Noncovalent aggregates

The combining of two or more substances or molecular entities to yield a single substance or molecular entity, a process that involves either covalent or noncovalent bonding. Included in this definition is the formation of ion pairs from free ions, the noncovalent aggregation of monomers to form polymeric structures or complexes, as well as colligation. The opposite of association is dissociation. 

Figure 6 Characterization data for some noncovalent aggregates (A) H NMR spectra in CDCI3 for 1) 6a, 2) Hub(M)3 and 3) and an expansion of the imide region for 6b, (B) a table showing the calculated and experimentally determined (ES-MS and VPO) molecular weights for several aggregates and (C) GPC chromatograms for five aggregates...

Researchers, primarily from Moscow State University, Russia, have also formed noncovalent aggregates between enzymes and polymers [palmitoylated poly (sucrose acrylate)], polyelectrolytes (polybrene), and block copolymers. Reported enzymatic activities were high. For the former, activity decreased as the molecular weight and degree of palmitoylation increased. Chymotrypsin-polyelectrolyte and -block copolymer complexes were active in aqueous-polar organic co-solvent mixtures when the ionic strength was increased. " ... 

Reaction of calixarene (47) and CO2 is special, because it converts linear supramolecular polymeric chains (48) into supramolecular, 3D polymeric networks (46). These are also switchable and can be transformed back to the linear chains (48) without breaking them. While supramolecular cross-linked polymers are known (92), they break upon dissociation of the noncovalent aggregates that compose them. Material 46 is different, as it only releases CO2 and keeps hydrogen-bonding intact. 

Precipitation is a macroscopic process characterized by a visible change of an otherwise clear solution in the form of an increase in solution viscosity, clouding of solution, or phase separation of solid materials. The formation of precipitates may be due to covalent polymerization and/or noncovalent aggregation (Section 4.3.2.2). In covalent polymerization, dimer formation usually precedes the precipitation, and the phenomenon is best illustrated by insulin, which has been extensively reported to form covalent dimers. 

Surfactant molecules having a hydrophilic head and hydrophobic tail portion when present in aqueous solution generate micellar structures above critical micelle concentration (CMC) by noncovalent aggregation of individual surfactant molecules. The micelles generated can be either spherical or irregular in shape, hi micelles, surfactant molecules form walls of spherical structure in such a manner that the hydrophilic head portion faces outward and hydrophobic tail is toward the interior of the micelles, thus generating a hydrophobic core (Figure 1.6). Surfactants have been used for micellar... 

Many proteins exist as stable and ordered noncovalent aggregates of more than one polypeptide chain. The overall structure of a protein having multiple subunits Is called its quaternary structure. The quaternary structure of hemoglobin, for example. Involves four subunits (see Section 24.12). 

The impact of noncovalent aggregation depends greatly on its degree of reversibility under conditions of analysis and administration in vivo. Noncovalent aggregation can result... 

Glucagon-Like Peptide-1 Analog Large Soluble Noncovalent Aggregates... 

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