title: Nuclear relaxation effects in Davies ENDOR variants.
abstract: A recent article by Yang and Hoffman [T.-C. Yang, B.M. Hoffman, J. Magn. Reson., 181 (2006) 280] presents a 'Davies/Hahn ENDOR multi-sequence' in which the alpha and beta peaks of an electron-nuclear double resonance (ENDOR) spectrum can be distinguished. This represents one instance of a family of ENDOR sequences which have no initial microwave inversion pulse, and which can reveal information about nuclear relaxation rates and the signs of hyperfine coupling constants. Here we discuss the more general set of such sequences, which we refer to as Saturated Pulsed ENDOR, and show how signal sensitivity can be optimised within the context of this new technique. Through simulations, we compare its performance to other techniques based on Davies ENDOR, and experimentally illustrate its properties using the non-heme Fe enzyme anthranilate dioxygenase AntDO. Finally, we suggest a protocol for extracting both the magnitude and sign of the hyperfine tensor using a combination of ENDOR techniques.
authors.affiliation: Department of Materials, Oxford University, Oxford OX1 3PH, UK. john.morton@sjc.ox.ac.uk <john.morton@sjc.ox.ac.uk>
authors.forename: John J L
authors.initials: JJ
authors.lastname: Morton
authors.forename: Nicholas S
authors.initials: NS
authors.lastname: Lees
authors.forename: Brian M
authors.initials: BM
authors.lastname: Hoffman
authors.forename: Stefan
authors.initials: S
authors.lastname: Stoll
mesh_terms: D000465:Algorithms; D003198:Computer Simulation; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008956:Models, Chemical; D008958:Models, Molecular; D012815:Signal Processing, Computer-Assisted