Aggregation behaviors of gemini nucleotide at the air-water interface and in solutions induced by adenine-uracil interaction

Cationic gemini surfactants having nucleotides as counterions (called nucleo-gemini hereafter) were synthesized and their aggregation behavior at air-water surfaces as well as in bulk solutions were studied. Fluid solutions of these nucleo-gemini surfactants show transitions to hydrogels upon addition of complementary nucleoside bases or other nucleo-gemini surfactants having complementary bases as counterions. The FTIR-ATR measurements show that the carboxylate groups of uridine form hydrogen bonds with the amine groups of adenosine. The aggregation behavior was also confirmed at the air-water interface by Brewster angle microscopy as well as surface pressure measurements; the monolayer of a gemini nucleotide was observed to undergo a transition to multilayers when nucleosides with complementary bases were added into the subphase. Isotherm curves of surface pressure monitored in parallel show a decrease in molecular area upon addition of such nucleosides.     

Porous materials show superhydrophobic to superhydrophilic switching

Switching between superhydrophobicity and superhydrophilicity in porous materials was predicted theoretically and demonstrated experimentally with the example of thermally induced contact angle change; tunability of this system was also demonstrated.     

Latex bead immobilisation in PDMS matrix for the detection of p53 gene point mutation and anti-HIV-1 capsid protein antibodies

Two diagnostic chemiluminescent biochips were developed for either the detection of p53 gene point mutation or the serological detection of anti-HIV-1 p24 capsid protein. Both biochips were composed of 24 microarrays of latex beads spots (4×4) (150 m in diameter, 800 m spacing) entrapped in a poly(dimethylsiloxane) elastomer (PDMS). The latex beads, bearing oligonucleotide sequences or capsid protein, were spotted with a conventional piezoelectric spotter and subsequently transferred at the PDMS interface. The electron microscopy observation of the biochips showed how homogeneous and well distributed the spots could be. Point mutation detection on the codon 273 of the p53 gene was performed on the basis of the melting temperature difference between the perfect match sequence and the one base pair mismatch sequence. The hybridisation of a 20-mer oligonucleotide form the codon 273 including a one base pair mutation in its sequence on a biochip arrayed with non-muted and the muted complementary sequences, enabled a clear discrimination at 56°C between muted and wild sequences. Moreover, the quantitative measurement of the amount of muted sequence in a sample was possible in the range 0.4–4 pmol. Serological measurement of anti-HIV-1 p24 capsid protein on the biochip, prepared with 1-m-diameter latex beads, enabled the detection of monoclonal antibodies in the range 1.55–775 ng mL^–1. Such a range could be lowered to 0.775 ng mL^–1 when using 50-nm-diameter beads, which generated a higher specific surface. The validation of the biochip for the detection of anti-HIV-1 capsid protein antibodies was performed in human sera from seropositive and seronegative patients. The positivity of the sera was easily discriminated at serum dilutions below 1:1,000.     

Segmentation under geometrical conditions using geodesic active contours and interpolation using level set methods

Let I: be a given bounded image function, where is an open and bounded domain which belongs to ⁿ. Let us consider n=2 for the purpose of illustration. Also, let S={x_i}_i be a finite set of given points. We would like to find a contour , such that is an object boundary interpolating the points from S. We combine the ideas of the geodesic active contour (cf. Caselles et al. [7,8]) and of interpolation of points (cf. Zhao et al. [40]) in a level set approach developed by Osher and Sethian [33]. We present modelling of the proposed method, both theoretical results (viscosity solution) and numerical results are given. AMS subject classification 49L25, 74G65, 68U10     

Tetranuclear polybipyridyl complexes of Ru(II) and Mn(II), their electro- and photo-induced transformation into di-mu-oxo Mn(III)Mn(IV) hexanuclear complexes

Three heterotetranuclear complexes, [{Ru(II)(bpy)(2)(L(n))}(3)Mn(II)](8+) (bpy = 2,2'-bipyridine, n = 2, 4, 6), in which a Mn(II)-tris-bipyridine-like centre is covalently linked to three Ru(II)-tris-bipyridine-like moieties using bridging bis-bipyridine L(n) ligands, have been synthesised and characterised. The electrochemical, photophysical and photochemical properties of these complexes have been investigated in CH(3)CN. The cyclic voltammograms of the three complexes exhibit two successive very close one-electron metal-centred oxidation processes in the positive potential region. The first, which is irreversible, corresponds to the Mn(II)/Mn(III) redox system (E(pa) approximately 0.82 V vs Ag/Ag(+) 0.01 M in CH(3)CN-0.1 M Bu(4)NClO(4)), whereas the second which is, reversible, is associated with the Ru(II)/Ru(III) redox couple (E(1/2) approximately 0.91 V). In the negative potential region, three successive reversible four electron systems are observed, corresponding to ligand-based reduction processes. The three stable dimeric oxidized forms of the complexes, [Mn(2)(III,IV)O(2){Ru(II)(bpy)(2)(L(n))}(4)](11+), [Mn(2)(IV,IV)O(2){Ru(II)(bpy)(2)(L(n))}(4)](12+) and [Mn(2)(IV,IV)O(2){Ru(III)(bpy)(2)(L(n))}(4)](16+) are obtained in fairly good yields by sequential electrolyses after consumption of respectively 1.5, 0.5 and 3 electrons per molecule of initial tetranuclear complexes. The formation of the di-micro-oxo binuclear complexes are the result of the instability of the {[Ru(II)(bpy)(2)(L(n))](3)Mn(III)}(9+) species, which react with residual water, via a disproportionation reaction and the release of one ligand, [Ru(II)(bpy)(2)(L(n))](2+). A quantitative yield can be obtained for these reactions if the electrochemical oxidations are performed in the presence of an added external base like 2,6-dimethylpyridine. Photophysical properties of these compounds have been investigated showing that the luminescence of the Ru(II)-tris-bipyridine-like moieties is little affected by the presence of manganese within the tetranuclear complexes. A slight quenching of the excited states of the ruthenium moieties, which occurs by an intramolecular process, has been observed. Measurements made at low concentration (<1 x 10(-5) M) indicate that some decoordination of Mn(2+) arises in 1a-c. These measurements allow the calculation of the association constants for these complexes. Finally, photoinduced oxidation of the tetranuclear complexes has been performed by continuous photolysis experiments in the presence of a large excess of a diazonium salt, acting as a sacrificial oxidant. The three successive oxidation processes, Mn(II)--> Mn(III)Mn(IV), Mn(III)Mn(IV)--> Mn(IV)Mn(IV) and Ru(II)--> Ru(III) are thus obtained, the addition of 2,6-dimethylpyridine in the medium giving an essentially quantitative yield for the two first photo-induced oxidation steps as found for electrochemical oxidation.     

A new stepwise synthesis of a family of propylamines derived from diatom silaffins and their activity in silicification

A new method for the stepwise synthesis of propylamines containing fragments of N-methyl propylamine as found in diatom bioextracts is presented and their activity in silicic acid condensation is described.     

Potential applications of high pressures in pharmaceutical science and medicine

Abstract

High pressure (HP) technology appears to be of paramount interest for valuable applications in pharmacy and medicine, owing to academic studies and industrial developments of this technology for food processing. The main potential application of HP between 100 MPa and 1200 MPa (1 kbar to 12kbar) is the inactivation of biological agents (bacteria, moulds, yeasts, virus and even prions) which allows the sterilization (i.e, “pascalization”) of thermo-, chemo-, or radio-sensitive materials and chemicals. The immunogenicity of some pressure-killed bacteria or virus suggests also the potentiality of making new vaccines. Another interest of the HP technology is the possibility of storage at subzero temperatures without freezing of cells and animal tissues to be used for cells and organs for transplant. HP engineering may be used for enzyme-catalyzed synthesis of fine chemicals, production of modified proteins of medical or pharmaceutical interest, and organic synthesis of pharmaceuticals.     

Well-posedness of a degenernate parabolic equation issuing from two-dimensional perfect fluid dynamics

A degenerate parabolic equation of convection-diffusion type has been proposed by Robert and Sommeria in [12] to describe the relaxation towards statistical equilibrium states in 2D incompressible perfect fluid dynamics. The paper is concerned with the Cauchy problem for this equation. The local existence of a variational soluation is obtained in using the decrease of the (negative) mixing entropy and Schauder theorem. A smoothing effect is used when proving the uniqueness of the variational solutions by youdovitch's method. Finally, global existence of solutions and their asymptotic convergence towards Gibbs states are shown for a large class of initial data.     

Variety of available coordination sites for extra-framework iron in LTA and MFI zeolites

Variations in coordination states of extra-framework iron are studied in low iron content ferrisilicates (Si/⁵⁷Fe ≈ 200) during various in situ treatments. In Fe-LTA complete Fe³⁺ ? Fe^2?+? reversibility is observed. In Fe-MFI extra-framework iron can be stabilized in Fe^2?+? state in spite of ambient oxidizing conditions (N₂O, 620 K). Further, in Fe-MFI simultaneous stabilization of Fe^2?+? and Fe^3?+? may take place providing centres for redox catalytic processes.