Nanodrop absorbtion at 290 nm??? - (Jan/13/2012 )

Hi All

Been a while since I've posted here... anyway, I have some students working with me extracting DNA from some (very old) samples of bird crop contents (a.k.a bird barf) and bird feces.

They are using Qiagen DNEasy kits to extract DNA, and then I have them quantitate DNA concentrations with a nanodrop. We often have relatively high absorbance a 230 nm, due to salt carry over -- doesn't seem to affect the results much, so I don't sweat it, and of course a second peak at 260. Usually next to nothing at 280, and most of the time the 260/280 ratio is 1.7-2.1

But for several samples that one of the interns extracted, she's getting very strong peaks at 290 nm! I've never encountered that before, and am wondering if she's maybe... doing something incorrectly? If she were failing to wash adequately though, I would just expect a big old peak at 230... I've tried searching for what could absorb at that wavelength and just get random chemistry students loooking for the answers to their homework.

My other thought is that it could be something particular to the digestive systems of birds, but I really don't know.

Has anyone else gotten 290 in their DNA extractions? If so, what was it?

hello there,
study these two articles :

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2242397/
http://arthritis-research.com/content/3/4/E002

also it could be possibility of Shifts