Hydrophobic tail length plays a pivotal role in amyloid beta (25-35) fibril-surfactant interactions

The amyloid -peptide fragment comprising residues 25-35 (A(25-35)) is known to be the most toxic fragment of the full length A peptide which undergoes fibrillation very rapidly. In the present work, we have investigated the effects of the micellar environment (cationic, anionic, and nonionic) on preformed A(25-35) fibrils. The amyloid fibrils have been prepared and characterized by several biophysical and microscopic techniques. Effects of cationic dodecyl trimethyl ammonium bromide (DTAB), cetyl trimethylammonium bromide (CTAB), anionic sodium dodecyl sulfate (SDS), and nonionic polyoxyethyleneoctyl phenyl ether (Triton X-100 or TX) on fibrils have been studied by Thioflavin T fluorescence, UV-vis spectroscopy based turbidity assay and microscopic analyses. Interestingly, DTAB and SDS micelles were observed to disintegrate prepared fibrils to some extent irrespective of their charges. CTAB micelles were found to break down the fibrillar assembly to a greater extent. On the other hand, the nonionic surfactant TX was found to trigger the fibrillation process. The presence of a longer hydrophobic tail in case of CTAB is assumed to be a reason for its higher fibril disaggregating efficacy, the premise of their formation being largely attributed to hydrophobic interactions. Proteins 2016; 84:1213-1223. (c) 2016 Wiley Periodicals, Inc.