Important Features of a Ligand

A ligand should ideally recognise only the target protein. Examples of affinity ligands are shown in Table 9-2. However, many group-specific adsorbents are commercially available and it may be unnecessary to invest in a specific adsorbent. The size of the ligand is important for if is too small the target protein may have insuffi- 

Factors affecting retention are the equilibrium dissociation constant (K for the ligand-protein complex and the number of available binding sites on the ligand. The value of may be defined by 

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Examination of structurally characterized dithiolene complexes identifies a number of important features of dithiolene ligand systems. The ligands largely maintain their shape, bond distances, and angles over a wide range of metal-based complexes. Even additional bridging bonds found in bis(dithiolene) dimers and multimeric mono(dithiolene) structures do not greatly alter the metal-dithiolene chelate. 

The enzyme-catalyzed interconversion of acetaldehyde and ethanol serves to illustrate a second important feature of prochiral relationships, that ofprochiral faces. Addition of a fourth ligand, different from the three already present, to the carbonyl carbon of acetaldehyde will produce a chiral molecule. The original molecule presents to the approaching reagent two faces which bear a mirror-image relationship to one another and are therefore enantiotopic. The two faces may be classified as re (from rectus) or si (from sinister), according to the sequence rule. If the substituents viewed from a particular face appear clockwise in order of decreasing priority, then that face is re if coimter-clockwise, then si. The re and si faces of acetaldehyde are shown below. 

Silver(I) coordination chemistry produces a stream of unusual structures, and a great number of complexes with all type of donor ligands have been prepared. An important feature of the... 

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