title: Pulsed electron-nuclear double resonance (ENDOR) at 140 GHz.
abstract: We describe a spectrometer for pulsed ENDOR at 140 GHz, which is based on microwave IMPATT diode amplifiers and a probe consisting of a TE011 cavity with a high-quality resonance circuit for variable radiofrequency irradiation. For pulsed EPR we obtain an absolute sensitivity of 3x10(9) spins/Gauss at 20 K. The performance of the spectrometer is demonstrated with pulsed ENDOR spectra of a standard bis-diphenylene-phenyl-allyl (BDPA) doped into polystyrene and of the tyrosyl radical from E. coli ribonucleotide reductase (RNR). The EPR spectrum of the RNR tyrosyl radical displays substantial g-anisotropy at 5 T and is used to demonstrate orientation-selective Davies-ENDOR.
authors.affiliation: Francis Bitter Magnet Laboratory and Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
authors.forename: M
authors.initials: M
authors.lastname: Bennati
authors.forename: C T
authors.initials: CT
authors.lastname: Farrar
authors.forename: J A
authors.initials: JA
authors.lastname: Bryant
authors.forename: S J
authors.initials: SJ
authors.lastname: Inati
authors.forename: V
authors.initials: V
authors.lastname: Weis
authors.forename: G J
authors.initials: GJ
authors.lastname: Gerfen
authors.forename: P
authors.initials: P
authors.lastname: Riggs-Gelasco
authors.forename: J
authors.initials: J
authors.lastname: Stubbe
authors.forename: R G
authors.initials: RG
authors.lastname: Griffin
mesh_terms: D000498:Allyl Compounds / Q000737:chemistry; D016880:Anisotropy; D001555:Benzene Derivatives / Q000737:chemistry; D003198:Computer Simulation; D004578:Electron Spin Resonance Spectroscopy / Q000295:instrumentation / Q000379:methods*; D004926:Escherichia coli / Q000201:enzymology; D005609:Free Radicals; D008280:Magnetics; D011137:Polystyrenes; D011522:Protons; D011846:Radio Waves; D012264:Ribonucleotide Reductases / Q000737:chemistry*; D012680:Sensitivity and Specificity; D013057:Spectrum Analysis; D013113:Spin Labels; D014159:Transducers; D014443:Tyrosine
chemical_list: D000498:Allyl Compounds; D001555:Benzene Derivatives; D005609:Free Radicals; D011137:Polystyrenes; D011522:Protons; D013113:Spin Labels; D014443:Tyrosine; D012264:Ribonucleotide Reductases