Cooperativity hydrophobic interfaces

Fig. 7. Schematic illustration of free energy assignments for three different types of interactions. The examples illustrate the situation existing for folded, unfolded, and one partially folded intermediate. For hydrophobic interfaces, partially folded intermediates always include an extra term Ag corresponding to the solvent exposure of protein regions that have not undergone unfolding. The unfolded state lacks this uncompensated exposure term. For a bonded or liganded interface, cooperative behavior is created when the unfolding of either domain results in the disruption of the bonded interface or the dissociation of the ligand molecule. [Reprinted from Freire el al. (1991)].

Positive Cooperativity Due to Changeable Hydrophobic Interface Between aP Dimers... 

This chapter discusses stereospecific intermolecular interactions in monolayers at the air-water interface, where surface-active molecules (surfactants) are partially oriented with respect to each other by the cooperative combination of interionic, hydrophobic, and hydrogenbonding forces. We believe that these reports should be of particular interest in relation to stereospecificity in assemblies such as micelles, vesicles, and bilayer membranes, where their significance has been largely ignored. 

The hydrophobic effect does a minimum number of hydrocarbon chains must associate before the water-hydrocarbon interface is eliminated. This association process is a cooperative one, and the micelles therefore have a minimum size. 

Fig. 4. Redox cooperation of hydrophobic vitaminE and hydrophilic vitaminC. Ascorbate (AH-) acts as an electron-transfer agent at the water/membrane interface. Note that one molecule of lipid hydroperoxide LOOH is produced for each termination reaction by vitamin E. See the discussion in...

The 77 values of (3-lg/PGA films (0.1 wt% PGA in the bulk phase) showed an antagonic behavior when compared to the tto( single (3-lg and PGA films, which should be attributed to their high degree of esterification (higher hydrophobicity) that allows them to rapidly adsorb at the interface. However, in the presence of KO at 0.5% (Figure 25.1a), the system showed a more cooperative adsorption. Similarly, KLVF at 0.5% increased tt of the mixed system. The increased cooperativity as PGA increased from 0.1 to 0.5% may be ascribed to an increase of segregation phenomena in the bulk solution. 

Should the structural data show the a p -a p interface to be one of hydrophobic association that is disrupted on oxygenation, then in our view the answer is clearly yes, the cooperative binding of oxygen to hemoglobin results from the consilient mechanism. In our view the presence of hydrophobic association at the a P -a P interface would indicate that positive cooperativity, essential to hemoglobin function in oxygen transport, arises due to the consilient... 

Another class of metalloporphyrin species of remarkable photoactivity at the liquid/liquid interface is formed by the electrostatic association of oppositely charged species . The electrostatic attraction between the charged substituents and the hydrophobic interaction of the aromatic macrocycles cooperate in holding the individual species in close proximity such that extensive orbital overlap can... 

The polyelectrolyte coated surface is uncharged, or in the case of AM-MAPTAC-30 weakly positively charged, before SDS is added. When SDS associates with an uncharged polyelectrolyte layer it will result in a recharging of the interface which results in the development of an electrostatic double layer and a less favorable polyelectrolyte-surface interaction. Thus, the polyelectrolyte-surfactant association at the mica surface is counteracted by electrostatic forces. Instead, it is driven by the hydrophobic interaction between the surfactant tails. This is confirmed by the cooperative nature of the association process observed for all polyelectrolyte-surfactant systems studied in this report. It is well known that hydrophobic interactions are very important also for the association between polyelectrolytes and surfactants in bulk solutions as demonstrated by the cooperativity of this process [16]. The... 

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