Radiation track structure, nanoscale dose and DNA damage

7 problems

• Ab initio prediction of complex DNA damage yields

  Open

  Radiation sometimes breaks both strands of DNA at nearby places, which cells repair badly. Predicting how often this happens, starting from physics alone, is not yet possible.

• Electron interaction cross sections in liquid water below 100 eV

  Open

  Most of the damage is done by very slow electrons, but how those electrons scatter in liquid water is poorly measured. Simulations therefore rest on guesses in exactly the range that matters.

• Sub-keV electron emission spectra from irradiated gold nanoparticles

  Open

  When a gold particle absorbs an x-ray it releases a burst of slow electrons whose number and energies set the local damage. Simulation programs disagree on that burst.

• Nanoparticle enhancement in proton and carbon-ion beams

  Contested

  Gold adds little extra absorbed dose in proton beams, since protons interact with electrons in almost the same way regardless of the element. Some experiments still report enhanced killing, others report none.

• Why gold nanoparticles sensitize cells in megavoltage photon beams

  Open

  At the high photon energies used in the clinic, gold should add almost no extra absorbed dose, yet experiments report clear extra cell killing. The source of the extra effect is unknown.

• Which nanoscale observable predicts biological effect

  Open

  Dose alone does not predict biological damage for different particle types. The question is which microscopic measure of the energy pattern does.

• Radiation chemistry beyond the homogeneous stage

  Open

  Water split by radiation produces reactive fragments whose numbers change over nanoseconds to seconds. Current models stop too early to describe what reaches biological targets.