Search results for "Molecule"

Effect of air-absorbed oxygen and moisture on the chemical stability of photoexcitedMg,ZnandEuphthalocyanines in dimethylformamide

2006

Absorption of oxygen and moisture from air by MPc-DMF systems was studied and related to the molecular stability demonstrated by phthalocyanine complexes (unsubstituted MPc's : MgPc , ZnPc and EuPc2; Pc = phthalocyanine ligand, C32H16N8) subjected to UV irradiation. A lower stability of air-exposed dimethylformamide solutions is observed and is due to a specific affinity for molecular oxygen revealed by the Pc macrocycle. SEM results proved oxygen molecules fixed to the phthalocyanine solids by forces strong enough to sustain desorption under vacuum. Absorption curves determined for MPc-DMF systems also indicate oxygen accommodated by the phthalocyanine moiety. This explains the predominant…

Aligned microcontact printing of biomolecules on microelectronic device surfaces

2001

Microcontact printing (/spl mu/CP) of extracellular matrix proteins is a fascinating approach to control cell positioning and outgrowth, which is essential in the development of applications ranging from cellular biosensors to tissue engineering. Microelectronic devices can be used to detect the activity from a large number of recording sites over the long term. However, signals from cells can only be recorded at small sensitive spots. Here, the authors present an innovative setup to perform aligned /spl mu/CP of extracellular matrix proteins on microelectronic devices in order to guide the growth of electrogenic cells specifically to these sensitive spots. The authors' system is based on t…

Synthesis and characterization of perfluoroalkyl-pyrenes embedded in a polymethylmethacrylate matrix

2012

Structural behaviour differences in low methoxy pectin solutions in the presence of divalent cations (Ca 2+ and Zn 2+ ): a process driven by the bind…

2014

International audience; In this paper, we compare the interactions between low methoxy pectin (LMP) and either Ca2+ or Zn2+ in semi-dilute solutions. Intrinsic viscosity and turbidity measurements reveal that pectin-calcium solutions are more viscous, but yet less turbid, than pectin-zinc ones. To get a molecular understanding on the origin of this rather unexpected behavior, we further performed isothermal titration calorimetry, small angle neutron scattering experiments, as well as molecular dynamics simulations. Our results suggest that calcium cations induce the formation of a more homogeneous network of pectin than zinc cations do. The molecular dynamics simulations indicate that this …

Orientation and molecular contacts of melatonin confined into AOT and lecithin reversed micellar systems

2008

Abstract The state of increasing amounts of melatonin (MLT) confined in dry AOT or lecithin reversed micelles dispersed in CCl 4 has been investigated by UV–vis and 1 H NMR spectroscopies. The experimental results are consistent with MLT totally entrapped in reversed micelles, as a consequence of specific melatonin/surfactant interaction; the main driving force of the MLT solubilization in the core of reversed micelles is the establishment of H-bonding between the MLT NH groups (both indolic and amidic) and the head group of surfactants. The short contacts deduced from intermolecular NOEs are accounted for by favourable interactions between the surfactant's polar head and the H7–NH–H2 fragm…

Triggering a transient organo-gelation system in a chemically active solvent

2021

A transient organo-gelation system with spatiotemporal dynamic properties is described. Here, the solvent actively controls a complex set of equilibria that underpin the dynamic assembly event. The observed metastability is due to the in situ formation of a secondary solvent, acting as an antagonist against the primary solvent of the organogel. peerReviewed

The adsorption of water vapor on super absorbent product at low temperatures and low mass.

2006

The adsorption isotherms of water vapor on super absorbent product have the same form of type III isotherm at ambient temperature with the hysteresis phenomena. For temperatures lower than ambient, the isotherms become deformed because of the chains effect. The polymer is characterized by a multilayer adsorption, which occurs before a full-course is complete. During adsorption reactions, the polymer undergoes rearrangement polymeric network, which results from a cooperative diffusion of the water molecules and from a chain spacing followed by an expansion of the polymeric network. Three types of water molecules adsorbed on polymer were identified: strongly dependent water, adsorbed water, a…

Structure and optical properties of a monolayer single crystal of a cyanine dye

1992

Abstract Molecularly thin single crystals of a cyanine dye prepared by adsorption at a charged surfactant monolayer are studied by polarized optical spectroscopy and electron diffraction. Both techniques independently show a herringbone arrangement of the dye with the long axes of translationally inequivalent molecules forming an angle of 80°. The dye arranges in a primitive rectangular unit cell (a=21.2 A, b=6.14 A) adjacent to an epitaxially related hexagonal cell of the aliphatic tails of the surfactant.

Diorganotin(IV) complexes ofD-galacturonic acid: solid-state and solution-phase structural study

2003

Three diorganotin(IV) complexes of D-galacturonic acid (H2GalA; R = Me, n-Bu, Ph), two of which are new derivatives (R = Me, Ph), have been synthesized and their solid-state and solution-phase investigated by IR, Mossbauer, 1H, 13C and 119Sn NMR spectroscopy. The FTIR data suggest that H2GalA, in the dialkyltin derivatives, behaves as a dianionic ligand, coordinating the tin(IV) atom through an ester-type carboxylate and deprotonated alcoholic hydroxo groups, whereas a bridging carboxylate occurs in the diphenyltin(IV) complex. Octahedral and trigonal bipyramidal local geometries on tin(IV) atoms are proposed for dialkyltin(IV)GalA and diphenyltin(IV)GalA complexes respectively on the basis…

The shell matrix of the freshwater mussel Unio pictorum (Paleoheterodonta, Unionoida). Involvement of acidic polysaccharides from glycoproteins in na…

2007

13 pages; International audience; Among molluscs, the shell biomineralization process is controlled by a set of extracellular macromolecular components secreted by the calcifying mantle. In spite of several studies, these components are mainly known in bivalves from only few members of pteriomorph groups. In the present case, we investigated the biochemical properties of the aragonitic shell of the freshwater bivalve Unio pictorum (Paleoheterodonta, Unionoida). Analysis of the amino acid composition reveals a high amount of glycine, aspartate and alanine in the acid-soluble extract, whereas the acid-insoluble one is rich in alanine and glycine. Monosaccharidic analysis indicates that the in…