Eta(z)/kappa: a transverse relaxation optimized spectroscopy NMR experiment measuring longitudinal relaxation...

Area of Science:

• Biophysics
• Structural Biology
• Nuclear Magnetic Resonance (NMR) Spectroscopy

Background:

• NMR spin relaxation studies are crucial for measuring biomolecular dynamics.
• Current limitations restrict these studies to small biomolecules (<10 kDa).
• Measuring eta(z), a cross-correlated relaxation rate, is particularly challenging for larger proteins.

Purpose of the Study:

• To develop a new NMR experiment for measuring eta(z) in larger proteins (up to 30 kDa).
• To enable accurate interpretation of (15)N-NMR backbone relaxation experiments.
• To also measure kappa, the longitudinal (1)H(N)-(1)H(') DD cross relaxation rate.

Main Methods:

• A novel (1)H(N)-(15)N transverse relaxation optimized spectroscopy (TROSY) experiment was developed.
• The experiment measures eta(z) and kappa, providing insights into biomolecular dynamics.
• The method was tested on human ubiquitin, calmodulin/peptide complex, and E. coli DnaK ATPase domain.

Main Results:

• The new TROSY experiment successfully measures eta(z) in proteins up to 30 kDa.
• The experiment also quantifies kappa, the site-specific rate of longitudinal cross relaxation.
• Preliminary results demonstrate the experiment's applicability to various protein systems.

Conclusions:

• The developed NMR experiment overcomes previous technical limitations for studying larger biomolecules.
• This advancement enhances the understanding of protein backbone dynamics and improves NMR data interpretation.
• The method provides valuable insights into the variability of the (15)N chemical shift anisotropy tensor.