Design Considerations

When designing a foldamer sequence to adopt a specific conformation at the interface, ''positive'' and ''negative'' design approaches, leading to rational stabilization and destabilization of local geometries by introduction of attractive and repulsive interactions, have to be combined in order to realize the ''minimally frustrated'' state [5]. One first important aspect concerns the use of hetero-sequences to bias conformational preferences in foldamers. For example, from

Fig. 13.4 Pathway selection in pattern recognition offoldamers on surfaces. The Muthukumar Model (adapted from ref. [4]) assumes that the foldamer displays three groups, spaced m units apart, which recognize the surface functionalities X, spaced by distance b. In the case of recognition, the enthalpy of interaction is e while the loop entropy is fs = 3kBTb2/2m. While the intermediate topological state (c) i: more stable than (b), it does not lead to the global minimum topological state (d) as shown on the right.

Fig. 13.4 Pathway selection in pattern recognition offoldamers on surfaces. The Muthukumar Model (adapted from ref. [4]) assumes that the foldamer displays three groups, spaced m units apart, which recognize the surface functionalities X, spaced by distance b. In the case of recognition, the enthalpy of interaction is e while the loop entropy is fs = 3kBTb2/2m. While the intermediate topological state (c) i: more stable than (b), it does not lead to the global minimum topological state (d) as shown on the right.

Fig. 13.3 it becomes apparent that in order to favor the helical conformation at the interface, heterosequences are required. A second important strategy avoids complications or local defects due to chain entropy by reducing the number of entropically favored loops. Furthermore, the strength of the interactions, both within and between strands and most importantly between foldamer and surface has to be balanced to assure for defect healing yet conformational stability.

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