We used two criteria to detect the identical sequences of different conformations: The stringent criterion: As we are most interested in the conversion between alpha helices and beta strand, we constraint the positions of detected identical sequences to contain both ‘E’ an ‘H’ (such as ‘EEEEEEE’ vs ‘HHHHHHH’). The loose criterion: To make our result comparable to previous studies, we also impose a less stringent criterion, where at least one of the middle two residues in the identical sequences has to contain both ‘E’ and ‘H’ (such as ‘CCCEEECC’ vs ‘CCHHHHHH’).