1206452-13-2Relevant academic research and scientific papers
Hydrophobic peptide channels and encapsulated water wires
Raghavender, Upadhyayula S.,Kantharaju,Aravinda, Subrayashastry,Shamala, Narayanaswamy,Balaram, Padmanabhan
, p. 1075 - 1086 (2010)
Peptide nanotubes with filled and empty pores and close-packed structures are formed in closely related pentapeptides. Enantiomorphic sequences, Boc- DPro-Aib-Xxx-Aib-Val-OMe (Xxx = Leu, 1; Val, 2; Ala, 3; Phe, 4) and Boc-Pro-Aib-DXxx-Aib-DVal-OMe (DXxx = DLeu, 5; DVal, 6; DAla, 7; DPhe, 8), yield molecular structures with a very similar backbone conformation but varied packing patterns in crystals. Peptides 1, 2, 5, and 6 show tubular structures with the molecules self-assembling along the crystallographic six-fold axis (c-axis) and revealing a honeycomb arrangement laterally (ab plane). Two forms of entrapped water wires have been characterized in 2: 2a with d O...O = 2.6 A and 2b with dO...O = 3.5 A. The latter is observed in 6 (6a) also. A polymorphic form of 6 (6b), grown from a solution of methanol-water, was observed to crystallize in a monoclinic system as a close-packed structure. Single-file water wire arrangements encapsulated inside hydrophobic channels formed by peptide nanotubes could be established by modeling the published structures in the cases of a cyclic peptide and a dipeptide. In all the entrapped water wires, each water molecule is involved in a hydrogen bond with a previous and succeeding water molecule. The O-H group of the water not involved in any hydrogen bond does not seem to be involved in an energetically significant interaction with the nanotube interior, a general feature of the one-dimensional water wires encapsulated in hydrophobic environements. Water wires in hydrophobic channels are contrasted with the single-file arrangements in amphipathic channels formed by aquaporins.
