Shedding Light


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(l-r) Iris Margalit, Dr. Ilit Cohen-Ofri, Dr. Joanna Grzyb, Dr. Dror Noy and Dr. Jebasinga Tennyson. Custom-built proteins

If “older is wiser,” then photosynthetic organisms, including plants, algae and various types of bacteria, must be wise indeed – at least when it comes to efficiently converting sunlight, water and carbon dioxide into sugars and other energy-rich molecules to fuel their biological activities.
Dr. Dror Noy, a plant scientist at the Weizmann Institute of Science, has plans to harness the ancient art of photosynthesis – mastered by organisms over millions of years – in new ways, to create clean and renewable alternatives to fossil fuels.
Using natural biological building blocks and the living photosynthetic apparatus as a starting “blueprint,” Noy intends to design and engineer functional solar energy conversion systems. The building blocks of these systems will be small, robust protein scaffolds known as maquettes, which were first developed by the University of Pennsylvania group Noy joined as a postdoctoral student. Maquettes are assembled from natural amino acids, but their design is different from any natural protein. Now Noy hopes to customize new types of maquettes, endowing them with pigments and other cofactors found in the photosynthetic apparatus.
Noy focuses on the initial stages of photosynthesis – the so-called light reactions. In protein complexes known as photosystems, the pigments in leaves or organisms absorb sunlight and transfer this light energy to a nearby reaction center. In the reaction centers, this energy causes the release of electrons, which then pass through a chain of reactions, producing chemical energy for further conversion into oxygen and carbohydrates in the final stages of photosynthesis. To return the lost electrons to the photosystems, new electrons are split from water molecules, freeing up oxygen molecules and positively charged protons.
“Although the process of photosynthesis is highly efficient for photosynthetic organisms, they store their converted energy in sugars that are poor fuel products,” explains Noy. He is trying to sift through the evolutionary “noise” of functions that have been lost, gained or duplicated over the aeons to identify the minimal requirements necessary for photosynthesis, and to build maquettes that will harness its energy for making better fuels.
As for the design, Noy and his group have an initial advantage: The photosynthetic apparatus is one of the best-characterized systems in the field of biology. The distance between pigments has been measured down to the near-atomic scale, and the dynamics of energy transfer down to fractions of picoseconds. The precise 3-D arrangement of pigments, however, is critical for the process to work efficiently, and in practice, manipulating structures at such small scales has proven difficult. The photosystem proteins provide the scaffold that maintains this spatial organization, and this, in turn, is determined by the sequence of their amino acids. Thus the key to success lies in finding the right amino acid sequence for each protein – an incredible challenge, given that there are millions of possible combinations.
Yet Noy’s group is starting to make headway. Using genetic engineering, they “program” the bacterium E. coli to produce new proteins with specifically designed amino acid sequences for assembling pigments and cofactors into simpler analogs of natural photosynthetic proteins. By iteratively testing and redesigning the new proteins, they are beginning to understand how sequences of amino acids translate into the required 3-D structures. They have already managed to build prototype maquettes containing a few light-harvesting pigments that are able to carry out some reactions, and they are hoping to further tweak the design to contain many more pigments. Another group is working on ways to tap into the process of photosynthesis at the “junction” where light energy can be diverted to converting protons into hydrogen molecules that could be used for fuel.
Noy: “These studies will hopefully open the way to the design of stand-alone energy conversion as well as such light-activated devices as protein-based solar cells, which make use of biological elements in a non-biological context. Insights gained from this research will also advance our understanding of the way plants harvest and store solar energy. This understanding should make it possible to introduce custom-built proteins into plants to increase the production of such plant-based fuels as biodiesel or ethanol, as well as enabling the production by plants of such ‘inorganic’ fuels as hydrogen.”
Right: Actual molecular structures of natural protein complexes:a photosynthetic reaction center (top) and a cytochrome. Left: Artificial proteins that are analogous to the natural ones, with details of their “assistant molecules” (far left)














Getting the Green Light

Born in Tel Aviv, in 1967, Dr. Dror Noy served in the Israel Air Force, reaching the rank of lieutenant. After receiving a B.Sc. in chemistry from Tel Aviv University in 1992, he pursued his M.Sc. and Ph.D. studies at the Weizmann Institute under the guidance of Prof. Avigdor Scherz, then went on to postdoctoral studies at the University of Pennsylvania in the laboratory of Prof. P. Leslie Dutton. Upon returning to Israel in 2004, he worked as a post-doctoral fellow and later as a staff scientist with Prof. Irit Sagi in the Weizmann Institute’s Structural Biology Department. “Although I focused on different aspects of research at each stage of my studies, the repertoire of scientific and technical knowledge thus gained has allowed me to integrate them into a new line of research.” Noy joined the Plant Sciences Department as a senior scientist in 2007.

Noy is a recipient of the 2006 Career Development Award from the internationally based Human Frontier Science Program. He is married and is the father of four children, aged 10, 7 and twins of 3½ years.

Dr. Dror Noy’s research is supported by the Chais Family Fellows Program for New Scientists; the Koret Foundation; the estate of Louise G. Perlmuter, Brookline, MA; Ilan Gluzman, Secaucus, NJ; and Dr. and Mrs. Robert Zaitlin, Los Angeles, CA.