Catalytic Amine Oxidation under Ambient Aerobic Conditions: Mimicry of Monoamine Oxidase B

The flavoenzyme monoamine oxidase (MAO) regulates mammalian behavioral patterns by modulating neurotransmitters such as adrenaline and serotonin. The mechanistic basis which underpins this enzyme is far from agreed upon. Reported herein is that the combination of a synthetic flavin and alloxan generates a catalyst system which facilitates biomimetic amine oxidation. Mechanistic and electron paramagnetic (EPR) spectroscopic data supports the conclusion that the reaction proceeds through a radical manifold. This data provides the first example of a biorelevant synthetic model for monoamine oxidase B activity.     

Development of poly(ε-caprolactone-co-l-lactide) and poly(ε-caprolactone-co-δ-valerolactone) as new degradable binder used for antifouling paint

Copolyesters containing ε-caprolactone and l-lactide or ε-caprolactone and δ-valerolactone at different compositions were synthesized by using tetrabutoxytitane Ti(OBu)₄ at high temperature in bulk. A series of copolyesters were prepared by varying the compositions of both comonomers. These copolymers were characterized by using ¹H NMR, ¹³C NMR, gel permeation chromatography (GPC), differential scanning calorimetry (DSC) and MALDI-TOF mass spectrometry. ¹³C NMR analysis gave an insight on their microstructure. Structural parameters of the copolymers were obtained by calculating the triad sequence fractions. Poly(ε-caprolactone-co-l-lactide) has a more alternate structure than poly(ε-caprolactone-co-δ-valerolactone). The potential use of these copolyesters in antifouling coatings was examined because of their solubility in aromatic solvent and their hydration and hydrolytic degradation. Paints based on these new degradable binders had a good antifouling activity in Atlantic Ocean (France).     

Grafting of poly(methyl vinyl ketone) onto aluminum surface

Polymers were grafted on aluminum surfaces in order to modify the chemical and physical properties of the interface. The properly cleaned and activated surface of the aluminum substrate was first "silanized" either with 3-(trimethoxysilyl)propylamine or allyltrimethoxysilane. The grafting was carried out following two methods: (i) by the reaction of preformed poly(methyl vinyl ketone) with the aminosilane-modified surface; and (ii) by polymerization of methyl vinyl ketone with the vinylsilane-modified surface. The modified aluminum surfaces were characterized by X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscopy, and energy dispersive X-ray spectroscopy. The new surfaces were examined by contact-angle measurements, and determinations of the Lewis basicity.     

Circularly Polarized Fluorescent Helicene-Boranils: Synthesis,Photophysical and Chiroptical Properties

Mono- and di-boranil-substituted helicenes were prepared by BF₂-borylation of the corresponding anils, readily synthesized by condensation of 2-amino- and 2,15-diamino-helicenes with 4-(diethylamino)salicylaldehyde. After enantiomeric resolution using HPLC, their chiroptical properties including circularly polarized fluorescence in solution and in PMMA films were investigated and rationalized with the help of NMR, X-ray and quantum-chemical calculations.     

Synthesis,Profiling, and Bioactive Conformation of trans‐Cyclopropyl Epothilones

A series of new 3‐deoxy‐C(12),C(13)‐trans‐cyclopropyl‐epothilones have been prepared, bearing benzothiazole, quinoline, thiazol‐5‐ylvinyl, or isoxazol‐3‐ylvinyl side chains. For analogs with fused aromatic side chains, macrocyclic ring‐closure was based on ring‐closing olefin metathesis (RCM) of a precursor incorporating the fully elaborated heavy atom framework of the target structure (including the side chain moiety), while side chain attachment for the thiazole and isoxazole‐containing 16‐desmethyl analogs was performed only after establishment of the macrolactone core. Two approaches were elaborated for a macrocyclic aldehyde as the common precursor for the latter analogs that involved ring‐closure either by RCM or by macrolactonization. Benzothiazole‐ and quinoline‐based analogs were found to be highly potent antiproliferative agents; the two analogs with a thiazol‐5‐ylvinyl or an isoxazol‐3‐ylvinyl side chain likewise showed good antiproliferative activity but were significantly less potent than the parent epothilone A. Surprisingly, the desaturation of the C(10)?C(11) bond in these analogs was associated with a virtually complete loss in antiproliferative activity, which likely reflects a requirement for a ca. 60 ° C(10)?C(11) torsion angle in the tubulin‐bound conformation of 12,13‐trans‐epothilones.     

Twin-transformed lattice defects in γ-TiAl

We study the transformation of lattice defects in γ-TiAl upon intersection by deformation twins. A faulted dipole is chopped forming a dislocation loop faulted on the cube plane of the twin; faulted dipoles and twin loops may shrink at different rates. Dislocations with 1/2<110] and <011] Burgers vectors gliding on octahedral planes are transformed into configurations with low mobility on {010} plane. Elementary mechanisms involved in the transformation are considered and a pole mechanism for twin growth at forest dislocations is proposed.     

An innovative antisolvent precipitation process as a promising technique to prepare ultrafine rifampicin particles

Many existing and new drugs fail to be fully utilized because of their limited bioavailability due to poor solubility in aqueous media (BCS drug classes II and IV). In this work, for accelerating dissolution of this kind of poorly water-soluble drugs, an antisolvent precipitation method that does not require the use of conventional volatile organic solvents is proposed. To demonstrate this technique, ultrafine particles of rifampicin were prepared using a room temperature ionic liquid (1-ethyl 3- methyl imidazolium methyl-phosphonate) as an alternative solvent and a phosphate buffer as an antisolvent.Rifampicin solubility was measured in various solvents (1-ethyl 3-methyl imidazolium methylphosphonate, water and phosphate buffer), showing the RTIL good solvency for the model drug: rifampicin solubility was found to be higher than 90 mg/g in RTIL at 30 °C and lower than 1 mg/g in water at 25 °C. Additionally, it was demonstrated that introduction of rifampicin solution in 1-ethyl 3- methyl imidazolium methyl-phosphonate into the aqueous solution antisolvent can produce particles in the submicron range with or without hydroxypropyl methylcellulose as the stabilizer. The ultrafine particles (280–360 nm) are amorphous with enhanced solubility and faster dissolution rate. To our knowledge, this is the first published work examining the suitability of using RTILs for ultrafine drug nanoparticles preparation by an antisolvent precipitation process.     

Microdroplets in Microfluidics: An Evolving Platform for Discoveries in Chemistry and Biology

Microdroplets in microfluidics offer a great number of opportunities in chemical and biological research. They provide a compartment in which species or reactions can be isolated, they are monodisperse and therefore suitable for quantitative studies, they offer the possibility to work with extremely small volumes, single cells, or single molecules, and are suitable for high‐throughput experiments. The aim of this Review is to show the importance of these features in enabling new experiments in biology and chemistry. The recent advances in device fabrication are highlighted as are the remaining technological challenges. Examples are presented to show how compartmentalization, monodispersity, single‐molecule sensitivity, and high throughput have been exploited in experiments that would have been extremely difficult outside the microfluidics platform.     

Improved Accuracy of Low Affinity Protein–Ligand Equilibrium Dissociation Constants Directly Determined by Electrospray Ionization Mass Spectrometry

There is continued interest in the determination by ESI-MS of equilibrium dissociation constants (K_D) that accurately reflect the affinity of a protein–ligand complex in solution. Issues in the measurement of K_D are compounded in the case of low affinity complexes. Here we present a K_D measurement method and corresponding mathematical model dealing with both gas-phase dissociation (GPD) and aggregation. To this end, a rational mathematical correction of GPD (f_sat) is combined with the development of an experimental protocol to deal with gas-phase aggregation. A guide to apply the method to noncovalent protein–ligand systems according to their kinetic behavior is provided. The approach is validated by comparing the K_D values determined by this method with in-solution K_D literature values. The influence of the type of molecular interactions and instrumental setup on f_sat is examined as a first step towards a fine dissection of factors affecting GPD. The method can be reliably applied to a wide array of low affinity systems without the need for a reference ligand or protein.     

Simplifying native chemical ligation with an N-acylsulfonamide linker

We report a simplified procedure for the chemical ligation of peptides by using the sulfamylbutyryl linker as a mildly activating group capable of participating in ligation. When the peptidyl N-methylsulfonamide is directly added with excess thiols to ligation reactions, the speed of reaction is comparable to native chemical ligation.