School of Chemistry Research
School of Chemistry: Research Highlights
The School of Chemistry is one of the largest research and teaching chemistry departments in the UK and has a strong portfolio of research across the whole of the discipline from modelling gas phase reactions of simple molecules to the chemistry of proteins. The highlights below give a flavour of the breadth of the dynamic and ground-breaking research achieved in recent years.
1 Materials chemistry
Materials chemistry encompasses colloids, liquid crystals inorganic nanostructures for nanoplasmonics, template-directed synthesis of inorganic carbonate/phosphates and metallic architectures, protein-mediated biomimetic biomineralization and the development of a rational design protocol for engineering the morphology of self-assembling peptide nanofilaments.
Professor Stephen Mann and Dr Adam Perriman reported the first example of a liquid protein (Angew. Chem. Int. Ed. 2009 48, 6242). Functionalising the surface of the iron storage protein ferritin with protonated amines provides an electrostatic binding site for negatively charged polymer surfactant, creating proteins that bristle with long hairs. This composite melts at 30°C to a liquid crystal and at 50°C, the liquid appears to act like an ordinary fluid. The “liquid protein” is more highly concentrated than a protein dissolved in water which offers the possibility of being able to administer higher doses of medically useful proteins. Alginate, a seaweed-derived biopolymer controls the growth of Y124 nanoparticles to produce the first ever single crystal high-temperature superconductor nanowires where the biopolymer directs the reaction and subsequent morphology of the superconductor.(Hall and Mann Adv. Mat. 2008, 20, 1782).
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Simulated image of a ligand-passivated ferritin protein |
YBa2Cu4O8 (Y124) nanowires templated by an alginate biopolymer |
Professor Ian Manners' group have developed a new concept for micelle formation via self-assembly termed crystallization-driven living self-assembly (Science 2007, 317, 644; Nature Materials 2009, 8, 144). This involves controlled formation of micelles from the termini of cylindrical micelles with a crystalline core and allows unprecedented control of micelle architectures which will have applications in liquid crystals, emissive heterojunctions, and photovoltaic materials.
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Scheme for formation of a segmented triblock comicelle |
2 Synthesis
Synthesis underpins many research themes. Within organic synthesis, Aggarwal (Nature, 2008, 456, 778-782) can produce molecules containing asymmetric quaternary stereogenic centres (e.g. tertiary alcohols) using boron reactivity. All reactions occur with complete inversion of stereochemistry when boranes are employed but complete retention occurs when boronic esters are used providing a neat, versatile and unique complementary relationship.
3 Biological chemistry
Biological chemistry from the polyketides group (Simpson, Cox, Willis, Crosby, Crump) has established the programming mechanisms in tenellin synthase where a single gene cluster produces a library of compounds. In bacteria, the group have applied detailed physical and analytical methods to the dissociated actinorhodin polyketide synthase to show for the first time how these complex biomachines coordinate biosynthetic reactions (Nature,1999, 401, 502).
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The biosynthetic potential of the tenellin biosynthetic proteins (top); Part of the 1H 15N 2D NMR spectrum of acyl carrier protein (pink and green), the central substrate of polyketide and fatty acid biosynthesis (malonyl transferase is shown in blue and red) (bottom). |
4 Computational and theoretical chemistry
This research explores key aspects of enzyme mechanism. Using molecular simulations (e.g. combined quantum mechanics/molecular mechanics (QM/MM) methods), Professor Adrian Mulholland (and collaborators from Manchester; Science 2006, 312, 237) deduced the atomic-level description for tryptamine oxidation by aromatic amine dehydrogenase. The simulations demonstrated, crucially, that tunnelling is promoted only by short-range molecular motion at the active site and the controversial notion that long-range flexing of the rest of the protein molecule plays a direct role was been firmly challenged. This work has profoundly important implications for the understanding the activity, dynamics and evolution of biological catalysts.
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QM/MM calculation on an enzyme(left); Active site of aromatic amine dehydrogenase, showing the groups involved in the tunnelling reaction (right). |
5 Dynamics and structure of gas-phase molecules
Dynamics and structure of gas-phase molecules enables chemical reactions to be studied that take place on incredibly short femto to picoseconds (10-15 – 10-12 s) timescales. Using laser ionization and 3D velocity imaging to capture the dynamic behaviour of reaction products, Ashfold and Orr-Ewing (J. Phys. Chem. A, 2005, 109, 11093) have studied fundamental process (e.g. Cl + CH3F → HCl + CH2F) and demonstrated that the product HCl rotational energy provided the probe needed to study incipient hydrogen bonding after the reaction transition state.
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Calculated energies of reactants (left), products (right), weakly bound complexes, and the transition state for the reaction Cl + CH3F HCl + CH2F. |
Velocity map image of the HCl (v=0,J=1) products of the reaction of Cl atoms with neopentane. The coloured peak in the upper region corresponds to products forward scattered in the CM frame. |
6 Atmospheric chemistry
Atmospheric chemistry spans innovations in laboratory studies, advances in field measurements, and computer modelling. Aerosols and clouds play a crucial role in regional and global climate change, although their impact is not well quantified. Professor Jonathan Reid has shown that using tightly focussing light (optical tweezers), single airborne particles can be captured and manipulated. Similarly, arrays of particles can be positioned, rotated and coagulated with real-time control; the movie/image shows this with an array of water droplets, each 5×10-6 m in diameter (Chem. Soc. Rev. 2008, 37, 756-769). This has provided insights to size, composition and kinetic behaviour of atmospheric aerosol, all of which are important in the understanding of clouds and pollution.
7 Analytical chemistry
Advances in this field encompass diatomic to macromolecular scales. Environmental and climate change issues are especially important. Researchers at the Bristol Biogeochemistry Research Centre have demonstrated that the key biochemical components associated with previously unculturable soil methanotrophic bacteria – key organisms because they constitute the terrestrial methane sink – can be probed using 13C and 15N. State of the art gas chromatography-combustion-isotope ratio mass spectrometry targets phospholipid fatty acids, hopanoids, protein-derived amino acids, carbohydrates, and for the first time a link has been established between the methane oxidation capacity of soils to the methanotrophic bacterial population (Nature, 2000, 405, 175; Envir. Microbio. 2008, 10, 1917).
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