High frequency electron paramagnetic resonance 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 was reacted with the methanethiosulfonate spin label at the cystein sulfur. The spin sensitivity of high frequency EPR is excellent with less than fifty nanograms 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-0 bond with a motional anisotropy ,rl/,rll (=- 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. The study demonstrated the feasibility of performing 140 GHz EPR on biological samples in fluid solution.

Agency
National Institute of Health (NIH)
Institute
National Center for Research Resources (NCRR)
Type
Biotechnology Resource Grants (P41)
Project #
2P41RR000995-24
Application #
6118650
Study Section
Project Start
1999-05-15
Project End
2000-04-30
Budget Start
1998-10-01
Budget End
1999-09-30
Support Year
24
Fiscal Year
1999
Total Cost
Indirect Cost
Name
Massachusetts Institute of Technology
Department
Type
DUNS #
City
Cambridge
State
MA
Country
United States
Zip Code
02139
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