title: Conformational changes and aggregation of alginic acid as determined by fluorescence correlation spectroscopy.
abstract: Insight into the conformations and aggregation of alginic acid was gained by measuring its diffusion coefficient at very dilute concentrations using fluorescence correlation spectroscopy. Both the pH and ionic strength (I) had an important influence on the diffusion coefficient of the polysaccharide. For pH, three effects were isolated: (i) below pH 4, the charge density decreased causing increased aggregation; (ii) between pH 4 and 8, a molecular expansion was observed with increasing pH, whereas (iii) above pH 8 some dissociation of the polymer was observed. Increasing I from 0.001 to 0.1 M resulted in a ca. 20% increase in the diffusion coefficient. By coupling these measurements to molar mass determinations obtained by size exclusion chromatography and monomer size estimations determined from ab initio calculations, it was possible to determine the radii of gyration via de Gennes renormalization theory. From diffusion coefficients and radii of gyration obtained as a function of ionic strength, persistence lengths (total, electrostatic, and intrinsic) were calculated from the Benoit-Doty relationship.
authors.affiliation: Analytical and Biophysical Environmental Chemistry, University of Geneva, 30 Quai E. Ansermet, Geneva CH-1211, Switzerland.
authors.forename: Fabrice
authors.initials: F
authors.lastname: Avaltroni
authors.forename: Marianne
authors.initials: M
authors.lastname: Seijo
authors.forename: Serge
authors.initials: S
authors.lastname: Ulrich
authors.forename: Serge
authors.initials: S
authors.lastname: Stoll
authors.forename: Kevin J
authors.initials: KJ
authors.lastname: Wilkinson
mesh_terms: D000464:Alginates / Q000737:chemistry*; D001671:Biochemistry / Q000379:methods; D020723:Glucuronic Acid / Q000737:chemistry; D006603:Hexuronic Acids / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D007477:Ions; D044662:Macrocystis / Q000378:metabolism; D046911:Macromolecular Substances; D008956:Models, Chemical; D015233:Models, Statistical; D008968:Molecular Conformation; D011108:Polymers / Q000737:chemistry; D013050:Spectrometry, Fluorescence / Q000379:methods
chemical_list: D000464:Alginates; D006603:Hexuronic Acids; D007477:Ions; D046911:Macromolecular Substances; D011108:Polymers; D020723:Glucuronic Acid