“…Effect of amino acids and ascorbic acid. It was felt that the missing component was the peptidic factor L and attempts were made to replace this material with high levels of individual amino acids (Peters, Prescott, and Snell, 1953;Demain and Hendlin, 1958). Those that showed stimulation at 3 mg per ml were L-glutamine, L-asparagine, L-glutamic acid, and DL-serine.…”