title: Solvent Controlled Structural Transition of KI4K Self-Assemblies: from Nanotubes to Nanofibrils.
abstract: The structural modulation of peptide and protein assemblies under well-controlled conditions is of both fundamental and practical significance. In spite of extensive studies, it remains hugely challenging to tune the self-assembled nanostructures in a controllable manner because the self-assembly processes are dictated by various noncovalent interactions and their interplay. We report here how to manipulate the self-assembly of a designed, symmetric amphiphilic peptide (KI4K) via the solvent-controlled structural transition. Structural transition processes were carefully followed by the combination of transmission electronic microscopy (TEM), atomic force microscopy (AFM), circular dichroism (CD), Fourier transform infrared spectroscopy (FTIR), and small angle neutron scattering (SANS). The results show that the introduction of acetonitrile into water significantly affected the hydrophobic interactions among hydrophobic side chains while imposing little impact on the β-sheet hydrogen bonding between peptide backbones. A structural transition occurred from nanotubes to helical/twisted ribbons and then to thin fibrils with the addition of acetonitrile due to the reduced hydrophobic interactions and the consequent weakening of the lateral stacking between KI4K β-sheets. The increased intermolecular electrostatic repulsions among lysine side chain amino groups had little effect on the lateral stacking of KI4K β-sheets due to the molecular symmetry. Complementary molecular dynamic (MD) simulations also indicated the solvation of acetonitrile molecules into the hydrophobic domains weakening the coherence between the neighboring sheets.
authors.affiliation: Centre for Bioengineering and Biotechnology, China University of Petroleum (East China) , 66 Changjiang West Road, Qingdao 266580, China.
authors.forename: Yurong
authors.initials: Y
authors.lastname: Zhao
authors.affiliation: Centre for Bioengineering and Biotechnology, China University of Petroleum (East China) , 66 Changjiang West Road, Qingdao 266580, China.
authors.forename: Li
authors.initials: L
authors.lastname: Deng
authors.affiliation: Centre for Bioengineering and Biotechnology, China University of Petroleum (East China) , 66 Changjiang West Road, Qingdao 266580, China.
authors.forename: Jiqian
authors.initials: J
authors.lastname: Wang
authors.affiliation: Centre for Bioengineering and Biotechnology, China University of Petroleum (East China) , 66 Changjiang West Road, Qingdao 266580, China.
authors.forename: Hai
authors.initials: H
authors.lastname: Xu
authors.affiliation: Biological Physics Group, School of Physics and Astronomy, The University of Manchester , Manchester M13 9PL, United Kingdom.
authors.forename: Jian R
authors.initials: JR
authors.lastname: Lu
mesh_terms: D002942:Circular Dichroism; D006860:Hydrogen Bonding; D018625:Microscopy, Atomic Force; D046529:Microscopy, Electron, Transmission; D056004:Molecular Dynamics Simulation; D049329:Nanostructures / Q000737:chemistry*; D043942:Nanotubes / Q000737:chemistry*; D010455:Peptides / Q000737:chemistry*; D017433:Protein Structure, Secondary; D012997:Solvents / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared; D055672:Static Electricity
chemical_list: D010455:Peptides; D012997:Solvents