protein absorption at 260nm - (Jun/12/2008 )
Do proteins show absorption peak at 260nm under any conditions (change in pH etc)?
Phe has a max at 260, and His at 258
Hi, i have a similar problem, when i spec my protein, the peak is suppose to be at 275nm, but it's at 260nm, and i thought it might be the DNA contamination, but it's not...does anyone have any idea about this? Thank you very much!
Some useful info here:
http://search.vadlo.com/b/q?sn=158621799&a...+peak&rel=0
The long and short of it is that if you are dealing with a purified protein, depending upon its peptide content, it may not peak at 280. 280 is kind of a general, average for a pool of proteins, and most proteins fall in that area (due to tyrosine and tryptophen content).
..
Some useful info here:
http://search.vadlo.com/b/q?sn=158621799&a...+peak&rel=0
The long and short of it is that if you are dealing with a purified protein, depending upon its peptide content, it may not peak at 280. 280 is kind of a general, average for a pool of proteins, and most proteins fall in that area (due to tyrosine and tryptophen content).
..
Thank you! My protein is purified recombinant protein, and the purity is more than 95%...there are 4 tyrosine and no tryptophen, when i spec the protein, the peaks vary, sometimes it's at 275nm, but most of time, it's at 260nm, so i assume its amino acids might be modified...i try to determine the protein concentration, but if its modified, it's not accurate then, do u have any idea how to determine the concentration?
when was the last time your spec was wavelength calibrated?
your spec may need service.
pH is also an important factor. Becareful 
not denature ur protein 
otherwise there wont be
any absorption at 260nm 
Certain metals bound to proteins can give strong signals at wavelengths less than 280 nm. Maybe you have metals in the solution which are bound to the protein? A way to check for metal contamination would be to throw some PAR (4-(2-pyridylazo)resorcinol) at the sample and see if it changes from a yellow color to an orange-red color. Or try adding EDTA to the sample and see if the wavelength shifts.