Page 1 of 1

Analyzing protein-DNA complex by SEC

Posted: Tue Feb 26, 2019 3:37 pm
by metachrom
If I am analyzing a protein-DNA complex by SEC, should I use protein calibration standards or DNA calibration standards?

Re: Analyzing protein-DNA complex by SEC

Posted: Tue Feb 26, 2019 3:38 pm
by DanSome
With SEC-MALS, you don’t need to use any molar mass calibration standards! The MALS detector directly measures the molar mass of the protein, DNA, or other macromolecule. The measurement is independent of the elution time and specific calibration standards. Whether your molecule has a different density or conformation, compared to your standard, and whether your molecule interacts with the column (thus influencing its elution time) does not matter for SEC-MALS.

[answer provided by Sophia Kenrick, Ph.D., Wyatt Technology]

Re: Analyzing protein-DNA complex by SEC

Posted: Wed Feb 27, 2019 12:52 pm
by DanSome
You will, however, need to know the dn/dc values of the protein and DNA, and UV extinction coefficients at the measurement wavelength (260 or 280 nm, usually).

The dn/dc values of most proteins and DNA are universal to good approximation - 0.186 and 0.17, respectively. The extinction coefficients can be calculated from the sequence, though it is best to measure them.