Extending the distance range accessed with continuous wave EPR with Gd3+ spin probes at high magnetic fields.

ABSTRACT: Interspin distances between 0.8 nm and 2.0 nm can be measured through the dipolar broadening of the continuous wave (cw) EPR spectrum of nitroxide spin labels at X-band (9.4 GHz, 0.35 T). We introduce Gd(3+) as a promising alternative spin label for distance measurements by cw EPR above 7 Tesla, where the |-1/2〉 to |1/2〉 transition narrows below 1 mT and becomes extremely sensitive to dipolar broadening. To estimate the distance limits of cw EPR with Gd(3+), we have measured spectra of frozen solutions of GdCl3 at 8.6 T (240 GHz) and 10 K at concentrations ranging from 50 mM to 0.1 mM, covering a range of average interspin distances. These experiments show substantial dipolar broadening at distances where line broadening cannot be observed with nitroxides at X-band. This data, and its agre

SUBMITTER: Edwards DT 

PROVIDER: S-EPMC4142211 | biostudies-literature | 2013 Jul

REPOSITORIES: biostudies-literature