Internal levels of copper were measured by atomic absorption spectrometry and normalized to protein content. The following treatments are displayed in this graph: YM, 157 μM c-CuNP, 400 μM CuSO4, 100 μM GSH, 100 μM NAC, 157 μM c-CuNP + 100 μM GSH, 157 μM c-CuNP + 100 μM NAC, 400 μM CuSO4 + 100 μM GSH, and 400 μM CuSO4 + 100 μM NAC. The graph is rescaled to better show the concentrations of the controls. The average of three independent samples for each treatment was determined and plotted error bars.