The sun is the source of growth for thousands of lives on Earth, and through photosynthesis, sunlight is converted into chemical energy. As the largest organic synthesis process in the biological world, photosynthesis is arguably the most important chemical reaction for life.
Organisms that can carry out photosynthesis, in addition to our common green plants, there are also some photosynthetic bacteria, for example, green sulfur bacteria (Chlorobium tepidum) is one of them. Recently, American scientists discovered that green sulfur bacteria can use quantum mechanical effects to regulate the process of photosynthesis.
Chlorobium tepidum is one of the world’s oldest photosynthetic bacteria, having been created more than three billion years ago. In the early days, when the Earth was extremely anoxic, green sulfur bacteria were a class of anaerobic photosynthetic bacteria.
How is energy transferred in photosynthetic proteins? And what controls the choice of energy transfer pathways? The researchers studied the photosynthetic performance of green sulfur bacteria in both aerobic and anaerobic environments and found that vibronic coupling, a quantum effect, is the key to the problem, directing where energy is transferred.
The word “vibronic” is derived from vibrational and electronic, and refers to the concept that in molecules, electron motion and nuclear vibrations are intertwined, deeply intertwined and indistinguishable.
In green sulfur bacteria, a complex called FMO is used to capture light energy; and mycophyll, like plant chlorophyll, is the site where photosynthesis occurs. In the anaerobic state, the difference between the energy levels of the two electronic states of the FMO and the vibrational energy of the bacteriophage molecule coincide.
Thus, through the electronic vibrational coupling, an energy transfer “highway” is opened, and the energy flows unimpeded to the “reaction center” of photosynthesis, which is filled with chlorophyll molecules, and the situation becomes very different when the environment is enriched with oxygen.
A pair of cysteine residues in the FMO complex reacts with the oxygen in the environment and each loses a proton. This breaks the harmony between the electronic state energy levels and the vibrational energy of the molecule.
The electron vibrational coupling is broken and the “highway” of energy transfer is interrupted. Energy is diverted to other paths leading to various places where it is continuously lost. The green sulfur bacteria lose energy, but are protected from oxidative damage and are able to “save their lives. This is an insight into biology through the regulation of quantum effects to achieve survival options.
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