Figure 4. Impact of light and oxidative stress on microcystin binding to proteins.

A) Immunoblot analyses of soluble Microcystis protein extracts with an anti-microcystin antibody after high light treatment of 700 µmol photons m⁻² s⁻¹ for up to 4 hours. The irradiation time of the individual samples is indicated. The sample 4′h was irradiated with high light for three hours and subsequently transferred to low light for one hour. B) Immunoblot analysis of a low light adapted culture (C) that was treated for 4 hours with 700 µmol photons m⁻² s⁻¹ high light (HL), 10 µM H₂O₂ or in parallel grown under low light in the absence of iron (-Fe). Immunoblot analysis of a low light adapted culture of the ΔmcyB mutant and a culture treated for three hours with high light (700 µmol photons m⁻² s⁻¹) after microcystin addition.