The protein is completely denatured by 8M GuHCl, so you will have to refold it if you want to keep it in solution without chaotrope, otherwise it will aggregate. One way to do this is to add the protein sample slowly, drop by drop, into a large volume of buffer with stirring. Another way is to gradually reduce the GuHCl concentration of a dilute solution of the protein. You also have to consider whether it will be necessary to form disulfide bonds.

Some companies offer protein refolding kits to help you in identifying suitable refolding conditions.

Thanks for your answer and time! Adam

i had the same problem. try to set up a dialysis against a buffer with high salt concentration or 0.5-1 M arginine. Both conditions are reported to be useful to mantain your protein in solution