Dependence of Distance Distributions Derived from Double Electron–Electron Resonance Pulsed EPR Spectroscopy on Pulse‐Sequence Time1. (10th March 2015)

• Record Type: Journal Article
• Authors: Baber, James L.; Louis, John M.; Clore, G. Marius
• Is Part Of: Angewandte Chemie. Volume 127:Number 18(2015)
• Page Start: 5426
• Page End: 5429
• Publication Date: 2015-03-10
• Subjects: Chemistry -- Periodicals; 540
• DOI: 10.1002/ange.201500640
• Languages: English
• ISSNs: 0044-8249

Abstract

<abstract abstract-type="main" xml:lang="en"> <title>Abstract</title> <p>Pulsed double electron–electron resonance (DEER) provides pairwise P(<italic>r</italic>) distance distributions in doubly spin labeled proteins. We report that in protonated proteins, P(<italic>r</italic>) is dependent on the length of the second echo period <italic>T</italic> owing to local environmental effects on the spin‐label phase memory relaxation time <italic>T</italic>_m. For the protein ABD, this effect results in a 1.4 Å increase in the P(<italic>r</italic>) maximum from <italic>T</italic>=6 to 20 μs. Protein A has a bimodal P(<italic>r</italic>) distribution, and the relative height of the shorter distance peak at <italic>T</italic>=10 μs, the shortest value required to obtain a reliable P(<italic>r</italic>), is reduced by 40 % relative to that found by extrapolation to <italic>T</italic>=0. Our results indicate that data at a series of <italic>T</italic> values are essential for quantitative interpretation of DEER to determine the extent of the <italic>T</italic> dependence and to extrapolate the results to <italic>T</italic>=0. Complete deuteration (99 %) of the protein was accompanied by a significant increase in <italic>T</italic>_m and effectively abolished the P(<italic>r</italic>) dependence on <italic>T</italic>.</p> </abstract>