{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,30]],"date-time":"2026-07-30T19:01:57Z","timestamp":1785438117297,"version":"3.56.0"},"reference-count":65,"publisher":"National Academy of Sciences","issue":"30","license":[{"start":{"date-parts":[[2026,7,21]],"date-time":"2026-07-21T00:00:00Z","timestamp":1784592000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":["www.pnas.org"],"crossmark-restriction":true},"short-container-title":["Proc. Natl. Acad. Sci. U.S.A."],"published-print":{"date-parts":[[2026,7,28]]},"abstract":"<jats:p>\n                    Photosystem I (PSI) converts light into chemical energy with near-unity quantum efficiency, yet its energy-transfer and charge-separation mechanisms remain debated. Evolution has diversified PSI architectures: Cyanobacterial PSI trimers confine red-shifted pigments to the core, whereas plant PSI-Light Harvesting Complex Isupercomplexes incorporate extensive peripheral red and charge-transfer states that reshape trapping. The unicellular red alga\n                    <jats:italic toggle=\"yes\">Cyanidioschyzon merolae<\/jats:italic>\n                    exemplifies functional diversification across distinct evolutionary branches, combining a photosystem II and plant-like monomeric PSI core associated with a varying number of light harvesting antenna subunits, Light Harvesting Complexes from Red Lineage (LHCR). This hybrid organization functionally bridges mechanistic models across different lineages. We applied two-dimensional electronic spectroscopy at ultralow temperatures (8 and 80 K) to disentangle overlapping excitation pathways in\n                    <jats:italic toggle=\"yes\">C. merolae<\/jats:italic>\n                    PSI. Cryogenic measurements suppressed thermal broadening, resolving five dynamical components: subpicosecond equilibration (0.3 to 0.8 ps) across the core\u2013LHCR interface, subsequent population transfer (2.6 to 4 ps) into progressively lower-energy manifolds, and slower feeding (18 to 53 ps) into red pools distributed across both core and antenna. On the longest timescales (hundreds of ps), a persistent ground-state bleach signifies excitons stabilized in terminal sinks. Notably, comparison of 8 K and 80 K spectra reveals that excitations are heterogeneously partitioned among multiple sinks at low disorder, whereas modest thermal activation (kT\n                    <jats:inline-formula>\n                      <mml:math xmlns:mml=\"http:\/\/www.w3.org\/1998\/Math\/MathML\" display=\"inline\" overflow=\"scroll\">\n                        <mml:mo>\u223c<\/mml:mo>\n                      <\/mml:math>\n                    <\/jats:inline-formula>\n                    55 cm\n                    <jats:sup>\u22121<\/jats:sup>\n                    ) promotes selective convergence into core-associated red chlorophylls. Atomistic excitonic modeling with time-nonlocal master equations supports these observations, revealing temperature-dependent energy redistribution. Overall,\n                    <jats:italic toggle=\"yes\">C. merolae<\/jats:italic>\n                    PSI expands the kinetic funnel by distributing trapping sites, enhancing spectral coverage while maintaining high efficiency, which is an important functional diversification during evolution.\n                  <\/jats:p>","DOI":"10.1073\/pnas.2530661123","type":"journal-article","created":{"date-parts":[[2026,7,21]],"date-time":"2026-07-21T18:00:45Z","timestamp":1784656845000},"update-policy":"https:\/\/doi.org\/10.1073\/pnas.cm10313","source":"Crossref","is-referenced-by-count":0,"title":["Excitonic energy transfer in red algal Photosystem I reveals an evolutionary bridge between cyanobacteria and plants"],"prefix":"10.1073","volume":"123","author":[{"ORCID":"https:\/\/orcid.org\/0009-0006-2289-9717","authenticated-orcid":false,"given":"Mengyuan","family":"Cui","sequence":"first","affiliation":[{"id":[{"id":"https:\/\/ror.org\/03et85d35","id-type":"ROR","asserted-by":"publisher"}],"name":"Department of Physics, School of Physical Science and Technology, Ningbo University","place":["Ningbo, People\u2019s Republic of China"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8825-1909","authenticated-orcid":false,"given":"Zihui","family":"Liu","sequence":"additional","affiliation":[{"id":[{"id":"https:\/\/ror.org\/03et85d35","id-type":"ROR","asserted-by":"publisher"}],"name":"Department of Physics, School of Physical Science and Technology, Ningbo University","place":["Ningbo, People\u2019s Republic of China"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4586-610X","authenticated-orcid":false,"given":"Miriam","family":"Izzo","sequence":"additional","affiliation":[{"id":[{"id":"https:\/\/ror.org\/039bjqg32","id-type":"ROR","asserted-by":"publisher"}],"name":"Solar Fuels Laboratory, Center of New Technologies, University of Warsaw","place":["Warsaw, Poland"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Junhua","family":"Zhou","sequence":"additional","affiliation":[{"id":[{"id":"https:\/\/ror.org\/03et85d35","id-type":"ROR","asserted-by":"publisher"}],"name":"Department of Physics, School of Physical Science and Technology, Ningbo University","place":["Ningbo, People\u2019s Republic of China"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0002-1241-094X","authenticated-orcid":false,"given":"Enhu","family":"He","sequence":"additional","affiliation":[{"id":[{"id":"https:\/\/ror.org\/03et85d35","id-type":"ROR","asserted-by":"publisher"}],"name":"Department of Physics, School of Physical Science and Technology, Ningbo University","place":["Ningbo, People\u2019s Republic of China"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Vandana","family":"Tiwari","sequence":"additional","affiliation":[{"id":[{"id":"https:\/\/ror.org\/05gzmn429","id-type":"ROR","asserted-by":"publisher"}],"name":"Stanford PULSE Institute, SLAC National Accelerator Laboratory","place":["Menlo Park"]},{"id":[{"id":"https:\/\/ror.org\/05gzmn429","id-type":"ROR","asserted-by":"publisher"}],"name":"Department of Chemical Science, Linac Coherent Light Source, SLAC National Accelerator Laboratory","place":["Menlo Park"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-5147-153X","authenticated-orcid":false,"given":"Petar H.","family":"Lambrev","sequence":"additional","affiliation":[{"id":[{"id":"https:\/\/ror.org\/016gb1631","id-type":"ROR","asserted-by":"publisher"}],"name":"Biological Research Centre","place":["Szeged, Hungary"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0884-0541","authenticated-orcid":false,"given":"R. 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