1
|
Chatterjee S, Nam Y, Salimi A, Lee JY. Monitoring early-stage β-amyloid dimer aggregation by histidine site-specific two-dimensional infrared spectroscopy in a simulation study. Phys Chem Chem Phys 2022; 24:18691-18702. [PMID: 35899740 DOI: 10.1039/d2cp02479a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Monitoring early-stage β-amyloid (Aβ) dimerization is a formidable challenge for understanding neurological diseases. We compared β-sheet formation and histidine site-specific two-dimensional infrared (2D IR) spectroscopic signatures of Aβ dimers with different histidine states (δ; Nδ1-H, ε; Nε2-H, or π; both protonated). Molecular dynamics (MD) simulations revealed that β-sheet formation is favored for the δδδ:δδδ and πππ:πππ tautomeric isomers showing strong couplings and frequent contacts between the central hydrophobic core and C-terminus compared with the εεε:εεε isomer. Characteristic blue-shifts in the 2D IR central bands were observed upon monomer-dimer transformation. The εεε:εεε dimer exhibited larger frequency shifts than δδδ:δδδ and πππ:πππ implying that the red-shift may have a correlation with Nδ1-H(δ) protonation. Our results support the tautomerization/protonation hypothesis that attributes Aβ misfolding to histidine tautomers as a possible primary initiator for Aβ aggregation and facilitates the application of histidine site-specific 2D IR spectroscopy for studying early-stage Aβ self-assembly.
Collapse
Affiliation(s)
| | - Yeonsig Nam
- Department of Chemistry, Sungkyunkwan University, Suwon 440-746, Korea. .,Department of Chemistry, University of California, Irvine, California 92697-2025, USA
| | - Abbas Salimi
- Department of Chemistry, Sungkyunkwan University, Suwon 440-746, Korea.
| | - Jin Yong Lee
- Department of Chemistry, Sungkyunkwan University, Suwon 440-746, Korea.
| |
Collapse
|
2
|
Stelmakh A, Cai W, Baumketner A. Attraction between Like-Charged Macroions Mediated by Specific Counterion Configurations. J Phys Chem B 2019; 123:9971-9983. [PMID: 31657573 DOI: 10.1021/acs.jpcb.9b06545] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Attraction between like-charged macroions is fundamental to many processes in biology, chemistry, and physics. It also plays an important role in industrial applications such as ion-extraction processes or catalysis. In this work, we report a novel mechanism by which attraction can be realized between spherical macroions at high ionic strength. It consists of specific configurations of two, three, and more counterions that appear between macroions with high statistical probability. The attraction is manifested in a minimum in the potential of mean force between the macroions at short distances. Its depth increases with increasing charge of the macroion, demonstrating that the attraction is electrostatic in nature. It is shown that the implicit solvent model with a distance-dependent dielectric constant can capture both the geometry and thermodynamics of charge-stabilized macroion dimers on the qualitative level. The results obtained for a model colloid with a smooth surface are extrapolated to more realistic systems. Evidence is found that the reported mechanism can be observed in small chemical compounds with encapsulated ions such as fullerenes.
Collapse
Affiliation(s)
- A Stelmakh
- Department of Chemistry , Ivan Franko Lviv National University , 6 Kyrylo and Mefodii Street , Lviv 79005 , Ukraine.,Institute of Inorganic Chemistry, Department of Chemistry and Applied Bioscience , ETH Zurich , Vladimir Prelog Weg 1 , CH-8093 Zurich , Switzerland
| | - W Cai
- Department of Mathematics , Southern Methodist University , 3200 Dyer Street , Dallas , Texas 75275 , United States
| | - A Baumketner
- Institute for Condensed Matter Physics , NAS of Ukraine , 1 Svientsistsky Str , Lviv , 79011 , Ukraine
| |
Collapse
|
3
|
Nguyen HL, Krupa P, Hai NM, Linh HQ, Li MS. Structure and Physicochemical Properties of the Aβ42 Tetramer: Multiscale Molecular Dynamics Simulations. J Phys Chem B 2019; 123:7253-7269. [DOI: 10.1021/acs.jpcb.9b04208] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- Hoang Linh Nguyen
- Institute for Computational Science and Technology, SBI Building, Quang Trung Software
City, Tan Chanh Hiep Ward, District 12, Ho Chi Minh City 700000, Vietnam
- Biomedical Engineering Department, Ho Chi Minh City University of Technology-VNU HCM, 268 Ly Thuong Kiet Street, Distr. 10, Ho Chi Minh City 700000, Vietnam
| | - Pawel Krupa
- Institute of Physics Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warsaw, Poland
| | - Nguyen Minh Hai
- Faculty of Physics and Engineering Physics, University of Science-VNU HCM, Ho Chi Minh City 700000, Vietnam
| | - Huynh Quang Linh
- Biomedical Engineering Department, Ho Chi Minh City University of Technology-VNU HCM, 268 Ly Thuong Kiet Street, Distr. 10, Ho Chi Minh City 700000, Vietnam
| | - Mai Suan Li
- Institute of Physics Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warsaw, Poland
| |
Collapse
|
4
|
Nguyen PH, Campanera JM, Ngo ST, Loquet A, Derreumaux P. Tetrameric Aβ40 and Aβ42 β-Barrel Structures by Extensive Atomistic Simulations. II. In Aqueous Solution. J Phys Chem B 2019; 123:6750-6756. [DOI: 10.1021/acs.jpcb.9b05288] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Affiliation(s)
- Phuong H. Nguyen
- CNRS, Université de Paris, UPR 9080,
Laboratoire de Biochimie Théorique, 13 rue Pierre et Marie Curie, F-75005, Paris, France
- Institut de Biologie Physico-Chimique-Fondation Edmond de Rothschild, PSL Research University, Paris, France
| | - Josep M. Campanera
- Departament de Fisicoquímica, Facultat de Farmacia, Universitat de Barcelona, 08028 Barcelona, Catalonia, Spain
| | - Son Tung Ngo
- Laboratory of Theoretical and Computational Biophysics, Ton Duc Thang University, Ho Chi Minh City, Vietnam
- Faculty of Applied Sciences, Ton Duc Thang University, Ho Chi Minh City, Vietnam
| | - Antoine Loquet
- Institute of Chemistry and Biology of Membranes and Nanoobjects, UMR5248 CNRS, Université de Bordeaux, Bordeaux, France
| | - Philippe Derreumaux
- Laboratory of Theoretical Chemistry, Ton Duc Thang University, Ho Chi Minh City, Vietnam
- Faculty of Pharmacy, Ton Duc Thang University, Ho Chi Minh City, Vietnam
| |
Collapse
|
5
|
Lu L, Deng Y, Li X, Li H, Karniadakis GE. Understanding the Twisted Structure of Amyloid Fibrils via Molecular Simulations. J Phys Chem B 2018; 122:11302-11310. [PMID: 30106299 DOI: 10.1021/acs.jpcb.8b07255] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Accumulation and aggregation of amyloid are associated with the pathogenesis of many human diseases, such as Alzheimer's disease and Type 2 diabetes mellitus. Therefore, a quantitative understanding of the molecular mechanisms causing different aggregated structures and biomechanical properties of amyloid fibrils could shed some light into the progression of these diseases. In this work, we develop coarse-grained molecular dynamics (CGMD) models to simulate the dynamic self-assembly of two types of amyloids (amylin and amyloid β (Aβ)). We investigate the structural and mechanical properties of different types of aggregated amyloid fibrils. Our simulations demonstrate that amyloid fibrils could result from longitudinal growth of protofilament bundles, confirming one of the hypotheses on the fibril formation. In addition, we find that the persistence length of amylin fibrils increases concurrently with their pitch length, suggesting that the bending stiffness of amylin fibrils becomes larger when the amylin fibrils are less twisted. Similar results are observed for Aβ fibrils. These findings quantify the connection between the structural and the biomechanical properties of the fibrils. The CGMD models developed in this work can be potentially used to examine efficacy of anti-aggregation drugs, which could help in developing new treatments.
Collapse
Affiliation(s)
- Lu Lu
- Division of Applied Mathematics , Brown University , Providence , Rhode Island 02912 , United States
| | - Yixiang Deng
- School of Engineering , Brown University , Providence , Rhode Island 02912 , United States
| | - Xuejin Li
- Division of Applied Mathematics , Brown University , Providence , Rhode Island 02912 , United States
| | - He Li
- Division of Applied Mathematics , Brown University , Providence , Rhode Island 02912 , United States
| | - George Em Karniadakis
- Division of Applied Mathematics , Brown University , Providence , Rhode Island 02912 , United States
| |
Collapse
|
6
|
Sarma R, Wong KY, Lynch GC, Pettitt BM. Peptide Solubility Limits: Backbone and Side-Chain Interactions. J Phys Chem B 2018; 122:3528-3539. [PMID: 29384681 PMCID: PMC5909690 DOI: 10.1021/acs.jpcb.7b10734] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
We calculate the solubility limit of pentapeptides in water by simulating the phase separation in an oversaturated aqueous solution. The solubility limit order followed by our model peptides (GGRGG > GGDGG > GGGGG > GGVGG > GGQGG > GGNGG > GGFGG) is found to be the same as that reported for amino acid monomers from experiment (R > D > G > V > Q > N > F). Investigation of dynamical properties of peptides shows that the higher the solubility of a peptide is, the lower the time spent by the peptide in the aggregated cluster is. We also demonstrate that fluctuations in conformation and hydration number of peptide in monomeric form are correlated with the solubility of the peptide. We considered energetic mechanisms and dynamical properties of interbackbone CO-CO and CO···HN interactions. Our results confirm that CO-CO interactions more than the interbackbone H-bonds are important in peptide self-assembly and association. Further, we find that the stability of H-bonded peptide pairs arises mainly from coexisting CO-CO and CO···HN interactions.
Collapse
Affiliation(s)
- Rahul Sarma
- Sealy Center for Structural Biology and Molecular Biophysics, Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, 301 University Boulevard, Galveston, Texas 77555-0304, United States
| | - Ka-Yiu Wong
- Sealy Center for Structural Biology and Molecular Biophysics, Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, 301 University Boulevard, Galveston, Texas 77555-0304, United States
| | - Gillian C. Lynch
- Sealy Center for Structural Biology and Molecular Biophysics, Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, 301 University Boulevard, Galveston, Texas 77555-0304, United States
| | - B. Montgomery Pettitt
- Sealy Center for Structural Biology and Molecular Biophysics, Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, 301 University Boulevard, Galveston, Texas 77555-0304, United States
| |
Collapse
|
7
|
Blinov N, Khorvash M, Wishart DS, Cashman NR, Kovalenko A. Initial Structural Models of the Aβ42 Dimer from Replica Exchange Molecular Dynamics Simulations. ACS OMEGA 2017; 2:7621-7636. [PMID: 31457321 PMCID: PMC6645216 DOI: 10.1021/acsomega.7b00805] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/16/2017] [Accepted: 10/26/2017] [Indexed: 05/27/2023]
Abstract
Experimental characterization of the molecular structure of small amyloid (A)β oligomers that are currently considered as toxic agents in Alzheimer's disease is a formidably difficult task due to their transient nature and tendency to aggregate. Such structural information is of importance because it can help in developing diagnostics and an effective therapy for the disease. In this study, molecular simulations and protein-protein docking are employed to explore a possible connection between the structure of Aβ monomers and the properties of the intermonomer interface in the Aβ42 dimer. A structurally diverse ensemble of conformations of the monomer was sampled in microsecond timescale implicit solvent replica exchange molecular dynamics simulations. Representative structures with different solvent exposure of hydrophobic residues and secondary structure content were selected to build structural models of the dimer. Analysis of these models reveals that formation of an intramonomer salt bridge (SB) between Asp23 and Lys28 residues can prevent the building of a hydrophobic interface between the central hydrophobic clusters (CHCs) of monomers upon dimerization. This structural feature of the Aβ42 dimer is related to the difference in packing of hydrophobic residues in monomers with the Asp23-Lys28 SB in on and off states, in particular, to a lower propensity to form hydrophobic contacts between the CHC domain and C-terminal residues in monomers with a formed SB. These findings could have important implications for understanding the difference between aggregation pathways of Aβ monomers leading to neurotoxic oligomers or inert fibrillar structures.
Collapse
Affiliation(s)
- Nikolay Blinov
- Department
of Mechanical Engineering, University of
Alberta, Edmonton, Alberta T6G 1H9, Canada
- National
Institute for Nanotechnology, National Research
Council of Canada, Edmonton, Alberta T6G 2M9, Canada
| | - Massih Khorvash
- Department
of Medicine, University of British Columbia, Vancouver, British Columbia V6T 2B5, Canada
| | - David S. Wishart
- Departments
of Computing Science and Biological Sciences, University of Alberta, Edmonton, Alberta T6G 2E8, Canada
| | - Neil R. Cashman
- Department
of Medicine, University of British Columbia, Vancouver, British Columbia V6T 2B5, Canada
| | - Andriy Kovalenko
- Department
of Mechanical Engineering, University of
Alberta, Edmonton, Alberta T6G 1H9, Canada
- National
Institute for Nanotechnology, National Research
Council of Canada, Edmonton, Alberta T6G 2M9, Canada
| |
Collapse
|
8
|
Bacci M, Vymětal J, Mihajlovic M, Caflisch A, Vitalis A. Amyloid β Fibril Elongation by Monomers Involves Disorder at the Tip. J Chem Theory Comput 2017; 13:5117-5130. [PMID: 28870064 DOI: 10.1021/acs.jctc.7b00662] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The growth of amyloid fibrils from Aβ1-42 peptide, one of the key pathogenic players in Alzheimer's disease, is believed to follow a nucleation-elongation mechanism. Fibril elongation is often described as a "dock-lock" procedure, where a disordered monomer adsorbs to an existing fibril in a relatively fast process (docking), followed by a slower conformational transition toward the ordered state of the template (locking). Here, we use molecular dynamics simulations of an ordered pentamer of Aβ42 at fully atomistic resolution, which includes solvent, to characterize the elongation process. We construct a Markov state model from an ensemble of short trajectories generated by an advanced sampling algorithm that efficiently diversifies a subset of the system without any bias forces. This subset corresponds to selected dihedral angles of the peptide chain at the fibril tip favored to be the fast growing one experimentally. From the network model, we extract distinct locking pathways covering time scales in the high microsecond regime. Slow steps are associated with the exchange of hydrophobic contacts, between nonnative and native intermolecular contacts as well as between intra- and intermolecular ones. The N-terminal segments, which are disordered in fibrils and typically considered inert, are able to shield the lateral interfaces of the pentamer. We conclude by discussing our findings in the context of a refined dock-lock model of Aβ fibril elongation, which involves structural disorder for more than one monomer at the growing tip.
Collapse
Affiliation(s)
- Marco Bacci
- University of Zurich , Department of Biochemistry, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
| | - Jiří Vymětal
- University of Zurich , Department of Biochemistry, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
| | - Maja Mihajlovic
- University of Zurich , Department of Biochemistry, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
| | - Amedeo Caflisch
- University of Zurich , Department of Biochemistry, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
| | - Andreas Vitalis
- University of Zurich , Department of Biochemistry, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
| |
Collapse
|
9
|
Dorosh L, Stepanova M. Probing oligomerization of amyloid beta peptide in silico. MOLECULAR BIOSYSTEMS 2017; 13:165-182. [PMID: 27844078 DOI: 10.1039/c6mb00441e] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Aggregation of amyloid β (Aβ) peptide is implicated in fatal Alzheimer's disease, for which no cure is available. Understanding the mechanisms responsible for this aggregation is required in order for therapies to be developed. In an effort to better understand the molecular mechanisms involved in spontaneous aggregation of Aβ peptide, extensive molecular dynamics simulations are reported, and the results are analyzed through a combination of structural biology tools and a novel essential collective dynamics method. Several model systems composed of ten or twelve Aβ17-42 chains in water are investigated, and the influence of metal ions is probed. The results suggest that Aβ monomers tend to aggregate into stable globular-like oligomers with 13-23% of β-sheet content. Two stages of oligomer formation have been identified: quick collapse within the first 40 ns of the simulation, characterized by a decrease in inter-chain separation and build-up of β-sheets, and the subsequent slow relaxation of the oligomer structure. The resulting oligomers comprise a stable, coherently moving sub-aggregate of 6-9 strongly inter-correlated chains. Cu2+ and Fe2+ ions have been found to develop coordination bonds with carboxylate groups of E22, D23 and A42, which remain stable during 200 ns simulations. The presence of Fe2+, and particularly Cu2+ ions, in negatively charged cavities has been found to cause significant changes in the structure and dynamics of the oligomers. The results indicate, in particular, that formation of non-fibrillar oligomers might be involved in early template-free aggregation of Aβ17-42 monomers, with charged species such as Cu2+ or Fe2+ ions playing an important role.
Collapse
Affiliation(s)
- L Dorosh
- Department of Electrical and Computer Engineering, University of Alberta, Edmonton, Alberta, Canada. and National Research Council of Canada, Edmonton, Alberta, Canada
| | - M Stepanova
- Department of Electrical and Computer Engineering, University of Alberta, Edmonton, Alberta, Canada. and National Research Council of Canada, Edmonton, Alberta, Canada and Department of Physics, Astronomy, and Materials Science, Missouri State University, Springfield, MO, USA
| |
Collapse
|
10
|
|
11
|
Irbäck A, Wessén J. Thermodynamics of amyloid formation and the role of intersheet interactions. J Chem Phys 2016; 143:105104. [PMID: 26374063 DOI: 10.1063/1.4930280] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
The self-assembly of proteins into β-sheet-rich amyloid fibrils has been observed to occur with sigmoidal kinetics, indicating that the system initially is trapped in a metastable state. Here, we use a minimal lattice-based model to explore the thermodynamic forces driving amyloid formation in a finite canonical (NVT) system. By means of generalized-ensemble Monte Carlo techniques and a semi-analytical method, the thermodynamic properties of this model are investigated for different sets of intersheet interaction parameters. When the interactions support lateral growth into multi-layered fibrillar structures, an evaporation/condensation transition is observed, between a supersaturated solution state and a thermodynamically distinct state where small and large fibril-like species exist in equilibrium. Intermediate-size aggregates are statistically suppressed. These properties do not hold if aggregate growth is one-dimensional.
Collapse
Affiliation(s)
- Anders Irbäck
- Department of Astronomy and Theoretical Physics, Lund University, Sölvegatan 14A, SE-223 62 Lund, Sweden
| | - Jonas Wessén
- Department of Astronomy and Theoretical Physics, Lund University, Sölvegatan 14A, SE-223 62 Lund, Sweden
| |
Collapse
|
12
|
Nagel-Steger L, Owen MC, Strodel B. An Account of Amyloid Oligomers: Facts and Figures Obtained from Experiments and Simulations. Chembiochem 2016; 17:657-76. [PMID: 26910367 DOI: 10.1002/cbic.201500623] [Citation(s) in RCA: 83] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2015] [Indexed: 12/27/2022]
Abstract
The deposition of amyloid in brain tissue in the context of neurodegenerative diseases involves the formation of intermediate species-termed oligomers-of lower molecular mass and with structures that deviate from those of mature amyloid fibrils. Because these oligomers are thought to be primarily responsible for the subsequent disease pathogenesis, the elucidation of their structure is of enormous interest. Nevertheless, because of the high aggregation propensity and the polydispersity of oligomeric species formed by the proteins or peptides in question, the preparation of appropriate samples for high-resolution structural methods has proven to be rather difficult. This is why theoretical approaches have been of particular importance in gaining insights into possible oligomeric structures for some time. Only recently has it been possible to achieve some progress with regard to the experimentally based structural characterization of defined oligomeric species. Here we discuss how theory and experiment are used to determine oligomer structures and what can be done to improve the integration of the two disciplines.
Collapse
Affiliation(s)
- Luitgard Nagel-Steger
- Institute of Complex Systems: Structural Biochemistry (ICS-6), Forschungszentrum Jülich, 52425, Jülich, Germany.,Institut für Physikalische Biologie, Heinrich-Heine-Universität Düsseldorf, Universitätstrasse 1, 40225, Düsseldorf, Germany
| | - Michael C Owen
- Institute of Complex Systems: Structural Biochemistry (ICS-6), Forschungszentrum Jülich, 52425, Jülich, Germany
| | - Birgit Strodel
- Institute of Complex Systems: Structural Biochemistry (ICS-6), Forschungszentrum Jülich, 52425, Jülich, Germany. .,Institute of Theoretical and Computational Chemistry, Heinrich Heine University Düsseldorf, Universitätstrasse 1, 40225, Düsseldorf, Germany.
| |
Collapse
|
13
|
Emperador A, Sfriso P, Villarreal MA, Gelpí JL, Orozco M. PACSAB: Coarse-Grained Force Field for the Study of Protein–Protein Interactions and Conformational Sampling in Multiprotein Systems. J Chem Theory Comput 2015; 11:5929-38. [DOI: 10.1021/acs.jctc.5b00660] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Agustí Emperador
- Institute for Research in Biomedicine (IRB Barcelona), Baldiri
i Reixac 10, Barcelona 08028, Spain
- Joint BSC-IRB Research Program in Computational Biology, IRB Barcelona, Barcelona 08028, Spain
| | - Pedro Sfriso
- Institute for Research in Biomedicine (IRB Barcelona), Baldiri
i Reixac 10, Barcelona 08028, Spain
- Joint BSC-IRB Research Program in Computational Biology, IRB Barcelona, Barcelona 08028, Spain
| | - Marcos Ariel Villarreal
- Instituto de Investigaciones en Fisicoquímica de Córdoba
- Departamento de Matemática y Física, CONICET-Universidad Nacional de Córdoba, University City, Córdoba 5000, Argentina
| | - Josep Lluis Gelpí
- Institute for Research in Biomedicine (IRB Barcelona), Baldiri
i Reixac 10, Barcelona 08028, Spain
- Joint BSC-IRB Research Program in Computational Biology, IRB Barcelona, Barcelona 08028, Spain
- Barcelona Supercomputing Center, Jordi Girona
29, Barcelona 08034, Spain
- Departament de Bioquímica, Facultat de Biologia, Avgda Diagonal 645, Barcelona 08028, Spain
| | - Modesto Orozco
- Institute for Research in Biomedicine (IRB Barcelona), Baldiri
i Reixac 10, Barcelona 08028, Spain
- Joint BSC-IRB Research Program in Computational Biology, IRB Barcelona, Barcelona 08028, Spain
- Barcelona Supercomputing Center, Jordi Girona
29, Barcelona 08034, Spain
- Departament de Bioquímica, Facultat de Biologia, Avgda Diagonal 645, Barcelona 08028, Spain
| |
Collapse
|
14
|
Tarus B, Tran TT, Nasica-Labouze J, Sterpone F, Nguyen PH, Derreumaux P. Structures of the Alzheimer's Wild-Type Aβ1-40 Dimer from Atomistic Simulations. J Phys Chem B 2015; 119:10478-87. [PMID: 26228450 DOI: 10.1021/acs.jpcb.5b05593] [Citation(s) in RCA: 74] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We have studied the dimer of amyloid beta peptide Aβ of 40 residues by means of all-atom replica exchange molecular dynamics. The Aβ-dimers have been found to be the smallest toxic species in Alzheimer's disease, but their inherent flexibilities have precluded structural characterization by experimental methods. Though the 24-μs-scale simulation reveals a mean secondary structure of 18% β-strand and 10% α helix, we find transient configurations with an unstructured N-terminus and multiple β-hairpins spanning residues 17-21 and 30-36, but the antiparallel and perpendicular peptide orientations are preferred over the parallel organization. Short-lived conformational states also consist of all α topologies, and one compact peptide with β-sheet structure stabilized by a rather extended peptide with α-helical content. Overall, this first all-atom study provides insights into the equilibrium structure of the Aβ1-40 dimer in aqueous solution, opening a new avenue for a comprehensive understanding of the impact of pathogenic and protective mutations in early-stage Alzheimer's disease on a molecular level.
Collapse
Affiliation(s)
- Bogdan Tarus
- Laboratoire de Biochimie Théorique, UPR 9080 CNRS, IBPC, Université Paris Diderot, Sorbonne Paris Cité, 13 Rue Pierre et Marie Curie, 75005 Paris, France
| | - Thanh T Tran
- Laboratoire de Biochimie Théorique, UPR 9080 CNRS, IBPC, Université Paris Diderot, Sorbonne Paris Cité, 13 Rue Pierre et Marie Curie, 75005 Paris, France
| | - Jessica Nasica-Labouze
- Laboratoire de Biochimie Théorique, UPR 9080 CNRS, IBPC, Université Paris Diderot, Sorbonne Paris Cité, 13 Rue Pierre et Marie Curie, 75005 Paris, France
| | - Fabio Sterpone
- Laboratoire de Biochimie Théorique, UPR 9080 CNRS, IBPC, Université Paris Diderot, Sorbonne Paris Cité, 13 Rue Pierre et Marie Curie, 75005 Paris, France
| | - Phuong H Nguyen
- Laboratoire de Biochimie Théorique, UPR 9080 CNRS, IBPC, Université Paris Diderot, Sorbonne Paris Cité, 13 Rue Pierre et Marie Curie, 75005 Paris, France
| | - Philippe Derreumaux
- Laboratoire de Biochimie Théorique, UPR 9080 CNRS, IBPC, Université Paris Diderot, Sorbonne Paris Cité, 13 Rue Pierre et Marie Curie, 75005 Paris, France
| |
Collapse
|
15
|
Nasica-Labouze J, Nguyen PH, Sterpone F, Berthoumieu O, Buchete NV, Coté S, De Simone A, Doig AJ, Faller P, Garcia A, Laio A, Li MS, Melchionna S, Mousseau N, Mu Y, Paravastu A, Pasquali S, Rosenman DJ, Strodel B, Tarus B, Viles JH, Zhang T, Wang C, Derreumaux P. Amyloid β Protein and Alzheimer's Disease: When Computer Simulations Complement Experimental Studies. Chem Rev 2015; 115:3518-63. [PMID: 25789869 DOI: 10.1021/cr500638n] [Citation(s) in RCA: 478] [Impact Index Per Article: 53.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Jessica Nasica-Labouze
- †Laboratoire de Biochimie Théorique, Institut de Biologie Physico-Chimique (IBPC), UPR9080 CNRS, Université Paris Diderot, Sorbonne Paris Cité, 13 rue Pierre et Marie Curie, 75005 Paris, France
| | - Phuong H Nguyen
- †Laboratoire de Biochimie Théorique, Institut de Biologie Physico-Chimique (IBPC), UPR9080 CNRS, Université Paris Diderot, Sorbonne Paris Cité, 13 rue Pierre et Marie Curie, 75005 Paris, France
| | - Fabio Sterpone
- †Laboratoire de Biochimie Théorique, Institut de Biologie Physico-Chimique (IBPC), UPR9080 CNRS, Université Paris Diderot, Sorbonne Paris Cité, 13 rue Pierre et Marie Curie, 75005 Paris, France
| | - Olivia Berthoumieu
- ‡LCC (Laboratoire de Chimie de Coordination), CNRS, Université de Toulouse, Université Paul Sabatier (UPS), Institut National Polytechnique de Toulouse (INPT), 205 route de Narbonne, BP 44099, Toulouse F-31077 Cedex 4, France
| | | | - Sébastien Coté
- ∥Département de Physique and Groupe de recherche sur les protéines membranaires (GEPROM), Université de Montréal, C.P. 6128, succursale Centre-ville, Montréal, Québec H3C 3T5, Canada
| | - Alfonso De Simone
- ⊥Department of Life Sciences, Imperial College London, London SW7 2AZ, United Kingdom
| | - Andrew J Doig
- #Manchester Institute of Biotechnology, University of Manchester, 131 Princess Street, Manchester M1 7DN, United Kingdom
| | - Peter Faller
- ‡LCC (Laboratoire de Chimie de Coordination), CNRS, Université de Toulouse, Université Paul Sabatier (UPS), Institut National Polytechnique de Toulouse (INPT), 205 route de Narbonne, BP 44099, Toulouse F-31077 Cedex 4, France
| | | | - Alessandro Laio
- ○The International School for Advanced Studies (SISSA), Via Bonomea 265, 34136 Trieste, Italy
| | - Mai Suan Li
- ◆Institute of Physics, Polish Academy of Sciences, Al. Lotnikow 32/46, 02-668 Warsaw, Poland.,¶Institute for Computational Science and Technology, SBI Building, Quang Trung Software City, Tan Chanh Hiep Ward, District 12, Ho Chi Minh City, Vietnam
| | - Simone Melchionna
- ⬠Instituto Processi Chimico-Fisici, CNR-IPCF, Consiglio Nazionale delle Ricerche, 00185 Roma, Italy
| | | | - Yuguang Mu
- ▲School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, 637551 Singapore
| | - Anant Paravastu
- ⊕National High Magnetic Field Laboratory, 1800 East Paul Dirac Drive, Tallahassee, Florida 32310, United States
| | - Samuela Pasquali
- †Laboratoire de Biochimie Théorique, Institut de Biologie Physico-Chimique (IBPC), UPR9080 CNRS, Université Paris Diderot, Sorbonne Paris Cité, 13 rue Pierre et Marie Curie, 75005 Paris, France
| | | | - Birgit Strodel
- △Institute of Complex Systems: Structural Biochemistry (ICS-6), Forschungszentrum Jülich GmbH, 52425 Jülich, Germany
| | - Bogdan Tarus
- †Laboratoire de Biochimie Théorique, Institut de Biologie Physico-Chimique (IBPC), UPR9080 CNRS, Université Paris Diderot, Sorbonne Paris Cité, 13 rue Pierre et Marie Curie, 75005 Paris, France
| | - John H Viles
- ▼School of Biological and Chemical Sciences, Queen Mary University of London, London E1 4NS, United Kingdom
| | - Tong Zhang
- †Laboratoire de Biochimie Théorique, Institut de Biologie Physico-Chimique (IBPC), UPR9080 CNRS, Université Paris Diderot, Sorbonne Paris Cité, 13 rue Pierre et Marie Curie, 75005 Paris, France.,▲School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, 637551 Singapore
| | | | - Philippe Derreumaux
- †Laboratoire de Biochimie Théorique, Institut de Biologie Physico-Chimique (IBPC), UPR9080 CNRS, Université Paris Diderot, Sorbonne Paris Cité, 13 rue Pierre et Marie Curie, 75005 Paris, France.,□Institut Universitaire de France, 75005 Paris, France
| |
Collapse
|
16
|
Ning L, Wang Q, Zheng Y, Liu H, Yao X. Effects of the A117V mutation on the folding and aggregation of palindromic sequences (PrP113–120) in prion: insights from replica exchange molecular dynamics simulations. MOLECULAR BIOSYSTEMS 2015; 11:647-55. [DOI: 10.1039/c4mb00546e] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The A117V mutation enhances the aggregation propensity of the palindromic sequences in prion protein.
Collapse
Affiliation(s)
- Lulu Ning
- State Key Laboratory of Applied Organic Chemistry and Department of Chemistry
- Lanzhou University
- Lanzhou 730000
- China
| | - Qianqian Wang
- School of Pharmacy
- Lanzhou University
- Lanzhou 730000
- China
| | - Yang Zheng
- State Key Laboratory of Applied Organic Chemistry and Department of Chemistry
- Lanzhou University
- Lanzhou 730000
- China
| | - Huanxiang Liu
- State Key Laboratory of Applied Organic Chemistry and Department of Chemistry
- Lanzhou University
- Lanzhou 730000
- China
- School of Pharmacy
| | - Xiaojun Yao
- State Key Laboratory of Applied Organic Chemistry and Department of Chemistry
- Lanzhou University
- Lanzhou 730000
- China
- State Key Laboratory of Quality Research in Chinese Medicine
| |
Collapse
|
17
|
Pouplana R, Campanera JM. Energetic contributions of residues to the formation of early amyloid-β oligomers. Phys Chem Chem Phys 2014; 17:2823-37. [PMID: 25503571 DOI: 10.1039/c4cp04544k] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Low-weight amyloid-β (Aβ) oligomers formed at early stages of oligomerization rather than fibril assemblies seem to be the toxic components that drive neurodegeneration in Alzheimer's disease. Unfortunately, detailed knowledge of the structure of these early oligomers at the residue level is not yet available. In this study, we performed all-atom explicit solvent molecular dynamics simulations to examine the oligomerization process of Aβ10-35 monomers when forming dimers, trimers, tetramers and octamers, with four independent simulations of a total simulated time of 3 μs for each oligomer system. The decomposition of the stability free energy by MM-GBSA methodology allowed us to unravel the network of energetic interactions that stabilize such oligomers. The contribution of the intermonomeric van der Waals term is the most significant energy feature of the oligomerization process, consistent with the so-called hydrophobic effect. Furthermore, the decomposition of the stability free energy into residues and residue-pairwise terms revealed that it is mainly apolar interactions between the three specific hydrophobic fragments 31-35 (C-terminal region), 17-20 (central hydrophobic core) and 12-14 (N-terminal region) that are responsible for such a favourable effect. The conformation in which the hydrophobic cthr-chc interaction is oriented perpendicularly is particularly important. We propose three other model substructures that favour the oligomerization process and can thus be considered as molecular targets for future inhibitors. Understanding Aβ oligomerization at the residue level could lead to more efficient design of inhibitors of this process.
Collapse
Affiliation(s)
- R Pouplana
- Departament de Fisicoquímica, Facultat de Farmàcia, Universitat de Barcelona, Av. Joan XXIII, s/n, Diagonal Sud, 08028, Barcelona, Catalonia, Spain.
| | | |
Collapse
|
18
|
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
|
19
|
Abstract
![]()
Experimentally, the solubility of
oligoglycines in water decreases
as its length increases. Computationally, the free energy of solvation
becomes more favorable with chain length for short (n = 1–5) oligoglycines. We present results of large scale simulations
with over 600 pentaglycines at varying concentrations in explicit
solvent to consider the mechanism of aggregation. The solubility limit
of Gly5 for the force field used was calculated and compared
with experimental values. We find that intermolecular interactions
between pentaglycines are favored over interactions between glycine
and water, leading to their aggregation. However, the interaction
driving peptide associations, liquid–liquid phase separation,
are not predominantly hydrogen bonding. Instead, non-hydrogen bonding
interactions between partially charged atoms on the peptide backbone
allow the formation of dipole–dipole and charge layering correlations
that mechanistically stabilize the formation of large, stable peptide
clusters.
Collapse
Affiliation(s)
- Deepti Karandur
- Structural and Computational Biology and Molecular Biophysics, Baylor College of Medicine , Houston, Texas 77030, United States
| | | | | |
Collapse
|
20
|
Socher E, Sticht H, Horn AHC. The conformational stability of nonfibrillar amyloid-β peptide oligomers critically depends on the C-terminal peptide length. ACS Chem Neurosci 2014; 5:161-7. [PMID: 24494584 DOI: 10.1021/cn400208r] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
The amyloid-β (Aβ) peptide is one key molecule in the pathogenesis of Alzheimer's disease. We investigated the conformational stability of a nonfibrillar tetrameric Aβ structure by molecular dynamics (MD) simulations revealing that the stability of the Aβ tetramer depends critically on the C-terminal length. In contrast to the Aβ17-40 tetramer, which proved to be instable, the simulations demonstrate structural integrity of the Aβ17-42 and Aβ17-43 tetramers. These differences in stability can be attributed to an extension of the middle strand of a three-stranded antiparallel β sheet through residues 41-43, only present in the longer Aβ species that aggregate faster and are more neurotoxic. Additional MD simulations demonstrate that this higher stability is also present in the monomers forming the tetramer. In conclusion, our findings suggest the existence of a nonfibrillar oligomer topology that is significantly more stable for the longer Aβ species, thus offering a structural explanation for their higher neurotoxicity.
Collapse
Affiliation(s)
- Eileen Socher
- Bioinformatik,
Institut für Biochemie, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Fahrstraße 17, 91054 Erlangen, Germany
| | - Heinrich Sticht
- Bioinformatik,
Institut für Biochemie, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Fahrstraße 17, 91054 Erlangen, Germany
| | - Anselm H. C. Horn
- Bioinformatik,
Institut für Biochemie, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Fahrstraße 17, 91054 Erlangen, Germany
| |
Collapse
|
21
|
Ning L, Guo J, Bai Q, Jin N, Liu H, Yao X. Structural diversity and initial oligomerization of PrP106-126 studied by replica-exchange and conventional molecular dynamics simulations. PLoS One 2014; 9:e87266. [PMID: 24586266 PMCID: PMC3929351 DOI: 10.1371/journal.pone.0087266] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2013] [Accepted: 12/24/2013] [Indexed: 12/15/2022] Open
Abstract
Prion diseases are marked by cerebral accumulation of the abnormal isoform of the prion protein. A fragment of prion protein composed of residues 106–126 (PrP106–126) exhibits similar properties to full length prion and plays a key role in the conformational conversion from cellular prion to its pathogenic pattern. Soluble oligomers of PrP106–126 have been proposed to be responsible for neurotoxicity. However, the monomeric conformational space and initial oligomerization of PrP106–126 are still obscure, which are very important for understanding the conformational conversion of PrP106–126. In this study, replica exchange molecular dynamics simulations were performed to investigate monomeric and dimeric states of PrP106–126 in implicit solvent. The structural diversity of PrP106–126 was observed and this peptide did not acquire stable structure. The dimeric PrP106–126 also displayed structural diversity and hydrophobic interaction drove the dimerization. To further study initial oligomerization of PrP106–126, 1 µs conventional molecular dynamics simulations of trimer and tetramer formation were carried out in implicit solvent. We have observed the spontaneous formation of several basic oligomers and stable oligomers with high β-sheet contents were sampled in the simulations of trimer and tetramer formation. The β-hairpin formed in hydrophobic tail of PrP106–126 with residues 118–120 in turn may stabilize these oligomers and seed the formation oligomers. This study can provide insight into the detailed information about the structure of PrP106–126 and the dynamics of aggregation of monomeric PrP106–126 into oligomers in atomic level.
Collapse
Affiliation(s)
- Lulu Ning
- State Key Laboratory of Applied Organic Chemistry and Department of Chemistry, Lanzhou University, Lanzhou, China
| | - Jingjing Guo
- State Key Laboratory of Applied Organic Chemistry and Department of Chemistry, Lanzhou University, Lanzhou, China
- School of Pharmacy, Lanzhou University, Lanzhou, China
| | - Qifeng Bai
- State Key Laboratory of Applied Organic Chemistry and Department of Chemistry, Lanzhou University, Lanzhou, China
| | | | - Huanxiang Liu
- State Key Laboratory of Applied Organic Chemistry and Department of Chemistry, Lanzhou University, Lanzhou, China
- School of Pharmacy, Lanzhou University, Lanzhou, China
- * E-mail: (HL); (XY)
| | - Xiaojun Yao
- State Key Laboratory of Applied Organic Chemistry and Department of Chemistry, Lanzhou University, Lanzhou, China
- State Key Lab for Quality Research in Chinese Medicines, Macau Institute for Applied Research in Medicine and Health, Macau University of Science and Technology, Taipa, Macau, China
- * E-mail: (HL); (XY)
| |
Collapse
|
22
|
Abeln S, Vendruscolo M, Dobson CM, Frenkel D. A simple lattice model that captures protein folding, aggregation and amyloid formation. PLoS One 2014; 9:e85185. [PMID: 24454816 PMCID: PMC3893179 DOI: 10.1371/journal.pone.0085185] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2013] [Accepted: 12/03/2013] [Indexed: 01/01/2023] Open
Abstract
The ability of many proteins to convert from their functional soluble state to amyloid fibrils can be attributed to inter-molecular beta strand formation. Such amyloid formation is associated with neurodegenerative disorders like Alzheimer's and Parkinson's. Molecular modelling can play a key role in providing insight into the factors that make proteins prone to fibril formation. However, fully atomistic models are computationally too expensive to capture the length and time scales associated with fibril formation. As the ability to form fibrils is the rule rather than the exception, much insight can be gained from the study of coarse-grained models that capture the key generic features associated with amyloid formation. Here we present a simple lattice model that can capture both protein folding and beta strand formation. Unlike standard lattice models, this model explicitly incorporates the formation of hydrogen bonds and the directionality of side chains. The simplicity of our model makes it computationally feasible to investigate the interplay between folding, amorphous aggregation and fibril formation, and maintains the capability of classic lattice models to simulate protein folding with high specificity. In our model, the folded proteins contain structures that resemble naturally occurring beta-sheets, with alternating polar and hydrophobic amino acids. Moreover, fibrils with intermolecular cross-beta strand conformations can be formed spontaneously out of multiple short hydrophobic peptide sequences. Both the formation of hydrogen bonds in folded structures and in fibrils is strongly dependent on the amino acid sequence, indicating that hydrogen-bonding interactions alone are not strong enough to initiate the formation of beta sheets. This result agrees with experimental observations that beta sheet and amyloid formation is strongly sequence dependent, with hydrophobic sequences being more prone to form such structures. Our model should open the way to a systematic study of the interplay between the factors that lead to amyloid formation.
Collapse
Affiliation(s)
- Sanne Abeln
- IBIVU - Deptartment of Computer Science, VU University, Amsterdam, The Netherlands
| | - Michele Vendruscolo
- Deptartment of Chemistry, University of Cambridge, Cambridge, United Kingdom
| | | | - Daan Frenkel
- Deptartment of Chemistry, University of Cambridge, Cambridge, United Kingdom
| |
Collapse
|
23
|
Qi R, Luo Y, Ma B, Nussinov R, Wei G. Conformational distribution and α-helix to β-sheet transition of human amylin fragment dimer. Biomacromolecules 2014; 15:122-31. [PMID: 24313776 PMCID: PMC6429924 DOI: 10.1021/bm401406e] [Citation(s) in RCA: 64] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Experiments suggested that the fibrillation of the 11-25 fragment (hIAPP(11-25)) of human islet amyloid polypeptide (hIAPP or amylin) involves the formation of transient α-helical intermediates, followed by conversion to β-sheet-rich structure. However, atomic details of α-helical intermediates and the transition mechanism are mostly unknown. We investigated the structural properties of the monomer and dimer in atomistic detail by replica exchange molecular dynamics (REMD) simulations. Transient α-helical monomers and dimers were both observed in the REMD trajectories. Our calculated H(α) chemical shifts based on the monomer REMD run are in agreement with the solution-state NMR experimental observations. Multiple 300 ns MD simulations at 310 K show that α-helix-to-β-sheet transition follows two mechanisms: the first involved direct transition of the random coil part of the helical conformation into antiparallel β-sheet, and in the second, the α-helical conformation unfolded and converted into antiparallel β-sheet. In both mechanisms, the α-helix-to-β-sheet transition occurred via random coil, and the transition was accompanied by an increase of interpeptide contacts. In addition, our REMD simulations revealed different temperature dependencies of helical and β-structures. Comparison with experimental data suggests that the propensity for hIAPP(11-25) to form α-helices and amyloid structures is concentration- and temperature-dependent.
Collapse
Affiliation(s)
- Ruxi Qi
- State Key Laboratory of Surface Physics, Key Laboratory for Computational Physical Sciences (MOE), and Department of Physics, Fudan University , Shanghai, China
| | | | | | | | | |
Collapse
|
24
|
Meral D, Urbanc B. Discrete molecular dynamics study of oligomer formation by N-terminally truncated amyloid β-protein. J Mol Biol 2013; 425:2260-75. [PMID: 23500806 PMCID: PMC3665754 DOI: 10.1016/j.jmb.2013.03.010] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2013] [Accepted: 03/05/2013] [Indexed: 01/09/2023]
Abstract
In Alzheimer's disease (AD), amyloid β-protein (Aβ) self-assembles into toxic oligomers. Of the two predominant Aβ alloforms, Aβ1-40 and Aβ1-42, the latter is particularly strongly linked to AD. N-terminally truncated and pyroglutamated Aβ peptides were recently shown to seed Aβ aggregation and contribute significantly to Aβ-mediated toxicity, yet their folding and assembly were not explored computationally. Discrete molecular dynamics approach previously captured in vitro-derived distinct Aβ1-40 and Aβ1-42 oligomer size distributions and predicted that the more toxic Aβ1-42 oligomers had more flexible and solvent-exposed N-termini than Aβ1-40 oligomers. Here, we examined oligomer formation of Aβ3-40, Aβ3-42, Aβ11-40, and Aβ11-42 by the discrete molecular dynamics approach. The four N-terminally truncated peptides showed increased oligomerization propensity relative to the full-length peptides, consistent with in vitro findings. Conformations formed by Aβ3-40/42 had significantly more flexible and solvent-exposed N-termini than Aβ1-40/42 conformations. In contrast, in Aβ11-40/42 conformations, the N-termini formed more contacts and were less accessible to the solvent. The compactness of the Aβ11-40/42 conformations was in part facilitated by Val12. Two single amino acid substitutions that reduced and abolished hydrophobicity at position 12, respectively, resulted in a proportionally increased structural variability. Our results suggest that Aβ11-40 and Aβ11-42 oligomers might be less toxic than Aβ1-40 and Aβ1-42 oligomers and offer a plausible explanation for the experimentally observed increased toxicity of Aβ3-40 and Aβ3-42 and their pyroglutamated forms.
Collapse
Affiliation(s)
- Derya Meral
- Department of Physics, Drexel University, Philadelphia, PA 19104, USA
| | - Brigita Urbanc
- Department of Physics, Drexel University, Philadelphia, PA 19104, USA
| |
Collapse
|
25
|
Ni B, Baumketner A. Reduced atomic pair-interaction design (RAPID) model for simulations of proteins. J Chem Phys 2013; 138:064102. [PMID: 23425456 PMCID: PMC3579890 DOI: 10.1063/1.4790160] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2012] [Accepted: 01/18/2013] [Indexed: 12/15/2022] Open
Abstract
Increasingly, theoretical studies of proteins focus on large systems. This trend demands the development of computational models that are fast, to overcome the growing complexity, and accurate, to capture the physically relevant features. To address this demand, we introduce a protein model that uses all-atom architecture to ensure the highest level of chemical detail while employing effective pair potentials to represent the effect of solvent to achieve the maximum speed. The effective potentials are derived for amino acid residues based on the condition that the solvent-free model matches the relevant pair-distribution functions observed in explicit solvent simulations. As a test, the model is applied to alanine polypeptides. For the chain with 10 amino acid residues, the model is found to reproduce properly the native state and its population. Small discrepancies are observed for other folding properties and can be attributed to the approximations inherent in the model. The transferability of the generated effective potentials is investigated in simulations of a longer peptide with 25 residues. A minimal set of potentials is identified that leads to qualitatively correct results in comparison with the explicit solvent simulations. Further tests, conducted for multiple peptide chains, show that the transferable model correctly reproduces the experimentally observed tendency of polyalanines to aggregate into β-sheets more strongly with the growing length of the peptide chain. Taken together, the reported results suggest that the proposed model could be used to succesfully simulate folding and aggregation of small peptides in atomic detail. Further tests are needed to assess the strengths and limitations of the model more thoroughly.
Collapse
Affiliation(s)
- Boris Ni
- Department of Physics and Optical Science, University of North Carolina Charlotte, 9201 University City Blvd., Charlotte, North Carolina 28262, USA
| | | |
Collapse
|
26
|
Pannuzzo M, Milardi D, Raudino A, Karttunen M, La Rosa C. Analytical model and multiscale simulations of Aβ peptide aggregation in lipid membranes: towards a unifying description of conformational transitions, oligomerization and membrane damage. Phys Chem Chem Phys 2013; 15:8940-51. [DOI: 10.1039/c3cp44539a] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
|
27
|
Kim S, Klimov DK. Binding to the lipid monolayer induces conformational transition in Aβ monomer. J Mol Model 2012; 19:737-50. [DOI: 10.1007/s00894-012-1596-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2012] [Accepted: 09/03/2012] [Indexed: 12/11/2022]
|
28
|
Curcó D, Michaux C, Roussel G, Tinti E, Perpète EA, Alemán C. Stochastic simulation of structural properties of natively unfolded and denatured proteins. J Mol Model 2012; 18:4503-16. [DOI: 10.1007/s00894-012-1456-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2012] [Accepted: 05/02/2012] [Indexed: 01/05/2023]
|
29
|
Barz B, Urbanc B. Dimer formation enhances structural differences between amyloid β-protein (1-40) and (1-42): an explicit-solvent molecular dynamics study. PLoS One 2012; 7:e34345. [PMID: 22509291 PMCID: PMC3324527 DOI: 10.1371/journal.pone.0034345] [Citation(s) in RCA: 89] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2011] [Accepted: 02/26/2012] [Indexed: 11/18/2022] Open
Abstract
Amyloid β-protein (Aβ) is central to the pathology of Alzheimer's disease. A 5% difference in the primary structure of the two predominant alloforms, Aβ(1-40) and Aβ(1-42), results in distinct assembly pathways and toxicity properties. Discrete molecular dynamics (DMD) studies of Aβ(1-40) and Aβ(1-42) assembly resulted in alloform-specific oligomer size distributions consistent with experimental findings. Here, a large ensemble of DMD-derived Aβ(1-40) and Aβ(1-42) monomers and dimers was subjected to fully atomistic molecular dynamics (MD) simulations using the OPLS-AA force field combined with two water models, SPCE and TIP3P. The resulting all-atom conformations were slightly larger, less compact, had similar turn and lower β-strand propensities than those predicted by DMD. Fully atomistic Aβ(1-40) and Aβ(1-42) monomers populated qualitatively similar free energy landscapes. In contrast, the free energy landscape of Aβ(1-42) dimers indicated a larger conformational variability in comparison to that of Aβ(1-40) dimers. Aβ(1-42) dimers were characterized by an increased flexibility in the N-terminal region D1-R5 and a larger solvent exposure of charged amino acids relative to Aβ(1-40) dimers. Of the three positively charged amino acids, R5 was the most and K16 the least involved in salt bridge formation. This result was independent of the water model, alloform, and assembly state. Overall, salt bridge propensities increased upon dimer formation. An exception was the salt bridge propensity of K28, which decreased upon formation of Aβ(1-42) dimers and was significantly lower than in Aβ(1-40) dimers. The potential relevance of the three positively charged amino acids in mediating the Aβ oligomer toxicity is discussed in the light of available experimental data.
Collapse
Affiliation(s)
- Bogdan Barz
- Physics Department, Drexel University, Philadelphia, Pennsylvania, United States of America
| | - Brigita Urbanc
- Physics Department, Drexel University, Philadelphia, Pennsylvania, United States of America
| |
Collapse
|
30
|
Zhao J, Wang Q, Liang G, Zheng J. Molecular dynamics simulations of low-ordered alzheimer β-amyloid oligomers from dimer to hexamer on self-assembled monolayers. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2011; 27:14876-14887. [PMID: 22077332 DOI: 10.1021/la2027913] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Accumulation of small soluble oligomers of amyloid-β (Aβ) in the human brain is thought to play an important pathological role in Alzheimer's disease. The interaction of these Aβ oligomers with cell membrane and other artificial surfaces is important for the understanding of Aβ aggregation and toxicity mechanisms. Here, we present a series of exploratory molecular dynamics (MD) simulations to study the early adsorption and conformational change of Aβ oligomers from dimer to hexamer on three different self-assembled monolayers (SAMs) terminated with CH(3), OH, and COOH groups. Within the time scale of MD simulations, the conformation, orientation, and adsorption of Aβ oligomers on the SAMs is determined by complex interplay among the size of Aβ oligomers, the surface chemistry of the SAMs, and the structure and dynamics of interfacial waters. Energetic analysis of Aβ adsorption on the SAMs reveals that Aβ adsorption on the SAMs is a net outcome of different competitions between dominant hydrophobic Aβ-CH(3)-SAM interactions and weak CH(3)-SAM-water interactions, between dominant electrostatic Aβ-COOH-SAM interactions and strong COOH-SAM-water interactions, and between comparable hydrophobic and electrostatic Aβ-OH-SAM interactions and strong OH-SAM-water interactions. Atomic force microscopy images also confirm that all of three SAMs can induce the adsorption and polymerization of Aβ oligomers. Structural analysis of Aβ oligomers on the SAMs shows a dramatic increase in structural stability and β-sheet content from dimer to trimer, suggesting that Aβ trimer could act as seeds for Aβ polymerization on the SAMs. This work provides atomic-level understanding of Aβ peptides at interface.
Collapse
Affiliation(s)
- Jun Zhao
- Department of Chemical and Biomolecular Engineering, The University of Akron, Akron, Ohio 44325, USA
| | | | | | | |
Collapse
|
31
|
Convertino M, Vitalis A, Caflisch A. Disordered binding of small molecules to Aβ(12-28). J Biol Chem 2011; 286:41578-41588. [PMID: 21969380 PMCID: PMC3308868 DOI: 10.1074/jbc.m111.285957] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2011] [Revised: 09/23/2011] [Indexed: 11/06/2022] Open
Abstract
In recent years, an increasing number of small molecules and short peptides have been identified that interfere with aggregation and/or oligomerization of the Alzheimer β-amyloid peptide (Aβ). Many of them possess aromatic moieties, suggesting a dominant role for those in interacting with Aβ along various stages of the aggregation process. In this study, we attempt to elucidate whether interactions of such aromatic inhibitors with monomeric Aβ(12-28) point to a common mechanism of action by performing atomistic molecular dynamics simulations at equilibrium. Our results suggest that, independently of the presence of inhibitors, monomeric Aβ(12-28) populates a partially collapsed ensemble that is largely devoid of canonical secondary structure at 300 K and neutral pH. The small molecules have different affinities for Aβ(12-28) that can be partially rationalized by the balance of aromatic and charged moieties constituting the molecules. There are no predominant binding modes, although aggregation inhibitors preferentially interact with the N-terminal portion of the fragment (residues 13-20). Analysis of the free energy landscape of Aβ(12-28) reveals differences highlighted by altered populations of a looplike conformer in the presence of inhibitors. We conclude that intrinsic disorder of Aβ persists at the level of binding small molecules and that inhibitors can significantly alter properties of monomeric Aβ via multiple routes of differing specificity.
Collapse
Affiliation(s)
- Marino Convertino
- Department of Biochemistry, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
| | - Andreas Vitalis
- Department of Biochemistry, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland.
| | - Amedeo Caflisch
- Department of Biochemistry, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland.
| |
Collapse
|
32
|
Lockhart C, Kim S, Kumar R, Klimov DK. Does amino acid sequence determine the properties of Aβ dimer? J Chem Phys 2011; 135:035103. [PMID: 21787025 DOI: 10.1063/1.3610427] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The effect of random reshuffling of amino acids on the properties of dimers formed by Aβ peptides is studied using replica exchange molecular dynamics and united atom implicit solvent model. We show that thermodynamics of dimer assembly and the dimer globule-like state are not affected by sequence permutation. Furthermore, sequence reshuffling does not change the distributions of non-local interactions and, to a large extent, amino acids in the dimer volume. To rationalize these results, we demonstrate that Gaussian statistics applies surprisingly well to the end-to-end distances of the peptides in the dimer implying that non-bonded interactions between distant along the chain amino acids are effectively screened. This observation suggests that peptides in the dimer behave as ideal chains in polymer melt, in which amino acids lose their "identity" and therefore the memory of sequence position. As a result large-scale properties of the dimer become universal or sequence independent. Comparison of our simulations with the prior theoretical studies and their implications for experiments are discussed.
Collapse
Affiliation(s)
- Christopher Lockhart
- School of Systems Biology, George Mason University, Manassas, Virginia 20110, USA
| | | | | | | |
Collapse
|
33
|
Tuffery P, Derreumaux P. Flexibility and binding affinity in protein-ligand, protein-protein and multi-component protein interactions: limitations of current computational approaches. J R Soc Interface 2011; 9:20-33. [PMID: 21993006 DOI: 10.1098/rsif.2011.0584] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The recognition process between a protein and a partner represents a significant theoretical challenge. In silico structure-based drug design carried out with nothing more than the three-dimensional structure of the protein has led to the introduction of many compounds into clinical trials and numerous drug approvals. Central to guiding the discovery process is to recognize active among non-active compounds. While large-scale computer simulations of compounds taken from a library (virtual screening) or designed de novo are highly desirable in the post-genomic area, many technical problems remain to be adequately addressed. This article presents an overview and discusses the limits of current computational methods for predicting the correct binding pose and accurate binding affinity. It also presents the performances of the most popular algorithms for exploring binary and multi-body protein interactions.
Collapse
Affiliation(s)
- Pierre Tuffery
- INSERM UMR-S 973, Université Paris Diderot, 35 rue Hélène Brion, 75251 Paris cedex, France
| | | |
Collapse
|
34
|
Kim S, Chang WE, Kumar R, Klimov DK. Naproxen interferes with the assembly of Aβ oligomers implicated in Alzheimer's disease. Biophys J 2011; 100:2024-32. [PMID: 21504739 DOI: 10.1016/j.bpj.2011.02.044] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2010] [Revised: 02/15/2011] [Accepted: 02/24/2011] [Indexed: 12/23/2022] Open
Abstract
Experimental and epidemiological studies have shown that the nonsteroidal antiinflammatory drug naproxen may be useful in the treatment of Alzheimer's disease. To investigate the interactions of naproxen with Aβ dimers, which are the smallest cytotoxic aggregated Aβ peptide species, we use united atom implicit solvent model and exhaustive replica exchange molecular dynamics. We show that naproxen ligands bind to Aβ dimer and penetrate its volume interfering with the interpeptide interactions. As a result naproxen induces a destabilizing effect on Aβ dimer. By comparing the free-energy landscapes of naproxen interactions with Aβ dimers and fibrils, we conclude that this ligand has stronger antiaggregation potential against Aβ fibrils rather than against dimers. The analysis of naproxen binding energetics shows that the location of ligand binding sites in Aβ dimer is dictated by the Aβ amino acid sequence. Comparison of the in silico findings with experimental observations reveals potential limitations of naproxen as an effective therapeutic agent in the treatment of Alzheimer's disease.
Collapse
Affiliation(s)
- Seongwon Kim
- School of Systems Biology, George Mason University, Manassas, Virginia, USA
| | | | | | | |
Collapse
|
35
|
Kim BH, Palermo NY, Lovas S, Zaikova T, Keana JFW, Lyubchenko YL. Single-molecule atomic force microscopy force spectroscopy study of Aβ-40 interactions. Biochemistry 2011; 50:5154-62. [PMID: 21553928 DOI: 10.1021/bi200147a] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Misfolding and aggregation of amyloid β-40 (Aβ-40) peptide play key roles in the development of Alzheimer's disease (AD). However, very little is known about the molecular mechanisms underlying these molecular processes. We developed a novel experimental approach that can directly probe aggregation-prone states of proteins and their interactions. In this approach, the proteins are anchored to the surface of the atomic force microscopy substrate (mica) and the probe, and the interaction between anchored molecules is measured in the approach-retraction cycles. We used dynamic force spectroscopy (DFS) to measure the stability of transiently formed dimers. One of the major findings from DFS analysis of α-synuclein (α-Syn) is that dimeric complexes formed by misfolded α-Syn protein are very stable and dissociate over a range of seconds. This differs markedly from the dynamics of monomers, which occurs on a microsecond to nanosecond time scale. Here we applied the same approach to quantitatively characterize interactions of Aβ-40 peptides over a broad range of pH values. These studies showed that misfolded dimers are characterized by lifetimes in the range of seconds. This value depends on pH and varies between 2.7 s for pH 2.7 and 0.1 s for pH 7, indicating that the aggregation properties of Aβ-40 are modulated by the environmental conditions. The analysis of the contour lengths revealed the existence of various pathways for dimer dissociation, suggesting that dimers with different conformations are formed. These structural variations result in different aggregation pathways, leading to different types of oligomers and higher-order aggregates, including fibrils.
Collapse
Affiliation(s)
- Bo-Hyun Kim
- Department of Pharmaceutical Sciences, University of Nebraska Medical Center, NE, USA
| | | | | | | | | | | |
Collapse
|
36
|
Velez-Vega C, Escobedo FA. Characterizing the structural behavior of selected Aβ-42 monomers with different solubilities. J Phys Chem B 2011; 115:4900-10. [PMID: 21486050 DOI: 10.1021/jp1086575] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The conformational behavior of the wild-type amyloid β-42 (Aβ-42) monomer and two of its mutants was explored via all-atom replica exchange molecular dynamics simulations in explicit solvent, to identify structural features that may promote or deter early-stage oligomerization. The markers used for this purpose indicate that while the three peptides are relatively flexible they have distinct preferential structures and degree of rigidity. In particular, we found that one mutant that remains in the monomeric state in experiments displays a characteristic N-terminal structure that significantly enhances its rigidity. This finding is consistent with various studies that have detected a reduction in oligomerization frequency and Aβ-related toxicity upon sequence-specific antibody or ligand binding to the N-terminal tail of wild-type monomers, likely leading to the stabilization of this region. In general, our results highlight a potential role of the N-terminal segment on Aβ oligomerization and give insights into specific interactions that may be responsible for promoting the pronounced structural changes observed upon introducing point mutations on the wild-type Aβ-42 peptide.
Collapse
Affiliation(s)
- Camilo Velez-Vega
- School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, New York 14853, USA
| | | |
Collapse
|
37
|
Spill YG, Pasquali S, Derreumaux P. Impact of Thermostats on Folding and Aggregation Properties of Peptides Using the Optimized Potential for Efficient Structure Prediction Coarse-Grained Model. J Chem Theory Comput 2011; 7:1502-10. [DOI: 10.1021/ct100619p] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Affiliation(s)
- Yannick G. Spill
- Laboratoire de Biochimie Théorique, UPR 9080 CNRS et Université Paris Diderot (Paris 7), Institut de Biologie Physico Chimique, 13 rue Pierre et Marie Curie, 75005 Paris, France
| | - Samuela Pasquali
- Laboratoire de Biochimie Théorique, UPR 9080 CNRS et Université Paris Diderot (Paris 7), Institut de Biologie Physico Chimique, 13 rue Pierre et Marie Curie, 75005 Paris, France
| | - Philippe Derreumaux
- Laboratoire de Biochimie Théorique, UPR 9080 CNRS et Université Paris Diderot (Paris 7), Institut de Biologie Physico Chimique, 13 rue Pierre et Marie Curie, 75005 Paris, France
| |
Collapse
|
38
|
Lu Y, Wei G, Derreumaux P. Effects of G33A and G33I mutations on the structures of monomer and dimer of the amyloid-β fragment 29-42 by replica exchange molecular dynamics simulations. J Phys Chem B 2010; 115:1282-8. [PMID: 21186801 DOI: 10.1021/jp110269a] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The early formed oligomers of amyloid-β proteins with 40 and 42 amino acids are believed to be the culprits of Alzheimer's disease. Aβ1-42 peptides with alanine and isoleucine mutations of glycine 33 are known to be much less toxic than the wild-type Aβ1-42 and promote the aggregation process in vitro. The fragment Aβ29-42 has also been shown to form fibrils, disrupt Aβ1-42 oligomerization, and inhibit Aβ1-42-induced neurotoxicity. As a first step toward understanding the impact of G33A and G33I mutations on the earliest steps along the Aβ1-42 aggregation pathway, we have studied the structures of the monomer and dimer of Aβ29-42 and its two G33 variants using coarse-grained replica exchange molecular dynamics simulations. These simulations, totaling 15 μs, indicate that both substitutions impact the conformational ensemble of Aβ29-42. For the monomer, the population of the β-hairpin is high for wild-type Aβ29-42, but marginal for Aβ29-42 G33I mutant. The three dimers are also stabilized by different patterns of interaction. The data are discussed in terms of the differences in the aggregation characteristics between wild-type Aβ1-42 and its two G33A and G33I variants.
Collapse
Affiliation(s)
- Yan Lu
- State Key Laboratory of Surface Physics, Department of Physics, Fudan University, Shanghai, China
| | | | | |
Collapse
|