Comments on “isothermal sustained oscillations in a very simple surface reaction” by C.G. Takoudis,L.D. Schmidt and R. Aris

The oscillating CO oxidation on Pt is examined as a possible candidate for the Takoudis, Schmidt and Aris (TSA) model. Moreover the results of our Monte Carlo simulation of this model reaction are tentatively compared to TSA numerical results.     

Three-component synthesis of benzo[b][1,5]thiazepines via coupling–addition–cyclocondensation sequence

2,4-Disubstituted benzo[b][1,5]thiazepines represent nonfluorescent intense yellow chromophores and are readily synthesized from acid chlorides, terminal alkynes, and ortho-amino thiophenols by a consecutive one-pot three-component Sonogashira coupling–Michael addition–cyclocondensation sequence under mild conditions in good yields.     

Optimal L ∞-Error Estimate of a Finite Element Method for Hamilton–Jacobi–Bellman Equations

This paper is concerned with the piecewise linear finite element approximation of Hamilton–Jacobi–Bellman equations. We establish the optimal L ^∞-error estimate, combining the concepts of subsolution and discrete regularity.     

Behaviour of vicinal InP surfaces grown by MOVPE: exploitation of AFM images

InP substrates and epilayers grown by MOVPE have been studied by AFM. For different misorientation angles, we observed the surface of the substrate after annealing under phosphine (PH₃) and of the epilayers under different growth conditions such as growth temperature T_g and trimethylindium (TMI) partial pressure. After annealing the terrace width corresponds to the nominal value of misorientation angle measured by X-ray diffraction. We observed different topographies and roughnesses for the grown layers corresponding to different growth modes. We propose, taking into account the roughness of the surface, a calculation of the step height and terrace width. For 2D nucleation (θ ≤ 0.2° and T_g = 500°C) and step flow mode, the roughness is low while it is increased by step bunching (θ ≥ 0.5° and T_g ≥ 580°C). Moreover we have examined the surface morphology for different misorientation angles and determined the influence of growth conditions (growth temperature, indium partial pressure) on the growth mechanism. At T_g = 580°C the increase of the TMI partial pressure in the reactor enhances the step bunching and leads to larger terraces.     

Factors governing electron capture by small disulfide loops in two-cysteine peptides

Integrated molecular orbital-molecular orbital (IMOMO) calculations on 17 short disulfide-bridged peptides (up to 16 residues, with at most five intraloop residues) were performed to elucidate some factors controlling their electron capture. These illustrative systems display contrasted behaviors, shedding light on several criteria of differentiation: size, shape, and rigidity of the disulfide-linking loop, intramolecular hydrogen bonds, etc. The geometrical malleability of disulfide radical anions, whose existence and role as intermediate have been evidenced, is discussed. The disulfide elongation (by ca. 0.7 A) upon electron capture induces "soft" structural damages for these turn structures, with a weakening or cleavage of vicinal hydrogen bond(s). On the basis of a series of six Cys-Alan-Cys peptides, it is proposed that electron affinity reflects the topological frustration of these short and highly constrained structures. Results for a series of amino acid mutations are analyzed for the Cys-Xxx-Yyy-Cys motif, common to redox enzymes of the thioredoxin superfamily.     

Optimization of a liquid chromatographic separation for the simultaneous determination of four anthracyclines and their respective 13-S-dihydro metabolites

The optimization of a liquid chromatographic separation of four anthracyclines (doxorubicin, epirubicin, daunorubicin and idarubicin) and their respective 13-S-dihydro metabolites (doxorubicinol, epirubicinol, daunorubicinol and idarubicinol) is described. Inclusion of epidaunorubicin in the assay allows internal standardization. Potential chromatographic interference of aglycones (doxorubicinone, daunorubicinone, idarubicinone, doxorubicinolone, daunorubicinolone and idarubicinolone) was investigated and tackled. The analyses were performed on a C18 RP column and gradient elutions were performed with a mixture of 0.1% formic acid in water and 0.1% formic acid in ACN. The analytes were measured by fluorescence detection with an excitation wavelength of 480 nm and emission wavelength of 555 nm, respectively. The separation will potentially allow a broad field of applications, ranging from therapeutic drug monitoring and kinetic studies in cancer patients to monitoring hospital personnel and effluents.