Self-assembly with modification

In this case, the restriction of peptide self-assembly was both desired, and by design. More generally, when looking to modify peptides and retain their self-assembly, where modifications are incompatible with assembly, post-assembly strategies will be necessary. 

Self-assembly can be divided into a number of classes 1. strict self-assembly, 2. irreversible self-assembly, 3. precursor modification followed by self-assembly, 4. self-assembly with post-modification, 5. assisted self-assembly, 6. directed self-assembly, 7. self-assembly with intermittent processing. 

Gibb, B. C., Strict self-assembly and self-assembly with covalent modification , in Encyclopedia of Supramolecular Chemistry, Atwood, J. L.. Steed, J. W., eds. Marcel Dekker New York, 2004. Vol. 2, pp. 1372-1378. 

Several types of self-assembly have been identified from the biological literature 7 (i) thermodynamic self-assembly (ii) irreversible self-assembly (iii) assisted and directed self-assembly and (iv) self-assembly with pre-, post-, or intermittent modification. 

Self-assembly processes involving covalent modifications typically comprise one of the earlier classes of self-assembly followed by, preceded by, or intermixed with conventional covalent bond formation. In coordination chemistry, for example, self-assembly with precursor modification means synthesizing the component ligands and metal complexes before carrying out the reaction. Post-modification involves locking a self-assembled structure into a kinetically stable state. Self-assembly with intermittent processing involves combinations of both of these. 

Catenanes and Other Interlocked Molecules, p. 206 DNA Nanotechnology, p. 475 Nomenclature in Crystal Engineering, p. 967 Plutonic and Archimedean Solids, p. 1100 Self-Assembling Catenanes. p. 1240 Strict Self-Assembly and Self-Assembly with Covalent Modifications, p. 1372 Supramolecular Isomerism, p. 1420 The Template Effect, p. 1493... 

Strict Self-Assembly and Self-Assembly with Covalent Modification, p. 1372 Supramolecular Polymers, p. 1443... 

Hemoglobins O2 Uptake and Transport, p. 636 Molecular Logic Gates, p. 893 Molecular-Level Machines, p. 931 Phthalocyanines, p. 1069 71—71 Stacking Theory and Scope, p. 1076 Potphyrin-Based Clathrates, p. 1150 Self-Assembly Definition and Kinetic and Thermodynamic Considerations, p. 1248 Self-Assembly Terminology, p. 1263 Strict Self-Assembly and Self-Assembly with Covalent Modifications, p. 1372 Supramolecular Photochemistry, p. 1434 Vitamin 8/2 and Heme Models, p. 1569... 

Two self-assembly techniques are predominantly employed in the preparation of catenanes "thermodynamic" self-assembly and self-assembly with covalent "modification."... 

In self-assembly with covalent modification, conventional organic reactions are typically performed on self-assembled structures in order to lock them into a kinetically stable state." ] For the preparation of catenanes, the self-assembly step is generally used to generate a precursor molecule with a disposition that allows for ready conversion to a kinetically stable catenane structure. The self-assembly step is most often employed to bring about interlocking, giving rotaxane or pseudorotaxane intermediates. These are subsequently converted to catenanes by simple cyclization reactions. 

One addition to the assembly lexicon added a layer of complexity to the above definition. Thus, one of the seven different classes of self-assembly originally proposed by Lindsey. — which are strict self-assembly processes (with or without a template) positioned in different chemical settings—is commonly known as "irreversible self-assembly." This term is used to describe two-step processes, whereby a strict self-assembly processes is followed by irreversible reactions that covalently knit together the array of subunits. As Whitesides noted, strictly speaking this term is a misnomer. Hence, along with other types of post-assembly modified self-assemblies, we categorize these processes as "self-assembly with covalent modification." Postmodification generally comes in the form of a series of covalent bond formation steps and is of less interest to us here. The crux of any self-assembly process is the self-assembly. 

Strict Self-Assembly and Self-Assembly with Covalent Modifications... 

Mirkin et al. recently worked on a slightly different metal-ion-directed self-assembly in which thermodynamically controlled covalent modification is applied to the product. In this approach, the assembly part of this, self-assembly with covalent modification," involves chelate donors and is perhaps best described with the Raymond analysis. However, in contrast, the postmodi-fied products are probably best described using the method proposed by Stang. This double-barreled approach is not ideal and indicates that there is still a large amount of work to be done before a more uniformly applicable description of self-assembly is reached. 

Strict Self-Assembly and Self Assembly with Covalent Modifications, p. 1372 Strong Hydrogen Bonds, p. 1379 Supramolecular Polymers, p. 1443 Suifactants. Part I Fundamentals, p. 1458 Surfactants, Part II Applications, p. 1470 van der Waals Forces, p. 1550... 

Self-assembly with post-modification. The most common form of modification that is utilised in synthetic systems is the alteration of a system after the self-assembly step has taken place. Many common systems, such as rotaxanes and catenanes (Section 3.4), are formed from a self-assembled structure, held loosely together by non-covalent interactions, which are locked in place once the self-assembly process is complete by the formation of covalent bonds, much like tying off the ends of a knot. 

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