A probe to monitor performance of ¹?N longitudinal relaxation experiments for proteins in solution.

ABSTRACT: The magnitude of the ¹?N longitudinal relaxation rate typically decreases as magnetic field strength increases in globular proteins in solution. Thus, it is important to test the performance of ¹?N longitudinal relaxation experiments at high field strength. Herein, a tool to investigate systematic errors in ¹?N longitudinal relaxation rate, R?, is introduced. The tool, a difference in R? values between the two components of the ¹H-coupled ¹?N magnetizations, R?(1)-R?(2), conveniently detects inefficiencies in cancellation of cross correlation between ¹H-¹?N dipolar coupling and ¹?N chemical shift anisotropy. Experiments, in varying conditions, and simulations of a two-spin system indicate that insufficient cancellation of the cross correlation is due to (1) ¹H pulse imperfection and (2) ¹H off-resonance effect, and (3) is further amplified by residual ¹?N transverse magnetization that is caused by the ¹?N off-resonance effect. Results also show that this problem can be easily and practically remedied by discarding the initial decay points when recording ¹?N longitudinal relaxation in proteins.

SUBMITTER: Ishima R 

PROVIDER: S-EPMC3951101 | biostudies-literature | 2014 Feb

REPOSITORIES: biostudies-literature