After running SDS-PAGE for confirmation (Mini-PROTEAN® TGX™ Precast Gels, Bio-Rad), the fractions from the second linear gradient that show a band of 38 kD were pooled independently and dialyzed overnight against Buffer C (50 mM Tris-HCl, 150 mM NaCl, 1.5 mM DTT). The pool was concentrated using 10K cut-off Amicon® Ultra-15 Centrifugal Filter Units (Millipore Sigma, Burlington, MA, USA). Absorbance at 280 nm was recorded for estimated the protein concentration. These samples were aliquoted and stored with 20% of glycerol at -80 Celsius degrees.