alkaline solution + dilute cupric sulfate + protein= ?

[cotegl at ncaur1.ncaur.gov]

In article <450lk7$b90 at doffen.uninett.no>, jonp at sandnessjoen.vgs.no 
says...
>
>I dont know if this is the right place to mail this question, but I'll 
>give it a try and hope someone can help me. 
>
>Alkaline solution  + diluted cupric sulfate, if you add some protein you 
>get a violet or pink colour.
>
>What is really happening in this process.
>
>I would be so gratefulif anyone culd give me an answer.
>
>Jon Pettersen.
>
This sounds like the well-known and extensively studied Biuret reaction. 
 For starters, check out the following review on the Folin method of 
protein analysis; it should give you some leads regarding your particular 
reaction conditions:

G.L. Peterson, Analytical Biochemistry 100 (1979) 2010220.

Actually, any good book chapter on the chemical analysis of proteins 
should give you the info. you seek.

G. Cote
USDA