{"doi":"10.1021/jacs.5c05261","title":"Description of the Electronic Structure of Oxyhemoglobin Using Fe L-Edge X-ray Absorption Spectroscopy","abstract":"The electronic structure of oxyhemoglobin has been controversial since the discovery of the compound’s diamagnetism in 1936. This study uses partial fluorescence yield Fe L-edge X-ray absorption spectroscopy (XAS) in the 3s→2p fluorescence on oxyhemoglobin solutions, measured using a transition-edge sensor detector, to obtain a quantitative experimental description of the electronic structure of the O 2 -bound iron site. The spectrum is very different from typical low-spin Fe II and Fe III heme spectra, and multiplet simulations indicate a mixed ground configuration with ∼57% low-spin Fe III and ∼43% low-spin Fe II character. This is also very different from the Fe II character found for the picket-fence porphyrin model complex. The oxyhemoglobin L-edge XAS data further show that the O 2 ligand engages in a weak σ- but strong π-bond with the iron ion, leading to the overall strong Fe–O 2 bond required for O 2 transport.","journal":"Journal of the American Chemical Society","year":2025,"id":541458,"datarank":0.0,"base_score":0.0,"endowment":0.0,"self_citation_contribution":0.0,"citation_network_contribution":0.0,"self_endowment_contribution":0.0,"citer_contribution":0.0,"corpus_percentile":null,"corpus_rank":null,"citation_count":2,"citer_count":0,"citers_with_citation_signal":0,"citers_with_endowment":0,"datacite_reuse_total":0,"is_dataset":false,"is_dataset_confidence":0.9541,"is_data_producer":false,"deposit_databanks":null,"is_oa":true,"file_count":0,"downloads":0,"has_version_chain":false,"published_date":"2025-01-01","fair_score":null,"fair_percentile":null,"algorithm_id":"datarank_citation_only_1hop_v6","ranking_scope":"data_only","authors":[{"id":451217,"name":"Charles J. Titus","orcid":"0000-0001-6312-8552","position":1,"is_corresponding":false},{"id":299419,"name":"Leland B. Gee","orcid":"0000-0002-5817-3997","position":2,"is_corresponding":false},{"id":414292,"name":"Michael L. Baker","orcid":"0000-0002-8246-3177","position":3,"is_corresponding":false},{"id":1281764,"name":"Max D. J. Waters","orcid":"0000-0002-3505-627X","position":4,"is_corresponding":false},{"id":361412,"name":"James J. Yan","orcid":"0000-0001-5516-3446","position":5,"is_corresponding":false},{"id":644655,"name":"Sang‐Jun Lee","orcid":"0000-0002-8199-3993","position":6,"is_corresponding":false},{"id":484772,"name":"Dennis Nordlund","orcid":"0000-0001-9524-6908","position":7,"is_corresponding":false},{"id":943976,"name":"W. B. Doriese","orcid":"0000-0003-1107-6441","position":8,"is_corresponding":false},{"id":943977,"name":"G. C. O’Neil","orcid":"0000-0003-3450-2263","position":9,"is_corresponding":false},{"id":1429788,"name":"Daniel Schmidt","orcid":"0009-0009-1627-5790","position":10,"is_corresponding":false},{"id":943978,"name":"Daniel S. Swetz","orcid":"0000-0002-8192-2175","position":11,"is_corresponding":false},{"id":943979,"name":"Joel N. Ullom","orcid":"0000-0003-2486-4025","position":12,"is_corresponding":false},{"id":943980,"name":"K. D. Irwin","orcid":"0000-0002-2998-9743","position":13,"is_corresponding":false},{"id":271050,"name":"Edward I. Solomon","orcid":"0000-0003-0291-3199","position":14,"is_corresponding":false},{"id":665151,"name":"Augustin Braun","orcid":"0000-0002-9487-5769","position":0,"is_corresponding":true}],"reference_count":52,"raw_metadata":null,"created_at":"2026-07-19T02:52:47.161928Z","pmid":"40498961","pmcid":null,"fwci":null,"citation_percentile":null,"influential_citations":0,"oa_status":null,"license":null,"views":0,"total_file_size_bytes":0,"version_count":0,"fair_f":null,"fair_a":null,"fair_i":null,"fair_r":null,"fair_zscore":null,"fair_rationale":null,"fair_model":null,"fair_agent_version":null,"fair_fulltext_source":null,"fair_has_llm":null,"fair_computed_at":null,"clinical_trials":[],"software_tools":[],"db_accessions":[],"linked_datasets":[],"topics":[]}