TY - JOUR
T1 - Molecular dynamics simulation of [Gd(egta)(H2O)]- in aqueous solution
T2 - Internal motions of the poly(amino carboxylate) and water ligands, and rotational correlation times
AU - Yerly, Fabrice
AU - Hardcastle, Kenneth I.
AU - Helm, Lothar
AU - Aime, Silvio
AU - Botta, Mauro
AU - Merbach, André E.
PY - 2002/3/1
Y1 - 2002/3/1
N2 - Molecular dynamics simulations of [Gd(egta)(H2O)]- (egta4-= 3,12-bis(carboxymethyl)-6,9-dioxa-3,12-diazatetradecanedioate(4-)) have been performed without any artificial constraint on the first coordination sphere, such as covalent bonds between the Gd3+ and the coordination sites. Two new crystallographic structures were determined for this gadolinium chelate and used to start two molecular dynamics simulations. [Gd(egta)(H2O)]- and [Gd(egta)]- were both observed during the simulations, with a mean volume for the reaction of dissociation [Gd(egta)(H2O)]- → [Gd(egta)]- + H2O of +7.2cm3 mol-1, which corroborates the previously published experimental value of +10.5 cm3 mol-1. Changes in the conformation of the complex with the inversion of several dihedral angles are observed in the simulations independently from the water dissociation. Very fast changes of the third-order rotation axis direction of the Gd3+ coordination polyhedron (of symmetry D3h) are observed during the simulations and are related to the mechanism of electronic relaxation of the complex. Different rotational correlation times (τR) were calculated from the simulations on various observables of the complex. Protons of the inner sphere have different τR. The mean τR of the two Gd-HW (HW = hydrogen of water molecule) vectors is 72% lower than τR of the complex, and 75% lower than τR of the vector Gd-OW (OW = oxygen of water molecule). This discrimination of the tumbling rates should be taken into account in future global 17O NMR, EPR and NMRD (nuclear magnetic relaxation dispersion) data analysis.
AB - Molecular dynamics simulations of [Gd(egta)(H2O)]- (egta4-= 3,12-bis(carboxymethyl)-6,9-dioxa-3,12-diazatetradecanedioate(4-)) have been performed without any artificial constraint on the first coordination sphere, such as covalent bonds between the Gd3+ and the coordination sites. Two new crystallographic structures were determined for this gadolinium chelate and used to start two molecular dynamics simulations. [Gd(egta)(H2O)]- and [Gd(egta)]- were both observed during the simulations, with a mean volume for the reaction of dissociation [Gd(egta)(H2O)]- → [Gd(egta)]- + H2O of +7.2cm3 mol-1, which corroborates the previously published experimental value of +10.5 cm3 mol-1. Changes in the conformation of the complex with the inversion of several dihedral angles are observed in the simulations independently from the water dissociation. Very fast changes of the third-order rotation axis direction of the Gd3+ coordination polyhedron (of symmetry D3h) are observed during the simulations and are related to the mechanism of electronic relaxation of the complex. Different rotational correlation times (τR) were calculated from the simulations on various observables of the complex. Protons of the inner sphere have different τR. The mean τR of the two Gd-HW (HW = hydrogen of water molecule) vectors is 72% lower than τR of the complex, and 75% lower than τR of the vector Gd-OW (OW = oxygen of water molecule). This discrimination of the tumbling rates should be taken into account in future global 17O NMR, EPR and NMRD (nuclear magnetic relaxation dispersion) data analysis.
KW - Conformation analysis
KW - Gadolinium
KW - Imaging agents
KW - Magnetic resonance imaging
KW - Molecular dynamics
KW - Solvation
UR - http://www.scopus.com/inward/record.url?scp=0036501596&partnerID=8YFLogxK
U2 - 10.1002/1521-3765(20020301)8:5<1031::AID-CHEM1031>3.0.CO;2-9
DO - 10.1002/1521-3765(20020301)8:5<1031::AID-CHEM1031>3.0.CO;2-9
M3 - Article
SN - 0947-6539
VL - 8
SP - 1031
EP - 1039
JO - Chemistry - A European Journal
JF - Chemistry - A European Journal
IS - 5
ER -