Configuration metal binding

The dependence of chiral recognition on the formation of the diastereomeric complex imposes constraints on the proximity of the metal binding sites, usually either an hydroxy or an amine a to a carboxyHc acid, in the analyte. Principal advantages of this technique include the abiHty to assign configuration in the absence of standards, enantioresolve non aromatic analytes, use aqueous mobile phases, acquire a stationary phase with the opposite enantioselectivity, and predict the likelihood of successful chiral resolution for a given analyte based on a weU-understood chiral recognition mechanism. 

Fig. 4. Calculated density of states for two zigzag individual SWCNTs with (a) semiconducting (10, 0) and (b) metallic (9, 0) configurations. Tight-binding approximation was used for the calculation [6].

In the thermodynamically favored species, therefore, both ligand strands must bind with their N -termini to the A-configured metal center of the meso-type dinu-clear complex to adopt the sterically more favored right-handed helical conformation. Thus, under thermodynamically controlled conditions the dominating species in solution is isomer I (Figure 1.3.8). The results and considerations discussed show that stereochemical communication between a metal center and an amino acid residue can control the microstructure at the amino acid. In the example presented this leads, in a thermodynamically controlled system, after initial formation of a complex mixture, to only one final dominating species [20, 21]. 

Fig. 1.3.8. Schematic presentation of the thermodynamically favored isomer I with the N-terminal catecholates of both ligands binding to a A-configured metal and the C-termini binding to a A-configured metal.

Fig. 6. AS, the difference between free atom and metallic binding energies of 2s or 2p core levels in the elements Ti through Zn. Estimates by Ley et al. [Ref. (79)], shown as filled circles, are based on dnsm configurations which were taken to differ between atom and metal for all elements except Cr and Zn. The open circles are values based on free atom binding energies for atom configurations d s most closely corresponding to the metallic d electron counts. (See text.)...

Nielson KB, Atkin CL and Winge DR (1985) Distinct metal-binding configurations in metallo-thionein. J Biol Chem 260 5342-5350. 

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