Experimental and theoretical study of QED corrections in the ground state of heliumlike iron

The energy of the Lyβ and Lyγ lines of heliumlike iron has been measured with a precision of 25 ppm. The study of these transitions involving levels of high principal quantum number (n=3 andn=4) provides us with informations on the ground state 1¹ S ₀ of the ion. The experimental values are compared to MCDF calculations including QED two-body corrections.     

Efficient synthesis of (S)-4-phthalimido-1,3,4,5-tetrahydro-8-(2,6-dichlorobenzyloxy)- 3-oxo-2H-2-benzazepin-2-acetic acid (PHt-Hba(2,6-Cl2-Bn)-Gly-OH)

4-Amino-2-benzazepin-3-ones have proven very useful for studying the biologically active conformations of peptides. The synthesis of Pht-Aba-Xaa-OH by reaction of the corresponding 1,3-oxazolidin-5-one with trifluoromethanesulfonic acid (TFMSA) has been reported in the literature. However, when this procedure was applied to the preparation of Pht-Hba(Bn)-Gly-OH 8, many byproducts were formed and the yield of the desired aminobenzazepinones 7 and 8 was very low. We report in this paper an efficient methodology for the synthesis of Pht-Hba(2,6-Cl2-Bn)-Gly-OH 17 starting from the commercially available tyrosine. In our procedure, the dipeptide Pht-Tyr(2,6-Cl2-Bn)-Gly-OH 15 is converted to the 1,3-oxazolidin-5-one 16 which then undergoes Friedel-Crafts cyclization in the presence of tin tetrachloride to afford the desired 4-phthalimido-1,3,4,5-tetrahydro-8-(2,6-dichlorobenzyloxy)-2-be nzazepin-3-one 17 in excellent yield.     

Self-assembled monolayers of peptide nucleic acids on gold surfaces: a spectroscopic study

We have characterized self-assembled monolayers (SAMs) of thiol-derivatized peptide nucleic acid (PNA) chains adsorbed on gold surfaces by using reflection absorption infrared spectroscopy (RAIRS) and X-ray photoemission spectroscopy (XPS) techniques. We have found that the molecular orientation of PNAs strongly depends on surface coverage. At low coverage, PNA chains lie flat on the surface, while at high coverage, PNA molecules realign their molecular axes with the surface normal and form SAMs without the need of co-immobilization of spacers or other adjuvant molecules. The change in the molecular orientation has been studied by infrared spectroscopy and it has been confirmed by atomic force microscopy (AFM). PNA immobilization has been followed by analyzing the N(1s) XPS core-level peak. We show that the fine line shape of the N(1s) core-level peak at optimal concentration for biosensing is due to a chemical shift. A combination of the above-mentioned techniques allow us to affirm that the structure of the SAMs is stabilized by molecule-molecule interactions through noncomplementary adjacent nucleic bases.     

BSDEs with stochastic Lipschitz condition and quadratic PDEs in Hilbert spaces

This paper is devoted to real valued backward stochastic differential equations (BSDEs for short) with generators which satisfy a stochastic Lipschitz condition involving BMO martingales. This framework arises naturally when looking at the BSDE satisfied by the gradient of the solution to a BSDE with quadratic growth in Z$Z$. We first prove an existence and uniqueness result from which we deduce the differentiability with respect to parameters of solutions to quadratic BSDEs. Finally, we apply these results to prove the existence and uniqueness of a mild solution to a parabolic partial differential equation in Hilbert space with nonlinearity having quadratic growth in the gradient of the solution.     

{7-[Bis(carboxymethyl)amino]coumarin-4-yl}methoxycarbonyl derivatives for photorelease of carboxylic acids, alcohols/phenols, thioalcohols/thiophenols, and amines

Light-induced release of biomolecules from inactive precursor molecules represents a powerful method to study cellular processes with high temporal and spatial resolution. Here we report the synthesis and photochemistry of a series of {7-[bis(carboxymethyl)amino]coumarin-4-yl}methyl carboxylates, carbonates, carbamates, and thiocarbonates as potential phototriggers for compounds with COOH, OH, NH(2), and SH functions. The compounds are soluble in aqueous buffer, show low fluorescence, and are efficiently photolysed by irradiation with UV/Vis or IR light to release carboxylates, alcohols, phenols, amines, thioalcohols, or thiophenols.     

Activation of a Sweet Taste Receptor by Oleanane-Type Glycosides from Wisteria sinensis

The phytochemical study of Wisteria sinensis (Sims) DC. (Fabaceae), commonly known as the Chinese Wisteria, led to the isolation of seven oleanane-type glycosides from an aqueous-ethanolic extract of the roots. Among the seven isolated saponins, two have never been reported before: 3-O-α-L-rhamnopyranosyl-(1→2)-β-D-glucopyranosyl-(1→2)-β-D-glucuronopyranosyl-22-O-acetylolean-12-ene-3β,16β,22β,30-tetrol, and 3-O-β-D-xylopyranosyl-(1→2)-β-D-glucuronopyranosylwistariasapogenol A. Based on the close structures between the saponins from W. sinensis, and the glycyrrhizin from licorice, the stimulation of the sweet taste receptor TAS1R2/TAS1R3 by these glycosides was evaluated.