Spectroscopic behavior differences between lumazine and alloxazine in the DMSO-water mixture

Jan Truksa; Matouš Kratochvíl; Jan Richtár; Lucia Ivanová; Martin Weiter; Jozef Krajčovič; Vladimír Lukeš

doi:10.1016/j.saa.2023.122998

Spectroscopic behavior differences between lumazine and alloxazine in the DMSO-water mixture

Spectrochim Acta A Mol Biomol Spectrosc. 2023 Dec 5:302:122998. doi: 10.1016/j.saa.2023.122998. Epub 2023 Jun 20.

Authors

Jan Truksa¹, Matouš Kratochvíl², Jan Richtár², Lucia Ivanová², Martin Weiter², Jozef Krajčovič³, Vladimír Lukeš⁴

Affiliations

¹ Faculty of Chemistry, Brno University of Technology, Purkyňova 118, CZ-612 00 Brno, Czech Republic. Electronic address: Jan.Truksa@vutbr.cz.
² Faculty of Chemistry, Brno University of Technology, Purkyňova 118, CZ-612 00 Brno, Czech Republic.
³ Faculty of Chemistry, Brno University of Technology, Purkyňova 118, CZ-612 00 Brno, Czech Republic; Dipartimento di Chimica, Università degli Studi di Bari Aldo Moro, via Orabona, 4-70125 Bari, Italy.
⁴ Institute of Physical Chemistry and Chemical Physics, Slovak University of Technology in Bratislava, Radlinského 9, SK-812 37 Bratislava, Slovakia.

PMID: 37356394
DOI: 10.1016/j.saa.2023.122998

Abstract

The absorption and emission spectra were investigated for lumazine, alloxazine and their cyanated or fluorinated derivatives, respectively. The spectroscopic properties were modulated by varying water concentration in dimethyl sulfoxide (DMSO). Some intriguing experimental results were found for the samples containing 65 % of water and 35% of DMSO. This finding is consistent with previously published molecular dynamics (MD) simulations confirming the concept of the 'local bulk' model. In this case, a notable decrease in absorption and emission intensities was registered, even larger than the water quenching observed in other cases. The changes in midrange DMSO concentrations could be explained by the formation of local solvents structures as predicted by MD, specifically the formation of DMSO·2H₂O dimers. Experimentally, the cyano-substituted lumazine has shown a remarkable sensitivity to DMSO concentration. The spectroscopic measurements were interpreted using the density functional theory where the implicit DMSO solvent model was combined with explicit water molecules. Together with its enhanced water solubility, the cyanated lumazine derivate could be used for non-destructive DMSO detection in vitro for applications such as drug uptake monitoring, since DMSO is often used in pharmaceutical practice.

Keywords: Bio-inspired Material; Flavins; Fluorescence; Lumazine; Tautomerisation; Vertical Excited States.