Preparation of novel analgesics via diastereoselective nucleophilic addition to 1-dimethylamino-2-methylpentan-3-one

The diastereoselective synthesis of naphthyl amino alcohols via nucleophilic addition to racemic 1-dimethylamino-2-methylpentan-3-one was studied. The use of the appropriate experimental conditions allowed the synthesis of both diastereoisomers. The relative configurations were established via NOESY experiments.     

Polyelectrolyte complexes. VI. Polycation structure,polyanion molar mass,and polyion concentration effects on complex nanoparticles based on poly(sodium 2‐acrylamido‐2‐methylpropanesulfonate)

The formation and characterization of some interpolyelectrolyte complex (IPEC) nanoparticles based on poly(sodium 2‐acrylamido‐2‐methylpropanesulfonate) (NaPAMPS), as a function of the polycation structure, polyanion molar mass, and polyion concentration, were followed in this work. Poly(diallyldimethylammonium chloride) and two polycations (PCs) containing (N,N‐dimethyl‐2‐hydroxypropyleneammonium chloride) units in the backbone (PCA₅ and PCA₅D₁) were used as starting polyions. The complex stoichiometry, (n^?/n⁺)_iso, was pointed out by optical density at 500 nm (OD₅₀₀), polyelectrolyte titration, and dynamic light scattering. IPEC nanoparticle sizes were influenced by the polycation structure and polyanion molar mass only before the complex stoichiometry, which was higher for the more hydrophilic polycations (PCA₅ and PCA₅D₁) and for a higher NaPAMPS molar mass, and were almost independent of these factors after that, at a flow rate of the added polyion of about 0.28 mL × (mL PC)^?1 × h^?1. The IPEC nanoparticle sizes remained almost constant for more than 2 weeks, both before and after the complex stoichiometry, at low concentrations of polyions. NIPECs as stable colloidal dispersions with positive charges in excess were prepared at a ratio between charges (n^?/n⁺) of 0.7, and their storage colloidal stability, as a function of the polycation structure and polyion concentration (from 0.8 to ca. 7.8 mmol/L), was demonstrated. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2495–2505, 2004     

The effect of the external lateral electric field on the luminescence intensity of InAs/GaAs quantum dots

We report on low-temperature microphotoluminescence (μ-PL) measurements of InAs/GaAs quantum dots (QDs) exposed to a lateral external electric field. It is demonstrated that the QDs’ PL signal could be increased severalfold by altering the external and/or the internal electric field, which could be changed by an additional infrared laser. A model which accounts for a substantially faster lateral transport of the photoexcited carriers achieved in an external electric field is employed to explain the observed effects. The results obtained suggest that the lateral electric fields play a major role for the dot luminescence intensity measured in our experiment—a finding which could be used to tailor the properties of QD-based optoelectronic applications. The text was submitted by the authors in English.     

The gas phase reaction between CO2 and lanthanide atoms. A test of a model for the isokinetic effect

Summary Co₃O₄, NiCo₂O₄ and LaCo₂O₄catalysts were synthesizedby the citric acid-ligated method. These catalysts containing Co-oxide active components can largely lower the temperature of soot combustion under tight contact conditions. Under the conditions of loose contact NiCo₂O₄ cannot promote soot combustion, but LaCo₂O₄ can effectively promote soot combustion because the nanometric perovskite-type catalyst LaCoO₃produced in the LaCo₂O₄sample.</o:p>     

Coulometric determination of NAD+ and NADH in normal and cancer cells using LDH, RVC and a polymer mediator

An electrochemical method for the measurement of NAD(+) and NADH in normal and cancer tissues using flow injection analysis (FIA) is reported. Reticulated vitreous carbon (RVC) electrodes with entrapped l-lactate dehydrogenase (LDH) and a new redox polymer containing covalently bound toluidine blue O (TBO) were employed for this purpose. Both NAD(+) and NADH were estimated coulometrically based on their reaction with LDH. The latter was immobilized on controlled pore glass (CPG) by cross-linking with glutaraldehyde and packed within the RVC. The concentrations of NAD(+) and NADH in the tissues, estimated using different electron mediators such as ferricyanide (FCN), meldola blue (MB) and TBO have also been compared. The effects of flow rate, pH, applied potential (versus Ag/AgCl reference) and adsorption of the mediators have also been investigated. Based on the measurements of NAD(+) and NADH in normal and cancer tissues it has been concluded that the NADH concentration is lower, while the NAD(+) concentration is higher in cancer tissues. Amongst the electron mediators TBO was found to be a more stable mediator for such measurements.     

Low Temperature Sol-Gel Preparation of Nanocrystalline TiO2 Thin Films

TiO₂ nanocrystalline thin films with varying degree of porosity have been prepared using a low temperature method. TiO₂ films of the anatase form have been obtained by using a polyethylene glycol (PEG) modified sol-gel method. Densification and crystallization of the films was found to result from the thermal treatment of the dip coated films in boiling water. The films have been characterized by Raman, XRD, FTIR, AFM and optical methods. Highly transparent films with transmission in excess of 85% and porosity as high as 58% are formed predominantly of anatase crystallites of dimensions of the order of 5 nm. Initial results on lithium intercalation into these films resulting in an efficient optical modulation in the visible and near infrared regions demonstrate a good potential of these films for electrochromic applications.     

Conversions between ordered and disordered cellulose. Effects of mechanical treatment followed by cyclic wetting and drying

An investigation into the effects of mechanical treatment and hydration on the order of cellulose substrates (microcrystalline cellulose and Cladophora cellulose) was performed by the use of ball milling followed by cyclic wetting and drying. The results, monitored by¹³C-CP/MAS NMR-spectroscopy, were evaluated by calculation of the crystallinity indices and principal component analysis of the NMR data acquired. The results showed that a large part of the disorder induced by the mechanical treatment of cellulose by ball milling is reversible and reordering upon hydration leads to the cellulose I form initially present. The C4 signals corresponding to the reversibly disordered cellulose chains are observed in the amorphous region between 79 and 86 ppm in the¹³C-CP/MAS NMR-spectra together with signals from cellulose chains on the surface of ordered regions. The peak cluster which contains the C2, C3 and C5 ring carbons can be divided into two specific spectral regions; one between 74 and 77 ppm largely originates from ring carbons within disordered cellulose structures, and one between 70 and 74 ppm contains larger contributions from ordered cellulose. The behaviour of the celluloses upon milling is in accordance with a concept of ordered cellulose fibrils containing amorphous cellulose mainly as surface layers and induced reversible lattice distortions.     

2-(2-Hydroxyaryl)cinnamic amides: a new class of axially chiral molecules

The syntheses of several differently substituted amides formally derived from a chiral amine, either E-2-(2-hydroxyphenyl)cinnamic acid or both E- and Z-2-(2-hydroxynaphthyl)cinnamic acid, are reported. These molecules display a restricted rotation about the C₂-C_aryl bond. The barriers to rotation about the C₂-C_aryl bond were measured by the dynamic ¹H NMR and were found to vary between 11.8 and 24.5 kcal mol⁻¹, depending on the substitution. In particular, E-2-(2-hydroxynapthyl)cinnamic amides, displayed a high barrier to rotation (ΔG_c^‡=24.4 kcal mol⁻¹) and could be isolated in both diastereomerically pure forms at room temperature. The X-ray structure of one E-2-(2-hydroxynapthyl)cinnamic amide, was resolved, enabling for the determination of the absolute configuration of the chiral axis (aR).