A Platform of Phenol‐Based Nitroxide Radicals as an “EPR Toolbox” in Supramolecular and Click Chemistry

Hauenschild, Till; Hinderberger, Dariush

doi:10.1002/cplu.201800429

Cited by 10 publications

(8 citation statements)

References 39 publications

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“…These comprise as π/π interactions, hydrogen bonding, Coulomb, and dipole/dipole interactions as well as van der Waals and hydrophobic interactions. [ 19 ] The mono‐ and dianionic spin probes 4‐carboxy‐2,2,6,6‐tetramethyl‐1‐piperidinyloxyl (4‐carboxy‐TEMPO) and disodium nitrosodisulfonate (Fremy's salt), respectively, as well as the cationic tetraalkylammonium TEMPO species (4‐trimethylammonium‐2,2,6,6‐tetramethyl‐1‐piperidinyloxyl [CAT‐1]) are able to participate in Coulomb interactions. Note that all ionic spin probes were used as salts, and we do not explicitly mention the respective counterions.…”

Section: Resultsmentioning

confidence: 99%

Molecular‐Level Interactions of Nanodisc‐Forming Copolymers Dissected by EPR Spectroscopy

Eisermann

Hoffmann

Schöffmann

et al. 2021

Macro Chemistry & Physics

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This study focuses on analyzing the noncovalent interaction patterns between three lipid‐nanodisc‐forming polymers and nitroxide radicals which are used as small organic tracer molecules. Besides the negatively charged polymers diisobutylene/maleic acid (DIBMA) and styrene/maleic acid (SMA) (2:1), the solvation behavior of a newly synthesized zwitterionic styrene/maleic amide sulfobetaine copolymer named SMA‐sulfobetaine (SB) is characterized. The applied spin probes vary in their respective chemical structure, allowing the report of different local micropolarities and nanoscopic regions by recording temperature‐dependent continuous‐wave electron paramagnetic resonance (CW EPR) spectra. In combination with light scattering experiments, a nanoscopic interpretation of the dominant polymer/guest molecule interaction patterns is provided. The results indicate that in SMA and DIBMA, ionic interactions dominate the interaction patterns with other molecules. In SMA‐SB, the zwitterionic side chains mainly induce a dynamic assembly with guest molecules due to weaker noncovalent interactions. Depending on the applied spin probe, temperature‐dependent CW EPR measurements reveal nanoscopic cloud points depending on the interaction patterns with SMA‐SB which can occur more than 20 °C below its macroscopically observed upper critical solution temperature. Finally, the detailed dissection of interaction patterns may provide a better understanding that may even allow tuning the polymers’ properties for use in lipid nanodisc formation.

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Section: Resultsmentioning

confidence: 99%

Molecular‐Level Interactions of Nanodisc‐Forming Copolymers Dissected by EPR Spectroscopy

Eisermann

Hoffmann

Schöffmann

et al. 2021

Macro Chemistry & Physics

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“…Because of the mild reaction conditions, which keep the TEMPO radical groups as open-shell moieties, Steglich esterification has been oft-used for the syntheses of TEMPO-bearing small molecules. [56][57][58][59] As for the synthesis of M1-Br 2 , the initial attempt of brominating M1 directly using NBS was unsuccessful as the TEMPO radical groups on M1 were quenched during the reaction. As an alternative, the ProDOT-COOH precursor was brominated using NBS to produce ProDOT-COOH-Br 2 , which was then reacted with 4-hydroxy-TEMPO to synthesize M1-Br 2 through the Steglich esterification.…”

Section: Resultsmentioning

confidence: 99%

Impact of open‐shell loading on mass transport and doping in conjugated radical polymers

Liu

Perera

Wang

et al. 2021

Journal of Polymer Science

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Radical-containing polymers are an evolving class of redox-active macromolecules that have received great interest; however, most reports regarding radical polymers have focused on materials with nonconjugated backbones because their application drivers did not require this conjugation. Conversely, there has been a recent rise in the development of radical polymers for nextgeneration applications where imparting conjugation to the backbone of the radical polymer could be of significant benefit. To this end, we designed and synthesized a series of 3,4-propylenedioxythiophene (ProDOT)-based polymers bearing nitroxide radical pendent groups via direct arylation polymerization. Specifically, we present four radical polymers with open-shell loadings ranging from 24% to 82% of the total number of repeat units per polymer chain. The impact of openshell loading on the electrochemical behaviors of these polymers in different electrolytes was then established using cyclic voltammetry, spectroelectrochemical analyses, and electrochemical quartz-crystal microbalance with dissipation monitoring. We demonstrate that incorporating the open-shell moieties in the ProDOT-based polymers lowers the oxidation onset potential of the conjugated backbone and increases the solvent and ion uptake significantly. Thus, this effort provides a clear picture of the mass transfer and doping mechanism of the ProDOT-based radical polymers to aid in guiding their future design.

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“…An alternative and simplified approach would be the utilization of a “toolbox” of some established spin‐labeled pharmaceuticals (SLPs) or designable phenol‐based spin probes that are well‐known to represent albumin ligands. Comparative studies on XSA could also provide a quick view on global or local structural effects when the ligand binding sites and their positions are known from crystal structures.…”

Section: Resultsmentioning

confidence: 99%

Fatty Acid Triangulation in Albumins Using a Landmark Spin Label

Reichenwallner

Hauenschild

Schmelzer

et al. 2019

Israel Journal of Chemistry

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Several spatial correlations of up to six fatty acid (FA) binding sites in albumins were found by double electron-electron resonance (DEER). A strategy was used that combines spin-labeling and spin-probing techniques in electron paramagnetic resonance (EPR) spectroscopy. This is here achieved by introducing an additional covalent landmark spin (LS) label to the self-assembled system of EPR-active, paramagnetic stearic acid derivatives and albumins. Therefore, a cysteine specific, paramagnetic LS that was attached to the albumin surface at a unique position (Cys34) provides a fixed topological reference point for monitoring statistical ligand uptake. We propose that the determination of nanoscale distance distributions emerging between the LS and EPR-active fatty acid derivatives generally allows for the direct observation of individually occupied binding sites in solution. Essentially, several binding pockets, groups of them and evidence for ligand-induced allosteric modulation can be traced from such FA-LS interspin correlations. Experimental results were substantiated with theoretical predictions from molecular dynamics (MD) simulations. It was observed that all binding sites in an albumin ensemble may be statistically filled even at the lowest level of ligand loading. This approach generally bears the potential for mapping occupation states of individual ligand binding sites in proteins using such spinlabeled ligands.

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A Platform of Phenol‐Based Nitroxide Radicals as an “EPR Toolbox” in Supramolecular and Click Chemistry

Cited by 10 publications

References 39 publications

Molecular‐Level Interactions of Nanodisc‐Forming Copolymers Dissected by EPR Spectroscopy

Molecular‐Level Interactions of Nanodisc‐Forming Copolymers Dissected by EPR Spectroscopy

Impact of open‐shell loading on mass transport and doping in conjugated radical polymers

Fatty Acid Triangulation in Albumins Using a Landmark Spin Label

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