{"id":746,"date":"2026-04-15T13:22:39","date_gmt":"2026-04-15T13:22:39","guid":{"rendered":"https:\/\/citations.tools.bio-logic.fr\/?p=746"},"modified":"2026-04-15T13:22:39","modified_gmt":"2026-04-15T13:22:39","slug":"biohybrid-photosynthetic-charge-accumulation-detected-by-flavin-semiquinone-formation-in-ferredoxin-nadpreductase","status":"publish","type":"post","link":"https:\/\/citations.tools.bio-logic.fr\/?p=746","title":{"rendered":"Biohybrid photosynthetic charge accumulation detected by flavin semiquinone formation in ferredoxin-NADP<sup>+<\/sup>reductase"},"content":{"rendered":"<h4>DOI:<\/h4>\n<p><a href=\"https:\/\/doi.org\/10.1039\/d2sc01546c\" target=\"_blank\" rel=\"noopener\">10.1039\/d2sc01546c<\/a><\/p>\n<h4>Authors:<\/h4>\n<p>Lisa M. Utschig, Udita Brahmachari, Karen L. Mulfort, Jens Niklas, Oleg G. Poluektov<\/p>\n<h4>Abstract:<\/h4>\n<p>Flavin chemistry is ubiquitous in biological systems with flavoproteins engaged in important redox reactions. In photosynthesis, flavin cofactors are used as electron donors\/acceptors to facilitate charge transfer and accumulation for ultimate use in carbon fixation. Following light-induced charge separation in the photosynthetic transmembrane reaction center photosystem I (PSI), an electron is transferred to one of two small soluble shuttle proteins, a ferredoxin (Fd) or a flavodoxin (Fld) (the latter in the condition of Fe-deficiency), followed by electron transfer to the ferredoxin-NADP<sup>+<\/sup> reductase (FNR) enzyme. FNR accepts two of these sequential one electron transfers, with its flavin adenine dinucleotide (FAD) cofactor becoming doubly reduced, forming a hydride which is then passed onto the substrate NADP<sup>+<\/sup> to form NADPH. The two one-electron potentials (oxidized\/semiquinone and semiquinone\/hydroquinone) are similar to each other with the FNR protein stabilizing the hydroquinone, making spectroscopic detection of the intermediate semiquinone state difficult. We employed a new biohybrid-based strategy that involved truncating the native three-protein electron transfer cascade PSI \u2192 Fd \u2192 FNR to a two-protein cascade by replacing PSI with a molecular Ru(ii) photosensitizer (RuPS) which is covalently bound to Fd and Fld to form biohybrid complexes that successfully mimic PSI in light-driven NADPH formation. RuFd \u2192 FNR and RuFld \u2192 FNR electron transfer experiments revealed a notable distinction in photosynthetic charge accumulation that we attribute to the different protein cofactors [2Fe2S] and flavin. After freeze quenching the two-protein systems under illumination, an intermediate semiquinone state of FNR was readily observed with cw X-band EPR spectroscopy. The increased spectral resolution from selective deuteration allowed EPR detection of inter-flavoprotein electron transfer. This work establishes a biohybrid experimental approach for further studies of photosynthetic light-driven electron transfer chain that culminates at FNR and highlights nature&rsquo;s mechanisms that couple single electron transfer chemistry to charge accumulation, providing important insight for the development of photon-to-fuel schemes.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>DOI: 10.1039\/d2sc01546c Authors: Lisa M. Utschig, Udita Brahmachari, Karen L. Mulfort, Jens Niklas, Oleg G. Poluektov Abstract: Flavin chemistry is ubiquitous in biological systems with flavoproteins engaged in important redox reactions. In photosynthesis, flavin cofactors are used as electron donors\/acceptors to facilitate charge transfer and accumulation for ultimate use in carbon fixation. Following light-induced charge [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[5],"tags":[],"class_list":["post-746","post","type-post","status-publish","format-standard","hentry","category-freeze-quench"],"_links":{"self":[{"href":"https:\/\/citations.tools.bio-logic.fr\/index.php?rest_route=\/wp\/v2\/posts\/746","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/citations.tools.bio-logic.fr\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/citations.tools.bio-logic.fr\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/citations.tools.bio-logic.fr\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/citations.tools.bio-logic.fr\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=746"}],"version-history":[{"count":0,"href":"https:\/\/citations.tools.bio-logic.fr\/index.php?rest_route=\/wp\/v2\/posts\/746\/revisions"}],"wp:attachment":[{"href":"https:\/\/citations.tools.bio-logic.fr\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=746"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/citations.tools.bio-logic.fr\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=746"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/citations.tools.bio-logic.fr\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=746"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}