I had a weird results with a dot blot prepared with RNA samples.
- We prepared two dot blots in parallel with the same RNA samples,
- each sample was dotted twice on the same filter, one time the RNA was treated with RNase A as negative control, one time the sample was mocked treated,
- the two filters were hybridized with two different radioactive probes, one filter was hybridized with the probe for the target gene, the second filter with the probe for the control gene. Results were consistent,
- after some months (8 months) the filters were checked for radioactivity, they were cold, no signals were detected,
- the filters were hybridized again but the probes were swapped (i.e. the first filter was now hybridized with the probe for the control gene and viceversa),
- the filter now hybridized with the probe for the control gene (previously was the target gene) gave consistent results. The filter that was previously hybridized with the probe for the control gene and now was hybridized with the probe for the target gene was weird: the first wells of the blot (the uppest ones) had a very faint signal, those at the bottom of the filter had a very strong signal, the problem is that the signal is detected also in wells were no sample was loaded. I can exclude to have exchanged the filters because none of the filters we prepared contained samples at the same position of the supposed empty wells.
Have someone ever experienced a weirdness like this?
Please find attached a picture of an autoradiographic film, the empty wells are supposed to be the three at the bottom on the right.