Conformational Switching Controls Biradical Spin Dynamics in Flavin–Tryptophan Dyads

Conformational Switching Controls Biradical Spin Dynamics in Flavin–Tryptophan Dyads Full article

Journal

Journal of the American Chemical Society
ISSN: 0002-7863

Output data

Year: 2026, DOI: 10.1021/jacs.5c22947

Authors

Musabirova Guzel ¹ , Morozova Olga B. ² , Kiryutin Alexey S. ² , Anisimova Irina S. ³ , Zhukov Ivan V. ² , Theiss Tobias ¹ , Gerhards Luca ³ , Zoller Ben G.E. ⁴ , Gulder Tanja ^1,4 , Matysik Jörg ¹ , Solov’yov Ilia A. ³ , Yurkovskaya Alexandra V. ²

Affiliations

1	Department of Analytical Chemistry, Leipzig University, 04103 Leipzig, Germany
2	Siberian Branch of the Russian Academy of Science, International Tomography Center, 630090 Novosibirsk, Russia
3	Institute of Physics, Carl von Ossietzky Universität, 26129 Oldenburg, Germany
4	Organic Chemistry, Saarland University, 66123 Saarbrücken, Germany

Flavin−tryptophan dyads linked by oligoproline chains were used to probe how proline cis−trans isomerization modulates spin dynamics under photo-CIDNP conditions. Field-cycling NMR revealed that minor cis−containing conformers form compact geometries that support intramolecular biradical recombination. These states display the features of J-resonance photo-CIDNP: uniform emissive polarization and pronounced maxima at 5−20 mT, while their signals vanish at high fields. In contrast, the dominant all-trans (PPII) conformers and longer linkers produce only Δg dominated patterns consistent with intermolecular radical encounters. Time-resolved photo-CIDNP confirmed that intermolecular processes prevail in most systems, with the fourproline dyad showing additional intramolecular contributions. The results establish that proline isomerization serves as a structural switch that governs the donor−acceptor distance and, consequently, the balance between intra- and intermolecular spin-selective pathways. The study further highlights field-cycling photo-CIDNP as a promising tool for identifying transient biradical states in biomolecular model systems.

Musabirova G. , Morozova O.B. , Kiryutin A.S. , Anisimova I.S. , Zhukov I.V. , Theiss T. , Gerhards L. , Zoller B.G.E. , Gulder T. , Matysik J. , Solov’yov I.A. , Yurkovskaya A.V.
Conformational Switching Controls Biradical Spin Dynamics in Flavin–Tryptophan Dyads
Journal of the American Chemical Society. 2026. DOI: 10.1021/jacs.5c22947 OpenAlex

Submitted:	Dec 22, 2025
Accepted:	Feb 27, 2026
Published online:	Mar 23, 2026

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