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：1978
卷号：75
期号：7
页码：3019-3022
DOI：10.1073/pnas.75.7.3019
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：The magnetic susceptibility of Rhus vernicifera laccase has been remeasured over the temperature range 5-260 K. In contrast to our previous results [Solomon, E.I., Dooley, D. M., Wang R.-H., Gray, H.B., Cerdonio, M., Mogno, F. & Romani, G. L. (1975) J. Am. Chem. Soc. 98, 1029-1031] linear chi versus T-1 behavior was observed. The susceptibility of Limulus polyphemus oxyhemocyanin has also been measured in the range 5-260 K. Only weak paramagnetism, attributable to dissolved oxygen and a small amount of paramagnetic impurities, was observed. Analysis of the data establishes a lower limit of 550 cm-1 for J, consistent with our earlier work. The temperature dependence of the susceptibility of laccase is quantitatively accounted for by the presence of two paramagnetic copper ions (types 1 and 2) per enzyme molecule. Curie law behavior at low temperatures rules out significant interaction between the two coppper types, indicating that these redox centers are well separated (several angstroms) and are not connected by bridging ligands. Formulation of the type 3 site as binuclear Cu(II) requires J greater than or equal to 500 cm-1.
