Image_1_A prospective investigation of the effects of soccer heading on cognitive and sensorimotor performances in semi-professional female players.jpg

IntroductionRepetitive head impacts (RHI) from routine soccer (football) heading have been suggested to contribute to the long-term development of neurodegenerative disorders. However, scientific evidence concerning the actual risk of these RHI on brain health remains inconclusive. Moreover, female athletes—despite a presumably increased vulnerability toward the effects of RHI—are largely underrepresented in previous approaches. Therefore, our aim was to prospectively investigate the effects of heading on cognitive and sensorimotor performances, health perception, and concussion symptoms in semi-professional female soccer players.MethodsAn extensive test battery was used to assess cognitive and sensorimotor performances as well as health status (SF-36) and concussion symptoms (SCAT3) of a total of 27 female soccer players (22.2 ± 4.2 years) and 15 control subjects (23.2 ± 3.0 years) before and after one-and-a-half years. Throughout this period, soccer players’ heading exposure was determined using video analysis.ResultsSubgroup comparisons (control [n = 12], low exposure [n = 7], high exposure [n = 8]) showed no time-dependent differences in SF-36 or SCAT3 scores. Similarly, across most behavioral tests, soccer players’ performances evolved equally or more favorably as compared to the control subjects. However, there were significant effects pointing toward slightly negative consequences of heading on aspects of fine motor control (p = 0.001), which were confirmed by correlation and multiple regression analyses. The latter, further, yielded indications for a relationship between heading exposure and negative alterations in postural control (p = 0.002).DiscussionOur findings do not provide evidence for negative effects of soccer heading on female players’ health perception, concussion symptoms, and cognitive performances over the course of one-and-a-half years. However, we found subtle negative alterations in fine motor and postural control that could be attributed to heading exposure. Other factors, like the number of previous head injuries, were not linked to the observed changes. Given the reduction of our initial sample size due to player fluctuation, the results need to be interpreted with caution and validated in larger-scale studies. These should not only focus on cognitive outcomes but also consider sensorimotor changes as a result of RHI from soccer heading.</p

Nitric Oxide-Induced Formation of the S_-₂ State in the Oxygen-Evolving Complex of Photosystem II from <i>Synechococcus elongatus</i>^†

In spinach photosystem II (PSII) membranes, the tetranuclear manganese cluster of the oxygen-evolving complex (OEC) can be reduced by incubation with nitric oxide at −30 °C to a state which is characterized by an Mn2(II, III) EPR multiline signal [Sarrou, J., Ioannidis, N., Deligiannakis, Y., and Petrouleas, V. (1998) Biochemistry 37, 3581−3587]. This state was recently assigned to the S-2 state of the OEC [Schansker, G., Goussias, C., Petrouleas, V., and Rutherford, A. W. (2002) Biochemistry 41, 3057−3064]. On the basis of EPR spectroscopy and flash-induced oxygen evolution patterns, we show that a similar reduction process takes place in PSII samples of the thermophilic cyanobacterium Synechococcus elongatus at both −30 and 0 °C. An EPR multiline signal, very similar but not identical to that of the S-2 state in spinach, was obtained with monomeric and dimeric PSII core complexes from S. elongatus only after incubation at −30 °C. The assignment of this EPR multiline signal to the S-2 state is corroborated by measurements of flash-induced oxygen evolution patterns and detailed fits using extended Kok models. The small reproducible shifts of several low-field peak positions of the S-2 EPR multiline signal in S. elongatus compared to spinach suggest that slight differences in the coordination geometry and/or the ligands of the manganese cluster exist between thermophilic cyanobacteria and higher plants

Nitric Oxide-Induced Formation of the S_-₂ State in the Oxygen-Evolving Complex of Photosystem II from <i>Synechococcus elongatus</i>^†

In spinach photosystem II (PSII) membranes, the tetranuclear manganese cluster of the oxygen-evolving complex (OEC) can be reduced by incubation with nitric oxide at −30 °C to a state which is characterized by an Mn2(II, III) EPR multiline signal [Sarrou, J., Ioannidis, N., Deligiannakis, Y., and Petrouleas, V. (1998) Biochemistry 37, 3581−3587]. This state was recently assigned to the S-2 state of the OEC [Schansker, G., Goussias, C., Petrouleas, V., and Rutherford, A. W. (2002) Biochemistry 41, 3057−3064]. On the basis of EPR spectroscopy and flash-induced oxygen evolution patterns, we show that a similar reduction process takes place in PSII samples of the thermophilic cyanobacterium Synechococcus elongatus at both −30 and 0 °C. An EPR multiline signal, very similar but not identical to that of the S-2 state in spinach, was obtained with monomeric and dimeric PSII core complexes from S. elongatus only after incubation at −30 °C. The assignment of this EPR multiline signal to the S-2 state is corroborated by measurements of flash-induced oxygen evolution patterns and detailed fits using extended Kok models. The small reproducible shifts of several low-field peak positions of the S-2 EPR multiline signal in S. elongatus compared to spinach suggest that slight differences in the coordination geometry and/or the ligands of the manganese cluster exist between thermophilic cyanobacteria and higher plants

Size Determination of Cyanobacterial and Higher Plant Photosystem II by Gel Permeation Chromatography, Light Scattering, and Ultracentrifugation^†

The oxygen-evolving photosystem II core complexes (PSIIcc) from the thermophilic cyanobacterium Thermosynechococcus elongatus (PSIIccTe) and the higher plant Spinacia oleracea (PSIIccSo) have been isolated from the thylakoid membrane by solubilization with n-dodecyl-β-d-maltoside, purified and characterized by gel permeation chromatography (GPC), dynamic light scattering (DLS), and analytical ultracentrifugation (AUC). DLS suggests that PSIIcc from both organisms exists as a monomer in dilute solution and aggregates with increasing protein concentration. In contrast to DLS, GPC and AUC showed that PSIIcc of both organisms occur as monomers and dimers, and it became clear from our studies that calibration of GPC columns with soluble proteins leads to wrong estimates of the molecular masses of membrane proteins. At a PSIIcc protein concentration of 0.2 mg/mL, molar masses, M, of 756 ± 18 kDa and 710 ± 15 kDa for dimeric PSIIccTe and PSIIccSo, respectively, were determined by analytical ultracentrifugation. At very low protein concentrations, at or below 0.05 mg/mL, the dimeric form of PSIIccTe partially dissociates (20−30%) to form monomers. On the basis of these studies 3-dimensional crystals of PSIIccTe were obtained that contain dimers in the asymmetric unit [Zouni, A. et al. (2001) Nature 409, 739−743]. Using synchrotron radiation the crystals diffract to a resolution of 3.8 Å, which has been improved recently to 3.2 Å [Biesiadka, J., et al. (2004) Phys. Chem. Chem. Phys. 6, 4733−4736]

Size Determination of Cyanobacterial and Higher Plant Photosystem II by Gel Permeation Chromatography, Light Scattering, and Ultracentrifugation^†

The oxygen-evolving photosystem II core complexes (PSIIcc) from the thermophilic cyanobacterium Thermosynechococcus elongatus (PSIIccTe) and the higher plant Spinacia oleracea (PSIIccSo) have been isolated from the thylakoid membrane by solubilization with n-dodecyl-β-d-maltoside, purified and characterized by gel permeation chromatography (GPC), dynamic light scattering (DLS), and analytical ultracentrifugation (AUC). DLS suggests that PSIIcc from both organisms exists as a monomer in dilute solution and aggregates with increasing protein concentration. In contrast to DLS, GPC and AUC showed that PSIIcc of both organisms occur as monomers and dimers, and it became clear from our studies that calibration of GPC columns with soluble proteins leads to wrong estimates of the molecular masses of membrane proteins. At a PSIIcc protein concentration of 0.2 mg/mL, molar masses, M, of 756 ± 18 kDa and 710 ± 15 kDa for dimeric PSIIccTe and PSIIccSo, respectively, were determined by analytical ultracentrifugation. At very low protein concentrations, at or below 0.05 mg/mL, the dimeric form of PSIIccTe partially dissociates (20−30%) to form monomers. On the basis of these studies 3-dimensional crystals of PSIIccTe were obtained that contain dimers in the asymmetric unit [Zouni, A. et al. (2001) Nature 409, 739−743]. Using synchrotron radiation the crystals diffract to a resolution of 3.8 Å, which has been improved recently to 3.2 Å [Biesiadka, J., et al. (2004) Phys. Chem. Chem. Phys. 6, 4733−4736]

Coherences of Photoinduced Electron Spin Qubit Pair States in Photosystem I

This publication presents the first comprehensive experimental study of electron spin coherences in photosynthetic reaction center proteins, specifically focusing on photosystem I (PSI). The ultrafast electron transfer in PSI generates spin-correlated radical pairs (SCRPs), which are entangled spin pairs formed in well-defined spin states (Bell states). Since their discovery in our group in the 1980s, SCRPs have been extensively used to enhance our understanding of structure–function relationships in photosynthetic proteins. More recently, SCRPs have been utilized as tools for quantum sensing. Electron spin decoherence poses a significant challenge in realizing practical applications of electron spin qubits, particularly the creation of quantum entanglement between multiple electron spins. This work is focused on the systematic characterization of decoherence in SCRPs of PSI. These decoherence times were measured as electron spin echo decay times, termed phase memory times (TM), at various temperatures. Decoherence was recorded on both transient SCRP states P700+A1– and thermalized states. Our study reveals that TM exhibits minimal dependence on the biological species, biochemical treatment, and paramagnetic species. The analysis indicates that nuclear spin diffusion and instantaneous diffusion mechanisms alone cannot explain the observed decoherence. As a plausible explanation we discuss the assumption that the low-temperature dynamics of methyl groups in the protein surrounding the unpaired electron spin centers is the main factor governing the loss of the spin coherence in PSI

Cr L‑Edge X‑ray Absorption Spectroscopy of Cr^III(acac)₃ in Solution with Measured and Calculated Absolute Absorption Cross Sections

X-ray absorption spectroscopy at the L-edge of 3d transition metals is widely used for probing the valence electronic structure at the metal site via 2p–3d transitions. Assessing the information contained in L-edge absorption spectra requires systematic comparison of experiment and theory. We here investigate the Cr L-edge absorption spectrum of high-spin chromium acetylacetonate CrIII(acac)3 in solution. Using a transmission flatjet enables determining absolute absorption cross sections and spectra free from X-ray-induced sample damage. We address the challenges of measuring Cr L absorption edges spectrally close to the O K absorption edge of the solvent. We critically assess how experimental absorption cross sections can be used to extract information on the electronic structure of the studied system by comparing our results of this CrIII (3d3) complex to our previous work on L-edge absorption cross sections of MnIII(acac)3 (3d4) and MnII(acac)2 (3d5). Considering our experimental uncertainties, the most insightful experimental observable for this d3(CrIII)–d4(MnIII)–d5(MnII) series is the L-edge branching ratio, and we discuss it in comparison to semiempirical multiplet theory and ab initio restricted active space calculations. We further discuss and analyze trends in integrated absorption cross sections and correlate the spectral shapes with the local electronic structure at the metal sites

X‑ray Emission Spectroscopy as an <i>in Situ</i> Diagnostic Tool for X‑ray Crystallography of Metalloproteins Using an X‑ray Free-Electron Laser

Serial femtosecond crystallography (SFX) using the ultrashort X-ray pulses from a X-ray free-electron laser (XFEL) provides a new way of collecting structural data at room temperature that allows for following the reaction in real time after initiation. XFEL experiments are conducted in a shot-by-shot mode as the sample is destroyed and replenished after each X-ray pulse, and therefore, monitoring and controlling the data quality by using <i>in situ</i> diagnostic tools is critical. To study metalloenzymes, we developed the use of simultaneous collection of X-ray diffraction of crystals along with X-ray emission spectroscopy (XES) data that is used as a diagnostic tool for crystallography, by monitoring the chemical state of the metal catalytic center. We have optimized data analysis methods and sample delivery techniques for fast and active feedback to ensure the quality of each batch of samples and the turnover of the catalytic reaction caused by reaction triggering methods. Here, we describe this active <i>in situ</i> feedback system using Photosystem II as an example that catalyzes the oxidation of H₂O to O₂ at the Mn₄CaO₅ active site. We used the first moments of the Mn Kβ_1,3 emission spectra, which are sensitive to the oxidation state of Mn, as the primary diagnostics. This approach is applicable to different metalloproteins to determine the integrity of samples and follow changes in the chemical states of the reaction that can be initiated by light or activated by substrates and offers a metric for determining the diffraction images that are used for the final data sets

The Protonation States of Oxo-Bridged Mn^IV Dimers Resolved by Experimental and Computational Mn K Pre-Edge X‑ray Absorption Spectroscopy

In nature, the protonation of oxo bridges is a commonly encountered mechanism for fine-tuning chemical properties and reaction pathways. Often, however, the protonation states are difficult to establish experimentally. This is of particular importance in the oxygen evolving complex of photosystem II, where identification of the bridging oxo protonation states is one of the essential requirements toward unraveling the mechanism. In order to establish a combined experimental and theoretical protocol for the determination of protonation states, we have systematically investigated a series of Mn model complexes by Mn K pre-edge X-ray absorption spectroscopy. An ideal test case for selective bis-μ-oxo-bridge protonation in a Mn dimer is represented by the system [Mn^IV₂(salpn)₂(μ-OH_<i>n</i>)₂]^<i>n</i>+. Although the three species [Mn^IV₂(salpn)₂(μ-O)₂], [Mn^IV₂(salpn)₂(μ-O)­(μ-OH)]⁺ and [Mn^IV₂(salpn)₂(μ-OH)₂]²⁺ differ only in the protonation of the oxo bridges, they exhibit distinct differences in the pre-edge region while maintaining the same edge energy. The experimental spectra are correlated in detail to theoretically calculated spectra. A time-dependent density functional theory approach for calculating the pre-edge spectra of molecules with multiple metal centers is presented, using both high spin (HS) and broken symmetry (BS) electronic structure solutions. The most intense pre-edge transitions correspond to an excitation of the Mn 1s core electrons into the unoccupied orbitals of local e_g character (d_<i>z</i>² and d_<i>xy</i> based in the chosen coordinate system). The lowest energy experimental feature is dominated by excitations of 1s-α electrons, and the second observed feature is primarily attributed to 1s-β electron excitations. The observed energetic separation is due to spin polarization effects in spin-unrestricted density functional theory and models final state multiplet effects. The effects of spin polarization on the calculated Mn K pre-edge spectra, in both the HS and BS solutions, are discussed in terms of the strength of the antiferromagnetic coupling and associated changes in the covalency of Mn–O bonds. The information presented in this paper is complemented with the X-ray emission spectra of the same compounds published in an accompanying paper. Taken together, the two studies provide the foundation for a better understanding of the X-ray spectroscopic data of the oxygen evolving complex (OEC) in photosystem II