Determination of the Optimal Labeling Amount of p30 and p72 Protein
The p30 protein was diluted 2-fold from 0.1 to 0.00625 mg/mL using 0.1 M PBS, while the p72 protein was diluted 2-fold from 0.25 to 0.001952125 mg/mL using 0.1 M PBS. Afterward, 0.1 mL of the diluted p30 or p72 protein was added to the gold solution with adjusted pH, mixed thoroughly, and left to stand at room temperature for 8–10 min. Subsequently, 0.1 mL of 10% NaCl solution was added and mixed thoroughly, and the color change was observed after 2 h. The minimum protein label amount was recorded, and 20% was added to the minimum label amount to obtain the best protein label amount (Hampl et al., 2001).