MadSci Network: Biochemistry |
Hi Vandi,
I am a little unclear about exactly what you are trying to calculate, but I will answer with a speculation about what you mean.... In your first sentence you ask how to figure out the concentrations of amino acid species at different pHs. I am assuming by "species" you mean you want to know at a given pH what concentration of the amino acid is +1 charged, and how much is +2 charged, etc?
The Henderson-Hasselbalch equation relates pH, pKa and the concentrations of the two species on either side of the pKa value (i.e. the concentrations of the 0 and +1 species, or the concentrations of the +1 and +2 species, etc). The equation is:
pH = pKa + log([HA]/[A])
Of course, you will have to look up the pKa of the various ionizable groups in the amino acid of interest, but that information is easy to find.
Hope this helps!
Karin
Try the links in the MadSci Library for more information on Biochemistry.