The oxidative degradation of organic pollutants present in cork-processing water at natural pH (6.45) was studied in a bubble column ozonation reactor. A steady reduction in both chemical oxygen demand (COD) and total organic carbon (TOC) was observed under the action of ozone alone and the feasibility of deep mineralisation (organic matter removal more than 90% in 120 min under the following experimental conditions: liquid volume 9L; superficial gas velocity 6.8x10(-3) m s(-1); ozone partial pressure 1.31 kPa; initial COD 328 mg L(-1); initial TOC 127 mg L(-1)) was demonstrated. The monitoring of pH, redox potential (ORP) and the mean oxidation number of carbon (MOC) was correlated with the oxidation and mineralisation of the organic species in the water. The ozonation of cork-processing water in the bubble column was analysed in terms of a mole balance coupled with ozonation kinetics modelled by the two-film theory of mass transfer and chemical reaction. Under the experimental conditions used, and in contrast with the literature, it was determined that the reaction follows a fast kinetic regime at the beginning of the oxidation process, shifting to the moderate and the slow kinetic regimes at later stages of the oxidation reaction. The dynamic change of the rate coefficient estimated by the model was correlated to changes in the water composition.     

Modeling of an annular photocatalytic reactor for water purification: oxidation of pesticides

Photocatalytic oxidation (PCO) over titanium dioxide (TiO2) is a "green" sustainable process for the treatment and purification of water and wastewater. However, the application of PCO for wastewater treatment on an industrial scale is currently hindered by a lack of simple mathematical models that can be readily applied to reactor design. Current models are either too simplistic or too rigorous to be useful in photocatalytic reactor design, scale-up, and optimization. In this paper a simple mathematical model is presented for slurry, annular, photocatalytic reactors that still retains the essential elements of a rigorous approach while providing simple solutions. The model extends the applicability of the thin-film model of photocatalytic reactors previously presented to include the case of geometrically thick photoreactors (i.e., those reactors in which the thickness of the annular zone is significant as compared to the outer radius of the reactor). The model uses a novel six-flux absorption-scattering model to represent the radiation field in the reaction space, which assumes that scattered photons follow the route of the six directions of the Cartesian coordinates. The model was successfully validated with experimental results from the photocatalytic oxidation of the pesticide isoproturon in an experimental reactor. The mathematical model presented may be used as a tool for the design, scale-up, and optimization of annular photocatalytic reactors for water treatment and purification.     

Polychlorinated biphenyls, hexachlorobenzene, hexachlorocyclohexane isomers, and pesticide organochlorine residues in cod-liver oil dietary supplements

Levels of polychlorinated biphenyls (PCBs), hexachlorobenzene, hexachlorocyclohexane isomers (alpha, beta, gamma), and chlorinated pesticides (DDTs) in cod-liver oil used as a dietary supplement were determined. Total PCB and DDT concentrations varied from 25 to 201 ng g(-1) lipid weight basis and from 25 to 133 ng g(-1) lipid weight basis, respectively. Hexachlorobenzene contributed very little to the overall contaminant burden of dietary supplement oils, whereas hexachlorocyclohexane isomers were below the instrumental detection limits in all samples. The daily intake of PCBs and DDTs derived by the consumption of cod-liver oil at manufacturer-recommended doses varied from 0.004 to 2.01 microg/day and from 0.004 to 1.24 microg/day, respectively. Relative to some dioxin-like PCB congeners (mono-ortho PCB 105, 118, and 156; non-ortho PCB 77, 126, and 169), the intakes calculated varied from less than 0.001 to 0.74 pg of toxic equivalency values (TEQ) per kg of body weight per day. These values, although below the range of 1 to 4 pg of TEQ per kg of body weight per day set by the World Health Organization, emphasize the need for strict and continuous monitoring of fish oil contamination to reduce, as much as possible, the risks to human health.     

HCB, p,p'-DDE and PCB ontogenetic transfer and magnification in bluefin tuna (Thunnus thynnus) from the Mediterranean Sea

The bluefin tuna, Thunnus thynnus (Linnaeus 1758), is biologically and economically important in the Atlantic--Mediterranean ecosystems. Bluefin tuna feed on diverse food items depending on their age, thus they occupy different trophic levels during their lifespan. Hexachlorobenzene (HCB), p,p'-DDE and polychlorinated biphenyls (PCBs) are well-known persistent organic pollutants (POPs) in the Mediterranean basin. The relationship between stable isotopes of nitrogen (N) and the POP residue levels in tissues has recently increased knowledge on the link between the trophic levels and the contaminant accumulation. Trophic levels were estimated by using 15N/14N ratio (delta15N) and HCB, p,p'-DDE, and forty-three PCBs were quantified in bluefin tuna from the southern Tyrrhenian Sea. Results showed that changes in PCB and p,p'-DDE concentrations were a function of size and trophic level, while no correlations were observed for HCB. Apart from HCB and PCB nos. 101, 207, 95, 158, and 60 + 56, which did not show any significant increase per trophic level, the other PCBs and the p,p'-DDE increased significantly. The ontogenetic magnification factor of PCBs was 6.6 +/- 0.5, which was significantly (12 times) higher (p < 0.05) than the values found for p,p'-DDE (1.4) and HCB (1.4).     

The influence of local factors on the prediction of fumonisin contamination in maize

BACKGROUND: Contamination by mycotoxins is a major concern to the maize industry in north‐east Italy where maize grain is often spoiled by Fusarium spp. In this work, fumonisins, deoxynivalenol and zearalenone were determined and an artificial neural network (ANN) model suitable for predicting mycotoxin contamination of maize at harvest time was developed. RESULTS: The occurrence of deoxynivalenol and zearalenone was very limited, while fumonisins concentration ranged from 163 and to 3663 µg kg^?1 in 2007, and from 333 to 11473 µg kg^?1 in 2008. Statistical data analysis of factors affecting fumonisins concentration revealed that irrigation, chemical treatment against the European corn borer and harvest date significantly affected the level of contamination (P < 0.05), although the relevance of the factors was different in 2007 and 2008. The neural network approach showed a significant correlation between ascertained values and predictions based on agronomic data. CONCLUSION: This is the first time that an artificial neural network has been used to predict fumonisin accumulation in maize: the prediction has been shown to have the potential for the development of a new approach for the rapid cataloging of grain lots. Copyright © 2012 Society of Chemical Industry     

LNT: A logical neighbor tree secure group communication scheme for wireless sensor networks

Secure group communication is a paradigm that primarily designates one-to-many communication security. The proposed works relevant to secure group communication have predominantly considered the whole network as being a single group managed by a central powerful node capable of supporting heavy communication, computation and storage cost. However, a typical Wireless Sensor Network (WSN) may contain several groups, and each one is maintained by a sensor node (the group controller) with constrained resources. Moreover, the previously proposed schemes require a multicast routing support to deliver the rekeying messages. Nevertheless, multicast routing can incur heavy storage and communication overheads in the case of a wireless sensor network. Due to these two major limitations, we have reckoned it necessary to propose a new secure group communication with a lightweight rekeying process. Our proposal overcomes the two limitations mentioned above, and can be applied to a homogeneous WSN with resource-constrained nodes with no need for a multicast routing support. Actually, the analysis and simulation results have clearly demonstrated that our scheme outperforms the previous well-known solutions.