New opportunities with VUV and soft-X-ray free electron lasers: Biological systems

Biology is deeply influenced by the structure of biomolecules, the dynamics of biomolecules, the way that biomolecules interact with each other, and how the cellular architecture is influenced by the structure and dynamics of the molecular components. At its most fundamental level, the length scale of these structures and dynamics of primary biological components is on the 1-100 nm length scale. Although there are ingenious optical techniques that reach into that length domain, they involve highly specific and robust optical probes and averaging techniques to find the standard deviation of the mean, greatly limiting our ability to observe the real-time dynamics of cell components at a fundamental level. It is now clear that unraveling the response of cells to ionizing radiation is critical for understanding many fundamental problems in biology, from aging to apoptosis (programmed cell death) to the origins of cancer. Since a cell is spatially highly heterogeneous, simply irradiating cells results in the activation of many different biological pathways. The high brightness of a coherent X-ray/VUV light source would allow irradiating cell components with 100 nm or better spatial resolution, which would be a major step forward in unraveling the response of cells to genomic and component damage.