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Magic-angle spinning NMR spectroscopy provides insight into the impact of small molecule uptake by G-quartet hydrogels
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Reddy, G. N. Manjunatha, Peters, Gretchen Marie, Tatman, Ben, Rajan, Teena S., Kock, Si Min, Zhang, Jing, Frenguelli, Bruno G., Davis, Jeffery T., Marsh, Andrew and Brown, Steven P. (2020) Magic-angle spinning NMR spectroscopy provides insight into the impact of small molecule uptake by G-quartet hydrogels. Materials Advances, 1 (7). pp. 2236-2247. doi:10.1039/D0MA00475H ISSN 2633-5409.
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WRAP-Magic-angle-spinning-NMR-spectroscopy-provides-insight-Brown-2020.pdf - Accepted Version - Requires a PDF viewer. Available under License Creative Commons Attribution Non-commercial. Download (30Mb) | Preview |
Official URL: https://doi.org/10.1039/D0MA00475H
Abstract
Small molecule guests influence the functional properties of supramolecular hydrogels. Molecular-level understanding of such sol-gel compositions and structures is challenging due to the lack of long-range order and inherently heterogeneous sol-gel interface. In this study, insight into the uptake process of biologically relevant small molecules into guanosine-quartet(G4) borate hydrogels is obtained by gel-state magic-angle spinning (MAS) NMR spectroscopy. G4∙K+ borate hydrogel can absorb up to 0.3 equivalent of cationic methylene blue (MB) without a significant disruption of the G4 fibrils that make up the gel, whereas the addition of over 0.3 equivalents of MB to the same gel leads to a gel-to-sol transition. The gel-to-sol transition process is characterized ex situ by analyzing and comparing the 1H and 11B MAS NMR spectra acquired before and after the MB uptake. In particular, 11B isotropic chemical shifts and quadrupole interactions were determined by analyzing the 11B MAS NMR spectra acquired at different magnetic fields, 11.7 T, 14.1 T and 20 T, which enable the different local bonding environments of borate anions in sol- and gel domains to be distinguished and identified. By comparison, uptake of heterocyclic molecules such as adenine, cytosine and 1-methylthymine into G4∙Na+ borate hydrogels lead to stiff and clear gels while increasing the solubility of the nucleobases as compared to the solubility of the same compounds in water. G4∙Na+ gel can uptake one equiv. of adenine with minimal disruption to the sol-gel framework, thus enhancing the adenine solubility up to an order of magnitude as compared to water. Combined multinuclear (1H, 11B and 23Na) NMR spectroscopy analysis and vial inversion tests revealed that the nucleobases are embedded into pores of the sol phase rather than being closely interacting with the G-4 fibrils that make up the gel phase. These results indicate that G-4 hydrogels have potential applications as carrier systems for small molecules. Gel-state MAS NMR spectroscopy can be used to gain insight into host-guest interactions in complex heterogeneous sol-gel systems, which is often difficult to obtain from the conventional techniques such as X-ray scattering, electron microscopy and optical spectroscopy.
| Item Type: | Journal Article | ||||||||||||||||||||||||||||||
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| Subjects: | Q Science > QD Chemistry | ||||||||||||||||||||||||||||||
| Divisions: | Faculty of Science, Engineering and Medicine > Science > Chemistry Faculty of Science, Engineering and Medicine > Science > Life Sciences (2010- ) Faculty of Science, Engineering and Medicine > Science > Physics |
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| Library of Congress Subject Headings (LCSH): | Supramolecular chemistry, Heterocyclic compounds | ||||||||||||||||||||||||||||||
| Journal or Publication Title: | Materials Advances | ||||||||||||||||||||||||||||||
| Publisher: | Royal Society of Chemistry | ||||||||||||||||||||||||||||||
| ISSN: | 2633-5409 | ||||||||||||||||||||||||||||||
| Official Date: | 5 September 2020 | ||||||||||||||||||||||||||||||
| Dates: |
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| Volume: | 1 | ||||||||||||||||||||||||||||||
| Number: | 7 | ||||||||||||||||||||||||||||||
| Page Range: | pp. 2236-2247 | ||||||||||||||||||||||||||||||
| DOI: | 10.1039/D0MA00475H | ||||||||||||||||||||||||||||||
| Status: | Peer Reviewed | ||||||||||||||||||||||||||||||
| Publication Status: | Published | ||||||||||||||||||||||||||||||
| Access rights to Published version: | Open Access (Creative Commons) | ||||||||||||||||||||||||||||||
| Date of first compliant deposit: | 8 September 2020 | ||||||||||||||||||||||||||||||
| Date of first compliant Open Access: | 8 September 2020 | ||||||||||||||||||||||||||||||
| RIOXX Funder/Project Grant: |
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