Lignans from the Bark of Magnolia kobus

The Et₂O‐soluble fraction from the bark of Magnolia kobus led to the isolation of two new lignans, (+)‐(7α,7′α,8α,8′α)‐3′,4,4′,5,5′‐pentamethoxy‐7,9′: 7′,9‐diepoxylignan‐3‐ol ( 1 ) and (+)‐(7α,7′α,8α,8′α)‐4,5‐dimethoxy‐3′,4′‐(methylenedioxy)‐7,9′: 7′,9‐diepoxylignan‐3‐ol ( 2 ), along with five known lignans 3 – 7 . Their structures were established on the basis of various spectroscopic analyses including 1D‐ (¹H, ¹³C, and DEPT) and 2D‐NMR (COSY, NOESY, HMQC, and HMBC) and by comparison of their spectral data with those of related compounds.     

Vapour pressure data of ε-caprolactone, δ-hexalactone,and γ-caprolactone

This work reports new vapour pressure data of ε-caprolactone, δ-hexalactone, and γ-caprolactone. Vapour pressure measurements were carried out over the temperature range of (283 to 343) K using the static method with a differential pressure transducer. Degassing was performed inside the equilibrium cell by freezing and thawing the samples under moderate vacuum (about 50 kPa). For ε-caprolactone and δ-hexalactone vapour pressure values varied in the range of (0.045 to 0.769) kPa and (0.005 to 0.354) kPa, respectively, while for γ-caprolactone a maximum value of 1.367 kPa was found. Experimental vapour pressure data were correlated by the Antoine equation with a good agreement between experiment and model.     

Two-column simulated moving-bed process for binary separation

A two-column simulated moving-bed system has been developed for binary separation. The system combines a flexible node design, robust pump configuration, and cyclic flow-rate modulation to exploit the benefits of simulated counter-current operation. The feasibility of the proposed two-column system is demonstrated on the linear separation of two nucleosides by reversed phase. Emphasis is given to the potentialities of the process compared to single-column batch chromatography with recycling for the same amount of stationary phase. The performance of the proposed two-column process is verified with laboratory-scale experiments and detailed simulations for different difficulties in separation and desorbent-to-feed ratios.     

Mesophilic Acidogenesis of Food Waste-Recycling Wastewater: Effects of Hydraulic Retention Time,pH, and Temperature

The effects of hydraulic retention time (HRT), pH, and operating temperature (T _OP) on the degradation of food waste-recycling wastewater (FRW) were investigated in laboratory-scale hydrolysis/acidogenesis reactors. Response surface analysis was used to approximate the production of volatile organic acids and degradation of volatile suspended solids (VSS), carbohydrate, protein, and lipid with regard to the independent variables (1?≤?HRT?≤?3 days, 4?≤?pH?≤?6, 25?≤?T _OP?≤?45 °C). Partial cubic models adequately approximated the corresponding response surfaces at α?<?5 %. The physiological conditions for maximum acidification (0.4 g TVFA?+?EtOH/g VS_added) and the maximal degradation of VSS (47.5 %), carbohydrate (92.0 %), protein (17.7 %), and lipid (73.7 %) were different. Analysis of variance suggested that pH had a great effect on the responses in most cases, while T _OP and HRT, and their interaction, were significant in some cases. Denaturing gradient gel electrophoresis analysis revealed that Sporanaerobacter acetigenes, Lactobacillus sp., and Eubacterium pyruvivorans-like microorganisms might be main contributors to the hydrolysis and acidogenesis of FRW. Biochemical methane potential test confirmed higher methane yield (538.2 mL CH₄/g VS_added) from an acidogenic effluent than from raw FRW.     

Free Superoxide is an Intermediate in the Production of H2O2 by Copper(I)‐Aβ Peptide and O2

Oxidative stress is considered as an important factor and an early event in the etiology of Alzheimer's disease (AD). Cu bound to the peptide amyloid‐β (Aβ) is found in AD brains, and Cu‐Aβ could contribute to this oxidative stress, as it is able to produce in vitro H₂O₂ and HO^. in the presence of oxygen and biological reducing agents such as ascorbate. The mechanism of Cu‐Aβ‐catalyzed H₂O₂ production is however not known, although it was proposed that H₂O₂ is directly formed from O₂ via a 2‐electron process. Here, we implement an electrochemical setup and use the specificity of superoxide dismutase‐1 (SOD1) to show, for the first time, that H₂O₂ production by Cu‐Aβ in the presence of ascorbate occurs mainly via a free O₂^.? intermediate. This finding radically changes the view on the catalytic mechanism of H₂O₂ production by Cu‐Aβ, and opens the possibility that Cu‐Aβ‐catalyzed O₂^.? contributes to oxidative stress in AD, and hence may be of interest.     

Estimation of Polymerization Conditions Needed to Make Ethylene/1‐olefin Copolymers with Specific Microstructures Using Artificial Neural Networks

Two artificial neural network models (forward and inverse) are developed to describe ethylene/1‐olefin copolymerization with a catalyst having two site types using training and testing datasets obtained from a polymerization kinetic model. The forward model is applied to predict the molecular weight and chemical composition distributions of the polymer from a set of polymerization conditions, such as ethylene concentration, 1‐olefin concentration, cocatalyst concentration, hydrogen concentration, and polymerization temperature. The results of the forward model agree well with those from the kinetic model. The inverse model is applied to determine the polymerization conditions to produce polymers with desired microstructures. Although the inverse model generates multiple solutions for the general case, unique solutions are obtained when one of the three key process parameters (ethylene concentration, 1‐olefin concentration, and polymerization temperature) is kept constant. The proposed model can be used as an efficient tool to design materials from a set of polymerization conditions.

     

Theoretical studies on farnesyl transferase: evidence for thioether product coordination to the active-site zinc sphere

Farnesyltransferase (FTase), an interesting zinc metaloenzyme, has been the subject of great attention in anticancer research over the last decade. However, despite the major accomplishments in the field, some very pungent questions on the farnesylation mechanism still persist. In this study, the authors have analyzed a mechanistic paradox that arises from the existence of several contradicting and inconclusive experimental evidence regarding the existence of direct coordination between the active-site zinc cation and the thioether from the farnesylated peptide product, which include UV-vis spectroscopy data on a Co(2+)-substituted FTase, two X-ray crystallographic structures of the FTase-product complex, and extended X-ray absorption fine structure results. Using high-level theoretical calculations on two models of different sizes, and QM/MM calculations on the full enzyme, the authors have shown that the farnesylated product is Zn coordinated, and that a subsequent step where this Zn bond is broken is coherent with the available kinetic results. Furthermore, an explanation for the contradicting experimental evidence is suggested.     

Solvent control of charge localization in 11-bond bridged dinitroaromatic radical anions

The optical spectra of 4,4'-dinitrostilbene (1-) and 4,4'-dinitrotolane (2-) radical anions show the narrow band widths and partially resolved vibrational structure exhibited by charge-delocalized dinitroaromatic radical anions in the solvents THF, HMPA, and DMPU (dimethylpropyleneurea). Both show the broad, nearly Gaussian-shaped bands found for charge-localized intervalence compounds in DMF, DMSO, and MeCN, with the transition energy of the band maximum, which equals the vertical reorganization energy (lambda) for localized intervalence compounds, increasing in that order. In contrast, 4,4'-dinitroazobenzene (3-) remains delocalized in these solvents, although the line width required to simulate the vibrational structure increases by 200 cm-1 in DMF and 400 cm-1 in MeCN compared to HMPA. The change from localized to delocalized spectra as a function of solvent establishes the transition energy for which delocalization occurs and demonstrates that, as predicted, the Hush method substantially underestimates the electronic coupling for compounds that lie near the borderline.