Reagents and solutions

BSA and phosphate-buffered saline (PBS) (pH 7.4) were prepared from Merck. The double distilled water was operated as the solvent in the preparation of the PBS solution. The stock solution of BSA (2mM) was prepared by dissolving the appropriate quantity of protein in PBS solution. Nisin was bought from Sigma-Aldrich Company. The experimental stock concentration of nisin (2 mM) was attained by dissolving proper amount of nisin powder in 2 mL of PBS solution. Finally, all solutions were preserved at a low temperature (277 K).