Nitroxide Side-Chain Dynamics in a Spin-Labeled Helix-Forming Peptide Revealed by High-Frequency (139.5-GHz) EPR Spectroscopy

M. Bennati, G. J. Gerfen, G. V. Martinez, R. G. Griffin, D. J. Singel, G. L. Millhauser

Research output: Contribution to journalArticle

16 Scopus citations

Abstract

High-frequency electron paramagnetic resonance (EPR) spectroscopy has been performed on a nitroxide spin-labeled peptide in fluid aqueous solution. The peptide, which follows the single letter sequence Ac-(AAAAK)2CAAAKA-NH2 3K-11, was reacted with the methanethiosulfonate spin label at the cysteine sulfur. The spin sensitivity of high-frequency EPR is excellent with less than 20 pmol of sample required to obtain spectra with good signal-to-noise ratios. Simulation of the temperature-dependent spectral lineshapes reveals the existence of local anisotropic motion about the nitroxide N-O bond with a motional anisotropy τ (≡ N) approaching 2.6 at 306 K. Comparison with previous work on rigidly labeled peptides suggests that the spin label is reorienting about its side-chain tether. This study demonstrates the feasibility of performing 140-GHz EPR on biological samples in fluid aqueous solution.

Original languageEnglish (US)
Pages (from-to)281-286
Number of pages6
JournalJournal of Magnetic Resonance
Volume139
Issue number2
DOIs
StatePublished - Aug 1999

Keywords

  • Anisotropic motion
  • EPR
  • High frequency
  • Peptide
  • Side-chain dynamics

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Nuclear and High Energy Physics
  • Condensed Matter Physics

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