Chemical Biology

UNDERSTANDING THE INEFFICIENCIES OF PHOTOSYNTHESIS Plants and photosynthetic bacteria capture light energy and convert it into stored chemical energy, which is used to drive reactions that convert water and carbon dioxide into the materials that almost all organisms on earth need to live and grow. Surprisingly the detailed mechanisms are not well understood. We employ a combination of spectroscopic methods and computational modelling to reveal pathways, mechanisms and rate limiting steps that control the light dependent and dark Photosynthetic reactions.

DARK PHOTOSYNTHETIC REACTIONS Inside plant cells, a network of enzymes creates organic carbon from the CO2 in the air and these reactions are strikingly inefficient. Typical enzymes can process ~1000 molecules per sec, but one of the enzymes, Rubisco, involved in the network, fixes only about 3 CO2 molecules per sec. An understanding of Rubisco''s inefficiency could clearly have significant impact, as it may provide a route to achieving profound improvements in photosynthetic efficiencies, through manipulating Rubisco in the chloroplast of higher plants. This requires a range of quantitative approaches if the delivery of selected or engineered traits is to be a viable proposition. Prof David Klug, Prof Martin Parry and Dr Laura Barter have students working on quantitative proteomics, metabolomics, transcriptomics all allied with modelling and calculation to probe the Rubisco interactome and to investigate the regulatory networks controlling photosynthetic efficiency. The aim being to determine how these interactions control the up and down regulation of the enzyme.

PHOTOSYNTHETIC WATER SPLITTING The chloroplast houses a membrane which contains a chain of complexes involved with the intake of light energy and the transfer of charge across the membrane. This separation of charge is a method of storing energy and can be thought of as being like a battery, and therefore these complexes are the power-house of the organism. It is striking that the plant is able to store enough energy, by creating stable intermediate states, to drive the energy demanding reactions that splits water and release oxygen as a by-product. These reactions occur over timescales that cover more than fifteen orders of magnitude. A range of spectroscopic methods in combination with modelling allow us to probe the quantitative structure function relationship. Single molecule spectroscopy has also been employed to probe properties of Photosynthetic complexes which are inaccessible in any other way. In particular the work has focused on the heterogeneity of the process and the dynamics associated with steps hidden by rate limiting steps in an ensemble experiment.

TWO-DIMENSIONAL INFRARED SPECTROSCOPY Current research includes the use of an optical analogue of 2D NMR to measure vibration-vibration coupling with the aim of probing the structure of enzyme active sites. Dr Laura Barter is particularly focusing on the water-splitting chemistry in Photosynthesis in collaboration with Prof David Klug and Dr Ian Gould in the Chemistry department.

O'Donnelly K, Zhao G, Patel P, Butt MS, Mak LH, Kretschmer S, Woscholski R, Barter LMCet al., 2014, Isolation and kinetic characterisation of hydrophobically distinct populations of form I Rubisco, PLANT METHODS, Vol: 10, ISSN: 1746-4811 Author Web Link Cite JOURNAL ARTICLE Miller D, Booth PJ, Seddon JM, Templer RH, Law RV, Woscholski R, Ces O, Barter LMCet al., 2013, Protocell design through modular compartmentalization, JOURNAL OF THE ROYAL SOCIETY INTERFACE, Vol: 10, ISSN: 1742-5689 Author Web Link Cite JOURNAL ARTICLE Charalambous K, Booth PJ, Woscholski R, Seddon JM, Templer RH, Law RV, Barter LMC, Ces Oet al., 2012, Engineering de Novo Membrane-Mediated Protein-Protein Communication Networks, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, Vol: 134, Pages: 5746-5749, ISSN: 0002-7863 Author Web Link Cite CITATIONS: 12 JOURNAL ARTICLE Wormit A, Butt SM, Chairam I, McKenna JF, Nunes-Nesi A, Kjaer L, O'Donnelly K, Fernie AR, Woscholski R, Barter MCL, Hamann Tet al., 2012, Osmosensitive Changes of Carbohydrate Metabolism in Response to Cellulose Biosynthesis Inhibition, PLANT PHYSIOLOGY, Vol: 159, Pages: 105-117, ISSN: 0032-0889 Author Web Link Cite CITATIONS: 10 JOURNAL ARTICLE Fournier F, Gardner EM, Guo R, Donaldson PM, Barter LMC, Palmer DJ, Barnett CJ, Willison KR, Gould IR, Klug DRet al., 2008, Optical fingerprinting of peptides using two-dimensional infrared spectroscopy: Proof of principle, ANALYTICAL BIOCHEMISTRY, Vol: 374, Pages: 358-365, ISSN: 0003-2697 Author Web Link Cite CITATIONS: 17 JOURNAL ARTICLE Donaldson PM, Guo R, Fournier F, Gardner EM, Barter LMC, Barnett CJ, Gould IR, Klug DR, Palmer DJ, Willison KRet al., 2007, Direct identification and decongestion of Fermi resonances by control of pulse time ordering in two-dimensional IR spectroscopy (vol 127, art no. 114513, 2007), JOURNAL OF CHEMICAL PHYSICS, Vol: 127, ISSN: 0021-9606 Author Web Link Cite JOURNAL ARTICLE Donaldson PM, Guo R, Fournier F, Gardner EM, Barter LMC, Barnett CJ, Gould IR, Klug DR, Palmer DJ, Willison KRet al., 2007, Direct identification and decongestion of Fermi resonances by control of pulse time ordering in two-dimensional IR spectroscopy, JOURNAL OF CHEMICAL PHYSICS, Vol: 127, ISSN: 0021-9606 Author Web Link Cite CITATIONS: 18 JOURNAL ARTICLE Barter LMC, Klug DR, Woscholski R, 2006, Does history repeat itself? The emergence of a new discipline, ACS CHEMICAL BIOLOGY, Vol: 1, Pages: 737-740, ISSN: 1554-8929 Author Web Link Cite CITATIONS: 1 JOURNAL ARTICLE Barter LMC, Klug DR, 2005, A unified picture of energy and electron transfer in primary photosynthesis, CHEMICAL PHYSICS, Vol: 319, Pages: 308-315, ISSN: 0301-0104 Author Web Link Cite CITATIONS: 2 JOURNAL ARTICLE Barter LMC, van Grondelle R, Klug DR, 2005, Energy trapping and equilibration: a balance of regulation and efficiency, Photosystem II: the light-driven water: plastoquinone oxidoreductase, Editors: Wydrzynski, Satoh, Publisher: Springer, Pages: 491-514, ISBN: 9781402042492

Barter LMC, Durrant JR, Klug DR, 2003, A quantitative structure-function relationship for the Photosystern II reaction center: Supermolecular behavior in natural photosynthesis, PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, Vol: 100, Pages: 946-951, ISSN: 0027-8424