Thanks for your reply.
I dont have access to NMR (well our department is not well equipped).i dont have much experience with protein chemistry so I read in some of the protein purification protocols books - it was said that when protein is purified under denaturing conditions with urea, removal of urea by dialysis will bring the protein to native state. so using the procedure that i mentioned before i was trying to do that. My experiment is to use the pure protein for immunizing mice and look at their immune response. Anyway i will try to get some help NMR from someone. Thanks again for your suggestions.