Effect of temperature on the structure and cytotoxicity effect of α-lactalbumin-oleic acid complexes against the L1210 cell line

Publication date: Available online 17 July 2015 Source:Food Structure Author(s): Frances Nsonzi, Ahmed Gomaa, Jacqueline Sedman, Ashraf A. Ismail α-Lactalbumin-oleic acid (α-La-OA) complexes with cytotoxicity against selected tumor cells are potential functional food ingredients. This research employed Fourier-transform infrared (FTIR), circular dichroism (CD), and intrinsic fluorescence spectroscopic techniques to investigate the protein and lipid structures in such complexes and their cytotoxic function against the L1210 cell line as mediated by the preparation temperature under conditions amenable to commercial production. Food-grade α-La-OA samples were prepared from 3.53mM α-La and 0.354mM OA at pH 6.5 by heating at 25, 50, 60, 70, or 80oC for 20 min⋅ FTIR spectroscopy revealed that OA, the cytotoxic component in the α-La-OA samples, was protonated. OA concentration increased with temperature up to a ‘saturation limit’ of 50:1 lipid:protein molar ratio attained at 60oC, 70oC, 80oC. Cytotoxicity against tumor cells increased with temperature up to 60oC and then declined, such that α-La-OA samples prepared at 70 and 80oC were not cytotoxic. Near-UV CD spectroscopy demonstrated positive correlation in magnitude of unfolding in protein tertiary structure with temperature (r2 =0.99), and with OA concentration (r2 =0.99) in the 25 to 60oC range. Distinct transitions of unfolding in tertiary structure below and above 60oC were detected by intrinsic fluor...

Source: Food Structure - July 18, 2015 Category: Food Science Source Type: research