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Author (up) Causse, B.; Spadini, L.; Sarret, G.; Faure, A.; Travelet, C.; Madern, D.; Delolme, C. openurl 
  Title Xanthan Exopolysaccharide: Cu2+ Complexes Affected from the pH-Dependent Conformational State; Implications for Environmentally Relevant Biopolymers Type Journal Article
  Year 2016 Publication Environmental Science & Technology Abbreviated Journal  
  Volume 50 Issue 7 Pages 3477-3485  
  Keywords  
  Abstract The conformational impact of environmental biopolymers on metal sorption was studied through Cu sorption on xanthan. The apparent Cu2+ complexation constant (logK; Cu2+ + L- <-> CuL+) decreased from 2.9 +/- 0.1 at pH 3.5 to 2.5 +/- 0.1 at pH 5.5 (ionic strength I = 0.1). This behavior is in apparent contradiction with basic thermodynamics, as usually the higher the pH the more cations bind. Our combined titration, circular dichroism and dynamic light scattering study indicated that the change observed in Cu bond strength relates to a conformational change of the structure of xanthan, which generates more chelating sites at pH 3.5 than at pH 5.5. This hypothesis was validated by the fact that the Cu sorption constants on xanthan were always higher than those measured on a mixture of pyruvic and glucuronic acids (logK = 2.2), which are the two constitutive ligands present in the xanthan monomer. This study shows the role of the structural conformation of natural biopolymers in metal bond strength. This finding may help to better predict the fate of Cu and other metals in acidic environmental settings such as aquatic media affected by acid mine drainage, as well as peats and acidic soils, and to better define optimal conditions for bioremediation processes.  
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  ISSN 0013-936x ISBN Medium  
  Area Expedition Conference  
  Notes WOS:000373655800022 HYDRIMZ Approved no  
  Call Number IGE @ juliette.blanchet @ Serial 4118  
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