Studies of arginine-arene interactions through synthesis and evaluation of a series of galectin-binding aromatic lactose esters

Aromatic lactose 2-O-esters were synthesized and used to probe arene-arginine interactions with the galectin family of proteins. They were found to be low microM inhibitors of galectin-1, -3, and -9N-terminal domain and moderate inhibitors of galectin-7, but not inhibitors of galectin-8N-terminal, which lacks an arginine residue close to the critical, esterified lactose 2-O-position. Molecular modeling of galectins in complex with aromatic lactose 2-O-esters, as well as binding studies with a galectin-3 R186S mutant, confirmed that the inhibitory efficiency of the lactose 2-O-esters was due to the formation of strong interactions between the aromatic ester moieties and the arginine guanidinium groups of galectin-1 and -3. An important common feature shared by galectin-1 and -3 was that the arginines formed in-plane ion pairs with two side-chain carboxylates, which resulted in extended planar pi-electron surfaces that did not require solvation by water; these surfaces were ideal for stacking with aromatic moieties of the ligands. The results provide a basis for the design of lectin inhibitors and drugs that exploit interactions with arginine side-chains via aromatic moieties, which are involved in intramolecular protein salt bridges.     

Partially dehydrochlorinated PVC. II. Reactions with dienophiles and hydroxylating agents

Samples of poly(vinylchloride) containing polyene sequences were made by partial dehydrochlorination by alkali in tetrahydrofuran solution, by alkali in dioxane, and thermally in dimethyl-formamide. The reactions of polyene PVC were followed by UV spectrophotometry. Dienophiles were found to have relative reactivities similar to those found in reactions with low molecular-weight dienes. The reaction with maleic anhydride yielded polymers which after hydrolysis contained carboxyl groups. Hydroxylation was made with osmium tetraoxide and performic acid. With the latter reagent the reaction proceeded to complete disappearance of the UV-absorption peaks from trienes and higher polyenes: Gel permeation chromatography analysis showed that hydroxylation could be made with only minor changes in molecular-weight distribution. The formation of gel upon thermal dehydrochlorination in DMF was shown to be due to physical cross linking probably arising by crystallization of polyene segments. The adhesion of the hydroxylated and carboxylated polymers to glass and stainless-steel surfaces was investigated. Films adhered stronger as the degree of dehydrochlorination of the polyene PVC used to make the derivative increased. Samples with long sequences adhered much stronger than those containing short sequences of corresponding degrees of total substitution.     

Purification of Biorefinery Lignin with Alcohols

After hydrothermal pretreatment and enzymatic hydrolysis of wheat straw, a slurry rich in lignin but with a high content of inorganic substances, especially silica, and residual carbohydrates is produced. This slurry was used to develop an ethanol organosolv separation method to produce silica-free lignin fractions. The addition of para toluene sulphonic acid (PTSA) and the use of two alternative long-chain alcohols, oleyl alcohol or nonylphenol, were tested. In every reaction, two lignin fractions were produced and their molecular size and elemental composition were characterized. The yield of each fraction and the change in MWD were studied as a function of temperature and solid to liquid ratio. At 100, 150, and 200°C and with the use of PTSA, high-purity lignin fractions were obtained. After lignin fractionation with nonylphenol, a liquid silica-free product with high lignin content was obtained in yields between 17 and 72%.     

A comparison of partially acetylated nanocellulose,nanocrystalline cellulose,and nanoclay as fillers for high‐performance polylactide nanocomposites

Partially acetylated cellulose nanofibers (CNF) were chemically extracted from sisal fibers and the performance of those CNF as nanofillers for polylactide (PLA) for food packaging applications was evaluated. Three PLA nanocomposites; PLA/CNF (cellulose nanofibers), PLA/CNC (nanocrystalline cellulose), and PLA/C30B (Cloisite^TM 30B, an organically modified montmorillonite clay) were prepared and their properties were evaluated. It was found that CNF reinforced composites showed a larger decrease on oxygen transmission rate (OTR) than the clay‐based composites; (PLA/CNF 1% nanocomposite showed a 63% of reduction at 23°C and 50% RH while PLA/C30B 1% showed a 26% decrease) and similar behavior on terms of water vapor barrier properties with 46 and 43%, respectively of decrease on water vapor transmission rate at 23°C and 50% RH (relative humidity). In terms of mechanical and thermomechanical properties, CNF‐based nanocomposites showed better performance than clay‐based composites without affecting significantly the optical transparency. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43257.     

不同脱毒方法对玉米秸秆水解液酒精发酵的影响

利用湿热预处理(195℃,15 min)后的玉米秸秆水解液,考察了3种不同脱毒方法(中和法、饱和生石灰法和Na2SO3法)对水解液中的抑制剂的去除效果,研究了树干毕赤酵母(Pichia stipitis 58376)对脱毒后的水解液酒精发酵情况.结果表明:玉米秸秆水解液经过3种方法脱毒处理后,醛类抑制荆(糠醛和5-羟甲...     

Kinetic Analysis of Terminal and Unactivated C?H Bond Oxyfunctionalization in Fatty Acid Methyl Esters by Monooxygenase‐Based Whole‐Cell Biocatalysis

The alkane monooxygenase AlkBGT from Pseudomonas putida GPo1 constitutes a versatile enzyme system for the ω‐oxyfunctionalization of medium chain‐length alkanes. In this study, recombinant Escherichia coli W3110 expressing alkBGT was investigated as whole‐cell catalyst for the regioselective biooxidation of fatty acid methyl esters to terminal alcohols. The ω‐functionalized products are of general economic interest, serving as building blocks for polymer synthesis. The whole‐cell catalysts proved to functionalize fatty acid methyl esters with a medium length alkyl chain specifically at the ω‐position. The highest specific hydroxylation activity of 104 U g_CDW⁻¹ was obtained with nonanoic acid methyl ester as substrate using resting cells of E. coli W3110 (pBT10). In an optimized set‐up, maximal 9‐hydroxynonanoic acid methyl ester yields of 95% were achieved. For this specific substrate, apparent whole‐cell kinetic parameters were determined with a V_max of 204±9 U g_CDW⁻¹, a substrate uptake constant (K_S) of 142±17 μM, and a specificity constant V_max/K_S of 1.4 U g_CDW⁻¹ μM ⁻¹ for the formation of the terminal alcohol. The same E. coli strain carrying additional alk genes showed a different substrate selectivity. A comparison of biocatalysis with whole cells and enriched enzyme preparations showed that both substrate availability and enzyme specificity control the efficiency of the whole‐cell bioconversion of the longer and more hydrophobic substrate dodecanoic acid methyl ester. The efficient coupling of redox cofactor oxidation and product formation, as determined in vitro, combined with the high in vivo activities make E. coli W3110 (pBT10) a promising biocatalyst for the preparative synthesis of terminally functionalized fatty acid methyl esters.     

Effect of acid deposition on quantity and quality of dissolved organic matter in soil-water

The aim of this study was to explore how acid deposition may affect the concentration and quality of dissolved organic matter (DOM) in soil-water. This was done by a small-scale acidification experiment during two years where 0.5 × 0.5 m(2) plots were artificially irrigated with water with different sulfuric acid content, and soil-water was sampled using zero-tension lysimeters under the O-horizon. The DOM was characterized using absorbance, fluorescence, and size exclusion chromatography analyses. Our results showed lower mobility of DOM in the high acid treatment. At the same time, there was a significant change in the DOM quality. Soil-water in the high acid treatment exhibited DOM that was less colored, less hydrophobic, less aromatic, and of lower molecular weight, compared to the low acid treatment. This supports the hypothesis that reduction in sulfur deposition is an important driver behind the ongoing brownification of surface waters in many regions.     

ESR studies of the effect of zeolite structures on motional dynamics of NO2

Electron spin resonance (ESR) spectroscopy was used to study the effect of zeolite structure on the motional dynamics of NO₂ adsorbed on the zeolites. The temperature-dependent ESR spectral line shapes were quantitatively analyzed using the slow-motion ESR theory. It was observed that the motional dynamics of NO₂ is strongly dependent on the structure of the zeolite (Beta-type, ZSM-5, mordenite, L-type and ferrierite zeolites). The following important observations were made. (1) In zeolites with similar channel structures, the diffusion rate of NO₂ is proportional to the channel size, and the order of the diffusion rates is Beta-type>ZSM-5>ferrierite and L-type>mordenite. (2) The diffusion of NO₂ is faster in the zeolites with multi-dimensional channels (Beta-type, ZSM-5 and ferrierite) than that in those with uni-dimensional channels (L-type and mordenite).     

Design of a General‐Purpose European Compound Screening Library for EU‐OPENSCREEN

This work describes a collaborative effort to define and apply a protocol for the rational selection of a general‐purpose screening library, to be used by the screening platforms affiliated with the EU‐OPENSCREEN initiative. It is designed as a standard source of compounds for primary screening against novel biological targets, at the request of research partners. Given the general nature of the potential applications of this compound collection, the focus of the selection strategy lies on ensuring chemical stability, absence of reactive compounds, screening‐compliant physicochemical properties, loose compliance to drug‐likeness criteria (as drug design is a major, but not exclusive application), and maximal diversity/coverage of chemical space, aimed at providing hits for a wide spectrum of drugable targets. Finally, practical availability/cost issues cannot be avoided. The main goal of this publication is to inform potential future users of this library about its conception, sources, and characteristics. The outline of the selection procedure, notably of the filtering rules designed by a large committee of European medicinal chemists and chemoinformaticians, may be of general methodological interest for the screening/medicinal chemistry community. The selection task of 200K molecules out of a pre‐filtered set of 1.4M candidates was shared by five independent European research groups, each picking a subset of 40K compounds according to their own in‐house methodology and expertise. An in‐depth analysis of chemical space coverage of the library serves not only to characterize the collection, but also to compare the various chemoinformatics‐driven selection procedures of maximal diversity sets. Compound selections contributed by various participating groups were mapped onto general‐purpose self‐organizing maps (SOMs) built on the basis of marketed drugs and bioactive reference molecules. In this way, the occupancy of chemical space by the EU‐OPENSCREEN library could be directly compared with distributions of known bioactives of various classes. This mapping highlights the relevance of the selection and shows how the consensus reached by merging the five different 40K selections contributes to achieve this relevance. The approach also allows one to readily identify subsets of target‐ or target‐class‐oriented compounds from the EU‐OPENSCREEN library to suit the needs of the diverse range of potential users. The final EU‐OPENSCREEN library, assembled by merging five independent selections of 40K compounds from various expert groups, represents an excellent example of a Europe‐wide collaborative effort toward the common objective of building best‐in‐class European open screening platforms.     

STEAM DRYING OF WOOD CHIPS IN PNEUMATIC CONVEYING DRYERS

ABSTRACT

A model for a pneumatic conveying dryer is presented. Although the main emphasis is put on superheated steam drying of wood chips, it can be used for other porous materials as well

The model includes a comprehensive two-dimensional model for the drying of single wood chips which accounts for the main physical mechanisms occurring in wood during drying. The external drying conditions in a pneumatic conveying dryer were calculated by applying the mass, heat and momentum equations for each incremental step in dryer length. A plug flow assumption was made for the dryer model and the single particle and dryer models were solved in an iterative manner. The non-spherical nature of wood chips were accounted for by measuring the drag and heat transfer coefficients

Model calculations illustrate the complex interactions between steam, particles and walls which occur in a flash dryer. The drying rate varies in a very complex manner through the dryer. The internal resistance to mass transfer becomes very important in The drying of less permeable wood species such as spruce. Two effects were observed as the particle size was increased: firstly the heat transfer rate decreased, and secondly the residence time increased. To some extent, these effects compensate for each other, however, the net result is that larger chips have a higher final moisture content.