Molecular dynamics study of the hydration of lanthanum(III) and europium(III) including many-body effects

Lanthanides complexes are widely used as contrast agents in magnetic resonance imaging (MRI) and are involved in many fields such as organic synthesis, catalysis, and nuclear waste management. The complexation of the ion by the solvent or an organic ligand and the resulting properties (for example the relaxivity in MRI) are mainly governed by the structure and dynamics of the coordination shells. All of the MD approachs already carried out for the lanthanide(III) hydration failed due to the lack of accurate representation of many-body effects. We present the first molecular dynamics simulation including these effects that accounts for the experimental results from a structural and dynamic (water exchange rate) point of view

Gd(III) polyaminocarboxylate chelate: realistic manybody molecular dynamics simulations for molecular imaging applications

Realistic molecular dynamics simulations of polyaminocarboxylate complexes of gadolinium (III) ion in water are performed, providing coordination numbers and average residence times in quantitative agreement with available experimental data. A theoretical analysis, based on fitting a fluctuating charges model on ab initio data, also indicates that charge transfer between the ion and the ligand is significant

A predicted organometallic series following a 32-electron principle: An@C28 (An = Th, Pa+, U2+, Pu4+).

International audienceThe spectroscopic and thermodynamic properties of the molecules M@C28 (M = Ce, Th, Pa+, U2+, Pu4+) are calculated using density functional theory. The systems have considerable energetic stability. It is shown that the actinide cases can be classified as "32-electron" systems, using the bonding s-, p-, d-, and f-type orbitals of the central metal. The rest of the valence molecular orbitals have purely carbon character

Towards energy decomposition analysis for open and closed shell f-elements mono aqua complexes

International audienceWe propose an energy decomposition analysis of mono aqua systems of both open and closed shell lanthanide and actinide cations using the CSOV scheme. We compared the values obtained with either large f-in-core or small core quasi relativistic pseudopotentials and computed the unpaired electrons contribution to the polarization energy component. Through a quasi-systematic approach on a number of chosen f-element cations, we quantified the different trends across both series for each contribution. This work is an important preliminary step for the acquisition of reference ab initio data for further parameterization of polarizable force fields for lanthanides and actinides. (Cop) 2013 Elsevier B. V. All rights reserved

Gas-phase models of gamma-turns: Effect of side-chain/backbone interactions investigated by IR/UV spectroscopy and quantum chemistry

The conformations of laser-desorbed jet-cooled short peptide chains Ac–Phe–Xxx–NH2 (Xxx=Gly, Ala, Val, and Pro) have been investigated by IR/UV double resonance spectroscopy and density-functional-theory (DFT) quantum chemistry calculations. Singly -folded backbone conformations (L-) are systematically observed as the most stable conformers, showing that in these two-residue peptide chains, the local conformational preference of each residue is retained (L for Phe and turn for Xxx). Besides, turns are also spontaneously formed but appear as minor conformers. The theoretical analysis suggests negligible inter-residue interactions of the main conformers, which enables us to consider these species as good models of turns. In the case of valine, two similar types of turns, differing by the strength of their hydrogen bond, have been found both experimentally and theoretically. This observation provides evidence for a strong flexibility of the peptide chain, whose minimum-energy structures are controlled by side-chain/backbone interactions. The qualitative conformational difference between the present species and the reversed sequence Ac–Xxx–Phe–NH2 is also discussed