A robust heteronuclear dipolar recoupling method comparable to TEDOR for proteins in magic-angle spinning solid-state...

Area of Science:

• Biophysical Chemistry
• Nuclear Magnetic Resonance Spectroscopy
• Structural Biology

Background:

• Magic-angle spinning (MAS) solid-state NMR is crucial for determining protein structures.
• Efficient heteronuclear dipolar recoupling is essential for magnetization transfer in MAS NMR.
• Existing methods like Transferred Echo Double Resonance (TEDOR) have limitations in efficiency and selectivity.

Purpose of the Study:

• To develop a robust and efficient heteronuclear dipolar recoupling method for protein studies in MAS solid-state NMR.
• To improve magnetization transfer efficiency between nitrogen-15 (¹⁵N) and carbon-13 (¹³C) nuclei.
• To offer a method comparable in simplicity and robustness to TEDOR but with enhanced performance.

Main Methods:

• Development of a broadband dual back-to-back pulse (Bro-DBP) sequence based on prior band-selective DBP methods.
• Implementation of new phase-cycling schemes to achieve broadband recoupling.
• Application and validation of the Bro-DBP method on a model peptide (fMLF) and a protein (GB1) sample labeled with ¹³C and ¹⁵N.

Main Results:

• The Bro-DBP method demonstrates robust and efficient broadband ¹⁵N-to-¹³C magnetization transfer.
• Bro-DBP achieves comparable ¹⁵N→¹³Cα transfer efficiency to TEDOR, with a 30-40% enhancement for ¹⁵N→¹³C' transfer.
• As a carbonyl (¹³C')-selected method, Bro-DBP shows up to 1.7 times higher ¹⁵N→¹³C' efficiency than TEDOR.

Conclusions:

• The broadband dual back-to-back pulse (Bro-DBP) method is a simple, robust, and efficient technique for heteronuclear recoupling in MAS solid-state NMR.
• Bro-DBP offers significant improvements in ¹⁵N-to-¹³C' magnetization transfer efficiency compared to TEDOR.
• This method is highly valuable for advancing structural studies of proteins using MAS solid-state NMR.