Resistance of β-casein at the air-water interface to enzymatic cleavage

Jhih Min Lin, Joo Chuan Ang, J. W. White

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    3 Citations (Scopus)

    Abstract

    X-ray reflectivity from an air-buffer interfacial β-casein monomolecular film placed on a solution of chymosin (renin) showed unexpectedly slow proteolytic cleavage. To understand this, the separate structures of β-casein and chymosin, the presentation of each molecule to the other at the air/liquid interface, and that of their mixtures is reported. At the air/solution interface, the hydrophobicity of the protein molecules causes orientation and some deformation of the conformation. When β-casein was presented to a chymosin monomolecular interfacial film, the chymosin was largely displaced from the surface, which was accounted for by the different surfactancy of the two molecules at 25 °C. There was no observable proteolysis. In the reverse experiment, a significant enzymatic degradation and the signature of hydrophobic fragments was observed but only at and above an enzyme concentration of 0.015 mg/mL in the substrate. For comparison, the air/solution interface of premixed β-casein with chymosin in phosphate buffer showed that the film was composed of β-casein proteolytic fragments and chymosin.

    Original languageEnglish
    Pages (from-to)18985-18991
    Number of pages7
    JournalLangmuir
    Volume26
    Issue number24
    DOIs
    Publication statusPublished - 21 Dec 2010

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