Ionic assemblies molecular associations

Soft templates, usually molecules and molecular associations such as amines, thermolabile organic polymers, and surfactants, can be removed by heat treatment. In addition, vesicles, ionic liquids, self-assembled colloidal crystals, and air bubbles have been used for soft templating synthesis. 

Ionic (electrostatic) interaction may also lead to cyclic self-assembly. Numerous alkah metal and alkahne-earth molecular compounds fall into this category. These include three types of associated ring compounds ... 

The polar, ionic and even non-ionic head-group interactions of lipid membranes and other surfactants, (as indeed for many polymers and polyelectrolyte intra-molecular interactions) and the associated curvature at interfaces formed by such assemblies will be dependent on dissolved gas in quite complicated ways. Fluctuating nanometric sized cavities at such surfaces will be at extremely high pressure, (P = 2y/r, y= surface tension, and r the radius) resulting in formation of H and OH radicals. The immediate formation of Cl radicals and consequent damage to phospholipids offers em explanation of exercise-induced immunosuppression (through excess lactic acid CO2 production), perhaps a clue to the aging process. 

The description of structure in complex chemical systems necessarily involves a hierarchical approach we first analyse microstructure (at the atomic level), then mesostructure (the molecular level) and so on. This approach is essential in many biological systems, since self-assembly in the formation of biological structures often takes place at many levels. This phenomenon is particularly pronounced in the complex structures formed by amphiphilic proteins that spontaneously associate in water. For example myosin molecules associate into thick threads in an aqueous solution. Actin can be transformed in a similar way from a monomeric molecular solution into helical double strands by adjusting the pH and ionic strength of the aqueous medium. The superstructure in muscle represents a higher level of organisation of such threads into an arrangement of infinite two-dimensional periodicity. 

Crystal deconstruction is the process that leads backwards. in a reverse "aufbau process, from the structure of a molecular crystal to the component molecules or ions. Crystal deconstruction allows one to focus on the interactions that are more relevant for crystal structure cohesion. The objective of the deconstruction process is also that of learning about the factors responsible for molecular/ionic recognition and self-assembly in the solid state. Insights into crystal polymorphism can be gained by comparing the different distributions of intermolecular interactions associated with the existence of different crystal forms of the same molecular species. 

However, it is not only from an architectural viewpoint that dendrimers can be contrasted to organized assemblies. but micellar stabilization and organization of species in uncharacteristic environments are also suggested. Thus, stmctural attributes of branched frameworks ean be employed for such applications as aqueous solubilization of inherently water-insoluble species as well as molecular ordering based on noneovalent interaetions, such as //-bonding and ionic associations. The advent and current status of several dendritic micelles are herein ehronicled. 

Figure 6 Molecular model of O2 sensor complex in NEB cell. Shown is the a-jS potassium (K+) channel complex with tetramer of a-subunits forming the ionic pore, -subiuiits interact with the assembly domains T1 in the cytosol. A positively chaiged amino terminal ball domain of the a-subunit (and possibly of the -subunit) underlies fast inactivation. The reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase complex is shown to be associated with this K+-channel complex in NEB cells. Reactive oxygen intermediates produced by the NADPH oxidase modulate the inactivation process by oxidizing specific cysteine residues in the amino terminus, forming disulfide bridges with other cysteines located in the channel and thus immobilizing the inactivation balls. (From Ref 78, Courtesy of Dr. Honore.)...

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