 However, this does not cause issues since the thioredoxin is removed in order to trigger the self-assembly reaction with thrombin which results in fiber formation.This removal of the Cu(I) laden thioredoxin removes virtually all copper from the silk structure.The researchers also, through a buffer containing EDTA and by utilizing THPTA (which stabilizes the copper ions), rinsed the fibers resulting in further removal of Cu(I) leaving a <0.1 % by weight trace of copper ions.