Evaluation and optimization of coherence transfer in high molecular weight systems

Area of Science:

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

Background:

• Large proteins present challenges for NMR due to slow tumbling and large chemical shift anisotropy (CSA).
• Existing TROSY experiments can suffer from reduced coherence transfer efficiency for large biomolecules.
• Unambiguous sequential backbone assignment is crucial for determining protein structure and function.

Purpose of the Study:

• To evaluate the coherence transfer efficiency of various TROSY experiments for large proteins.
• To introduce and assess novel NMR experiments, MP-HNCA and HN(CO)CANH, for sequential backbone assignment.
• To provide improved methods for analyzing large protein structures using NMR.

Main Methods:

• Evaluation of coherence throughput in several TROSY-based NMR experiments.
• Introduction and theoretical analysis of two new experiments: MP-HNCA and HN(CO)CANH.
• Experimental validation on a 60.8 kDa homodimer of protein Cel6A at 800 MHz proton frequency.

Main Results:

• The new MP-HNCA and HN(CO)CANH experiments demonstrate significantly better theoretical coherence transfer efficiencies.
• These improvements are particularly notable for interresidual (13)C(alpha) correlations.
• Enhanced efficiency was observed even for large protein complexes like the Cel6A homodimer.

Conclusions:

• MP-HNCA and HN(CO)CANH are effective alternatives for sequential backbone assignment in large proteins.
• These methods overcome limitations imposed by large chemical shift anisotropy (CSA) in high magnetic fields.
• The developed NMR techniques facilitate structural studies of challenging biomolecules.