| 1. |
- Zhang, Jun, Dr. 1987-, et al.
(author)
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Intramolecular Proton and Charge Transfer of Pyrene-based trans-Stilbene Salicylic Acids Applied to Detection of Aggregated Proteins.
- 2018
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In: ChemPhysChem. - Weinheim, Germany : Wiley-VCH Verlag. - 1439-4235 .- 1439-7641. ; 19:22, s. 3001-3009
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Journal article (peer-reviewed)abstract
- Two analogues to the fluorescent amyloid probe 2,5-bis(4'-hydroxy-3'-carboxy-styryl)benzene (X-34) were synthesized based on the trans-stilbene pyrene scaffold (Py1SA and Py2SA). The compounds show strikingly different emission spectra when bound to preformed Aβ1-42 fibrils. This remarkable emission difference is retained when bound to amyloid fibrils of four distinct proteins, suggesting a common binding configuration for each molecule. Density functional theory calculations show that Py1SA is twisted, while Py2SA is more planar. Still, an analysis of the highest occupied molecular orbitals (HOMOs) and lowest unoccupied molecular orbitals (LUMOs) of the two compounds indicates that the degree of electronic coupling between the pyrene and salicylic acid (SA) moieties is larger in Py1SA than in Py2SA. Excited state intramolecular proton transfer (ESIPT) coupled-charge transfer (ICT) was observed for the anionic form in polar solvents. We conclude that ICT properties of trans-stilbene derivatives can be utilized for amyloid probe design with large changes in emission spectra and decay times from analogous chemical structures depending on the detailed physical nature of the binding site.less thanbr /greater than (© 2018 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim.)
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| 2. |
- Zhang, Jun, Dr. 1987-
(author)
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Synthesis and characterization of fluorescent stilbene-based probes targeting amyloid fibrils
- 2018
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Doctoral thesis (other academic/artistic)abstract
- Alzheimer’s disease (AD) is characterized by two main protein aggregate hallmarks in the brain: extracellular deposition of the amyloid-β (Aβ) in senile plaques and intracellular neurofibrillary tangles (NFTs) consisting of hyperphosphorylated tau protein. The past decade has seen great progress in the development of imaging probes for the non-invasive detection of Aβ and tau aggregates. Here positron emission tomography (PET), single-photon emission computed tomography (SPECT) and magnetic resonance imaging (MRI), are highly promising technologies for clinical diagnostics. However, as a research tool, optical imaging is superior because it is real-time, sensitive, inexpensive, not radioactive and that it in particular affords high-resolution studies both in vitro and in vivo. Fluorescent probes are especially useful for designing novel binding scaffolds for structure investigations of protein aggregates. This thesis describes design, synthesis and evaluation of a series of fluorescent probes for detection of amyloid fibrils, especially Aβ or tau aggregates in vitro.Firstly, trans-stilbenoid vinylbenzene-1,2-diol with benzene, naphthalene, anthracene, and pyrene are investigated with respect to their photophysical properties free in solution and when bound to amyloid fibrils, including time-resolved fluorescence measurements. It is noted that the extended conjugated systems retained the amyloid targeting properties of the probes and both the anthracene and pyrene moieties extensively enhanced the fluorescence intensity and prolonged lifetimes.Secondly, the synthesis of two molecules, Py1SA and Py2SA, based on pyrene linked to salicylic acid via a trans-stilbene C = C bond is presented. The compounds show strikingly different emission spectra when bound to preformed Aβ1-42 fibrils as well as to fibrils from four other distinct proteins. Additionally, excited state intramolecular proton transfer (ESIPT) coupled-charge transfer (ICT) is observed for the anionic form of the probes in polar solvents. This is likely the reason for the spectral differences of the probes when bound to amyloid fibrils.Moreover, the synthesis of a further development of the Congo red analogue X-34 [2,5-bis(4’-hydroxy-3’-carboxy-styryl) benzene] by rational design and synthesis is described. Full photophysical characterization was performed, including recording absorbance and fluorescence spectra, Stokes shift, quantum yield and fluorescence lifetimes. All ligands displayed high affinity towards recombinant amyloid fibrils of Aβ1-42 and tau as well as selectivity towards the corresponding disease-associated protein aggregates in human post mortem AD tissue.Lastly, the synthesis of a set of 2,1,3-benzothiadiazole (BTD)-based ligands with different conjugated spacers and variable patterns of OH substitutions of bis-styryl-BTD prototypes were developed. Aβ binding affinities (Aβ1-42 and Aβ1-40 fibrils) and the specificity towards Aβ plaques of all ligands were determined. These findings extend the structure to activity relationships of BTD-based ligands for Aβ fibril binding.Throughout the studies in this dissertation, new interesting properties of small molecule fluorescence probes have been discovered and analyzed. This knowledge should facilitate the development of noninvasive probes for early detection of Alzheimer's disease and to distinguish different Aβ fibril polymorphs.
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| 3. |
- Zhang, Jun, Dr. 1987-, et al.
(author)
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trans-Stilbenoids with Extended Fluorescence Lifetimes for the Characterization of Amyloid Fibrils
- 2017
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In: ACS Omega. - : American Chemical Society (ACS). - 2470-1343. ; 2:8, s. 4693-4704
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Journal article (peer-reviewed)abstract
- It was previously reported that two naphthyl-based trans-stilbene probes, (E)-4-(2-(naphthalen-1-yl)vinyl)benzene-1,2-diol (1) and (E)-4-(2-(naphthalen-2-yl)vinyl)benzene-1,2-diol (3), can bind to both native transthyretin (TTR) and misfolded protofibrillar TTR at physiological concentrations, displaying distinct emission maxima bound to the different conformational states (>100 nm difference). To further explore this amyloid probe scaffold to obtain extended fluorescence lifetimes, two new analogues with expanded aromatic ring systems (anthracene and pyrene), (E)-4-(2-(anthracen-2-yl)vinyl)benzene-1,2-diol (4) and (E)-4-(2-(pyren-2-yl)vinyl)benzene-1,2-diol (5), were synthesized employing the palladium-catalyzed Mizoroki–Heck reaction. (E)-4-Styrylbenzene-1,2-diol (2), 3, 4, and 5 were investigated with respect to their photophysical properties in methanol and when bound to insulin, lysozyme, and Aβ1-42 fibrils, including time-resolved fluorescence measurements. In conclusion, 4 and 5 can bind to both native and fibrillar TTR, becoming highly fluorescent. Compounds 2–5 bind specifically to insulin, lysozyme, and Aβ1-42 fibrils with an apparent fluorescence intensity increase and moderate binding affinities. The average fluorescence lifetimes of the probes bound to Aβ1-42 fibrils are 1.3 ns (2), 1.5 ns (3), 5.7 ns (4), and 29.8 ns (5). In summary, the variable aromatic moieties of the para-positioned trans-stilbenoid vinyl-benzene-1,2-diol with benzene, naphthalene, anthracene, and pyrene showed that the extended conjugated systems retained the amyloid targeting properties of the probes. Furthermore, both the anthracene and pyrene moieties extensively enhanced the fluorescence intensity and prolonged lifetimes. These attractive probe properties should improve amyloid detection and characterization by fluorescence-based techniques.
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| 4. |
- Kronstrand, Robert, 1966-, et al.
(author)
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Rilmazafone: A Designer Benzodiazepine Pro-Drug Involved in Fatal Intoxications
- 2023
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In: Journal of Analytical Toxicology. - : OXFORD UNIV PRESS INC. - 0146-4760 .- 1945-2403. ; 47:7, s. 640-643
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Journal article (peer-reviewed)abstract
- Rilmazafone is a pro-drug that can be prescribed in Japan to treat insomnia. Rilmazafone metabolizes into active compounds by a ring closure resulting in a triazolo benzodiazepine structure similar to alprazolam. In mid-2022, the National Board of Forensic Medicine in Sweden were requested to investigate two separate deaths with the suspected use of pagoclone. Packages labeled "Pagoclone" were found at each scene that was suspected to contain rilmazafone based on website information. During screening by high resolution mass spectrometry, rilmazafone metabolites were presumptively identified. Due to the lack of reference material for the active metabolites, the metabolites were synthesized in house and quantification of the compounds identified in the two autopsy cases was prompted. In Case 1, femoral blood concentrations of 7.9, 65 and 170 ng/g of the metabolites rilmazolam, N-desmethyl rilmazolam and di-desmethyl rilmazolam, respectively, were detected. Additional toxicological findings included the medications haloperidol, alimemazine, fluoxetine, olanzapine and acetaminophen. In Case 2, femoral blood concentrations of 1.7, 1.4 and 70 ng/g of rimazolam, N-desmethyl rilmazolam and di-desmethyl rilmazolam, respectively, were detected. Additional toxicological findings included loperamide, alimemazine and pregabalin. The intake of rilmazafone was determined as the cause of death in Case 1 and contributed in the Case 2.
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| 5. |
- Larsson, Johan, 1990-, et al.
(author)
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Combining endocannabinoids with retigabine for enhanced M-channel effect and improved KV7 subtype selectivity
- 2020
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In: The Journal of General Physiology. - : ROCKEFELLER UNIV PRESS. - 0022-1295 .- 1540-7748. ; 152:8
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Journal article (peer-reviewed)abstract
- Retigabine is unique among anticonvulsant drugs by targeting the neuronal M-channel, which is composed of KV7.2/KV7.3 and contributes to the negative neuronal resting membrane potential. Unfortunately, retigabine causes adverse effects, which limits its clinical use. Adverse effects may be reduced by developing M-channel activators with improved KV7 subtype selectivity. The aim of this study was to evaluate the prospect of endocannabinoids as M-channel activators, either in isolation or combined with retigabine. Human KV7 channels were expressed in Xenopus laevis oocytes. The effect of extracellular application of compounds with different properties was studied using two-electrode voltage clamp electrophysiology. Site-directed mutagenesis was used to construct channels with mutated residues to aid in the mechanistic understanding of these effects. We find that arachidonoyl-L-serine (ARA-S), a weak endocannabinoid, potently activates the human M-channel expressed in Xenopus oocytes. Importantly, we show that ARA-S activates the M-channel via a different mechanism and displays a different KV7 subtype selectivity compared with retigabine. We demonstrate that coapplication of ARA-S and retigabine at low concentrations retains the effect on the M-channel while limiting effects on other KV7 subtypes. Our findings suggest that improved KV7 subtype selectivity of M-channel activators can be achieved through strategically combining compounds with different subtype selectivity.
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| 6. |
- Ottosson, Nina, et al.
(author)
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A drug pocket at the lipid bilayer-potassium channel interface
- 2017
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In: Science Advances. - : AMER ASSOC ADVANCEMENT SCIENCE. - 2375-2548. ; 3:10
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Journal article (peer-reviewed)abstract
- Many pharmaceutical drugs against neurological and cardiovascular disorders exert their therapeutic effects by binding to specific sites on voltage-gated ion channels of neurons or cardiomyocytes. To date, all molecules targeting known ion channel sites bind to protein pockets that are mainly surrounded by water. We describe a lipid-protein drug-binding pocket of a potassium channel. We synthesized and electrophysiologically tested 125 derivatives, analogs, and related compounds to dehydroabietic acid. Functional data in combination with docking and molecular dynamics simulations mapped a binding site for small-molecule compounds at the interface between the lipid bilayer and the transmembrane segments S3 and S4 of the voltage-sensor domain. This fundamentally new binding site for small-molecule compounds paves the way for the design of new types of drugs against diseases caused by altered excitability.
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| 7. |
- Rautio, Tobias, et al.
(author)
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An improved procedure for the synthesis of fourteen 4-OH and 3-MeO-4OH metabolites of fentanyl analogues from two intermediates on multi-gram scale
- 2022
-
In: Synthetic Communications. - : Taylor & Francis Inc. - 0039-7911 .- 1532-2432. ; 52:3, s. 392-401
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Journal article (peer-reviewed)abstract
- Fentanyl analogues have appeared on the recreational drug market during the last ten years and caused many fatal overdoses around the world due to their high potencies. Their metabolites are of great interest for toxicology, metabolism and identification studies. According to the literature, fentanyl analogues with similar structures have similar metabolism profile. Therefore, a synthetic route that enables synthesis of the corresponding metabolites for several fentanyl analogues would be valuable. Fentanyl analogue metabolites are often polar and tailing on silica gel. Hence, the purification of these substances could be challengeable. In this work, a general synthetic route was developed and described for the multi-gram scale synthesis of 14 potential metabolites of seven fentanyl analogues. The synthetic route is concise and optimized, does not require any use of silica gel purification and is therefore convenient for large-scale synthesis. The overall yields of the metabolites were in the range of 25-57%.
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| 8. |
- Rautio, Tobias, et al.
(author)
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In vitro metabolite identification of acetylbenzylfentanyl, benzoylbenzylfentanyl, 3-fluoro-methoxyacetylfentanyl, and 3-phenylpropanoylfentanyl using LC-QTOF-HRMS together with synthesized references
- 2023
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In: Drug Testing and Analysis. - : WILEY. - 1942-7603 .- 1942-7611. ; 15:7, s. 711-729
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Journal article (peer-reviewed)abstract
- Acetylbenzylfentanyl, benzoylbenzylfentanyl, 3-fluoro-methoxyacetylfentanyl, and 3-phenylpropanoylfentanyl are fentanyl analogs that have been reported to the European Monitoring Centre for Drugs and Drug Addiction in recent years. The aim of this study was to identify metabolic pathways and potential biomarker metabolites of these fentanyl analogs. The compounds were incubated (5 mu M) with cryopreserved hepatocytes for up to 5 h in vitro. Metabolites were analyzed with liquid chromatography-quadrupole time of flight-high-resolution mass spectrometry (LC-QTOF-HRMS). The experiments showed that acetylbenzylfentanyl, benzoylbenzylfentanyl, and 3-phenylpropanoylfentanyl were mainly metabolized through N-dealkylation (forming nor-metabolites) and 3-fluoro-methoxyacetylfentanyl mainly through demethylation. Other observed metabolites were formed by mono-/dihydroxylation, dihydrodiol formation, demethylation, dehydrogenation, amide hydrolysis, and/or glucuronidation. The experiments showed that a large number of metabolites of 3-phenylpropanoylfentanyl were formed. The exact position of hydroxy groups in formed monohydroxy metabolites could not be established solely based upon recorded MSMS spectra of hepatocyte samples. Therefore, potential monohydroxy metabolites of 3-phenylpropanoylfentanyl, with the hydroxy group in different positions, were synthesized and analyzed together with the hepatocyte samples. This approach could reveal that the beta position of the phenylpropanoyl moiety was highly favored; beta-OH-phenylpropanoylfentanyl was the most abundant metabolite after the nor-metabolite. Both metabolites have the potential to serve as biomarkers for 3-phenylpropanoylfentanyl. The nor-metabolites of acetylbenzylfentanyl, benzoylbenzylfentanyl, and 3-fluoro-methoxyacetylfentanyl do also seem to be suitable biomarker metabolites, as do the demethylated metabolite of 3-fluoro-methoxyacetylfentanyl. Identified metabolic pathways and formed metabolites were in agreement with findings in previous studies of similar fentanyl analogs.
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| 9. |
- Silverå Ejneby, Malin, 1987-, et al.
(author)
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Atom-by-atom tuning of the electrostatic potassium-channel modulator dehydroabietic acid
- 2018
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In: The Journal of General Physiology. - New York, United States : Rockefeller Institute for Medical Research. - 0022-1295 .- 1540-7748. ; 150:5, s. 731-750
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Journal article (peer-reviewed)abstract
- Dehydroabietic acid (DHAA) is a naturally occurring component of pine resin that was recently shown to open voltage-gated potassium (KV) channels. The hydrophobic part of DHAA anchors the compound near the channel’s positively charged voltage sensor in a pocket between the channel and the lipid membrane. The negatively charged carboxyl group exerts an electrostatic effect on the channel’s voltage sensor, leading to the channel opening. In this study, we show that the channel-opening effect increases as the length of the carboxyl-group stalk is extended until a critical length of three atoms is reached. Longer stalks render the compounds noneffective. This critical distance is consistent with a simple electrostatic model in which the charge location depends on the stalk length. By combining an effective anchor with the optimal stalk length, we create a compound that opens the human KV7.2/7.3 (M type) potassium channel at a concentration of 1 µM. These results suggest that a stalk between the anchor and the effector group is a powerful way of increasing the potency of a channel-opening drug.
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| 10. |
- Wallgren, Jakob, 1987-
(author)
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An insight into the metabolism of New Psychoactive Substances : Structural elucidation of urinary metabolites of synthetic cannabinoids and fentanyl analogues using synthesized reference standards
- 2020
-
Doctoral thesis (other academic/artistic)abstract
- New Psychoactive Substances (NPS) is an umbrella term covering hundreds of substances across different drug groups. Many of these substances were originally developed for therapeutic use but have later appeared on the recreational drug market. The use of NPS has been associated with many outbreaks leading to hospitalizations and has been implicated in numerous fatalities worldwide. To be able to analytically detect drugs in a forensic setting is vital in the fight against the abuse of NPS. One of the most notable challenges in detection of NPS is the identification of major urinary metabolites for use as biomarkers. Furthermore, given the lack of reference standards in most metabolism studies, the major urinary metabolites can often only be tentatively determined.This thesis describes the synthesis and analysis of potential metabolites used to identify the exact structures of major metabolites of the synthetic cannabinoid AKB-48, fentanyl and five fentanyl analogues in authentic human urine samples and/or hepatocyte incubations. Synthetic targets were chosen based on previous metabolism studies by our research group. Subsequently, synthetic routes were developed to produce numerous potential metabolites across the studied NPS. The synthesized reference standards were analyzed by LC-QTOF-MS alongside hepatocyte drug incubations and authentic human urine samples. Comparison of the resulting analytical data was used to determine the exact structures of many metabolites. This includes urinary metabolites of AKB-48 with a single hydroxyl group situated on a secondary carbon of the adamantane moiety, or position 3 or 5 of the pentyl side chain. For the studied fentanyls, the β-OH and the 4’-OH metabolites were abundant metabolites identified in hepatocyte incubations while the 4’-OH, 4’-OH-3’-OMe and 3’,4’-diOH were the favored metabolic motifs among the metabolites identified in urine.Additionally, a concise synthetic route to produce synthetic cannabinoid metabolites with the 4-OH-5F pentyl side chain motif was developed and demonstrated for four synthetic cannabinoids. These findings and the developed synthetic routes can be used to provide forensic toxicology laboratories with urinary biomarkers for drug detection. Moreover, the synthesized reference standards of major metabolites can be studied to better understand the toxicity of their parent drugs.
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