Department of Chemistry, University of Manitoba, Winnipeg, Manitoba, Canada.
Inorg Chem. 2011 Apr 4;50(7):3141-52. doi: 10.1021/ic2001706. Epub 2011 Mar 10.
The structural properties and electronic structures of pentacoordinated uranyl complexes belonging to the UO(2)F(n)(H(2)O)(5-n) series have been studied in the gas and aqueous phases using density functionals with relativistic pseudopotentials and all-electron basis sets in the gas-phase calculations in combination with COSMO in the aqueous phase. In addition, the conformational orientation and structural and electronic properties of UO(2)F(5) in the hydrophobic cavities of the right-handed coiled-coil (RHCC) protein of tetrabrachion have been determined using the hybrid QM/MM method. Although there is good agreement between the available experimental geometrical parameters and the values obtained in the aqueous phase using pseudopotentials or all-electron basis sets, variation of the uranyl U═O bond with the number of fluoride ligands is only truly captured after the inclusion of five water molecules in the second coordination sphere around the molecules. The docking procedure used in this work shows that there are only two possible orientations of the uranyl group of UO(2)F(5) embedded in the hydrophobic cavities of the RHCC protein. The two orientations are exclusively along the axes perpendicular to the protein axial channel with no possible orientation of the uranyl group along the axial channel because of both steric effects and interaction with the alkyl chain of the isoleucine residues pointing into the axial channel. In addition, the embedded complex is always positioned nearer to the isoleucine residues at the N-terminal ends of the hydrophobic cavities. Energy analysis, however, reveals that both conformations can only be observed in cavity 2, the largest hydrophobic cavity. The structural and electronic properties of the ligand embedded in this cavity are very similar to those of the gas-phase structure. A comparable study of Pt(CN)(6) and the anticancer drug cisplatin, [PtCl(2)(NH(3))(2)], in cavity 2, revealed the existence of just two orientations for the former, similar to the uranyl complex, and multiple orientations for the latter.
五配位铀酰配合物的结构性质和电子结构属于UO(2)F(n)(H(2)O)(5-n)系列，已在气相和水相使用相对论赝势和全电子基组的密度泛函进行研究，在气相计算中结合 COMSO 在水相。此外，还使用混合 QM/MM 方法确定了右手卷曲螺旋（RHCC）蛋白疏水腔中UO(2)F(5)的构象取向、结构和电子性质。尽管可用的实验几何参数与使用赝势或全电子基组在水相获得的值之间存在良好的一致性，但只有在第二配体分子周围的配位球中包含五个水分子后，铀酰 U═O 键随氟化物配体数量的变化才真正被捕获。本工作中使用的对接程序表明，嵌入 RHCC 蛋白疏水腔中的UO(2)F(5)的铀酰基团只有两种可能的取向。这两种取向都完全沿着与蛋白质轴向通道垂直的轴，由于空间位阻效应和与轴向通道内的异亮氨酸残基的烷基链的相互作用，铀酰基团不可能沿着轴向通道取向。此外，嵌入的配合物总是更靠近疏水腔的 N 末端的异亮氨酸残基。然而，能量分析表明，只有两种构象可以在腔 2 中观察到，腔 2 是最大的疏水腔。嵌入该腔的配体的结构和电子性质与气相结构非常相似。对腔 2 中的Pt(CN)(6)和抗癌药物顺铂[PtCl(2)(NH(3))(2)]进行了类似的研究，结果表明前者存在类似于铀酰配合物的两种取向，而后者存在多种取向。
