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Understanding cellular mechanics requires evaluating the mechanical and chemical cues that regulate the actin cytoskeleton, particularly filopodia and lamellipodia. Therefore, this study aims to investigate the effect of scaffolds properties on cell migration. The results showed that scaffolds toughness, strain, and strength played a key role in promoting cell movement by stimulating the dynamic formation of filopodia and lamellipodia. The test sample containing 3 wt% G significantly enhanced toughness, yield strength, and strain, leading to increase cell motility as well as enhanced development of longer filopodia and larger lamellipodia in MG-63 cells. These results provide valuable insights for optimizing scaffolds to promote bone tissue regeneration. [ABSTRACT FROM AUTHOR]

Soil acidification has been widely recognized as a server environmental issue. Acid soil causes hazards to plant species' development, growth and also the yield of crop through the world. Rhododendron species have been demonstrated to prefer to grow in acid soil. However, the molecular-response mechanism of Rhododendron seedlings and their interspecific variance to different pH conditions remains unclear. Herein, we compared the response of R. decorum and R. griersonianum to different pH treatments through physiological indicators, transcriptome analysis, and weighted gene co-expression network analysis. We found that the physiological and biochemical traits and DEG numbers indicted that the narrow-ranging species R. griersonianum was more sensitive to pH conditions than R. decorum. Photosynthesis and starch and sucrose metabolism shared significant enrichment pathways in R. griersonianum and R. decorum. However, differences in gene-expression patterns related to these pathways existed in response to pH treatments. Furthermore, several unique enriched pathways and expression patterns were identified between both species. Specifically, the genes involved in porphyrin and chlorophyll metabolism, carotenoid biosynthesis, carbon fixation in photosynthetic organisms, and photorespiration were highly expressed at pH 4.5 and 5.5 in R. griersonianum. Meanwhile, genes related to brassinosteroids, galactose metabolism, phenylpropanoids, and flavonoid biosynthesis were identified in R. decorum. This finding implied the different strategies of Rhododendron species during response and adaptation to soil pH conditions. The present study provided new insights to understand the molecular mechanisms of woody plant adaptation to acidic environment. [ABSTRACT FROM AUTHOR]

The global practical implementation of proton exchange membrane fuel cells (PEMFCs) heavily relies on the advancement of highly effective platinum (Pt)-based electrocatalysts for the oxygen reduction reaction (ORR). To achieve high ORR performance, electrocatalysts with highly accessible reactive surfaces are needed to promote the uncovering of active positions for easy mass transportation. In this critical review, we introduce different approaches for the emerging development of effective ORR electrocatalysts, which offer high activity and durability. The strategies, including morphological engineering, geometric configuration modification via supporting materials, alloys regulation, core-shell, and confinement engineering of single atom electrocatalysts (SAEs), are discussed in line with the goals and requirements of ORR performance enhancement. We review the ongoing development of Pt electrocatalysts based on the syntheses, nanoarchitecture, electrochemical performances, and stability. We eventually explore the obstacles and research directions on further developing more effective electrocatalysts. [ABSTRACT FROM AUTHOR]

Copyright of Rare Metals is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Principles of inexpensive biotechnology are being increasingly used to address the problems posed by the use of lithium-sulfur batteries. We used chitin, a low-cost marine biowaste product, as a precursor for the in-situ preparation of chitin-derived nitrogen-doped hierarchical porous carbon fibers (CNHPCFs) containing abundant pores. These materials are characterized by varying morphologies and high specific surface areas and present a hierarchical porous structure. CNHPCFs adsorb polysulfides, exhibit good ionic conductivity, and can be potentially used to generate green energy. These properties help address the problems of volume expansion and slow transport. The CNHPCF-1@S cathode exhibits excellent cycling performance and high capacity (1368.80 mAh·g−1 at 0.2 C; decay rate: 0.011% per turn at 5 C). The high electrochemical reversibility recorded for CNHPCF-1@S and the stepwise reaction mechanism followed were studied using the in-situ X-ray diffraction and in-situ Raman spectroscopy techniques. The results reported herein can potentially help develop new ideas for the recycling and treatment of marine biofertilizers. The results can also provide a platform to improve the application prospects of lithium-sulfur batteries. [ABSTRACT FROM AUTHOR]

The recent development of Aurum (Au) introduced Platinum (Pt) based nanomaterials is of great significance to direct methanol fuel cell as electrocatalysts for anode reactions, due to its stability and anti-poisoning features. Therefore, the performance of PtAu based catalysts with different elements, atomic ratio, and morphology was studied in methanol solution to further improve its electrocatalytic activity. Furthermore, the effects of Au have aroused the researchers' attention in Pt-based nanocatalysts. In this review, we summarize the controllable synthesis, mechanism, and catalytic performance of Au introduced Pt-based electrocatalysts such as PtAu core-shell nanostructures, PtAu dendrite, PtAu nanowires, self-supporting Au@Pt NPs, and Au@Pt star-like nanocrystals for the methanol oxidation reaction. Finally, the challenges and research directions for the future development of PtAu based catalysts are provided. [ABSTRACT FROM AUTHOR]

Summary: G-quadruplexes (G4s) are DNA or RNA structures formed by guanine-rich repeating sequences. Recently, G4s have become a highly attractive therapeutic target for BRCA-deficient cancers. Here, we show that a substituted quinolone amide compound, MTR-106, stabilizes DNA G-quadruplexes in vitro. MTR-106 displayed significant antiproliferative activity in homologous recombination repair (HR)-deficient and PARP inhibitor (PARPi)-resistant cancer cells. Moreover, MTR-106 increased DNA damage and promoted cell cycle arrest and apoptosis to inhibit cell growth. Importantly, its oral and i.v. administration significantly impaired tumor growth in BRCA-deficient xenograft mouse models. However, MTR-106 showed modest activity against talazoparib-resistant xenograft models. In rats, the drug rapidly distributes to tissues within 5 min, and its average concentrations were 12-fold higher in the tissues than in the plasma. Overall, we identified MTR-106 as a novel G-quadruplex stabilizer with high tissue distribution, and it may serve as a potential anticancer agent. [ABSTRACT FROM AUTHOR]

Bacon Ke, who did pioneering research on the primary photochemistry of photosynthesis, was born in China on July 26, 1920, and currently, he is living in a senior home in San Francisco, California, and is a centenarian. To us, this is a very happy and unique occasion to honor him. After providing a brief account of his life, and a glimpse of his research in photosynthesis, we present here "messages" for Bacon Ke@ 100 from: Robert Alfano (USA), Charles Arntzen (USA), Sandor Demeter (Hungary), Richard A. Dilley (USA), John Golbeck (USA), Isamu Ikegami (Japan), Ting-Yun Kuang (China), Richard Malkin (USA), Hualing Mi (China), Teruo Ogawa (Japan), Yasusi Yamamoto (Japan), and Xin-Guang Zhu (China). [ABSTRACT FROM AUTHOR]

Metal sulfide/carbon composite reveals to be a prospective electrode material for lithium-ion batteries due to the synergy of the two components, and their structure greatly determines the electrochemical performance. We herein have successfully fabricated an in situ encapsulation of Ni3S2 nanoparticles into carbon nanowalls (Ni3S2/CNWs) with three-dimensional interconnected porous structures, which are synthesized assisted by cation adsorption and following hydrothermal process. The abundant mesoporous carbon nanowalls are used as both conductive matrix and protective layer to alleviate the volume change of Ni3S2. Benefiting from the superior theoretical capacity of Ni3S2 and unique structure of CNWs, Ni3S2/CNWs-1 anodes show the high discharge capacity of 906 mAh g−1 at 200 mA g−1 after cycling 200 times, outstanding rate capacity of 567 mAh g−1 at 5 A g−1 and super-long cycling life of 666 mAh g−1 at 2 A g−1 after cycling 1000 times. More importantly, the button-type full cells based on Ni3S2/CNWs-1 anodes and LiFePO4 cathodes present excellent cycling stability and practicality. [ABSTRACT FROM AUTHOR]

Summary: The bromodomain and extra-terminal domain (BET) family of proteins, especially bromodomain-containing protein 4 (BRD4), has emerged as exciting anti-tumor targets due to their important roles in epigenetic regulation. Therefore, the discovery of BET inhibitors with promising anti-tumor efficacy will provide a novel approach to epigenetic anticancer therapy. Recently, we discovered the new BET inhibitor compound 171, which is derived from a polo-like kinase 1 (PLK1)-BRD4 dual inhibitor based on our previous research. Compound 171 was found to maintain BET inhibition ability without PLK1 inhibition, and there was no selectivity among BET family members. The in vitro and in vivo results both indicated that the overall anti-tumor activity of compound 171 was improved compared with the (+)-JQ-1 or OTX-015 BET inhibitors. Furthermore, we found that compound 171 could regulate the expression of cell cycle-regulating proteins including c-Myc and p21 and induce cell cycle arrest in the G0/G1 phase. However, compound 171 only has a quite limited effect on apoptosis, in considering that apoptosis was only observed at doses greater than 50 μM. To determine the mechanisms underlying cell death, proliferation activity assay was conducted. The results showed that compound 171 induced clear anti-proliferative effects at doses that no obvious apoptosis was induced, which indicated that the cell cycle arresting effect contributed mostly to its anti-tumor activity. The result of this study revealed the anti-tumor mechanism of compound 171, and laid a foundation for the combination therapy in clinical practice, if compound 171 or its series compounds become drug candidates in the future. [ABSTRACT FROM AUTHOR]

This study aims to investigate the effects of centralized allocation and optimization of railway resources on overall operational efficiency of the railway industry. Its results are intended to help Taiwan railway industry in resource allocation and reduction of organization resistance caused by resource deployment in Taiwan. For this purpose, this study proposes and divides resource reallocation into long-, middle-, and short-term plans, with three resource adjustment programs. These programs consider different geographical ranges and resource conditions of personnel and equipment in resource allocation by using a two-phase centralized data envelopment analysis. Conducted in 2011, the Taiwan railway data analysis indicated that high overall output that was attributed to efficient allocation of resources induced large-scale organizational changes and adjustments (such as staff reduction) in the railway industry. These changes resulted in widespread organization resistance. Nonetheless, this process enabled the railway industry in Taiwan to achieve balance between output and organization resistance under different environments efficiently. [ABSTRACT FROM AUTHOR]

Champereia manillana (Bl.) Merr. is a vulnerable plant from the family Opiliaceae. The complete chloroplast genome (plastome) of Opiliaceae family was sequenced for the first time. The plastome of C. manillana was 147,461 bp in length. It was consisted of a large single copy (LSC) region (83,505 bp) and a small single copy (SSC) region (7,806 bp), which were separated by two inverted repeats (IRs, 28,075 bp). This plastome contained 101 different genes, including 67 protein-coding genes (PCGs), 30 tRNA genes and four rRNA genes. The overall GC content was 37.4%. Furthermore, phylogenetics analysis of 4 species in the Santalales was also conducted. The whole chloroplast genome of this species will be useful for the future plant evolutionary, phylogeny and genomic studies in the family Opiliaceae. [ABSTRACT FROM AUTHOR]

Aim:Oligomannurarate 971 derived from a marine plant has shown neuroprotective effects. In this study we synthesized a series of truncated derivatives of the oligosaccharide, and investigated the effect of these derivatives against Aβ peptide toxicity in vitro.Methods:The sulfoxide method was applied to synthesize the derivatives. SH-SY5Y human neuroblastoma cells were treated with Aβ1-40 (2 μmol/L), and the cell viability was detected using a CCK8 assay.Results:A series of β-(1,4)-D-mannosyl oligosaccharide, ranging from the disaccharide to the hexasaccharide, were synthesized. Addition of 10 μmol/L β-(1,4)-D-mannobiose 6, β-(1,4)-D-mannotriose 9 or β-(1,4)-D-mannotetraose 12 in SH-SY5Y cells significantly attenuated Aβ1-40-induced toxicity. The efficacies were similar to those caused by 10 μmol/L oligomannurarate 971 or alzhemed. Other oligosaccharides including oligomaltoses and oligocelluloses were less active.Conclusion:Synthetic homogeneous short chain β-(1,4)-D-mannans shows neuroprotective effect against Aβ peptide toxicity similar to that of heterogeneous oligomannurarate 971 and alzhemed. [ABSTRACT FROM AUTHOR]

Three-dimensional porous biodegradable polymer scaffolds have been widely used for tissue engineering of bone repair or regeneration. The primary function of scaffolds is to provide structure support for the cells adhesion and proliferation. This study selects the Poly- ɛ-caprolactone (PCL) as material, NaCl mixed with hydroxyapatite (HA) or nano-aluminum oxide (nAl 2O 3) for porous scaffold. This study uses the solvent casting/particulate leaching method to fabricate the porous scaffold. The authors discuss the compression mechanical properties, physical properties (porosity, moisture content, contact angle) of a pure PCL, PCL/mHA, PCL/nHA and PCL/nAl 2O 3 scaffolds. In vitro cell culture is used for osteoblast cell (MG63) and the microculture tetrazolium test (MTT) is undertaken in the scaffold. The scaffolds are implanted to the femur of rats and histological examination is attempted after 2 weeks. The experimental results indicate that HA and nAl 2O 3 can improve the hydrophilic property. In conclusion, the PCL/nHA scaffold exhibits splendid in vivo biocompatibility and osteogenesis. [ABSTRACT FROM AUTHOR]

Aim:To decipher the molecular interactions between c-Met and its type I inhibitors and to facilitate the design of novel c-Met inhibitors.Methods:Based on the prototype model inhibitor 1, four ligands with subtle differences in the fused aromatic rings were synthesized. Quantum chemistry was employed to calculate the binding free energy for each ligand. Symmetry-adapted perturbation theory (SAPT) was used to decompose the binding energy into several fundamental forces to elucidate the determinant factors.Results:Binding free energies calculated from quantum chemistry were correlated well with experimental data. SAPT calculations showed that the predominant driving force for binding was derived from a sandwich π-π interaction with Tyr-1230. Arg-1208 was the differentiating factor, interacting with the 6-position of the fused aromatic ring system through the backbone carbonyl with a force pattern similar to hydrogen bonding. Therefore, a hydrogen atom must be attached at the 6-position, and changing the carbon atom to nitrogen caused unfavorable electrostatic interactions.Conclusion:The theoretical studies have elucidated the determinant factors involved in the binding of type I inhibitors to c-Met. [ABSTRACT FROM AUTHOR]

Aim:To design and synthesize bivalent ligands for adenosine A1-dopamine D1 receptor heteromers (A1-D1R), and evaluate their pharmacological activities.Methods:Bivalent ligands and their corresponding A1R monovalent ligands were designed and synthesized. The affinities of the bivalent ligands for A1R and D1R in rat brain membrane preparation were examined using radiolabeled binding assays. To demonstrate the formation of A1-D1R, fluorescence resonance energy transfer (FRET) was conducted in HEK293 cells transfected with D1-CFP and A1-YFP. Molecular modeling was used to analyze the possible mode of protein-protein and protein-ligand interactions.Results:Two bivalent ligands for A1R and D1R (20a, 20b), as well as the corresponding A1R monovalent ligands (21a, 21b) were synthesized. In radiolabeled binding assays, the bivalent ligands showed affinities for A1R 10-100 times higher than those of the corresponding monovalent ligands. In FRET experiments, the bivalent ligands significantly increased the heterodimerization of A1R and D1R compared with the corresponding monovalent ligands. A heterodimer model with the interface of helixes 3, 4, 5 of A1R and helixes 1, 6, 7 from D1R was established with molecular modeling. The distance between the two ligand binding sites in the heterodimer model was approximately 48.4 Å, which was shorter than the length of the bivalent ligands.Conclusion:This study demonstrates the existence of A1-D1R in situ and a simultaneous interaction of bivalent ligands with both the receptors. [ABSTRACT FROM AUTHOR]

This study forms hydroxyapatite-silica ceramic structure, which can generate interconnected porous 3D models suitable as bone scaffold, using a novel selective laser sintering (SLS) technique. Hydroxyapatite (HA) powder and a silica sol are first mixed into slurries. After processing by SLS, the HA particles are embedded in the gelled silica matrix to form green parts. The processed parts are analyzed by scanning electron microscopy (SEM). The number of cells attached on this scaffold surface is obtained by the in vitro cultured cells test. The higher number of viable cells are obtained when the sintering temperature of the scaffold was 1200°C at day 4 of cell culturing. The proposed technology can be applied to generate a bone scaffold model of porous bio-ceramics for biomedicine. [ABSTRACT FROM AUTHOR]

This study investigates warpage of electronic dictionary battery covers fabricated using thin-wall injection molding as a replacement for conventional insert molding. The primary concern is the molding window in thin-wall injection molding for acrylonitrile-butadiene styrene (ABS) and polycarbonate (PC)+ABS plastics. Finally, the process parameters for thin-wall injection molding that eliminate warpage of electronic dictionary battery covers are identified. Experimental results demonstrate that the area of the molding window for ABS exceeds that for PC+ABS. Analysis of the molding window reveals that ABS is more appropriate than PC+ABS for battery covers. Low melt temperature, high injection speed, and high packing pressure eliminate battery cover warpage. Melt temperature is the most important process parameter for eliminating warpage when using both ABS and PC+ABS. [ABSTRACT FROM AUTHOR]

Aim:Cytarabine is an efficient anticancer agent for acute myelogenous leukemia, but with short plasma half-life and rapid deamination to its inactive metabolite. The aim of this study was to design and synthesize novel cholic acid-cytarabine conjugates to improve its pharmacokinetic parameters.Methods:The in vitro stability of novel cholic acid-cytarabine conjugates was investigated in simulated gastric and intestinal fluid, mouse blood and liver homogenate using HPLC. The portacaval samples of the conjugates were examined in male Sprague-Dawley rats using LC/MS, and in vivo distribution was examined in male Kunming mice using LC/MS. Antitumor activities were tested in HL60 cells using MTT assay.Results:Cholic acid-cytarabine compounds with four different linkers were designed and synthesized. All the four cholic acid-cytarabine conjugates could release cytarabine when incubated with the simulated gastric and intestinal fluid, mouse blood and liver homogenate. The conjugates 6, 12, and 16 were present in the portacaval samples, whereas the conjugate 7 was not detected. The conjugates 6 and 16 showed high specificity in targeting the liver (liver target index 34.9 and 16.3, respectively) and good absorption in vivo, as compared with cytarabine. In cytarabine-sensitive HL60 cells, the conjugates 6, 12, and 16 retained potent antitumor activities.Conclusion:Three novel cholic acid-cytarabine conjugates with good liver-targeting properties and absorption were obtained. Further optimization of the conjugates is needed in the future. [ABSTRACT FROM AUTHOR]

We calculated the Coulomb failure stress change generated by the 1976 Tangshan earthquake that is projected onto the fault planes and slip directions of large subsequent aftershocks. Results of previous studies on the seismic failure distribution, crustal velocity and viscosity structures of the Tangshan earthquake are used as model constraints. Effects of the local pore fluid pressure and impact of soft medium near the fault are also considered. Our result shows that the subsequent Luanxian and Ninghe earthquakes occurred in the regions with a positive Coulomb failure stress produced by the Tangshan earthquake. To study the triggering effect of the Tangshan, Luanxian, and Ninghe earthquakes on the follow-up small earthquakes, we first evaluate the possible focal mechanisms of small earthquakes according to the regional stress field and co-seismic slip distributions derived from previous studies, assuming the amplitude of regional tectonic stress as 10 MPa. By projecting the stress changes generated by the above three earthquakes onto the possible fault planes and slip directions of small earthquakes, we find that the “butterfly” distribution pattern of increased Coulomb failure stress is consistent with the spatial distribution of follow-up earthquakes, and 95% of the aftershocks occurred in regions where Coulomb failure stresses increase, indicating that the former large earthquakes modulated occurrences of follow-up earthquakes in the Tangshan earthquake sequence. This result has some significance in rapid assessment of aftershock hazard after a large earthquake. If detailed failure distribution, seismogenic fault in the focal area and their slip features can be rapidly determined after a large earthquake, our algorithm can be used to predict the locations of large aftershocks. [ABSTRACT FROM AUTHOR]

This paper presents some methods that the standard acceleration design response spectra derived from the present China code for seismic design of buildings are transformed into the seismic demand spectra, and that the base shear force-roof displacement curve of structure is converted to the capacity spectrum of an equivalent single-degree-of-freedom (SDOF) system. The capacity spectrum method (CSM) is programmed by means of MATLAB7.0 computer language. A dual lateral force resisting system of 10-story steel frame-steel plate shear walls (SPSW) is designed according to the corresponding China design codes. The base shear force-roof displacement curve of structure subjected to the monotonic increasing lateral inverse triangular load is obtained by applying the equivalent strip model to stimulate SPSW and by using the finite element analysis software SAP2000 to make Pushover analysis. The seismic performance of this dual system subjected to three different conditions, i.e. the 8-intensity frequently occurred earthquake, fortification earthquake and seldom occurred earthquake, is evaluated by CSM program. The excessive safety of steel frame-SPSW system designed according to the present China design codes is pointed out and a new design method is suggested. [ABSTRACT FROM AUTHOR]

We simulate accumulative Coulomb failure stress change in a layered Maxwell viscoelastic media in the northeastern Qinghai-Xizang (Tibetan) Plateau since 1920. Lithospheric stress/strain evolution is assumed to be driven by dislocations of large earthquakes ( M≥7.0) and secular tectonic loading. The earthquake rupture parameters such as the fault rupture length, width, and slip are either adopted from field investigations or estimated from their statistic relationships with the earthquake magnitudes and seismic moments. Our study shows that among 20 large earthquakes ( M≥7.0) investigated, 17 occurred in areas where the Coulomb failure stress change is positive, with a triggering rate of 85%. This study provides essential data for the intermediate to long-term likelihood estimation of large earthquakes in the northeastern Tibetan Plateau. [ABSTRACT FROM AUTHOR]

The displacement field generated by aftershocks in Landers earthquake fault zone and its adjacent areas is calculated in this study. The result is compared with the displacement field of the main shock calculated by co-seismic slip model of Wald and Heaton (1994). The result shows that the direction of displacement generated by aftershocks in Landers seismic fault plane and its adjacent areas is consistent with that generated by main shock. The rupture of aftershock is generally inherited from main shock. The displacement generated by aftershocks is up to an order of centimeter and can be measured by GPS sites nearby. So when we use geodetic data measured after earthquake to study the geophysical problems such as crustal viscosity structure, afterslip distribution, etc., only the displacement field generated by aftershocks considered, can uncertainty be reduced to minimum and realistic result be obtained. [ABSTRACT FROM AUTHOR]

Application of NaHSO3 solution at low concentrations (20–200 μM) to the culture medium enhanced photosynthetic oxygen evolution in cyanobacterium Synechocystis PCC6803 by more than 10%. The slow phase of ms-DLE was strengthened, showing that the transmembrane proton motive force related to photophosphorylation was enhanced. It was also observed that dry weight as well as ATP content under illuminated conditions were both increased after the treatment, indicating that low concentrations of NaHSO3 could enhance the supply of ATP and thus increase biomass accumulation. In accord with the promotion in the photosynthetic oxygen evolution and ATP content, the transient increase in chlorophyll fluorescence after the termination of actinic light was increased; and meanwhile, the half-time of re-reduction of P700+ in the presence of DCMU after a pulse light under background far-red light was shortened by approximately 30%, indicating that cyclic electron flow around PS I was accelerated by the treatment. Based on these results it is suggested that the increase in photosynthesis in Synechocystis PCC6803 caused by low concentrations of NaHSO3 solution might be due to the stimulation of the cyclic electron flow around PS I and thus the increase in photophosphorylation. [ABSTRACT FROM AUTHOR]

Presents a study which examined the relation between the enhancing effect of NaHSO... on photosynthesis and that on photophosphorylation in wheat leaves. Materials and methods used; Results; Discussion.

The relation between the fast phase of ms-DLE (delayed light emission measured with a phosphoroscope) and the proton released from water oxidation in spinach chloroplasts was studied in several aspects. When photophosphorylation was allowed to be coupled to the Hill reaction the intensity of the fast phase of ms-DLE of chloroplast was lowered more at 1 °C than at 25 °C, and the photophosphorylation rate within 40 ms of flashing light was higher at 1 °C than at 25 °C. Adding the ε subunit of ATP synthase to the chloroplast preparation to block the leakage of protons through ATP synthase, the intensity of the fast phase of ms-DLE was enhanced, to a larger extent at 1 °C than at 25°C. When the ms-DLE was measured under isotonic conditions, the intensity of fast phase of ms-DLE enhanced by proton released from oxidation of water was more pronounced. The above results support the suggestion that under lower temperature and isotonic conditions, the proton released from water oxidation was liable to be localized and could enhance the intensity of the fast phase of ms-DLE more effectively. [ABSTRACT FROM AUTHOR]

Weak red light-induced changes in chlorophyll fluorescence parameters and in the distribution of PS I and PS II in thylakoid membranes were measured in wheat leaves to investigate effective ways to alter the excitation energy distribution between the two photosystems during state transition in vivo. Both the chlorophyll fluorescence parameter Fm/Fo and F685/F735, the ratio of fluorescence yields of the two photosystems at low temperature (77 K), decreased when wheat leaves were illuminated by weak red light of 640 nm, however, Fm/Fo decreased to its minimum in a shorter time than F685/F735. When Photosystem (PS II) thylakoid (BBY) membranes from adequately dark-adapted leaves (control) and from red light-illuminated leaves were subjected to SDS-polyacrylamide gel electrophoresis under mildly denaturing conditions, PS I was almost absent in the control, but was present in the membranes from the leaves preilluminated with the weak red light. In consonance with this result, the content of Cu, measured by means of the energy dispersive X-ray microanalysis (EDX), increased in the central region, but decreased in the margin of the grana stacks from the leaves preilluminated by the red light as compared with the control. It is therefore suggested that: (i) both spillover and absorption cross-section changes are effective ways to alter the excitation energy distribution between the two photosystems during state transitions in vivo, and the change in spillover has a quicker response to the unbalanced light absorption of the two photosystems than the change in light absorption cross-section, and (ii) the migration of PS I towards the central region of grana stack during the transition to state 2 leads to the enhancement of excitation energy spillover from PS II to PS I. [ABSTRACT FROM AUTHOR]

Photoinactivation of Photosystem (PS) II in vivo was investigated by cumulative exposure of pea, rice and spinach leaves to light pulses of variable duration from 2 to 100 s, separated by dark intervals of 30 min. During each light pulse, photosynthetic induction occurred to an extent depending on the time of illumination, but steady-state photosynthesis had not been achieved. During photosynthetic induction, it is clearly demonstrated that reciprocity of irradiance and duration of illumination did not hold: hence the same cumulative photon exposure (mol m) does not necessarily give the same extent of photoinactivation of PS II. This contrasts with the situation of steady-state photosynthesis where the photoinactivation of PS II exhibited reciprocity of irradiance and duration of illumination (Park et al. (1995) Planta 196: 401-411). We suggest that, for reciprocity to hold between irradiance and duration of illumination, there must be a balance between photochemical (qP) and non-photochemical (NPQ) quenching at all irradiances. The index of susceptibility to light stress, which represents an intrinsic ability of PS II to balance photochemical and non-photochemical quenching, is defined by the quotient (1-qP)/NPQ. Although constant in steady-state photosynthesis under a wide range of irradiance (Park et al. (1995). Plant Cell Physiol 36: 1163-1169), this index of susceptibility for spinach leaves declined extremely rapidly during photosynthetic induction at a given irradiance, and, at a given cumulative photon exposure, was dependent on irradiance. During photosynthetic induction, only limited photoprotective strategies are developed: while the transthylakoid pH gradient conferred some degree of photoprotection, neither D1 protein turnover nor the xanthophyll cycle was operative. Thus, PS II is more easily photoinactivated during photosynthetic induction, a phenomenon that may have relevance for understorey leaves experiencing infrequent, short sunflecks. [ABSTRACT FROM AUTHOR]

The regulatory effects of malate on chloroplast Mg-ATPase were investigated and the mechanism was discussed. Malate stimulated methanol-activated membrane-bound and isolated CF Mg-ATPase activity. The γ subunit of CF may be involved in malate regulation of the enzyme function. Modification of γ subunit at one site of the peptide by NEM may affect malate stimulation of ATPase while at another site may have no effect. The effect of malate on the Mg-ATPase was also controlled by the Mg/ATP ratio in the reaction medium. The enhancing effect of malate on Mg-ATPase activity depended on the presence of high concentrations of Mg in the reaction mixture. Kinetic study showed that malate raised the V of catalysis without affecting the K for Mg ATP. The experiments imply that the stimulation of Mg-ATPase by malate is probably correlated with the P binding site on the enzyme. The regulation of ATPase activity by malate in chloroplasts may be relevant to its function in vivo. [ABSTRACT FROM AUTHOR]

Discusses the preparation of high loading plutonium supported on carbon by on-site reduction. Availability of methods for the preparation of carbon-supported catalysts; Control of the small cluster size to make high precious metal loading; Identification of the catalyst crystallites through transmission electron microscopy.