Synchronization and functional central limit theorems for interacting reinforced random walks

We obtain Central Limit Theorems in Functional form for a class of time-inhomogeneous interacting random walks. Due to a reinforcement mechanism and interaction, the walks are strongly correlated and converge almost surely to the same, possibly random, limit. We study random walks interacting through a mean-field rule and compare the rate they converge to their limit with the rate of synchronization, i.e. the rate at which their mutual distances converge to zero. We show that, under certain conditions, synchronization is faster than convergence. Even if our focus is on theoretical results, we propose as main motivations two contexts in which such results could directly apply: urn models and opinion dynamics in a random network evolving via preferential attachment.     

Resorcylic acid lactones: A pluripotent scaffold with therapeutic potential

The recent discoveries of potent HSP90 and MAP kinase inhibitors amongst the resorcylic acid lactones (RALs) have revived interest in this family of natural products. Both HSP90 and MAP kinase inhibition hold tremendous therapeutic potential, particularly in the treatment of cancer. Our synthetic efforts towards the RALs and, in particular, selective inhibitors of HSP90 and kinases are reviewed.     

A novel heterotrifunctional peptide-based cross-linking reagent for facile access to bioconjugates. Applications to peptide fluorescent labelling and immobilisation

A convenient, versatile and straightforward synthesis of a novel heterotrifunctional peptide-based linker molecule is described. This generic bio-labelling reagent contains an amine-reactive N-hydroxysuccinimidyl carbamate moiety, an aldehyde/ketone-reactive aminooxy group and a thiol group with a propensity to form urea, oxime and thioether linkages respectively. The full chemical orthogonality between the free aminooxy and thiol functionalities was demonstrated through the preparation of a fluorescent reagent suitable for the selective staining of a carboxaldehyde-modified surface by means of oxime ligation. The absence of reactivity of these two functions toward the nucleophile-sensitive active carbamate was obtained by using temporary aminooxy- and thiol-protecting groups removable under mild conditions. The utility of the linker molecule to cross-link three different molecular partners has been illustrated by the preparation of fluorescent tripod-functionalised surfaces which may be useful in developing new peptide microarrays and related immunosensors.     

7-hydroxycoumarin-hemicyanine hybrids: a new class of far-red emitting fluorogenic dyes

The design and synthesis of novel water-soluble far-red emitting phenol-based fluorophores derived from 7-hydroxycoumarin are described. These hemicyanine-coumarin hybrids display promising spectroscopic features such as large apparent Stokes shift (ranging from 60 to 140 nm) and fluorescence emission maxima between 620 and 720 nm in physiological conditions. Their utility was then illustrated by the preparation of an original fluorogenic probe of penicillin G acylase (PGA) whose fluorescence is unveiled through an enzyme-initiated domino reaction.     

Some micromechanical aspects of failure in granular materials based on second-order work

This paper discusses the notion of failure in a granular assembly by examining the key microstructural mechanisms which are most likely to trigger the nucleation and propagation of instabilities within a granular material. For this purpose, the key variable to predict the occurrence of failure, known as second-order work, is expressed from variables on the grain scale. The local behaviour incidents (where contacts may open or slide), compared to the global response of the assembly, are analysed by two approaches. First, numerical computations made by a discrete element model confirm the microscopic definition of the second-order work. Secondly, a micromechanical model, based on a homogenization procedure, relating the macroscopic behaviour to microscopic ingredients, namely contact planes, points to a close link between the occurrence of failure on the macroscopic scale as well as on the contact planes.     

The first metal-free water-soluble cryptophane-111

Cryptophane-111 is one of the best candidates for (129)Xe MRI-based applications. Herein, we report the first metal-free and water-soluble cryptophane-111 core which involves an efficient and unusual post-synthetic sulfonation procedure.     

Optimizing millisecond time scale near-infrared emission in polynuclear chrome(III)-lanthanide(III) complexes

This work illustrates a simple approach for optimizing long-lived near-infrared lanthanide-centered luminescence using trivalent chromium chromophores as sensitizers. Reactions of the segmental ligand L2 with stoichiometric amounts of M(CF(3)SO(3))(2) (M = Cr, Zn) and Ln(CF(3)SO(3))(3) (Ln = Nd, Er, Yb) under aerobic conditions quantitatively yield the D(3)-symmetrical trinuclear [MLnM(L2)(3)](CF(3)SO(3))(n) complexes (M = Zn, n = 7; M = Cr, n = 9), in which the central lanthanide activator is sandwiched between the two transition metal cations. Visible or NIR irradiation of the peripheral Cr(III) chromophores in [CrLnCr(L2)(3)](9+) induces rate-limiting intramolecular intermetallic Cr→Ln energy transfer processes (Ln = Nd, Er, Yb), which eventually produces lanthanide-centered near-infrared (NIR) or IR emission with apparent lifetimes within the millisecond range. As compared to the parent dinuclear complexes [CrLn(L1)(3)](6+), the connection of a second strong-field [CrN(6)] sensitizer in [CrLnCr(L2)(3)](9+) significantly enhances the emission intensity without perturbing the kinetic regime. This work opens novel exciting photophysical perspectives via the buildup of non-negligible population densities for the long-lived doubly excited state [Cr*LnCr*(L2)(3)](9+) under reasonable pumping powers.     

TRIPLET STATES OF CAROTENOIDS BOUND TO REACTION CENTERS OF PHOTOSYNTHETIC BACTERIA: TIME-RESOLVED RESONANCE RAMAN SPECTROSCOPY

Time-resolved, low-temperature resonance Raman spectra of triplet states of the carotenoids specifically present in bacterial reaction centers in a strained cis conformation have been obtained, thus demonstrating the possibility of studying intermediate transient states of these structures using resonance Raman spectroscopy. Resonance Raman spectra of triplet cis spheroidene and cis methoxyneurosporene present in reaction centers of Rhodopseudomonas spheroides, (strains 2.4.1. and Ga, respectively) exhibit marked differences with those of triplet, all- trans carotenoids previously studied in vitro. These differences, together with the frequency shifts measured for the v ₁ modes, indicate that triplet carotenoids bound to reaction centers retain a cis conformation, and that probably no isomerization occurs to all- trans carotenoids upon T ← S₀ excitation. P_i electron distributions along the polyene backbone are probably less regular in the triplet state than in the singlet ground state, although probably not to the extent suggested by previous theoretical calculations. The apparently anomalous behaviour of the v ₂ bands of all- trans carotenoids upon T ← S₀ excitation is shown to result largely from the actual complexity of this region of the Raman spectra, together with a weak participation of the v _c—–c internal coordinate in the corresponding modes. Finally, the Raman scattering efficiency of triplet spheroidene bound to reaction centers is lower than that of the singlet, ground state form, under equivalent excitation conditions.