Specific Attractive Interactions

The involvement of specific attractive interactions of molecules with the electrode surface (adsorption) makes the electrode process even more complex. The intensity of such interactions ranges from weak (physisorption) to strong (chemical bonds formed between adsorbate and electrode). 

Specific attractive interactions between the dendrimer building blocks (e.g. hydrogen bonds between amino acid building blocks) or complexation of metal ions [86] by suitable functional groups in the dendrimer scaffold can favour the formation of chiral substructures and effect distortion or folding of the overall structure. Interactions with solvent molecules can also have a pronounced effect on the overall structure. 

Cell adhesion results from specific attractive interactions between molecules on the ceU surface and a substrate, which may be coated with more than one kind of molecule. CeU detachment represents the termination of these interactions by physical, chemical, electrical, optical, or other means. 

More effective and specific cell adhesion can be achieved by taking advantage of unique receptors present on the cell surface and the specific attractive interactions that these receptors have with certain biomolecules called ligands. Often, cells of different types have different receptors on their surfaces, and hence, the ligand-receptor bond is like a lock and key connection. One cell type may have receptors that bind to a particular ligand but another cell type may be lacking that kind of receptor. A ligand-coated substrate will therefore bind cells of the former type, but not of the latter type. 

Two principal approaches have been used in the synthesis of polyrotaxanes. In the statistical method, no specific interaction exists between the linear and the cyclic species. The equilibrium for threading is driven by entropic factors. This hence provides a wide choice of pairs of cyclics and linear chains. However, the resulting yield is often low. In the template or directed method, specific attractive interaction (such as metal chelation, charge transfer interactions, etc.) between the cyclic and the linear species is taken advantage of. 

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