Authors: Rieko Ishima
Publish Date: 2014/01/05
Volume: 58, Issue: 2, Pages: 113-122
Abstract
The magnitude of the 15N longitudinal relaxation rate typically decreases as magnetic field strength increases in globular proteins in solution Thus it is important to test the performance of 15N longitudinal relaxation experiments at high field strength Herein a tool to investigate systematic errors in 15N longitudinal relaxation rate R1 is introduced The tool a difference in R1 values between the two components of the 1Hcoupled 15N magnetizations R 1 1 –R 1 2 conveniently detects inefficiencies in cancellation of cross correlation between 1H–15N dipolar coupling and 15N chemical shift anisotropy Experiments in varying conditions and simulations of a twospin system indicate that insufficient cancellation of the cross correlation is due to 1 1H pulse imperfection and 2 1H offresonance effect and 3 is further amplified by residual 15N transverse magnetization that is caused by the 15N offresonance effect Results also show that this problem can be easily and practically remedied by discarding the initial decay points when recording 15N longitudinal relaxation in proteinsI thank Dennis Torchia and Teresa Brosenitsch for useful discussions and critical reading of the manuscript This study was financially supported by National Science Foundation research grant MCB 0814905 National institutes of health 5P50GM08225107 and University of Pittsburgh
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