The synthetic polytripeptides (Pro-Pro-Gly)10 and (Pro-Pro-Gly)20 form micro-crystalline structures similar to segmental structures formed by collagen.
Olsen BR, Berg RA, Sakakibara S, Kishida Y, Prockop DJ. The synthetic polytripeptides (Pro-Pro-Gly)10 and (Pro-Pro-Gly)20 form micro-crystalline structures similar to segmental structures formed by collagen. J Mol Biol. 1971 May 14; 57(3):589-95.