Chaperone efficiency in reaction

The subsequent evaluation of rate constants33,38 has shown that k66 is three times as large as k 63 at room temperature if Ar is the chaperone for reaction (3-63). If Cl2 is the principal chaperone, and if it is not more than three times as efficient as Ar, then reaction (3-63) is not in equilibrium at room temperature and below eq. (3-1 ) must be used. Of course if another gas is the principal chaperone gas or if Cl2 is much more efficient than Ar as a chaperone, then reaction (3-63) is in equilibrium above room temperature, and eq. (3-T) reduces to eq. (3-1). The experiments of Burns and Dainton33 exhibited a slight falloff for (CC120) at high [Cl2] as predicted from eq. (3-1). Thus the indications are that eq. (3-T) must be used, that Cl2 is not unusually efficient in reaction (3-63), and thus that there is no evidence for a Cl3 intermediate. 

If the value used for k6 is correct (a slight change in the activation energy used could markedly offset the value), NO and/or HI is about 300 times as efficient as the chaperones used in other studies. Thus, the observed intermediate order of the reaction is entirely reasonable. 

FIGURE 8.5 Structuration of an IDP upon binding to membrane lipids. When an IDP comes close to a membrane, specific interactions with selected lipids (such as gangliosides in lipid rafts) will favor the efficient adhesion of the protein to this membrane. Moreover, the repetitive head groups of raft lipids wiU induce a-helical folding of the protein through a typical chaperone-facilitated reaction. The reduction of dimensionality from 3D (extracellular milieu) to 2D (hpid raft surface) also favors the concentration of the protein on the membrane surface. The Parkinson s and Alzheimer s disease-associated proteins a-synuclein and p-amyloid peptides (Ap) are typical examples of such IDPs that acquire a helical structure when bound to hpid rafts of neural cells. 

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