title: Overlapping double turn conformations adopted by tetrapeptides containing non-coded alpha-amino isobutyric acid (Aib) and formation of tape-like structures through supramolecular helix mediated self-assembly.
abstract: Single crystal X-ray diffraction studies and solvent dependent (1)H NMR titrations reveal that a set of four tetrapeptides with general formula Boc-Xx(1)-Aib(2)-Yy(3)-Zz(4)-OMe, where Xx, Yy and Zz are coded L-amino acids, adopt equivalent conformations that can be described as overlapping double turn conformations stabilized by two 4-->1 intramolecular hydrogen bonds between Yy(3)-NH and Boc C=O and Zz(4)-NH and Xx(1)C=O. In the crystalline state, the double turn structures are packed in head-to-tail fashion through intermolecular hydrogen bonds to create supramolecular helical structures. Field emission scanning electron microscopic (FE-SEM) images of the tetrapeptides in the solid state reveal that they can form flat tape-like structures. The results establish that synthetic Aib containing supramolecular helices can form highly ordered self-aggregated amyloid plaque like human amylin.
authors.affiliation: Department of Chemistry, University of Calcutta, 92, A. P. C. Road, Kolkata-700 009, India.
authors.forename: Sudeshna
authors.initials: S
authors.lastname: Kar
authors.forename: Arpita
authors.initials: A
authors.lastname: Dutta
authors.forename: M G B
authors.initials: MG
authors.lastname: Drew
authors.forename: Pradyot
authors.initials: P
authors.lastname: Koley
authors.forename: Animesh
authors.initials: A
authors.lastname: Pramanik
mesh_terms: D000621:Aminoisobutyric Acids / Q000737:chemistry*; D000682:Amyloid / Q000737:chemistry; D003460:Crystallization; D018360:Crystallography, X-Ray; D058228:Islet Amyloid Polypeptide; D008855:Microscopy, Electron, Scanning; D019906:Nuclear Magnetic Resonance, Biomolecular; D009842:Oligopeptides / Q000737:chemistry*; D011487:Protein Conformation; D017433:Protein Structure, Secondary
chemical_list: D000621:Aminoisobutyric Acids; D000682:Amyloid; D058228:Islet Amyloid Polypeptide; D009842:Oligopeptides; C100049:2-aminoisobutyric acid