title: Temperature and pH effects on biophysical and morphological properties of self-assembling peptide RADA16-I.
abstract: It has been found that the self-assembling peptide RADA 16-I forms a beta-sheet structure and self-assembles into nanofibers and scaffolds in favor of cell growth, hemostasis and tissue-injury repair. But its biophysical and morphological properties, especially for its beta-sheet and self-assembling properties in heat- and pH-denatured conditions, remain largely unclear. In order to better understand and design nanobiomaterials, we studied the self-assembly behaviors of RADA16-I using CD and atomic force microscopy (AFM) measurements in various pH and heat-denatured conditions. Here, we report that the peptide, when exposed to pH 1.0 and 4.0, was still able to assume a typical beta-sheet structure and self-assemble into long nanofiber, although its beta-sheet content was dramatically decreased by 10% in a pH 1.0 solution. However, the peptide, when exposed to pH 13.0, drastically lost its beta-sheet structure and assembled into different small-sized globular aggregates. Similarly, the peptide, when heat-denatured from 25 to 70 degrees C, was still able to assume a typical beta-sheet structure with 46% content, but self-assembled into small-sized globular aggregates at much higher temperature. Titration experiments showed that the peptide RADA16-I exists in three types of ionic species: acidic (fully protonated peptide), zwitterionic (electrically neutral peptide carrying partial positive and negative charges) and basic (fully deprotonated peptide) species, called 'super ions'. The unordered structure and beta-turn of these 'super ions' via hydrogen or ionic bonds, and heat Brownian motion under the above denatured conditions would directly affect the stability of the beta-sheet and nanofibers. These results help us in the design of future nanobiomaterials, such as biosensors, based on beta-sheets and environmental changes. These results also help understand the pathogenesis of the beta-sheet-mediated neuronal diseases such as Alzheimer's disease and the mechanism of hemostasis.
authors.affiliation: Institute for NanoBiomedical Technology and Membrane Biology, West China Hospital, Sichuan University, Chengdu, 610041, Sichuan, China.
authors.forename: Zhaoyang
authors.initials: Z
authors.lastname: Ye
authors.forename: Hangyu
authors.initials: H
authors.lastname: Zhang
authors.forename: Hanlin
authors.initials: H
authors.lastname: Luo
authors.forename: Shunkang
authors.initials: S
authors.lastname: Wang
authors.forename: Qinghan
authors.initials: Q
authors.lastname: Zhou
authors.forename: Xinpeng
authors.initials: X
authors.lastname: DU
authors.forename: Chengkang
authors.initials: C
authors.lastname: Tang
authors.forename: Liyan
authors.initials: L
authors.lastname: Chen
authors.forename: Jingping
authors.initials: J
authors.lastname: Liu
authors.forename: Ying-Kang
authors.initials: YK
authors.lastname: Shi
authors.forename: Er-Yong
authors.initials: EY
authors.lastname: Zhang
authors.forename: Rutledge
authors.initials: R
authors.lastname: Ellis-Behnke
authors.forename: Xiaojun
authors.initials: X
authors.lastname: Zhao
mesh_terms: D020816:Amino Acid Motifs; D000818:Animals; D055592:Biophysical Phenomena; D001703:Biophysics; D002942:Circular Dichroism; D006706:Homeostasis; D006863:Hydrogen-Ion Concentration; D007525:Isoelectric Focusing; D018625:Microscopy, Atomic Force; D008958:Models, Molecular; D049329:Nanostructures / Q000737:chemistry / Q000648:ultrastructure; D010455:Peptides / Q000737:chemistry*; D011489:Protein Denaturation; D017434:Protein Structure, Tertiary; D011817:Rabbits; D013696:Temperature
chemical_list: D010455:Peptides