标题：Magnetic Dipole-Dipole Coupled Cu(II) Pairs in Nitric Oxide-Treated Tyrosinase: A Structural Relationship Between the Active Sites of Tyrosinase and Hemocyanin
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：1973
卷号：70
期号：4
页码：993-996
DOI：10.1073/pnas.70.4.993
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：The Tr and T[unk] states of tyrosinase were treated with NO. EPR spectra of the products observed at 14{degrees}K and at 113{degrees}K showed mixtures of two signals. One had components in the region of g = 2, about 1200 G wide, and in the region of g = 4, showing hyperfine splitting. The other signal was similar to that arising from isolated Cu(II) ions in an axially symmetric environment. The first signal was indicative of {Delta}m = 1 and {Delta}m = 2 transitions arising from magnetic dipole-dipole coupled Cu(II) ion pairs. It closely resembled previously reported EPR spectra obtained from NO-treated hemocyanin, which were confirmed in this study. The normal Curie behavior of the signals between 230{degrees}K and 14{degrees}K ruled out significant exchange coupling between the ion pairs. The {Delta}m = 2 signals were not saturable up to 350 mW at 14{degrees}K. The broad {Delta}m = 1 signals could be separated from accompanying signals by the saturation characteristics of the latter at about 10 mW at 14{degrees}K. The results establish the presence of a pair of copper ions at the active site of tyrosinase, and a clsoe structural relationship between this active site and that of hemocyanin.
关键词：O2 binding ; Cu proteins ; electron paramagnetic resonance
