Study of Calcitriol Interaction with the Vitamin D Receptor Using DFT and TD-DFT Calculations

Area of Science:

• Biochemistry
• Computational Chemistry
• Molecular Biology

Background:

• Calcitriol, the active form of vitamin D, plays a crucial role in various physiological processes.
• Dysregulation of calcitriol levels or vitamin D receptor (VDR) sensitivity can lead to hypercalcemia.
• Developing VDR-ligand analogues with therapeutic benefits and reduced side effects is a key research objective.

Purpose of the Study:

• To elucidate the molecular interactions between calcitriol and the VDR using computational modeling.
• To identify stable VDR-calcitriol conformations and understand their electronic properties.
• To provide a foundation for the rational design of novel VDR-targeting drugs.

Main Methods:

• Hybrid ONIOM2(B3LYP/6-31++G(2d,p):PM7) methodology for structural and energetic characterization.
• Time-Dependent Density Functional Theory (TD-DFT) for electronic property analysis.
• Calculation of binding energy to assess interaction strength.

Main Results:

• Identified stable conformations of the VDR-calcitriol complex.
• Determined that calcitriol is the primary chromophore, with its electronic transitions influenced by TRP286 and TYR295 residues.
• Calculated binding energy (-11.88 kcal/mol) aligns with experimental data, validating the computational model.

Conclusions:

• The study offers novel mechanistic insights into VDR-calcitriol recognition at the residue level.
• Computational findings support the reliability of the predicted binding mode.
• This research can guide the development of improved therapeutic analogues targeting the VDR.