We overexpress our proteins from E. coli cells then purify. After centrifuging the cells from growth medium, we sometimes have trouble resuspending the cells in sonication buffer. Long ago, I was trained to do this gently, by swirling small portions of buffer in the centrifuge tubes, but sometimes this takes an inordinately long time. Yesterday we tried using a small paint brush and a gentle stroking action to resuspend them. Does anyone have any suggestions for how to do this step without damaging the cells?