?Why alkaline pH in protein refold?

[lgbell]

In article <3624020E.C612EAA5 at student.mahidol.ac.th>, 
g3937506 at STUDENT1.MAHIDOL.AC.TH says...
>
>Dear all:
>
>Is it neccessary to refold a protein in alkaline pH?
>Does this prevent any chemical modification ?
>Thanks for all suggestion.
>
>Jongrak
>
>--
>-----------------------------------Mr. Jongrak Kittiworakarn
>                                   g3937506 at student.mahidol.ac.th

Well that depends.  An alkaline pH will facillitate the formation of 
disulfide bridges (Cys-Cys) under atmospheric oxidation.  The 
traditional assumption is that the thermodynamically stable 
disulfide configuration is the same as the naturally occurring or 
active one.  So I guess the rationale is that, the protein initially 
re-folds according to its primary sequence and disulfide bridges, if 
present, then form accordingly from atmospheric oxidation of Cys and 
stabalise this final conformation.

Obviously if the protein does not contain Cys then under this 
explanation the re-folding pH can be varied.  Obviously the optimuin 
pH to use would be related to the environment the protein naturally 
exists in or is biosynthesised in.  

Hope this helps,
Len
lgbell at liv.ac.uk