The Importance of Disordered Protein Arrangement in Photosynthetic Cells

The Importance of Disordered Protein Arrangement in Photosynthetic Cells

Photosynthesis is a vital process that allows cells to convert light into energy. Central to this process are the light-harvesting proteins, which absorb photons and transfer their energy to produce sugar molecules. A recent study conducted by chemists at MIT has shed light on how the disorganized arrangement of these proteins enhances energy transduction efficiency.

Light-harvesting proteins, also known as the antenna, play a crucial role in photosynthetic cells. They absorb photons and transfer their energy between a series of proteins until it reaches the photosynthetic reaction center. This transfer of energy is highly efficient, with nearly every absorbed photon generating an electron. This phenomenon, known as near-unity quantum efficiency, is crucial for the cell’s energy production.

The study conducted by the MIT chemists aimed to understand how the disorganized arrangement of the proteins in the light-harvesting complex contributes to its high energy transduction efficiency. The researchers discovered that the disordered organization of the proteins enhances long-distance energy transfer, a critical process for the antenna’s operation.

Previous studies have focused on how energy moves within a single protein using ultrafast spectroscopy. However, studying the transfer of energy between proteins has proven challenging. To overcome this hurdle, the MIT researchers designed synthetic nanoscale membranes called nanodiscs. These membranes allowed them to control the distance between two proteins embedded within them, enabling them to measure energy transfer between the proteins.

The researchers embedded two versions of the primary light-harvesting protein found in purple bacteria, LH2 and LH3, into the nanodiscs. Using cryo-electron microscopy, they confirmed that the positioning of the proteins closely resembled that of proteins in native membranes. The distances between the light-harvesting proteins ranged from 2.5 to 3 nanometers.

By utilizing ultrafast spectroscopy and the slight difference in light absorption between LH2 and LH3, the researchers observed energy transfer between the two proteins. They found that proteins positioned closely together allowed for faster energy transfer, taking approximately 6 picoseconds for a photon to travel between them. In contrast, proteins spaced farther apart required up to 15 picoseconds for energy transfer.

The efficiency of energy transfer relies on the speed of the transfer, as a longer journey results in more energy loss. The researchers concluded that the disordered arrangement of the proteins in living cells is more efficient compared to a lattice structure. This finding challenges the assumption that biological systems are inherently disordered. Instead, organisms may have evolved to take advantage of this disordered organization.

Having established the ability to measure inter-protein energy transfer, the researchers plan to further investigate energy transfer between other proteins, such as those in the antenna to the reaction center. They also aim to study energy transfer in antenna proteins found in organisms other than purple bacteria, including green plants. By gaining a deeper understanding of the mechanisms behind efficient energy transduction, scientists can potentially develop more efficient energy conversion systems inspired by nature.

Understanding the mechanisms behind efficient energy transduction in photosynthetic cells has significant implications for various fields, including renewable energy and bioengineering. By unraveling the complexities of energy transfer, scientists can potentially develop more efficient energy conversion systems. Inspired by the disordered organization of proteins in living cells, new technologies may be developed to enhance energy conversion and drive advancements in renewable energy sources.

The MIT study provides valuable insights into the disordered arrangement of proteins in the light-harvesting complex of photosynthetic cells. The findings highlight the crucial role of this organization in enhancing energy transduction efficiency. By further exploring energy transfer between proteins and studying different organisms, researchers can uncover more secrets about photosynthesis and potentially revolutionize energy conversion technologies.

Chemistry

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