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Association of Enzymatically and Nonenzymatically Functionalized Caseins Analyzed by Size-Exclusion Chromatography and Light-Scattering Techniques
journal contribution
posted on 2020-02-21, 21:29 authored by Mariella Hannß, Raffaele Andrea Abbate, Eva Mitzenheim, Mahmoud Alkhalaf, Wendelin Böhm, Albena Lederer, Thomas HenleThe influence of covalent protein
modifications resulting from
the Maillard reaction (glycation) of casein and lactose on the noncovalent
association behavior of the protein was studied. Nonenzymatic cross-linking
with methylglyoxal (MGO) and glutaraldehyde (GTA) as well as enzymatic
cross-linking with microbial transglutaminase (mTG) was investigated
in comparison. Molar mass, particle size, and conformational characteristics
of nonmicellar casein associates as well as the extent of intraparticle
protein cross-linking were examined utilizing size-exclusion chromatography
(SEC) combined with UV detection and static and dynamic light scattering.
Cross-linking resulted in the stabilization of a certain fraction
of casein associates, with particle sizes of approximately 30 nm in
radius of gyration (Rg), and promoted
an incorporation of further casein molecules into those particles,
yielding molar masses (Mw) of 1.0–1.2
× 106 g/mol. When caseins were additionally conjugated
with lactose during the early Maillard reaction, a further growth
of the associates up to approximately 50 nm in Rg with a Mw of 2.1 × 106 g/mol was observed. Furthermore, glycation reactions induced
a transition from slightly elongated, random-coil structures toward
more anisotropic conformations. Associates consisting of caseins cross-linked
with GTA appeared to preserve the original particle conformation.