Figure 7. Amino acid hydroperoxides produced by plasma treatment of organic medium induce DNA damage.

(A) Cells were treated with 100 µl of medium or PBS that was separately exposed to 1.55 J/cm² plasma. (B) 100 µl of PBS, medium without serum, or PBS with 100 µg/ml BSA were treated with plasma (1.55 J/cm²) and immediately added to cells on a coverslip (separated, S). Cells overlaid with 100 µl of the indicated solution were treated with plasma (1.55 J/cm²) (direct, D). (C) Solutions containing the indicated amino acid (100 µM) were separately treated with plasma and then added to MCF10A cells. (A, B, C) After 1-minute incubation, cells on cover slips were diluted in 2 ml medium, followed by lysis and Western blot for γ-H2AX and α-tubulin. (D) Peroxidation efficiency of various amino acid components of cell culture medium when treated with IR [43]. For each amino acid, the amount of DNA damage induced is proportional to the peroxidation efficiency.