A somewhat overlooked challenge is the complexity of protein folding that researchers may need to address during synthetic protein preparation. Typically, a solution of the protein in chaotropic conditions such as guanidine or urea is prepared and then diluted into a refolding buffer. Many larger proteins require chaperones for efficient folding, particularly in vivo where direct control of refolding conditions is limited. Recently, it was shown that the GroEL/ES chaperone protein can efficiently fold both enantiomers (L-and D-) of synthetic DapA protein. This observation suggested that the protein chaperone activity can be achiral and may find broad utility in the pursuit of mirror-image life systems. Two specific challenges associated with protein folding that will be discussed here include correct oxidation of disulfide bonds and installation of post-translational modifications.