CPMG sequences with enhanced sensitivity to chemical exchange

Area of Science:

• Biophysical Chemistry
• Structural Biology
• Nuclear Magnetic Resonance (NMR) Spectroscopy

Background:

• Studying chemical exchange in biomolecules is crucial for understanding protein dynamics.
• Conventional methods for measuring nitrogen-15 (15N) relaxation rates are often confounded by proton-proton (1H-1H) interactions.
• Accurate quantification of chemical exchange requires isolating relaxation contributions.

Purpose of the Study:

• To develop improved relaxation-compensated Carr-Purcell-Meiboom-Gill pulse sequences.
• To enable the study of chemical exchange for backbone 15N nuclei.
• To facilitate the detection and quantification of chemical exchange processes.

Main Methods:

• Implementation of advanced relaxation-compensated Carr-Purcell-Meiboom-Gill pulse sequences.
• Measurement of phenomenological relaxation rate constants for 15N nuclei.
• Independent determination of relaxation rate constants from conventional 15N spin relaxation measurements.

Main Results:

• The new pulse sequences yield relaxation rate constants free from 1H-1H dipole-dipole interactions.
• Chemical exchange processes can be more readily detected and quantified.
• The method's utility is demonstrated using basic pancreatic trypsin inhibitor.

Conclusions:

• The developed NMR pulse sequences offer a significant improvement for studying protein dynamics.
• These sequences facilitate accurate characterization of chemical exchange in biomolecules.
• The method provides a more direct approach to measuring 15N relaxation rates.