V.B.2 ELECTROPHORESIS OF RNA THROUGH GELS CONTAINING FORMALDEHYDE 1. Prepare gel-running buffer and formaldehyde.

50 mM sodium acetate 5 mM EDTA (pH 8.0) This buffer yellows with age if exposed to light or autoclaved. Discoloration does not affect its performance appreciably. b..Formaldehyde (F.W.=30.03) is usually obtained as a 37 % solution in water (12.3 M). Check that the pH of the concentrated solution is greater than 4.0. The concentrated solution should be handled and stored in a chemical hood. 2. Prepare the gel by melting agarose in water, cooling to 60°C, and adding 5X gel buffer and formaldehyde to give 1X and 2.2 M final concentrations, respectively. (One part of stock formaldehyde solution should be diluted with 4.6 parts of agarose solution). Note: The fractionation properties of formaldehyde gels with different agarose concentrations have been determined by Lehrach et al. (1977). 3. Prepare the sample by mixing the following in a sterile Eppendorf tube