Optimization of CEST MRI Reporter Protein Design Using Cation-Pi Networks

Area of Science:

• Biomedical Imaging
• Molecular Biology
• Therapeutic Development

Background:

• Nucleic acid-based therapies require noninvasive methods for tracking delivery, persistence, and spread.
• Chemical Exchange Saturation Transfer (CEST) reporter proteins offer high sensitivity for MRI detection.
• Existing CEST reporter proteins lack specificity due to overlapping signals with endogenous proteins.

Purpose of the Study:

• To investigate proteins and peptides with tyrosine, tryptophan, and lysine residues for enhanced MRI reporter gene applications.
• To identify biomarkers that provide distinct CEST contrast away from endogenous signals for improved specificity.
• To enable noninvasive in vivo monitoring of viral and gene therapies using MRI.

Main Methods:

• Screening of proteins and peptides containing tyrosine, tryptophan, and lysine residues.
• Analysis of chemical exchange saturation transfer (CEST) properties, including downfield shifts (4-10 ppm) and exchange rates (400-2500 s⁻¹).
• Investigation of molecular interactions, such as hydrogen bonding and cation-π networks, influencing CEST contrast.

Main Results:

• Identified molecules exhibiting significant downfield CEST contrast, distinct from water resonance.
• Demonstrated detectable exchangeable proton signals from tyrosine, tryptophan, and lysine under physiological conditions.
• Attributed observed CEST properties to unique hydrogen bonding and cation-π network interactions.

Conclusions:

• Discovered novel protein and peptide candidates for highly specific and sensitive MRI reporter genes.
• These findings pave the way for developing stable reporter proteins for advanced in vivo monitoring.
• The developed biomarkers will significantly advance the tracking of nucleic acid-based therapies like gene and virotherapy.