Butterfly Effect in Cytarabine: Combined NMR-NQR Experiment, Solid-State Computational Modeling, Quantitative...

Area of Science:

• Biochemistry
• Computational Chemistry
• Molecular Biology

Background:

• Cytarabine (Ara-C), a synthetic cytidine isomer, exhibits potent anti-cancer properties.
• A minor inversion of the 2'-hydroxyl group in Ara-C's sugar moiety drastically alters its biological activity.
• Understanding the molecular basis of this activity is crucial for developing novel therapeutics.

Purpose of the Study:

• To elucidate the molecular mechanisms behind Cytarabine's anti-cancer activity.
• To investigate the structural and electronic differences between Cytarabine and cytidine.
• To identify key molecular interactions driving Ara-C's efficacy.

Main Methods:

• Nuclear Quadrupole Resonance (NQR) spectroscopy and ¹H-¹⁴N NMR techniques.
• Solid-state computational modeling including Quantum Theory of Atoms in Molecules (QTAIM) and Hirshfeld surface analysis.
• Molecular docking simulations with deoxycytidine kinase (dCK) and quantitative structure-property relationship (QSPR) analysis.

Main Results:

• A unique intramolecular OH···O hydrogen bond was identified as critical for Ara-C's conformation and binding.
• This hydrogen bond strengthens interactions with amino acid residues (Gln97, Asp133, Ara128) and Phe137.
• NQR spectral analysis revealed three inequivalent nitrogen sites, providing insights into electronic distribution.

Conclusions:

• The 'butterfly effect' of Ara-C's anti-cancer activity is attributed to the 2'-hydroxyl inversion and the intramolecular hydrogen bond.
• These findings highlight distinct binding modes compared to cytidine, offering a basis for designing improved anti-cancer and anti-viral agents.