Photosystem I（PSI）absorbs and utilizes light energy to generate reducing power for the reduction of NADP＋ to NADPH with a quantum efficiency close to 100%. Plant PSI forms a supercomplex with light-harvesting complex I（LHCI）with a total molecular weight of over 600 kDa．X-ray structure analysis of the PSI-LHCI membrane-protein supercomplex has revealed detailed arrangement of the light-harvesting pigments and other cofactors especially within LHCI．Here the excited energy transfer（EET）pathways from LHCI to the PSI core and photoprotection mechanisms are discussed based on the structure obtained.
The initial reaction of photosynthesis takes place in photosystem II（PSII）, a 700 kDa membrane protein complex that catalyzes water-splitting reaction through an S-state cycle of the oxygen evolving complex（OEC）. The structure of PSII has been solved by X-ray diffraction（XRD）at 1.9 Å resolution, which revealed that the OEC is a Mn4CaO5 cluster coordinated by a well-defined protein environment. However, extended X-ray absorption fine structure（EXAFS）studies showed that the manganese atoms in the OEC are easily reduced by X-ray irradiation, and slight differences were found in the Mn-Mn distances determined by XRD and EXAFS studies. Very recently, it was demonstrated that radiation damage free structure can be obtainable using X-ray free electron lasers（XFEL）. In this paper, we report a radiation damage free structure of PSII in the S1 state at a resolution of 1.95 Å using femtosecond X-ray pulses of the SACLA facility. Compared with the structure from XRD, the OEC in the XFEL structure has Mn-Mn distances that are shorter by 0.1～0.2 Å. Based on the XFEL structure, the valences of each manganese atom were tentatively assigned as Mn1（＋3）, Mn2（＋4）, Mn3（＋4）and Mn4（＋3）in the S1 state and that O5 is a hydroxide ion and may serve as one of the substrate oxygen atoms. These findings provide a structural basis for the mechanism of oxygen evolution.
Excessive consumption of fructose in the Western diet is associated with an increased incidence of metabolic disorders such as obesity and non-alcoholic steatohepatitis. A growing interest is focused on the fructose transporter GLUT5. In this review, we describe crystal structures of the mammalian GLUT5 with its empty binding site exposed to either the extracellular side or intracellular side. By comparing structures in these two different conformational states, we show that the transport is achieved by a combination of global “rocker-switch”-like movement of transmembrane bundles and local asymmetric “gated-pore”-like rearrangement. This structural information is now open for designing novel therapeutic drugs.
Containerless processing, which enables a melt to be levitated in air, prevents the melt from crystallization at the boundary between the melt and a container wall. Accordingly, deeper undercooling can be realized. Metastable hexagonal Lu1－xScxFeO3 （0 ≤ x ≤ 0.8） were directly solidified from an undercooled melt by containerless processing with an aerodynamic levitation furnace. Synchrotron X-ray diffraction measurements revealed that the crystal structure of the hexagonal phase was isomorphous to hexagonal ferroelectric RMnO3 （R = rare earth ions） with a polar space group of P63cm. The weak ferromagnetic transition temperature increased from 150 K for x = 0 to 175 K for x = 0.7, which is the highest magnetic transition temperature among those of hexagonal RMnO3 and RFeO3.
We present a comprehensive study of the heat capacity, crystal structures, DFT calculations, and magnetic and electrical properties of a one-dimensional（1D）rhodium（I）-semiquinonato complex,［Rh（3,6-DBSQ-4,5-（MeO）2）（CO）2］∞（3）, where 3,6-DBSQ-4,5-（MeO）2•- represents 3,6-di-tert-butyl-4,5-dimethoxy-1,2-benzosemiquinonato radical anion. The compound 3 comprises neutral 1D chains of complex molecules stacked in a staggered arrangement with short Rh-Rh distances and exhibits unprecedented bistable multifunctionality with respect to its magnetic and conductive properties in the temperature range of 228-207 K. The observed bistability results from the thermal hysteresis across a first-order phase transition, and the transition accompanies the exchange of the interchain C-H…O hydrogen-bond partners between the semiquinonato ligands. The strong overlaps of the complex molecules lead to unusually strong ferromagnetic interactions in the low-temperature（LT）phase. Furthermore, the magnetic interactions in the 1D chain drastically change from strongly ferromagnetic in the LT phase to antiferromagnetic in the room-temperature（RT）phase with hysteresis. In addition, the compound 3 exhibits long-range antiferromagnetic ordering between the ferromagnetic chains and spontaneous magnetization because of spin canting（canted antiferromagnetism）at a transition temperature TN of 14.2 K. The electrical conductivity of 3 at 300 K is 4.8×10-4 S cm-1, which is relatively high despite Rh not being in a mixed-valence state. The temperature dependence of electrical resistivity also exhibits a clear hysteresis across the first-order phase transition. Furthermore, the ferromagnetic LT phase can be easily stabilized up to RT by the application of a relatively weak applied pressure of 1.4 kbar, which reflects the bistable characteristics and demonstrates the simultaneous control of multifunctionality through external perturbation.