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This paper concerns a new method of characterizing chitosans with different degrees of acetylation (DA = 2, 11.5 and 21%); it consists of steric exclusion chromatography using a multidetection instrument allowing determination of M, [eta] and RG for each point of the chromatograms. From these data, the Mark-Houwink parameters for intrinsic viscosity and the(More)
The interaction between single-walled carbon nanotubes and photosynthetic reaction centers purified from purple bacterium Rhodobacter sphaeroides R-26 has been investigated. Atomic force microscopy studies provide evidence that reaction center protein can be attached effectively to the nanotubes. The typical diameter of the nanotube is 1-4 nm and 15 +/- 2(More)
This paper describes an original mechanism of evolution of a polysaccharide system occurring during thermal treatments. Under its native conformation, the YAS34 polymer presents a solution character in the dilute and semi-dilute regimes. However, the zero shear rate viscosity indicates existence of interchain interactions which disappear on the deacetylated(More)
This paper concerns the study of the conformational transition of a new exopolysaccharide (YAS34) using experimental techniques such as optical rotation, conductimetric and microcalorimetric measurements as a function of temperature. The behaviors of this polysaccharide in the acid or sodium salt form are compared; a deacetylated sample is also prepared to(More)
Hyaluronan (HA) is a linear charged polysaccharide whose structure is made up of repeating disaccharide units. Apparently conflicting reports have been published about the nature of the helical structure of HA in the solid state. Recent developments in the field of molecular modeling of polysaccharides offer new opportunities to reexamine the structural(More)
The results of the analysis of hydration spectra of Na(+) hyaluronan (HA) performed in a companion study are translated in terms of chemical mechanisms. We find that dried HA is characterized by chains having ordered parts of at least 6 disaccharide repeat units that extend over 60 A. The order is mainly due to C3O3H...O5 and C4O4H...O5 hydrogen bonds that(More)
This article is the first one in a series dedicated to the study of hyaluronan as observed by IR spectrometry. The goal is to determine its hydration mechanism and the structural changes this mechanism implies. Hyaluronan is a natural polysaccharide that is widely used in biomedical applications and cosmetics. Its macroscopic properties are significantly(More)
This paper concerns the study of a new bacterial exopolysaccharide. The ionic properties of the polymer are considered in relation to the first structural results. This polysaccharide is a carboxylic polyelectrolyte with a charge parameter of 1.33, and exhibits usual polyelectrolyte properties with monovalent and Mg2+ ions. In contrast, its affinity for the(More)
This paper concerns the behavior in dilute and demidilute solutions of deacetylated gellan. The conformational transition, controlled by temperature and ionic strength, is investigated. It corresponds to a double-helix single-chain transition. Large ionic selectivity is observed in the helical conformation th at controls the degree of aggregation upon(More)
A new bacterial polysaccharide '1644' is studied in aqueous solutions and in the gel state. The viscometric measurements for dilute and semi-dilute solutions in presence of monovalent salts are usual; however, in presence of divalent cations like Ca2+ an original behaviour is observed, related to intermolecular bonds. For larger polymer concentrations a(More)