Se K-edge X-ray absorption near-edge spectra of A549 cells treated with selenite. Cells were cultured to yield a monolayer as described in the Methods section. Next, the monolayers were treated with 1 μM selenite for 24 h or 5 μM selenite for 1, 4, 24, 48 or 72 h, then worked up and X-ray absorption near-edge spectral analysis performed as described in detail in the Methods section.