| RNase Control: The Basics Storing RNA Samples Since RNA samples can be contaminated by small amounts of RNases carried over during RNA isolation or due to repeated sample use, proper storage can help minimize these problems. Short-term Storage
For short-term storage, RNA samples can be resuspended in water or buffer and stored at -80°C. If water is the preferred medium, be sure to use nuclease-free water. Using a buffer solution that contains a chelating agent is a better way to store RNA. Chelation of divalent cations such as Mg+2 and Ca+2 will prevent heat-induced strand scission (RNA can be chemically cleaved when heated in the presence of Mg+2). Ambion provides nuclease-free water and a variety of buffers, including TE, 0.1 mM EDTA and THE RNA Storage Solution (which has the added benefit of a low pH), for storing RNA. All are subjected to rigorous quality control procedures and guaranteed to be nuclease free. Long-term Storage
For long-term storage (more than a few weeks), RNA samples are best stored as a salt/ethanol slurry. To do this, take the RNA through all the steps of a regular precipitation with salt (e.g., 1/10 volume of 3 M NaOAc, pH 4.8) and ethanol (2 volumes of 100% ethanol) and store the mixture at -80°C without pelleting the RNA out of solution. The combination of low pH, low temperature and high alcohol content will stabilize the RNA and inhibit all enzymatic activity. Other alternatives for long-term storage are to store the RNA in formamide (Chomczynski, 1992) or to store the RNA in frozen aliquots at -20°C or below. If stored in formamide or ethanol, the RNA will need to be pelleted out of solution prior to quantitation or other manipulation. |