Molecular recognition of avidin on biotin-functionalized gold surfaces detected by FT-IRRAS and use of metal carbonyl probes

Fourier transform infrared reflection-absorption spectroscopy (FT-IRRAS) was successively used to monitor the covalent immobilization of biotin molecules onto a planar gold substrate covered with a self-assembled monolayer of cystamine and to transduce the molecular recognition of avidin and biotin. This detection was greatly facilitated and made selective by the labeling of avidin and of biotin with various transition metal carbonyl probes. The binding of avidin to the surface was optimized by blocking the nonspecific binding sites by adsorption of an unrelated protein, bovine serum albumin. This work exemplifies the feasibility of detecting biomolecular associations involving molecules of any size at a liquid/solid interface by using a simple and accessible surface analysis technique.     

Heterocyclisation of Unsaturated Phenylsulfides. Synthesis of a Novel Series of 2 Substituted-2,3-dihydrobenzothiazoles

Aminoarylhydroxy thioalkenes react with tosyl derivatives to provide mainly N substituted -2 vinyl -2,3 dihydrobenzothiazoles. A different regiochemistry of cyclization depending on whether a methyl or a phenyl susbtituent was used, was observed Formation of -2H-3,4-dihydrobenzothiazines and dienes was observed.     

Representations for conditional expectations and applications to pricing and hedging of financial products in Lévy and jump-diffusion setting

In this article, we derive expressions for conditional expectations in terms of regular expectations without conditioning but involving some weights. For this purpose, we apply two approaches: the conditional density method and the Malliavin method. We use these expressions for the numerical estimation of the price of American options and their deltas in a Lévy and jump-diffusion setting. Several examples of applications to financial and energy markets are given including numerical examples.     

A Bis-Chelating / Ligand for the Synthesis of Heterobimetallic Platinum(II)/Rhenium(I) Complexes: Tools for the Optimization of a New Class of Platinum(II) Anticancer Agents

The two independent and coordination sites of a newly synthesized bis[2-(hydroxyphenyl)-1,2,4-triazole] platform have been exploited to prepare four monometallic neutral ()Pt^II complexes carrying DMSO, pyridine, triphenylphosphine, or N-heterocyclic carbene as the fourth ligand. Then, the second coordination site was used to introduce an IR-active rhenium tricarbonyl entity, affording the four corresponding heterobimetallic neutral Pt^II/Re^I complexes, as well as a cationic Pt^II/Re^I derivative. X-ray crystallographic studies showed that distortion of the organic platform occurred to accommodate the coordination geometry of both metal centers. No ligand exchange or transchelation occurred upon incubation of the Pt^II complexes in aqueous environment or in the presence of Fe^III, respectively. The antiproliferative activity of the ligand and complexes was first screened on the triple-negative breast cancer cell line MDA-MB-231. Then, the IC₅₀ values of the most active candidates were determined on a wider panel of human cancer cells (MDA-MB-231, MCF-7, and A2780), as well as on a nontumorigenic cell line (MCF-10A). Low micromolar activities were reached for the complexes carrying a DMSO ligand, making them the first examples of highly active, but hydrolytically stable, Pt^II complexes. Finally, the characteristic mid-IR signature of the {Re(CO)₃} fragment in the Pt/Re heterobimetallic complexes was used to quantify their uptake in breast cancer cells.     

ETUDE STRUCTURALE DE QUELQUES SPIROPHOSPHORANES A LIAISON P–C EXOCYCLIQUE

Abstract

The PMR spectra of some spirophosphorans containing the P–C bond are analysed. The results allow us to determine the stereochemistry of these compounds (conformation, stereoisomerism).

Le spectre de RMP de quelques spirophosphoranes à liaison P–C est analysé. Les résultats sont utilisés pour préciser la stéréochimie de ces composés (conformation, stéréoisomérie).     

Decisive Influence of Phosphorus Ligands on O2 Oxidations of Alkenes in the Presence of the Iron Nitrato/Iron Nitrosyl Couple

Abstract

Fe(NO)₂XL and Fe(NO)X₂L nitrosyl iron complexes, X = Cl, I, and L = HMPA, dppe, PPh₃, activate molecular O₂ to yield nitrato complexes. The phosphorous ligand is decisive for the oxidative power of these nitrates: with HMPA or dppe, oxygen transfer occurs only to phosphines. On going from HMPA to PPh3 the single nitrato complex obtained, Fe(NO)₂X(OPPh₃)₂ selectively epoxidizes cyclohexene, and this is the first example of oxygen transfer from a nitrato ligand to an olefin.     

Multiple Mechanism of NCA Polymerization: Effect of N-Acetylglycine NCA and Related Additives

Polymerization of α-aminoisobutyric acid NCA by alkaline salts of various basicity as well as amines has been investigated. The study was focused on the effect on the initial polymerization rate of additives such as N-acetylglycine NCA and some other less electrophilic additives (l-acetyl-2-pyrrolidone, 3-acetyl-2-oxazolidone, 1-acetyl-3-methylhydantoin) which are all models of the growing chain end produced by the NCA anion pathway. The acetyl endgroup was detected by 250 MHz ¹H-NMR in all the polymers of α-aminoisobutyric acid NCA obtained in the presence of l-acetyl-3-methylhydantoin and triethyl amine or sodium methoxide initiators, whereas the additives influenced variously the kinetics of polymerization according to the nature of the initiator used. The results were interpreted in the light of a multiple mechanism supposing the simultaneous presence of the initiator anion, its conjugate acid, and NCA anion for basic salt initiation. Thus, the observed effect has to be considered as the sum of an elementary acceleration due to NCA anion and of an elementary deceleration due to the initiator anion. Predominance of the pathways involving NCA anion could be shown this way. This conclusion could be extended to γ-benxyl-L-glutamate NCA which is a more reactive NCA. However, the deceleration observed with some additives led us to believe that a nonnegligible participation of initiator anion during initiation cannot be excluded.