In vitro biological evaluation and molecular docking studies of natural and semisynthetic flavones from Gardenia oudiepe (Rubiaceae) as tyrosinase inhibitors.

Hyperpigmentation disorders are difficult to treat without causing permanent depigmentation or irritation. The most effective hypopigmenting agents are tyrosinase inhibitors, however some of those currently used have shown serious side effects. As several classes of flavonoids have already demonstrated ability to inhibit tyrosinase, a library of natural polymethoxyflavones isolated (1-7) from the bud exudate of Gardenia oudiepe and semi-synthetic derivatives (8,9) were evaluated. IC50 of the most active compounds were in the micromolar range. The strongest inhibitors 1, 2 and 3 all shared a 3',4'-dimethoxy-5'-hydroxy trisubstituted B ring. These SAR conclusions were confirmed by molecular docking studies. The mode of interaction with the enzyme was elucidated, and important interactions between the most active compounds and catalytic residues of tyrosinase were observed. All of these data provided a library of compounds as potential leaders for the design of new depigmenting agents and formulations.

Vibrational and structural behavior of (L)-cysteine ethyl ester hydrochloride in the solid state and in aqueous solution.

The aim of this work is to evaluate the vibrational and structural properties of l-cysteine ethyl ester hydrochloride (CE), and its electronic behavior mainly in relation to the action of the thiol and amine groups at different degrees of solvation. The crystal structure of CE was determined at room temperature by X-ray diffraction methods. Infrared and Raman spectra were collected to compare the behavior of different functional groups in the molecule, both in the solid phase and in aqueous solution. Its UV and circular dichroism spectra were also measured in aqueous solution. The influence of an aqueous environment on the CE spectra was simulated by means of implicit (polarizable continuum model) and explicit (molecular dynamics, solute-solvent clusters) methods. Calculations in explicit and continuous solvent are of interest to explain the behavior of bioavailable sites in this medium. The study was completed by natural bond orbital analysis to determine the presence of hyperconjugative interactions.

Active-feedback control of the magnetic boundary for magnetohydrodynamic stabilization of a fusion plasma.

Stable operation with control on magnetohydrodynamic modes has been obtained in the modified reversed field experiment employing a set of 192 feedback controlled saddle coils. Improvements of plasma temperature, confinement (twofold), and pulse length (threefold) and, as a consequence of the magnetic fluctuation reduction, strong mitigation of plasma-wall interaction and mode locking are reported.

Experimental and simulated neon spectra in the 10-nm wavelength region from tokamak and reversed field pinch plasmas.

Experimental neon spectra (in the 10-nm region), from the tokamak Tore Supra and the reversed field pinch experiment RFX, have been simulated. The spectra include lines from three neon ionization states, namely Ne(7+), Ne(6+), and Ne(5+) ions. Collisional radiative models have been built for these three Ne ions, considering electron collisional excitation and radiative decay as populating processes of the excited states. These models give photon emission coefficients for the emitted lines at electron density and temperature values corresponding to the experimental situations. Impurity modelling is performed using a one-dimensional impurity transport code, calculating the steady-state radial distribution of the Ne ions. The Ne line brightnesses are evaluated in a post-process subroutine and simulated spectra are obtained. The parts of the spectra corresponding to a single ionization state do not depend on the experimental conditions and show good agreement with the simulated single ionization state spectra. On the other hand, the superposition of the three spectra depends on the experimental conditions, as a consequence of the fact that the ion charge distribution depends not only on the radial profiles of the electron density and temperature, but also of the impurity transport coefficients. Simulations of the Ne spectra (including transport) give confidence in the atomic physics calculations; moreover, they allow the determination of the transport coefficients in the plasma region emitting the considered ionization states.