Competing charge transfer pathways at the photosystem II-electrode interface.

The integration of the water-oxidation enzyme photosystem II (PSII) into electrodes allows the electrons extracted from water oxidation to be harnessed for enzyme characterization and to drive novel endergonic reactions. However, PSII continues to underperform in integrated photoelectrochemical systems despite extensive optimization efforts. Here we carried out protein-film photoelectrochemistry using spinach and Thermosynechococcus elongatus PSII, and we identified a competing charge transfer pathway at the enzyme-electrode interface that short-circuits the known water-oxidation pathway. This undesirable pathway occurs as a result of photo-induced O2 reduction occurring at the chlorophyll pigments and is promoted by the embedment of PSII in an electron-conducting fullerene matrix, a common strategy for enzyme immobilization. Anaerobicity helps to recover the PSII photoresponse and unmasks the onset potentials relating to the QA/QB charge transfer process. These findings impart a fuller understanding of the charge transfer pathways within PSII and at photosystem-electrode interfaces, which will lead to more rational design of pigment-containing photoelectrodes in general.This work was supported by the U.K. Engineering and Physical Sciences Research Council (EP/H00338X/2 to E. Reisner), the U.K. Biology and Biotechnological Sciences Research Council (BB/K010220/1 to E. Reisner), a Marie Curie International Incoming Fellowship (PIIF-GA-2012-328085 RPSII to J.J.Z.). N.P. was supported by the Winton Fund for the Physics of Sustainability. E. Romero. and R.v.G. were supported by the VU University Amsterdam, the Laserlab-Europe Consortium, the TOP grant (700.58.305) from the Foundation of Chemical Sciences part of NWO, the Advanced Investigator grant (267333, PHOTPROT) from the European Research Council, and the EU FP7 project PAPETS (GA 323901). R.v.G. gratefully acknowledges his `Academy Professor' grant from the Royal Netherlands Academy of Arts and Sciences (KNAW). We would also like to thank Miss Katharina Brinkert and Prof A. William Rutherford for a sample of T. elongatus PSII, and H. v. Roon for preparation of the spinach PSII samples

Financial doping and financial fair play in European Club football competitions

Addresses the emerging area of manipulation in professional sports by bringing a collection of original contributions together in one volume for the first time Provides an interdisciplinary approach, combining economic, business administrative and legal issues, that enables a complete overview for any scholar interested in the global economics of, and manipulation of sport, in general Presents contributions from world class scholars that are well known in their area

X-ray fluorescence analysis of metal distributions in cryogenic biological samples using large-acceptance-angle SDD detection and continuous scanning at the Hard X-ray Micro/Nano-Probe beamline P06 at PETRA III

A new Rococo 2 X-ray fluorescence detector was implemented into the cryogenic sample environment at the Hard X-ray Micro/Nano-Probe beamline P06 at PETRA III, DESY, Hamburg, Germany. A four sensor-field cloverleaf design is optimized for the investigation of planar samples and operates in a backscattering geometry resulting in a large solid angle of up to 1.1 steradian. The detector, coupled with the Xspress 3 pulse processor, enables measurements at high count rates of up to 106 counts per second per sensor. The measured energy resolution of ∼129 eV (Mn Kα at 10000 counts s−1) is only minimally impaired at the highest count rates. The resulting high detection sensitivity allows for an accurate determination of trace element distributions such as in thin frozen hydrated biological specimens. First proof-of-principle measurements using continuous-movement 2D scans of frozen hydrated HeLa cells as a model system are reported to demonstrate the potential of the new detection system

A Multiperspective Approach to Solvent Regulation of Enzymatic Activity: HMG‐CoA Reductase

3‐Hydroxy‐3‐methylglutaryl–coenzyme A (HMG‐CoA) reductase was investigated in different organic cosolvents by means of kinetic and calorimetric measurements, molecular dynamics simulations, and small‐angle X‐ray scattering. The combined experimental and theoretical techniques were essential to complement each other's limitations in the investigation of the complex interaction pattern between the enzyme, different solvent types, and concentrations. In this way, the underlying mechanisms for the loss of enzyme activity in different water‐miscible solvents could be elucidated. These include direct inhibitory effects onto the active center and structural distortions

In Cellulo Analysis of Huntingtin Inclusion Bodies by Cryogenic Nanoprobe SAXS

Huntington's disease (HD) is one of nine neurodegenerative disorders associated with an extension of polyglutamine (polyQ) in proteins. In HD, the polyQ tract in the huntingtin protein is extended beyond a threshold of 38 amino acids leading to the formation of amyloidal structures in the cytoplasm and nucleus. We investigated here the structure of Htt (Huntingtin) amyloid fibrils in cellulo with nanoprobe small angle X-ray scattering. As these measurements were performed under cryogenic conditions, the information is obtained on the aggregates in their natural, hydrated environment without the need of staining and chemical fixation. We also could show the presence of oligomer structures not visible in fluorescence microscopy. Structural information on repetitive units inside of Htt inclusion bodies was determined from the SAXS data and compared to electron microscopy images. The results suggest that nanoprobe cryo-SAXS can serve as powerful tool to investigate the kinetics of amyloid aggregate formation inside cells and to understand how fibril formation can be influenced by drugs and other external stimuli