Conformational Changes and Aggregation of Alginic Acid as Determined By Fluorescence Correlation Spectroscopy

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• 作者：Fabrice Avaltroni ; Marianne Seijo ; Serge Ulrich ; Serge Stoll ; Kevin J. Wilkinson
• 刊名：Biomacromolecules
• 出版年：2007
• 出版时间：January 2007
• 年：2007
• 卷：8
• 期：1
• 页码：106 - 112
• 全文大小：191K
• 年卷期：v.8,no.1(January 2007)
• ISSN：1526-4602

文摘

Insight into the conformations and aggregation of alginic acid was gained by measuring its diffusion coefficientat very dilute concentrations using fluorescence correlation spectroscopy. Both the pH and ionic strength (I) hadan 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 molecularexpansion was observed with increasing pH, whereas (iii) above pH 8 some dissociation of the polymer wasobserved. Increasing I from 0.001 to 0.1 M resulted in a ca. 20% increase in the diffusion coefficient. By couplingthese measurements to molar mass determinations obtained by size exclusion chromatography and monomer sizeestimations determined from ab initio calculations, it was possible to determine the radii of gyration via de Gennesrenormalization 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.