Structure and Dynamics of Chromatographically Relevant Fe(III)-Chelates

Abstract

Immobilized metal ion affinity chromatography (IMAC) is an important chromatographic technique for biomolecules. In order to get a detailed understanding of the hydration of immobilized Fe(III), complexes of Fe(III) with methyl substituted iminodiacetate ([Fe(MSIDA)(H2O)3](+)) as well as with methyl substituted nitrilotriacetate ([Fe(MSNTA)(H2O)2]) were simulated in aqueous solutions with the quantum mechanical charge field molecular dynamics (QMCF MD) approach. The simulations were carried out at the Hartree-Fock (HF) level of theory, since cluster calculations at the HF, MP2, and B3LYP levels of theory showed that this method results in a good compromise between computational effort and accuracy. None of the coordinating water molecules were exchanged during the simulation period of 15 ps. The Fe-OH2O bond distances as well as the Fe-OH2O stretching motions differed among the coordinating water molecules, indicating different bond strengths. For the water molecules in the second hydration layer, mean residence times of 2.7 and 1.9 ps were obtained for [Fe(MSIDA)(H2O)3](+) and [Fe(MSNTA)(H2O)2], respectively. Furthermore, infrared measurements were carried out to characterize the most prominent bond features of aqueous Fe(III)-NTA and to discuss these results in conjunction with the computationally derived frequencies.

Breakthrough Potential in Near-Infrared Spectroscopy: Spectra Simulation. A Review of Recent Developments

“…Often, while maintaining careful error control, simplifications in the determination of the electronic structure may bring substantial gains in this regard. As recently demonstrated by Messner et al in their investigation of the hydration of immobilized Fe(III), complexes of Fe(III) with methyl substituted iminodiacetate ([Fe(MSIDA)(H 2 O) 3 ]+), as well as with methyl substituted nitrilotriacetate ([Fe-(MSNTA)(H 2 O) 2 ]) in aqueous solutions (Messner et al, 2014) by QMCF-MD, ingenious balancing between the cost-accuracy of the applied electronic method brings notable advantages, e.g., allowing to expand the parameters of molecular dynamics in return. By choosing a relatively fundamental Hartree-Fock (HF) approach, even over a much more robust MP2 method, Messner et al accomplished essential progress in our understanding of the hydration structure and dynamics of metaloorganic complexes.…”

“…At present, this remains a challenge, due to the complex electronic structure of transition metal atoms. Anharmonic simulations of vibrational spectra of such materials are prohibitively expensive; the computational expense associated with solving the vibrational problem in anharmonic approximation of advanced materials requires well-thought simplifications applied at several potential levels, ranging from the vibrational analysis itself (e.g., through reducing the grid density for total energy evaluations; Lutz et al, 2014c) to ingenious approaches to the electronic structure itself (e.g., Messner et al, 2014; Lutz et al, 2015). Vibrational spectra simulations of the metaloorganic complexes involving lighter metal ions can be found in recent literature.…”

A Comparative Study of [CaEDTA]2– and [MgEDTA]2–: Structural and Dynamical Insights from Quantum Mechanical Charge Field Molecular Dynamics

“…In this work an extended QM/MM technique, known as QMCF, [40][41][42][43] is used which has proven to yield excellent results for the investigation of coordination complexes. [45][46][47][48][49] For more information on the methodology the reader is referred to the respective original literature. [40][41][42][43] A crucial step for QM calculations is the assignment of suitable basis sets for the chemical species in the QM region, i.e.…”

“…HF on the other hand lacks of a proper description of electron correlation, but when double-ζ basis sets + polarisation functions are applied excellent results are obtained. [45][46][47][48][49]55 Thus, HF was chosen as compromise between accuracy of results and computational cost. For both MD simulations of [CaEDTA] 2− and [MgEDTA] 2− in aqueous solution a cubic periodic water box containing 2500 explicitly treated water molecules was used.…”

Remarkable conformational flexibility of aqueous 18-crown-6 and its strontium(ii) complex – ab initio molecular dynamics simulations

“…Besides these solute species the cubic boxes (side lengths of 44.9 Å) contained 3000 water molecules. 25,27,41 For the strontium(II) ion the Stuttgart RSC 1997 basis set including a quasi relativistic effective core potential accounting for 28 inner electrons 42 was obtained from the EMSL database. For the integration of the equations of motion the Velocity-Verlet 28,29 algorithm was employed with a time step to 2 fs.…”