Protein aggregation is a prevalent phenomenon. It is important to study protein aggregation under different solution conditions. In this study, using 1-anilinonaphthalene-8-sulfonic acid (ANS) fluorescence spectra, we investigated the critical micelle concentration (CMC) of 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP). We also studied the effects of DOTAP on amyloid aggregation of β-lactoglobulin using intrinsic fluorescence spectra, circular dichroism spectra, thioflavin T fluorescence, a Congo red binding assay and transmission electron microscopy. We observed that DOTAP had a dual role on β-lactoglobulin amyloid aggregation. DOTAP inhibited the amyloid aggregation below the CMC, while it had the opposite effect above the CMC. Moreover, the results of transmission electron microscopy showed that spherical aggregates were formed above the CMC. These results led us to conclude that cationic lipids could be used as modulators of protein self-assembly.
Keywords: 1,2-dioleoyl-3-trimethylammonium-propane(DOTAP); Amyloid aggregation; Critical micelle concentration (CMC); Spherical aggregation; β-lactoglobulin (β-LG).
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