Electron spin-lattice relaxation of the [Cu(1.5) ... Cu(1.5)] dinuclear copper center in nitrous oxide reductase. Biophys J 1995 Dec;69(6):2761-9
Date
12/01/1995Pubmed ID
8599682Pubmed Central ID
PMC1236513DOI
10.1016/S0006-3495(95)80149-9Scopus ID
2-s2.0-0028857093 (requires institutional sign-in at Scopus site) 28 CitationsAbstract
Relaxation times have been obtained with time-domain EPR for the dinuclear mixed valence [CuA(1.5) ... CuA(1.5)[ S = 1/2 center in nitrous oxide reductase, N2OR, from Pseudomonas stutzeri, in the TN5 mutant defective in copper chromophore biosynthesis, in a synthetic mixed valence complex, and in type 1 and 2 copper complexes. Data confirmed that the intrinsic electron spin-lattice relaxation time, T1, for N2OR in the temperature range of 6-25 K is unusually short for copper centers. At best, a twofold increase of T1 from g perpendicular to g parallel was measured. Optimized fits of the saturation-recovery data were obtained using both double-exponential and stretched-exponential functions. The temperature dependence of the spin-lattice relaxation rate of mutant N2OR is about T5.0 with the stretched-exponential model or T3.3 and T3.9 for the model using the sum of two exponentials. These T1s are intrinsic to the mixed valence [CuA(1.5) ... CuA(1.5)] center, and no interaction of the second copper center in wild-type N2OR with the [CuA(1.5) ... CuA(1.5)] center has been observed. The T1 of the mixed valence center of N2OR is not only shorter than for monomeric square planar Cu(II) complexes, but also shorter than for a synthetic mixed valence complex, Cu2(N[CH2CH2NHCH2CH2NHCH2CH2]3N). The short T1 is attributed to the vibrational modes of type 1 copper and/or the metal-metal interaction in [CuA(1.5) ... CuA(1.5)].
Author List
Pfenninger S, Antholine WE, Barr ME, Hyde JS, Kroneck PM, Zumft WGMESH terms used to index this publication - Major topics in bold
Amino Acid SequenceAnimals
Binding Sites
Cattle
Copper
Electron Spin Resonance Spectroscopy
Electron Transport Complex IV
Kinetics
Molecular Sequence Data
Mutation
Oxidoreductases
Protein Structure, Secondary
Pseudomonas
Temperature
Thermodynamics
Time Factors
