Linked Life Data

19566184

Source:http://linkedlifedata.com/resource/pubmed/id/19566184

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PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
24
pubmed:dateCreated
2009-7-1
pubmed:abstractText
We studied by light scattering and small angle x-rays scattering (SAXS) conformations and solvation of plant tannins (oligomers and polymers) in mixed water-ethanol solutions. Their structures are not simple linear chains but contain about 6% of branching. Ab initio reconstruction reveals that monomers within a branch are closely bound pairwise. The chains are rather rigid, with the Kuhn length b = 13+/-3 nm, corresponding to about 35 linearly bound monomers. Contribution of solvation layer to SAXS intensity varies in a nonmonotonic way with ethanol content phi(A), which is an indication of amphipathic nature of tannin molecules. Best solvent composition phi(A)(B) is a decreasing function of polymerization degree N, in agreement with increasing water solubility of tannins with N. Polymers longer than b present a power-law behavior I approximately Q(-d) in the SAXS profile at high momentum transfer Q. The monotonic decrease in d with increasing phi(A) (from 2.4 in water to 1.9 in ethanol) points that the tannins are more compact in water than in ethanol, presumably due to attractive intramolecular interactions in water. Tannins were then oxidized in controlled conditions similar to real biological or food systems. Oxidation does not produce any intermolecular condensation, but generates additional intramolecular links. Some oxidation products are insoluble in water rich solvent. For that reason, we identify these species as a fraction of natural tannins called "T1" in the notation of Zanchi et al. [Langmuir 23, 9949 (2007)]. Within the fraction left soluble after oxidation, conformations of polymeric tannins, despite their higher rigidity, remain sensitive to solvent composition.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Jun
pubmed:issn
1089-7690
pubmed:author
pubmed:issnType
Electronic
pubmed:day
28
pubmed:volume
130
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
245103
pubmed:meshHeading
pubmed:year
2009
pubmed:articleTitle
Rigidity, conformation, and solvation of native and oxidized tannin macromolecules in water-ethanol solution.
pubmed:affiliation
Laboratoire de Physique Théorique et Hautes Energies, 4 place Jussieu, BP 126, 75252 Paris Cedex 05, France. drazen.zanchi@lpthe.jussieu.fr
pubmed:publicationType
Journal Article, Research Support, Non-U.S. Gov't