Calcium carbonate precipitation: Effect of protein additives and concentrations.

The effect on pH drop is illustrated by selected time points at t = 0 sec, 20 sec and 400 sec. The initial ΔpH (0–20 sec) is 0.3±0.1 for all experiments (n = number or replications). Significant differences become visible only after several minutes. For HCO3– as first ionic interaction partner, the second pH shift (ΔpH 20–400 sec) is lacking at high GFP and GFP-perlucin protein concentrations (25 µg and 100 µg) (values highlighted in bold). For Ca2+ as the first ionic interaction partner, the second pH shift (ΔpH 20–400 sec) is reduced compared to experiments with low protein concentration (0.4 µg/ml), or with Concanavalin A (2 µg/ml or 8 µg/ml). This demonstrates that the assay is extremely sensitive to certain parameters such as protein concentration and selected precursor solution in which the protein is supplied first.