Supramolecular activity

D. G. and Pikramenou Z. (1997) Chemosensing of Monocyclic and Bicyclic Aromatic Hydrocarbons by Supramolecular Active Sites, in Desvergne J.-P. and Czarnik A. W. (Eds), Chemosensors of Ion and Molecule Recognition, NATO ASI series, Kluwer Academic Publishers, Dordrecht, pp. 159-76. 

Determination of the dependence of the fractional activity on the concentration of the monomer forming the uni- or supramolecular active structure is required to obtain the fc Cso (Section 11.2.2). The shape of the Cm profile contains further information on the thermodynamics and, in some cases, the stoichiometry of the self-assembly of supramolecular ion channels and pores (Fig. 11.7) [21]. 

Parallel and antiparallel self-assembly can be differentiated by voltage dependence Parallel self-assembly of asymmetric monomers gives voltage-sensitive, antiparallel self-assembly voltage-insensitive synthetic ion channels and pores [9]. Other indirect evidence from function such as inner diameters from Hill analysis of single-channel conductance (Section 11.3.3) or other size exclusion experiments is often used to support indications for supramolecular active structures molecular modeling can be of help as well [3, 4, 10]. 

Monks CR, Freiberg BA, Kupfer H, Sciaky N, Kupfer A Three-dimensional segregation of supramolecular activation clusters inT cells. Nature 1998 395 82-85. 

Figure 11 Hill plots are dose-response curves that describe the dependence of activity on monomer concentration. Hill analysis can differentiate between (a) unstable supramolecular active structures (n > 1 known stoichiometry, undetectable suprastructure) and (b) stable supramolecular or unimolecular active structures (n < 1 unknown stoichiometry, detectable suprastructure). Single channel lifetimes (t) differentiate between labile and inert active structures, whereas both open probabilities and Hill coefficients indicate thermodynamic stabilities.

Supramolecular activation as a key aspect of ROP was also recently exploited by Hedrick, Waymouth and coworkers. The application of a conjoined bifunctional... 

The potential of the cluster units described here to participate in intermolecular chalcogen-chalcogen interactions combined with the easy modification of their outer coordination sphere with ligands of different nature, i.e., redox active, hydrogen donors, bi-functional, etc., make these systems useful blocks for the construction of supramolecular materials with multi-physical properties. 

Finally, to produce the structural and functional devices of the cell, polypeptides are synthesized by ribosomal translation of the mRNA. The supramolecular complex of the E. coli ribosome consists of 52 protein and three RNA molecules. The power of programmed molecular recognition is impressively demonstrated by the fact that aU of the individual 55 ribosomal building blocks spontaneously assemble to form the functional supramolecular complex by means of noncovalent interactions. The ribosome contains two subunits, the 308 subunit, with a molecular weight of about 930 kDa, and the 1590-kDa 50S subunit, forming particles of about 25-nm diameter. The resolution of the well-defined three-dimensional structure of the ribosome and the exact topographical constitution of its components are still under active investigation. Nevertheless, the localization of the multiple enzymatic domains, e.g., the peptidyl transferase, are well known, and thus the fundamental functions of the entire supramolecular machine is understood [24]. 

Although non-covalent interactions of anions are one of the most actively explored areas of supramolecular chemistry [15], the anion sensing and recognition have up to now relied primarily on electrostatic binding or hydrogen bonding to the receptor [16,54-61]. However, recent UV-Vis and NMR spectral studies clearly reveal that complex formation takes place in the solutions between halides and neutral olefinic and aromatic it-acceptors such as those in Fig. 3 [23,62],... 

It hag been shown that transition of a backbone carbon from the sp to sp state is promoted by tensile stresses and inhibited by compressive strains (10,44). The acceleration of the process of ozone oxidation of the polymers under load is not associated with the changes in supramolecular structure or segmental mobility of the chain. The probably reason of this effect is a decreasing of the activation energy for hydrogen abstraction (44). The mechanism of initial stages of the reaction of ozone with PP can be represented as ... 

Strong intermolecular interactions between active SCO mononuclear building blocks stem from the presence of efficient hydrogen-bonding networks or 7i-7i stacking interactions and have led to abrupt spin transitions [1], sometimes with associated hysteresis [2-4]. Despite the important efforts made by crystal engineers in establishing reliable connections between molecular and supramolecular structures on the basis of intermolecular interactions, the control of such forces is, however, difficult and becomes even more complicated when uncoordinated counter-ions and/or solvent molecules are present in the crystal lattice. 

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