title: Metal ion dependent adhesion sites in integrins: a combined DFT and QMC study on Mn2+.
abstract: The theoretical study of relative energies of different spin states of Mn2+ has been carried out for the isolated cation and for structures in which the cation is coordinated to ligands that represent the first coordination shell in a protein environment that contains a metal ion dependent adhesion site (MIDAS, found in the ligand binding domain of protein LFA-1). The calculations determine whether the ligand field generated by a prototype protein environment affects the relative energies between high, intermediate, and low spin states. Geometry optimizations and vibrational frequency calculations were carried out at the B3LYP/SKBJ+* level of theory. Single point calculations were performed at the B3LYP/6-311++G(2df,2p) and diffusion monte carlo (DMC) levels for the refinement of the electronic energies. These calculations reveal important differences in the relative energies between high/low spin complexes obtained by B3LYP and DMC and show that although both DFT and DMC show similar trends, a higher level method such as DMC is necessary for a quantitative description of the interactions between Mn2+ and its natural ligands. (G)s of acetate-type ligand binding reactions were calculated that show that the higher the spin of the manganese complex, the lower the affinity for the ligand.
authors.affiliation: Kimika Fakultatea, Euskal Herriko Unibertsitatea, P.K. 1072, 20080 Donostia, Spain.
authors.forename: Eider San
authors.initials: ES
authors.lastname: Sebastian
authors.forename: Jon M
authors.initials: JM
authors.lastname: Matxain
authors.forename: Leif A
authors.initials: LA
authors.lastname: Eriksson
authors.forename: Roland H
authors.initials: RH
authors.lastname: Stote
authors.forename: Annick
authors.initials: A
authors.lastname: Dejaegere
authors.forename: Fernando P
authors.initials: FP
authors.lastname: Cossio
authors.forename: Xabier
authors.initials: X
authors.lastname: Lopez
mesh_terms: D000465:Algorithms; D001665:Binding Sites; D016023:Integrins / Q000737:chemistry*; D008024:Ligands; D008345:Manganese / Q000737:chemistry*; D008667:Metalloproteins / Q000737:chemistry*; D011485:Protein Binding; D011789:Quantum Theory; D013816:Thermodynamics
chemical_list: D016023:Integrins; D008024:Ligands; D008667:Metalloproteins; D008345:Manganese