I recently noticed that when boiling my cytochrome sample with TCEP will show degradation product of my cytochromes (shown by extra lower molecular weight bands in heme staining). Since my sample is a c-type cytochrome with no free cysteine, I am quite confused how this could happen? I could not find any literature supporting this idea since most of the literature suggest that TCEP is safe to use with cytochrome c. I am wondering if anyone has any idea how this could happen?