| 1. |
- Ekebergh, Andreas, 1984, et al.
(author)
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Exploring a cascade Heck-Suzuki reaction based route to kinase inhibitors using design of experiments
- 2015
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In: Organic and biomolecular chemistry. - : Royal Society of Chemistry (RSC). - 1477-0520 .- 1477-0539. ; 13:11, s. 3382-3392
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Journal article (peer-reviewed)abstract
- Design of Experiments (DoE) has been used to optimize a diversity oriented palladium catalyzed cascade Heck-Suzuki reaction for the construction of 3-alkenyl substituted cyclopenta[b]indole compounds. The obtained DoE model revealed a reaction highly dependent on the ligand. Guided by the model, an optimal ligand was chosen that selectively delivered the desired products in high yields. The conditions were applicable with a variety of boronic acids and were used to synthesize a library of 3-alkenyl derivatized compounds. Focusing on inhibition of kinases relevant for combating melanoma, the library was used in an initial structure-activity survey. In line with the observed kinase inhibition, cellular studies revealed one of the more promising derivatives to inhibit cell proliferation via an apoptotic mechanism.
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| 2. |
- Ekebergh, Andreas, 1984, et al.
(author)
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On the photostability of scytonemin, analogues thereof and their monomeric counterparts
- 2015
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In: Photochemical and Photobiological Sciences. - : Springer Science and Business Media LLC. - 1474-9092 .- 1474-905X. ; 14:12, s. 2179-2186
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Journal article (peer-reviewed)abstract
- As a part of their sun-protective strategy, cyanobacteria produce the natural UV-screener scytonemin. Its accumulation in the extracellular sheaths allows the bacteria to thrive in inhospitable locations highly exposed to solar radiation. Scytonemin is often referred to as photostable and has been reported to be non-fluorescent. Taken together, these properties indicate inherently fast non-radiative relaxation processes. Despite these interesting traits, the photophysics of scytonemin is as yet almost completely unexplored. In this study, we have compared the steady-state photophysics of scytonemin itself and four derivatives thereof. Furthermore, the in vitro photostability of scytonemin was studied in different solvents using a solar simulation system. Scytonemin and the investigated derivatives demonstrated a more rapid photoinduced decay in comparison with two commercial UV-screening agents. The photostability could be modulated by varying the solvent, with the protic solvent ethanol providing the most stabilizing environment.
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| 3. |
- Kaya, Ibrahim, et al.
(author)
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On-Tissue Chemical Derivatization of Catecholamines Using 4-(N-Methyl)pyridinium Boronic Acid for ToF-SIMS and LDI-ToF Mass Spectrometry Imaging
- 2018
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In: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 90:22, s. 13580-13590
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Journal article (peer-reviewed)abstract
- The analysis of small polar compounds with ToF-SIMS and MALDI-ToF-MS have been generally hindered by low detection sensitivity, poor ionization efficiency, ion suppression, analyte in-source fragmentation, and background spectral interferences from either a MALDI matrix and/or endogenous tissue components. Chemical derivatization has been a well-established strategy for improved mass spectrometric detection of many small molecular weight endogenous compounds in tissues. Here, we present a devised strategy to selectively derivatize and sensitively detect catecholamines with both secondary ion ejection and laser desorption ionization strategies, which are used in many imaging mass spectrometry (IMS) experiments. Chemical derivatization of catecholamines was performed by a reaction with a synthesized permanent pyridinium-cation-containing boronic acid molecule, 4-(N-methyl)pyridinium boronic acid, through boronate ester formation (boronic acid-diol reaction). The derivatization facilitates their sensitive detection with ToF-SIMS and LDI-ToF mass spectrometric techniques. 4-(N-Methyl)pyridinium boronic acid worked as a reactive matrix for catecholamines with LDI and improved the sensitivity of detection for both SIMS and LDI, while the isotopic abundances of the boron atom reflect a unique isotopic pattern for derivatized catecholamines in MS analysis. Finally, the devised strategy was applied, as a proof of concept, for on-tissue chemical derivatization and GCIB-ToF-SIMS (down to 3 μm per pixel spatial resolution) and LDI-ToF mass spectrometry imaging of dopamine, epinephrine, and norepinephrine in porcine adrenal gland tissue sections. MS/MS using collision-induced dissociation (CID)-ToF-ToF-SIMS was subsequently employed on the same tissue sections after SIMS and LDI mass spectrometry imaging experiments, which provided tandem MS information for the validation of the derivatized catecholamines in situ. This methodology can be a powerful approach for the selective and sensitive ionization/detection and spatial localization of diol-containing molecules such as aminols, vic-diols, saccharides, and glycans along with catecholamines in tissue sections with both SIMS and LDI/MALDI-MS techniques. © 2018 American Chemical Society.
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| 4. |
- Nimmermark, Anders, 1971, et al.
(author)
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Teaching of chemical bonding: a study of Swedish and South African students' conceptions of bonding
- 2016
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In: Chemistry Education Research and Practice. - : Royal Society of Chemistry (RSC). - 1109-4028 .- 1756-1108. ; 17:4, s. 985-1005
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Journal article (peer-reviewed)abstract
- Almost 700 Swedish and South African students from the upper secondary school and first-term chemistry university level responded to our survey on concepts of chemical bonding. The national secondary school curricula and most common textbooks for both countries were also surveyed and compared for their content on chemical bonding. Notable differences between the countries were found in textbooks and in the curriculum regarding the topics of ionic bonding, bond energetics and use of the VSEPR model, the latter being absent in the Swedish curriculum and ionic bonding not explicitly mentioned in the South African curriculum. To some extent these differences are reflected in the students' responses to the survey. It is also clear that university teachers in both countries must prepare effective counter-measures against deep rooted misunderstandings. For the upper secondary school level it is suggested that the bond energetics and exothermic and endothermic reactions be clearly and carefully presented and separated as the study indicates that mixing of these two concepts is a major cause of confusion.
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| 5. |
- Ye, Chen, et al.
(author)
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Annihilation Versus Excimer Formation by the Triplet Pair in Triplet-Triplet Annihilation Photon Upconversion
- 2019
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In: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 141:24, s. 9578-9584
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Journal article (peer-reviewed)abstract
- The triplet pair is the key functional unit in triplet-triplet annihilation photon upconversion. The same molecular properties that stabilize the triplet pair also allow dimers to form on the singlet energy surface, creating an unwanted energy relaxation pathway. Here we show that excimer formation most likely is a consequence of a triplet dimer formed before the annihilation event. Polarity-dependent studies were performed to elucidate how to promote wanted emission pathways over excimer formation. Furthermore, we show that the yield of triplet-triplet annihilation is increased in higher-viscosity solvents. The results will bring new insights in how to increase the upconversion efficiency and how to avoid energy-loss channels.
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