Change in value of Na+, K+-ATP-ase activity (A/A0%) of membrane fraction from cell line U937 under AuNP influence. Sizes of 1–10, 2–20, 3–30, and 4–45 nm. (M ± m; n = 5, P < 0.05 relative to control A0). For 100% (control) adopted the value Na+, K+-ATP-ase activity in the absence of gold nanoparticles. Gold nanoparticles in the environment made fiber membrane fraction (150–200 mg) and the mixture was incubated for 3 min. Incubation medium for determination of enzyme activity (volume 1 ml) is 50 mM Tris–HCl, 5 mM MgCl2, 100 mM NaCl, 20 mM KCl, 3 mM ATP (pH = 7.5). Incubation period is 10 min, and temperature is 37°C. The amount of membrane protein is 15–20 mg.