A non-intuitive design of a cyclic decapeptide library with unique backbone structural features

An analysis of hydrogen bonding patterns of cyclic decapeptide (CDP) beta-sheet structures has resulted in a 'non-intuitive' design of cyclic decapeptides wherein their beta-turns and residue positions can be fixed by choosing 2 of the 10 residues, i.e. positions i and i+4, to be Prolines or N-substituted residues. This sequence relationship between the two Pro or N-substituted residues is shown to uniquely define the conformation of the CDP. Furthermore, this design of the 2 beta-turn, beta-sheet CDP structure is expected to be characterised by residues disposed in an exclusive fashion in which four residues are on one side of the ring, two on the other and the four corner residues in the beta-turn are in the plane of the ring. This opens up the possibility of fine-tuning the four residues facing one way and /or the two residues facing the other way such that a library containing a myriad of chemically diverse systems could be obtained. The design process along with the molecular modelling of specific CDP-s and the building of a CDP library are discussed in detail.