Anomalous T7 Raman spin-lattice relaxation rate of low spin cytochrome P-450 from P s e u d o m o n a s p u t i d a

Abstract

Electron spin‐lattice relaxation measurements were made on camphor‐free low spin ferric cytochrome P‐450 from Pseudomonas putida. Data were taken between 1.75–13 K at X and Ku band microwave frequencies using the technique of pulse saturation recovery. The experiment revealed an anomalous Raman relaxation rate varying in the low temperature limit as T⁷ rather than T⁹, the latter being expected for a Kramers ion. We discuss this anomaly and show how it suggests that the ferric spin system relaxes to thermal equilibrium through interactions with a two dimensional phonon spectrum. The planar structure of the heme complex adds credibility to this interpretation.