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Old 06-14-2016, 06:03 AM   #2
Location: Canada

Join Date: Jun 2013
Posts: 56


Low A260/230 can be caused by many contaminants including guanidine salts, phenolics, glycogen or other carbohydrates. In my experience if it is pervasive among different isolation procedures it is likely a co-precipitant originating from the sample tissue itself. Polysaccharides are a common culprit in plant and mollusk tissues and are co-precipitated by the alcohols that are in nearly all commercial kit binding buffers. I have seen commercial column-based kits shear high-molecular weight DNA due to the contaminants.

It would be very helpful if you told us what species, or at least the general group of organisms your are working with. There are a few good home-brew options that I have found helpful for improving A260/230 but I would want to know the taxon before making a recommendation. If you think the RNAlater is the culprit you could soak the sample in PBS or another inert buffer an hour or so before extraction but I would suspect the problem is co-precipitation of something like carbohydrates, which will not be helped by soaking the tissue in such a buffer.

Here is thread you may have already consulted from pmiguel that I have found helpful for diagnosis:
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