Analysis of amyloid fibril structure by scanning cysteine mutagenesis.

Introduction of Cys point mutations into amyloidogenic proteins provides several productive avenues to probing the structures of amyloid fibrils and other nonnative protein aggregates. We describe here the use of single and double Cys mutants to examine the structure of the amyloid beta(1-40) amyloid fibril. Single mutants provide information on local fibril environment around the side chain being investigated, including solvent accessibility within the fibril. Double Cys mutants provide information on whether the mutated side chains make intramolecular contacts within amyloid fibril structure.