Conversion of ß-1,6-Glucans to Gentiobiose using an endo-ß-1,6-Glucanase PsGly30A from Paenibacillus sp. GKG.

A plethora of di- and oligosaccharides isolated from the natural sources are used in food and pharmaceutical industry. An enzymatic hydrolysis of fungal cell wall ß-glucans is a good alternative to produce the desired oligosaccharides with different functionalities, such as the flavour enhancer gentiobiose. We have previously identified PsGly30A as a potential yeast cell wall degrading ß-1,6-glycosidase. The aim of this study is to characterise the PsGly30A enzyme, a member of the GH30 family, and to evaluate its suitability for the production of gentiobiose from ß-1,6-glucans. An endo-ß-1,6-glucanase PsGly30A encoding gene from Paenibacillus sp. GKG has been cloned and overexpressed in Escherichia coli. The recombinant enzyme has been active towards pustulan and yeast ß-glucan, but not on laminarin from the Laminaria digitata, confirming the endo-ß-1,6-glucanase mode of action. The PsGly30A shows the highest activity at pH 5.5 and 50 °C. The specific activity of PsGly30A on pustulan (1262±82 U/mg) is among the highest reported for GH30 ß-1,6-glycosidases. Moreover, gentiobiose is the major reaction product when pustulan, yeast ß-glucan or yeast cell walls have been used as a substrate. Therefore, PsGly30A is a promising catalyst for valorisation of the yeast-related by-products.

Palladium-Catalyzed Synthesis of Cyclopropylthiophenes and Their Derivatization.

The cyclopropylthiophene moiety has attracted the attention of the scientific community for its potential pharmaceutical applications. However, synthesis of the compounds containing this framework remains challenging, has rarely been reported and remains unresolved. Here we provide optimized syntheses for cyclopropylthiophenes and their derivatives, containing carbonyl, acetyl, carboxylic acid, methyl carboxylate, nitrile, bromide and sulfonyl chloride moieties.

In Vitro Antioxidant and Prooxidant Activities of Red Raspberry (Rubus idaeus L.) Stem Extracts.

Leaves and stems of red raspberry (Rubus idaeus) are used in Lithuanian folk medicine. Healing properties of raspberry are related to the content of bioactive compounds, mainly polyphenols. Extracts of raspberry leaves contained higher total phenolic content (TPC) (1290 mg/L, expressed in gallic acid equivalent) compared to that in extracts of stems or peeled bark (up to 420 mg/L and 598 mg/L, respectively). To find out whether the collection time of herbal material was critical for the properties of the extracts, the stems were collected at different times of the year. TPC in the extracts depended more on extraction conditions rather than on the sampling time. Antioxidant activity of raspberry stem and bark extracts tested by spectrophotometric (DPPH● scavenging) and electrochemical (cyclic and differential pulse voltammetry) assays correlated with TPC. DPPH radical scavenging activity values for stem, leaf, and bark extracts were as follows: ≤1.18 ± 0.07, 1.63 ± 0.10, and ≤1.90 ± 0.04 (mmol/L, TROLOX equivalent), respectively. Assessed electrochemically, hydrogen peroxide-scavenging activity of extracts was independent on TPC. The latter activity was related to the presence of some protein in the extract as revealed by gel electrophoresis. Prooxidant activity of raspberry stem extracts was dependent on solution pH and temperature.

Electrochemical Shell-Isolated Nanoparticle-Enhanced Raman Spectroscopy of Imidazole Ring Functionalized Monolayer on Smooth Gold Electrode.

The imidazole ring (Im) of histidine side chains plays a unique role in the function of proteins through covalent bonding with metal ions and hydrogen bonding interactions with adjusted biomolecules and water. At biological interfaces, these interactions are modified because of the presence of an electric field. Self-assembled monolayers (SAMs) with the functional Im group mimic the histidine side chain at electrified interfaces. In this study, we applied in-situ shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS) to probe the structure and hydrogen bonding of Im-functionalized SAM on smooth Au at the electrochemical interface. The self-assembly of molecules on the Au induced the proton shift from N1 atom (Tautomer-I), which is the dominant form of Im in the bulk sample, to N3 atom (Tautomer-II). The impact of electrode potential on the hydrogen bonding interaction strength of the Im ring was identified by SHINERS. Temperature-Raman measurements and density functional theory (DFT) analysis revealed the spectral marker for Im ring packing (mode near 1496-1480 cm-1) that allowed us to associate the confined and strongly hydrogen bonded interfacial Im groups with electrode polarization at -0.8 V. Reflection adsorption IR (RAIR) spectra of SAMs with and without Im revealed that the bulky ring prevented the formation of a strongly hydrogen bonded amide group network.

Reflection Absorption Infrared Spectroscopy Characterization of SAM Formation from 8-Mercapto-N-(phenethyl)octanamide Thiols with Phe Ring and Amide Groups.

Multifunctional amide-containing self-assembled monolayers (SAMs) provide prospects for the construction of interfaces with required physicochemical properties and distinctive stability. In this study, we report the synthesis of amide-containing thiols with terminal phenylalanine (Phe) ring functionality (HS(CH2)7CONH(CH2)2C6H5) and the characterization of the formation of SAMs from these thiols on gold by reflection absorption infrared spectroscopy (RAIRS). For reliable assignments of vibrational bands, ring deuterated analogs were synthesized and studied as well. Adsorption time induced changes in Amide-II band frequency and relative intensity of Amide-II/Amide-I bands revealed two-state sigmoidal form dependence with a transition inflection points at 2.2 ± 0.5 and 4.7 ± 0.5 min, respectively. The transition from initial (disordered) to final (hydrogen-bonded, ordered) structure resulted in increased Amide-II frequency from 1548 to 1557 cm-1, which is diagnostic for a strongly hydrogen-bonded amide network in trans conformation. However, the lateral interactions between the alkyl chains were found to be somewhat reduced when compared with well-ordered alkane thiol monolayers.

Allelopathic Activity of Canadian Goldenrod (Solidago canadensis L.) Extracts on Seed Germination and Growth of Lettuce (Lactuca sativa L.) and Garden Pepper Cress (Lepidium sativum L.).

Native to N. America, Canadian goldenrod (Solidago canadensis L.) was introduced to Europe as an ornamental plant and quickly spread here and in other parts of the world. The rapid spread of the plant is due to several reasons: phenotypic plasticity, broad climatic tolerance, propagation via underground rhizomes and seeds that mature in large numbers, etc. Additionally, the success of Canadian goldenrod's invasion is determined by its allelochemicals that affect seed germination, root formation and whole growth of nearby plants. Allelopathy of various extracts and essential oils (EOs) of S. canadensis on seed germination and growth of lettuce (Lactuca sativa L.) and garden pepper cress (Lepidium sativum L.) was evaluated and compared with other Solidago species (S. virgaurea, S. × niederederi) collected from the same growing locality in Lithuania. Soil characteristics (conductivity, pH and major elements) of the collecting site were determined. Aqueous flower extracts of all studied Solidago species showed the highest inhibitory effect on model plants. Canadian goldenrod leaf water/diethyl ether extract showed highest inhibitory effect in all relative concentrations (1.0; 0.1; 0.01) suppressing growth of L. sativa (from 0 to 2.3 mm compared with 22.7 mm for control samples) and L. sativum (from 0.5 to 16.8 mm compared with 35.3 mm in control). It was noticed that garden pepper cress was more susceptible to Solidago spp. inhibitory effects than lettuce. S. canadensis root EOs comprised mainly of limonene (35.0%) and ß-pinene (26.2%) and inflorescence oils containing α-pinene (21.6%), germacrene D (15.1%), limonene (10.2%) and lupenyl acetate (9.8%) exhibited the highest inhibitory effect on lettuce and garden pepper cress growth. Relative germination and vigor index of model plants was conducted. Chemical composition of extracts and EOs was determined by HPLC/DAD/TOF and GC/MS techniques.

Derivatives of Pyridazine with Phenoxazine and 9,9-Dimethyl-9,10-dihydroacridine Donor Moieties Exhibiting Thermally Activated Delayed Fluorescence.

Two compounds based on pyridazine as the acceptor core and 9,9-dimethyl-9,10-dihydroacridine or phenoxazine donor moieties were designed and synthesized by Buchwald-Hartwig cross-coupling reaction. The electronic, photophysical, and electrochemical properties of the compounds were studied by ultraviolet-visible spectroscopy (UV-vis), photoluminescence spectrometry, differential scanning calorimetry, thermogravimetric analysis, and cyclic voltammetry. The compounds are characterized by high thermal stabilities. Their 5% weight loss temperatures are 314 and 336 °C. Complete weight loss of both pyridazine-based compounds was detected by TGA, indicating sublimation. The derivative of pyridazine and 9,9-dimethyl-9,10-dihydroacridine is capable of glass formation. Its glass transition temperature is 80 °C. The geometries and electronic characteristics of the compounds were substantiated using density functional theory (DFT). The compounds exhibited emission from the intramolecular charge transfer state manifested by positive solvatochromism. The emission in the range of 534-609 nm of the toluene solutions of the compounds is thermally activated delayed fluorescence with lifetimes of 93 and 143 ns, respectively.

Electrochemical SEIRAS Analysis of Imidazole-Ring-Functionalized Self-Assembled Monolayers.

An essential amino acid, histidine, has a vital role in the secondary structure and catalytic activity of proteins because of the diverse interactions its side chain imidazole (Im) ring can take part in. Among these interactions, hydrogen donating and accepting bonding are often found to operate at the charged interfaces. However, despite the great biological significance, hydrogen-bond interactions are difficult to investigate at electrochemical interfaces due to the lack of appropriate experimental methods. Here, we present a surface-enhanced infrared absorption spectroscopy (SEIRAS) and density functional theory (DFT) study addressing this issue. To probe the hydrogen-bond interactions of the Im at the electrified organic layer/water interface, we constructed Au-adsorbed self-assembled monolayers (SAMs) that are functionalized with the Im group. As the prerequisite for spectroelectrochemical investigations, we first analyzed the formation of the monolayer and the relationship between the chemical composition of SAM and its structure. Infrared absorption markers that are sensitive to hydrogen-bonding interactions were identified. We found that negative electrode polarization effectively reduced hydrogen-bonding strength at the Im ring at the organic layer-water interface. The possible mechanism governing such a decrease in hydrogen-bonding interaction strength is discussed.

Derivatives of Imidazole and Carbazole as Bifunctional Materials for Organic Light-Emitting Diodes.

New derivatives of carbazole and diphenyl imidazole for potential multiple applications were synthesized and investigated. Their properties were studied by thermal, optical, photophysical, electrochemical, and photoelectrical measurements. The compounds exhibited relatively narrow blue light-emission bands, which is favorable for deep-blue electroluminescent devices. The synthesized derivatives of imidazole and carbazole were tested as fluorescent emitters for OLEDs. The device showed deep-blue emissions with CIE color coordinates of (0.16, 0.08) and maximum quantum efficiency of 1.1%. The compounds demonstrated high triplet energy values above 3.0 eV and hole drift mobility exceeding 10-4 cm2/V·s at high electric fields. One of the compounds having two diphenyl imidazole moieties and tert-butyl-substituted carbazolyl groups showed bipolar charge transport with electron drift mobility reaching 10-4 cm2/V·s at electric field of 8 × 105 V/cm. The synthesized compounds were investigated as hosts for green, red and sky-blue phosphorescent OLEDs. The green-, red- and sky-blue-emitting devices demonstrated maximum quantum efficiencies of 8.3%, 6.4% and 7.6%, respectively.

Conversion of fatty acid methyl esters into dibasic esters by metathesis and their lubricant properties.

Biodiesel plants are struggling to find value added applications for fatty acid methyl esters (FAME). One option for FAME valorization would be dibasic esters, which can be transesterified with 2-ethylhexyl (2EH) or other alcohols to produce lubricant basestocks and achieve the most widespread viscosity grades VG46 and VG32. Biocatalytic, metathesis and other synthetic pathways are available to produce dibasic esters. Using a ruthenium-based catalyst, methyl oleate was converted into monounsaturated dibasic ester by metathesis and reached VG22 after transesterification with 2EH in this investigation. Synthesized 2EH esters of other dibasic acids showed distinct viscometric trends. Their correlation implied that FAME from gondoic and erucic acids should result in VG32 and VG46 respectively, if converted into 2EH dibasic esters. Pour points demonstrated excellent low temperature fluidity and resistance to heat thinning when monounsaturation was retained. Oxidative stability properties remained acceptable, volatility was lower than that of VG46 mineral oils. Mixed alcohols, acids and esters can also be used for meeting VG specifications or achieving higher biobased contents. Currently petrochemical ester basestocks dominate in high performance hydraulic fluids (HF). However, fractionation of FAME into high-erucic/gondoic esters in biodiesel plants can produce a valuable biobased feedstock for large volume manufacture of HF and other lubricants.

Inerolysin and vaginolysin, the cytolysins implicated in vaginal dysbiosis, differently impair molecular integrity of phospholipid membranes.

The pore-forming toxins, inerolysin (INY) and vaginolysin (VLY), produced by vaginal bacteria Lactobacillus iners and Gardnerella vaginalis were studied using the artificial cholesterol-rich tethered bilayer membranes (tBLMs) by electrochemical techniques. The electrochemical impedance spectroscopy (EIS) of tBLMs attested for the toxin-induced impairment of the integrity of phospholipid membranes. This observation was in line with the atomic force microscopy data demonstrating formation of oligomeric protein assemblies in tBLMs. These assemblies exhibited different morphologies: VLY mostly formed complete rings, whereas INY produced arciform structures. We found that both EIS (membrane damage) and the surface plasmon resonance (protein binding) data obtained on tBLMs are in-line with the data obtained in human cell lysis experiments. EIS, however, is capable of capturing effects inaccessible for biological activity assays. Specifically, we found that the INY-induced damage of tBLMs is nearly a linear function of membrane cholesterol content, whereas VLY triggered significant damage only at high (50 mol%) cholesterol concentrations. The observed differences of INY and VLY activities on phospholipid membranes might have clinical importance: both toxin-producing bacteria have been found in healthy vagina and dysbiosis, suggesting the need for adaptation at different vaginal conditions. Our results broaden the possibilities of application of tBLMs in medical diagnostics.

Effect of 1-acyl-5,6-dialkoxy-2-alkylthiobenzo[d] imidazoles on the action potential duration and isometric contraction in guinea pig atrium activated by carbachol and in guinea pig heart papillary muscles.

BACKGROUND: Studies have shown that some benzo[d]imidazole derivatives (1-(5,6-dimethoxy-2-methylthio-1H-benzo[d]imidazol-1-yl)-1-ethanone (1), 1-(6-ethylthio-5H[1,31dioxolo[4',5':4,5] benzo[d]imidazol-5-yl)-1-propanone (2), 1-(2-ethylthio-6,7-dihydro-1H[1,4]dioxino [2:3':4,5]benzo[d]imidazol-1-yl)-1-pro-panone (3) and 2,3,9,10-tetrahydro-8H [1,4]dioxino[2' 3":4',5']benzo[4,5]imid-azo[2,1-b][1,3]thiazin-10-one (4)) possess strong cardiotonic activity. The goal of this study was to investigate the effect of compounds 1-4 on the action potential (AP) duration and contractile force in guinea pig atrium activated by carbachol and in guinea pig heart papillary muscles. METHODS: The experiments were carried out on the guinea pig papillary muscles and atrium. Isometric contraction and transmembrane potential were recorded using a force transducer and standard microelectrode technique. RESULTS: Compounds 1-4 exerted a positive inotropic effect in a dose-dependent manner on the electrically driven left atrium and papillary muscles, more pronounced in atrium. In response to 1 micromol/L carbachol the AP duration at a 90 % repolarization in atrium shortened more than 70 %, the isometric contraction decreased to the similar level as well. Compounds 1 and 4 significantly antagonized the shortening of the AP duration induced by carbachol and increased it. Compound 1 abolished the reduction of isometric contraction as well. Derivative 3 significantly lengthened (31 ms) the AP duration at a 90 % repolarization in papillary muscles, while 1 and 4 failed to affect this index. The selective blockade of the rapid component of the delayed rectifier potassium current (Ikr) by dl-sotalol (1 micromol/L) did not show the substantial influence on benzimidazole effects. CONCLUSION: These findings support the hypothesis that the tested benzo[d] imidazole derivatives abolish the influence of carbachol on AP and the isometric contraction by inhibition of acetylcholine-activated potassium current (KACh) in guinea pig atrial myocytes and therefore may be beneficial for the prognosis of patients with advanced heart failure and atrial fibrillation.