Pigments acid-base sites

Prof. Fowkes s flow calorimetric work led to important advances in the understanding of the interactions between mineral fillers, polymers, and polymer additives. The work of S. T. Joslin and F. M. Fowkes [29] in which they time-sliced the outputs from an FMC and its accompanying DSD enabled them to determine differential molar heats of adsorption as a function of progress in the adsorption process, and gave an indication of the heterogeneity of strength of the acid or base adsorption sites on the filler or pigment surfaces. 

In some senses enzymes with copper at their active sites act in an opposite manner to those with zinc at their active sites. Copper-based enzymes are responsible for carrying out oxidation reactions which lead to formation of organic stmc-tural polymers such a collagen and melanin (responable for protection against UV radiation). Copper-based enzymes have two copper atoms in the Cu(I) oxidation state at their active site to which molecular oxygen becomes bound. Figure 26.33 shows the action of the copper-based enzyme tyrosinase which oxidises the amino acid tyrosine to produce dopachrome, the precursor of the melanin pigments. 

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