hello everybody..
i am new to this forum... i need sum help regarding the quantification of protein at 280nms.. can anyone please tell me how to go for it if i want to calculate directly in mg/ml...i have tried several times on net bt am nt getting the right way of calculating....may b i think thr is sum prob wid the calculation formula.. i am trying to find on net bt thr they mentioned extinction coefficient at .1% gives conc of protein in mg/ml... bt wen i am trying it experimentally i am nt getting the same conc of protein with 280nms and bradford expt.. kindly please help...
thanks in advance
Deepika

Determine the extinction coefficient of the peptide, for example a prion protein shown below, by pasting in the sequence:
(MKKRPKPGGWNTGGSRYPGQGSPGGNRYPPQGGGTWGQPHGGGWGQPHGGGWGQPHGGGWGQPHGGGWGQGGGTHNQWNKPSKPKTNMKHMAGAAAAGAVVGGLGGYMLGSAMSRPMMHFGNDWEDRYYRENMNRYPNQVYYRPVDQYNNQNNFVHDCVNITIKQHTVTTTTKGENFTETDIKIMERVVEQMCTTQYQKESQAYYDGRRSS )

at a website like http://us.expasy.org/tools/protparam.html

The website will give pertinent information like #amino acids = 211, mw = 23,191.5g/mol, pI 9.58 etc.... It also gives the calculated extinction coefficient (E) at 61,880M-1cm-1. When the extinction coefficient is divided by the mw, it gives 2.668 (g/L)-1.

With this information, we can calculate the protein concentration. Abs280/2.668 x dilution factor = mg/mL.

The extinction coefficient varies for each protein, so paste in your particular sequence into the webpage.

Abs280/2.668 x dilution factor = mg/mL.

hi thanx for ur repy bt i still hav one doubt ... u mentioned that extinction coefficient is divided by the mw, it gives 2.668 (g/L)-1. my ques is how can we can calculate the protein concentration. Abs280/2.668 x dilution factor in mg/mL. wen extinc coeff is in g/L..
anyways thanx 4 ur reply..
Deepika