title: Evaluation of a biohybrid photoelectrochemical cell employing the purple bacterial reaction centre as a biosensor for herbicides.
abstract: The Rhodobacter sphaeroides reaction centre is a relatively robust and tractable membrane protein that has potential for exploitation in technological applications, including biohybrid devices for photovoltaics and biosensing. This report assessed the usefulness of the photocurrent generated by this reaction centre adhered to a small working electrode as the basis for a biosensor for classes of herbicides used extensively for the control of weeds in major agricultural crops. Photocurrent generation was inhibited in a concentration-dependent manner by the triazides atrazine and terbutryn, but not by nitrile or phenylurea herbicides. Measurements of the effects of these herbicides on the kinetics of charge recombination in photo-oxidised reaction centres in solution showed the same selectivity of response. Titrations of reaction centre photocurrents yielded half maximal inhibitory concentrations of 208nM and 2.1µM for terbutryn and atrazine, respectively, with limits of detection estimated at around 8nM and 50nM, respectively. Photocurrent attenuation provided a direct measure of herbicide concentration, with no need for model-dependent kinetic analysis of the signal used for detection or the use of prohibitively complex instrumentation, and prospects for the use of protein engineering to develop the sensitivity and selectivity of herbicide binding by the Rba. sphaeroides reaction centre are discussed.
authors.affiliation: School of Biochemistry, Medical Sciences Building, University of Bristol, University Walk, Bristol BS8 1TD, United Kingdom. Electronic address: D.Swainsbury@bristol.ac.uk.
authors.forename: David J K
authors.initials: DJ
authors.lastname: Swainsbury
authors.affiliation: Division of Physics and Astronomy, Department of Biophysics, VU University Amsterdam, De Boelelaan 1081, Amsterdam 1081 HV, The Netherlands. Electronic address: v.m.friebe@vu.nl.
authors.forename: Vincent M
authors.initials: VM
authors.lastname: Friebe
authors.affiliation: Division of Physics and Astronomy, Department of Biophysics, VU University Amsterdam, De Boelelaan 1081, Amsterdam 1081 HV, The Netherlands. Electronic address: r.n.frese@vu.nl.
authors.forename: Raoul N
authors.initials: RN
authors.lastname: Frese
authors.affiliation: School of Biochemistry, Medical Sciences Building, University of Bristol, University Walk, Bristol BS8 1TD, United Kingdom. Electronic address: m.r.jones@bristol.ac.uk.
authors.forename: Michael R
authors.initials: MR
authors.lastname: Jones
mesh_terms: D015374:Biosensing Techniques / Q000295:instrumentation*; D004563:Electrochemistry / Q000295:instrumentation*; D004867:Equipment Design; D019544:Equipment Failure Analysis; D006540:Herbicides / Q000032:analysis* / Q000737:chemistry; D008027:Light; D010777:Photochemistry / Q000295:instrumentation*; D045322:Photosynthetic Reaction Center Complex Proteins / Q000737:chemistry* / Q000528:radiation effects; D012242:Rhodobacter sphaeroides / Q000737:chemistry*; D014227:Triazines / Q000032:analysis* / Q000737:chemistry
chemical_list: D006540:Herbicides; D045322:Photosynthetic Reaction Center Complex Proteins; D014227:Triazines
keywords: Atrazine; Biosensor; Herbicide; Photocurrent; Photovoltaics; Reaction centre