Theoretical study for cyclo-peptides geometric characteristics and their assemblies

The structures of six cyclo-peptides, ([-(D-Ala-Gln)(4)-], [-(D-Val-Gln)(4) -] [-(D-Leu-Gln)(4)-] [-(D-Phe-Gln)(4)-], [-(D-Leu-Trp)(4)], [(D-Ala-Phe-D- Ala-Val)(2)]) were completely optimized by using semi-empirical molecular o rbital method AMI and affirmed by using vibrational analysis. The structura l characteristics of these molecules for self-assembly were revealed. The i nfluences of the substituent on the moleculars structure and self-assembly process were discussed in detail. The computational results show that all t he six cyclo-peptides can form dislike conformations despite of their varie d side chains, and we can further predict that the any other cyclic octapep tide composed of alternating D- and L- amino acids can also form a disklike structure and self-assembly to nanotube.