Methods for detecting the presence of at least one misfolded form of sod1 in a biological sample

A method of preparing a purified human Superoxide Dismutase 1 (SOD1) substrate for use in a real-time quaking induced conversion assay, the method comprising:

• a. performing chromatography on a sample of cells expressing a human SOD1 protein having an amino acid sequence of SEQ ID NO:1 or SEQ ID NO:2, to produce an eluate;
• and
• b. either:
• i. incubating the eluate for at least 6 hours at a temperature of about 20° C. to about 22° C. in at least 20 mM to about 30 mM of at least one buffer having a pH between about 6.0 to about 8.0 to produce a purified human SOD1 substrate;
• or
• ii. performing, in the presence of at least 20 mM to about 30 mM of at least one buffer having a pH between about 6.0 to about 8.0, buffer exchange, exchange using an exclusion column which removes any salts and/or contaminants less than 10 kDa, or dialysis for at least 7 hours, at least 8 hours, at least 9 hours, at least 10 hours, at least 11 hours, at least 12 hours, at least 13 hours, at least 14 hours, at least 15 hours, at least 16 hours, at least 17 hours, at least 18 hours, at least 19 hours, at least 20 hours, at least 21 hours, at least 22 hours, at least 23 hours, or at least 24 hours to produce a purified human SOD1 substrate.