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Structural and Thermal Stability of β-Lactoglobulin as a Result of Interacting with Sugar Beet Pectin

Phoebe X. Qi, Edward D. Wickham, Rafael A. Garcia
Journal of agricultural and food chemistry 2014 v.62 no.30 pp. 7567-7576
beets, thermal stability, sugar beet, pectins, fluorescence, circular dichroism spectroscopy, beta-lactoglobulin, chemical interactions, chemical structure, energy, fluorescence emission spectroscopy, heat treatment, infrared spectroscopy, ionic strength, pH
Changes in the structural and thermal stability of β-lactoglobulin (β-LG) induced by interacting with sugar beet pectin (SBP) have been studied by circular dichroism (CD), Fourier transform infrared, and steady-state as well as time-resolved fluorescence spectroscopic techniques. It has been demonstrated that SBP not only is capable of binding to native β-LG but also causes a significant loss in antiparallel β-sheet, ∼10%, accompanied by an increase in either random coil or turn structures. In addition, the interaction also disrupted the environments of all aromatic residues including Trp, Phe, and Tyr of β-LG as evidenced by near-UV CD and fluorescence. When preheated β-LG was combined with SBP, the secondary structure of β-LG was partially recovered, ∼4% gain in antiparallel β-sheet, and Trp19 fluorescence was recovered slightly. Although forming complexes with SBP did not significantly impact the thermal stability of individual secondary structural elements of β-LG, the environment of Trp19 was protected considerably.