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

Qi, Phoebe X., Wickham, Edward D., Garcia, Rafael A.
Journal of agricultural and food chemistry 2014 v.62 no.30 pp. 7567
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.