Rotational and hyperfine structure in the yellow system of CuF

Previous spectroscopic studies of copper monofluoride have suggested that the excited electronic state involved in the yellow system is either ³Σ^? or a (¹Π, ¹Σ) “p-complex”. A Doppler-limited (HWHM ? 0.4 GHz), laser-induced fluorescence study of the (0, 0) band of the ⁶³Cu¹⁹F isotopic species was performed in order to make a more definite assignment of the upper state. As a result of increased resolution, many of the rotational lines appear as partially resolved quartets resulting from the ⁶³Cu ($\text{I =}\text{3}\text{2}$) nuclear hyperfine splitting. It was not possible on the evidence available to decide between the alternative assignments for the upper state. Assuming a ³Σ^? state, 200 features were assigned, measured, and fitted by a least-squares procedure to determine values for the parameters (cm^?1) of CuF in the excited state: T₀ = 17 574.9663(12), λ₀ = ? 27.7149(11), λ_D0 = 0.001161(1), B₀ = 0.375035(2), 10⁶D₀ = 0.510(1), γ₀ = 0.01074(6), $\text{b}{}_{\mathrm{F}}\text{(}{}^{63}\text{Cu}\text{) = 0.032(2)}$, $\text{c(}{}^{63}\text{Cu}\text{) = ?0.039(7)}$. The ⁶³Cu hyperfine parameters are interpreted in terms of possible electronic models of CuF in the A state.     

Gas chromatographic-mass spectrometric quantitation of tri-, di- and monomethylxanthines and uric acids from hepatocyte incubation media

A gas chromatographic-mass spectrometric method is described for the measurement of the concentration of fourteen methylxanthines and methyluric acid metabolites of methylxanthines, especially caffeine, from cell incubation media. The method shows linearity, accuracy and recovery suitable for metabolic studies. The reproducibility of relative retention times is satisfactory (less than 0.07%) and allows rapid and conclusive identification of chromatographic peaks corresponding to metabolites. Moreover, this method enables the simultaneous determination of 3.7-methylxanthine and its 1.7-isomer, which are not chromatographically resolved. This method can be successfully applied when molecules labelled with stable isotopes are used as tracers for metabolic studies.     

Can Dispersion Forces Govern Aromatic Stacking in an Organic Solvent?

Experimental support for the dominance of van der Waals dispersion forces in aromatic stacking interactions occurring in organic solution is surprisingly limited. The size‐dependence of aromatic stacking in an organic solvent was examined. The interaction energy was found to vary by about 7.5 kJ mol^?1 on going from a phenyl–phenyl to an anthracene–pyrene stack. Strikingly, the experimental data were highly correlated with dispersion energies determined using symmetry‐adapted perturbation theory (SAPT), while the induction, exchange, electrostatic, and solvation energy components correlated poorly. Both the experimental data and the SAPT‐dispersion energies gave high‐quality correlations with the change in solvent accessible area upon complexation. Thus, the size‐dependence of aromatic stacking interactions is consistent with the dominance of van der Waals dispersion forces even in the presence of a competing polarizable solvent.     

[13C]Aminopyrine and [13C]Caffeine Breath Test: Influence of Gender,Cigarette Smoking and Oral Contraceptives Intake

Abstract

The [¹³C]aminopyrine breath test ([¹³C]ABT) measures the global activity of cytochrome P450 in vivo and is a sensitive indicator of liver metabolic dysfunction. The present study aims to determine whether gender and cigarette smoking influence the results of [¹³C]ABT as well as to confirm the effect of oral contraceptive steroids (OCS) intake on this metabolic test. Hundred and ten healthy subjects, including men and women, smoker and non-smoker, women taking OCS or not, were phenotyped for CYP1A2 using the [¹³C]caffeine breath test and underwent a [¹³C]ABT. Both tests showed large inter-individual variations in accordance with that of CYP450 liver content. [¹³C]ABT was sensitive enough to point out a significant induction or inhibition related to cigarette smoking habits or OCS. The combined effect of smoking and OCS resulted in an overall unchanged metabolic activity. Consequently, the impact of the studied conditions on the [¹³C]ABT parameters must be considered by clinicians or clinical investigators.     

2(1H)-pyridinone (2-pyridone): self-association and association with water. Spectral and structural characteristics: infrared study and ab initio calculations

DFT calculations of 2(1H)-pyridinone (2-pyridone NHP), the centrosymmetric dimer (NHP)2 and the closed complexes (NHP, H2O) and (NHP, 2H2O), with their deuterated homologues NDP, (NDP)2, (NDP, D2O) and (NDP, 2D2O), are compared with vibrational spectra of NHP and NDP in ternary mixtures CH3CN, NHP, H2O. Experimental data are also obtained for NHP or NDP in various solvents. The protic solvent effects demonstrate that mechanical couplings are different in the 1500-1700 cm(-1) range for the nuC=O and nu8b (valence of the ring) modes in NHP and NDP (or (NHP, H2O) and (NDP, D2O)). For the first time, data are obtained for NDP in the dimer (NHP, NDP). Comparison of data for pyridone, monomer, dimer or complexed with water, shows that in the complexes, water is a weaker proton acceptor and a stronger proton donor than a second pyridone molecule in the centrosymmetric dimer.