title: Thermodynamics of the proton dissociation of natural polyuronic acids.
abstract: The thermodynamic properties of the dissociation of natural polyuronic acids in dilute aqueous solution at 25 degrees C are reported. The investigation concerns polygalacturonic acid and alginic acids from different sources, including highly homogeneous mannuronic and gulronic fractions and involved potentiometry, isothermal calorimetry, dilatometry and circular dichroism measurements. The dissociation of polyuronic acids was studied as a function of degree of dissociation, concentration of the polymer and ionic strength. Abnormal behavior upon dissociation was observed only in polyguluronic and polygalacturonic acids and attributed to a pH-induced conformational transition and/or to an interchain disaggregation. Direct molecular weight evidence supports the proposed intramolecular transition of polygalacturonate chain.
authors.affiliation: Dipartimento di Biochimica, Biofisica e Chimica delle Macromolecole, University of Trieste, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Cesáro
authors.forename: F
authors.initials: F
authors.lastname: Delben
authors.forename: S
authors.initials: S
authors.lastname: Paoletti
mesh_terms: D000464:Alginates / Q000737:chemistry*; D002151:Calorimetry; D002942:Circular Dichroism; D020723:Glucuronic Acid; D006603:Hexuronic Acids; D006863:Hydrogen-Ion Concentration; D008968:Molecular Conformation; D008970:Molecular Weight; D010368:Pectins / Q000737:chemistry*; D011199:Potentiometry; D011522:Protons; D013816:Thermodynamics
chemical_list: D000464:Alginates; D006603:Hexuronic Acids; D011522:Protons; D010368:Pectins; D020723:Glucuronic Acid; C003181:polygalacturonic acid