Using steered molecular dynamics to predict and assess Hsp70 substrate-binding domain mutants that alter prion propagation.

Genetic screens using Saccharomyces cerevisiae have identified an array of cytosolic Hsp70 mutants that are impaired in the ability to propagate the yeast [PSI(+)] prion. The best characterized of these mutants is the Ssa1 L483W mutant (so-called SSA1-21), which is located in the substrate-binding domain of the protein. However, biochemical analysis of some of these Hsp70 mutants has so far failed to provide major insight into the specific functional changes in Hsp70 that cause prion impairment. In order to gain a better understanding of the mechanism of Hsp70 impairment of prions we have taken an in silico approach and focused on the Escherichia coli Hsp70 ortholog DnaK. Using steered molecular dynamics simulations (SMD) we demonstrate that DnaK variant L484W (analogous to SSA1-21) is predicted to bind substrate more avidly than wild-type DnaK due to an increase in numbers of hydrogen bonds and hydrophobic interactions between chaperone and peptide. Additionally the presence of the larger tryptophan side chain is predicted to cause a conformational change in the peptide-binding domain that physically impairs substrate dissociation. The DnaK L484W variant in combination with some SSA1-21 phenotypic second-site suppressor mutations exhibits chaperone-substrate interactions that are similar to wild-type protein and this provides a rationale for the phenotypic suppression that is observed. Our computational analysis fits well with previous yeast genetics studies regarding the functionality of the Ssa1-21 protein and provides further evidence suggesting that manipulation of the Hsp70 ATPase cycle to favor the ADP/substrate-bound form impairs prion propagation. Furthermore, we demonstrate how SMD can be used as a computational tool for predicting Hsp70 peptide-binding domain mutants that impair prion propagation

Recent advances in spinel ferrite-based magnetic photocatalysts for efficient degradation of organic pollutants

Although spinel ferrite (MFe2O4, M = Zn, Ni, Mn, etc.) has been reported as a promising catalyst, its low photocatalytic activity under visible light greatly restricts its practical application. Spinel ferrite-based photocatalytic composites have exhibited improved efficiency for pollutant degradation, due to interface charge carrier mobility and structural modification. Meanwhile, due to its magnetism and stability, spinel ferrite composite can be easily recycled for long-term utilization, showing its high application potential. In this review, the recent advances in the construction and photocatalytic degradation of spinel ferrite composites are discussed, with an emphasis on the relationship between structural property and photocatalytic activity. In addition, to improve their photocatalytic application, the challenges, gaps and future research prospects are proposed. HIGHLIGHTS The development of spinel ferrite-based photocatalysts was reviewed.; The heterojunction of spinel ferrite and other photocatalysts was reported.; The preparation processes of photocatalytic heterojunctions were summarized.; The mechanism of photocatalytic heterojunctions was illustrated and compared.; Future research suggestions were proposed.

Primate Chaperones Hsc70 (Constitutive) and Hsp70 (Induced) Differ Functionally in Supporting Growth and Prion Propagation in Saccharomyces cerevisiae

Hsp70's are highly conserved essential protein chaperones that assist protein folding and prevent protein aggregation. They have modular structures consisting of ATPase, substrate-binding, and C-terminal domains. Substrate binding and release is regulated by ATP hydrolysis and nucleotide exchange, which in turn are regulated by cochaperones. Eukaryotes have constitutive (Hsc70) and stress-inducible (iHsp70) isoforms, but their functions have not been systematically compared. Using a yeast system to evaluate heterologous Hsp70's we find that primate Hsc70 supported growth but iHsp70 did not. Plant Hsc70 and iHsp70 counterparts behaved similarly, implying evolutionary conservation of this distinction. Swapping yeast and primate Hsp70 domains showed that (i) the Hsc70–iHsp70 distinction resided in the ATPase domain, (ii) substrate-binding domains of Hsp70's within and across species functioned similarly regarding growth, (iii) C-terminal domain function was important for growth, and (iv) Hsp70 functions important for cell growth and prion propagation were separable. Enzymatic analysis uncovered a correlation between substrate affinity and prion phenotype and showed that ATPase and protein-folding activities were generally similar. Our data support a view that intrinsic activities of Hsp70 isoforms are comparable, and functional differences in vivo lie mainly in complex interactions of Hsp70 with cochaperones

Propagation of Saccharomyces cerevisiae [PSI(+)] Prion Is Impaired by Factors That Regulate Hsp70 Substrate Binding

The Saccharomyces cerevisiae [PSI(+)] prion is believed to be a self-propagating cytoplasmic amyloid. Earlier characterization of HSP70 (SSA1) mutations suggested that [PSI(+)] propagation is impaired by alterations that enhance Ssa1p's substrate binding. This impairment is overcome by second-site mutations in Ssa1p's conserved C-terminal motif (GPTVEEVD), which mediates interactions with tetratricopeptide repeat (TPR) cochaperones. Sti1p, a TPR cochaperone homolog of mammalian Hop1 (Hsp70/90 organizing protein), activates Ssa1p ATPase, which promotes substrate binding by Ssa1p. Here we find that in SSA1-21 cells depletion of Sti1p improved [PSI(+)] propagation, while excess Sti1p weakened it. In contrast, depletion of Fes1p, a nucleotide exchange factor for Ssa1p that facilitates substrate release, weakened [PSI(+)] propagation, while overproducing Fes1p improved it. Therefore, alterations of Hsp70 cochaperones that promote or prolong Hsp70 substrate binding impair [PSI(+)] propagation. We also find that the GPTVEEVD motif is important for physical interaction with Hsp40 (Ydj1p), another Hsp70 cochaperone that promotes substrate binding but is dispensable for viability. We further find that depleting Cpr7p, an Hsp90 TPR cochaperone and CyP-40 cyclophilin homolog, improved [PSI(+)] propagation in SSA1 mutants. Although Cpr7p and Sti1p are Hsp90 cochaperones, we provide evidence that Hsp90 is not involved in [PSI(+)] propagation, suggesting that Sti1p and Cpr7p functionally interact with Hsp70 independently of Hsp90

Design and synthesis of a novel fluorescent probe, EuIII-dtpa-bis(adenine), and application for the detection of orotic acid in urine

For detection of orotic acid (OA), a novel fluorescent probe, EuIII-dtpa-bis(adenine), was designed and synthesized based on the complementation base pairing principle. The dtpa-bis(adenine) ligand was characterized by nuclear magnetic resonance spectroscopy (1H NMR and 13C NMR), Fourier transform infrared spectra (FTIR), and elemental analysis. Then, the effects of solution pH values and some coexisting interfering substances on OA detection using EuIII-dtpa-bis(adenine) as a fluorescent probe were investigated. The linear relationship of F0/F and OA concentration in the range of 10–150 μmol/L was obtained, where F0 and F are the fluorescence intensities of EuIII-dtpa-bis(adenine) at 320 nm in the absence and presence of OA, respectively. The calculated limit of detection is about 0.807 μmol/L. The detection mechanism of OA was proposed. In addition, the detection of OA in urine samples has also been studied. It was found that the designed and synthesized fluorescent probe is effective for the detection of OA in urine samples.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Hydrodynamic cavitation-enhanced photocatalytic activity of P-doped TiO2 for degradation of ciprofloxacin: Synergetic effect and mechanism

Hybrid methods with an enhanced oxidation capacity have been proposed for the removal of organic contaminants based on combining hydrodynamic cavitation (HC) with advanced oxidation processes (AOPs). In this study, we utilize the synergetic effect between photocatalytic processes and HC to strengthen ciprofloxacin (CIP) degradation by P-doped TiO2 catalysts. In comparison to a degradation ratio of 20.37 % in HC and 55.7 % in P-TiO2-based photocatalytic processes alone, the CIP degradation ratio reached as high as 90.63 % in HC-assisted photocatalytic processes with the optimal experimental parameters. The mechanic microjets treatment originated from HC make P-TiO2 nano photocatalysts with significantly increased surface area, smaller particle sizes, cleaner surface and improved dispersion, which were found using SEM, TEM, and BET analysis. Possible degradation mechanisms and reaction pathways of CIP during hybrid HC + photocatalytic processes were explored by coupling free radical capture experiments and liquid chromatography-mass spectrometry . This hybrid HC + photocatalytic technique has a potential application in the treatment of antibiotic sewage at the industrial level

Two Novel Colorimetric Probes (5-HMBA-FH and 3-HMBA-FH) Based on Fluorescein for Copper(II) ion Detection

Two novel isomeric colorimetric probes are established for simultaneous determination of copper ions using 2-Hydroxy-5-methoxybenzaldehyde fluorescein hydrazone (5-HMBA-FH) and 2-Hydroxy-3-methoxybenzaldehyde fluorescein hydrazone (3-HMBA-FH). They are synthesized by reacting fluorescein hydrazide with 2-Hydroxy-5-methoxybenzaldehyde and 2-Hydroxy-3-methoxybenzaldehyde, respectively, and then characterized by 1H-NMR, 13C-NMR and Infrared spectrum. In addition of copper ions to the solutions of two novel colorimetric probes can generate the obviously peaks at 498 nm in UV-vis absorption spectra along with a rapid color change from colorless to dark yellow. The detection limits of the method for Cu2+ ion were 3.442 Ă 10-6 mol/L and 3.682 Ă 10-6 mol/L separately, for 5-HMBA-FH and 3-HMBA-FH. The additions of other metal ions hardly affect the copper ions determination. The proposed method was successfully applied to the analysis of Cu2+ ions in various samples. This method possessing high sensitivity, simplicity and minimized interfere will provide a great advantage in detecting copper ions in the environmental, food, medical applications.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Decomposing the Influencing Factors of Industrial Sector Carbon Dioxide Emissions in Inner Mongolia Based on the LMDI Method

Understanding of the influencing factors of industrial sector carbon dioxide emissions is essential to reduce natural and anthropogenic greenhouse gas emissions. In this paper, we applied the Logarithmic Mean Divisia Index (LMDI) decomposition method based on the extended Kaya identity to analyze the changes in industrial carbon dioxide emissions resulting from 39 industrial sectors in Inner Mongolia northeast of China over the period 2003–2012. The factors were divided into five types of effects i.e., industrial growth effect, industrial structure effect, energy effect, energy intensity effect, population effect and comparative analysis of differential influences of various factors on industrial sector. Our results clearly show that (1) Industrial sector carbon dioxide emissions have increased from 134.00 million ton in 2003 to 513.46 million ton in 2012, with an annual average growth rate of 16.097%. The industrial carbon dioxide emissions intensity has decreased from 0.99 million ton/billion yuan to 0.28 million ton/billion yuan. Also, the energy structure has been dominated by coal; (2) Production and supply of electric power, steam and hot water, coal mining and dressing, smelting and pressing of ferrous metals, petroleum processing, coking and nuclear fuel processing, and raw chemical materials and chemical products account for 89.74% of total increased industrial carbon dioxide emissions; (3) The industrial growth effect and population effect are found to be a critical driving force for increasing industrial sector carbon dioxide emissions over the research period. The energy intensity effect is the crucial drivers of the decrease of carbon dioxide emissions. However, the energy structure effect and industrial structure effect have considerably varied over the study years without displaying any clear trend