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The structure had been commented out with the comment I think the image conflicts with www.commonchemistry.org/ChemicalDetail.aspx?ref=58569-55-4.
They look like isomers, but to check, I re-drew both of them as shown in Isis and let Isis name them

• Met-enkephalin.png - Isis agreed that it was S,R,R - as per IUPAC name on the page, this also agreed with the SMILES notation given.
• http://www.commonchemistry.org/ChemicalDetail.aspx?ref=58569-55-4 - Isis agreed with the text that said it was S,S,S.

Therefore they are different compounds, and I have re-instated the structure.  Ronhjones   ^(Talk) 23:11, 6 September 2009 (UTC) reply