Abstract: The structures of six cyclo-peptides([-(D-Ala-Gln₄], [-(D-Val-Gln₄], [-(D-Leu-Gln₄], [-(D-Phe-Gln₄], [-(D-Leu-Trp₄], [(D-Ala-Phe-(D-Ala-Val)₂]) were completely optimized by using semi-empirical molecular orbital method AM1 and affirmed by using vibrational analysis. The structural characteristics of these molecules for self-assembly were revealed. The influences of the substituent on the moleculars structure and self-assembly process were discussed in detail. The computational results show that all the six cyclo-peptides can form dislike conformations despite of their varied side chains, and we can further predict that the any other cyclic octapeptide composed of alternating D- and L- amino acids can also form a disklike structure and self-assembly to nanotube.

Key words: Cyclopeptide, Selfassembly, AM₁