After the pellet had dried, it was ground to a fine powder using a pestle and mortar, rinsed with 15% (w/v) TCA in acetone, vortex mixed and then centrifuged at 10,000 rpm for 10 min at 4 °C. The rinsing with TCA/acetone and centrifugation was repeated three times. The pellet was then rinsed with cold 15% (w/v) TCA in water and centrifuged. The rinsing with cold TCA and centrifugation was repeated three times. The pellet was then rinsed with cold 80% (v/v) acetone followed by centrifugation, and this was also repeated three times. The pellet was then air dried.