Modeling zinc in biomolecules with the self consistent charge-density functional tight binding (SCC-DFTB) method:...

Area of Science:

• Computational chemistry
• Quantum chemistry
• Biochemistry

Background:

• Zinc ions play crucial roles in numerous biological processes.
• Accurate computational modeling of zinc-containing systems is essential for understanding enzyme mechanisms.
• Existing methods may be computationally expensive for large systems.

Purpose of the Study:

• To develop and validate parameters for zinc ions within the self-consistent charge density functional tight-binding (SCC-DFTB) framework.
• To assess the accuracy of the developed SCC-DFTB parameters against higher-level theoretical methods.
• To evaluate the applicability of SCC-DFTB for modeling zinc active sites in enzymes.

Main Methods:

• Development of zinc ion parameters for the SCC-DFTB method.
• Validation against B3LYP and MP2 calculations using various basis sets.
• Testing on small molecules with biological zinc coordination environments (cysteine, histidine, etc.).
• Application to active site models of enzymes like alcohol dehydrogenase and carbonic anhydrase.

Main Results:

• The SCC-DFTB approach with new zinc parameters reliably reproduces structural properties.
• Energetic properties, including ligand binding and deprotonation energies, are accurately predicted.
• Barriers for zinc-assisted proton transfers are well-reproduced compared to B3LYP and MP2.
• The method shows good performance for enzyme active site models.

Conclusions:

• The developed SCC-DFTB parameters provide a computationally efficient and accurate method for studying zinc ions in biological systems.
• This approach facilitates the investigation of zinc-dependent enzymes and their mechanisms.
• SCC-DFTB offers a viable alternative to more computationally intensive methods for zinc-related research.