{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,9,29]],"date-time":"2025-09-29T03:57:33Z","timestamp":1759118253867},"reference-count":0,"publisher":"Portland Press Ltd.","issue":"3","content-domain":{"domain":["portlandpress.com"],"crossmark-restriction":true},"short-container-title":[],"published-print":{"date-parts":[[1981,3,1]]},"abstract":"<jats:p>M.c.d. (magnetic-circular-dichroism) spectroscopy was used to study the magnetization properties of the haem centres in cytochrome c oxidase with magnetic fields of between 0 and 5.3 T over the temperature range 1.5\u2013200 K. The oxidized, oxidized cyanide and partially reduced cyanide forms of the enzyme were studied. In the oxidized state only cytochrome a3+ is detectable by m.c.d. spectroscopy, and its magnetization characteristics show it to be a low-spin ferric haem. In the partially reduced cyanide form of the enzyme cytochrome a is in the diamagnetic low-spin ferrous form, whereas cytochrome a3\u2013CN is e.p.r.-detectable and gives an m.c.d.-magnetization curve typical of a low-spin ferric haem. In the oxidized cyanide form of the enzyme both cytochrome a and cytochrome a3\u2013CN are detectable by m.c.d. spectroscopy, although only cytochrome a gives an e.p.r. signal. The magnetization characteristics of haem a3\u2013CN show clearly that its ground state is an electronic doublet and that another state, probably a spin singlet, lies greater than 10 cm-1 above this. These features are well accounted for by an electronic state of spin S = 1 with a predominantly axial distortion, which leaves the doublet, Ms = +\/- 1, as the ground state and the component Ms = 0 as the excited state. This state would not give an e.p.r. signal. Such an electronic state could arise either from a ferromagnetic coupling between haem a3+(3)-CN and the cupric ion, Cua3, or form a haem in the Fe(IV) state.<\/jats:p>","DOI":"10.1042\/bj1930687","type":"journal-article","created":{"date-parts":[[2015,8,10]],"date-time":"2015-08-10T20:26:12Z","timestamp":1439238372000},"page":"687-697","update-policy":"http:\/\/dx.doi.org\/10.1042\/crossmark_policy","source":"Crossref","is-referenced-by-count":48,"title":["A study of the magnetic properties of haem <i>a<\/i>3 in cytochrome <i>c<\/i> oxidase by using magnetic-circular-dichroism spectroscopy"],"prefix":"10.1042","volume":"193","author":[{"given":"A J","family":"Thomson","sequence":"first","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"M K","family":"Johnson","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"C","family":"Greenwood","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"P E","family":"Gooding","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"288","container-title":["Biochemical Journal"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/portlandpress.com\/biochemj\/article-pdf\/193\/3\/687\/564589\/bj1930687.pdf","content-type":"application\/pdf","content-version":"vor","intended-application":"syndication"},{"URL":"https:\/\/portlandpress.com\/biochemj\/article-pdf\/193\/3\/687\/564589\/bj1930687.pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2021,11,25]],"date-time":"2021-11-25T14:17:41Z","timestamp":1637849861000},"score":1,"resource":{"primary":{"URL":"https:\/\/portlandpress.com\/biochemj\/article\/193\/3\/687\/17890\/A-study-of-the-magnetic-properties-of-haem-a3-in"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[1981,3,1]]},"references-count":0,"journal-issue":{"issue":"3","published-print":{"date-parts":[[1981,3,1]]}},"URL":"https:\/\/doi.org\/10.1042\/bj1930687","relation":{},"ISSN":["0264-6021"],"issn-type":[{"value":"0264-6021","type":"print"}],"subject":[],"published":{"date-parts":[[1981,3,1]]}}}