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Søren Vrønning Hoffmann

Conformational changes to deamidated wheat gliadins and b-casein upon adsorption to oil-water emulsion interfaces

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  • Benjamin T. Wong, Australia
  • Jiali Zhai, Australia
  • Søren Vrønning Hoffmann
  • MaryAnn Augustin, Australia
  • Tim J. Wooster, Australia
  • Li Day, Australia
The conformation of deamidated gliadins and b-casein in solution and adsorbed at the interface of oil-inwater
emulsions was studied using synchrotron radiation circular dichroism (SRCD) and front-facefluorescence
spectroscopy. Deamidation led to partial unfolding of gliadins in solution. The a-helix
content of the protein decreased from 35% (in the native form) to 16.3% while the percentage of b-sheet
and unordered structure increased upon deamidation. The secondary structure of deamidated gliadins
was largely unchanged upon adsorption to both tricaprin/water and hexadecane/water interfaces. In
contrast, b-casein adopted a more ordered structure upon adsorption to these two oil/water interfaces,
the a-helix content increased from 5.5% (in solution) to 20% and 22.5% respectively after adsorption to
tricaprin/water and hexadecane/water interfaces. Both deamidated gliadins and b-casein have distinctive
N-terminal hydrophilic and C-terminal hydrophobic domains. Unlike b-casein which contains no
cysteine residue, gliadins have a large number of intramolecular disulphide bonds located in the Cterminal
hydrophobic domain which constrains the conformational freedom of this protein upon
adsorption to oil/water interfaces. The hydrophobicity of the oil phase also has an impact on the
conformation of each protein upon adsorption to the oil/water interfaces e systematic trends were
observed between oil phase polarity from: i) tryptophan fluorescence emission maxima, and ii) the ahelix
content in the adsorbed state. Our results demonstrate that conformational re-arrangement of
proteins upon adsorption to emulsion interfaces is dependent not only on the hydrophobicity of the oil
phase, but more importantly on the conformational flexibility of the protein.
Original languageEnglish
JournalFood Hydrocolloids
Pages (from-to)91-101
Publication statusPublished - May 2012

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