Letters to the Editor 19171 Share this:EmailFacebookTwitterPinterestPocketRedditPrint By Science News January 22, 2003 at 10:43 pm After reading this article, I couldn’t believe that the manuscript didn’t identify the chemical substance involved. Eck Prud’hommeFort Worth, Texas The amino acid mentioned in the story is p -aminophenylalanine .–J. Gorman