Other primary structures of proteins were proposed by various researchers, such as the diketopiperazine model of Emil Abderhalden and the pyrrol/piperidine model of Troensegaard in 1942.
Varios investigadores propuxeron outros modelos de estruturas primarias das proteínas, como o modelo dicetopiperacina de Emil Abderhalden e o modelo pirrol/piperidina de Troensegaard en 1942.