Architecture, helical supramolecular

Peptides composed of various coded and noncoded amino acid residues self-assemble to form various types of supramolecular architectures, including supramolecular helices and sheets, nanotubes, nanorods, nanovesicles, and nanofibers. The higher-order self-assembly of supramolecular (3-sheets or supramolecular helices composed of short synthetic acyclic peptides leads to the formation of amyloid-like fibrils. Synthetic cyclic peptides were used in supramolecular chemistry as molecular scaffolding for artificial receptors, so as to host various chiral and achiral ions and other small neutral substrates. Cyclic peptides also self-assemble like their acyclic counterparts to form supramolecular structures, including hollow nanotubes. Self-assembling cyclic peptides can be served as artificial ion channels, and some of them exhibit potential antimicrobial activities against drug-resistant bacteria. 

Cholesteric LCs (CLCs) are of particular interest due to their unique ability to self-organize into a helical supramolecular architecture. CLC structures are also found in nature including living matter. They have been used in temperature sensors, optical filters, reflective devices, cosmetics, etc. A CLC reflects light owing to its helical... 

Compound 72 was shown to display enantioselectivity in the extraction of chiral potassium salts from water into the organic phase.105 The supramolec-ular polymer possesses a homochiral helical architecture onto which one of the anionic enantiomers preferentially binds. Intriguingly, for some of the anions the octamer and polymer showed opposite selectivity, illustrating the difference in supramolecular chirality of the two systems. Furthermore, the polymer was capable of inducing a Cotton effect in the achiral compound potassium A-(2,4-dinitrophenyl)glycinate. Since the apolar side chains would... 

FIGURE 5.11 Supramolecular, helical architecture and definition of pitch length p of chiral nematic liquid crystals. 

The design and synthesis of supramolecular architectures with parallel control over shape and dimensions is a challenging task in current organic chemistry [13, 14], The information stored at a molecular level plays a key role in the process of self-assembly. Recent examples of nanoscopic supramolecular complexes from outside the dendrimer held include hydrogen-bonded rosettes [15,16], polymers [17], sandwiches [18, 19] and other complexes [20-22], helicates [23], grids [24], mushrooms [25], capsules [26] and spheres [27]. 

Metal-directed Self-assembly of Complex Supramolecular Architecture Chains, Racks, Ladders, Grids, Macrocycles, Cages, Nanotubes and Self-intertwining Strands (Helicates)... 

Fritz Vogtle is Professor and Director at the Kekule-Institute for Organic Chemistry and Biochemistry at the University of Bonn, Germany. His research interests are supramolecular chemistry deformed helical molecules and their chiroptical properties and compounds with appealing architectures such as rotaxanes, catenanes, knots, and dendrimers [37-40],... 

Supramolecular architectures are highly sensitive to chiral perturbations in general, and in systems that form liquid crystals in particular. Small amounts of enantiopure guest molecule added to a nematic host can induce a transition to a cholesteric phase, and the helical organization in the mesoscopic system is very sensitive to the structure of the guest molecule. Chiral amplification was successfully achieved in such liquid crystals, using CPL as the chiral trigger for the phase transition [183]. 

---