Just when biologists thought they were getting a handle on some of the molecular behavior in cells, along come other scientists to reveal that at least in photosynthesis the ‘crazy’ world of quantum mechanics has been put to work. Oh my, indeed. Not that this comes as a huge surprise. Quantum physics underlies everything in the physical world. It’s just that for humans, quantum just about anything is not, or counter, intuitive. Better still, when scientists work with quantum behaviors, it requires extremely powerful microscopes and extremely cold temperatures. Not a comfortable milieu for research. Now, however, it appears that plants have adapted to quantum behavior for producing energy from sunlight, and do it at normal temperatures.
The pioneering work, done by a team of chemists at the University of Toronto (Canada), started with collecting what are called ‘light-harvesting complexes’ from two species of marine algae. Light-harvesting complexes capture photons from sunlight and use them to excite electrons in protein compounds to higher levels – a transfer of energy. Later that energy can be attached to organic compounds, such as glucose (sugars), for storage. These light-harvesting complexes were stimulated with femtosecond pulses of laser energy to simulate sunlight, and observed with a two-dimensional electronic spectroscope. What they found was that during this conversion the same quanta of energy existed in two places at once (in the photon and in the electrons) – a quantum superposition – which is a hallmark characteristic of quantum mechanics.
This was a surprising and highly suggestive result. As one of the researchers put it:
“There’s been a lot of excitement and speculation that nature may be using quantum mechanical practices,” says chemistry professor Greg Scholes, lead author of a new study published this week in Nature. “Our latest experiments show that normally functioning biological systems have the capacity to use quantum mechanics in order to optimize a process as essential to their survival as photosynthesis.”
“This and other recent discoveries have captured the attention of researchers for several reasons,” says Scholes. “First, it means that quantum mechanical probability laws can prevail over the classical laws of kinetics in this complex biological system, even at normal temperatures. The energy can thereby flow efficiently by—counter intuitively—traversing several alternative paths through the antenna proteins simultaneously. It also raises some other potentially fascinating questions, such as, have these organisms developed quantum-mechanical strategies for light-harvesting to gain an evolutionary advantage? It suggests that algae knew about quantum mechanics nearly two billion years before humans,” says Scholes.
The finding also suggests that if this quantum-based process is correctly identified, that other biological processes may also utilize quantum mechanics in ways that, up to now, science has not even considered. Oh my, goodness.