| 1. |
- Abelein, Axel, et al.
(författare)
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The hairpin conformation of the amyloid beta peptide is an important structural motif along the aggregation pathway
- 2014
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Ingår i: Journal of Biological Inorganic Chemistry. - : Springer Science and Business Media LLC. - 0949-8257 .- 1432-1327. ; 19:4-5, s. 623-634
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Forskningsöversikt (refereegranskat)abstract
- The amyloid beta (A beta) peptides are 39-42 residue-long peptides found in the senile plaques in the brains of Alzheimer's disease (AD) patients. These peptides self-aggregate in aqueous solution, going from soluble and mainly unstructured monomers to insoluble ordered fibrils. The aggregation process(es) are strongly influenced by environmental conditions. Several lines of evidence indicate that the neurotoxic species are the intermediate oligomeric states appearing along the aggregation pathways. This minireview summarizes recent findings, mainly based on solution and solid-state NMR experiments and electron microscopy, which investigate the molecular structures and characteristics of the A beta peptides at different stages along the aggregation pathways. We conclude that a hairpin-like conformation constitutes a common motif for the A beta peptides in most of the described structures. There are certain variations in different hairpin conformations, for example regarding H-bonding partners, which could be one reason for the molecular heterogeneity observed in the aggregated systems. Interacting hairpins are the building blocks of the insoluble fibrils, again with variations in how hairpins are organized in the cross-section of the fibril, perpendicular to the fibril axis. The secondary structure propensities can be seen already in peptide monomers in solution. Unfortunately, detailed structural information about the intermediate oligomeric states is presently not available. In the review, special attention is given to metal ion interactions, particularly the binding constants and ligand structures of A beta complexes with Cu(II) and Zn(II), since these ions affect the aggregation process(es) and are considered to be involved in the molecular mechanisms underlying AD pathology.
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| 2. |
- Tiiman, Ann, et al.
(författare)
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Amyloidogenic Nanoplaques in Blood Serum of Patients with Alzheimer's Disease Revealed by Time-Resolved Thioflavin T Fluorescence Intensity Fluctuation Analysis
- 2019
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Ingår i: Journal of Alzheimer's Disease. - : IOS PRESS. - 1387-2877 .- 1875-8908. ; 68:2, s. 571-582
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Tidskriftsartikel (refereegranskat)abstract
- Background: Biomarkers are central to current research on molecular mechanisms underlying Alzheimer's disease (AD). Their further development is of paramount importance for understanding pathophysiological processes that eventually lead to disease onset. Biomarkers are also crucial for early disease detection, before clinical manifestation, and for development of new disease modifying therapies. Objective: The overall aim of this work is to develop a minimally invasive method for fast, ultra-sensitive and cost-effective detection of structurally modified peptide/protein self-assemblies in the peripheral blood and in other biological fluids. Specifically, we focus here on using this method to detect structured amyloidogenic oligomeric aggregates in the blood serum of apparently healthy individuals and patients in early AD stage, and measure their concentration and size. Methods: Time-resolved detection of Thioflavin T (ThT) fluorescence intensity fluctuations in a sub-femtoliter observation volume element was used to identify in blood serum ThT-active structured amyloidogenic oligomeric aggregates, hereafter called nanoplaques, and measure with single-particle sensitivity their concentration and size. Results: The concentration and size of structured amyloidogenic nanoplaques are significantly higher in the blood serum of individuals diagnosed with AD than in control subjects. Conclusion: A new method with the ultimate, single-particle sensitivity was successfully developed. The proposed approach neither relies on the use of immune-based probes, nor on the use of radiotracers, signal-amplification or protein separation techniques, and provides a minimally invasive test for fast and cost-effective early determination of structurally modified peptides/proteins in the peripheral blood, as shown here, but also in other biological fluids.
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| 3. |
- Tiiman, Ann, et al.
(författare)
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Heterogeneity and Turnover of Intermediates during Amyloid-beta (A beta) Peptide Aggregation Studied by Fluorescence Correlation Spectroscopy
- 2015
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Ingår i: Biochemistry. - : American Chemical Society (ACS). - 0006-2960 .- 1520-4995. ; 54:49, s. 7203-7211
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Tidskriftsartikel (refereegranskat)abstract
- Self-assembly of amyloid beta (A beta) peptide molecules into large aggregates is a naturally occurring process driven in aqueous solution by a dynamic interplay between hydrophobic interactions among A beta molecules, which promote aggregation, and steric and overall electrostatic hindrance, which stifles it. A beta self-association is entropically unfavorable, as it implies order increase in the system, but under favorable kinetic conditions, the process proceeds at appreciable rates, yielding A beta aggregates of different sizes and structures. Despite the great relevance and extensive research efforts, detailed kinetic mechanisms underlying A beta aggregation remain only partially understood. In this study, fluorescence correlation spectroscopy (FCS) and Thioflavin T (ThT) were used to monitor the time dependent growth of structured aggregates and characterize multiple components during the aggregation of A beta peptides in a heterogeneous aqueous solution. To this aim, we collected data during a relatively large number of observation periods, 30 consecutive measurements lasting 10 s each, at what we consider to be a constant time point in the slow aggregation process. This approach enabled monitoring the formation of nanomolar concentrations of structured amyloid aggregates and demonstrated the changing distribution of amyloid aggregate sizes throughout the aggregation process. We identified aggregates of different sizes with molecular weight from 260 to more than 1 x 10(6) kDa and revealed the hitherto unobserved kinetic turnover of intermediates during A beta aggregation. The effect of different A beta concentrations, A beta:ThT ratios, differences between the 40 (A beta 40) and 42 (A beta 42) residue long variants of A beta, and the effect of stirring were also examined.
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| 4. |
- Tiiman, Ann, et al.
(författare)
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In vitro fibrillization of Alzheimer's amyloid-beta peptide (1-42)
- 2015
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Ingår i: AIP Advances. - : AIP Publishing. - 2158-3226. ; 5:9
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Tidskriftsartikel (refereegranskat)abstract
- The amyloid deposition in the form of extracellular fibrillar aggregates of amyloid-beta (A beta) peptide is a critical pathological event in Alzheimer's disease. Here, we report a systematic investigation of the effects of environmental factors on the kinetics of A beta fibrillization in vitro. The effects of A beta 42 peptide concentration, temperature, pH, added solvents and the ratio of A beta 40 and A beta 42 on the peptide fibrillization under agitated conditions was studied. The analysis show that the rate of fibril growth by monomer addition is not limited by diffusion but by rearrangement in the monomer structure, which is enhanced by low concentrations of fluorinated alcohols and characterized by the activation energy of 12 kcal/ mol. Fibrillization rate decreases at pH values below 7.0 where simultaneous protonation of His 13 and 14 inhibits fibril formation. The lag period for A beta 42 was only twofold shorter and the fibril growth rate twofold faster than those of A beta 40. Lag period was shortened and the fibrillization rate was increased only at 90% content of A beta 42.
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| 5. |
- Tiiman, Ann, et al.
(författare)
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Specific Binding of Cu(II) Ions to Amyloid-Beta Peptides Bound to Aggregation-Inhibiting Molecules or SDS Micelles Creates Complexes that Generate Radical Oxygen Species
- 2016
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Ingår i: Journal of Alzheimer's Disease. - : IOS Press. - 1387-2877 .- 1875-8908. ; 54:3, s. 971-982
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Tidskriftsartikel (refereegranskat)abstract
- Aggregation of the amyloid-beta (A beta) peptide into insoluble plaques is a major factor in Alzheimer's disease (AD) pathology. Another major factor in AD is arguably metal ions, as metal dyshomeostasis is observed in AD patients, metal ions modulate A beta aggregation, and AD plaques contain numerous metals including redox-active Cu and Fe ions. In vivo, A beta is found in various cellular locations including membranes. So far, Cu(II)/A beta interactions and ROS generation have not been investigated in a membrane environment. Here, we study Cu(II) and Zn(II) interactions with A beta bound to SDS micelles or to engineered aggregation-inhibiting molecules (the cyclic peptide CP-2 and the Z(A beta 3)(12-58) Y18L Affibody molecule). In all studied systems the A beta N-terminal segment was found to be unbound, unstructured, and free to bind metal ions. In SDS micelles, A beta was found to bind Cu(II) and Zn(II) with the same ligands and the same K-D as in aqueous solution. ROS was generated in all Cu(II)/A beta complexes. These results indicate that binding of A beta to membranes, drugs, and other entities that do not interact with the A beta N-terminal part, appears not to compromise the N-terminal segment's ability to bind metal ions, nor impede the capacity of N-terminally bound Cu(II) to generate ROS.
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| 6. |
- Wärmländer, Sebastian, et al.
(författare)
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Biophysical Studies of the Amyloid beta-Peptide : Interactions with Metal Ions and Small Molecules
- 2013
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Ingår i: ChemBioChem. - : Wiley. - 1439-4227 .- 1439-7633. ; 14:14, s. 1692-1704
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Tidskriftsartikel (refereegranskat)abstract
- Alzheimer's disease is the most common of the protein misfolding (amyloid) diseases. The deposits in the brains of afflicted patients contain as a major fraction an aggregated insoluble form of the so-called amyloid beta-peptides (A beta peptides): fragments of the amyloid precursor protein of 39-43 residues in length. This review focuses on biophysical studies of the A beta peptides: that is, of the aggregation pathways and intermediates observed during aggregation, of the molecular structures observed along these pathways, and of the interactions of A beta with Cu and Zn ions and with small molecules that modify the aggregation pathways. Particular emphasis is placed on studies based on high-resolution and solid-state NMR methods. Theoretical studies relating to the interactions are also included. An emerging picture is that of A beta peptides in aqueous solution undergoing hydrophobic collapse together with identical partners. There then follows a relatively slow process leading to more ordered secondary and tertiary (quaternary) structures in the growing aggregates. These aggregates eventually assemble into elongated fibrils visible by electron microscopy. Small molecules or metal ions that interfere with the aggregation processes give rise to a variety of aggregation products that may be studied in vitro and considered in relation to observations in cell cultures or in vivo. Although the heterogeneous nature of the processes makes detailed structural studies difficult, knowledge and understanding of the underlying physical chemistry might provide a basis for future therapeutic strategies against the disease. A final part of the review deals with the interactions that may occur between the A beta peptides and the prion protein, where the latter is involved in other protein misfolding diseases.
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| 7. |
- Wärmländer, Sebastian K. T. S., et al.
(författare)
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Metal binding to the amyloid-beta peptides in the presence of biomembranes : potential mechanisms of cell toxicity
- 2019
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Ingår i: Journal of Biological Inorganic Chemistry. - : Springer Science and Business Media LLC. - 0949-8257 .- 1432-1327. ; 24:8, s. 1189-1196
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Forskningsöversikt (refereegranskat)abstract
- The amyloid-beta (A beta) peptides are key molecules in Alzheimer's disease (AD) pathology. They interact with cellular membranes, and can bind metal ions outside the membrane. Certain oligomeric A beta aggregates are known to induce membrane perturbations and the structure of these oligomers-and their membrane-perturbing effects-can be modulated by metal ion binding. If the bound metal ions are redox active, as e.g., Cu and Fe ions are, they will generate harmful reactive oxygen species (ROS) just outside the membrane surface. Thus, the membrane damage incurred by toxic A beta oligomers is likely aggravated when redox-active metal ions are present. The combined interactions between A beta oligomers, metal ions, and biomembranes may be responsible for at least some of the neuronal death in AD patients.
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