Structure and dynamics of chromatographically relevant Fe(III)-chelates

Area of Science:

• Computational Chemistry
• Biophysical Chemistry
• Chromatography

Background:

• Immobilized metal ion affinity chromatography (IMAC) is vital for biomolecule separation.
• Understanding the hydration of immobilized metal ions, like Fe(III), is key to optimizing IMAC techniques.
• Previous studies have lacked detailed insights into the dynamic hydration shell of Fe(III) in IMAC contexts.

Purpose of the Study:

• To investigate the hydration structure and dynamics of Fe(III) complexes relevant to IMAC.
• To simulate aqueous solutions of Fe(III) with methyl substituted iminodiacetate ([Fe(MSIDA)(H2O)3](+)) and methyl substituted nitrilotriacetate ([Fe(MSNTA)(H2O)2]).
• To compare computational findings with experimental infrared spectroscopy data.

Main Methods:

• Quantum mechanical charge field molecular dynamics (QMCF MD) simulations at the Hartree-Fock (HF) level of theory.
• Cluster calculations using HF, MP2, and B3LYP methods to determine the optimal level of theory.
• 15 ps simulation period to observe water molecule exchange and dynamics.
• Infrared spectroscopy for experimental characterization of Fe(III)-NTA complexes.

Main Results:

• No exchange of coordinating water molecules was observed during the 15 ps simulation.
• Differences in Fe-OH2O bond distances and stretching motions indicated varying bond strengths for coordinated water.
• Mean residence times for second hydration layer water molecules were 2.7 ps for [Fe(MSIDA)(H2O)3](+) and 1.9 ps for [Fe(MSNTA)(H2O)2].

Conclusions:

• The study provides a detailed molecular-level understanding of Fe(III) hydration in IMAC-relevant complexes.
• Computational and experimental data offer insights into the stability and dynamics of the hydration shell.
• Findings contribute to the rational design and optimization of IMAC processes for biomolecule purification.