| 1. |
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| 2. |
- Arja, Katriann, et al.
(författare)
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Enhanced Fluorescent Assignment of Protein Aggregates by an Oligothiophene-Porphyrin-Based Amyloid Ligand
- 2013
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Ingår i: Macromolecular rapid communications. - : Wiley-VCH Verlag. - 1022-1336 .- 1521-3927. ; 34:9, s. 723-730
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Tidskriftsartikel (refereegranskat)abstract
- Fluorescent probes identifying protein aggregates are of great interest, as deposition of aggregated proteins is associated with many devastating diseases. Here, we report that a fluorescent amyloid ligand composed of two distinct molecular moieties, an amyloidophilic pentameric oligothiophene and a porphyrin, can be utilized for spectral and lifetime imaging assessment of recombinant A 1-42 amyloid fibrils and A deposits in brain tissue sections from a transgenic mouse model with Alzheimers disease pathology. The enhanced spectral range and distinct lifetime diversity of this novel oligothiopheneporphyrin-based ligand allow a more precise assessment of heterogeneous amyloid morphology compared with the corresponding oligothiophene dye.
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| 3. |
- Begum, Afshan, et al.
(författare)
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Transthyretin Binding Mode Dichotomy of Fluorescent trans-Stilbene Ligands
- 2023
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Ingår i: ACS Chemical Neuroscience. - : American Chemical Society (ACS). - 1948-7193. ; 14:5, s. 820-828
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Tidskriftsartikel (refereegranskat)abstract
- The orientations of ligands bound to the transthyretin (TTR) thyroxine (T4) binding site are difficult to predict. Conflicting binding modes of resveratrol have been reported. We previously reported two resveratrol based trans-stilbene fluorescent ligands, (E)-4-(2-(naphthalen-1-yl)vinyl)benzene-1,2-diol (SB-11) and (E)-4-(2-(naphthalen-2-yl)vinyl)-benzene-1,2-diol (SB-14), that bind native and misfolded protofibrillar TTR. The binding orientations of these two analogous ligands to native tetrameric TTR were predicted to be opposite. Herein we report the crystal structures of these TTR:ligand complexes. Opposite binding modes were verified but were different than predicted. The reverse binding mode (SB14) placing the naphthalene moiety toward the opening of the binding pocket renders the fluorescent ligand pH sensitive due to changes in Lys15 amine protonation. Conversely, the forward binding mode (SB-11) placing the naphthalene inward mediates a stabilizing conformational change, allowing intersubunit H-bonding between Ser117 of different monomers across the dimer interface. Our structures of TTR complexes answer important questions in ligand design and interpretation of trans-stilbene binding modes to the TTR T4 binding site.
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| 4. |
- Campos Melo, Raúl Ivan, et al.
(författare)
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Novel Trans-Stilbene-based Fluorophores as Probes for Spectral Discrimination of Native and Protofibrillar Transthyretin
- 2016
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Ingår i: ACS Chemical Neuroscience. - : American Chemical Society (ACS). - 1948-7193. ; 7:7, s. 924-940
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Tidskriftsartikel (refereegranskat)abstract
- Accumulation of misfolded transthyretin (TTR) as amyloid fibrils causes various human disorders. Native transthyretin is a neurotrophic protein and is a putative extracellular molecular chaperone. Several fluorophores have been shown in vitro to bind selectively to native TTR. Other compounds, such as thioflavin T, bind TTR amyloid fibrils. The probe 1-anilinonaphthalene-8-sulfonate (ANS) binds to both native and fibrillar TTR, becoming highly fluorescent, but with indistinguishable emission spectra for native and fibrillar TTR. Herein we report our efforts to develop a fluorescent small molecule capable of binding both native and misfolded protofibrillar TTR, providing distinguishable emission spectra. We used microwave synthesis for efficient production of a small library of trans-stilbenes and fluorescence spectral screening of their binding properties. We synthesized and tested 22 trans-stilbenes displaying a variety of functional groups. We successfully developed two naphthyl-based trans-stilbenes probes that detect both TTR states at physiological concentrations. The compounds bound with nanomolar to micromolar affinities and displayed distinct emission maxima upon binding native or misfolded protofibrillar TTR (>100 nm difference). The probes were mainly responsive to environment polarity providing evidence for the divergent hydrophobic structure of the binding sites of these protein conformational states. Furthermore, we were able to successfully use one of these probes to quantify the relative amounts of native and protofibrillar TTR in a dynamic equilibrium. In conclusion, we identified two trans-stilbene-based fluorescent probes, (E)-4-(2-(naphthalen-1-yl)vinyl)benzene-1,2-diol (11) and (E)-4-(2-(naphthalen-2-yl)vinyl)benzene-1,2-diol (14), that bind native and protofibrillar TTR, providing a wide difference in emission maxima allowing conformational discrimination by fluorescence spectroscopy. We expect these novel molecules to serve as important chemical biology research tools in studies of TTR folding and misfolding.
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| 5. |
- Elgland, Mathias, 1987-
(författare)
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Synthesis and application of β-configured [18/19F]FDGs : Novel prosthetic CuAAC click chemistry fluoroglycosylation tools for amyloid PET imaging and cancer theranostics
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Positron emission tomography (PET) is a non-invasive imaging method that renders three-dimensional images of tissue that selectively has taken up a radiolabelled organic compound, referred to as a radiotracer. This excellent technique provides clinicians with a tool to monitor disease progression and to evaluate how the patient respond to treatment. The by far most widely employed radiotracer in PET is called 2-deoxy-2-[18F]fluoro-D-glucose ([18F]FDG), which is often referred to as the golden standard in PET. From a molecular perspective, [18F]FDG is an analogue of glucose where a hydroxyl group has been replaced with a radioactive fluorine atom (18F). It is well known that covalent attachment of carbohydrates (i.e., glycosylation) to biomolecules tend to improve their properties in the body, in terms of; improved pharmacokinetics, increased metabolic stability and faster clearance from blood and other non-specific tissue. It is therefore natural to pursuit the development of a [18F]fluoroglycosylation method where [18F]FDG is chemically conjugated to a ligand with high affinity for a given biological target (e.g., tumors or disease-associated protein aggregates).This thesis describes a novel [18F]fluoroglycosylation method that in a simple and general manner facilitate the conjugation of [18F]FDG to biological ligands using click chemistry. The utility of the developed [18F]fluoroglycosylation method is demonstrated by radiolabelling of curcumin, thus forming a tracer that may be employed for diagnosis of Alzheimer’s disease. Moreover, a set of oligothiophenes were fluoroglycosylated for potential diagnosis of Alzheimer’s disease but also for other much rarer protein misfolding diseases (e.g., Creutzfeldt-Jakob disease and systemic amyloidosis). In addition, the synthesis of a series of 19F-fluoroglycosylated porphyrins is described which exhibited promising properties not only to detect but also to treat melanoma cancer. Lastly, the synthesis of a set of 19F-fluorinated E-stilbenes, structurally based on the antioxidant resveratrol is presented. The E-stilbenes were evaluated for their capacity to spectrally distinguish between native and protofibrillar transthyretin in the pursuit of finding diagnostic markers for the rare but severe disease, transthyretin amyloidosis.
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| 6. |
- Fyrner, Timmy, et al.
(författare)
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Derivatization of a bioorthogonal protected trisaccharide linker : towards multimodal tools for chemical biology
- 2012
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Ingår i: Bioconjugate chemistry. - : American Chemical Society (ACS). - 1043-1802 .- 1520-4812. ; 23:6, s. 1333-1340
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Tidskriftsartikel (refereegranskat)abstract
- When cross-linking biomolecules to surfaces or to other biomolecules, the use of appropriate spacer molecules is of great importance. Mimicking the naturally occurring spacer molecules will give further insight into their role and function, possibly unveil important issues regarding the importance of the specificity of carbohydrate-based anchor moieties, in e.g., glycoproteins and glycosylphosphatidylinositols. Herein, we present the synthesis of a lactoside-based trisaccharide, potentially suitable as a heterobifunctional bioorthogonal linker molecule whereon valuable chemical handles have been conjugated. An amino-derivative having thiol functionality shows promise as novel SPR-surfaces. Furthermore, the trisaccharide has been conjugated to a cholesterol moiety in combination with a fluorophore which successfully assemble on the cell surface in lipid microdomains, possibly lipid-rafts. Finally, a CuI-catalyzed azide-alkyne cycloaddition reaction (CuAAC) confirms the potential use of oligosaccharides as bioorthogonal linkers in chemical biology.
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| 7. |
- Hammarström, Per, et al.
(författare)
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A Fluorescent Pentameric Thiophene Derivative Detects in Vitro-Formed Prefibrillar Protein Aggregates
- 2010
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Ingår i: BIOCHEMISTRY. - : ACS American Chemical Society. - 0006-2960 .- 1520-4995. ; 49:32, s. 6838-6845
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Tidskriftsartikel (refereegranskat)abstract
- Protein aggregation is associated with a wide range of diseases, and molecular probes that are able to detect a diversity of misfolded protein assemblies are of great importance. The identification of prefibrillar states preceding the formation of well-defined amyloid fibrils is of particular interest both because of their likely role in the mechanism of fibril formation and because of the growing awareness that these species are likely to play a critical role in the pathogenesis of protein deposition diseases. Herein, we explore the use of an anionic oligothiophene derivative, p-FTAA, for detection of prefibrillar protein aggregates during in vitro fibrillation of three different amyloidogenic proteins (insulin, lysozyme, and prion protein). p-FTAA generally detected prefibrillar protein aggregates that could not be detected by thioflavine T fluorescence and in addition showed high fluorescence when bound to mature fibrils. Second, the kinetics of protein aggregation or the formation of amyloid fibrils of insulin was not extensively influenced by the presence of various concentrations of p-FTAA. These results establish the use of p-FTAA as an additional tool for studying the process of protein aggregation.
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| 8. |
- Herland, Anna, et al.
(författare)
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Synthesis of a regioregular zwitterionic conjugated oligoelectrolyte, usable as an optical probe for detection of amyloid fibril formation at acidic pH
- 2005
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 127:7, s. 2317-2323
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Tidskriftsartikel (refereegranskat)abstract
- Changes of the optical properties of conjugated polyelectrolytes have been utilized to monitor noncovalent interactions between biomolecules and the conjugated polyelectrolytes in sensor applications. A regioregular, zwitterionic conjugated oligoelectrolyte was synthesized in order to create a probe with a defined set of optical properties and hereby facilitate interpretation of biomolecule−oligoelectrolyte interactions. The synthesized oligoelectrolyte was used at acidic pH as a novel optical probe to detect amyloid fibril formation of bovine insulin and chicken lysozyme. Interaction of the probe with formed amyloid fibrils results in changes of the geometry and the electronic structure of the oligoelectrolyte chains, which were monitored with absorption and emission spectroscopy.
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| 9. |
- Mishra, Rajesh, et al.
(författare)
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Impact of N-glycosylation site variants during human PrP aggregation and fibril nucleation
- 2019
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Ingår i: Biochimica et Biophysica Acta - Proteins and Proteomics. - : ELSEVIER. - 1570-9639 .- 1878-1454. ; 1867:10, s. 909-921
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Tidskriftsartikel (refereegranskat)abstract
- Misfolding and aggregation of the human prion protein (PrP) cause neurodegenerative transmissible spongiform encephalopathies such as Creutzfeldt-Jakob disease. Mature native PrP is composed of 209 residues and is folded into a C-terminal globular domain (residues 125-209) comprising a small two-stranded beta-sheet and three alpha-helices. The N-terminal domain (residues 23-124) is intrinsically disordered. Expression of truncated PrP (residues 90-231) is sufficient to cause prion disease and residues 90/100-231 is comprising the amyloid-like fibril core of misfolded infectious PrP. During PrP fibril formation under native conditions in vitro, the disordered N-terminal domain slows down fibril formation likely due to a mechanism of initial aggregation forming morphologically disordered aggregates. The morphological disordered aggregate is a transient phase. Nucleation of fibrils occurs from this initial aggregate. The aggregate phase is largely circumvented by seeding with preformed PrP fibrils. In vivo PrP is N-glycosylated at positions Asn181 and Asn197. Little is known about the importance of these positions and their glycans for PrP stability, aggregation and fibril formation. We have in this study taken a step towards that goal by mutating residues 181 and 197 for cysteines to study the positional impact on these processes. We have further by organic synthetic chemistry and chemical modification generated synthetic glycosylations in these positions. Our data shows that residue 181 when mutated to a cysteine is a key residue for self -chaperoning, rendering a trap in the initial aggregate preventing conformational changes towards amyloid fibril formation. Position 197 is less involved in the aggregate trapping and is more geared towards beta-sheet structure conversion within amyloid fibrils. As expected, synthetic glycosylated 197 is less affected towards fibril formation compared to glycosylated 181. Our data are rather compatible with the parallel in-register intermolecular beta-sheet model structure of the PrP90-231 fibril and sheds light on the misfolding transitions of PrP in vitro. We hypothesize that glycosylation of position 181 is a key site for prion strain differentiation in vivo.
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| 10. |
- Nilsson, K. Peter R., et al.
(författare)
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Imaging distinct conformational states of amyloid-beta fibrils in Alzheimer's disease using novel luminescent probes
- 2007
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Ingår i: ACS Chemical Biology. - : American Chemical Society (ACS). - 1554-8929 .- 1554-8937. ; 2:8, s. 553-560
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Tidskriftsartikel (refereegranskat)abstract
- Using luminescent conjugated polyelectrolyte probes (LCPs), we demonstrate the possibility to distinguish amyloid-β 1–42 peptide (Aβ1–42) fibril conformations, by analyzing in vitro generated amyloid fibrils of Aβ1–42 formed under quiescent and agitated conditions. LCPs were then shown to resolve such conformational heterogeneity of amyloid deposits in vivo. A diversity of amyloid deposits depending upon morphology and anatomic location was illustrated with LCPs in frozen ex vivo brain sections from a transgenic mouse model (tg-APP swe) of Alzheimer’s disease. Comparative LCP fluorescence showed that compact-core plaques of amyloid β precursor protein transgenic mice were composed of rigid dense amyloid. A more abundant form of amyloid plaque displayed morphology of a compact center with a protruding diffuse exterior. Surprisingly, the compact center of these plaques showed disordered conformations of the fibrils, and the exterior was composed of rigid amyloid protruding from the disordered center. This type of plaque appears to grow from more loosely assembled regions toward solidified amyloid tentacles. This work demonstrates how application of LCPs can prove helpful to monitor aggregate structure of in vivo formed amyloid deposits such as architecture, maturity, and origin.
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