I would like to isolate both DNA and RNA from the same cells (mda-mb-231) after some treatments in culture. I will use different kits for each isolation, I will primarily isolate RNA for QPCR, but I want to keep half of cell pellet for further DNA isolation. How can I keep the pellets -20? Keeping cells in PBS buffer OR as liquid free pellet after routine trypsinisation? OR Do you have any other ideas for this? Thanks in advance.