4 M guanidine HCl and hydroxylamine.
Buffer to pH 9 with 0.2 M NaCO3. Will need to add ~ 16 volumes of NaCO3 to reach pH 9 since solution is very acidic.
Add 5mM DTT, 1mM N-ethylmaleimide and 1x TXSWB to protein solution.
Mix equal volumes of guanidine-hydroxylamine solution with your protein. Final protein conc. should be 1-5 mg/ml.
Adjust pH to 9 if necessary with NaCO3
Incubate 4-8 hours at 45ºC.
Neutralize pH with acetic acid.