Get access

Unfolding of beta-lactoglobulin on the surface of polystyrene nanoparticles: Experimental and computational approaches

Authors

  • Matteo Miriani,

    1. Section of Chemistry and Biomolecular Sciences, DeFENS, University of Milan, Italy
    Search for more papers by this author
  • Ivano Eberini,

    1. Laboratorio di Biochimica e Biofisica Computazionale, Sezione di Biochimica, Biofisica, Fisiologia ed Immunopatologia, Dipartimento di Scienze Farmacologiche e Biomolecolari, University of Milan, Italy
    Search for more papers by this author
  • Stefania Iametti,

    1. Section of Chemistry and Biomolecular Sciences, DeFENS, University of Milan, Italy
    Search for more papers by this author
  • Pasquale Ferranti,

    1. Dipartimento di Agraria, University of Naples “Federico II,” Reggia di Portici, Italy
    Search for more papers by this author
  • Cristina Sensi,

    1. Laboratorio di Biochimica e Biofisica Computazionale, Sezione di Biochimica, Biofisica, Fisiologia ed Immunopatologia, Dipartimento di Scienze Farmacologiche e Biomolecolari, University of Milan, Italy
    Search for more papers by this author
  • Francesco Bonomi

    Corresponding author
    1. Section of Chemistry and Biomolecular Sciences, DeFENS, University of Milan, Italy
    • Correspondence to: Francesco Bonomi, Section of Chemistry and Biomolecular Sciences, DeFENS, University of Milan, Via Celoria 2, 20133, Milan, Italy. E-mail: francesco.bonomi@unimi.it

    Search for more papers by this author

ABSTRACT

Structural changes ensuing from the non-covalent absorption of bovine beta-lactoglobulin (BLG) on the surface of polystyrene nanoparticles were investigated by using spectroscopic approaches, by assessing the reactivity of specific residues, and by limited proteolysis/mass spectrometry. Also, the immunoreactivity of absorbed and free BLG was compared. All these approaches indicated substantial rearrangements of the protein structure in the absorbed state, in spite of the reported structural rigidity of BLG. Changes made evident by experimental measurements were confirmed by computational approaches. These indicate that adsorption-related changes are most marked in the area between the main C-terminal alpha helix and the beta-barrel, and lead to full exposure of the thiol on Cys121, consistent with experimental measurements. In the computational model of bound BLG, both Trp61 and Trp19 also move away from their neighboring quenchers and become solvent-exposed, as indicated by fluorescence measurement. Upon binding, the beta-barrel also loosens, with a substantial increase in immunoreactivity and with noticeable changes in the trypsinolytic pattern. The possible general significance of the structural changes reported here for non-covalently adsorbed BLG is discussed with respect to recognition events involving surface-bound proteins, as are aspects related to the carrier function(s) of BLG, and to its use as a common ingredient in many food systems. Proteins 2014; 82:1272–1282. © 2013 Wiley Periodicals, Inc.

Ancillary