Superior Antibacterial Activity of Integral Lemon Pectin Extracted via Hydrodynamic Cavitation

Pectin extracted via hydrodynamic cavitation in water only from waste lemon peel and further isolated via freeze drying displays significant antibacterial activity against Staphylococcus aureus, a Gram positive pathogen which easily contaminates food. The antibacterial effect of the new IntegroPectin is largely superior to that of commercial citrus pectin, opening the way to advanced applications of a new bioproduct now obtainable in large amounts and at low cost from citrus juice industry's waste.     

Semiconductor Quantum Dots as Components of Photoactive Supramolecular Architectures

Luminescent quantum dots (QDs) are colloidal semiconductor nanocrystals consisting of an inorganic core covered by a molecular layer of organic surfactants. Although QDs have been known for more than thirty years, they are still attracting the interest of researchers because of their unique size-tunable optical and electrical properties arising from quantum confinement. Moreover, the controlled decoration of the QD surface with suitable molecular species enables the rational design of inorganic-organic multicomponent architectures that can show a vast array of functionalities. This minireview highlights the recent progress in the use of surface-modified QDs – in particular, those based on cadmium chalcogenides – as supramolecular platforms for light-related applications such as optical sensing, triplet photosensitization, photocatalysis and phototherapy.     

Involvement of Proton Transfer for Carbon Dioxide Reduction Coupled with Extracellular Electron Uptake in Shewanella oneidensis MR‐1

Microbial biosynthesis of hydrocarbon from CO₂ reduction driven by electron uptake process from the cathodic electrode has gained intensive attention in terms of potential industrial application. However, a lack of a model system for detailed studies on the mechanism of the CO₂ reduction hinders the improvement in efficiency for microbial electrosynthesis. Here, we examined the mechanism of microbial CO₂ reduction at the cathode by a well‐described microbe for extracellular electron uptake, Shewanella oneidensis MR‐1, capable of reducing gaseous CO₂ to produce formic acid. Using whole‐cell electrochemical assay, we observed stable cathodic current production at ?0.65 V vs Ag/AgCl KCl sat. associated with the introduction of CO₂. The observed cathodic current was enhanced by the addition of 4 μM riboflavin, which specifically accelerates the electron uptake process of MR‐1 by the interaction to its outer‐membrane c‐type cytochromes. The significant impact of an uncoupler agent and a mutant strain of MR‐1 lacking sole F‐type ATPase suggested the importance of proton import to the cytoplasm for the cathodic CO₂ reduction. The present data suggest that MR‐1 potentially serves as a model system for microbial electrosynthesis from CO₂.     

The Elusive Ketene (H2CCO) Channel in the Infrared Multiphoton Dissociation of Solid 1,3,5-Trinitro-1,3,5-Triazinane (RDX)

Understanding of the fundamental mechanisms involved in the decomposition of 1,3,5-trinitro-1,3,5-triazinane (RDX) still represents a major challenge for the energetic materials and physical (organic) chemistry communities mainly because multiple competing dissociation channels are likely involved and previous detection methods of the products are not isomer selective. In this study we exploited a microsecond pulsed infrared laser to decompose thin RDX films at 5 K under mild conditions to limit the fragmentation channels. The subliming decomposition products during the temperature programed desorption phase are detected using isomer selective single photoionization time-of-flight mass spectrometry (PI-ReTOF-MS). This technique enables us to assign a product signal at m/z=42 to ketene (H₂CCO), but not to diazomethane (H₂CNN; 42 amu) as speculated previously. Electronic structure calculations support our experimental observations and unravel the decomposition mechanisms of RDX leading eventually to the elusive ketene (H₂CCO) via an exotic, four-membered ring intermediate. This study highlights the necessity to exploit isomer-selective detection schemes to probe the true decomposition products of nitramine-based energetic materials.     

Lyapunov exponent for Lipschitz maps

Nonlinear Dynamics - It is well known that the Lyapunov exponent plays a fundamental role in dynamical systems. In this note, we propose a definition of Lyapunov exponent for Lipschitz maps, which...     

1H NMR detection of immobilized water molecules within a strong distal hydrogen-bonding network of substrate-bound human heme oxygenase-1

Solution 1H NMR is used to probe the environments of the donor protons of eight strong hydrogen bonds on the distal side of the heme substrate in the cyanide-inhibited, substrate-bound complex of human heme oxygenase, hHO. It is demonstrated that significant magnetization transfer from the bulk water signal to the eight labile protons does not result from chemical exchange, but from direct nuclear Overhauser effect due to the dipolar interaction of these labile protons with "ordered" water molecules. The enzyme labile proton to water proton distances are estimated at approximately 3 A. It is proposed that the role of the strong hydrogen-bonding network is to immobilize numerous water molecules which both stabilize the activated hydroperoxy species and funnel protons to the active site.     

Cationic beta-cyclodextrin bilayer vesicles

Cationic amphiphilic beta-cyclodextrins, substituted with hydrophobic n-alkylthio chains at the primary hydroxyl side and hydrophilic omega-amino-oligo(ethylene glycol) units at the secondary side, form bilayer vesicles with a diameter of 30-35 nm (when alkyl = hexadecyl) or nanoparticles with a diameter of ca. 120 nm (when alkyl = hexyl) in water.