Martin Cann wrote:
>> I'm afraid I haven't had much luck in the literature with this one.
>> Do the CO2/HCO3 and HPO4/H2PO4 intracellular buffer systems cross talk by any known mechanism? For example does one modulate transport systems for the other? What are their relative contributions to intracellular buffering? What are the consequences for the cell on perturbing one, e.g. CO2/HCO3 balance, on the other?
>> I probably haven't explained myself well, having only just read what a Henderson-Hasselbach equation is!
>> Any advice or recommended references would be much appreciated
For multiple simultaneous equilibria, for example those involving more
than buffer, the Henderson-Hasselbach equation or any other *explicit*
algebraic formula of the form
pH = f(concentrations)
cannot be written. One has to use some sort of iterative computer
method to find out the pH, or more generally the concentrations of ions
at equilibrium.
Two regular correspondents to this newsgroup, namely Athel
Cornish-Bowden and myself, have described very simple computer methods
for multiple ionic equilibria:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
@article {Stor7601,
author = "A. C. Storer and A. Cornish-Bowden",
title = "Concentration of $ {\rm MgATP}^ {2-}$ and other ions in
solution. {C}alculation of the true concentrations of species present in
mixtures of associating ions",
journal = "Biochem. J.",
volume = "159",
pages = "1--5",
year = 1976}
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
@article { Kuzm9771,
author = "P. Kuzmi\v{c}",
title = "Fixed-point methods for computing the equilibrium composition
of complex biochemical mixtures",
journal = "Biochem. J.",
volume = "331",
pages = "571--5",
year = "1998" }
These simple methods are not very general (they are *not* guaranteed to
work for very complex equilibria, for example those that involve
oligomerizations), but they are very simple to use and work sufficiently
well for the computation of pH.
Hope this helps,
- Petr
_____________________________________________________________________
P e t r K u z m i c, Ph.D. mailto:pkuzmic at biokin.com
BioKin Ltd. * Software and Consulting http://www.biokin.com
