Quantum effects in biological function

6 problems

• How cryptochrome radical pairs stay coherent long enough to sense Earth's field

  Open

  Migratory birds are thought to sense the direction of Earth's magnetic field through pairs of molecules with one unpaired electron each (radical pairs) in an eye protein called cryptochrome. Calculations say the electron spins lose their correlation too fast for so weak a field to matter, so either the calculations miss something or the receptor works differently.

• Does proton tunneling between DNA bases cause a measurable share of mutations?

  Open

  The hydrogen atoms holding DNA base pairs together can jump across, briefly creating rare forms of the bases that pair wrongly when DNA is copied. The question is whether this quantum jumping produces a noticeable fraction of the natural mutations in living cells.

• Do fast protein vibrations drive hydrogen tunneling in enzymes?

  Contested

  Many enzymes move a hydrogen atom by quantum tunneling, passing through rather than over an energy barrier, as seen from how much the reaction slows when hydrogen is replaced by heavier deuterium. Whether specific fast protein motions speed the reaction, or the protein only sets the shape of the barrier, is disputed.

• Does electronic coherence speed or protect photosynthetic energy transfer?

  Contested

  In photosynthesis, energy from absorbed light hops between pigment molecules to a reaction center where it is stored, and laser experiments show wave-like oscillations during this transfer. It is unclear whether these quantum oscillations make transfer faster or more efficient, or are a side effect of molecular vibrations.

• Why very weak radio-frequency noise disrupts the bird magnetic compass

  Contested

  Experiments report that weak radio noise, far weaker than Earth's magnetic field, makes migratory birds lose their compass sense. Radical-pair theory predicts such weak noise should only work if the electron spins stay correlated far longer than seems possible.

• Do coherences exist at all under natural incoherent sunlight?

  Open

  Laser pulses in the lab start all molecules oscillating together, but sunlight arrives as a steady random stream of photons. The question is whether any quantum coherence relevant to energy transfer exists inside a leaf in real light.