30C-22 |
Ligand and flavor binding functional properties of b-lactoglobulin in the molten globule state induced by high pressure |
J. YANG1, J. R. Powers, S. Clark, A. K. Dunker, and B. G. Swanson. (1) Dept. of Food Science & Human Nutrition, Washington State University, PO Box 646376, Pullman, WA 99164/6376
The molten globule is an intermediate protein structural state between the native and fully denatured states. Protein in the molten globule state possess unique hydrophobic molecular structures with enhanced surface and core hydrophobicity. We observed that high hydrostatic pressure at 600 MPa and 50°C induces b-lactoglobulin (b-LG) into the molten globule state. The objectives of this research are to investigate the binding affinity of b-LG in the native and the molten globule state with 1) hydrophobic retinol, cis-parinaric acid (CPA), and 1-anilino-naphthalene-8-sulfonate (ANS) probes; 2) palmitic acid, capsaicin and carvacrol ligands; 3) a-ionone, and b-ionone, cinnamaldehyde, and vanillin flavor compounds. b -LG at pH 7.0 was treated with HHP of 600 MPa at 50°C for 32 min. Extrinsic fluorescence was used to assay the binding affinity of retinol, CPA, and ANS with b-LG. A displacement assay using retinol, CPA, and ANS fluorescent probes was used to investigate the binding affinity of selected ligands and flavor compounds.Native b-LG binds one molecule of retinol or CPA, and 0.41 molecules of ANS. b-LG in the HHP induced molten globule state binds 0.67 molecule of retinol, 0.63 molecule of CPA, and 0.45 molecules of ANS. The HHP induced molten globule state of b-LG exhibits a statistically significant decrease in affinity for retinol and increases in affinity for CPA and ANS. Native b-LG exhibits greater affinity for palmitic acid, capsaicin, and carvacrol ligands than b-LG in the HHP induced molten globule state with apparent dissociation constants between 2.0´10-6 and 3.6´10-5. However, b-LG exhibits little affinity for a-ionone, b-ionone, cinnamaldehyde or vanillin flavor compounds. Native b-LG exhibits greater binding affinity for ligands and flavor compounds than the HHP induced molten globule state of b-LG. The hydrophobic binding affinity of b-LG is dependent on structures of fluorescent probes, ligands and flavor compounds as well as b-LG.
Session 30C, Food Chemistry: Proteins
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