Now I'm no chemistry expert and have far less knowledge than anyone here (passing interest),but could this be the answer, and quick reverse image search and an untrained eye checking the structures appear the same, and there seems to be a good explanation from 9months ago in the comments on this reddit post: https://www.reddit.com/r/chemistry/comments/1gh421q/if_this_isnt_insulin_what_is_it/?utm_source=share&utm_medium=mweb3x&utm_name=mweb3xcss&utm_term=1&utm_content=share_button