{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,8,27]],"date-time":"2026-08-27T10:32:18Z","timestamp":1787826738100,"version":"build-2784847793"},"reference-count":0,"publisher":"National Academy of Sciences","issue":"4","content-domain":{"domain":["www.pnas.org"],"crossmark-restriction":true},"short-container-title":["Proc. Natl. Acad. Sci. U.S.A."],"published-print":{"date-parts":[[1976,4]]},"abstract":"<jats:p>The contributions of the alpha and beta heme groups to the absorbance change that accompanies the aggregation of hemoglobin subunits were measured by comparing the extinction changes produced by n-butyl isocyanide binding to deoxyhemoglobin A with those produced by binding of n-butyl isocyanide to the isolated chains. Almost the entire aggregation absorbance change is associated with the unliganded alpha subunits, which exhibit a 30% increase in molar extinction at 428 nm during tetramer formation. This marked spectral change indicates a substantial perturbation of the electronic properties of the alpha heme groups in going from the high-affinity, isolated chain state to the low-affinity, tetrameric state. The lack of a significant absorbance change as sociated with the beta heme groups implies that the change in reactivity of unliganded beta subunits produced by aggregation is not the result of a change in spin or coordination geometry of the iron atom, but rather involves primarily an alteration in the protein structure near the sixth coordination position.<\/jats:p>","DOI":"10.1073\/pnas.73.4.1140","type":"journal-article","created":{"date-parts":[[2006,5,31]],"date-time":"2006-05-31T03:16:31Z","timestamp":1149045391000},"page":"1140-1144","update-policy":"https:\/\/doi.org\/10.1073\/pnas.cm10313","source":"Crossref","is-referenced-by-count":15,"title":["Spectral differences between the alpha and beta heme groups within human deoxyhemoglobin."],"prefix":"10.1073","volume":"73","author":[{"given":"J S","family":"Olson","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"341","published-online":{"date-parts":[[1976,4]]},"container-title":["Proceedings of the National Academy of Sciences"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/pnas.org\/doi\/pdf\/10.1073\/pnas.73.4.1140","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2022,4,13]],"date-time":"2022-04-13T11:13:10Z","timestamp":1649848390000},"score":1,"resource":{"primary":{"URL":"https:\/\/pnas.org\/doi\/full\/10.1073\/pnas.73.4.1140"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[1976,4]]},"references-count":0,"journal-issue":{"issue":"4","published-print":{"date-parts":[[1976,4]]}},"alternative-id":["10.1073\/pnas.73.4.1140"],"URL":"https:\/\/doi.org\/10.1073\/pnas.73.4.1140","relation":{},"ISSN":["0027-8424","1091-6490"],"issn-type":[{"value":"0027-8424","type":"print"},{"value":"1091-6490","type":"electronic"}],"subject":[],"published":{"date-parts":[[1976,4]]},"assertion":[{"value":"1976-04-01","order":2,"name":"published","label":"Published","group":{"name":"publication_history","label":"Publication History"}}]}}