The ups and downs of Feher-style ENDOR

Peter E Doan*, R. J. Gurbiel, Brian M Hoffman

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

8 Scopus citations


A new transient variation of the "Feher-style" electron-nuclear double resonance (ENDOR) method is examined. In this technique, the passage-mode electron paramagnetic resonance (EPR) signal is monitored following the application of a pulsed radio frequency (RF). Continuous-wave and transient proton ENDOR experiments have been conducted on the nonheme iron center from the protein nitrile hydratase. These experiments show that the transient ENDOR signal response exhibits a complex response with multiple phases in the time evolution of the ENDOR signal. Both increases and decreases in the passage-mode EPR signals are observed at different times following the RF pulse that induces an ENDOR transition. A simple model based on a packet-shifting ENDOR mechanism for a nonadiabatic passage EPR signal is proposed. This model describes many of the features seen in the transient ENDOR experiments and provides new insight into the traditional Feher-style ENDOR measurements. This new model shows that a packet-shifting mechanism can account for many of the "negative ENDOR" effects commonly seen in Feher-style ENDOR, which suggests that more exotic ENDOR mechanisms may not be required to explain these observations.

Original languageEnglish (US)
Pages (from-to)649-663
Number of pages15
JournalApplied Magnetic Resonance
Issue number3-4
StatePublished - Jan 1 2007

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics


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