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Unfolding of beta‐lactoglobulin on the surface of polystyrene nanoparticles: Experimental and computational approaches
Author(s) -
Miriani Matteo,
Eberini Ivano,
Iametti Stefania,
Ferranti Pasquale,
Sensi Cristina,
Bonomi Francesco
Publication year - 2014
Publication title -
proteins: structure, function, and bioinformatics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.699
H-Index - 191
eISSN - 1097-0134
pISSN - 0887-3585
DOI - 10.1002/prot.24493
Subject(s) - polystyrene , chemistry , beta lactoglobulin , covalent bond , nanoparticle , protein structure , adsorption , whey protein , biophysics , nanotechnology , materials science , chromatography , organic chemistry , biochemistry , polymer , biology
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 Cys 121 , consistent with experimental measurements. In the computational model of bound BLG, both Trp 61 and Trp 19 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.