Optimal-Control-Based Cβ Chemical Shift Encoding for Efficient Signal Assignment of Solid Proteins

Area of Science:

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

Background:

• Solid-state NMR spectroscopy is crucial for protein structural and dynamic analysis.
• Site-specific signal assignment, particularly Cα and Cβ chemical shifts, is vital for identifying amino acid residues.
• Conventional methods for Cβ chemical shift acquisition in solid proteins are limited by sensitivity drops due to long transverse evolution times.

Purpose of the Study:

• To develop a new method for efficient Cβ chemical shift acquisition in solid-state NMR.
• To overcome the sensitivity limitations associated with conventional Cβ chemical shift measurements.
• To enable faster and more accurate signal assignment for solid proteins.

Main Methods:

• Development of a novel Cβ-encoding method combining an optimal control-based spin manipulation pulse and a spin-state filter.
• Encoding Cβ chemical shifts onto the intensities of scalar-coupled Cα signals.
• Application of the method to microcrystalline protein GB1 for sequential signal assignment.

Main Results:

• The new method reduces the required transverse evolution time to less than half of previous methods.
• Total measurement time is shorter compared to explicit Cβ shift evolution.
• Successful sequential signal assignment was demonstrated for microcrystalline protein GB1.

Conclusions:

• The proposed Cβ-encoding nearest-neighbor NMR technique is applicable to solid proteins for the first time.
• This method offers improved efficiency and sensitivity for protein signal assignment.
• The approach holds promise for analyzing more complex protein systems.