Metal ion dependent adhesion sites in integrins: a combined DFT and QMC study on Mn2+.
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.
Sebastian
Eider San
ES
Kimika Fakultatea, Euskal Herriko Unibertsitatea, P.K. 1072, 20080 Donostia, Spain.
Matxain
Jon M
JM
Eriksson
Leif A
LA
Stote
Roland H
RH
Dejaegere
Annick
A
Cossio
Fernando P
FP
Lopez
Xabier
X
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
D016023:Integrins; D008024:Ligands; D008667:Metalloproteins; D008345:Manganese