title: Changes in beta-lactoglobulin conformation at the oil/water interface of emulsions studied by synchrotron radiation circular dichroism spectroscopy.
abstract: The structure of proteins at interfaces is a key factor determining the stability as well as organoleptic properties of food emulsions. While it is widely believed that proteins undergo conformational changes at interfaces, the measurement of these structural changes remains a significant challenge. In this study, the conformational changes of beta-lactoglobulin (beta-Lg) upon adsorption to the interface of hexadecane oil-in-water emulsions were investigated using synchrotron radiation circular dichroism (SRCD) spectroscopy. Far-UV SRCD spectra showed that adsorption of beta-Lg to the O/W interface caused a significant increase in non-native alpha-helix structure, accompanied by a concomitant loss of beta-sheet structure. Near-UV SRCD spectra revealed that a considerable disruption of beta-Lg tertiary structure occurred upon adsorption. Moreover, heat-induced changes to the non-native beta-Lg conformation at the oil/water interface were very small compared to the dramatic loss of beta-Lg secondary structure that occurred during heating in solution, suggesting that the interface has a stabilizing effect on the structure of non-native beta-Lg. Overall, our findings provide insight into the conformational behavior of proteins at oil/water interfaces and demonstrate the applicability of SRCD spectroscopy for measuring the conformation of adsorbed proteins in optically turbid emulsions.
authors.affiliation: Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria 3800, Australia.
authors.forename: Jiali
authors.initials: J
authors.lastname: Zhai
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Miles
authors.forename: Leonard Keith
authors.initials: LK
authors.lastname: Pattenden
authors.forename: Tzong-Hsien
authors.initials: TH
authors.lastname: Lee
authors.forename: Mary Ann
authors.initials: MA
authors.lastname: Augustin
authors.forename: B A
authors.initials: BA
authors.lastname: Wallace
authors.forename: Marie-Isabel
authors.initials: MI
authors.lastname: Aguilar
authors.forename: Tim J
authors.initials: TJ
authors.lastname: Wooster
mesh_terms: D000327:Adsorption; D002942:Circular Dichroism / Q000379:methods*; D004655:Emulsions; D007782:Lactoglobulins / Q000737:chemistry*; D010316:Particle Size; D017433:Protein Structure, Secondary; D013056:Spectrophotometry, Ultraviolet; D017356:Synchrotrons
chemical_list: D004655:Emulsions; D007782:Lactoglobulins