Determination of structure and 13C chemical shift assignments of the nitration products of 2-chloro-10-methylphenothiazine. X-Ray molecular structure of 2-chloro-7-nitro-10-methylphenothiazine 5-oxide

Nitration of 2-chloro-10-methylphenothiazine, 1 , yields two mono-nitro compounds identified as sulfoxide 2 and sulfone 3 . The nmr analyses of the ¹³C spectra of 2 and 3 establish unequivocally that in both compounds substitution has occurred at the seven position. This is supported by the X-ray crystal structure of one of the compounds 2-chloro-7-nitro-10-methylphenothiazine 5-oxide, 2 , which also shows that the sulfoxide group is in the “pseudo-axial” configuration. Crystals of 2 are monoclinic, space group P2₁/n, a = 11.606(4), b = 13.970(4)Å, c = 9.837(2), β = 127.49(2)° and Z = 4. The structure has been refined by full-matrix least-squares to R = 0.033 and R_w = 0.035, using 1704 observed reflections.     

Independent environmental monitoring and public dose assessment around the Canadian Nuclear Power Plants

Journal of Radioanalytical and Nuclear Chemistry - Radiological impact to members of the public living around the Canadian Nuclear Power Plants (NPPs) was assessed using environmental monitoring...     

Influence of Reynolds number on characteristics of turbulent wall boundary layers

Hot-wire anemometer measurements, using two types of probes, are reported for wall boundary layer flows with particular attention being given to the near-wall region and to measurements at high Reynolds numbers up to R 15,000. To obtain accurate near-wall measurements, the influence of wall proximity on hot-wire readings was eliminated by using a highly insulating wall material. Measurements were carried out with a single hot-wire boundary layer probe to obtain the longitudinal velocity informatemperature-wake sensor for the cross flow tion and a hot-wire, information.The results provided in the paper include measurements of averaged properties like mean velocity, rms-quantities of velocity fluctuations, probability density distributions etc. Conditional averages are also provided in order to yield information related to coherent flow structures present in boundary layer flows. It is shown that these structure remain present up to the highest Reynolds number investigated in the present study. The conditionally averaged data provide quantitative information on the mechanisms that are involved in the production of turbulence in boundary-layer flows.     

Energy-scalable pulsed mid-IR source using orientation-patterned GaAs

Coherent mid-IR sources based on orientation-patterned GaAs (OPGaAs) are of significant interest in diverse scientific, medical, and military applications. The generation of long-wavelength mid-IR beams in OPGaAs using optical parametric oscillation exhibits limitations in the obtainable pulse energy and peak power. The master oscillator power amplifier concept is demonstrated in OPGaAs, by which a mid-IR source based on optical parametric oscillation can be scaled to high energy by amplification of the output of the optical parametric oscillator in an optical parametric amplifier (OPA). A fivefold increase in the pulse energy is obtained using this method by amplifying 3.85μm pulses in an OPGaAs OPA pumped by a Th,Ho:YLF Q-switched laser.     

Monomer compartmentalisation in miniemulsion polymerisation studied by infrared spectroscopy

Miniemulsion polymerisations of styrene and butyl methacrylate were carried out in order to study mass transfer during the reaction. An in-line Attenuated Total Reflectance–Fourier Transform Infrared (ATR–FTIR) probe was used to follow the reactions, and the collected spectra were used to identify the different species that appeared and disappeared during polymerisation. The results show that the droplets were completely compartmentalized during the reaction, and that even when blends of droplets with different composition were polymerised together, no detectable levels of copolymer were formed. To cite this article: K. Ouzineb et al., C. R. Chimie 6 (2003).     

Substituent and solvent effects on tautomeric equilibria of barbituric acid derivatives and isoterically related compounds

N-Mono and N,N-dialkyl/diarylbarbituric acids exist in solution as a single tautomer. The ¹³C nmr spectroscopy shows that they are present in the triketo form in a number of polar and non-polar solvents. 2-Thiobarbituric acid derivatives, however, show extensive tautomerization. Their ¹³C chemical shift assignments were achieved by utilizing models 11a , 11c , 12b and 12d and from which relative tautomer distribution ratios were determined. These ratios were correlated with the dielectric constant of the various solvents (?). Thio-barbituric acids also formed adducts with solvents having carbonyl groups, characteristic observed only with barbiturates possessing the thione or thiophenolic group. 6-Amino and 6-methyluracils and thiouracils exist in DMSO solution as stable “ene” forms as do orotic acid, 24 , and its thio analogue 25. Compound 25 undergoes disproportionantion and tautomerization when heated or on prolonged standing in solution. Literature contradictions regarding the structure of “4,6-dihydroxypyrimidine,” 26 , were resolved and its tautomers in solution correctly assigned by ¹³C nmr. Anions of barbiturics and related systems exist in one of the two possible types A and B, depending on whether ring nitrogens are substituted (type A), or not (type B). Rapid H/D exchange at C₅ was evident from C-deuterium coupling. The redistribution of charge through C₄(C₆) carbonyl groups shown by ¹³C shifts of carbonyl carbon atoms of up to 10 ppm as compared to the CO carbons of the neutral species was evident.     

Breitbandige Lichtmodulation

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Cytochrome P450 BM-3 in complex with its substrate: Temperature-dependent spin state equilibria in the oxidized and reduced states

In structural studies of cytochrome P450 enzymes, substrates have been seen to bind in a variety of modes; it is important to identify those with the closest resemblance to the configurations adopted during selective oxidation. We attempt here to identify conditions in which the catalytic binding mode of cytochrome P450 BM-3 saturated with N-palmitoylglycine is highly populated. When the substrate binds directly atop the heme, primed for oxidation, displacement of the water ligand is necessary, and thereby the ferric heme is generally converted from low-spin to high-spin. Using both optical spectroscopy and solid-state nuclear magnetic resonance, studying both the full-length enzyme and the isolated heme domain, we show that a high population of the high-spin form is seen at room temperature and above, but not at reduced temperatures. In contrast, the reduced state exhibits high spin throughout the temperature range. The isotropic chemical shift of deuterons in the substrate bound to the oxidized and reduced forms of the enzyme was temperature-dependent, consistent with the presence of a nearby paramagnetic center, but temperature-independent for the diamagnetic CO-bound form, and for the free form of the compound. The reduced (ferrous heme) species shows Curie law dependence of the²H substrate chemical shift with respect to temperature from ?54 to +35 °C, but the oxidized (ferric heme) species showed a pronounced non-Curie dependence in both the²H and the¹³C shift of the substrate’s methyl group, with the effect of the paramagnetic heme at low temperatures being much reduced. These data are consistent with a mixture of at least two binding modes in rapid equilibrium wherein the heme is high-spin at room temperature but low-spin at cryogenic temperatures.