title: An electron spin resonance spectral study of the dynamics of spin-labelled fatty acids bound to oxidoreductases.
abstract: Electron spin resonance (ESR) spectra have been recorded for 5-doxylstearate (I) and 16-doxylstearate (II) in the presence of bacterial luciferase and soybean lipoxygenase. The acids are inhibitors of the enzymes (Kd approximately 2 x 10(-5) M for II bound to luciferase). Using theoretical computer simulations of the ESR line shapes, an effective correlation time of tau eff approximately 3.7 x 10(-9) +/- 0.5 x 10(-9) s is found for the motion of spin label I bound to luciferase. Concentration-dependent sedimentation velocity experiments indicate luciferase is anisotropic and, assuming a prolate ellipsoid of axial ratio less than or equal to 9, a correlation time of tau a approximately 7.7 x 10(-9) s is predicted for rotation about the luciferase long axis. The tightly bound spin-labelled inhibitors, therefore, are proposed to give rise to ESR spectra chiefly reflecting luciferase long axis rotation. The ESR spectra of I and II, bound to lipoxygenase and to luciferase, appear similar.
mesh_terms: D055598:Chemical Phenomena; D002621:Chemistry; D003497:Cyclic N-Oxides / Q000378:metabolism*; D004578:Electron Spin Resonance Spectroscopy; D008084:Lipoxygenase / Q000378:metabolism*; D008156:Luciferases / Q000378:metabolism*; D013113:Spin Labels
chemical_list: D003497:Cyclic N-Oxides; D013113:Spin Labels; C005072:5-doxylstearic acid; C032363:16-nitroxystearic acid; D008084:Lipoxygenase; D008156:Luciferases