1
|
Samui S, Biswas S, Basak S, Ghosh S, Muniyappa K, Naskar J. De novo designed aliphatic and aromatic peptides assemble into amyloid-like cytotoxic supramolecular nanofibrils. RSC Adv 2024; 14:4382-4388. [PMID: 38304566 PMCID: PMC10831423 DOI: 10.1039/d3ra07869h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2023] [Accepted: 01/16/2024] [Indexed: 02/03/2024] Open
Abstract
Peptides are very interesting biomolecules that upon self-association form a variety of thermodynamically stable supramolecular structures of nanometric dimension e.g. nanotubes, nanorods, nanovesicles, nanofibrils, nanowires and many others. Herein, we report six peptide molecules having a general chemical structure, H-Gaba-X-X-OH (Gaba: γ-aminobutyric acid, X: amino acid). Out of these six peptides, three are aromatic and the others are aliphatic. Atomic force microscopic (AFM) studies reveal that except peptide 6 (H-Gaba-Trp-Trp-OH), all the reported peptides adopt nanofibrillar morphology upon aggregation in aqueous medium. These supramolecular assemblies can recognize amyloid-specific molecular probe congo red (CR) and thioflavine t (ThT) and exhibit all the characteristic properties of amyloids. The MTT cell viability assay reveals that the toxicity of both aliphatic and aromatic peptides increases with increasing concentration of the peptides to both cancer (HeLa) and non-cancer (HEK 293) cells. Of note, the aromatic peptides show a slightly higher cytotoxic effect compared to the aliphatic peptides. Overall, the studies highlight the self-assembling nature of the de novo designed aliphatic and aromatic peptides and pave the way towards elucidating the intricacies of pathogenic amyloid assemblies.
Collapse
Affiliation(s)
- Satyabrata Samui
- Department of Biochemistry and Biophysics, University of Kalyani Nadia WB 741235 India
| | - Soumi Biswas
- Department of Biochemistry and Biophysics, University of Kalyani Nadia WB 741235 India
| | - Shubhanwita Basak
- Department of Biochemistry and Biophysics, University of Kalyani Nadia WB 741235 India
| | - Shreya Ghosh
- Department of Biochemistry and Biophysics, University of Kalyani Nadia WB 741235 India
| | - K Muniyappa
- Department of Biochemistry, Indian Institute of Science Bangalore Karnataka 560 012 India
| | - Jishu Naskar
- Department of Biochemistry and Biophysics, University of Kalyani Nadia WB 741235 India
| |
Collapse
|
2
|
Smorodina E, Kav B, Fatafta H, Strodel B. Effects of ion type and concentration on the structure and aggregation of the amyloid peptide A β 16 - 22 $$ {\boldsymbol{\beta}}_{16-22} $$. Proteins 2023. [PMID: 37964477 DOI: 10.1002/prot.26635] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2023] [Revised: 10/18/2023] [Accepted: 10/30/2023] [Indexed: 11/16/2023]
Abstract
Among the various factors controlling the amyloid aggregation process, the influences of ions on the aggregation rate and the resulting structures are important aspects to consider, which can be studied by molecular simulations. There is a wide variety of protein force fields and ion models, raising the question of which model to use in such studies. To address this question, we perform molecular dynamics simulations of Aβ16-22 , a fragment of the Alzheimer's amyloid β peptide, using different protein force fields, AMBER99SB-disp (A99-d) and CHARMM36m (C36m), and different ion parameters. The influences of NaCl and CaCl2 at various concentrations are studied and compared with the systems without the addition of ions. Our results indicate a sensitivity of the peptide-ion interactions to the different ion models. In particular, we observe a strong binding of Ca2+ to residue E22 with C36m and also with the Åqvist ion model used together with A99-d, which slightly affects the monomeric Aβ16-22 structures and the aggregation rate, but significantly affects the oligomer structures formed in the aggregation simulations. For example, at high Ca2+ concentrations, there was a switch from an antiparallel to a parallel β-sheet. Such ionic influences are of biological relevance because local ion concentrations can change in vivo and could help explain the polymorphism of amyloid fibrils.
Collapse
Affiliation(s)
- Eva Smorodina
- Institute of Biological Information Processing: Structural Biochemistry, Forschungszentrum Jülich, Jülich, Germany
- Department of Immunology, University of Oslo and Oslo University Hospital, Oslo, Norway
| | - Batuhan Kav
- Institute of Biological Information Processing: Structural Biochemistry, Forschungszentrum Jülich, Jülich, Germany
| | - Hebah Fatafta
- Institute of Biological Information Processing: Structural Biochemistry, Forschungszentrum Jülich, Jülich, Germany
- Institute of Theoretical and Computational Chemistry, Heinrich Heine University Düsseldorf, Düsseldorf, Germany
| | - Birgit Strodel
- Institute of Biological Information Processing: Structural Biochemistry, Forschungszentrum Jülich, Jülich, Germany
- Institute of Theoretical and Computational Chemistry, Heinrich Heine University Düsseldorf, Düsseldorf, Germany
| |
Collapse
|
3
|
Piedmont ER, Christensen EE, Krauss TD, Partridge BE. Amphiphilic dendrons as supramolecular holdase chaperones. RSC Chem Biol 2023; 4:754-759. [PMID: 37799582 PMCID: PMC10549246 DOI: 10.1039/d3cb00086a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2023] [Accepted: 09/05/2023] [Indexed: 10/07/2023] Open
Abstract
The aggregation of incompletely or incorrectly folded proteins is implicated in diseases including Alzheimer's, cataracts, and other maladies. Natural systems express protein chaperones to prevent or even reverse harmful protein aggregation. Synthetic chaperone-like systems have sought to mimic the action of their biological counterparts but typically require substantial optimization and high concentrations to be functional, or lack programmability that would enable the targeting of specific protein substrates. Here we report a series of amphiphilic dendrons that undergo assembly and inhibit the aggregation of fragment 16-22 amyloid β protein (Aβ16-22). We show that monodisperse dendrons with hydrophilic tetraethylene glycol chains and a hydrophobic core based on naphthyl and benzyl ethers undergo supramolecular assembly in aqueous solutions to form sphere-like particles. The solubility of these dendrons and their assemblies is tuned by varying the relative sizes of their hydrophilic and hydrophobic regions. Two water-soluble dendrons are discovered and shown, via fluorescence experiments with rhodamine 6G, to generate a hydrophobic environment. Furthermore, we demonstrate that sub-stoichiometric concentrations of these amphiphilic dendrons stabilize Aβ16-22 peptide with respect to aggregation, mimicking the activity of holdase chaperones. Our results highlight the potential of these amphiphilic molecules as the basis for a novel approach to artificial chaperones that may address many of the challenges associated with existing synthetic chaperone mimics.
Collapse
Affiliation(s)
| | - Erin E Christensen
- Department of Chemistry, University of Rochester Rochester NY 14627-0216 USA
| | - Todd D Krauss
- Department of Chemistry, University of Rochester Rochester NY 14627-0216 USA
- Institute of Optics, University of Rochester Rochester NY 14627-0186 USA
| | | |
Collapse
|
4
|
Kaur R, Narang SS, Singh P, Goyal B. Structural and molecular insights into tacrine-benzofuran hybrid induced inhibition of amyloid-β peptide aggregation and BACE1 activity. J Biomol Struct Dyn 2023; 41:13211-13227. [PMID: 37013977 DOI: 10.1080/07391102.2023.2191722] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2022] [Accepted: 01/16/2023] [Indexed: 04/05/2023]
Abstract
Amyloid-β (Aβ) aggregation and β-amyloid precursor protein cleaving enzyme 1 (BACE1) are the potential therapeutic drug targets for Alzheimer's disease (AD). A recent study highlighted that tacrine-benzofuran hybrid C1 displayed anti-aggregation activity against Aβ42 peptide and inhibit BACE1 activity. However, the inhibition mechanism of C1 against Aβ42 aggregation and BACE1 activity remains unclear. Thus, molecular dynamics (MD) simulations of Aβ42 monomer and BACE1 with and without C1 were performed to inspect the inhibitory mechanism of C1 against Aβ42 aggregation and BACE1 activity. In addition, a ligand-based virtual screening followed by MD simulations was employed to explore potent new small-molecule dual inhibitors of Aβ42 aggregation and BACE1 activity. MD simulations highlighted that C1 promotes the non aggregating helical conformation in Aβ42 and destabilizes D23-K28 salt bridge that plays a vital role in the self-aggregation of Aβ42. C1 displays a favourable binding free energy (-50.7 ± 7.3 kcal/mol) with Aβ42 monomer and preferentially binds to the central hydrophobic core (CHC) residues. MD simulations highlighted that C1 strongly interacted with the BACE1 active site (Asp32 and Asp228) and active pockets. The scrutiny of interatomic distances among key residues of BACE1 highlighted the close flap (non-active) position in BACE1 on the incorporation of C1. The MD simulations explain the observed high inhibitory activity of C1 against Aβ aggregation and BACE1 in the in vitro studies. The ligand-based virtual screening followed by MD simulations identified CHEMBL2019027 (C2) as a promising dual inhibitor of Aβ42 aggregation and BACE1 activity.Communicated by Ramaswamy H. Sarma.
Collapse
Affiliation(s)
- Rajdeep Kaur
- Department of Chemistry, Faculty of Basic and Applied Sciences, Sri Guru Granth Sahib World University, Fatehgarh Sahib, Punjab, India
| | - Simranjeet Singh Narang
- Department of Chemistry, Faculty of Basic and Applied Sciences, Sri Guru Granth Sahib World University, Fatehgarh Sahib, Punjab, India
| | - Pritpal Singh
- Department of Chemistry, Faculty of Basic and Applied Sciences, Sri Guru Granth Sahib World University, Fatehgarh Sahib, Punjab, India
| | - Bhupesh Goyal
- School of Chemistry & Biochemistry, Thapar Institute of Engineering & Technology, Patiala, Punjab, India
| |
Collapse
|
5
|
Tang X, Han W. Multiscale Exploration of Concentration-Dependent Amyloid-β(16-21) Amyloid Nucleation. J Phys Chem Lett 2022; 13:5009-5016. [PMID: 35649244 DOI: 10.1021/acs.jpclett.2c00685] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Atomic descriptions of peptide aggregation nucleation remain lacking due to the difficulty of exploring complex configurational spaces on long time scales. To elucidate this process, we develop a multiscale approach combining a metadynamics-based method with cluster statistical mechanics to derive concentration-dependent free energy surfaces of nucleation at near-atomic resolution. A kinetic transition network of nucleation is then constructed and employed to systematically explore nucleation pathways and kinetics through stochastic simulations. This approach is applied to describe Aβ16-21 amyloid nucleation, revealing a two-step mechanism involving disordered aggregates at millimolar concentration, and an unexpected mechanism at submillimolar concentrations that exhibits kinetics reminiscent of classical nucleation but atypical pathways involving growing clusters with structured cores wrapped by disordered surface. When this atypical mechanism is operative, critical nucleus size can be reflected by the nucleation reaction order. Collectively, our approach paves the way for a more quantitative and detailed understanding of peptide aggregation nucleation.
Collapse
Affiliation(s)
- Xuan Tang
- State Key Laboratory of Chemical Oncogenomics, Guangdong Provincial Key Laboratory of Chemical Genomics, School of Chemical Biology and Biotechnology, Peking University Shenzhen Graduate School, Shenzhen, 518055, China
| | - Wei Han
- State Key Laboratory of Chemical Oncogenomics, Guangdong Provincial Key Laboratory of Chemical Genomics, School of Chemical Biology and Biotechnology, Peking University Shenzhen Graduate School, Shenzhen, 518055, China
- Institute of Chemical Biology, Shenzhen Bay Laboratory, Shenzhen, 518132, China
| |
Collapse
|
6
|
Zbacnik NJ, Manning MC, Henry CS. Chemometric Study of the Relative Aggregation Propensity of Position 19
Mutants of Aβ(1-42). Curr Protein Pept Sci 2022; 23:52-60. [DOI: 10.2174/1389203723666220128105334] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2021] [Revised: 12/12/2021] [Accepted: 12/13/2021] [Indexed: 11/22/2022]
Abstract
Background:
The importance of aromaticity vs. hydrophobicity of the central hydrophobic
core (CHC, residues 17-20) in governing fibril formation in Aβ(1-42) has been the focus of an ongoing
debate in the literature.
Introduction:
Mutations in the CHC (especially at Phe19 and Phe20) have been used to examine the
relative impact of hydrophobicity and aromaticity on the degree of aggregation of Aβ(1-42). However,
the results have not been conclusive.
Methods:
Partial least squares (PLS) modeling of aggregation rates, using reduced properties of a series
of position 19 mutants, was employed to identify the physicochemical properties that had the
greatest impact on the extent of aggregation.
Results:
The PLS models indicate that hydrophobicity at position 19 of Aβ(1-42) appears to be the
primary and dominant factor in controlling Aβ(1-42) aggregation, with aromaticity having little effect.
Conclusions:
This study illustrates the value of using reduced properties of amino acids in conjunction
with PLS modeling to investigate mutational effects in peptides and proteins, as the reduced properties
can capture in a quantitative manner the different physicochemical properties of the amino acid side
chains. In this particular study, hydrophobicity at position 19 was determined to be the dominant property
controlling aggregation, while size, charge, and aromaticity had little impact.
Collapse
Affiliation(s)
| | - Mark Cornell Manning
- Legacy BioDesign LLC, Johnstown, CO 80534, USA
- Department of Chemistry, Colorado State University, Fort Collins, CO 80523, USA
| | - Charles S. Henry
- Department of Chemistry, Colorado State University, Fort Collins, CO 80523, USA
| |
Collapse
|
7
|
Kav B, Strodel B. Does the inclusion of electronic polarisability lead to a better modelling of peptide aggregation? RSC Adv 2022; 12:20829-20837. [PMID: 35919139 PMCID: PMC9301629 DOI: 10.1039/d2ra01478e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2022] [Accepted: 07/11/2022] [Indexed: 11/26/2022] Open
Abstract
Simulating the process of amyloid aggregation with atomic detail is a challenging task for various reasons. One of them is that it is difficult to parametrise a force field such that all protein states ranging from the folded through the unfolded to the aggregated state are represented with the same level of accuracy. Here, we test whether the consideration of electronic polarisability improves the description of the different states of Aβ16–22. Surprisingly, the CHARMM Drude polarisable force field is found to perform worse than its unpolarisable counterpart CHARMM36m. Sources for this failure of the Drude model are discussed. Simulating the process of amyloid aggregation is a hard task. We test whether the inclusion of electronic polarisability as done in CHARMM-Drude improves the modelling of Aβ16–22 aggregation and find it does not. Reasons for the failure are given.![]()
Collapse
Affiliation(s)
- Batuhan Kav
- Institute of Biological Information Processing: Structural Biochemistry (IBI-7), Forschungszentrum Jülich, 52428 Jülich, Germany
| | - Birgit Strodel
- Institute of Biological Information Processing: Structural Biochemistry (IBI-7), Forschungszentrum Jülich, 52428 Jülich, Germany
- Institute of Theoretical and Computational Chemistry, Heinrich Heine University Düsseldorf, 40225 Düsseldorf, Germany
| |
Collapse
|
8
|
Man VH, He X, Gao J, Wang J. Effects of All-Atom Molecular Mechanics Force Fields on Amyloid Peptide Assembly: The Case of PHF6 Peptide of Tau Protein. J Chem Theory Comput 2021; 17:6458-6471. [PMID: 34491058 DOI: 10.1021/acs.jctc.1c00028] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Molecular dynamics (MD) simulations play a vital role in revealing the mechanism of amyloid aggregation that is crucial to the therapeutic agent development for Alzheimer's Disease. However, the accuracy of MD simulation results strongly depends on the force field employed. In our previous benchmark for 17 all-atom force fields on modeling of amyloid aggregation using the Aβ16-22 dimer, we showed that AMBER14SB and CHARMM36m are suitable force fields for amyloid aggregation simulation, while GROMOS54a7 and OPLSAA are not good for the task. In this work, we continue assessing the applicability of atomistic force fields on amyloid aggregation using the VQIVYK (PHF6) peptide which is essential for tau-protein aggregation. Although, both Aβ16-22 and PHF6 peptides formed fibrils in vitro, the PHF6 fibrils are parallel β-sheets, while the Aβ16-22 fibrils are antiparallel β-sheets. We performed an all-atom large-scale MD simulation in explicit water on the PHF6 dimer and octa-peptides systems using five mainstream force fields, including AMBER99SB-disp, AMBER14SB, CHARMM36m, GROMOS54a7, and OPLSAA. The accumulated simulation time is 0.2 ms. Our result showed that the β-sheet structures of PHF6 peptides sampled by AMBER99SB-disp, AMBER14SB, GROMOS54a7, and OPLSAA are in favor of the antiparallel β-sheets, while the dominant type of β-sheet structures is parallel β-sheet by using CHARMM36m. Among the five force fields, CHARMM36m provides the strongest CH-π interaction that was observed in an NMR study. The comparison between our results and experimental observation indicates that CHARMM36m achieved the best performance on modeling the aggregation of PHF6 peptides. In summary, CHARMM36m is currently the most suitable force field for studying the aggregation of both amyloid-β and Tau through MD simulations.
Collapse
Affiliation(s)
- Viet Hoang Man
- Department of Pharmaceutical Sciences and Computational Chemical Genomics Screening Center, School of Pharmacy, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, United States
| | - Xibing He
- Department of Pharmaceutical Sciences and Computational Chemical Genomics Screening Center, School of Pharmacy, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, United States
| | - Jie Gao
- Department of Neuroscience, The Ohio State University Wexner Medical Center, Columbus, Ohio 43210, United States
| | - Junmei Wang
- Department of Pharmaceutical Sciences and Computational Chemical Genomics Screening Center, School of Pharmacy, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, United States
| |
Collapse
|
9
|
Boopathi S, Poma AB, Garduño-Juárez R. An Overview of Several Inhibitors for Alzheimer's Disease: Characterization and Failure. Int J Mol Sci 2021; 22:10798. [PMID: 34639140 PMCID: PMC8509255 DOI: 10.3390/ijms221910798] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2021] [Revised: 10/01/2021] [Accepted: 10/03/2021] [Indexed: 01/04/2023] Open
Abstract
Amyloid beta (Aβ) oligomers are the most neurotoxic aggregates causing neuronal death and cognitive damage. A detailed elucidation of the aggregation pathways from oligomers to fibril formation is crucial to develop therapeutic strategies for Alzheimer's disease (AD). Although experimental techniques rely on the measure of time- and space-average properties, they face severe difficulties in the investigation of Aβ peptide aggregation due to their intrinsically disorder character. Computer simulation is a tool that allows tracing the molecular motion of molecules; hence it complements Aβ experiments, as it allows to explore the binding mechanism between metal ions and Aβ oligomers close to the cellular membrane at the atomic resolution. In this context, integrated studies of experiments and computer simulations can assist in mapping the complete pathways of aggregation and toxicity of Aβ peptides. Aβ oligomers are disordered proteins, and due to a rapid exploration of their intrinsic conformational space in real-time, they are challenging therapeutic targets. Therefore, no good drug candidate could have been identified for clinical use. Our previous investigations identified two small molecules, M30 (2-Octahydroisoquinolin-2(1H)-ylethanamine) and Gabapentin, capable of Aβ binding and inhibiting molecular aggregation, synaptotoxicity, intracellular calcium signaling, cellular toxicity and memory losses induced by Aβ. Thus, we recommend these molecules as novel candidates to assist anti-AD drug discovery in the near future. This review discusses the most recent research investigations about the Aβ dynamics in water, close contact with cell membranes, and several therapeutic strategies to remove plaque formation.
Collapse
Affiliation(s)
- Subramanian Boopathi
- Instituto de Ciencias Físicas, Universidad Nacional Autónoma de México, Cuernavaca 62210, Mexico;
| | - Adolfo B. Poma
- Department of Biosystems and Soft Matter, Institute of Fundamental Technological Research Polish Academy of Science, Pawińskiego 5B, 02-106 Warsaw, Poland
- International Center for Research on Innovative Biobased Materials (ICRI-BioM)—International Research Agenda, Lodz University of Technology, Zeromskiego 116, 90-924 Lodz, Poland;
| | - Ramón Garduño-Juárez
- Instituto de Ciencias Físicas, Universidad Nacional Autónoma de México, Cuernavaca 62210, Mexico;
| |
Collapse
|
10
|
Strodel B. Amyloid aggregation simulations: challenges, advances and perspectives. Curr Opin Struct Biol 2020; 67:145-152. [PMID: 33279865 DOI: 10.1016/j.sbi.2020.10.019] [Citation(s) in RCA: 54] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2020] [Accepted: 10/18/2020] [Indexed: 10/22/2022]
Abstract
In amyloid aggregation diseases soluble proteins coalesce into a wide array of undesirable structures, ranging through oligomers and prefibrillar assemblies to highly ordered amyloid fibrils and plaques. Explicit-solvent all-atom molecular dynamics (MD) simulations of amyloid aggregation have been performed for almost 20 years, revealing valuable information about this phenomenon. However, these simulations are challenged by three main problems. Firstly, current force fields modeling amyloid aggregation are insufficiently accurate. Secondly, the protein concentrations in MD simulations are usually orders of magnitude higher than those used in vitro or found in vivo, which has direct consequences on the aggregates that form. Finally, the third problem is the well-known time-scale limit of MD simulations. In this review I highlight recent approaches to overcome these three limitations.
Collapse
Affiliation(s)
- Birgit Strodel
- Institute of Biological Information Processing (IBI-7: Structural Biochemistry), Forschungszentrum Jülich, 52425 Jülich, Germany; Institute of Theoretical and Computational Chemistry, Heinrich Heine University Düsseldorf, Universitätstrasse 1, 40225 Düsseldorf, Germany.
| |
Collapse
|
11
|
Samantray S, Yin F, Kav B, Strodel B. Different Force Fields Give Rise to Different Amyloid Aggregation Pathways in Molecular Dynamics Simulations. J Chem Inf Model 2020; 60:6462-6475. [DOI: 10.1021/acs.jcim.0c01063] [Citation(s) in RCA: 51] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Suman Samantray
- Institute of Biological Information Processing: Structural Biochemistry (IBI-7), Forschungszentrum Jülch, 52428 Jülich, Germany
- AICES Graduate School, RWTH Aachen University, Schinkelstraße 2, 52062 Aachen, Germany
| | - Feng Yin
- Institute of Biological Information Processing: Structural Biochemistry (IBI-7), Forschungszentrum Jülch, 52428 Jülich, Germany
| | - Batuhan Kav
- Institute of Biological Information Processing: Structural Biochemistry (IBI-7), Forschungszentrum Jülch, 52428 Jülich, Germany
| | - Birgit Strodel
- Institute of Biological Information Processing: Structural Biochemistry (IBI-7), Forschungszentrum Jülch, 52428 Jülich, Germany
- Institute of Theoretical and Computational Chemistry, Heinrich Heine University Düsseldorf, 40225 Düsseldorf, Germany
| |
Collapse
|
12
|
Yadav N, Chauhan MK, Chauhan VS. Short to ultrashort peptide-based hydrogels as a platform for biomedical applications. Biomater Sci 2019; 8:84-100. [PMID: 31696870 DOI: 10.1039/c9bm01304k] [Citation(s) in RCA: 67] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Short peptides have attracted significant attention from researchers in the past few years due to their easy design, synthesis and characterization, diverse functionalisation possibilities, low cost, possibility to make a large range of hierarchical nanostructures and most importantly their high biocompatibility and biodegradability. Generally, short peptides are also relatively more stable than their longer variants, non-immunogenic in nature and many of them self-assemble to provide an exciting range of nanostructures, including hydrogels. Thus, the development of short peptide-based hydrogels has become an area of intense investigation. Although these hydrogels have a water content of greater than 90%, they are surprisingly highly stable structures, and thus have been used for various biomedical applications, including cell therapeutics, drug delivery, tissue engineering and regeneration, contact lenses, biosensors, and wound healing, by different researchers. Herein, we review the progress of research in the rapidly expanding field of short to ultrashort peptide-based hydrogels and their possible applications. Special attention is paid to address and review this field with regard to the stability of peptide-based hydrogels, particularly to enzymatic degradation.
Collapse
Affiliation(s)
- Nitin Yadav
- Molecular Medicine Group, International Centre for Genetic Engineering & Biotechnology, Aruna Asaf Ali Marg, New Delhi-110067, India. and Delhi Institute of Pharmaceutical Sciences and Research, Mehrauli-Badarpur Road, Sector-3, Pushpvihar, New Delhi-110017, India
| | - Meenakshi K Chauhan
- Delhi Institute of Pharmaceutical Sciences and Research, Mehrauli-Badarpur Road, Sector-3, Pushpvihar, New Delhi-110017, India
| | - Virander S Chauhan
- Molecular Medicine Group, International Centre for Genetic Engineering & Biotechnology, Aruna Asaf Ali Marg, New Delhi-110067, India.
| |
Collapse
|
13
|
Zbacnik NJ, Henry CS, Manning MC. A Chemometric Approach Toward Predicting the Relative Aggregation Propensity: Aβ(1-42). J Pharm Sci 2019; 109:624-632. [PMID: 31606543 DOI: 10.1016/j.xphs.2019.10.014] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2019] [Revised: 10/04/2019] [Accepted: 10/08/2019] [Indexed: 01/19/2023]
Abstract
A number of algorithms have been developed to predict the aggregation propensity of peptides and proteins, but virtually none have the ability to provide sequence-specific information on what physicochemical properties are most important in altering aggregation propensity. In this study, a chemometric approach using reduced amino acid properties is used to examine the aggregation behavior of a highly amyloidogenic peptide, Aβ(1-42). Specific residues are identified as being critical to the aggregation process. At each of these positions, the important physicochemical properties are identified that would either accelerate or inhibit fibril formation.
Collapse
Affiliation(s)
| | - Charles S Henry
- Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523
| | - Mark Cornell Manning
- Legacy BioDesign LLC, Johnstown, Colorado 80534; Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523.
| |
Collapse
|
14
|
Urban JM, Ho J, Piester G, Fu R, Nilsson BL. Rippled β-Sheet Formation by an Amyloid-β Fragment Indicates Expanded Scope of Sequence Space for Enantiomeric β-Sheet Peptide Coassembly. Molecules 2019; 24:E1983. [PMID: 31126069 PMCID: PMC6571685 DOI: 10.3390/molecules24101983] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2019] [Revised: 05/10/2019] [Accepted: 05/22/2019] [Indexed: 11/30/2022] Open
Abstract
In 1953, Pauling and Corey predicted that enantiomeric β-sheet peptides would coassemble into so-called "rippled" β-sheets, in which the β-sheets would consist of alternating l- and d-peptides. To date, this phenomenon has been investigated primarily with amphipathic peptide sequences composed of alternating hydrophilic and hydrophobic amino acid residues. Here, we show that enantiomers of a fragment of the amyloid-β (Aβ) peptide that does not follow this sequence pattern, amyloid-β (16-22), readily coassembles into rippled β-sheets. Equimolar mixtures of enantiomeric amyloid-β (16-22) peptides assemble into supramolecular structures that exhibit distinct morphologies from those observed by self-assembly of the single enantiomer pleated β-sheet fibrils. Formation of rippled β-sheets composed of alternating l- and d-amyloid-β (16-22) is confirmed by isotope-edited infrared spectroscopy and solid-state NMR spectroscopy. Sedimentation analysis reveals that rippled β-sheet formation by l- and d-amyloid-β (16-22) is energetically favorable relative to self-assembly into corresponding pleated β-sheets. This work illustrates that coassembly of enantiomeric β-sheet peptides into rippled β-sheets is not limited to peptides with alternating hydrophobic/hydrophilic sequence patterns, but that a broader range of sequence space is available for the design and preparation of rippled β-sheet materials.
Collapse
Affiliation(s)
- Jennifer M Urban
- Department of Chemistry, University of Rochester, Rochester, NY 14627-0216, USA.
| | - Janson Ho
- Department of Chemistry, University of Rochester, Rochester, NY 14627-0216, USA.
| | - Gavin Piester
- Department of Chemistry, University of Rochester, Rochester, NY 14627-0216, USA.
| | - Riqiang Fu
- The National High Magnetic Field Laboratory, Florida State University, 1800 East Paul Dirac Drive, Tallahassee, FL 32310, USA.
| | - Bradley L Nilsson
- Department of Chemistry, University of Rochester, Rochester, NY 14627-0216, USA.
| |
Collapse
|
15
|
Mahmoudinobar F, Urban JM, Su Z, Nilsson BL, Dias CL. Thermodynamic Stability of Polar and Nonpolar Amyloid Fibrils. J Chem Theory Comput 2019; 15:3868-3874. [DOI: 10.1021/acs.jctc.9b00145] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Farbod Mahmoudinobar
- Department of Physics, New Jersey Institute of Technology, Newark, New Jersey 07102, United States
| | - Jennifer M. Urban
- Department of Chemistry, University of Rochester, Rochester, New York 14627, United States
| | - Zhaoqian Su
- Department of Systems and Computational Biology, Albert Einstein College of Medicine, Bronx, New York 10461, United States
| | - Bradley L. Nilsson
- Department of Chemistry, University of Rochester, Rochester, New York 14627, United States
| | - Cristiano L. Dias
- Department of Physics, New Jersey Institute of Technology, Newark, New Jersey 07102, United States
| |
Collapse
|
16
|
Carballo-Pacheco M, Ismail AE, Strodel B. On the Applicability of Force Fields To Study the Aggregation of Amyloidogenic Peptides Using Molecular Dynamics Simulations. J Chem Theory Comput 2018; 14:6063-6075. [PMID: 30336669 DOI: 10.1021/acs.jctc.8b00579] [Citation(s) in RCA: 60] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Molecular dynamics simulations play an essential role in understanding biomolecular processes such as protein aggregation at temporal and spatial resolutions which are not attainable by experimental methods. For a correct modeling of protein aggregation, force fields must accurately represent molecular interactions. Here, we study the effect of five different force fields on the oligomer formation of Alzheimer's Aβ16-22 peptide and two of its mutants: Aβ16-22(F19V,F20V), which does not form fibrils, and Aβ16-22(F19L) which forms fibrils faster than the wild type. We observe that while oligomer formation kinetics depends strongly on the force field, structural properties, such as the most relevant protein-protein contacts, are similar between them. The oligomer formation kinetics obtained with different force fields differ more from each other than the kinetics between aggregating and nonaggregating peptides simulated with a single force field. We discuss the difficulties in comparing atomistic simulations of amyloid oligomer formation with experimental observables.
Collapse
Affiliation(s)
- Martín Carballo-Pacheco
- Institute of Complex Systems: Structural Biochemistry (ICS-6) , Forschungszentrum Jülich GmbH , 52425 Jülich , Germany.,AICES Graduate School , RWTH Aachen University , Schinkelstraße 2 , 52062 Aachen , Germany
| | - Ahmed E Ismail
- AICES Graduate School , RWTH Aachen University , Schinkelstraße 2 , 52062 Aachen , Germany.,Aachener Verfahrenstechnik, Faculty of Mechanical Engineering , RWTH Aachen University , Schinkelstraße 2 , 52062 Aachen , Germany
| | - Birgit Strodel
- Institute of Complex Systems: Structural Biochemistry (ICS-6) , Forschungszentrum Jülich GmbH , 52425 Jülich , Germany.,Institute of Theoretical and Computational Chemistry , Heinrich Heine University Düsseldorf , Universitätstrasse 1 , 40225 Düsseldorf , Germany
| |
Collapse
|
17
|
Betush RJ, Urban JM, Nilsson BL. Balancing hydrophobicity and sequence pattern to influence self-assembly of amphipathic peptides. Biopolymers 2018; 110. [PMID: 29292825 DOI: 10.1002/bip.23099] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2017] [Revised: 12/01/2017] [Accepted: 12/04/2017] [Indexed: 01/25/2023]
Abstract
Amphipathic peptides with alternating polar and nonpolar amino acid sequences efficiently self-assemble into functional β-sheet fibrils as long as the nonpolar residues have sufficient hydrophobicity. For example, the Ac-(FKFE)2 -NH2 peptide rapidly self-assembles into β-sheet bilayer nanoribbons, while Ac-(AKAE)2 -NH2 fails to self-assemble under similar conditions due to the significantly reduced hydrophobicity and β-sheet propensity of Ala relative to Phe. Herein, we systematically explore the effect of substituting only two of the four Ala residues at various positions in the Ac-(AKAE)2 -NH2 peptide with amino acids of increasing hydrophobicity, β-sheet potential, and surface area (including Phe, 1-naphthylalanine (1-Nal), 2-naphthylalanine (2-Nal), cyclohexylalanine (Cha), and pentafluorophenylalanine (F5 -Phe)) on the self-assembly propensity of the resulting sequences. It was found that double Phe variants, regardless of the position of substitution, failed to self-assemble under the conditions used in this study. In contrast, all double 1-Nal and 2-Nal variants readily self-assembled, albeit at differing rates depending on the substitution patterns. To determine whether this was due to hydrophobicity or side chain surface area, we also prepared double Cha and F5 -Phe variant peptides (both side chain groups are more hydrophobic than Phe). Each of these variants also underwent effective self-assembly, with the aromatic F5 -Phe peptides doing so with greater efficiency. These findings provide insight into the role of amino acid hydrophobicity and sequence pattern on self-assembly proclivity of amphipathic peptides and on how targeted substitutions of nonpolar residues in these sequences can be exploited to tune the characteristics of the resulting self-assembled materials.
Collapse
Affiliation(s)
- Ria J Betush
- Department of Chemistry, Gannon University, Erie, Pennsylvania
| | - Jennifer M Urban
- Department of Chemistry, University of Rochester, Rochester, New York
| | - Bradley L Nilsson
- Department of Chemistry, University of Rochester, Rochester, New York
| |
Collapse
|
18
|
Ozgur B, Sayar M. Role of Hydrophobic/Aromatic Residues on the Stability of Double-Wall β-Sheet Structures Formed by a Triblock Peptide. J Phys Chem B 2017; 121:4115-4128. [PMID: 28399374 DOI: 10.1021/acs.jpcb.7b00650] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Bioinspired self-assembling peptides serve as powerful building blocks in the manufacturing of nanomaterials with tailored features. Because of their ease of synthesis, biocompatibility, and tunable activity, this emerging branch of biomolecules has become very popular. The triblock peptide architecture designed by the Hartgerink group is a versatile system that allows control over its assembly and has been shown to demonstrate tunable bioactivity. Three main forces, Coulomb repulsion, hydrogen bonding and hydrophobicity act together to guide the triblock peptides' assembly into one-dimensional objects and hydrogels. It was shown previously that both the nanofiber morphology (e.g., intersheet spacing, formation of antiparallel/parallel β-sheets) and hydrogel rheology strictly depend on the choice of the core residue where the triblock peptide fibers with aromatic cores in general form shorter fibers and yield poor hydrogels with respect to the ones with aliphatic cores. However, an elaborate understanding of the molecular reasons behind these changes remained unclear. In this study, by using carefully designed computer based free energy calculations, we analyzed the influence of the core residue on the formation of double-wall fibers and single-wall β-sheets. Our results demonstrate that the aromatic substitution impairs the fiber cores and this impairment is mainly associated with a reduced hydrophobic character of the aromatic side chains. Such weakening is most obvious in tryptophan containing peptides where the fiber core absorbs a significant amount of water. We also show that the ability of tyrosine to form side chain hydrogen bonds plays an indispensable role in the fiber stability. As opposed to the impairment of the fiber cores, single-wall β-sheets with aromatic faces become more stable compared to the ones with aliphatic faces suggesting that the choice of the core residue can also affect the underlying assembly mechanism. We also provide an in-depth comparison of competing structures (zero-dimensional aggregates, short and long fibers) in the triblock peptides' assembly and show that by adjusting the length of the terminal blocks, the fiber growth can be turned on or off while keeping the nanofiber morphology intact.
Collapse
Affiliation(s)
| | - Mehmet Sayar
- College of Engineering, Koc University , Istanbul, Turkey.,Chemical & Biological Engineering and Mechanical Engineering Departments, Koc University , Istanbul, Turkey
| |
Collapse
|
19
|
Shuaib S, Goyal B. Scrutiny of the mechanism of small molecule inhibitor preventing conformational transition of amyloid-β 42 monomer: insights from molecular dynamics simulations. J Biomol Struct Dyn 2017; 36:663-678. [PMID: 28162045 DOI: 10.1080/07391102.2017.1291363] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/09/2023]
Abstract
Alzheimer's disease (AD) is a progressive neurodegenerative disorder that is characterized by loss of intellectual functioning of brain and memory loss. According to amyloid cascade hypothesis, aggregation of amyloid-β42 (Aβ42) peptide can generate toxic oligomers and their accumulation in the brain is responsible for the onset of AD. In spite of carrying out a large number of experimental studies on inhibition of Aβ42 aggregation by small molecules, the detailed inhibitory mechanism remains elusive. In the present study, comparable molecular dynamics (MD) simulations were performed to elucidate the inhibitory mechanism of a sulfonamide inhibitor C1 (2,5-dichloro-N-(4-piperidinophenyl)-3-thiophenesulfonamide), reported for its in vitro and in vivo anti-aggregation activity against Aβ42. MD simulations reveal that C1 stabilizes native α-helix conformation of Aβ42 by interacting with key residues in the central helix region (13-26) with hydrogen bonds and π-π interactions. C1 lowers the solvent-accessible surface area of the central hydrophobic core (CHC), KLVFF (16-20), that confirms burial of hydrophobic residues leading to the dominance of helical conformation in the CHC region. The binding free energy analysis with MM-PBSA demonstrates that Ala2, Phe4, Tyr10, Gln15, Lys16, Leu17, Val18, Phe19, Phe20, Glu22, and Met35 contribute maximum to binding free energy (-43.1 kcal/mol) between C1 and Aβ42 monomer. Overall, MD simulations reveal that C1 inhibits Aβ42 aggregation by stabilizing native helical conformation and inhibiting the formation of aggregation-prone β-sheet conformation. The present results will shed light on the underlying inhibitory mechanism of small molecules that show potential in vitro anti-aggregation activity against Aβ42.
Collapse
Affiliation(s)
- Suniba Shuaib
- a Department of Chemistry , School of Basic and Applied Sciences, Sri Guru Granth Sahib World University , Fatehgarh Sahib 140406 , Punjab , India
| | - Bhupesh Goyal
- a Department of Chemistry , School of Basic and Applied Sciences, Sri Guru Granth Sahib World University , Fatehgarh Sahib 140406 , Punjab , India
| |
Collapse
|
20
|
Wang J, Tao K, Zhou P, Pambou E, Li Z, Xu H, Rogers S, King S, Lu JR. Tuning self-assembled morphology of the Aβ(16-22) peptide by substitution of phenylalanine residues. Colloids Surf B Biointerfaces 2016; 147:116-123. [PMID: 27497075 DOI: 10.1016/j.colsurfb.2016.07.052] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2016] [Revised: 07/27/2016] [Accepted: 07/28/2016] [Indexed: 11/25/2022]
Abstract
The effects of the two phenylalanine (Phe) residues in the blocked Aβ(16-22) peptide on its self-assembly have been investigated by replacing both of them with two cyclohexylalanines (Chas) or two phenylglycines (Phgs). TEM and SANS studies revealed that the flat and wide nanoribbons of Aβ(16-22) were transformed into thin nanotubes when replaced with Chas, and thinner and twisted nanofibrils when replaced with Phgs. The red-shifting degree of characteristic CD peaks suggested an increased twisting in the self-assembly of the derivative peptides, especially in the case of Ac-KLV(Phg)(Phg)AE-NH2. Furthermore, molecular dynamics (MD) simulations also indicated the increasing trend in twisting when Chas or Phgs were substituted for Phes. These results demonstrated that the hydrophobic interactions and spatial conformation between Cha residues were sufficient to cause lateral association of β-sheets to twisted/helical nanoribbons, which finally developed into nanotubes, while for Phg residue, the loss of the rotational freedom of the aromatic ring induced much stronger steric hindrance for the lateral stacking of Ac-KLV(Phg)(Phg)AE-NH2 β-sheets, eventually leading to the nanofibril formation. This study thus demonstrates that both the aromatic structure and the steric conformation of Phe residues are crucial in Aβ(16-22) self-assembly, especially in the significant lateral association of β-sheets.
Collapse
Affiliation(s)
- Jiqian Wang
- Centre for Bioengineering and Biotechnology, China University of Petroleum (East China), Qingdao 266580, China.
| | - Kai Tao
- Centre for Bioengineering and Biotechnology, China University of Petroleum (East China), Qingdao 266580, China
| | - Peng Zhou
- Centre for Bioengineering and Biotechnology, China University of Petroleum (East China), Qingdao 266580, China
| | - Elias Pambou
- Biological Physics Group, School of Physics and Astronomy, University of Manchester, Schuster Building, Oxford Road, Manchester M13 9PL, United Kingdom
| | - Zongyi Li
- Biological Physics Group, School of Physics and Astronomy, University of Manchester, Schuster Building, Oxford Road, Manchester M13 9PL, United Kingdom
| | - Hai Xu
- Centre for Bioengineering and Biotechnology, China University of Petroleum (East China), Qingdao 266580, China.
| | - Sarah Rogers
- ISIS Pulsed Neutron Source, Rutherford Appleton Laboratory, Didcot, Oxon OX11 0QZ, United Kingdom
| | - Stephen King
- ISIS Pulsed Neutron Source, Rutherford Appleton Laboratory, Didcot, Oxon OX11 0QZ, United Kingdom
| | - Jian R Lu
- Biological Physics Group, School of Physics and Astronomy, University of Manchester, Schuster Building, Oxford Road, Manchester M13 9PL, United Kingdom
| |
Collapse
|
21
|
Abstract
As methods to incorporate noncanonical amino acid residues into proteins have become more powerful, interest in their use to modify the physical and biological properties of proteins and enzymes has increased. This chapter discusses the use of highly fluorinated analogs of hydrophobic amino acids, for example, hexafluoroleucine, in protein design. In particular, fluorinated residues have proven to be generally effective in increasing the thermodynamic stability of proteins. The chapter provides an overview of the different fluorinated amino acids that have been used in protein design and the various methods available for producing fluorinated proteins. It discusses model proteins systems into which highly fluorinated amino acids have been introduced and the reasons why fluorinated residues are generally stabilizing, with particular reference to thermodynamic and structural studies from our laboratory. Lastly, details of the methodology we have developed to measure the thermodynamic stability of oligomeric fluorinated proteins are presented, as this may be generally applicable to many proteins.
Collapse
Affiliation(s)
- E N G Marsh
- University of Michigan, Ann Arbor, MI, United States.
| |
Collapse
|
22
|
Lee NR, Bowerman CJ, Nilsson BL. Sequence length determinants for self-assembly of amphipathic β-sheet peptides. Biopolymers 2016; 100:738-50. [PMID: 23553562 DOI: 10.1002/bip.22248] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2012] [Revised: 03/18/2013] [Accepted: 03/22/2013] [Indexed: 12/29/2022]
Abstract
Amphipathic peptides composed of alternating hydrophobic and hydrophilic amino acids are a privileged class of peptide, which have a high propensity to self-assemble into β-sheet fibrils. The Ac-(FKFE)2-NH2 peptide has been extensively studied and forms putative β-sheet bilayer fibrils in which the hydrophobic Phe side chains are organized to a single face of each constituent sheet; upon bilayer formation, these hydrophobic benzyl groups are sequestered in the hydrophobic core of the resulting fibril. In order for the Phe side chains to be uniformly displayed on one face of Ac-(FKFE)2-NH2 β-sheets, an antiparallel packing orientation in which one amino acid residue is unpaired must be adopted. Based on molecular models, we hypothesized that truncated seven amino acid derivatives of Ac-(FKFE)2-NH2 in which either the N-terminal Phe residue (Ac-KFEFKFE-NH2) or the C-terminal Glu residue (Ac-FKFEFKF-NH2) is eliminated should readily self-assemble into β-sheet bilayers in which all hydrogen bond and hydrophobic/charge interactions are satisfied. We found, however, that these minute changes in peptide sequence have unanticipated and dramatic effects on the self-assembly of each peptide. Ac-FKFEFKF-NH2 self-assembled into fibrils with unique morphology relative to the parent peptide, whereas the Ac-KFEFKFE-NH2 peptide had a strongly reduced propensity to self-assemble, even failing to self-assemble altogether under some conditions. These findings provide significant insight into the effect of sequence length and strand registry as well as hydrophobicity and charge on the self-assembly of simple amphipathic peptides to illuminate the possibility of tuning self-assembly processes and the resulting structures with minute changes to peptide sequence.
Collapse
Affiliation(s)
- Naomi R Lee
- Department of Chemistry, University of Rochester, Rochester, NY, 14627-0216
| | | | | |
Collapse
|
23
|
Pachahara SK, Nagaraj R. Probing the role of aromatic residues in the self-assembly of Aβ(16-22) in fluorinated alcohols and their aqueous mixtures. Biochem Biophys Rep 2015; 2:1-13. [PMID: 29124140 PMCID: PMC5668628 DOI: 10.1016/j.bbrep.2015.04.005] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2015] [Revised: 04/16/2015] [Accepted: 04/17/2015] [Indexed: 11/19/2022] Open
Abstract
The Aβ(16–22) sequence KLVFFAE spans the hydrophobic core of the Aβ peptide and plays an important role in its self-assembly. Apart from forming amyloid fibrils, Aβ(16–22) can self-associate into highly ordered nanotubes and ribbon-like structures depending on the composition of solvent used for dissolution. The Aβ(16–22) sequence which has FF at the 19th and 20th positions would be a good model to investigate peptide self-assembly in the context of aromatic interactions. In this study, self-assembly of Aβ(16–22) and its aromatic analogs obtained by replacement of F19, F20 or both by Y or W was examined after dissolution in fluorinated alcohols and their aqueous mixtures in solvent cluster forming conditions. The results indicate that the presence of aromatic residues Y and W and their position in the sequence plays an important role in self-assembly. We observe the formation of amyloid fibrils and other self-assembled structures such as spheres, rings and beads. Our results indicate that 20% HFIP is more favourable for amyloid fibril formation as compared to 20% TFE, when F is replaced with Y or W. The dissolution of peptides in DMSO followed by evaporation of solvent and dissolution in water appears to greatly influence peptide conformation, morphology and cross-β content of self-assembled structures. Our study shows that positioning of aromatic residues F, Y and W have an important role in directing self-assembly of the peptides. Effect of fluorinated alcohols on the aggregation of Aβ(16–22) and analogs was investigated. Replacement of F by Y and W in the Aβ(16–22) sequence modulates self-assembly. Positions of F, Y, W in Aβ(16–22) plays an important role in self-assembly.
Collapse
|
24
|
Smith JE, Liang C, Tseng M, Li N, Li S, Mowles AK, Mehta AK, Lynn DG. Defining the Dynamic Conformational Networks of Cross-β Peptide Assembly. Isr J Chem 2015. [DOI: 10.1002/ijch.201500012] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
|
25
|
Ow SY, Bekard I, Blencowe A, Qiao GG, Dunstan DE. A generic class of amyloid fibril inhibitors. J Mater Chem B 2015; 3:1350-1359. [DOI: 10.1039/c4tb01762e] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Amyloid fibrils are large ordered fibrillar aggregates formed from mis-folded proteins. Fibril formation is inhibited using a generic macromolecular structure.
Collapse
Affiliation(s)
- Sian-Yang Ow
- Department of Chemical and Biomolecular Engineering
- The University of Melbourne
- Australia
| | - Innocent Bekard
- Department of Chemical and Biomolecular Engineering
- The University of Melbourne
- Australia
| | - Anton Blencowe
- Department of Chemical and Biomolecular Engineering
- The University of Melbourne
- Australia
- Mawson Institute
- Division of ITEE
| | - Greg G. Qiao
- Department of Chemical and Biomolecular Engineering
- The University of Melbourne
- Australia
| | - Dave E. Dunstan
- Department of Chemical and Biomolecular Engineering
- The University of Melbourne
- Australia
| |
Collapse
|
26
|
Xie L, Lin D, Luo Y, Li H, Yang X, Wei G. Effects of hydroxylated carbon nanotubes on the aggregation of Aβ16-22 peptides: a combined simulation and experimental study. Biophys J 2014; 107:1930-1938. [PMID: 25418174 PMCID: PMC4213673 DOI: 10.1016/j.bpj.2014.08.034] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2014] [Revised: 07/27/2014] [Accepted: 08/21/2014] [Indexed: 11/19/2022] Open
Abstract
The pathogenesis of Alzheimer's disease (AD) is associated with the aggregation of amyloid-β (Aβ) peptides into toxic aggregates with ?-sheet character. In a previous computational study, we showed that pristine single-walled carbon nanotubes (SWCNTs) can inhibit the formation of β-sheet-rich oligomers in the central hydrophobic core fragment of Aβ (Aβ16-22). However, the poor solubility of SWCNTs in water hinders their use in biomedical applications and nanomedicine. Here, we investigate the influence of hydroxylated SWCNT, a water-soluble SWCNT derivative, on the aggregation of Aβ16-22 peptides using all-atom explicit-water replica exchange molecular dynamics simulations. Our results show that hydroxylated SWCNTs can significantly inhibit β-sheet formation and shift the conformations of Aβ16-22 oligomers from ordered β-sheet-rich structures toward disordered coil aggregates. Detailed analyses of the SWCNT-Aβ interaction reveal that the inhibition of β-sheet formation by hydroxylated SWCNTs mainly results from strong electrostatic interactions between the hydroxyl groups of SWCNTs and the positively charged residue K16 of Aβ16-22 and hydrophobic and aromatic stacking interactions between SWCNTs and F19 and F20. In addition, our atomic force microscopy and thioflavin T fluorescence experiments confirm the inhibitory effect of both pristine and hydroxylated SWCNTs on Aβ16-22 fibrillization, in support of our previous and present replica exchange molecular dynamics simulation results. These results demonstrate that hydroxylated SWCNTs efficiently inhibit the aggregation of Aβ16-22; in addition, they offer molecular insight into the inhibition mechanism, thus providing new clues for the design of therapeutic drugs against amyloidosis.
Collapse
Affiliation(s)
- Luogang Xie
- State Key Laboratory of Surface Physics, Key Laboratory for Computational Physical Sciences (Ministry of Education), and Department of Physics, Fudan University, Shanghai, China
| | - Dongdong Lin
- State Key Laboratory of Surface Physics, Key Laboratory for Computational Physical Sciences (Ministry of Education), and Department of Physics, Fudan University, Shanghai, China
| | - Yin Luo
- State Key Laboratory of Surface Physics, Key Laboratory for Computational Physical Sciences (Ministry of Education), and Department of Physics, Fudan University, Shanghai, China
| | - Huiyu Li
- Department of Mathematics and Physics, Shanghai University of Electric Power, Shanghai, China
| | - Xinju Yang
- State Key Laboratory of Surface Physics, Key Laboratory for Computational Physical Sciences (Ministry of Education), and Department of Physics, Fudan University, Shanghai, China
| | - Guanghong Wei
- State Key Laboratory of Surface Physics, Key Laboratory for Computational Physical Sciences (Ministry of Education), and Department of Physics, Fudan University, Shanghai, China.
| |
Collapse
|
27
|
Berhanu WM, Hansmann UHE. Stability of amyloid oligomers. ADVANCES IN PROTEIN CHEMISTRY AND STRUCTURAL BIOLOGY 2014; 96:113-41. [PMID: 25443956 DOI: 10.1016/bs.apcsb.2014.06.006] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/12/2023]
Abstract
Molecular simulations are now commonly used to complement experimental techniques in investigating amyloids and their role in human diseases. In this chapter, we will summarize techniques and approaches often used in amyloid simulations and will present recent success stories. Our examples will be focused on lessons learned from molecular dynamics simulations in aqueous environments that start from preformed aggregates. These studies explore the limitations that arise from the choice of force field, the role of mutations in the growth of amyloid aggregates, segmental polymorphism, and the importance of cross-seeding. Furthermore, they give evidence for potential toxicity mechanisms. We finally discuss the role of molecular simulations in the search for aggregation inhibitors.
Collapse
Affiliation(s)
- Workalemahu M Berhanu
- Department of Chemistry & Biochemistry, University of Oklahoma, Norman, Oklahoma, USA
| | - Ulrich H E Hansmann
- Department of Chemistry & Biochemistry, University of Oklahoma, Norman, Oklahoma, USA.
| |
Collapse
|
28
|
Pham JD, Spencer RK, Chen KH, Nowick JS. A fibril-like assembly of oligomers of a peptide derived from β-amyloid. J Am Chem Soc 2014; 136:12682-90. [PMID: 25068693 PMCID: PMC4183627 DOI: 10.1021/ja505713y] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
![]()
A macrocyclic
β-sheet peptide containing two nonapeptide
segments based on Aβ15–23 (QKLVFFAED) forms
fibril-like assemblies of oligomers in the solid state. The X-ray
crystallographic structure of macrocyclic β-sheet peptide 3 was determined at 1.75 Å resolution. The macrocycle
forms hydrogen-bonded dimers, which further assemble along the fibril
axis in a fashion resembling a herringbone pattern. The extended β-sheet
comprising the dimers is laminated against a second layer of dimers
through hydrophobic interactions to form a fibril-like assembly that
runs the length of the crystal lattice. The second layer is offset
by one monomer subunit, so that the fibril-like assembly is composed
of partially overlapping dimers, rather than discrete tetramers. In
aqueous solution, macrocyclic β-sheet 3 and homologues 4 and 5 form discrete tetramers, rather than
extended fibril-like assemblies. The fibril-like assemblies of oligomers
formed in the solid state by macrocyclic β-sheet 3 represent a new mode of supramolecular assembly not previously observed
for the amyloidogenic central region of Aβ. The structures observed
at atomic resolution for this peptide model system may offer insights
into the structures of oligomers and oligomer assemblies formed by
full-length Aβ and may provide a window into the propagation
and replication of amyloid oligomers.
Collapse
Affiliation(s)
- Johnny D Pham
- Department of Chemistry, University of California, Irvine , Irvine, California 92697-2025, United States
| | | | | | | |
Collapse
|
29
|
Ow SY, Dunstan DE. A brief overview of amyloids and Alzheimer's disease. Protein Sci 2014; 23:1315-31. [PMID: 25042050 DOI: 10.1002/pro.2524] [Citation(s) in RCA: 96] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2014] [Revised: 07/10/2014] [Accepted: 07/11/2014] [Indexed: 01/29/2023]
Abstract
Amyloid fibrils are self-assembled fibrous protein aggregates that are associated with a number of presently incurable diseases such as Alzheimer's and Parkinson's disease. Millions of people worldwide suffer from amyloid diseases. This review summarizes the unique cross-β structure of amyloid fibrils, morphological variations, the kinetics of amyloid fibril formation, and the cytotoxic effects of these fibrils and oligomers. Alzheimer's disease is also explored as an example of an amyloid disease to show the various approaches to treat these amyloid diseases. Finally, this review investigates the nanotechnological and biological applications of amyloid fibrils; as well as a summary of the typical biological pathways involved in the disposal of amyloid fibrils and their precursors.
Collapse
Affiliation(s)
- Sian-Yang Ow
- Department of Chemical and Biomolecular Engineering, University of Melbourne, Melbourne, Victoria, Australia
| | | |
Collapse
|
30
|
Saini A, Chauhan VS. Self-assembling properties of peptides derived from TDP-43 C-terminal fragment. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2014; 30:3845-3856. [PMID: 24559403 DOI: 10.1021/la404710w] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Two highly fibrillogenic peptide sequences (MNFGAFSINP and EDLIIKGISV) were previously reported in the C-terminal fragment (CTF) of TDP-43 (220-414), a protein recently implicated in neuro-degenerative diseases such as amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD-U). It was observed that the sequences MNFGAFS and EDLIIKG harbor their respective fibrillogenic domains. Here, the self-assembling properties of peptides obtained by systematic deletion of residues from these two sequences were investigated with the help of light scattering, thioflavin T fluorescence, transmission electron microscopy, and circular dichroism spectroscopy. It was found that the pentapeptide NFGAF and the tetrapeptide DLII are the shortest fibrillogenic sequences from MNFGAFS and EDLIIKG, respectively. Structure function studies revealed that self-assembly of the peptides is largely governed by hydrophobic interactions. Both NFGAF and DLII formed hydrogels based on a complex fibrillar network, at relatively low concentrations, and of remarkable strength and stability. Of particular interest was DLII, a rare aliphatic tetrapeptide that formed a hydrogel at a concentration of 1 mg/mL in less than an hour. Interestingly, various other tetrapeptides based on DLII (YLII, KLII, NLII, and LIID) also formed hydrogels of comparable physical properties, suggesting that an amphipathic peptide design based on the hydrophobic LII motif and a single residue polar terminus is highly favorable for hydrogelation. Peptides discovered in this study, especially DLII and its variants, are some of the shortest ever reported to show such structural and functional features, suggesting that they can be useful templates for the design of peptide-based soft materials.
Collapse
Affiliation(s)
- Akash Saini
- International Centre for Genetic Engineering and Biotechnology, Aruna Asaf Ali Marg, New Delhi 110067, India
| | | |
Collapse
|
31
|
Preston GW, Radford SE, Ashcroft AE, Wilson AJ. Analysis of amyloid nanostructures using photo-cross-linking: in situ comparison of three widely used photo-cross-linkers. ACS Chem Biol 2014; 9:761-8. [PMID: 24372480 PMCID: PMC3964826 DOI: 10.1021/cb400731s] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Photoinduced cross-linking (PIC) has become a powerful tool in chemical biology for the identification and mapping of stable or transient interactions between biomacromolecules and their (unknown) ligands. However, the value of PIC for in vitro and in vivo structural proteomics can be realized only if cross-linking reports accurately on biomacromolecule secondary, tertiary, and quaternary structures with residue-specific resolution. Progress in this area requires rigorous and comparative studies of PIC reagents, but despite widespread use of PIC, these have rarely been performed. The use of PIC to report reliably on noncovalent structure is therefore limited, and its potentials have yet to be fully realized. In the present study, we compared the abilities of three probes, phenyl trifluoromethyldiazirine (TFMD), benzophenone (BP), and phenylazide (PA), to record structural information within a biomolecular complex. For this purpose, we employed a self-assembled amyloid-like peptide nanostructure as a tightly and specifically packed model environment in which to photolyze the reagents. Information about PIC products was gathered using mass spectrometry and ion mobility spectrometry, and the data were interpreted using a mechanism-oriented approach. While all three PIC groups appeared to generate information within the packed peptide environment, the data highlight technical limitations of BP and PA. On the other hand, TFMD displayed accuracy and generated straightforward results. Thus TFMD, with its robust and rapid photochemistry, was shown to be an ideal probe for cross-linking of peptide nanostructures. The implications of our findings for detailed analyses of complex systems, including those that are transiently populated, are discussed.
Collapse
Affiliation(s)
- George W. Preston
- School
of Chemistry, ‡Astbury Centre for Structural Molecular Biology, and §School of Molecular and Cellular Biology,
Faculty of Biological Sciences, University of Leeds, Woodhouse Lane, Leeds LS2 9JT, United Kingdom
| | - Sheena E. Radford
- School
of Chemistry, ‡Astbury Centre for Structural Molecular Biology, and §School of Molecular and Cellular Biology,
Faculty of Biological Sciences, University of Leeds, Woodhouse Lane, Leeds LS2 9JT, United Kingdom
| | - Alison. E. Ashcroft
- School
of Chemistry, ‡Astbury Centre for Structural Molecular Biology, and §School of Molecular and Cellular Biology,
Faculty of Biological Sciences, University of Leeds, Woodhouse Lane, Leeds LS2 9JT, United Kingdom
| | - Andrew J. Wilson
- School
of Chemistry, ‡Astbury Centre for Structural Molecular Biology, and §School of Molecular and Cellular Biology,
Faculty of Biological Sciences, University of Leeds, Woodhouse Lane, Leeds LS2 9JT, United Kingdom
| |
Collapse
|
32
|
Markiewicz BN, Oyola R, Du D, Gai F. Aggregation gatekeeper and controlled assembly of Trpzip β-hairpins. Biochemistry 2014; 53:1146-54. [PMID: 24498924 PMCID: PMC3985754 DOI: 10.1021/bi401568a] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Protein and peptide aggregation is an important issue both in vivo and in vitro. Herein, we examine the aggregation behaviors of two well-studied β-hairpins, Trpzip1 and Trpzip2. Previous studies suggested that Trpzip2 remains monomeric up to a concentration of ~15 mM whereas Trpzip1 readily aggregates at micromolar concentrations at acidic or neutral pH. This disparity is puzzling considering that these two peptides differ only in their turn sequences (i.e., GN vs NG). We hypothesize that these peptides can aggregate from their folded states via native edge-to-edge interactions and that the Lys8 residue in Trpzip2 is a more effective aggregation gatekeeper, because of a more favorable orientation. In support of this hypothesis, we find that increasing the pH to 13 or replacing Lys8 with a hydrophobic and photolabile Lys analogue, Lys(nvoc), leads to a significant increase in the aggregation propensity of Trpzip2, and that the aggregation of this Trpzip2 mutant can be reversed upon restoring the native Lys side chain via photocleavage of the nvoc moiety. In addition, we find that while both Trpzip1 and Trpzip2 form parallel β-sheet aggregates, the Lys(nvoc) Trpzip2 mutant forms antiparallel β-sheets and more stable fibrils. Taken together, these findings provide another example showing how sensitive peptide and protein aggregation is to minor sequence variation and that it is possible to use a photolabile non-natural amino acid, such as Lys(nvoc), to tune the rate of peptide aggregation and to control fibrillar structure.
Collapse
Affiliation(s)
- Beatrice N Markiewicz
- Department of Chemistry, University of Pennsylvania , Philadelphia, Pennsylvania 19104, United States
| | | | | | | |
Collapse
|
33
|
Abstract
Highly fluorinated analogs of hydrophobic amino acids have proven to be generally effective in increasing the thermodynamic stability of proteins. These non-proteogenic amino acids can be incorporated into both α-helix and β-sheet structural motifs and generally enhance protein stability towards unfolding by heat and chemical denaturants, and retard their degradation by proteases. Recent detailed structural and thermodynamic studies have demonstrated that the increase in buried hydrophobic surface area that accompanies fluorination is primarily responsible for the stabilizing properties of fluorinated side chains. Fluorination appears to be a particularly useful strategy for increasing protein stability because fluorinated amino acids closely retain the shape of the side chain, and are thus minimally perturbing to protein structure and function. The first part of this chapter discusses some examples of highly fluorinated model proteins designed by our laboratory and protocols for their synthesis. In the second part, methods for determining their thermodynamic stability, along with conditions that have proven to be useful for crystallizing these proteins, are presented.
Collapse
Affiliation(s)
- Benjamin C Buer
- Department of Chemistry, University of Michigan, 930 N. University Ave., Ann Arbor, MI, 48109, USA
| | | |
Collapse
|
34
|
Tena-Solsona M, Miravet JF, Escuder B. Tetrapeptidic Molecular Hydrogels: Self-assembly and Co-aggregation with Amyloid Fragment Aβ1-40. Chemistry 2013; 20:1023-31. [DOI: 10.1002/chem.201302651] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2013] [Indexed: 12/21/2022]
|
35
|
Zhang L, Jiang C, Zhang H, Gong X, Yang L, Miao L, Shi Y, Zhang Y, Kong W, Zhang C, Shan Y. A novel modified peptide derived from membrane-proximal external region of human immunodeficiency virus type 1 envelope significantly enhances retrovirus infection. J Pept Sci 2013; 20:46-54. [PMID: 24254845 DOI: 10.1002/psc.2587] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2013] [Revised: 10/16/2013] [Accepted: 10/16/2013] [Indexed: 11/12/2022]
Abstract
Efficient gene transfer is a critical goal in retroviral transduction. Several peptides capable of forming amyloid fibrils, such as the 39-residue semen-derived infection-enhancing peptide (SEVI), have demonstrated the ability to boost retroviral gene delivery. Here, a 13-residue peptide P13 (Ac-(671) NWFDITNWLWYIK(683)) derived from the membrane-proximal external region of the human immunodeficiency virus type 1 (HIV-1) gp41 transmembrane protein, together with its 16-residue peptide derivative (P16) were found to enhance HIV-1 infection significantly. Both peptides, P13 and P16, could form amyloid fibril structures to potently enhance HIV-1 infectivity. Further investigations showed that both aromatic Trp residues and cationic Lys residues contributed to the enhancement of HIV-1 infection by these two active peptides. P16 could more effectively augment HIV-1 YU-2 infection than SEVI, implying its potential applications as a tool in the lab to improve gene transfer rates.
Collapse
Affiliation(s)
- Lishuang Zhang
- National Engineering Laboratory for AIDS Vaccine, College of Life Science, Jilin University, Changchun, Jilin, China
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
36
|
Xie L, Luo Y, Wei G. Aβ(16-22) peptides can assemble into ordered β-barrels and bilayer β-sheets, while substitution of phenylalanine 19 by tryptophan increases the population of disordered aggregates. J Phys Chem B 2013; 117:10149-60. [PMID: 23926957 DOI: 10.1021/jp405869a] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A recent experimental study reported that termini-uncapped Aβ(16-22) (with sequence KLVFFAE) peptides self-assembled into nanofibrils at pH 2.0. The oligomerization of this uncapped peptide at atomic level in acidic pH condition remains to be determined, as computational studies mainly focus on the self-assembly of capped Aβ(16-22) peptides at neutral pH condition. In this study, using replica exchange molecular dynamics (REMD) simulations with explicit solvent, we investigated the octameric structures of the uncapped Aβ(16-22) and its F19W variant at acidic pH condition. Our simulations reveal that the Aβ(16-22) octamers adopt various conformations, including closed β-barrels, bilayer β-sheets, and disordered aggregates. The closed β-barrel conformation is particularly interesting, as the cylindrical β-barrel has been reported recently as a cytotoxic species. Interpeptide contact probability analyses between all pairs of residues reveal that the hydrophobic and aromatic stacking interactions between F19 residues play an essential role in the formation of β-barrels and bilayer β-sheets. The importance of F19 and the steric effect on the structures of Aβ(16-22) octamers are further examined by REMD simulation of F19W mutant. This REMD run shows that substitution of F19 by W with a more bulky aromatic side chain significantly reduces the β-sheet content and in turn enhances the population of disordered aggregates, indicating that the steric effect significantly affect the self-assembly of low molecular weight Aβ(16-22) oligomers.
Collapse
Affiliation(s)
- Luogang Xie
- State Key Laboratory of Surface Physics, and Department of Physics, Fudan University, 220 Handan Road, Shanghai, 200433, China
| | | | | |
Collapse
|
37
|
Sarkar N, Dubey VK. Exploring critical determinants of protein amyloidogenesis: a review. J Pept Sci 2013; 19:529-36. [DOI: 10.1002/psc.2539] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2013] [Revised: 06/03/2013] [Accepted: 06/17/2013] [Indexed: 11/12/2022]
Affiliation(s)
- Nandini Sarkar
- Department of Biotechnology and Medical Engineering; National Institute of Technology Rourkela; Rourkela Odisha 769008 India
| | - Vikash Kumar Dubey
- Department of Biotechnology; Indian Institute of Technology Guwahati; Guwahati Assam 781039 India
| |
Collapse
|
38
|
Paulite M, Blum C, Schmid T, Opilik L, Eyer K, Walker GC, Zenobi R. Full spectroscopic tip-enhanced Raman imaging of single nanotapes formed from β-amyloid(1-40) peptide fragments. ACS NANO 2013; 7:911-20. [PMID: 23311496 DOI: 10.1021/nn305677k] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
This study demonstrates that spectral fingerprint patterns for a weakly scattering biological sample can be obtained reproducibly and reliably with tip-enhanced Raman spectroscopy (TERS) that correspond well with the conventional confocal Raman spectra collected for the bulk substance. These provided the basis for obtaining TERS images of individual self-assembled peptide nanotapes using an automated, objective procedure that correlate with the simultaneously obtained scanning tunneling microscopy (STM) images. TERS and STM images (64 × 64 pixels, 3 × 3 μm²) of peptide nanotapes are presented that rely on marker bands in the Raman fingerprint region. Full spectroscopic information in every pixel was obtained, allowing post-processing of data and identification of species of interest. Experimentally, the "gap-mode" TERS configuration was used with a solid metal (Ag) tip in feedback with a metal substrate (Au). Confocal Raman data of bulk nanotapes, TERS point measurements with longer acquisition time, atomic force microscopy images, and an infrared absorption spectrum of bulk nanotapes were recorded for comparison. It is shown that the unique combination of topographic and spectroscopic data that TERS imaging provides reveals differences between the STM and TERS images, for example, nanotapes that are only weakly visible in the STM images, a coverage of the surface with an unknown substance, and the identification of a patch as a protein assembly that could not be unambiguously assigned based on the STM image alone.
Collapse
Affiliation(s)
- Melissa Paulite
- Department of Chemistry and Applied Biosciences, Laboratory of Organic Chemistry, ETH Zurich, 8093 Zurich, Switzerland
| | | | | | | | | | | | | |
Collapse
|
39
|
Attanasio F, Convertino M, Magno A, Caflisch A, Corazza A, Haridas H, Esposito G, Cataldo S, Pignataro B, Milardi D, Rizzarelli E. Carnosine inhibits Aβ(42) aggregation by perturbing the H-bond network in and around the central hydrophobic cluster. Chembiochem 2013; 14:583-92. [PMID: 23440928 DOI: 10.1002/cbic.201200704] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2012] [Indexed: 02/06/2023]
Abstract
Aggregation of the amyloid-β peptide (Aβ) into fibrillar structures is a hallmark of Alzheimer's disease. Thus, preventing self-assembly of the Aβ peptide is an attractive therapeutic strategy. Here, we used experimental techniques and atomistic simulations to investigate the influence of carnosine, a dipeptide naturally occurring in the brain, on Aβ aggregation. Scanning force microscopy, circular dichroism and thioflavin T fluorescence experiments showed that carnosine does not modify the conformational features of Aβ42 but nonetheless inhibits amyloid growth. Molecular dynamics (MD) simulations indicated that carnosine interacts transiently with monomeric Aβ42 by salt bridges with charged side chains, and van der Waals contacts with residues in and around the central hydrophobic cluster ((17)LVFFA(21)). NMR experiments on the nonaggregative fragment Aβ12-28 did not evidence specific intermolecular interactions between the peptide and carnosine, in agreement with MD simulations. However, a close inspection of the spectra revealed that carnosine interferes with the local propensity of the peptide to form backbone hydrogen bonds close to the central hydrophobic cluster (residues E22, S26 and N27). Finally, MD simulations of aggregation-prone Aβ heptapeptide segments show that carnosine reduces the propensity to form intermolecular backbone hydrogen bonds in the region 18-24. Taken together, the experimental and simulation results (cumulative MD sampling of 0.2 ms) suggest that, despite the inability of carnosine to form stable contacts with Aβ, it might block the pathway toward toxic aggregates by perturbing the hydrogen bond network near residues with key roles in fibrillogenesis.
Collapse
Affiliation(s)
- Francesco Attanasio
- Istituto di Biostrutture e Bioimmagini-UOS CT, Consiglio Nazionale delle Ricerche, V.le A. Doria 6, 95125 Catania, Italy
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
40
|
Berhanu WM, Hansmann UHE. Side-chain hydrophobicity and the stability of Aβ₁₆₋₂₂ aggregates. Protein Sci 2012; 21:1837-48. [PMID: 23015407 PMCID: PMC3575914 DOI: 10.1002/pro.2164] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2012] [Revised: 09/06/2012] [Accepted: 09/14/2012] [Indexed: 11/05/2022]
Abstract
Recent mutagenesis studies using the hydrophobic segment of Aβ suggest that aromatic π-stacking interactions may not be critical for fibril formation. We have tested this conjecture by probing the effect of Leu, Ile, and Ala mutation of the aromatic Phe residues at positions 19 and 20, on the double-layer hexametric chains of Aβ fragment Aβ₁₆₋₂₂ using explicit solvent all-atom molecular dynamics. As these simulations rely on the accuracy of the utilized force fields, we first evaluated the dynamic and stability dependence on various force fields of small amyloid aggregates. These initial investigations led us to choose AMBER99SB-ILDN as force field in multiple long molecular dynamics simulations of 100 ns that probe the stability of the wild-type and mutants oligomers. Single-point and double-point mutants confirm that size and hydrophobicity are key for the aggregation and stability of the hydrophobic core region (Aβ₁₆₋₂₂). This suggests as a venue for designing Aβ aggregation inhibitors the substitution of residues (especially, Phe 19 and 20) in the hydrophobic region (Aβ₁₆₋₂₂) with natural and non-natural amino acids of similar size and hydrophobicity.
Collapse
Affiliation(s)
- Workalemahu M Berhanu
- Department of Chemistry and Biochemistry, University of OklahomaNorman, Oklahoma 73019
| | - Ulrich H E Hansmann
- Department of Chemistry and Biochemistry, University of OklahomaNorman, Oklahoma 73019
| |
Collapse
|
41
|
Clark GA, Baleja JD, Kumar K. Cross-strand interactions of fluorinated amino acids in β-hairpin constructs. J Am Chem Soc 2012; 134:17912-21. [PMID: 23078597 DOI: 10.1021/ja212080f] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
We describe herein the design, synthesis, and thermodynamic characterization of fluorinated β-hairpin constructs. Introduction of hexafluoroleucine (Hfl) did not perturb β-hairpin formation, as judged by (1)H NMR structures of four peptides determined to <1 Å backbone RMSDs, allowing direct comparison of thermodynamic stabilities of fluorinated peptides to their hydrocarbon counterparts. Judicious fluorination of peptides often results in increased thermal and chemical stability of the resultant folded structures. However, we found that when cross-strand residue partners were varied, the side-chain interaction energies followed the order Leu-Leu > Hfl-Leu > Hfl-Hfl. All peptides were more structured in 90% MeOH than in aqueous buffers. The peptides with Hfl-Leu or Hfl-Hfl cross-strand partners showed increased interaction energies in this solvent compared to those in water, in contrast to the insignificant effect on Leu-Leu. Our results inform the binding and assembly of peptides containing Hfl in the context of β-sheet structures and may be useful in interpreting binding of fluorinated ligands and peptides to biological targets.
Collapse
Affiliation(s)
- Ginevra A Clark
- Department of Chemistry, Tufts University, 62 Talbot Avenue, Medford, Massachusetts 02155, USA
| | | | | |
Collapse
|
42
|
Jana AK, Sengupta N. Adsorption mechanism and collapse propensities of the full-length, monomeric Aβ(1-42) on the surface of a single-walled carbon nanotube: a molecular dynamics simulation study. Biophys J 2012; 102:1889-96. [PMID: 22768945 DOI: 10.1016/j.bpj.2012.03.036] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2011] [Revised: 03/02/2012] [Accepted: 03/14/2012] [Indexed: 11/25/2022] Open
Abstract
Though nanomaterials such as carbon nanotubes have gained recent attention in biology and medicine, there are few studies at the single-molecule level that explore their interactions with disease-causing proteins. Using atomistic molecular-dynamics simulations, we have investigated the interactions of the monomeric Aβ(1-42) peptide with a single-walled carbon nanotube of small diameter. Starting with peptide-nanotube complexes that delineate the interactions of different segments of the peptide, we find rapid convergence in the peptide's adsorption behavior on the nanotube surface, manifested in its arrested movement, the convergence of peptide-nanotube contact areas and approach distances, and in increased peptide wrapping around the nanotube. In systems where the N-terminal domain is initially distal from nanotube, the adsorption phenomena are initiated by interactions arising from the central hydrophobic core, and precipitated by those arising from the N-terminal residues. Our simulations and free energy calculations together demonstrate that the presence of the nanotube increases the energetic favorability of the open state. We note that the observation of peptide localization could be leveraged for site-specific drug delivery, while the decreased propensity of collapse appears promising for altering kinetics of the peptide's self-assembly.
Collapse
Affiliation(s)
- Asis K Jana
- Physical Chemistry Division, National Chemical Laboratory, Pune, India
| | | |
Collapse
|
43
|
Bowerman CJ, Nilsson BL. Self-assembly of amphipathic β-sheet peptides: insights and applications. Biopolymers 2012; 98:169-84. [PMID: 22782560 DOI: 10.1002/bip.22058] [Citation(s) in RCA: 176] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Amphipathic peptides composed of alternating polar and nonpolar residues have a strong tendency to self-assemble into one-dimensional, amyloid-like fibril structures. Fibrils derived from peptides of general (XZXZ)(n) sequence in which X is hydrophobic and Z is hydrophilic adopt a putative β-sheet bilayer. The bilayer configuration allows burial of the hydrophobic X side chain groups in the core of the fibril and leaves the polar Z side chains exposed to solvent. This architectural arrangement provides fibrils that maintain high solubility in water and has facilitated the recent exploitation of self-assembled amphipathic peptide fibrils as functional biomaterials. This article is a critical review of the development and application of self-assembling amphipathic peptides with a focus on the fundamental insight these types of peptides provide into peptide self-assembly phenomena.
Collapse
Affiliation(s)
- Charles J Bowerman
- Department of Chemistry, University of Rochester, Rochester, NY 14627, USA
| | | |
Collapse
|
44
|
Sukhanova A, Poly S, Shemetov A, Bronstein I, Nabiev I. Implications of protein structure instability: from physiological to pathological secondary structure. Biopolymers 2012; 97:577-88. [PMID: 22605549 DOI: 10.1002/bip.22055] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Proteins are folded during their synthesis; this process may be spontaneous or assisted. Both phenomena are carefully regulated by the "housekeeping" mechanism and molecular chaperones to avoid the appearance of misfolded proteins. Unfolding process generally occurs during physiological degradation of protein, but in some specific cases it results from genetic or environmental changes and does not correspond to metabolic needs. The main outcome of these phenomena is the appearance of nonfunctional pathologically unfolded proteins with a strong tendency to aggregation. Moreover, for some of these unfolded proteins, the agglomeration that follows initial proteins association may give rise to highly structured soluble aggregates. These aggregates have been identified as the main cause of the so-called amyloidosis or amyloid diseases, such as Alzheimer's, Parkinson's, and Creutzfeldt-Jakob diseases, and type II diabetes mellitus. Although some common mechanisms of amyloid protein aggregation have been identified, the roles of the environmental conditions inducing amyloidosis remain to be clarified. In this review, we will summarize recent studies identifying the origin of amyloid nucleation and will try to predict the therapeutic prospects that may be opened by elucidation of the amyloidosis mechanisms.
Collapse
Affiliation(s)
- Alyona Sukhanova
- Institute of Molecular Medicine, Trinity College Dublin, Dublin 8, Ireland.
| | | | | | | | | |
Collapse
|
45
|
Preston GW, Radford SE, Ashcroft AE, Wilson AJ. Covalent cross-linking within supramolecular peptide structures. Anal Chem 2012; 84:6790-7. [PMID: 22746360 DOI: 10.1021/ac301198c] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
β-Sheet peptide nanostructures (e.g., amyloid fibrils) are recognized as important entities in biological systems and as functional materials in their own right. Their unique physical properties and architectural complexity, however, present a challenge for structure determination at atomic resolution. Covalent cross-linking and mass spectrometry are appealing methods for this endeavor because, potentially, a large amount of information can be extracted from a small sample in a single experiment. Previously, we described preliminary studies on the use of a photoreactive diazirine-containing amino acid to cross-link peptide monomers in nanostructures, together with the integrated separation and analysis of the products using ion mobility spectrometry coupled to conventional mass spectrometry. Here, a pH-switchable system (Aβ(16-22), a sequence from the amyloid-β peptide) was used to examine cross-linking chemistry in morphologically distinct supramolecular structures containing, or entirely composed of, diazirine-functionalized peptides. We examine the relationship between cross-linker chemistry, covalent cross-links (identified using chemical derivatization and tandem mass spectrometry), and noncovalent structure, and report differences in the site of cross-linking that can only be explained by supramolecular templating. The results demonstrate the applicability of the approach for obtaining structural restraints in ordered supramolecular assemblies, provided that a considered evaluation of the cross-linked products is undertaken.
Collapse
Affiliation(s)
- George W Preston
- School of Chemistry, Faculty of Biological Sciences, University of Leeds, Woodhouse Lane, Leeds LS2 9JT, UK
| | | | | | | |
Collapse
|
46
|
Childers WS, Anthony NR, Mehta AK, Berland KM, Lynn DG. Phase networks of cross-β peptide assemblies. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2012; 28:6386-6395. [PMID: 22439620 DOI: 10.1021/la300143j] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Recent evidence suggests that simple peptides can access diverse amphiphilic phases, and that these structures underlie the robust and widely distributed assemblies implicated in nearly 40 protein misfolding diseases. Here we exploit a minimal nucleating core of the Aβ peptide of Alzheimer's disease to map its morphologically accessible phases that include stable intermolecular molten particles, fibers, twisted and helical ribbons, and nanotubes. Analyses with both fluorescence lifetime imaging microscopy (FLIM) and transmission electron microscopy provide evidence for liquid-liquid phase separations, similar to the coexisting dilute and dense protein-rich liquid phases so critical for the liquid-solid transition in protein crystallization. We show that the observed particles are critical for transitions to the more ordered cross-β peptide phases, which are prevalent in all amyloid assemblies, and identify specific conditions that arrest assembly at the phase boundaries. We have identified a size dependence of the particles in order to transition to the para-crystalline phase and a width of the cross-β assemblies that defines the transition between twisted fibers and helically coiled ribbons. These experimental results reveal an interconnected network of increasing molecularly ordered cross-β transitions, greatly extending the initial computational models for cross-β assemblies.
Collapse
Affiliation(s)
- W Seth Childers
- Center for Fundamental and Applied Molecular Evolution, NSF/NASA Center for Chemical Evolution, Departments of Chemistry and Biology, Atlanta, Georgia 30322, USA
| | | | | | | | | |
Collapse
|
47
|
Doran TM, Anderson EA, Latchney SE, Opanashuk LA, Nilsson BL. Turn nucleation perturbs amyloid β self-assembly and cytotoxicity. J Mol Biol 2012; 421:315-28. [PMID: 22326870 DOI: 10.1016/j.jmb.2012.01.055] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2011] [Revised: 01/27/2012] [Accepted: 01/31/2012] [Indexed: 10/14/2022]
Abstract
The accumulation of senile plaques composed of amyloid β (Aβ) fibrils is a hallmark of Alzheimer's disease, although prefibrillar oligomeric species are believed to be the primary neurotoxic congeners in the pathogenesis of Alzheimer's disease. Uncertainty regarding the mechanistic relationship between Aβ oligomer and fibril formation and the cytotoxicity of these aggregate species persists. β-Turn formation has been proposed to be a potential rate-limiting step during Aβ fibrillogenesis. The effect of turn nucleation on Aβ self-assembly was probed by systematically replacing amino acid pairs in the putative turn region of Aβ (residues 24-27) with d-ProGly ((D)PG), an effective turn-nucleating motif. The kinetic, thermodynamic, and cytotoxic effects of these mutations were characterized. It was found that turn formation dramatically accelerated Aβ fibril self-assembly dependent on the site of turn nucleation. The cytotoxicity of the three (D)PG-containing Aβ variants was significantly lower than that of wild-type Aβ40, presumably due to decreased oligomer populations as a function of a more rapid progression to mature fibrils; oligomer populations were not eliminated, however, suggesting that turn formation is also a feature of oligomer structures. These results indicate that turn nucleation is a critical step in Aβ40 fibril formation.
Collapse
Affiliation(s)
- Todd M Doran
- Department of Chemistry, University of Rochester, Rochester, NY 14627, USA
| | | | | | | | | |
Collapse
|
48
|
Doran TM, Kamens AJ, Byrnes NK, Nilsson BL. Role of amino acid hydrophobicity, aromaticity, and molecular volume on IAPP(20-29) amyloid self-assembly. Proteins 2012; 80:1053-65. [DOI: 10.1002/prot.24007] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2011] [Revised: 11/12/2011] [Accepted: 11/18/2011] [Indexed: 01/22/2023]
|
49
|
Ryan DM, Nilsson BL. Self-assembled amino acids and dipeptides as noncovalent hydrogels for tissue engineering. Polym Chem 2012. [DOI: 10.1039/c1py00335f] [Citation(s) in RCA: 202] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
This review critically assesses progress in the use of self-assembling dipeptides and amino acids as hydrogel materials for tissue engineering.
Collapse
Affiliation(s)
- Derek M. Ryan
- University of Rochester
- Department of Chemistry
- Rochester
- USA
| | | |
Collapse
|
50
|
Bowerman CJ, Liyanage W, Federation AJ, Nilsson BL. Tuning β-sheet peptide self-assembly and hydrogelation behavior by modification of sequence hydrophobicity and aromaticity. Biomacromolecules 2011; 12:2735-45. [PMID: 21568346 DOI: 10.1021/bm200510k] [Citation(s) in RCA: 145] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Peptide self-assembly leading to cross-β amyloid structures is a widely studied phenomenon because of its role in amyloid pathology and the exploitation of amyloid as a functional biomaterial. The self-assembly process is governed by hydrogen bonding, hydrophobic, aromatic π-π, and electrostatic Coulombic interactions. A role for aromatic π-π interactions in peptide self-assembly leading to amyloid has been proposed, but the relative contributions of π-π versus general hydrophobic interactions in these processes are poorly understood. The Ac-(XKXK)(2)-NH(2) peptide was used to study the contributions of aromatic and hydrophobic interactions to peptide self-assembly. Position X was globally replaced by valine (Val), isoleucine (Ile), phenylalanine (Phe), pentafluorophenylalanine (F(5)-Phe), and cyclohexylalanine (Cha). At low pH, these peptides remain monomeric because of repulsion of charged lysine (Lys) residues. Increasing the solvent ionic strength to shield repulsive charge-charge interactions between protonated Lys residues facilitated cross-β fibril formation. It was generally found that as peptide hydrophobicity increased, the required ionic strength to induce self-assembly decreased. At [NaCl] ranging from 0 to 1000 mM, the Val sequence failed to assemble. Assembly of the Phe sequence commenced at 700 mM NaCl and at 300 mM NaCl for the less hydrophobic Ile variant, even though it displayed a mixture of random coil and β-sheet secondary structures over all NaCl concentrations. β-Sheet formation for F(5)-Phe and Cha sequences was observed at only 20 and 60 mM NaCl, respectively. Whereas self-assembly propensity generally correlated to peptide hydrophobicity and not aromatic character the presence of aromatic amino acids imparted unique properties to fibrils derived from these peptides. Nonaromatic peptides formed fibrils of 3-15 nm in diameter, whereas aromatic peptides formed nanotape or nanoribbon architectures of 3-7 nm widths. In addition, all peptides formed fibrillar hydrogels at sufficient peptide concentrations, but nonaromatic peptides formed weak gels, whereas aromatic peptides formed rigid gels. These findings clarify the influence of aromatic amino acids on peptide self-assembly processes and illuminate design principles for the inclusion of aromatic amino acids in amyloid-derived biomaterials.
Collapse
Affiliation(s)
- Charles J Bowerman
- Department of Chemistry, University of Rochester, Rochester, New York 14627-0216, USA
| | | | | | | |
Collapse
|