what does dtt do to proteins
These answers are actually quite wrong. 1) Proteins are soluble and most stable when folded (laws of thermodynamics, entropy gains by folding), nobody wants to purify unfolded, catalytically inactive protein. 2) DTT does not cause unfolding. Does not. Proteins are often found in highly reducing environments, so DTT stops oxidation of the protein (especially helpful in metal containing proteins) and the formation of unwanted disulfide bonds. If your protein requires disulfide bonds then you may not want to use DTT.