Journal of Protein Chemistry

, Volume 13, Issue 3, pp 347–354 | Cite as

Reversible and irreversible modifications ofβ-lactoglobulin upon exposure to heat

  • Sabina Cairoli
  • Stefania Iametti
  • Francesco Bonomi
Article

Abstract

Modifications in the exposure to the solvent of hydrophobic residues, changes in their organization into surface hydrophobic patches, and alterations in the dimerization equilibrium ofβ-lactoglobulin upon thermal treatment at neutralpH were studied. Exposure of tryptophan residues was temperature dependent and was essentially completed on the time scale of seconds. Reorganization of generic hydrophobic protein patches on the protein surface was monitored through binding of 1,8-anilinonaphthalenesulfonate, and was much slower than changes in tryptophan exposure. Different phases in surface hydrophobicity changes were related to the swelling and the subsequent collapse of the protein, which formed a metastable swollen intermediate. Heat treatment ofβ-lactoglobulin also resulted in the formation of soluble oligomeric aggregates. The aggregation process was studied as a function of temperature, demonstrating that (i) dimer dissociation was a necessary step in a sequential polymerization mechanism and (ii) cohesion of hydrophobic patches was the major driving force for aggregation.

Key words

Heat protein denaturation protein surface hydrophobicity protein aggregation beta-lactoglobulin 

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Copyright information

© Plenum Publishing Corporation 1994

Authors and Affiliations

  • Sabina Cairoli
    • 1
  • Stefania Iametti
    • 1
  • Francesco Bonomi
    • 1
  1. 1.Dipartimento di Scienze Molecolari Agroalimentari and Centro Interuniversitario per lo Studio delle Macromolecole InformazionaliUniversità di MilanoMilanItaly

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