Solution Structures Deduced from LIS Data

2 Solution structures deduced from LIS data. - Andre et a/. have prepared new ditopic trihelicate lanthanide (La-La -L3) complexes, which they consider of potential utility as biomedical probes. The solution structures of these species were determined by analyses of lanthanide-induced chemical shifts and proton spin relaxation data of mixed complexes containing one diamagnetic Lu + ion and one paramagnetic lanthanide ion. 

Valencia et have used proton pseudocontact chemical shift data in conjuction with x-ray crystal structures to determine the solution geometries of the lanthanide complexes with the ligand Py2N6Ac4, which contains four acetate pendant arms. The aqueous solution structures of diamagneticLa and Lu complexes were characterized by their COSY NMR spectra. The structures of the paramagnetic complexes were determined by fits of H pseudocontact chemical shift data and spin relaxation data to a model that assumed rhombic magnetic susceptibility tensors. 

Lisowsky et a/. have studied proton pseudocontact chemical shifts in a series of chiral macrocyclic Yb(III) complexes which differ in the axial ligands. They 

D Amelio et have determined the solution structure of the Ca -angiotensin complex, using Ce(III) as a paramagnetic surrogate for Ca . Distance and angle constraints used in a simulated annealing MD analysis of the complex were provided by ROESY cross-peaks and J(HN-Ha) coupling constants. Pseudocontact chemical shift measurements were used to determine the dissociation constant and the stoichiometry of the complex. 

1 Determination of Absolute Configuration and Solution Conformation. Abraham et have employed H and C lanthanide induced shifts produced by Yb(fod)3 as an experimental probe of the solution conformations of cyclopen-tanol and cis- and trans-cyclopentane-l,2-diol. Analysis of the LIS was undertaken in conjunction with molecular mechanics and ab initio calculations of structure. 

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