| Protein and peptide amyloidosis is a ubiquitous phenomenon in many diseases,including neurodegenerative diseases,such as Alzheimer's and Parkinson's diseases.The concentration of amyloid peptides in vivo is usually several orders of magnitude lower than the threshold for amyloid formation in vitro.A commonly agreed explanation lies in the special role of molecular surface in vivo,e.g.cytomembrane,which provide many weak intermolecular interaction sites?including hydrogen bonding,electrostatic interaction and among others?with amyloid peptides.Growing evidences have shown that amyloid formation in vivo is highly associated with these complex multi-scale interfaces provide by biological membranes,which may largely enhance the local concentration of amyloid peptides in the extracellular fluid.Macroscopic interfaces with different hydrophobicity,charge,functional groups,and chirality have been constructed to simulate the amyloid formation on flat biological membranes.Growing evidences have revealed that hydrophobicity,charge,functional groups,and other physical and chemical properties of interface greatly influence the kinetics of amyloid fibril formation,which dominates the structure and morphology of diverse assembly aggregates.As an intrinsic biochemical signature of life,molecular chirality directly governs the biomolecule recognition process,and it has been extensively reported recently that surface chirality is an important factor determining the behaviors of cells and bio-macromolecules at liquid-solid interface.Cytomembrane is mainly composed of phospholipids,which also show distinct asymmetric feature due to high chiral preference of L-enantiomers for phospholipids.Therefore,to study how surface chirality influences amyloid peptide assembly at liquid-solid interface,especially at low peptide concentrations,may reveal useful information for comprehensive understanding amyloid formation process in vivo.Here we used N-isobutyryl-cysteine?NIBC?enantiomers modified ultra-flat gold substrates to report the significant influence of surface chirality at the liquid-solid interface on A??1-40?assembly at low concentration of 1?mol·L-1.We show that A??1-40?prefers to assemble into an interesting ring-like aggregates on L-NIBC modified surface?L-surface?,while corresponding D-surface induces rod-like aggregates.We have shown how surface chirality influences the assembly of A??1-40?at low concentration.TERS experiment indicates that ring-like aggregates have similar secondary structure to rod-like aggregates of A??1-40?.It is generally acknowledged that the typical amyloid fibrils are built by hairpin-like?-turn??-hairpin?,which stacks into cross-?-sheet structure in a parallel alignment.Surface chirality can guide the alignment of?-hairpin in parallel or nonparallel fashions through stereoselective interaction.This leads to the generation of rod-like or ring-like aggregates with different Young's moduli.On the basis of site-specific replacement experimental and theoretical study,we also propose the electrostatic interaction sites?R5 and K16?and chiral recognition site?H14?on A??1-40?.It reveals a two-step process of the effect based on the electrostatic interaction enhanced adsorption and subsequent chiral stereoselective interaction which determines parallel or nonparallel assembly of?-hairpin on D-,or L-surface,respectively.These results provide interesting insight to reconsider the mechanism for amyloid formation on biological membrane at low concentrations in vivo.However,various biological nanostructures in vivo including organelles?e.g.,vesicles?and bio-macromolecules?e.g.,globulin?provide abundant nano-bio interfaces with different surface curvature.At these nano-bio interfaces,there are also a certain number of weak intermolecular interaction sites for enzyme and protein binding to.For example,recent study has demonstrated that the A??1-40?fibril structures formed in the presence of the vesicles were remarkably different from those formed in solution.However,the size effects of these nomadic biological nanostructures on the fibrillation kinetics of amyloid,as well as the influence of surface curvature of biomembranes on protein amyloidosis are still unclear.As a kind of widely-used material in biomedical field,gold nanoparticles?AuNPs?is quite similar to biological nanostructures in size.More importantly,after being modified with biomolecules,AuNPs canalso provide abundant nano-bio interfaces with many weak interaction sites.Therefore,AuNPs provide a promising platform for the research of physiological processes occurring at nano-bio interface.In this work,we adopted a series of chemically modified AuNPs to investigate the fibrillation kinetics of A??1-40?peptide at these artificial nano-bio interfaces.We found that the A??1-40?fibrillation was facilitated by the nano-bio interfaces with larger surface curvature radii.We found that the acceleration effect is depending on the amounts and dispersity of the peptide-binding sites provided by corresponding nano-bio interfaces with different surface curvature.The greater the total surface area provided by the AuNPs,the faster fibrillation kinetics of A??1-40?peptide at this artificial nano-bio interfaces.While,on the same total surface area provided by these three AuNPs,the fibrillation kinetics of A??1-40?were faster at the nano-bio interface with larger surface curvature radii than that with smaller surface curvature radii.This study not only provides insight into how nomadic biological nanostructures in vivo participate in physiological processes,but also furthers our understanding on amyloid fibrillation at the biological membranes with different surface curvature.This finding presents a new perspective to better understand how the surface curvature of nano-bio interfaces and even biomembranes influences the amyloid peptide fibrillation in vivo.Moreover,we examed the influence of molecular chirality at nano-bio interface on protein amyloidosis.We used N-isobutyryl-cysteine?NIBC?enantiomers modified gold nanoparticles?AuNPs?with a detameter of 15 nm to report the influence of surface chirality at the nano-bio interface on A??1-40?aggregation and fibrillation.We found both two chiral AuNPs can accelerate the fibrillation of A??1-40?,but the acceleration effect of L-NIBC-AuNCs was better than D-NIBC-AuNCs.However,the CD spectra showed that in presence of D-NIBC-AuNPs,the conformation transition process of A??1-40?form random coil to?-helix was faster than that in presence of L-NIBC-AuNPs.On the basis of experimental and theoretical study,we also propose the electrostatic interaction sites?R5 and K16?and chiral recognition site?H14?on A??1-40?.It reveals a two-step process of the effect based on the electrostatic interaction enhanced adsorption and subsequent chiral stereoselective interaction which determines the rate ofthe aggregation and the conformation transition process of A??1-40?.These results not only provide interesting insight to reconsider the mechanism for amyloid fibrillationatthe chiral interfaces provide by biological nanostructures in vivo,but also would help us design therapeutic drugs for diverse neurodegenerative diseases. |
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