Counterions protein aggregation

Fig. 39 Average number of 128-unit protein-like chains per aggregate as a function of reduced temperature T/Tc for counterions of different valence M z = 1, z = 2, and A z = 4. Tc is the temperature of counterion condensation. Adapted from [171]...

Articular cartilage is a complex composite polymeric material that consists principally of a network of collagen (in various states of aggregation), protein-polysaccharides, living cells (chondrocytes) and Inorganic ions. The latter are primarily counterions to the charged moieties of the polyelectrolytes of the matrix. The entire network is swollen with water, a major fraction of which is in regions between its fibrous elements. On compression this water is exuded. The tissue s network structure, composition, and equilibrium fluid contents vary with depth from the surface ( >A> ) Its structure and chemical composition have been extensively reviewed ... 

The size of the micellar aggregates is usually between 1 and 10 nm, and the aggregation number, i.e., the number of surfactant molecules per micelle, ranges from 20 to 200. Like proteins, the core of a micelle is essentially dry and consists of the hydrocarbon chains. The polar charged head groups project outward into the bulk water. Surrounding the core there is a layer composed of the ionic or polar headgroups, bound counterions, and water molecules. This layer is called the Stem layer. 

As shown in Figure 10.24, the conductance exceeds this maximum value considerably when the field exceeds about 5 kV/cm. An early explanation involved some kind of Wien effect. The first Wien effect is due to the liberation of ions from the counterion cloud around charged particles such as proteins, whereas the second one describes the creation of new charge carriers by field dissociation of week electroljrtes. Both of these effects together can explain a conductivity increase by several percent but not by 40% as seen in Figure 9.24. Moreover, this dramatic conductivity increase is only found in solution containing aggregated amphiphiles like lipids. 

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