Antiaggregation activity of chaperones and its quantification

Methods for the quantitative estimation of the antiaggregation activity of protein chaperones (first of all, small heat shock proteins) and chemical chaperones including amino acids, carbohydrates, polyamines, and cyclodextrins are discussed. Based on analysis of the plots of light scattering intensity or apparent optical absorption versus time, formulas for calculation of initial rate of aggregation of protein substrate and lag period on kinetic curves of aggregation were derived. Possible determination of the stoichiometry of chaperone-protein substrate complex from the dependence of the initial rate of aggregation on the ratio of protein chaperone/protein substrate concentrations is discussed. To characterize efficiency of the protective action of chemical chaperones, the [L]0.5 value can be used ([L]0.5 is the concentration of a chemical chaperone at which twofold decrease in the initial rate of aggregation occurs). Methods for quantitative estimation of the combined protective action of chaperones are discussed.