Preserving free thiols of intrinsically disordered tau protein without the use of a reducing agent

Intrinsically disordered proteins (IDPs) represent key mediators in many physiological as well as pathological processes. Solution-exposed cysteines of IDPs are highly reactive and therefore reducing agents are frequently included during their preparation to prevent formation of nonnative disulfides. However, reductants can potentially interfere with subsequent assays performed on the purified IDPs. Herein we report a method for purification of IDP tau in an atmosphere of inert argon, which eliminates the need for reducing agents. We have used this method for preparing several IDP tau isoforms and found it useful in the investigation of monomeric tau toxicity in rat cerebral neurons.