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Stapleton, H.J. Herrick, Richard Charles 2011-07-05T19:02:11Z 2011-07-05T19:02:11Z 10000-01-01 1976 Electron spin-lattice relaxation measurements have been taken on o camphor-free low-spin ferric cytochrome P-450 (mo) and the high-spin species of camphor-bound cytochrome P-450 (mos). Relaxation rates were measured at x-and Ku-band frequencies using the technique of pulse-saturation recovery. The data for the low-spin species revealed an anomalous Raman 7 relaxation rate varying in the low temperature limit as T rather than T9 , the latter being expected for a Kramers ion. This anomaly is discussed and it is shown how the data suggests that the spins relax to thermal equilibrium through interactions with an effective two dimensional phonon spectrum. This hypothesis seems credible in view of the planar structure of the heme ring. For the high-spin species of substrate-bound P-450, relaxation rates were found to be Orbach-dominated down to temperatures of 1.5 K, with both excited states in the S = 25 manifold contributing to the relaxation rate. The data were therefore fit to two Orbach processes which placed the excited state energies at 9.5 ± 2.8 K and 29.8 ± 1.9 K above the ground doublet for the first and second excited states, respectively. If the two excited energy levels are related to a single ligand field parameter, D, using the constraint imposed by the measured g-values of the ground doublet, then a fit of the relaxation data gives the values: D = 5.0 ± 0.2 K and E = 0.087D = 0.435 ± 0.02 K. These parameters in turn place the excited doublets at 10.7 ± 0.5 K and 30.5 ± 1.2 K, which are consistent with the constraint-free determination. Submitted by Carolyn Mead (cmead2@illinois.edu) on 2011-07-05T19:02:11Z No. of bitstreams: 1 1976_herrick.pdf: 6535814 bytes, checksum: 288826c9f4465ce5524da2e648412dcd (MD5) Made available in DSpace on 2011-07-05T19:02:11Z (GMT). No. of bitstreams: 1 1976_herrick.pdf: 6535814 bytes, checksum: 288826c9f4465ce5524da2e648412dcd (MD5) Previous issue date: 1976 Item marked as restricted to the 'UIUC Users [automated]' Group (id=2) by Carolyn Mead (cmead2@illinois.edu) on 2011-07-05T19:02:11Z Item is restricted indefinitely. Restriction data tranferred 2014-07-01T11:32:41-05:00 Original Data Group with Access UIUC Users [automated] Release Date: none Reason: Thesis Thesis U of I Only 1006796 http://hdl.handle.net/2142/25662 en 1976 Richard Charles Herrick electron spin-lattic relaxation cytochrome P-450 Pseudomonas putida low-spin ferric cytochrome relaxation rates Electron spin-lattice relaxation of cytochrome P-450 from Pseudomonas putida Dissertation / Thesis text Physics Physics University of Illinois at Urbana-Champaign Dissertation Ph.D.