α-Triazolylboronic Acids: A Promising Scaffold for Effective Inhibitors of KPCs

Boronic acids are known reversible covalent inhibitors of serine β-lactamases. The selectivity and high potency of specific boronates bearing an amide side chain that mimics the β-lactam's amide side chain have been advanced in several studies. Herein, we describe a new class of boronic acids in which the amide group is replaced by a bioisostere triazole. The boronic acids were obtained in a two-step synthesis that relies on the solid and versatile copper-catalyzed azide–alkyne cycloaddition (CuAAC) followed by boronate deprotection. All of the compounds show very good inhibition of the Klebsiella pneumoniae carbapenemase KPC-2, with K_i values ranging from 1 nM to 1 μM, and most of them are able to restore cefepime activity against K. pneumoniae harboring bla_KPC-2. In particular, compound 1 e , bearing a sulfonamide substituted by a thiophene ring, proved to be an excellent KPC-2 inhibitor (K_i=30 nM); it restored cefepime susceptibility in KPC-Kpn cells (MIC=0.5 μg/mL) with values similar to that of vaborbactam (K_i=20 nM, MIC in KPC-Kpn 0.5 μg/mL). Our findings suggest that α-triazolylboronates might represent an effective scaffold for the treatment of KPC-mediated infections.     

Effective Production of (S)-α-Hydroxy ketones: An Reaction Engineering Approach

The use of enzyme engineering for optimisation of an enzymatic reaction can significantly improve lifetime and performance of the biocatalyst. Reaction optimisation is a second powerful tool to enhance yield and enantiomeric excess (ee) of a desired product. In combination, an effective toolbox for biocatalytic process development is given. Previous rational enzyme engineering of thiamine diphosphate-dependent enzymes provided access to unavailable (S)-hydroxy ketones like phenylpropionylcarbinol (PPC) by carboligation of inexpensive aldehydes, but ee was only moderate (89 %) and yields low. In this work, the strong impact of reaction parameters of both, the performance as well as the stereoselectivity of the asymmetric synthesis of PPC catalysed by an (S)-selective Acetobacter pasteurianus pyruvate decarboxylase variant has been assessed. By combining appropriate substrate choice, reaction-, and solvent engineering the ee of the product could be improved from 89 % up to 98 % (S)-PPC. Simultaneously, specific space–time-yield could be increased up to 61-fold, proving the immense impact of suitable reaction condition on both, catalysts productivity and selectivity. Especially avoidance of organic co-solvents, used as substrate solubility enhancers, as well as the exchange of the donor aldehyde by its corresponding α-keto acid, which is decarboxylated to the aldehyde prior to carboligation by the same enzyme, were essential for the enhancement. On the basis of this successful optimisation it could be further shown, that iterative multi-parametric reaction optimisation and especially the application of Pareto charts for visualisation are valuable tools for effective process optimisation.     

Optimization of Enzymatic Synthesis of n-Propyl Acetate (Fruit Flavor Ester) – Effect of the Support on the Properties of Biocatalysts

The present study deals with the optimization of the enzymatic synthesis of n-propyl acetate using response surface methodology (RSM). The biocatalysts were prepared by physical adsorption of lipase from Thermomyces lanuginosus (TLL) on mesoporous hydrophobic supports – poly-hydroxybutyrate (PHB) and poly-methacrylate (PMA) particles. Their catalytic properties were also assayed in the hydrolysis of olive oil emulsion. The biocatalyst TLL–PMA presented the highest immobilization yield (IY, 90.6 ± 2.8%), immobilized protein concentration (36.5 ± 0.4 mg/g of PMA), and catalytic activity in esterification reaction. TLL–PHB was more active in the hydrolysis of olive oil emulsion by a four-fold factor (1240.5 ± 29.2 IU/g of PHB). Maximum acid consumption percentage of 84.3% was observed after 50 min of reaction catalyzed by TLL–PMA using 2000 mM of each reactant (n-propanol and acetic acid) in heptane medium. The purified ester was confirmed by gas chromatography mass spectrometry (GC–MS) analysis. After six consecutive cycles of esterification reaction, the biocatalyst retained around 50% of its initial activity. The results show that PMA may be an interesting support to prepare active biocatalysts in the synthesis of fruit flavor ester by esterification reaction.     

Fine-Grained Ore Minerals – Raw Materials for the Production of Refractories

Refractories and Industrial Ceramics - The new deposit of zircon-rutile-ilmenite sands “Tsentralnoye” in the Rasskazovsky district of the Tambov region, which does not require crushing...     

Immobilization of β-Galactosidase on Monolithic Discs for the Production of Prebiotics Galacto-oligosaccharides

Four different activated methacrylatic monoliths, acting as pore-through-flow membrane reactors in order to reduce enzyme costs and mass-transfer limitations, were characterized as support for immobilization of β-galactosidase to produce galacto-oligosaccharides (GOS). GOS synthesis was studied in different operation modes. A higher affinity of the immobilized enzyme towards the transgalactosylation reaction could be obtained, which results in desired GOS with higher degree of polymerisation. Kinetic models were successfully parametrized forming a basis for process modeling and optimization.     

Promising Antioxidant Activity of Erythrina Genus: An Alternative Treatment for Inflammatory Pain?

The negative impact that oxidative stress has on health is currently known. The complex mechanism of free radicals initiates a series of chain reactions that contribute to the evolution or development of different degenerative disorders. Likewise, these disorders are usually accompanied by inflammatory processes and, therefore, pain. In this sense, reactive oxygen species (ROS) have been shown to promote the nociceptive process, but effective treatment of pain and inflammation still represents a challenge. Over time, it has been learned that there is no single way to relieve pain, and as long as there are no other alternatives, the trend will continue to apply multidisciplinary management, such as promote the traditional use of the Erythrina genus to manage pain and inflammation. In this sense, the Erythrina genus produces a wide range of secondary metabolites, including flavanones, isoflavones, isoflavones, and pterocarpans; these compounds are characterized by their antioxidant activity. Phenolic compounds have demonstrated their ability to suppress pro-oxidants and inhibit inflammatory signaling pathways such as MAPK, AP1, and NFκB. Although there is preclinical evidence supporting its use, the pharmacological effect mechanisms are not entirely clear. Nowadays, there is a fast advancement in knowledge of the disciplines related to drug discovery, but most of nature’s medicinal potential has not yet been harnessed. This review analyzes the decisive role that the Erythrina genus could play in managing inflammatory pain mediated by its compounds and its uses as an antioxidant.     

α-Functional glycopolymers: New materials for (poly)peptide conjugation

The synthesis and characterization of a number of N-(hydroxy)succinimidyl ester-terminated glycopolymers obtained via copper(I)-catalysed living radical polymerisation have been described. Monomers employed were based on protected glucose and galactose, glucofuranoside monomer (1) and galactopyranoside monomer (2). The corresponding polymers featured a relatively narrow molecular weight distribution (PDI=1.10-1.31) and M_n between 4.5 and 10.2 kDa. The protecting groups were removed by treatment with formic acid. Analogous fluorescent polymers have been synthesized by copolymerisation of a monomer which fluoresces in the visible, the fluorescent behaviour of these materials has been investigated. Preliminary experiments have also shown that the terminally functional sugar polymers can react with molecules containing primary amino groups and some triblock ABA copolymers have been prepared.     

Optimization of Propionic Acid Feeding for Production of Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) in Fed-Batch Culture of Ralstonia eutropha

The feeding method of propionic acid for production of poly(3-hydroxybutyrate-co-3-hydro xyvalerate) [P(3HB-co-3HV)] by fed-batch culture of Ralstonia eutropha was optimized to achieve high cell density and high 3HV yield. Effects of different feeding strategies of propionic acid on the production of P(3HB-co-3HV) were investigated. A decline of specific synthesis rate of copolymer and the yield of 3HV unit from propionic acid were observed due to the propionic acid accumulation in culture broth when the feeding solution with high P/G(propionic acid to glucose) ratio was employed. It was further confirmed by controlling propionic acid concentration at a low level in the separate feeding of propionic acid. An optimal feeding strategy was demonstrated to reduce the propionic acid accumulation. The cell concentration, P(3HB-co-3HV) productivity and 3HV unit fraction reached to 163.9kg.m-3, 1.8kg.m-3.h-1, and 10.6%(by mass), respectively, resulting in a yield of 0.33g HV per g propionic acid.     

Polycyclic Compounds. Part V: Reaction of Aminoanthraquinones with α,β-Unsaturated Carbonyl Compounds; Synthesis of Disperse Dyes for Polyester

The reaction of 1-aminoanthraquinone (1) and 1,5-diaminoanthraquinone (2) with α,β-unsaturated ketones in the presence of anhydrous aluminium chloride led to the facile formation of new substituted dihydroanthrapyridine-quinones 3 in a one-stage synthesis. 2-Aminoanthraquinone failed to react under identical conditions. The investigations were extended to the reaction of 1 and 2 with acrylonitrile, methyl acrylate, methyl methacrylate and diethyl ethoxymethylenemalonate to yield the substituted aminoanthraquinones 4. The new compounds were evaluated as disperse dyes on polyester.     

Organometallic Compounds: An Opportunity for Chemical Biology?

Organometallic compounds are renowned for their remarkable applications in the field of catalysis, but much less is known about their potential in chemical biology. Indeed, such compounds have long been considered to be either unstable under physiological conditions or cytotoxic. As a consequence, little attention has been paid to their possible utilisation for biological purposes. Because of their outstanding physicochemical properties, which include chemical stability, structural diversity and unique photo- and electrochemical properties, however, organometallic compounds have the ability to play a leading role in the field of chemical biology. Indeed, remarkable examples of the use of such compounds-notably as enzyme inhibitors and as luminescent agents-have recently been reported. Here we summarise recent advances in the use of organometallic compounds for chemical biology purposes, an area that we define as "organometallic chemical biology". We also demonstrate that these recent discoveries are only a beginning and that many other organometallic complexes are likely to be found useful in this field of research in the near future.     

Titanium–Silica Catalysts for the Production of Fully Epoxidised Fatty Acid Methyl Esters

Grafted titanium-containing mesoporous silica catalysts were used in the selective epoxidation of C-18 unsaturated fatty acid methyl esters (FAMEs). High yields in mono- and diepoxide derivatives were obtained under acid-free reaction conditions with TBHP as oxidant. Ti-MCM-41 showed the best performance in terms of activity over the three FAMEs. Easy separation of the desired products and recycling of the catalyst were demonstrated.     

β-cyclodextrin as a Partial Replacement of Phosphorus Flame Retardant for Poly(Lactic Acid)/Poly(Methyl Methacrylate): A More Environmental Friendly Flame-Retarded Blends

β-Cyclodextrin was used together with isopropylated triaryl phosphate ester flame retardant to improve the flame resistance of poly(lactic acid)/poly(methyl methacrylate). Poly(lactic acid)/poly(methyl methacrylate)/flame-retardant blend (with and without β-cyclodextrin) was evaluated using limiting oxygen index, Underwriters Laboratories-94 vertical burning test, scanning electron microscopy, and thermogravimetric analysis (in O₂ and N₂). The addition of β-cyclodextrin was able to reduce the amount of flame retardant required for poly(lactic acid)/poly(methyl methacrylate) blends to achieve self-extinguishing properties. The poly(lactic acid)/poly(methyl methacrylate)20/flame-retardant/β-cyclodextrin blends achieved Underwriters Laboratories-94, V-0, and limiting oxygen index value of 29.3%. A compact and wide coverage of char layer was formed on the burning surface of poly(lactic acid)/poly(methyl methacrylate)20/flame-retardant/β-cyclodextrin blends.     

Insertion of heme b into the structure of the Cys34-carbamidomethylated human lipocalin α(1)-microglobulin: formation of a [(heme)(2) (α(1)-Microglobulin)](3) complex

α(1)-Microglobulin (α(1)m) is a 26 kDa plasma and tissue protein belonging to the lipocalin protein family. Previous investigations indicate that the protein interacts with heme and suggest that it has a function in heme metabolism. However, detailed characterizations of the α(1)m-heme interactions are lacking. Here, we report for the first time the preparation and analysis of a stable α(1)m-heme complex upon carbamidomethylation of the reactive Cys34 by using recombinantly expressed human α(1)m. Analytical size-exclusion chromatography coupled with a diode-array absorbance spectrophotometry demonstrates that at first an α(1)m-heme monomer is formed. Subsequently, a second heme triggers oligomerization that leads to trimerization. The resulting (α(1)m[heme](2))(3) complex was characterized by resonance Raman and EPR spectroscopy, which support the presence of two ferrihemes, thus indicating an unusual spin-state admixed ground state with S=(3)/(2), (5)/(2).     

Syntheses of diblock copolymers: poly(2-methylpropene)-b-poly(α-amino acid)

Summary Diblock copolymer poly (2-methylpropene)-b-poly (-amino acid) was obtained by polymerization of the corresponding N-caboxy anhydride initiated by a poly (2-methylpropene) bearing a terminal amine in dioxane/CH₂Cl₂ mixture. Copolymers were analyzed by FT IR, ¹H and ¹³C NMR. of the -amino acid segment determined by ¹H NMR fits well with those obtained by a theoretical calculation.     

Unraveling the Early Events of Amyloid-β Protein (Aβ) Aggregation: Techniques for the Determination of Aβ Aggregate Size

The aggregation of proteins into insoluble amyloid fibrils coincides with the onset of numerous diseases. An array of techniques is available to study the different stages of the amyloid aggregation process. Recently, emphasis has been placed upon the analysis of oligomeric amyloid species, which have been hypothesized to play a key role in disease progression. This paper reviews techniques utilized to study aggregation of the amyloid-β protein (Aβ) associated with Alzheimer's disease. In particular, the review focuses on techniques that provide information about the size or quantity of oligomeric Aβ species formed during the early stages of aggregation, including native-PAGE, SDS-PAGE, Western blotting, capillary electrophoresis, mass spectrometry, fluorescence correlation spectroscopy, light scattering, size exclusion chromatography, centrifugation, enzyme-linked immunosorbent assay, and dot blotting.     

Coevolution of the Activity and Thermostability of an ϵ-Keto Ester Reductase for Better Synthesis of an (R)-α-Lipoic Acid Precursor

In this work, we have identified a significantly improved variant (S131Y/Q252I) of the natural ϵ-keto ester reductase CpAR2 from Candida parapsilosis for efficiently manufacturing (R)-8-chloro-6-hydroxyoctanoic acid [(R)-ECHO] through co-evolution of activity and thermostability. The activity of the variant CpAR2_S131Y/Q252I towards the ϵ-keto ester ethyl 8-chloro-6-oxooctanoate was improved to 214 U mg⁻¹—from 120 U mg⁻¹ in the case of the wild-type enzyme (CpAR2_WT)—and the half-deactivating temperature (T₅₀, for 15 min incubation) was simultaneously increased by 2.3 °C in relation to that of CpAR2_WT. Consequently, only 2 g L⁻¹ of lyophilized E. coli cells harboring CpAR2_S131Y/Q252I and a glucose dehydrogenase (GDH) were required in order to achieve productivity similar to that obtained in our previous work, under optimized reaction conditions (530 g L⁻¹ d⁻¹). This result demonstrated a more economical and efficient process for the production of the key (R)-α-lipoic acid intermediate ethyl 8-chloro-6-oxooctanoate.