424 9.5  Extending Length and Time Scales to Quantum and Ecological Biophysics

energy is significantly higher than the thermal energy scale for energy transitions equivalent

to ~kBT, then this exchange, if observed experimentally, cannot be explained classically, but

can be explained by modeling the exchange as due to discrete quanta of energy.

Experiments to probe the electronic–​vibrational resonance in chlorophyll molecules have

been performed in vitro using time-​resolved femtosecond electron spectroscopy. Analysis of

these data indicates a so-​called negative joint probability for finding the chlorophyll molecules

within certain specific relative positions and momenta. Classical physics predicts that these

probability distributions are always positive, and therefore this represents a clear signature of

quantum behavior.

That being said, the absolute thermal energy scale of ~kBT at 300 K is still much higher

than that expected for likely quantum coherence effects by several orders of magnitude. In

other words, at ambient “room” temperature of biology, one might expect the surrounding

molecular chaos in the cell to annihilate any quantum coherence almost instantly. But recent

simulations suggest that quantum coherence may still result in a level-​broadening effect of the

free energy landscape—​flattening out local minima due to thermal fluctuation noise thereby

increasing the overall efficiency of energy transport—​possibly by up to a factor of two.

A related recent study involves quantum coherence observed in the enzyme lysozyme

(discussed previously in Chapter 5). In this study (Lundholm et al., 2015), the researchers

found evidence at very low ~1 K temperatures for coupled electrical dipole states in crystals

of lysozyme following the absorption of terahertz radiation. This observation was consistent

with a previously hypothesized but hitherto undetected state of matter called a “Fröhlich

condensate,” a vibrational ground state of dielectric matter analogous to the Bose–​Einstein

condensate on bosons, in which quantum coherence results in an extended state of several

coupled electric dipoles from different molecules over a long length scale equivalent in effect

to the whole crystal.

Although highly speculative, theoretical physicist Roger Penrose and anesthesiologist

Stuart Hameroff (Penrose et al., 2011) had previously hypothesized that microtubules inside

cells might function as quantum computing elements, driven by quantum coherence over

the long length scales of microtubule filaments. Normally, a wave function, as a superpos­

ition of all quantum states, is expected to collapse upon an interaction between the quantum

system and its environment (i.e., we measure it). However, in this system the collapse was

hypothesized not to occur until the quantum superpositions become physically separated in

space and time, a process known as objective reduction, and when such quantum coherence

collapses, then an instant of consciousness occurs. The physical cause of this hypothetical

coherence in microtubules was speculated by Penrose as being due to Fröhlich condensates

(Fröhlich, 1968). Previously, experimental studies failed to identify Fröhlich condensates,

so this recent study, although still hotly debated, may serve to propagate this speculation

of quantum-​based consciousness a little further. However, at present, it is going too far to

make a link between quantum mechanics and consciousness; the evidence is enormously

thin. But the key thing here is that the Fröhlich condensate has been a controversy for over

half a century, and now if these new experimental results support the Fröhlich hypothesis, it

means that biological systems may have the potential to show quantum mechanical coher­

ence at room temperature. This would clearly influence the organization of many biological

processes and the transmission of information, in particular.

A fourth, and perhaps more mysterious, example of nontrivial quantum biology is the

geonavigation of potentially many complex multicellular organisms. There is good experi­

mental evidence to support the theory of magnetoreception in several organisms. This is the

sense that allows certain organisms to detect external magnetic fields to perceive direction/​

altitude/​location, and ultimately use this to navigate. For example, Magnetospirilum bacteria

are magnetotaxic (i.e., their direction of swimming is affected by the direction of an external

magnetic field), common fruit flies appear to be able to “see” magnetic fields, homing pigeons

appear to respond to magnetic fields as do some mammals such as bats, and similarly salmon,

newts, turtles, lobsters, honeybees even certain plants such as the model organism mouse ear

cress (see Chapter 7) respond in growth direction to magnetic fields, though arguably in all

of the experimental studies tried to date the size of the artificially generated magnetic field

used is much larger than the native Earth’s magnetic field by an order of magnitude or more.