Ligand orientations

A.R. Raitsimring and F.A. Walker, Porphyrin and ligand protons as internal labels for determination of ligand orientations in ESEEMS of low-spin d5 complexes in glassy media ESEEM studies of the orientation of the g tensor with respect to the planes of axial ligands and porphyrin nitrogens of low-spin ferriheme systems, J. Am. Chem. Soc., 1998, 120, 991. 

Fig. 8 Highly active catalysts discovered on the basis of the ligand oriented catalyst design concept ...

The first approach has successfully been applied to the study of amorphous as well as to macroscopically ordered solids. Examples of applications include the determination of backbone geometries in fibrous proteins [4] or the determination of protein-backbone, side-chain, and bound-ligand orientation with respect to the membrane normal in membrane-bound proteins [5-8]. Membranes, bilayers, bicelles, or liposomes are neither solid nor liquid systems but have aspects of both and are sometimes liquid crystalline. In most of these systems, time-independent anisotropic interactions play an important role,... 

Fig. 14.8 Experimental ligand interactions with cytochrome P450 2C family. (A) X-ray structure ofthe sulfaphenazole derivate DMZ in rabbit CYP2C5 at 2.3 A resolution (PDB 1 N5B) from Wester et al. [191]. Only one ofthe two-ligand orientations for DMZ in accord with electron density is shown placing the benzylic methyl group in a 4.4 A distance to the heme iron. (B) X-ray structure of S-warfarin in human CYP2C9 at 2.55 A resolution (PDB 10G5) from Williams et al. [192]. The substrate is situated in a predominantly hydrophobic pocket. This binding mode places the 6- and 7-hydroxylation sites 10 A from the iron (arrow).

There has been considerable discussion on the validity of docking and scoring functions in structure-based design because of the complex issues involved such as ligand orientation, water participation, or flexibility of the target protein itself [186-190]. 

LIGAND ORIENTATION Phi The Psi (degrees) OF X LIGAND Y Z (A) CONFOR- HYDROGEN BONDING NATIONAL ENERGY SCHEME (kcal/mol) ... 

These subtle changes in ligand orientation may nevertheless lead to significant lowering of the energy. For [Fe(0H2)6]2+, the... 

Condensation of an acrylic acid-cellulose graft copolymer with 5-amino-l,10-phe-nanthroline (233) has been utilized to provide polymer (234 Scheme 113) with the phenanthroline ligand oriented optimally for complexation (77MI11110). The polymer was described as exhibiting a strong sorption capacity for Co2+ and Cu2+ ions. 

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