Liquid–Liquid Equilibria of Linalool + Ethanol + Water, Water + Ethanol + Limonene, and Limonene + Linalool + Water Systems

The present work was undertaken to determine liquid–liquid equilibria for ternary systems involved in the citrus essential oil terpeneless using dilute alcohol. Tie-line data have been determined for the linalool + ethanol + water, water + ethanol + limonene, and limonene + linalool + water ternary systems at 298.15 K. The experimental data were satisfactorily correlated using the UNIQUAC and NRTL equations, and the obtained binary interaction parameters are reported. The UNIFAC group-contribution method did not allow adequate predictions of liquid–liquid equilibria involved in this study.     

Regiochemistry of the photostimulated reaction of the phthalimide anion with 1-iodoadamantane and tert-butylmercury chloride by the S(RN)1 mechanism

The photostimulated reaction of the phthalimide anion (1) with 1-iodoadamantane (2) gave 3-(1-adamantyl) phthalimide (3) (12%) and 4-(1-adamantyl) phthalimide (4) (45%), together with the reduction product adamantane (AdH) (21%). The lack of reaction in the dark and inhibition of the photoinduced reaction by p-dinitrobenzene, 1,4-cyclohexadiene, and di-tert-butylnitroxide indicated that 1 reacts with 2 by an S(RN)1 mechanism. Formation of products 3 and 4 occurs with distonic radical anions as intermediates. The photoinduced reaction of anion 1 with tert-butylmercury chloride (10) affords 4-tert-butylphthalimide (11) as a unique product. By competition experiments toward 1, 1-iodoadamantane was found to be ca. 10 times more reactive than tert-butylmercury chloride.     

Selective synthetic routes to sterically hindered unsymmetrical diaryl ketones via arylstannanes

Bulky arylstannanes and bulky aroyl chlorides are good reaction partners for the synthesis of two-, three-, and even four-ortho-substituted benzophenones, in good to excellent isolated yields (47-91%). Three simple and direct routes, with differential advantages, are proposed: (i) a catalyst-free protocol, in o-dichlorobenzene (ODCB) at 180 °C; (ii) a room temperature protocol, using AlCl(3) (0.5 equiv), in dichloromethane (DCM); and (iii) a solvent-free, indium-promoted procedure. A radical mechanism is proposed for the indium-mediated reactions.     

An orbital localization criterion based on the theory of "fuzzy" atoms

This work proposes a new procedure for localizing molecular and natural orbitals. The localization criterion presented here is based on the partitioning of the overlap matrix into atomic contributions within the theory of "fuzzy" atoms. Our approach has several advantages over other schemes: it is computationally inexpensive, preserves the sigma/pi-separability in planar systems and provides a straightforward interpretation of the resulting orbitals in terms of their localization indices and atomic occupancies. The corresponding algorithm has been implemented and its efficiency tested on selected molecular systems.     

New insights on the behavior of PRODAN in homogeneous media and in large unilamellar vesicles

The behavior of 6-propionyl-2-dimethylaminonaphthalene (PRODAN) was studied in homogeneous media and in large unilamellar vesicles (LUVs) of the phospholipid 1,2-di-oleoyl-sn-glycero-3-phosphatidylcholine (DOPC), using absorption, emission, depolarization, and time-resolved spectroscopies. In homogeneous media, the Kamlet and Taft solvatochromic comparison method quantified solute-solvent interactions from the absorption and emission PRODAN bands. These studies demonstrate that the absorption band is sensitive to the polarity-polarizability (pi) and the hydrogen bond donor ability (alpha) parameters of the media. PRODAN in the excited state is even more sensitive to these parameters and to the hydrogen bond acceptor ability (beta) of the media. The transition energy (expressed in kcal/mol) for both absorption and emission bands gives a linear correlation with the well-known polarity parameter E(T30). The results from the absorption and emission bands also reveal that PRODAN aggregates in water. The monomer has two fluorescence lifetimes, 2.27 and 0.65 ns, while the aggregate has a lifetime of 14.6 ns. Using steady-state anisotropy measurements, the calculated volumes of the aggregate and the monomer are 5590 and 222 mL mol(-1), respectively. In DOPC LUVs, PRODAN undergoes a partition process between the water bulk and the DOPC bilayer. We show that the partition constant (K(p)) value is large enough that only at [DOPC] below 0.15 mg/mL PRODAN in water can be detected. PRODAN dissolved in LUVs at [DOPC] > 1 mg/mL exists completely incorporated in its monomer form and senses two different microenvironments within the bilayer: a polar region in the interface near the water and a less polar and also less viscous environment, between the phospholipid tails. These environments were characterized by their fluorescence lifetimes (tau), showing that PRODAN in the polar microenvironment has a tau value of approximately 4 ns while in the less polar region gives a value of 1.2 ns. Moreover, this probe also senses the micropolarity of these two different regions of the bilayer and yields values similar to that of methanol and tetrahydrofuran.     

Porphyrin-sensitized nanoparticulate TiO2 as the photoanode of a hybrid photoelectrochemical biofuel cell

Porphyrin-sensitized nanoparticulate TiO(2) on conducting glass has been investigated as a photoanode material for a new cell that converts light energy into electricity. The cell is a hybrid of a dye-sensitized nanoparticulate semiconductor photoelectrochemical solar cell, and a biofuel cell that oxidizes glucose. Porphyrin molecules excited by light inject electrons into the photoanode, from where they enter the external circuit. The resulting porphyrin radical cations are reduced by NADH in aqueous buffer, ultimately regenerating the photoanode and producing NAD(+). Glucose dehydrogenase oxidizes glucose, and in the process recycles NAD(+) back to NADH. The photoanode is coupled with a suitable cathode to make a functioning cell (Hg/Hg(2)SO(4) was employed for evaluation purposes). The cell produces 1.1 V at open circuit and has a fill factor of 0.61. These values are both significantly higher than those for a previously reported cell of a similar type based on an SnO(2) electrode.     

The chemical modification of liposome surfaces via a copper-mediated [3 + 2] azide-alkyne cycloaddition monitored by a colorimetric assay

A generic method for the efficient in-situ modification of liposomes is described based on "click" chemistry, and a simple colorimetric assay is developed for monitoring the reaction.     

Enzymatic Hydrolysis of Agavins to Generate Branched Fructooligosaccharides (a-FOS<Emphasis Type="Bold">)</Emphasis>

Recently, agavins (branched neo-fructans) of short degree of polymerization have shown beneficial effects on the health of both healthy and overweight individuals. Therefore, the aim of the present work was to investigate the potential use of Agave angustifolia agavins on the generation of branched fructooligosacharides (a-FOS). A. angustifolia agavins were hydrolyzed using exo-, endo-inulinase, and a mixture of both (25 and 75%, respectively). Exo- and the inulinase mixture degraded quickly the agavins in relation to endo-inulinase treatment. Only endo-inulinase and the inulinase mixture generated a-FOS formation. Endo-inulinase degraded 31% of agavins, yielding approximately 20% of a-FOS after 48 h, whereas the inulinase mixture hydrolyzed 33% of agavins in just 90 min, but only yielded 10% of a-FOS. These results suggest that agave plants could be an abundant raw material for a-FOS production, which might have a huge prebiotic potential as new branched fructooligosaccharides with many applications in the alimentary and pharmaceutical industry.     

Complex salts of [ReII(NO)Br4(pyz)]−: synthesis,crystal structures,and DFT studies

Two nitrosyl Re(II) complexes formulated as [Ni(bipy)₃][Re(NO)Br₄(pyz)]₂ and [Cu(bipy)₂Br][ReNOBr₄(pyz)] (pyz = pyrazine, bipy = 2,2′-bipyridine) were synthesized and characterized by single-crystal X-ray diffraction. The pyrazine in [Re(NO)Br₄(pyz)]^? was not able to act as bridge toward a second metal ion, and the two salts were obtained. Computational studies at the density functional level of theory show that the charge on the nitrogen, which could be available for bridging, is dramatically reduced to less than half, decreasing its capability to bind a second metal ion.     

Synchronization structure of evolving epileptic networks using cross-entropy

In this paper we present connectivity patterns of evolving large scale epileptic networks. We employed a cross-entropy measure in the frequency domain on EEG signals to infer the networks, before and during episodes of epileptic seizures. This measure allowed us to make a richer portrait about the node interactions on the graph and to identify emergent structures associated with the synchronization of brain activity. Our results points to a more complex scenario of network organization than the synchronized/unsynchronized dichotomy, with two main results: first, showing regions with unsynchronized (or independent) behavior, even during absence seizures, contradicting the concept of hypersynchrony. Furthermore, we explore the cross-entropy fluctuations along the seizure: a group of nodes became more similar over time while another group became more different, showing a complementary behaviour and different local brain activities. These results bring new questions about the spreading and the sustenance of the epileptic seizures and others synchronization phenomena in living systems.