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Titleβ-Lactoglobulin nanofibrils can be assembled into nanotapes via site-specific interactions with pectin
Publication TypeJournal Article
Year of Publication2016
AuthorsHettiarachchi, C.A., Melton L.D., McGillivray D.J., Loveday S.M., Gerrard J.A., and Williams M.A.K.
JournalSoft Matter
Pagination756 - 768
Date Published2016
ISSN1744683X (ISSN)
KeywordsCapillary electrophoresis, Electrostatics, Endopolygalacturonase, Galacturonic acids, Hierarchical architectures, Hierarchical assemblies, ionic strength, Methylesterification, Molecules, Nanofibers, Negatively charged, Self assembly, Site-specific interactions, Size exclusion chromatography, Structural modeling, X ray scattering
AbstractControlling the self-assembly of individual supramolecular entities, such as amyloid fibrils, into hierarchical architectures enables the 'bottom-up' fabrication of useful bionanomaterials. Here, we present the hierarchical assembly of β-lactoglobulin nanofibrils into the form of 'nanotapes' in the presence of a specific pectin with a high degree of methylesterification. The nanotapes produced were highly ordered, and had an average width of 180 nm at pH 3. Increasing the ionic strength or the pH of the medium led to the disassembly of nanotapes, indicating that electrostatic interactions stabilised the nanotape architecture. Small-angle X-ray scattering experiments conducted on the nanotapes showed that adequate space is available between adjacent nanofibrils to accommodate pectin molecules. To locate the interaction sites on the pectin molecule, it was subjected to endopolygalacturonase digestion, and the resulting products were analysed using capillary electrophoresis and size-exclusion chromatography for their charge and molecular weight, respectively. Results suggested that the functional pectin molecules carry short (<10 residues) enzyme-susceptible blocks of negatively charged, non-methylesterified galacturonic acid residues in the middle of their homogalacturonan backbones (and possibly near their ends), that specifically bind to sites on the nanofibrils. Blocking the interaction sites on the nanofibril surface using small oligomers of non-methylesterified galacturonic acid residues similar in size to the interaction sites of the pectin molecule decreased the nanotape formation, indicating that site-specific electrostatic interactions are vital for the cross-linking of nanofibrils. We propose a structural model for the pectin-cross-linked β-lactoglobulin nanotapes, the elements of which will inform the future design of bionanomaterials. © 2016 The Royal Society of Chemistry.

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