Question

Two proteins have been purified by a researcher, called Protein A and Protein B. She determines the extinction coefficient for each, generating the following information: Protein A: 1 mg/ml solution OD280=1.1 Protein B: 1 mg/ml solution OD280=0.27 She then purifies a new preparation of Protein A. Her new preparation of Protein A has 4 ml total, and when it is diluted 1/10 it gives OD280=0.44. What is the total protein in her new preparation of Protein A in mg?

Answer 1

Protein A = 1mg/ml OD at 280= 1.1 initially

The new prep for protein A is 4 ml diluted into 1:10

New OD= 0.44

For concentration

Mg/ml= Absorbance at 280 nm divided by path length (cm)

=0.44/ 1

= 0.44 mg/ ml

*Here, path length is taken as 1 since most of the spectrophotometers have a path length of 1cm . The concentration of the new protein A is 0.44 mg/ml