I follow a protocol to get protein from E.coli cells after sonication.
I used to grow 6 litres of large cultures and add IPTG to express the protein. I centrifuge for 10 mins at 8,000 rpm and get the pellets. Then I do sonication and centrifuge again at 20,000 for 1 hr.
My question is: can I do the last step of centrifugation at 4000 rpm for 2 hr? The centrifuge is no longer working at high speed (20,000rpm)