Figure 3. Optical response of the two layers in a pepsin-loaded nanoreactor upon introduction of α-casein.
The solid trace (“Layer 1”) represents the top layer of the nanostructure containing 100 nm-diameter pores. The dashed trace (“Layer 2”) corresponds to the bottom layer, which contains much smaller 6 nm-diameter pores. A solution of the α-casein protein substrate is introduced to the system at time = 0. The value of 2nL for Layer 1 initially increases as intact casein infiltrates the layer, and then it decreases as casein is digested by pepsin. The value of 2nL for Layer 2 increases as the smaller products of enzymatic digestion diffuse into the small pores of this layer.