Faculty of Biological Sciences

Dr Lars Jeuken

PhD 2001
Reader in Biophysics
School of Biomedical Sciences

Contact:  Garstang 10.140, +44(0) 113 34 33829, email address for  

You can read more about Dr Jeuken's interests here:
http://www.fbs.leeds.ac.uk/jeukengroup/


Research Interests

Redox-active membrane proteins, biological electron transfer

Our aim is to to control the interaction between biological macromolecules and inorganic 'solid' surfaces. The interaction between biomolecules and surfaces is key to many assays, but often not controlled. Take for instance an ELISA assay; Biomolecules are 'randomly' physisorbed on plastic 96-well plates without any control on the orientation of these molecules. However, biomolecules for which the epitope is orientated towards the plastic surfaces might not interact with antibodies. The interaction between solid, inorganic surfaces is particular important for membrane proteins, where the hydrophobic regions of the protein will change the way the proteins interacts with its environment. Vice versa, the influence of inorganic surfaces on proteins might be more pronounces for membrane proteins, denaturing the protein or otherwise influencing the function of the membrane proteins. Membrane proteins, in general, are more difficult to study due to their amphiphatic nature. Many membrane enzymes are studied in detergent solutions or only hydrophilic subunits are used (i.e., removing the integral membrane subunits). However, the lipid membrane has an important influence on the proteins that reside in them and experimental techniques that do not include the membrane are thus limited. When studying membrane proteins with assays that include their adsorption to a solid surface, one would ideally like to retain a native-like lipid environment. Important examples are enzymes that interact with the hydrophobic quinone pool (like ubiquinol oxidase). Other examples include 'membrane-bound hydrogenases', where the majority of studies are performed on the two hydrophilic subunits, without the third transmembrane quinone-converting subunit.

Within Leeds

Our research on membrane proteins is facilitated by colleagues in the University wide Integrative Membrane Biology group.

Our work is highly interdisciplinary in nature, which is greatly facilitated by various collaboration within the Structural Molecular Biology group.

 

Current Projects

Redox-active membrane enzymes

We have modified electrodes with lipid membranes in which the membranes either adopt a planar geometry (see Figure) or liposomes are immobilised intact on the surface. This allows us to study redox-active membrane proteins in their native environment. We use these systems to study the catalytic activity and proton pumping activity of an ubiquinol oxidase from E. coli, cytochrome bo3. Currently, we have three projects in this area. 

Single-enzyme studies of a proton pump

By modifying the electrode surfaces, membrane vesicles can be adsorbed on the surface that stay intact. By loading these vesicles with fluorescent probes we can simultaneously control the activity of the ubiquinol oxidase, cytochrome bo3 (using electrochemical methods) and measure its proton pumping activity (see also the ERC project 'MEME'). Currently, this experimental setup is used to study the proton pumping activity of a heme-copper oxidase at the single-enzyme level.

Respiration in Shewanella oneidensis MR-1

S. oneidensis is a proteobacterium and gram-negative facultative-anaerobe that has a remarkably diverse multicomponent and branched electron transport chain, making it an important model organism for bioreactor, bioengineering and bioremediation studies. Its respiratory plasticity allows S. oneidensis to link proton translocation to the reduction of a wide variety of electron acceptors such as O2, fumarate, nitrate, arsenate, DMSO, TMAO, Fe(III), Mn(IV), Cr(VI), V(V) oxides and various forms of other carbonaceous and sulfur-based compounds. During anearobic respiration, the quinone pool is oxidised by a single enzyme, CymA, which transfers the electrons to one of the many terminal reducases. We have used our membrane-modified electrodes to study QH2/Q oxidoreductases activity of CymA and its partners proteins in the periplasm (see Figure). S. oneidensis is also able to respire on electrode surfaces, transferring electrons extracellularly via MtrCAB, which span the periplasm and outer membrane. Electron transfer throught the MtrCAB complex and CymA is characterised in our lab using the membrane modified electrodes.

Membrane-bound hydrogenase (MBH)

MBHs are hydrogen/proton converting enzymes that donate to or extract electrons from the quinol pool in the lipid membrane. These enzymes are extensively studied using electrochemical methods, but invariably only the two hydrophilic subunits are used, omitting a third membrane subunit that interacts with the quinone pool. In this project, the whole heterotrimeric MBH is placed in the planar lipid membrane on the electrode surface (see image above) and the activity and other properties (such is deactivation) are characterised using electrochemical methods. 

Interactions between nanoparticles/nanowires and cell membranes

Exploiting Transmembrane Cytochromes for Solar Energy Conversion

There is vast potential for renewable fuel and electricity generation through the photochemical conversion of solar to chemical energy. We wish to tap into what is a largely unused power supply and develop the basic principles for a novel biotechnology that will harness solar energy using a biological synthetic approach, in which a bacterial respiratory machinery is coupled to inorganic photosensitisers. Our biosynthetic approach is inspired by plant photosynthesis where solar energy is absorbed by the special pair of chlorophylls (the photosensitisers) and, ultimately, converted to chemical energy. Our ambition is to overcome the major drawbacks of most artificial homogenous photosynthetic systems: a short-lived charge separated state, which is due to the failure to spatially decouple the reductive and the oxidative sites required to sustain charge separation. In plant photosynthesis, the latter is achieved by rapid transmembrane electron transfer. In this project, which is a collaboration with the Universities of East Anglia and Cambridge, transmembrane charge separation is achieved by exploiting the membrane-spanning electron-transfer conduits of the microbe Shewanella oneidensis MR-1, where the cytochrome conduits play an integral part of their ability to respire on inorganic minerals. As a proof of principle, we aim to photocatalyse the reduction of protons to hydrogen, using both inorganic (platinum) and biological (hydrogenase) catalysts. The resulting photocatalyst adopts the principles of natural photosynthesis (light harvesting, charge separation and catalysis) in a device that spatially separates the sites of photoexcitation and oxidation to that from reduction (hydrogen evolution). The image illustrates a cytochrome condiut protein (MtrF) coupled to a inorganic photosensitiser (TiO2). The assembly is adorbed on a gold electrode and electrochemistry is used to characterise the electron transfer rates between (photoexcited) TiO2 and MtrF.

Microbial fuel cells

Recently, an intense interest has emerged in microorganisms that generate electrical current from organic matter in microbial fuel cells (MFCs). MFCs have the ability to generate a clean and renewable energy and to generate continuous power in specialised environments like the bottom of the sea bed or the human body. However, one of the greatest bottlenecks in MFC development is their limited power output, which is still insufficient to drive most electronic devices in society. The limitation in power output is mostly due to the slow rate of electron transfer from the microbes to the anode of the MFC. Using our technology, we aim to 'electrically' connect bacteria in biofilms to the electrode (anode) via nanowires and thereby enhancing the electron transfer rate between microbe and the electrode, and thus the power output of the MFC. To analyse the interactions between Shewanella bacteria and chemically-modified nanoparticles, we make use of quantum dots, which are semi-conducting nanoparticulates that are strongly fluorescent and thus easy to image (see Figure).

Spherical-supported bilayer lipid membranes (ssBLM)

Nanoparticles can be relatively easily extracted from (aqueous) solution via (low-speed) centrifugation or, in the case of (para)magnetic particles, with a magnet. In our lab we coat silica nanoparticles with lipid bilayers. By including membrane proteins in the membrane-coated nanoparticles, we create a technological platform in which the membrane proteins can be easily extracted. Sponsored by MedImmune, we are currently exploring this platform for applications in phage display, raising antibody or antibody mimetic proteins against membrane proteins.

Nanotoxicology and nanomedicine

The toxic effects of nanomaterials are poorly understood and their effects on aquatic wildlife are largely unknown. In the absence of such basic toxicological information, it is difficult to set environmental quality standards or perform risk assessments for these materials. In a project funded by the EU, ENNSATOX, this crucial uncertainty was addressed by seeking to relate the structure and functionality of well-known nanoparticles (silica or ZnO) of varying morphology to its biological activity at the membrane level. Our lab focuses particularly on whether nanomaterials are able to induce damage, either mechanically or via the production of radiacal species, and whether nanoparticles are able to passively pass a cell membrane, thereby potentially inducing toxic effect in the cytoplasm. Alterantively, by creating nanomaterials that can passively pass the membrane without too many toxic concequences, a drug delivery system can be designed.

 

Faculty Research and Innovation



Studentship information

Undergraduate project topics:

  • 1) Nanotoxicology (group project)
  • 2) Transport of metabolites and drugs across the cell membrane
  • 3) Artificial photosynthesis

Postgraduate studentship areas:

  • We have various funded PhD positions available throughout the year.

See also:

Modules managed

BIOL2210 - Biological Membranes and Cell Signalling
BIOL5262M - Molecular Diagnostics and Drug Delivery

Modules taught

BIOC1301 - Introductory Integrated Biochemistry: the Molecules and Processes of Life
BIOC2303 - Intermediate Biochemistry: Skills
BIOL2210/BIOC2301 - Integrated Biochemistry/Biological Membranes
BIOL3398 - Research Tools and Applications
BIOL3399 - Extended Research Project Preparation
BIOL5262M - Molecular Diagnostics and Drug Delivery
BIOL5390M - Bioscience MSc Research Project
BIOW5906X - Theory, computation and bioinformatics
BMSC1103 - Basic Laboratory and Scientific Skills
BMSC1213 - Basic Laboratory and Scientific Skills 2
BMSC2229 - Experimental Skills in Medical Sciences
BMSC3301 - Research Project in Biomedical Sciences
BMSC3399 - Extended Research Project Preparation

Centre membership: The Astbury Centre for Structural Molecular Biology

Group Leader Dr Lars Jeuken  (Reader in Biophysics)

Redox-active membrane proteins, biological electron transfer 

Miss Hope Adamson  (Research Fellow)

Dr George Heath  (Research Fellow)

Mrs Honglin Rong  (Research Technician)


Postgraduates

Matthias Gantner (Primary supervisor) 50% FTE
Theodoros Laftsoglou (Primary supervisor) 80% FTE
Joseph Oram (Primary supervisor) 90% FTE
Anna Stikane (Primary supervisor) 67% FTE
Vlad Vasilca (Primary supervisor) 75% FTE
Anna Wroblewska-Wolna (Primary supervisor) 67% FTE
Ruth Craven (Co-supervisor) 33% FTE
Ashley Hancock (Co-supervisor) 10% FTE
Andrew Harvie (Co-supervisor) 20% FTE