Abstract In studies of membrane proteins, knowledge of protein topology can provide useful insight into both structure and function. In this work, we present a solution NMR method for the measurement the tilt angle and average immersion depth of alpha helices in membrane proteins, from analysis of the paramagnetic relaxation rate enhancements arising from dissolved oxygen. No modification to the micelle or protein is necessary, and the topology of both transmembrane and amphipathic helices are readily determined. We apply this method to the measure the topology of a monomeric mutant of phospholamban (AFA-PLN), a 52-residue membrane protein containing both an amphipathic and a transmembrane alpha helix. In dodecylphosphocholine micelles, the amphipathic helix of AFA-PLN was found to have a tilt angle of 87° ± 1° and an average immersion depth of 13.2 �. The transmembrane helix was found to have an average immersion depth of 5.4 �, indicating residues 41 and 42 are closest to the micelle centre. The resolution of paramagnetic relaxation rate enhancements from dissolved oxygen compares favourably to those from Ni (II), a hydrophilic paramagnetic species.
Content Type Journal Article
Category Article
Pages 173-183
DOI 10.1007/s10858-011-9551-z
Authors
M. Sameer Al-Abdul-Wahid, Department of Chemistry, University of Toronto Mississauga, Mississauga, ON L5L 1C6, Canada
Raffaello Verardi, Department of Chemistry, University of Minnesota, Minneapolis, MN 55455, USA
Gianluigi Veglia, Department of Chemistry, University of Minnesota, Minneapolis, MN 55455, USA
R. Scott Prosser, Department of Chemistry, University of Toronto Mississauga, Mississauga, ON L5L 1C6, Canada
[Question from NMRWiki Q&A forum] paramagnetic oxygen in solution NMR
paramagnetic oxygen in solution NMR
A student is running a kinetics experiment in a J-Young tube under 5-10 atm of oxygen, much like in this journal article:http://pubs.acs.org/doi/abs/10.1021/ja9061932
Student is seeing reduction in signal from his compound (slightly polar) and his internal standard (non-polar). Obviously paramagnetic oxygen?
The part I can't figure out: student is NOT seeing a reduction in his solvent peak. Solvent is benzene or toluene. I am assuming he is using at least some deuterated solvent.
I have found a lot of literature on the interaction of paramagnetic...
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http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jacsat/0/jacsat.ahead-of-print/ja109469c/aop/images/medium/ja-2010-09469c_0004.gif
Journal of the American Chemical Society
DOI: 10.1021/ja109469c
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