In article <[hidden email]>,
[hidden email] says...
> i am working on concanavalin A protein.It has the characteristics of
> forming dimer at pH<6.5 and tetramer at pH>6.5. How is this pH affecting the
> formation of oligmers.
> hope you will help me
by changing the ionization state of a amino acid side chain, which
allows/prevents association by electrostatic interactions. Presumably,
this would involve a His, whose side chain pKa is around 6.
You can try to find the X-ray structure of your protein on OCA
(http://bip.weizmann.ac.il/oca-bin/ocaids). You need to check the PDB-
files for the pH, at which the crystalls were grown. PDB-files are plain
text, you can use any text-editor (like notepad) to view them.