Peripheral structural motifs

Peripheral structural motifs are a second principal category of retrosynthetic fragments. The presence of such fragments usually does not substantially influence... 

Nevertheless, the structural peripheral fragments shown in Figure 12.5 have similar size, molecular topology, lipophilicity, number of H-bond accepting groups and number of rotatable bonds. It can be concluded that peripheral structural motifs, being structurally different molecular fragments, can exhibit similar physicochemical and spatial properties. 

The amphipathic helix, in which residues are spaced so that the helical periodicity places hydrophobic side chains on one side of the helix and hydrophilic side chains on the other, is a common structural motif used by the peripheral apolipoproteins to bind lipid (Segrest et al., 1992) it is also a structural element present in globular proteins (Perutz et al., 1965). 

How are proteins associated with the bilayer in membranes The proteins that occur in membranes can be peripheral proteins, which are found on the surface of the membrane, or integral proteins, which lie within the lipid bilayer. Various structural motifs, such as bundles of seven a-helices, occur in proteins that span membranes. 

Fig. 12.5 Dopamine D2 agonists having a distinct N-arylpiperazine privileged motif and structurally different peripheral fragments.

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