One recent sample contained a moderate number of fibre-like particles, but all other samples were typical of fine-grained ash (blocky, angular with electrostatic or chemical aggregation of finer particles on larger ones).
Many chaperones are also stress proteins and protect polypeptides from denaturation and aggregation when facing physical or chemical stress (Macario 1995).
Typically, the chaperone-like function has been studied in vitro by measuring the ability to prevent protein aggregation induced by different physical or chemical conditions, such as temperature or denaturants [ 5, 46].
Large numbers of charged amino acids, such as K and E, have been shown to prevent aggregation, even under conditions that normally cause proteins to aggregate, such as heating or chemical denaturation (Lawrence et al., 2007).
In general, chaperones are known as proteins that are involved in folding nascent proteins; furthermore, many chaperones protect polypeptides from denaturation and aggregation in the face of physical or chemical stress (Macario 1995 ).
The aggregation can be caused by magnetic, electrostatic or chemical interactions between particles.
Furthermore, expression of the relatively insoluble subunits of simple epithelial keratins carries the risk of protein aggregation induced cellular disease [30]in the event of mutation, imbalance of subunit expression, chemical induced aggregation or deficient degradation [31].
However, these strategies can have drawbacks such as poor expression (recombinant fusions) or aggregation and inactivation (chemical cross-linking), especially in the case of large multifunctional proteins.
Elevated temperature, shaking (shear and airliquid interface stress), surface adsorption and other physical or chemical stress factors facilitate the aggregation of unfolded proteins.
