期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1970
卷号：67
期号：2
页码：682-687
DOI：10.1073/pnas.67.2.682
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Contact-shifted nuclear magnetic resonances, arising from molecular paramagnetism, have been observed in both reduced and oxidized forms of the high-potential iron protein (HiPIP) isolated from Chromatium. Contact shifts of the reduced, formally diamagnetic form increase with temperature, indicating antiferromagnetic exchange coupling of the component iron atoms with thermal population of a magnetic state. In the oxidized form of HiPIP (formally S = 1/2), contact-shifted resonances attributed to the {beta}-CH2 groups of two cysteine residues display approximate Curie law behavior, while contact-shifted resonances assigned to the two other cysteine residues continue to exhibit a temperature dependence characteristic of antiferromagnetic exchange coupling. A cluster model for the redox center of Chromatium HiPIP that appears compatible with the PMR and preliminary x-ray results4, 11 is discussed.
