Figure 7.

Concentration measurements with fluorescamine for Aβ samples incubated at 37°C (a) or 4°C (b). Four Aβ42 samples (referred to as 1, 2, 3 and 4) were prepared separately in PBS buffer. Incubation at 37°C leads to rapid aggregation of Aβ42, and consequent reduction in apparent concentrations measured using the fluorescamine method (a). This is due to the reduction of the number of solvent-accessible lysine side chains as a result of protein aggregation. By contrast, only small changes were observed for Aβ42 samples incubated at 4°C at similar concentrations (b), suggesting that Aβ42 remains soluble at 4°C during the incubation period.