Obs Values Research Articles

Chain-Folded Lamellar Stacking Structure of the Crystalline Fraction of Bombyx mori Silk Fibroin with Silk II Form Studied by 2D 13C-13C Homonuclear Correlation NMR Spectroscopy.

The structure of Bombyx mori silk fibroin (SF) is a subject of significant interest due to its remarkable physical properties; however, its atomic-level structure is still not conclusive. We previously proposed a lamellar stacking structure for the crystalline fraction (Cp) with β-turns occurring every eighth amino acid. In this study, we took the following steps: At first, a model of the chain-folded lamellar stacking structure in antipolar and antiparallel β-sheet layers was constructed. Then, dipolar-assisted rotational resonance solid-state NMR spectra were observed to determine the effective internuclear distance (rj,keff) for the uniformly 13C-labeled Cp fraction sample. By comparing the experimentally obtained rj,keff (obs) values with the calculated rj,keff (calc) values from our structural model, a fairly good correlation between the observed and calculated values of the internuclear distances was obtained with a standard deviation of 0.37 Å. This supports the existence of the chain-folded lamellar stacking structure in the SF fiber. These findings contribute to our understanding of the atomic-level structure of SF and its exceptional properties.

Degradation of malachite green by UV/H2O2 and UV/H2O2/Fe2+ processes: kinetics and mechanism.

This work investigated the photochemical degradation of malachite green (MG), a cationic triphenylmethane dye used as a coloring agent, fungicide, and antiseptic. UV photolysis was ineffective in the removal of MG as only 12.35% degradation of MG (10mg/L) was achieved after 60min of irradiation. In contrast, 100.00% degradation of MG (10mg/L) was observed after 60min of irradiation in the presence of 10mM H2O2 by UV/H2O2 at pH 6.0. Similarly, complete removal (100.00%) of MG was observed at 30min of the reaction time by UV/H2O2/Fe2+ employing [MG]0 = 10mg/L, [H2O2]0 = 10mM, [Fe2+]0 = 2.5mg/L, and [pH]0 = 3.0. For the UV/H2O2 process, the degradation efficiency was higher at pH 6.0 than at pH 3.0 as the k obs values were 0.0873 and 0.0690min-1, respectively. However, UV/H2O2/Fe2+ showed higher reactivity at pH 3.0 than at pH 6.0. Chloride and nitrate ions slightly inhibited the removal efficiency of MG by both UV/H2O2 and UV/H2O2/Fe2+ processes. Moreover, three degradation products (DPs) of MG, (i) 4-dimethylamino-benzophenone (DABP), (ii) 4-amino-benzophenone (ABP), and (iii) 4-dimethylamino-phenol (DAP), were identified by GC-MS during the UV/H2O2 treatment. These DPs were found to demonstrate higher aquatic toxicity than the parent MG, suggesting that researchers should focus on the removal of target pollutants as well as their DPs. Nevertheless, the results of this study indicate that both UV/H2O2 and UV/H2O2/Fe2+ processes could be implemented to alleviate the harmful environmental impacts of dye and textile industries.

Kinetics and mechanism of the oxidation of hydrazine with [RuIII(pic)3] in aqueous solution

The kinetics and mechanism of the oxidation of hydrazine by [RuIII(pic)3] (pic- = picolinate anion) were studied spectrophotometrically as a function of hydrazine concentrations at a constant pH of 5.5. The rate of the reaction was followed by monitoring the appearance of the MLCT band of [RuII(pic)3]- at 466 nm. The reaction rate was found to be first-order for Ru(III)-complex concentration. The observed rate constant (k obs) values increased linearly with increase in the hydrazine concentration. The oxidation reaction was studied at varied temperature (20–40 °C). The ΔH≠ (73 ± 3 kJ mol−1 kJ·mol−1) and the negative ΔS≠ (34 ± 7 J·deg−1mol−1) values are consistent with the proposed outer-sphere electron transfer process operative in the oxidation of hydrazine with [RuIII(pic)3]. A working mechanism involving the formation of an active diazene (HN = NH) intermediate followed by its rapid two-electron oxidation by [RuIII(pic)3] in a kinetically inconsequential step producing N2 as sole product is proposed for an overall four-electron oxidation of hydrazine to dinitrogen.

ARRHENIUS KINETICS IN THE EVALUATION OF THE BIOLOGICAL ACTIVITY OF PHARMACEUTICAL TINCTURES

Objective: To develop a method for identifying tinctures by assessing their biological activity at different temperatures based on Arrhenius kinetics. Methods: The tinctures of anti-inflammatory and cardiotonic actions were chosen for the Spitotox-test. Chromatographic ethanol (HPLC grade, 99.8%, Fisher Scientific, UK) and deionized high-resistance water (18.2 MΩ cm, Milli-Q, Millipore) were used to prepare 70% water-alcohol extractant. The dispersity of the infusions and solvents was evaluated by LALLS (Malvern, UK) (micrometer range) and DLS (nanometer range) (Zetasizer Nano ZS, Malvern, UK) methods. Results: The observed (obs) values of activation energy ( °bsEa) of ligand-receptor interactions of infusoria Spirostomum ambiguum and components of tinctures with regard to the extractant: water volume ratio was ranked in descending order of toxicity: motherwort (1:10; 87±13 kJ/mol)>calendula (1:7; 103±18 kJ/mol)>eucalyptus (1:7; 159±5 kJ/mol)>valerian (1:5; 135±6 kJ/mol)>hawthorn (1:4; 113±20 kJ/mol). The found values of activation energy were included in the previously created library for the construction of the correlation diagram « °bsEa-LD50», which allowed to assess the toxicity of tinctures in comparison with other pharmaceutical substances. Conclusion: The method for assessing the biological activity of tinctures was developed by Arrhenius kinetics. The values of activation energy °bsEa of ligand-receptor interactions can be used for the identification of tinctures.

Influence of the Norbornene Anchor Group in Ru-Mediated Ring-Opening Metathesis Polymerization: Synthesis of Bottlebrush Polymers

Ring-opening metathesis polymerization (ROMP) mediated by Grubbs’ third-generation catalyst [G3, (H2IMes)(Cl)2(pyr)2RuCHPh] is widely used to make bottlebrush polymers by polymerization of a macromonomer (MM), typically a low molecular weight polymer functionalized with a norbornene. Termed the grafting-through method, this strategy requires a high degree of living character (“livingness”) to form well-defined bottlebrush polymers. Here, we studied how various anchor groups, the series of atoms connecting the polymerizable norbornene unit to the polymer side-chain, affect livingness in ROMP in a series of exo-norbornene polystyrene MMs. First, we calculated the HOMO and HOMO/LUMO gap energies of MM structures containing five different anchor groups using density functional theory methods, finding that these energies spanned a range of 10 kcal/mol. We then performed kinetics experiments on each MM with target backbone degrees of polymerization (Nbb) of 100 to measure the propagation rate constant (kp,obs) under identical conditions. A positive correlation between the HOMO energy and measured kp,obs values emerged, revealing a 7-fold variation in kp,obs values across the five MMs, suggesting different degrees of livingness among the anchor groups. A series of studies targeting Nbb values ranging from 100 to 2000 further highlighted these differences: The MMs with high kp,obs values reached higher conversions at high target Nbb values with lower dispersities (D̵) than the MMs with lower kp,obs values. Finally, we evaluated the synthesis of bottlebrush pentablock copolymers using the MMs at the two extremes by injecting an MM aliquot into a catalyst solution five consecutive times, allowing for polymerization of each block before the next injection. MM conversion at each step was higher, and the D̵ values for each block were lower for the MM with the highest kp anchor group compared to the lowest kp anchor group. Taken together, these studies highlight how the anchor group dramatically affects both kp and livingness in ROMP, which is crucial for the synthesis of precise bottlebrush (co)polymers.

Influence of the Norbornene Anchor Group in Ru-Mediated Ring-Opening Metathesis Polymerization: Synthesis of Linear Polymers

Ring-opening metathesis polymerization (ROMP) mediated by Grubbs’ first-generation catalyst [G1, (PCy3)2(Cl)2RuCHPh] and Grubbs’ third-generation catalyst [G3, (H2IMes)(Cl)2(pyr)2RuCHPh] can exhibit living characteristics for some monomer classes, most commonly substituted norbornenes. Here, we studied how various anchor groups, the series of atoms connecting the polymerizable norbornene unit to a functional group, affect livingness in ROMP in a series of small-molecule exo-norbornene monomers. We first designed and calculated the HOMO energy of 61 monomers using density functional theory methods, finding that these energies spanned a range of 25 kcal/mol. We then performed kinetics experiments using 1H NMR spectroscopy to measure the propagation rate constant (kp,obs) under identical conditions for eight selected monomers with different anchor groups across the range of HOMO energies. We observed a positive correlation between the HOMO energy or the HOMO/LUMO energy gap and measured kp,obs values for both catalysts, revealing a 30-fold and a 10-fold variation in kp,obs values across the series for G1 and G3, respectively. Interestingly, we observed a plateau for the three monomers with the highest HOMO energies for G3 catalyst, suggesting that above a certain level, the HOMO energy no longer influenced the rate-determining step under the conditions studied here. Chelation studies revealed that only one of the eight monomers showed measurable binding of electron-rich groups on the monomer to the catalyst, but with no apparent effect on kp. Finally, we utilized 1H NMR spectroscopy to measure the rate of catalyst decomposition in the presence of each monomer, a key termination pathway in ROMP. Ultimately, we determined that the anchor group did not substantially affect catalyst decomposition, a proxy for the termination rate constant (kt). In sum, these combined computational and experimental studies collectively demonstrate that livingness in ROMP of exo-norbornene monomers using G1 and G3 catalysts, as measured by relative kp/kt ratios, is primarily controlled by the kp of the anchor group, which is correlated with the HOMO energy.

Revisiting the Parameter Space of Binary Neutron Star Merger Event GW170817

Since the gravitational wave event GW170817 and gamma-ray burst GW170817A, there have been numerous studies constraining the burst properties through analysis of the afterglow light curves. Most agree that the burst was viewed off-axis with a ratio of the observer angle to the jet angle (θ obs/θ j ) between 4 and 6. We use a parameterized model and broadband synchrotron data up to ∼800 days post-merger to constrain parameters of the burst. To reproduce the hydrodynamics of a gamma-ray burst outflow, we use a two-parameter “boosted fireball” model. The structure of a boosted fireball is determined by the specific internal energy, η 0, and the bulk Lorentz factor, γ B ( ∼ 1/θ j ), with shapes varying smoothly from a quasi-spherical outflow for low values of γ B to a highly collimated jet for high values. We run simulations with γ B in the range 1–20 and η 0 in the range 2–15. To calculate light curves, we use a synchrotron radiation model characterized by F peak, ν m , and ν c , and calculate millions of spectra at different times and θ obs values using the boxfit radiation code. We can tabulate the spectral parameter values from our spectra and rapidly generate arbitrary light curves for comparison to data in MCMC analysis. We find that our model prefers a gamma-ray burst with jet energy E j ∼ 1050 erg and with an observer angle of radians and ratio to the jet opening angle of (θ obs/θ j ) = .

Karadeniz Suyunda Yetişen Kalkan (Psetta maxima) Balıklarında Florfenikol’ün Farmakokinetiğinin Belirlenmesi

In this study, it was aimed to determine the kinetics of florfenicol (FF) given intramuscularly and gavage in a single dose (10 mg/kg) in Black Sea Turbot (Psetta maxima), whose growing possibilities were investigated in Turkey in recent years. The study was carried out in black sea water, in closed system pools within the Trabzon Fisheries Central Research Institute. During the experiment, the Black Sea water temperature was 11±1 celsius, the salinity rate was 0.18%, the daily water change was carried out 15 times with a water flow rate of 1 liter/ minute. The amount of oxygen did not fall below 10.02 mg/ml. Experiments were performed on 65 turbot fish (42±2 g), which underwent bacterial and parasitic examination before the trial, including validation (5 specimens) and drug trials (60 specimens). Turbot fish were divided into two groups as 10 mg/kg body weight (c.a) FF administered intramuscularly and gavage. For the validation study, blood taken from turbot fish that were not given medication was used. Determination of plasma FF levels was performed on a high pressure liquid chromatography device (HPLC). Pharmacokinetic analyzes were performed using the win-nonlin pharmacokinetic program according to the non-compartmental model. The results of the validation studies were determined as 96.19, 85.81±0.026, 0.0039 and 0.012 based on Relative Standard Deviation (RSD) %, mean recovery %, LOD and LOQ in ppm, respectively. Tmax (hour), Cmax (mg L-1), Tlast (hour), Clast (mg L-1), AUClast (hour mg L-1), Vz_F_obs (L kg-1) of intramuscular and gavage FF administration groups, Cl_F_obs (L kg h-1) values are 1 and 6, respectively; 6.60 and 5.17; 48 and 48, 2.02 and 1.48, 145.39 and 101.76, 2.54 and 3.64, 0.033 and 0.045. The results of the study showed that the therapeutic dose range of FF can be extended up to 48 hours at 11±1°C in turbot fish, according to the MIC literature information for agents in fish.

HUBUNGAN PENGETAHUAN ORANGTUA TENTANG PEMELIHARAAN KESEHATAN GIGI DAN MULUT DENGAN KEJADIAN KARIES PADA ANAK KELAS V SDN X

Introductin : Maintenance of oral health is one of the efforts to improve health. One reason someone ignores the problems of oral health is the lack of knowledge about dental and oral hygiene. The role of parents is very important in assisting children in maintaining oral health, the role of parents is as caregivers, educators, supporters and supervisors. Dental caries is a disease of dental caries tissue caused by certain microorganisms that have the ability to form acids, especially in the presence of carbohydrates, which will result in a low salivary pH which can cause the dissolution of enamel minerals slowly. Objective : The aim of this study was to determine the relationship of parents' knowledge about dental and oral health care with caries incidence in fifth grade students of SDN Sukakarya 101 Bandung. Method : This type of research is analytical research using cross sectional design. The population in this study were all students of class V SDN Sukakarya 101 Bandung, amounting to 29 people and 29 mothers. Sampling in total sampling of students and parents of class V SDN Sukakarya 101, Arcamanik District of Bandung, which amounted to 29 students and 29 parents. The research instrument used in the form of a questionnaire level of maternal knowledge and observation sheet of dental caries incidence of children. Result : Based on the test decision, it was concluded that there was a significant relationship between parents' knowledge about dental and oral health maintenance with caries incidence in class V students of SDN Sukakarya 101 Bandung with an x2 obs value of 13,241 with p-value = 0,000. Because the observation p-value is smaller than 0.05 (0,000 <0.05). Conclusion : Terdapat hubungan tingkat pengetahuan orang tua dengan kejadian karies pada anak

Chitosan-alginate core-shell-corona shaped nanoparticles of dimethyl fumarate in orodispersible film to improve bioavailability in treatment of multiple sclerosis: Preparation, characterization and biodistribution in rats

Dimethyl fumarate (DMF) is used for the treatment of relapsing forms of multiple sclerosis and causes undesired adverse effects in patients such as gastroenteritis, dyspepsia, low bioavailability, gastritis, nausea and flushing. The aim of this study was to develop oral film containing biocompatible and biodegradable chitosan-alginate nanoparticles of DMF to improve oral bioavailability in multiple sclerosis treatment. The film formulations containing DMF were optimized through design of experiments using full factorial design, and impact of varying levels of independent factors on critical quality attributes of films were studied. The orodispersible film of chitosan-alginate core-shell-corona shaped nanoparticles of DMF was prepared by ionotropic pre-gelation of alginate core followed by chitosan polyelectrolyte complexation, the obtained colloidal nanosuspension was added to the optimized polymer matrix composition by simple process integration and then cast to films by solvent casting process. The films were characterized for their critical quality attributes like pH, tensile strength, disintegration time, in-vitro drug release, ex-vivo permeation study through porcine buccal mucosa and in-vivo pharmacokinetic study in wistar rats. The in-vitro drug release profile from chitosan-alginate core-shell-corona shaped nanoparticles in film evidenced a sustained release with initial 18.39% release in 30 min followed by sustained release up to 6 h in comparison to DMF oral film formulations which released more than 80% drug within 15 min. The in-vivo pharmacokinetic study confirmed that nanoparticles of DMF in orodispersible films (DMF051) were 0.6-fold more bioavailable even at very low drug concentration (2 mg/film) in comparison to conventional oral film formulation (DMF023) (30 mg of drug/film). The Cmax values obtained for DMF023 was 19.21 ± 0.46 μg/ml in comparison to 21.90 ± 0.38 μg/ml for DMF051 and 1.02 μg/ml for drug suspension, Tmax values obtained for DMF023 was 4.00h in comparison to 2.00 h for DMF051, t1/2 values 3.81 ± 0.03 for DMF023 in comparison to 6.59 ± 0.36 for DMF051, AUC 0-t values for DMF023 was 142.02 ± 1.17 μg/ml*h in comparison to 231.49 ± 3.49 μg/ml*h for DMF051 and AUC 0-inf_obs values 153.67 ± 1.27 μg/ml*h for DMF023 in comparison to 251.21 ± 3.48 μg/ml*h for DMF051. The study indicates enhanced bioavailability from this promising dosage form, prompting dose reduction and reduced side effects.

Simultaneous removal of phenol and chromium reduction from the aqueous solution with photocatalytic process in the presence of ZnO-activated carbon fibre composite

ABSTRACT Simultaneous removal of phenol and chromium Cr(VI) reduction in aqueous solution was evaluated using ZnO-activated carbon fibre (ZnO/ACF) composite in a photoreactor. ZnO/ACF composite was synthesised by the hydrothermal method, and its characteristics were characterised by techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy and Fourier transform infrared analysis. The effect of some operational factors such as pH, composite dosage, initial concentrations and contact time on the removal efficiency was studied through the photocatalytic runs using ZnO/ACF composite. SEM analysis demonstrated that the flowerlike structure of ZnO adhered successfully to the ACF surface. XRD analysis also confirmed patterns for the wurtzite hexagonal phase of ZnO and ACF for ZnO/ACF composite. Results of photocatalytic experiments showed that 20 mg/L of Cr(VI) and 20 mg/L of phenol were completely removed in acidic conditions with 1.5 g/L of ZnO/ACF after 45 and 50 min, respectively. With an increase in the concentration of pollutant from 5 to 20 mg/L, the k obs values decreased from 0.0512 to 0.0059 for phenol and decreased from 0.0489 to 0.0057 for chromium, while the electrical energy per order (E E0) increased from 99.77 to 856.15 kWh/m3for phenol and increased from 93.78 to 847.18 kWh/m3 for chromium. The use of ZnO/ACF composite is considerably improving the performance of the photocatalytic process. Therefore, ZnO/ACF/ultravioletcould be recommended as an effective process to simultaneously removal of phenol and Cr(VI) reduction in toxic wastewater.

The Effectiveness of Creative Problem Solving (CPS) Learning Model on Divergent Thinking Skills

<span lang="EN-US">This study has a goal to determine the effectiveness of the CPS learning process in thematic learning and the effectiveness of CPS on students' divergent thinking skills. The exploratory sequential mixed method was used in this study. The study participants were 184 fifth-grade students at public elementary schools in Laweyan District. Test instruments, observation sheets, and documentation were used to collect research data. The content and construct validations were used to test the validity of the test instrument, while the observation sheet and documentation were only tested for their content validity. This study went through two stages of data analysis, namely quantitative tests (normality, homogeneity, balance, hypothesis, and post-ANOVA tests) and qualitative analysis using interactive analysis methods through data reduction, data display, and conclusion drawing. The results of the study describe the calculation of the hypothesis test with an F obs value of 18.23 which is higher than the F table value of 3.02 with a significance level of 0.05. The average score of students who learn using the CPS model is 69.36 while students who use the DI model obtain an average score of 63.43. Students demonstrate every indicator of divergent thinking skills (fluency, flexibility, originality, and elaboration) during the learning process with the CPS model. Therefore, it can be concluded that the CPS learning model is more effective than DI to improve students' divergent thinking skills. The results of this study can be applied to improve the divergent thinking skills of elementary school students. </span>

Effects of rifampicin on plasma pharmacokinetics of tulathromycin in goats.

We investigated the pharmacokinetic profile of co-administration of tulathromycin with rifampicin. Healthy male goats were allocated to three groups (n=8) as Group A (single dose 2.5mg/kg tulathromycin s.c.), B (10mgkg-1 day-1 rifampicin p.o. daily for 7days and single dose 2.5mg/kg tulathromycin s.c. on 8th day),andC (10mgkg-1 day-1 rifampicin p.o. daily for 21days and single dose 2.5mg/kg tulathromycin s.c. on 8th day). Blood samples were collected from jugular veins. Plasma samples were analyzed for tulathromycin by liquid chromatography-mass spectrometry (LC-MS/MS). Peak plasma concentration (Cmax ) values of tulathromycin were 1,390±173, 958±106, and 807±116ng/ml in groups A, B, and C, respectively. Cmax value of group A was greater than other groups (p<.05). Mean residence time based on time zero to last sample time (MRTlast ) values were 52±1, 56±4 and 66±4hr in A, B, and C groups, respectively whereas mean residence time based on time zero extrapolated to infinity (MRTINF_obs ) values were 69±4, 85±5, and 86±4hr, respectively. MRTlast and MRTINF_obs values were greater in B and C groups than group A (p<.05). These findings suggest that rifampicin administration may change several pharmacokinetic parameters of tulathromycin in goats.

Efficient soluble and polymer cross linked insoluble poly-4-vinyl pyridine metal(V) chloride catalysts for esterification of butanol with acetic acid

New soluble and insoluble Ta, Mo and Sb pentachloride complex catalysts have been prepared using pyridine and polymer supported cross-linked (poly-4-vinyl pyridine) beads (PSCPVP), respectively. The prepared catalysts are characterized with FTIR, SEM, EDAX, CHN and TGA. The catalytic activities of these catalysts have been examined for esterification of acetic acid with butanol through gas chromatographic technique. The soluble complex catalyst show better activity than the insoluble catalyst, but it suffers from recovery and recyclability. The insoluble catalysts maintain stability up to three recycle times. From the k obs values, it is found that all the soluble catalysts of Py-MCl 5 , M=Ta, Mo &amp; Sb (k obs =7.26, 5.48 &amp; 1.47×10 3 min -1 ) showed higher catalytic activity than the insoluble PSCPVP-MCl 5 (k obs =5.18, 2.24 &amp; 0.87 x10 3 min -1 ) , but the latter catalysts are superior to the former in terms of recyclability. The catalytic activity of soluble Py-TaCl 5 , Py-MoCl 5 , Py-SbCl 5 catalyst is found to be 1.40, 2.44 and 1.68 times higher than PSCPVP-TaCl 5 , PSCPVP-MoCl 5 and PSCPVP-SbCl 5 , respectively. PSCPVP-TaCl 5 catalyst is found to be the superior most catalyst among the three catalysts. Further, these catalysts can be used in column batch reactors to conduct the reaction in continuous mode.

Oxidation of tetracycline and oxytetracycline for the photo-Fenton process: Their transformation products and toxicity assessment

Advanced oxidation processes have gained significant attention for treating tetracycline (TC) and oxytetracycline (OTC), however, their oxidation using the photo-Fenton process has not been sufficiently studied. Although degradations of TC and OTC were enhanced by increasing H2O2 and Fe2+ within the ranges investigated (H2O2 = 20–50 mg/L and Fe = 1–10 mg/L) under UV irradiation, further experiments for the photo-Fenton process were conducted with 20 mg/L of H2O2 and 5 mg/L of Fe2+ to balance efficiency and cost. The photo-Fenton process (UV/H2O2/Fe2+) was shown to be more effective to remove TC and OTC than H2O2, ultraviolet (UV), and UV/H2O2 at the same doses of oxidants. Inorganic anions and cations were shown to inhibit the degradation of TC and OTC during the photo-Fenton process, in the following order: HPO42- > HCO3− ≫ SO42- > Cl− and Cu2+ ≫ Ca2+ > Na+. The TC and OTC degradation are generally improved by increasing pH, which is opposite to the kpCBA,obs values, caused by increasing the deprotonation degree of TC and OTC. Four and nine transformation products of TC and OTC, respectively, were detected over the treatment period. Among the transformation products, m/z 443.14 (C22H22N2O8) formed during TC degradation, and m/z 433.16 (C20H20N2O9) and m/z 415.15 (C20H18N2O8) formed during OTC degradation, were reported for the first time. Vibrio fischeri toxicity assessment indicated that the inhibition ratio was decreased with a decreasing TC concentration, while, OTC transformation lead to higher toxicity. The product (m/z 477.15b) was determined to be the compound causing toxicity during degradation of OTC by using the quantitative structure activity relationship (QSAR). This toxic transformation product caused higher inhibition ratios than its parental compound (OTC), but its further oxidization resulted in decreasing the inhibition ratios.

Corrigendum: Specific Residues Expand the Substrate Scope and Enhance the Regioselectivity of a Plant O‐Methyltransferase

This is a corrigendum for the article “Specific residues expand the substrate scope and enhance the regioselectivity of a plant O-methyltransferase”, published in ChemCatChem 2019, 11 (14), 3227-3233, DOI: 10.1002/cctc.201900606. After publication, the authors noticed an error in the calculation of the observed kinetic constants in Table 1, during the transformation of the kcat,obs values from min−1 to s−1. The corrections in Table 1 are as follows: Substrate KM,obs [mM] kcat,obs [s−1] kcat,obs/KM,obs [s−1 ⋅ mM−1] 1b 0.0058±0.0003 0.133 ± 0.002 23 3a 0.719±0.035 0.0177 ± 0.0003 0.025 4a 0.119±0.014 0.063 ± 0.003 0.53 The authors apologize for this oversight.

Structural Analyses of Alanine Trimer and Tetramer Crystals with Antiparallel and Parallel β-Sheet Structures Using Solid-State 1H Spin-Diffusion 2D Correlation NMR Spectroscopy.

Poly-l-alanine (PLA) sequences are key elements of the crystalline domains of spider dragline and wild silkworm silks. In the present work, 1H spin-diffusion two-dimensional (2D) correlation NMR spectra were observed for selectively deuterated (Ala)3 and (Ala)4 crystals to develop the analytical method for the structure of PLA sequences. The build-up curves of the cross peaks for three kinds of 1H pairs in selectively deuterated (Ala)3 and (Ala)4 crystals were observed to obtain spin-diffusion rate constant k j, k from relaxation master equations P i, j(τm). The k j, k values subsequently lead to effective interproton distance r j, keff (obs) values for individual proton-proton pairs, which include intra- and intermolecular contributions. The r j, keff (obs) values were compared to r j, keff (calc) values obtained from the experimentally determined atomic coordinates of antiparallel (AP) β-sheet (Ala)3 and (Ala)4 and parallel (P) β-sheet of (Ala)3 and (Ala)4 crystals. The agreement between the r j, keff (obs) and r j, keff (calc) values was good for AP β-sheet (Ala)3 and (Ala)4 crystals but poor for P β-sheet (Ala)3 and (Ala)4 crystals. These deviations were obtained from the interproton distances of the interchain contributions due to different packing arrangements. The packing arrangements of the PLA region are important when considering the relevant structure and the mechanical properties of silks.

Correction to: Sequence-specific backbone resonance assignments and microsecond timescale molecular dynamics simulation of human eosinophil-derived neurotoxin.

After publication of this article, the authors noticed that a 15N-13C dimension error was unwillingly coded in the 3D NMR spectrum "fid.com" processing script used to perform backbone assignments for this enzyme. The authors noticed that some OBS, CAR and LAB values in the "fid.com" had been switched in the y and z dimensions, probably resulting from a wrong NMRPipe selection when reading the Varian NMR experimental parameters. They have carefully re-processed, re-analyzed, re-assigned, in addition to checking all scripts to evaluate the extent of this processing error on the published assignments. Authors determined that the "fid.com" error resulted in a significant number of incorrect backbone resonance assignments, requiring us to issue corrections in Figs. 2, 3 and 4 of this published manuscript, in addition to Table S1. New versions of these figures and table are provided below. The corresponding BMRB entry has also been revised. The authors note that these modifications do not change the global message, conclusions, and molecular dynamics simulations presented in this article. The authors are grateful to David N. Bernard (INRS) for help with finding and correcting these errors.

Ligand-Induced Conformational Changes in HSP90 Monitored Time Resolved and Label Free-Towards a Conformational Activity Screening for Drug Discovery.

Investigation of protein–ligand interactions is crucial during early drug‐discovery processes. ATR‐FTIR spectroscopy can detect label‐free protein–ligand interactions with high spatiotemporal resolution. Here we immobilized, as an example, the heat shock protein HSP90 on an ATR crystal. This protein is an important molecular target for drugs against several diseases including cancer. With our novel approach we investigated a ligand‐induced secondary structural change. Two specific binding modes of 19 drug‐like compounds were analyzed. Different binding modes can lead to different efficacy and specificity of different drugs. In addition, the k obs values of ligand dissociation were obtained. The results were validated by X‐ray crystallography for the structural change and by SPR experiments for the dissociation kinetics, but our method yields all data in a single and simple experiment.

Standard Gibbs Energy of Metabolic Reactions: III The 3-Phosphoglycerate Kinase Reaction.

The glycolytic pathway is one of the most studied metabolic pathways to date. This work focuses on determining the standard Gibbs energy of reaction (ΔRg0) of the first adenosine triphosphate-yielding reaction step of glycolysis, namely, the 3-phosphoglycerate kinase (PGK) reaction. Trustworthy values of ΔRg0 are required for thermodynamic approaches to determine single reaction conversions or even fluxes of metabolic reactions. In literature, the observed ΔRg0,obs values are usually determined directly from the experimental equilibrium composition data without accounting for the nonideality of the reaction mixture. That is the reason why the observed ΔRg0,obs values do not present consistent standard data as they are a function of the concentration, pH, and pMg. In this work, a combination of experimentally determined equilibrium composition data and activity coefficients of the reacting agents was used to determine ΔRg0 values for the temperatures 303, 313, and 323 K at pH 7. The activity coefficients were predicted with the thermodynamic model electrolyte perturbed-chain statistical associating fluid theory (ePC-SAFT). The ePC-SAFT parameters were taken from literature or fitted to new experimental osmotic coefficients. At 313.15 K, a value for ΔRg0 of −16.2 ± 0.2 kJ/mol was obtained. This value is about 4 kJ/mol less negative than what is usually considered as an accepted standard value. The reason behind this discrepancy was found to be the activity coefficients of the reacting agents, which dramatically influence the equilibrium position of the PGK reaction. On the basis of the temperature-dependent ΔRg0 values, the standard enthalpy of reaction was determined and found to be ΔRh0 = −49 ± 9 kJ/mol.