Electron spin-lattice relaxation of the [Cu(1.5) ... Cu(1.5)] dinuclear copper center in nitrous oxide reductase
| Autor: | Walter G. Zumft, S. Pfenninger, P. M. H. Kroneck, James S. Hyde, M. E. Barr, William E. Antholine |
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| Rok vydání: | 1995 |
| Předmět: |
Time Factors
Molecular Sequence Data Inorganic chemistry Biophysics chemistry.chemical_element Nitrous-oxide reductase Protein Structure Secondary law.invention Electron Transport Complex IV law Pseudomonas Animals Amino Acid Sequence Electron paramagnetic resonance Binding Sites Valence (chemistry) Chemistry Relaxation (NMR) Electron Spin Resonance Spectroscopy Temperature Atmospheric temperature range Chromophore Copper Kinetics Crystallography Molecular vibration Mutation Thermodynamics Cattle Oxidoreductases Research Article |
| Zdroj: | Biophysical Journal. 69:2761-2769 |
| ISSN: | 0006-3495 |
| DOI: | 10.1016/s0006-3495(95)80149-9 |
| Popis: | 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)]. |
| Databáze: | OpenAIRE |
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