Accelerated ¹⁹F biomolecular magic-angle spinning NMR with paramagnetic dopants.

Area of Science:

• Biophysical Chemistry
• Structural Biology
• Nuclear Magnetic Resonance Spectroscopy

Background:

• Fluorine-19 (19F) nucleus is increasingly utilized in Nuclear Magnetic Resonance (NMR) for its advantageous properties.
• Solid-state magic-angle spinning (MAS) NMR of fluorine-labelled samples offers structural insights into proteins and long-distance measurements.
• Low sensitivity in 19F MAS NMR, often due to slow longitudinal T1 relaxation, limits experimental efficiency.

Purpose of the Study:

• To investigate the application of paramagnetic doping to reduce T1 relaxation times in 19F-labelled biological samples for MAS NMR.
• To evaluate the effect of gadolinium chelates (Gd(DTPA) and Gd(DTPA-BMA)) on 19F and 13C relaxation times (T1 and T2).
• To assign chemical shifts of fluorotryptophan signals in a large protein (TET2) using mutagenesis.

Main Methods:

• Utilized paramagnetic doping with Gd(DTPA) and Gd(DTPA-BMA) on a [5-19F13C]-tryptophan-labelled protein.
• Conducted 19F-detected MAS NMR experiments to measure 19F and 13C T1 and T2 relaxation times.
• Employed a mutagenesis approach for chemical shift assignment of fluorotryptophan residues in the protein TET2.

Main Results:

• Paramagnetic relaxation enhancement significantly reduced measurement times for 19F MAS NMR experiments.
• Sensitivity was improved without compromising spectral resolution.
• Successfully assigned all four fluorotryptophan signals in the 12 x 39 kDa protein TET2.

Conclusions:

• Paramagnetic doping is an effective strategy to accelerate 19F T1 relaxation in biomolecular MAS NMR.
• This approach enhances experimental efficiency, enabling faster structural studies of biological macromolecules.
• The study provides valuable insights into the application of 19F MAS NMR for protein structure determination.