I have extracted DNA oligonucleotide of size 77 bp from a crushed 10% PAGE gel using 3 rounds of LiClO4 in water. The extracted elute was dried down in a vacuum centrifuge to a certain volume and then precipitated with 5 volumes of Ethanol before taking a spec on a NanoDrop. I do have a significant peak, characteristic of a DNA oligonucleotide, at 260 nm with a A260/A280 ≃ 1.75.
However, I also get a peak at 380 nm. I used to get this since a long time but I could not understand what it meant (did not find any literature reference). I do not want to worry about it too much, as long as I have my oligo, but I would like to know what it is. A colleague of mine also got the same peak, though not very prominent, who did not do a PAGE purification but direct UV Spec after Phenol/Chloroform extraction and LiClO4 in acetone precipitation.
What would you suggest?
Thank you.