@article {2020|2125, title = {Impact of the Astaxanthin, Betanin, and EGCG Compounds on Small Oligomers of Amyloid Aβ Peptide.}, journal = {J Chem Inf Model}, volume = {60}, year = {2020}, month = {2020 Mar 23}, pages = {1399-1408}, abstract = {

There is experimental evidence that the astaxanthin, betanin, and epigallocatechin-3-gallate (EGCG) compounds slow down the aggregation kinetics and the toxicity of the amyloid-β (Aβ) peptide. How these inhibitors affect the self-assembly at the atomic level remains elusive. To address this issue, we have performed for each ligand atomistic replica exchange molecular dynamic (REMD) simulations in an explicit solvent of the Aβ trimer from the U-shape conformation and MD simulations starting from Aβ dimer and tetramer structures characterized by different intra- and interpeptide conformations. We find that the three ligands have similar binding free energies on small Aβ oligomers but very distinct transient binding sites that will affect the aggregation of larger assemblies and fibril elongation of the Aβ peptide.

}, issn = {1549-960X}, doi = {10.1021/acs.jcim.9b01074}, author = {Minh Hung, Huynh and Nguyen, Minh Tho and Tran, Phuong-Thao and Truong, Vi Khanh and Chapman, James and Quynh Anh, Le Huu and Philippe Derreumaux and Vu, Van V and Ngo, Son Tung} } @article {2019|2127, title = {C-Terminal Plays as the Possible Nucleation of the Self-Aggregation of the S-Shape Aβ Tetramer in Solution: Intensive MD Study.}, journal = {ACS Omega}, volume = {4}, year = {2019}, month = {2019 Jun 30}, pages = {11066-11073}, abstract = {

Amyloid beta (Aβ) peptides are characterized as the major factors associated with neuron death in Alzheimer\&$\#$39;s disease, which is listed as the most common form of neurodegeneration. Disordered Aβ peptides are released from proteolysis of the amyloid precursor protein. The Aβ self-assembly process roughly takes place via five steps: disordered forms \→ oligomers \→ photofibrils \→ mature fibrils \→ plaques. Although Aβ fibrils are often observed in patient brains, oligomers were recently indicated to be major neurotoxic elements. In this work, the neurotoxic compound S-shape Aβ tetramer (S4Aβ) was investigated over 10 μs of unbiased MD simulations. In particular, the S4Aβ oligomer adopted a high dynamics structure, resulting in unsuccessful determination of their structures in experiments. The C-terminal was suggested as the possible nucleation of the Aβ aggregation. The sequences 27-35 and 39-40 formed rich β-content, whereas other residues mostly adopted coil structures. The mean value of the β-content over the equilibrium interval is \∼42 \± 3\%. Furthermore, the dissociation free energy of the S4Aβ peptide was predicted using a biased sampling method. The obtained free energy is Δ = -58.44 kcal/mol which is roughly the same level as the corresponding value of the U-shape Aβ peptide. We anticipate that the obtained S4Aβ structures could be used as targets for AD inhibitor screening over the in silico study.

}, issn = {2470-1343}, doi = {10.1021/acsomega.9b00992}, author = {Tung, Nguyen Thanh and Philippe Derreumaux and Vu, Van V and Nam, Pham Cam and Ngo, Son Tung} } @article {2019|2128, title = {Probable Transmembrane Amyloid α-Helix Bundles Capable of Conducting Ca Ions.}, journal = {J Phys Chem B}, volume = {123}, year = {2019}, month = {2019 Mar 28}, pages = {2645-2653}, abstract = {

Amyloid β (Aβ) peptides are considered the major causative agents of Alzheimer\&$\#$39;s disease (AD). In a widely accepted mechanism for AD pathogenesis, Aβ peptides are proposed to play multiple roles in damaging brain cells and their synaptic communications. Due to the heterogeneous nature of Aβ oligomers, their in vivo structures have not been understood. Most experimental and computational studies favored β-rich structures of Aβ as observed in Aβ fibrils. In this in silico study, we investigated an alternative perspective on the structures and function of Aβ oligomers in the cell membrane. Transmembrane α-helix bundles of the Aβ tetramer and trimer were observed in extensive temperature replica exchange molecular dynamics (REMD) simulations. We observed three minima on the free-energy landscape of each oligomer, namely, A, B, and C for the tetramer and D, E, and F for the trimer. Except for F, the minima consist of 4 or 3 parallel helices spanning across the membrane model dipalmitoylphosphatidylcholine. Replica exchange molecular dynamics-umbrella sampling (REMD-US) simulation was applied to study the process of a Ca crossing the pore formed by the α-helix bundles in A-E in comparison to that in a calcium channel and a proton channel. REMD-US reveals that A, C, and D allow Ca to cross their pore with a free-energy barrier comparable to that found for the calcium channel. In contrast, the free-energy barrier of a Ca ion crossing B, E, and the proton channel is significantly higher. This result suggests that Aβ peptide oligomers could form transmembrane α-helix bundles that provide feasible pathways for Ca transport. This is an intriguing observation that will stimulate further studies.

}, issn = {1520-5207}, doi = {10.1021/acs.jpcb.8b10792}, author = {Ngo, Son Tung and Philippe Derreumaux and Vu, Van V} }