Optimizing the northern blot procedure.

We describe methods for preparing formaldehyde-agarose gels for use in Northern blotting which yield consistent high quality results. Using these methods, we tested seven different commercially available membranes in Northern blots. Each membrane was handled as specified by the manufacturer in a course of hybridization, stripping and rehybridization. Filter background was low in all cases, but the intensity of the signal generated by specific hybridization varied markedly between filters after both the first and second hybridization.