Page 43 - University of Pretoria RESEARCH REVIEW 2018

The molecular mechanisms of photosynthesis
Tjaart Krüger, Department of Physics
A vast number of organisms perform photosynthesis, each
using unique pigment-protein complexes to capture the light from the sun and to transfer it to a photochemical reaction centre, first to convert the photoenergy into protons and electrons, and later into energy-rich molecules. These light-harvesting complexes do their job extremely efficiently.
molecule spectroscopy, which allows them to investigate one molecule
or protein at a time. As pioneers
in the application of this technique to photosynthetic light-harvesting complexes, they published an Invited Review in the journal Nanophotonics with colleagues in the Netherlands.
Postgraduate students in the team have built the first single molecule spectroscopy unit on the African continent to investigate light- harvesting complexes. They have demonstrated, in real time, how a small protein is activated by light and binds to phycobilisome to switch off its photosynthetic activity. This was the first time that the interaction between these two physiological partners had been investigated at the level of a single molecule. The results of this study were published in the Journal of Physical Chemistry Letters in 2018.
The main interest of Tjaart
Krüger, Associate Professor in
the Department of Physics, and his Biophysics research team, is in the molecular mechanisms of natural photosynthetic complexes. These are a rich source of inspiration for solar cell technologies and extremely useful for biotechnologies aimed at optimising photosynthesis for agriculture.
Krüger’s team have discovered that the light-harvesting complexes of diatoms use a different strategy
from plants to ensure robust energy transfer by using the laws of quantum mechanics to create a new, favourable energy state and exploiting disorder to populate this state. The results were published in the Proceedings of the National Academy of Sciences in December 2017. This was followed by a particularly fruitful year in 2018, with the publication of nine peer-reviewed papers, one textbook and four popular science articles.
In an invited Headline Review published by the Journal of the Royal Society Interface, Professor Krüger provided a perspective on
the future of the emerging field of quantum biology, which is expected to have a huge impact on numerous technologies. His team’s involvement with this work has been the result
of collaboration with international leaders in the field.
The research team has been able
to unravel many molecular details behind the very first steps in the photosynthetic process by developing novel equipment to push the analytical resolution to the technological limits. Their main experimental tool is single
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