Electrostatic interactions between hyaluronan and proteins at pH 4: how do they modulate hyaluronidase activity.

Hyaluronan (HA) hydrolysis catalyzed by hyaluronidase (HAase) is inhibited at low HAase over HA ratio and low ionic strength, because HA forms electrostatic complexes with HAase, which is unable to catalyze hydrolysis. Bovine serum albumin (BSA) was used as a model to study the HA-protein electrostatic complexes at pH 4. At low ionic strength, there is formation of (i) neutral insoluble complexes at the phase separation and (ii) small positively-charged or large negatively-charged soluble complexes whether BSA or HA is in excess.

Influence of the passenger domain of a model autotransporter on the properties of its translocator domain.

Autotransporters are a superfamily of proteins secreted by Gram-negative bacteria including many virulence factors. They are modular proteins composed of an N-terminal signal peptide, a surface-exposed 'passenger' domain carrying the activity of the protein, and a C-terminal 'translocator' domain composed of an alpha-helical linker region and a transmembrane beta-barrel. The translocator domain plays an essential role for the secretion of the passenger domain across the outer membrane; however, the mechanism of autotransport remains poorly understood.

Chain-length dependence of the kinetics of the hyaluronan hydrolysis catalyzed by bovine testicular hyaluronidase.

Hyaluronan (HA) has various biological functions that are strongly dependent on its chain length. In some cases, as in inflammation and angiogenesis, long and short chain-size HA effects are antagonistic. HA hydrolysis catalyzed by hyaluronidase (HAase) is believed to be involved in the control of the balance between longer and shorter HA chains.

The influence of isocyanurate content on the bioperformance of hydrocarbon-based polyurethanes.

Bulk, surface and bioactivity of newly synthesized hydroxy telechelic polyisoprene-based (H-HTPI) polyurethane were investigated by means of ATR-FT-IR, contact-angle measurements, cell viability, calcification, and platelet and fibrinogen quantification. The influence of isophorone diisocyanates isocyanurate (I-IPDI) content on these properties was determined. Results generally showed a non-significant difference in these properties when they were compared with a commercially available biomedical polyurethane (PU), such as Tecoflex.

Inner membrane lipids of Escherichia coli form domains.

In prokaryotic cells, the hypothesis of the existence of lipid domains was considered. In order to test this hypothesis and study the organization of lipids in the inner membrane of Escherichia coli, we elaborated Langmuir films mimicking the inner leaflet of this membrane by considering lipids extracted from the inner membrane of E coli by Folch protocol. Lipid monolayers were elaborated by using these extracts (Langmuir technique); the organization of the resulting films was studied at the air-water interface by Brewster angle microscopy and after transfer onto muscovite by atomic force microscopy.

Hyaluronidase activity is modulated by complexing with various polyelectrolytes including hyaluronan.

Hyaluronidase (HAase) plays an important role in the control of the size and concentration of hyaluronan (HA) chains, whose biological properties strongly depend on their length. Our previous studies of HA hydrolysis catalyzed by testicular HAase demonstrated that, whilst the substrate-dependence curve has a Michaelis-Menten shape with a 0.15 mol L(-1) ionic strength, at low ionic strength (5 mmol L(-1)), a strong decrease in the initial hydrolysis rate is observed at high substrate concentrations; the HA concentration for which the initial rate is maximum increases when the HAase concentration is increased.

Contribution of flow field flow fractionation with on line static and dynamic light scattering to the study of hydrosoluble polyelectrolyte complexes.

Water soluble polyelectrolyte complexes (PECs) formed between polyaspartate (anionic polymer) and poly(trimethylammonium propyl methacrylamide chloride) (cationic polymer) were studied by flow field flow fractionation with on-line coupling multi-angle laser light scattering-quasi elastic light scattering-differential refractive index determination (F4/MALLS/QELS/DRI). The separation technique permits to characterize polydisperse PECs. The molar mass of the polycation (PC) influences the stiffness of the PECs and the proportion between single PECs (i.

Behaviour of bacterial division protein FtsZ under a monolayer with phospholipid domains.

Assembly of the tubulin-like protein FtsZ at or near the cytoplasmic membrane is one of the earliest steps in division of bacteria such as Escherichia coli. Exactly what constitutes the site at which FtsZ acts is less clear. To investigate the influence of the membrane phospholipids on FtsZ localization and assembly, we have elaborated with the Langmuir technique a two-lipid monolayer made of dilauryl-phosphatidylethanolamine (DLPE) and dipalmitoyl-phosphatidylglycerol (DPPG).

High-resolution nuclear magnetic resonance spectroscopy studies of polysaccharides crosslinked by sodium trimetaphosphate: a proposal for the reaction mechanism.

An NMR spectroscopy study ((31)P, (1)H, (13)C) of the postulated crosslinking mechanism of sodium trimetaphosphate (STMP) on polysaccharides is reported using methyl alpha-D-glucopyranoside as a model. In a first step, reaction of STMP with Glc-OMe gives grafted sodium tripolyphosphate (STPP(g)). On the one hand, STTP(g) can react with a second alcohol functionality to give a crosslinked monophosphate.

Polyelectrolyte films based on polysaccharides of different conformations: effects on multilayer structure and mechanical properties.

Ultrathin films were prepared with cationic poly(allylamine hydrochloride) (PAH) and two anionic polysaccharides, iota- and lambda-carrageenan, of similar chemical composition but different conformations using the layer-by-layer (LbL) technique. The study of aqueous solutions of carrageenans confirms that iota-carrageenan is at room temperature in helical conformation while lambda-carrageenan is in random coil conformation. Characterization of the multilayers by ellipsometry, circular dichroism, and AFM revealed that iota-carrageenan keeps its helical conformation within the films while lambda-carrageenan chains are in random coil conformation.

Loading and release of small hydrophobic molecules in multilayer films based on amphiphilic polysaccharides.

We report on the loading and release behaviors of polyelectrolyte multilayers based on hydrophobically modified carboxymethylpullulan (CMP) derivatives and poly(ethyleneimine) (PEI) toward hydrophobic dye. The dye-loaded films are obtained according to two different protocols: (i) the postdiffusion approach, which involves the diffusion of the dye within preassembled self-assemblies, and (ii) the precomplexation method, which requires the formation of a water-soluble amphiphilic CMP derivative-dye complex before the multilayer buildup. In both cases, we provide clear evidence for the entrapment of the dye in hydrophobic nanoreservoirs resulting from the aggregation of decyl pendent groups grafted on CMP chains.

Inhibition of hyaluronan hydrolysis catalysed by hyaluronidase at high substrate concentration and low ionic strength.

Hyaluronidase and high levels of hyaluronan are found together in tumours. It is highly likely that hyaluronidase activity controls the balance between high molecular mass hyaluronan and oligosaccharides, and thus plays an important role in cancer development. The hyaluronan hydrolysis catalysed by bovine testicular hyaluronidase was studied as a model.

Channel formation by CarO, the carbapenem resistance-associated outer membrane protein of Acinetobacter baumannii.

It has been recently shown that resistance to both imipenem and meropenem in multidrug-resistant clinical strains of Acinetobacter baumannii is associated with the loss of a heat-modifiable 25/29-kDa outer membrane protein, called CarO. This study aimed to investigate the channel-forming properties of CarO. Mass spectrometry analyses of this protein band detected another 25-kDa protein (called Omp25), together with CarO.

Dynamic organization of mixed Langmuir films of glucose oxidase and stearylamine at the air-water interface.

The structure and the dynamic organization of a mixed Langmuir film of glucose oxidase and stearylamine at the air-water interface have been studied. The film has been first characterized at the air-water interface by surface pressure/area isotherms. The dynamics of the mixed film was studied by following the evolution of the film area at a constant pressure and the evolution of the pressure at a constant area.

Molecular weight characteristics of alginate produced by Azotobacter vinelandii in a membrane bioreactor.

A membrane bioreactor which combines a continuous fermentor and a cross-flow microfiltration module enabling continuous cell recycling and removal of the fermentation products freed of microbial cells was tested for the production of alginate by Azotobacter vinelandii. The molecular weight characteristics of the polysaccharide produced were investigated. The macromolecular characteristics of alginate recovered by first filtering batch fermentation broths through different microporous ceramic membranes with pore sizes varying from 0.

In vitro thrombogenicity investigation of new water-dispersible polyurethane anionomers bearing carboxylate groups.

New segmented polyurethane (PU) anionomers based on hydroxytelechelic polybutadiene were synthesized via an aqueous dispersion process. Incorporation of carboxylic groups was achieved using thioacids of different length. Surface properties were investigated by mean of water absorption analysis and static contact-angle measurements using water, diiodomethane, formamide and ethylene glycol.

Determination of pore size of catanionic icosahedral aggregates.

We show that it is possible to measure the porosity of facetted micron-sized hollow icosahedra of catanionic solutions by performing fluorescence recovery after photobleaching measurements. The size of spontaneous permanent pores in bilayers formed via molecular segregation is compatible with what is observed by freeze-fracture electron microscopy and is discussed versus theoretical expressions of bending energy.

Hemocompatibilty of new ionic polyurethanes: influence of carboxylic group insertion modes.

New segmented polyurethane (PU) anionomers based on hydroxytelechelic polybutadiene (HTPB) were synthesized via two environment-friendly chemical routes. The effects of carboxylic content and ion incorporation mode on the surface properties were investigated by mean of water absorption analysis and static contact angle measurements using water, diiodomethane, formamide and ethylene glycol. Blood compatibility of the PUs was evaluated by in vitro adhesion assay using 111In-radiolabeled platelet rich plasma and 125I-fibrinogen.

Adenophostin A and imipramine are two activators of the olfactory inositol 1,4,5-trisphosphate-gated channel in fish olfatory cilia.

Binding of an odorant to its receptor activates the cAMP-dependent pathway, and also leads to inositol 1,4,5-trisphosphate (InsP(3)) production. This induces opening of a plasma membrane channel in olfactory receptor cells (ORCs). We investigated single-channel properties of this channel in the presence of a phospholipase C (PLC) activator (imipramine) and of a potent activator of the InsP(3)/Ca(2+) release channel (adenophostin A) by reconstituting carp olfactory cilia into planar lipid bilayers.

Coupling Optical and Electrical Measurements in Artificial Membranes: Lateral Diffusion of Lipids and Channel Forming Peptides in Planar Bilayers.

Planar lipid bilayers (PLB) were prepared by the Montal-Mueller technique in a FRAP system designed to simultaneously measure conductivity across, and lateral diffusion of, the bilayer. In the first stage of the project the FRAP system was used to characterise the lateral dynamics of bilayer lipids with regards to phospholipid composition (headgroup, chain unsaturation etc.), presence of cholesterol and the effect of divalent cations on negatively-charged bilayers.

Thermodynamic parameters monitoring the equilibrium shift of enzyme-catalyzed hydrolysis/synthesis reactions in favor of synthesis in mixtures of water and organic solvent.

The main strategy developed to shift the equilibrium state of a hydrolase-catalyzed hydrolysis/synthesis reaction consists in reducing water activity by addition of organic solvents in the reaction medium. We have used several mixtures of water and 1,4-butanediol, ranging from pure water to pure 1,4-butanediol, to study the hydrolysis/synthesis reaction of the N-Cbz-L-tryptophanyl-glycineamide dipeptide, catalyzed by alpha-chymotrypsin. In the presence of 1,4-butanediol, alpha-chymotrypsin also catalyzed the esterification reaction between this diol and N-Cbz-L-tryptophan; this ester hydrolysis/synthesis reaction has thus also been examined.

Occurrence and phenotypic characterization of Yersinia ruckeri strains with biofilm-forming capacity in a rainbow trout farm.

The presence of Yersinia ruckeri in a French fish farm was investigated. Y. ruckeri was isolated mainly from algae and sediment samples rather than from water.

Phosphate deprivation is associated with high resistance to latamoxef of gel-entrapped, sessile-like Escherichia coli cells.

Viable Escherichia coli cells were entrapped in agar gel layers and incubated in a phosphate-limited glucose medium. Immobilized bacteria displayed enhanced alkaline phosphatase activity and overexpressed the outer membrane protein PhoE as compared with free-floating organisms. These observations highlighted the existence of high phosphate deprivation within biofilm-like structures.

Progesterone freeze-dried systems in sublingual dosage form.

Various polymer matrices were tested to enhance progesterone bioavailability as part of an emergency therapy. Among the different polymers used, i.e.

Molecular recognition of carbohydrates by a resorcinarene. Selective transport of alditols through a supported liquid membrane.

A supported liquid membrane (SLM) containing a resorcinarene carrier has been used for the selective transport of erythritol, threitol, ribitol and xylitol from concentrated (1.0-0.01 M) aqueous solutions.