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Title:Electron spin resonance study of single crystals of cytochrome P450 from Pseudomonas putida
Author(s):Devaney, Patrick William
Doctoral Committee Chair(s):Debrunner, Peter G.
Department / Program:Physics
Discipline:Physics
Degree:Ph.D.
Genre:Dissertation
Subject(s):electron spin resonance
single crystals
cytochrome P450
Pseudomonas putida
ferric heme iron
Abstract:The magnetic properties of the ferric heme iron in single crystals of cytochrome P450 have been studied by electron spin resonance. Spectra were recorded for orthorhombic crystals (space group P222l , 114 molecules/ unit cell) of the native, substrate-free enzyme (mo),which showed a single signal of spin S=1/2, and of the camphor complex (mos), which showed a mixture of high-spin, S=5/2, and low-spin, 8=1/2, species. Complete angular scans were taken at 9.18 GHz and temperatures of 5K' (high-spin) or 15K (low-spin) to determine the orientation of the g-tensors with respect to the crystal axes. The results are expressed in terms of the Euler angles (alpha, beta, gamma) rotating the crystal axes (c,b,a) onto the g-tensor axes (x,y,z). The O best fits of (alpha, beta, gamma) were (0,-80.-100) for m , (3,-70,-103) for 8=1/2 os os m , and (O,-95.~115) for 8=5/2 m , ,where an accidental symmetry produces the sign ambiguity. The g-values of the various species were found to be (2.48,2.25, 1.91) for mO. (2.40,2.23.1.97) for 8=1/2 mOs, and (7.75,3.93,1.80) for S=5/2 mOs; these all differed slightly from the frozen solution values. The low-spin mossignals were purely from the 1.97 species as opposed to the mixture of 1.97 and 1.91 heretofore observed in solutions. The low-spin g=2.4 was assigned to g on the basis of its near coincidence with z the high-spin g=1.8 direction. which is known to be the heme normal. The linewidths measured in the single crystal studies were consistent with the crystal mosaic distortion plus g-strain model. Best fits for the linewidth simulations were obtained with the parameter values: delta-theta = 2.2Sofor crystal mosaic spread, delta-Delta = O.ISA, deltaV = O.ISA for low-spin g-strain, and delta-alpha = 0.004 for high-spin g-strain. Unresolved hyperfine broadening was assumed to be ISG in both species based on earlier heme protein studies.
Issue Date:1980
Genre:Dissertation / Thesis
Type:Text
Language:English
URI:http://hdl.handle.net/2142/25543
Rights Information:1980 Patrick William Devaney
Date Available in IDEALS:2011-06-28
Identifier in Online Catalog:438004


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