Amyloid Fibril Formation by Peptide LYS (11-36) in Aqueous Trifluoroethanol

摘要

Peptide LYS (11-36),derived from the beta-sheet region of T4 lysozyme,forms an amyloid fibril in aqueous trifluoroethanol (TFE) at elevated temperature.The peptide has a moderate alpha-helix content in 20 and 50% (v/v) TFE solution;large quantities of fibrils were formed after incubation at 55degC for 2 weeks as monitored by a thioflavin T fluorescence assay.No fibrils were observed when the peptide initially existed predominantly as a random coil or as a complete a helix.Our results suggest that a moderate amount of alpha helix and random coil present in the peptide initially facilitates the fibril-formation process,but a high alpha-helix content inhibits fibril formation.Transmission electron microscopy revealed several types of fibril morphologies at different TFE concentrations.The fibrils were highly twisted and consisted of interleaved protofilaments in 50% TFE,while smooth and flat ribbonlike fibrils were found in 20% TFE.In 50% TFE,the fibril growth rate of LYS (11-36) was found to depend strongly on peptide concentration and seeding but was insensitive to solution pH and ionic strength.