Proton evolved local field solid-state nuclear magnetic resonance using Hadamard encoding: theory and application to...

Area of Science:

• Nuclear Magnetic Resonance (NMR) spectroscopy
• Structural biology
• Materials science

Background:

• NMR anisotropic parameters, including dipolar couplings and chemical shifts, are crucial for determining the structure and orientation of aligned membrane proteins and liquid crystals.
• Proton evolved local field (PELF) experiments are valuable for measuring averaged dipolar couplings and probing molecular motions in such systems.
• Traditional PELF experiments necessitate acquiring multiple 2D datasets at varying mixing times, which can be time-consuming and limit sensitivity across the full range of dipolar couplings.

Purpose of the Study:

• To introduce a novel PELF experiment incorporating Hadamard encoding (HE) for enhanced sensitivity and efficiency.
• To enable the measurement of a broader range of dipolar couplings within a single 2D experiment.
• To accelerate the structural and dynamic characterization of aligned biological and material samples.

Main Methods:

• Development of a new PELF experiment utilizing Hadamard encoding (HE) through phase switching of hard pulses.
• Simultaneous detection of four spin operators, enabling the generation of two 2D spectra.
• Application of the HE-PELF scheme to U-(15)N NAL single crystals and U-(15)N labeled sarcolipin reconstituted in oriented lipid bicelles.

Main Results:

• The HE-PELF experiment demonstrates significantly higher sensitivity for a wide spectrum of dipolar couplings compared to conventional PELF.
• The method successfully characterizes both small molecules (NAL) and complex biological systems (sarcolipin in bicelles).
• The acquired data covers a broader range of dipolar couplings efficiently in a single experiment.

Conclusions:

• The proposed HE-PELF experiment offers a more sensitive and efficient approach for NMR studies of aligned samples.
• This technique can be broadly applied to various multidimensional NMR experiments for faster structural and dynamic analysis.
• The method holds promise for advancing the study of oriented membrane proteins and liquid crystalline materials.