Predicting hydration free energies with chemical accuracy: the SAMPL4 challenge

An implicit solvent model described by a non-simple dielectric medium is used for the prediction of hydration free energies on the dataset of 47 molecules in the SAMPL4 challenge. The solute is represented by a minimal parameter set model based on a new all atom force-field, named the liquid simulation force-field. The importance of a first solvation shell correction to the hydration free energy prediction is discussed and two different approaches are introduced to address it: either with an empirical correction to a few functional groups (alcohol, ether, ester, amines and aromatic nitrogen), or an ab initio correction based on the formation of a solute/explicit water complex. Both approaches give equally good predictions with an average unsigned error <1 kcal/mol. Chemical accuracy is obtained.     

Heteroaromatic boron compounds. XV. Deuteriodeprotonation in some borazarothienopyridines and thienopyridines

Deuteriodeprotonation of some substituted 4,5-borazarothieno[2,3-c]pyridines (I) and 7,6-borazarothieno[3,2-c]pyridines (II) has been studied by the nmr technique. Exchange occurred predominantly in the 3-position, and the effect of methyl substitution on rate is discussed. The rates of exchange in some derivatives of I and II were compared with those of the isoelectronic thieno[2,3-c]pyridines (III) and thieno[3,2-c]pyridines (IV). Similar rates were obtained, confirming the aromatic nature of I and II. The deuteriodeprotonation of 4-methyl-4,5-borazaro-thieno[2,3-c]pyridine (Ie), 7-methyl-7,6-borazarothieno[3,2-c]pyridine (IIe), 4-methylthieno-[2,3-c]pyridine (IIIe), and 7-methylthieno[3,2-c]pyridine (IVe) were measured at different concentrations of deuteriosulfuric acid and different temperatures, showing that the protonated heterocycles are substrates in the deuteriodeprotonation reaction. Standard rates at p0 H and 100° were calculated for these systems.     

meso-Arylporpholactones and their Reduction Products

The rational syntheses of meso-tetraaryl-3-oxo-2-oxaporphyrins 5, known as porpholactones, via MnO(4)(-)-mediated oxidations of the corresponding meso-tetraaryl-2,3-dihydroxychlorins (7) is detailed. Since chlorin 7 is prepared from the parent porphyrin 1, this amounts to a 2-step replacement of a pyrrole moiety in 1 by an oxazolone moiety. The stepwise reduction of the porpholactone 5 results in the formation of chlorin analogues, meso-tetraaryl-3-hydroxy-2-oxachlorin (11) and meso-tetraaryl-2-oxachlorins (12). The reactivity of 11 with respect to nucleophilic substitution by O-, N-, and S-nucleophiles is described. The profound photophysical consequences of the formal replacement of a pyrrole with an oxazolone (porphyrin-like chromophore) or (substituted) oxazole moiety (chlorin-like chromophore with, for the parent oxazolochlorin 12, red-shifted Q(x) band with enhanced oscillator strengths) are detailed and rationalized on the basis of SAC-CI and MNDO-PSDCI molecular orbital theory calculations. The single crystal X-ray structures of the porpholactones point at a minor steric interaction between the carbonyl oxygen and the flanking phenyl group. The essentially planar structures of all chromophores in all oxidation states prove that the observed optical properties originate from the intrinsic electronic properties of the chromophores and are not subject to conformational modulation.     

Flexible active matrix addressed displays manufactured by printing and coating techniques

A flexible electrochromic active matrix addressed display, including 8 × 8 pixels, is demonstrated by using solution processing based on standard printing and coating manufacturing techniques. Each organic electrochromic display (OECD) pixel and its corresponding organic electrochemical transistor (OECT) are located on different sides of the flexible PET substrate. Electronic vias generated through the plastic substrate connects each OECD pixel with one addressing OECT. When comparing this display with actively addressed OECDs with all its components located on the same side, the present approach based on this electronic via substrate provides an enhanced pixel resolution and a relatively more simplified manufacturing process. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012     

Determination of reactor neutron spectra with multicomponent activation detectors

A procedure is described for the functional fitting of reactor neutron spectra with C/Eⁿ and fission spectra. The method is applied to multicomponent activation detector measurements in a Triga research reactor. In multicomponent detectors a mixture of several detector materials is irradiated as a single unit and measured simultaneously for all reaction products with a Ge(Li) gamma ray spectrometer.     

Separation of oxidized and deamidated human growth hormone variants by isocratic reversed-phase high-performance liquid chromatography.

Reversed-phase high-performance liquid chromatography (RP-HPLC) was utilized for the separation of recombinant human growth hormone (hGH) variants on a C18 silica column at 55 degrees C using an isocratic mobile phase which contained 27% 1-propanol in a 25 mM potassium phosphate buffer, pH 6.5. Three of the obtained peaks were characterized by tryptic mapping and mass spectrometry; two of the peaks were found to contain oxidized hGH (dioxy Met14/Met125 and Met125 sulfoxide) while the third contained a deamidated form (Asn149-->Asp149 or Asn152-->Asp152). Compared to the European Pharmacopoeia RP-HPLC method of hGH analysis, this new method gives two additional peaks and a 50% reduction in the analysis time.     

Synthesis and some chemical properties of 3,3,4,4-tetraethoxybut-1-yne

Ring opening of 1,1-dibromo-2-chloro-2-diethoxymethylcyclopropane in a mixture of ethanol and dichloromethane with 50% aqueous sodium hydroxide in the presence of triethylbenzylammonium chloride (TEBA) gave 3,3,4,4-tetraethoxybut-1-yne (TEB) in excellent yield. This alkyne appears to be thermally stable at least up to 150 °C. The compound is also stable in neutral and basic aqueous solutions. In acidic aqueous media, however, TEB is unstable and was converted to one or several products depending on the reaction conditions. The most useful reaction appears to be deketalization to give 1,1-diethoxybut-3-yn-2-one, which was obtained in quantitative yield under the optimum conditions.