Monomeric Ones Research Articles

Phytochemical Screening, Nutritional Properties and Biological Activities of Sweet and Conventional Potato Planted in Morocco

This study aimed at studying phytochemical composition, nutritional properties and biological activities (antioxidant and anti-inflammatory) of two potato varieties (sweet potato (SP): Ipomoea batatas L. and conventional potato (CP): Solanum tuberosum L.) planted and consumed in Morocco. For this, potato samples (SP and CP) were firstly subjected to phytochemical and nutritional analysis, including water content, total and reducing sugars, proteins, lipids, vitamin C, carotenoids, phenolic compounds and flavonoids. Secondly, phenolic compounds extracts were subjected to biological activities namely antioxidant and invitro anti-inflammatory. Potato extracts antioxidant activity was tested by DPPH and total antioxidant capacity (TAC) methods. Proteins and lipids contents were found much higher in SP (5.21 ± 0.26 and 0.29 ± 0.02 g/100g DW) respectively than in CP (2.93 ± 0.15 and 0.11 ± 0.01 g/100g DW) respectively. Besides, total and reducing sugars contents were 16.65 and 2.53 g/100g DW in the CP, and 12.47 and 2.13 g/100g DW in the SP, respectively. The antioxidant activity of different SP extracts was found to be higher than those of CP, by using DPPH and TAC methods. These findings could be explained by SP richness in carotenoids (212 ± 10.60 mg/100g DW), phenolic compounds (130.11 ± 6.51 mg GAE/100g DW), flavonoids (85.03 ± 4.2 5mg QE/100g DW) and vitamin C (471.33 ± 23.57 mg/100g DW). Exclusion chromatography done by Sephadex G50 showed that polymeric phenolic compounds in SP were more abundant when compared to monomeric ones. This difference was consistent with the anti-inflammatory activity assessed in vitro.

Expression of chiral molecular and supramolecular structure on enantioselective catalytic activity

Understanding the structure-function relationships encoded on chiral catalysts is important for investigating the fundamental principles of catalytic enantioselectivity. Herein, the synthesis and self-assembly of naphthalene substituted bis-l/d-histidine amphiphiles (bis-l/d-NapHis) in DMF/water solution mixture is reported. The resulting supramolecular assemblies featuring well-defined P/M nanoribbons (NRs). With combination of the (P/M)-NR and metal ion catalytic centers (Mn+ = Co2+, Cu2+, Fe3+), the (P)-NR-Mn+ as chiral supramolecular catalysts show catalytic preference to 3,4-dihydroxy-S-phenylalanine (S-DOPA) oxidation while the (M)-NR-Mn+ show enantioselective bias to R-DOPA oxidation. In contrast, their monomeric counterparts bis-l/d-NapHis-Mn+ display an inverse and dramatically lower catalytic selectivity in the R/S-DOPA oxidation. Among them, the Co2+-coordinated supramolecular nanostructures show the highest catalytic efficiency and enantioselectivity (select factor up to 2.70), while the Fe3+-coordinated monomeric ones show nearly racemic products. Analysis of the kinetic results suggests that the synergistic effect between metal ions and the chiral supramolecular NRs can significantly regulate the enantioselective catalytic activity, while the metal ion-mediated monomeric bis-l/d-NapHis were less active. The studies on association constants and activation energies reveal the difference in catalytic efficiency and enantioselectivity resulting from the different energy barriers and binding affinities existed between the chiral molecular/supramolecular structures and R/S-DOPA enantiomers. This work clarifies the correlation between chiral molecular/supramolecular structures and enantioselective catalytic activity, shedding new light on the rational design of chiral catalysts with outstanding enantioselectivity.

Circular RNA oligonucleotides: enzymatic synthesis and scaffolding for nanoconstruction.

We report the efficient synthesis of monomeric circular RNAs (circRNAs) in the size range of 16-44 nt with a novel DNA dumbbell splinting plus T4 DNA ligation strategy. Such a DNA dumbbell splinting strategy was developed by one group among ours recently for near-quantitative conversion of short linear DNAs into monomeric circular ones. Furthermore, using the 44 nt circRNA as scaffold strands, we constructed hybrid RNA:DNA and pure RNA:RNA double crossover tiles and their assemblies of nucleic acid nanotubes and flat arrays.

Polymerization State of Vanadyl Species Affects the Catalytic Activity and Arsenic Resistance of the V2O5-WO3/TiO2 Catalyst in Multipollutant Control of NOx and Chlorinated Aromatics.

The conventional V2O5-WO3/TiO2 catalyst suffers severely from arsenic poisoning, leading to a significant loss of catalytic activity. The doping of Al or Mo plays an important role in promoting the arsenic resistance on NH3 selective catalytic reduction (NH3-SCR), but their promotion mechanism remains in debate and has yet to be explored in multipollutant control (MPC) of NOx and chlorinated organics. Herein, our experimental characterizations and density functional theory (DFT) calculations confirmed that arsenic species preferentially adsorb on both Al and Mo to form arsenate, thereby avoiding bonding to the catalytically active V sites. More importantly, Al doping partially converted the polymeric vanadyl species into monomeric ones, thereby inhibiting the near-surface and bulk lattice oxygen mobility of the V2O5-WO3/TiO2 catalyst, while Mo doping resulted in vanadyl polymerization with an enriched V5+ chemical state and exhibited superior MPC activity and COx selectivity. Our work shows that antipoisoning catalysts can be designed with the combination of site protection and occurrence state modification of the active species.

Properties and Activity of Peptide Derivatives of ACE2 Cellular Receptor and Their Interaction with SARS-CoV-2 S Protein Receptor-Binding Domain

The aim of this work was to design and characterize peptides based on the α-helices h1 and h2 of the ACE2 receptor, forming the interaction interface between the receptor-binding domain (RBD) of the SARS-CoV-2 S protein and the cellular ACE2 receptor. Monomeric and heterodimeric peptides connected by disulfide bonds at different positions were synthesized. Solubility, RBD-binding affinity, and peptide helicity were experimentally measured, and molecular dynamics simulation was performed in various solvents. It was established that the preservation of the helical conformation is a necessary condition for the binding of peptides to RBD. The peptides have a low degree of helicity and low affinity for RBD in water. Dimeric peptides have a higher degree of helicity than monomeric ones, probably due to the mutual influence of helices. The degree of helicity of the peptides in trifluoroethanol is the highest; however, for in vitro studies, the most suitable solvent is a water-ethanol mixture.

Polymerized ionic liquids on charged electrodes: New prospects for electrochemistry

The number of electrochemical applications of ionic liquids and their polymerized forms is steadily growing. Nevertheless, polymeric ionic liquid-based electrochemical systems have hardly ever been described theoretically in the same way as monomeric ionic liquids-based ones. In this opinion, we briefly outline recent studies addressing basic and applied research of polymeric ionic liquids and shortly discuss our recently developed theoretical model, which describes the behavior of a polymeric ionic liquid and its solution on a charged electrode. We summarize the results of the obtained capacitance, electrostatic potential, and ionic concentration profiles and outline further development of the theoretical description of polymeric ionic liquids.

Elucidating the sensitivity of vanadyl species to water over V2O5/TiO2 catalysts for NOx abatement via operando Raman spectroscopy

Vanadia-based catalysts are widely used in the selective catalytic reduction of NOx with NH3 (NH3-SCR) for NOx abatement. However, the effect of water on specific vanadyl species is still unclear. Herein, the temperature-dependent sensitivity of vanadyl species to water has been originally elucidated via operando Raman spectroscopy. Interestingly, the stronger competitive adsorption of NH3 on polymeric vanadyl species in the presence of H2O dominants the NH3-SCR reaction above 250 °C despite the polymeric vanadyl show stronger adsorption to H2O than the monomeric ones. By contrast, the association of water molecules via hydrogen bonding dominants the activity degeneration to both monomeric and polymeric vanadyl species at temperatures below 250 °C. Furthermore, the stronger adsorption of water on polymeric vanadyl will give rise to even worse degeneration. This work elucidates the interaction of vanadyl species with water, which is essential for the development of high-performance catalysts for water-tolerant NOx abatement.

From a dimer to a monomer: Construction of a chimeric monomeric isocitrate dehydrogenase.

Many isocitrate dehydrogenases (IDHs) are dimeric enzymes whose catalytic sites are located at the intersubunit interface, whereas monomeric IDHs form catalytic sites with single polypeptide chains. It was proposed that monomeric IDHs were evolved from dimeric ones by partial gene duplication and fusion, but the evolutionary process had not been reproduced in laboratory. To construct a chimeric monomeric IDH from homo-dimeric one, it is necessary to reconstitute an active center by a duplicated region; to properly link the duplicated region to the rest part; and to optimize the newly formed protein surface. In this study, a chimeric monomeric IDH was successfully constructed by using homo-dimeric Escherichia coli IDH as a start point by rational design and site-saturation mutagenesis. The ~67 kDa chimeric enzyme behaved as a monomer in solution, with a Km of 61 μM and a kcat of 15 s-1 for isocitrate in the presence of NADP+ and Mn2+ . Our result demonstrated that dimeric IDHs have a potential to evolve monomeric ones. The evolution of the IDH family was also discussed.

Comparison of ab initio HF and DFT calculations of the structure and spectroscopy of two dimeric systems of chloro Yb(III) mono-phthalocyanine in polymeric lattice

Abstract Lanthanide complexes with phthalocyanines (Pc) and porphyrins are of great interest because of their unique luminescence behavior and many applications. Our research is devoted to photophysical studies and theoretical calculations HF and DFT of the structure and spectroscopy of two dimeric systems, created by chloro Yb(III) monophthalocyanines and comparison of the calculated spectroscopic behaviour with the experimental one for monomeric chelate in polymeric lattice of PMMA. Ytterbium chelates were chosen because they have special properties appropriate for technology of different materials with unique spectroscopic behaviour in NIR region, which is not overlapped by very intensive emission of π-conjugated system of phthalocyanine or by upconversion transitions. The drastic variation in emission properties of materials depend on the energy of excitation, and only minor changes are observed in spectroscopic frequencies of dimeric systems compared to monomeric ones. Attention is paid to the radiative, non-radiative and non-linear processes, intramolecular energy transfer and the role of charge-transfer state in this process.

Oligomerization triggered by foldon to enhance the catalytic efficiency of feruloyl esterase

A new method to express oligomerized feruloyl esterase (FAE) in Pichia pastoris GS115 to improve the catalytic efficiency was developed. It was realized by fusing the foldon domain at the C-terminus of FAE, and the fusion protein was purified by histidine tag. Fusion of the feruloyl esterase with the foldon domain resulted spontaneously forming a trimer FAE to improve the catalytic performance. The oligomerized FAE and monomeric FAE were obtained by purification. The apparent molecular weight of the oligomerized FAE was about 110 kDa, while the monomeric FAE about 40 kDa, and the optimum temperature of the oligomerized FAE was 50 °C, which is the same as the monomeric one. The optimal pH of the oligomerized FAE is 5.0, while the optimal pH of the monomer FAE is 6.0. When compared with the monomeric ones, the catalytic efficiency (kcat/Km) of the oligomerized FAE increased 7.57-folds. The catalytic constant (kcat) of the oligomerized FAE increased 3.42-folds. The oligomerized FAE induced by foldon have advantages in the catalytic performances, which represents a simple and effective enzyme-engineering tool. The method proposed here for improving the catalytic efficiency of FAE would have great potentials for improving the catalytic efficiency of other enzymes.

Association of hydrophilic derivatives of chlorophyll a in ethanol–water and ethanol–water–solubilizer systems

Electronic absorption spectroscopy and fluorescence spectroscopy were used to study conditions for the formation of associates of amphiphilic phorbins and chlorins in an ethanol–water system. The conditions and degree of disaggregation in the presence of solubilizing additives of nonionic surfactants (Tween 80) and biocompatible polymers (polyethylene glycol and polyvinylpyrrolidone) were also investigated. The propensity of the macroheterocycles based on chlorophyll a to association in water-alcoholic solutions decreases on going from covalently bound dimeric structures to monomeric ones, on going from phorbins to chlorins and on accumulating hydrophilic glycol or positively charged alkylammonium fragments in the molecule. Among the considered solubilizers, the nonionic surfactant Tween 80 emerged as the most efficient means for destroying chlorin associates in water–alcohol solutions with a high content of water.

DPPH Radical Scavenging Activity and Polyphenols in the Pods of 3 Common Beans

The pods of common beans (Phaseolus vulgaris) are rich in various nutrients, and they could therefore be important parts of the human diet. In the present study, we have analyzed the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity and the contents of polyphenols, anthocyanin, vitamin C, and carotenoid in the pods of 3 varieties of common beans. French beans had the highest DPPH radical scavenging activity and polyphenol contents among the three varieties. The anthocyanin content was 3.93 mg/g D.W. in French beans, but not detected in bush beans and Romano beans. The vitamin C and carotenoid contents ranged from 0.45-1.96 and 0.31-0.60 mg/g D.W. in the pods of these common beans, respectively. Moreover, we found French beans contained monomeric (Fra.I), oligomeric (Fra.II), and polymeric (Fra.III) polyphenols (67%, 31%, and 2%, respectively). In contrast, monomeric polyphenols are the main polyphenols (Fra.I > 96%) in bush beans and Romano beans. Oligomeric polyphenols (Fra.II) show higher DPPH radical scavenging activity than monomeric ones (Fra.I) in French beans. Oligomeric polyphenols with both B-type and A-type bonds were present in Fra.II from French beans. We identified malvidin 3,5-diglucoside as the anthocyanin in French beans by HPLC-PDA/MS. In summary, as a vegetable, French beans have the highest antioxidant activity among the three varieties of common bean pods studied here.

Oligomerization triggered by foldon: a simple method to enhance the catalytic efficiency of lichenase and xylanase

BackgroundEffective and simple methods that lead to higher enzymatic efficiencies are highly sough. Here we proposed a foldon-triggered trimerization of the target enzymes with significantly improved catalytic performances by fusing a foldon domain at the C-terminus of the enzymes via elastin-like polypeptides (ELPs). The foldon domain comprises 27 residues and can forms trimers with high stability.ResultsLichenase and xylanase can hydrolyze lichenan and xylan to produce value added products and biofuels, and they have great potentials as biotechnological tools in various industrial applications. We took them as the examples and compared the kinetic parameters of the engineered trimeric enzymes to those of the monomeric and wild type ones. When compared with the monomeric ones, the catalytic efficiency (kcat/Km) of the trimeric lichenase and xylanase increased 4.2- and 3.9- fold. The catalytic constant (kcat) of the trimeric lichenase and xylanase increased 1.8- fold and 5.0- fold than their corresponding wild-type counterparts. Also, the specific activities of trimeric lichenase and xylanase increased by 149% and 94% than those of the monomeric ones. Besides, the recovery of the lichenase and xylanase activities increased by 12.4% and 6.1% during the purification process using ELPs as the non-chromatographic tag. The possible reason is the foldon domain can reduce the transition temperature of the ELPs.ConclusionThe trimeric lichenase and xylanase induced by foldon have advantages in the catalytic performances. Besides, they were easier to purify with increased purification fold and decreased the loss of activities compared to their corresponding monomeric ones. Trimerizing of the target enzymes triggered by the foldon domain could improve their activities and facilitate the purification, which represents a simple and effective enzyme-engineering tool. It should have exciting potentials both in industrial and laboratory scales.

Structural and Stereochemical Studies of Laurokamurols A-C, Uncommon Bis-sesquiterpenoids from the Chinese Red Alga Laurencia okamurai Yamada.

Three novel heterodimeric laurane-type sesquiterpenoids, laurokamurols A-C (1-3), along with eight known related monomeric ones (4-11) were isolated from the East China Sea red alga Laurencia okamurai Yamada. The absolute configurations of the new bis-sesquitepenoids, especially their axial chirality, were determined by extensive spectroscopic analyses and TDDFT-ECD method. All of the new compounds showed promising PTP1B inhibitory activities with IC50 values comparable to the positive control, indicating them as potential food additives or pharmaceutical drug leads toward obesity or diabetes.

Propane oxidative dehydrogenation over VOx/SBA-15 catalysts

VOx/SBA-15 catalysts with five different vanadium loadings were prepared by a modified wet impregnation method, characterized using N2 adsorption, XRD, EDX, SEM, Raman and UV–vis spectroscopies and H2-TPR techniques, and tested in the oxidative dehydrogenation of propane in the temperature range 450–600°C. For all the catalysts the propane conversion increases with both reaction temperature and vanadium loading, while the selectivity for propene decreases mainly to the benefit of carbon oxides. Several types of VOx species coexist on the catalyst surface, with monomeric and low-polymerized ones leading mainly to propene, while V2O5 crystallites at high vanadium loadings producing more carbon oxides. Propene was determined to be the only primary product irrespective of the vanadium content.

A novel cationic Gemini surfactant with amide group: synthesis and micellization behavior in aqueous solutions

Novel cationic Gemini surfactant with amide group, N 1,N 10-bis(3-dodecanamidopropyl)-N 1,N 1,N 10,N 10-tetramethyldecan-1,10-diammonium bromide (abbreviated as 2C12enAm) has been synthesized by two-step reactions, purified and characterized in our laboratory. The critical micelle concentration (CMC) values of this Gemini surfactant were determined using electrical conductivity and surface tension measurements in the range of temperatures from 298.15 to 328.15 K. It was observed that the CMC value of Gemini surfactant has a much lower value compared with monomeric ones and shows a slight increase with an increase in the temperature. The interactions between Gemini and conventional monomeric surfactant hexadecyltrimethylammonium bromide (CTAB) have been studied using the conductivity at a certain micellar concentration and temperature range. Rubingh’s theory is used to evaluate the micellar interaction parameters (β) for the mixed systems. It has been observed that mixed micelle formation in all the binary mixtures exhibited negative synergism (antagonism) or ideal behavior due to positive β values. Thermodynamics parameters were also obtained from the temperature dependence of the CMC values. From the surface tension measurements, CMC, maximum surface excess concentration at the solution/air interface (Γmax), minimum area per surfactant molecule (A min), the surface pressure at CMC (ΠCMC), the surfactant concentration required to reduce the surface tension of solvent by 20 mN m−1 (pC20), and thermodynamic parameters have been evaluated at same temperatures.

Mechanochromism in the luminescence of novel cyclometalated platinum(II) complexes with α-aminocarboxylates.

Six novel phosphorescent cyclometalated platinum(ii) complexes with α-aminocarboxylato ligands, [Pt(II)(ppy)L] (ppy = 2-phenylpyridinato, L(-) = Gly, Ala, Leu, Ile, Phe, Sar), were synthesized, and the structures were determined by X-ray crystallography. [Pt(II)(ppy)L] (L(-) = Gly, Ala) in crystals are in monomeric structures and stack through π-π interactions to form columns, and the features of the luminescence are similar to each other and those in solution, suggesting little influence of the π-π interactions on the luminescence. [Pt(II)(ppy)Leu] has a dimeric structure through the Pt-Pt interaction. [Pt(II)(ppy)Sar] showed two pseudo-polymorphs, one of which contains both monomeric and dimeric forms, while the other consists of only dimeric units. Intra-dimer π-π interactions were observed in both the dimeric units. [Pt(II)(ppy)L] (L(-) = Leu, Ile, Phe) in the solid state displayed different spectral patterns of luminescence from those in solution, suggesting that the dimeric structures through the Pt-Pt interaction in the solid state are dissociated into the corresponding monomeric ones in solution. The complexes except [Pt(II)(ppy)Phe] in the solid state exhibited reversible luminescent mechanochromism in response to the mechanical grinding and treatment with a few drops of solvent. These phenomena are induced by the change in the energy level of the triplet state due to the change in the extent of intermolecular interactions, which appeared due to the crystalline-amorphous phase conversion.

Active component of supported vanadium catalysts in the selective oxidation of methanol

The structure of catalysts based on vanadium oxide supported on different oxides (SiO2, γ-Al2O3, ZrO2, and TiO2) was investigated. Their catalytic properties in the selective oxidation of methanol in a temperature range of 100–250°C were studied. It was shown that the nature of the support determines the structure of the oxide forms of vanadium. The supporting of vanadium on SiO2 and γ-Al2O3 leads to the preferred formation of crystalline V2O5; the surface monomeric and polymeric forms of VOx are additionally formed on ZrO2 and TiO2. It was established that the crystalline V2O5 oxide is least active in the selective oxidation of methanol; the polymeric forms are more active than monomeric ones. The mechanism of the selective oxidation of methanol to dimethoxymethane and methyl formate on the vanadium oxide catalysts is considered.

Increasing the potency of neutralizing single-domain antibodies by functionalization with a CD11b/CD18 binding domain

Recombinant single domain antibodies (nanobodies) constitute an attractive alternative for the production of neutralizing therapeutic agents. Their small size warrants rapid bioavailability and fast penetration to sites of toxin uptake, but also rapid renal clearance, which negatively affects their performance. In this work, we present a new strategy to drastically improve the neutralizing potency of single domain antibodies based on their fusion to a second nanobody specific for the complement receptor CD11b/CD18 (Mac-1). These bispecific antibodies retain a small size (˜30 kDa), but acquire effector functions that promote the elimination of the toxin-immunocomplexes. The principle was demonstrated in a mouse model of lethal toxicity with tetanus toxin. Three anti-tetanus toxin nanobodies were selected and characterized in terms of overlapping epitopes and inhibition of toxin binding to neuron gangliosides. Bispecific constructs of the most promising monodomain antibodies were built using anti Mac-1, CD45 and MHC II nanobodies. When co-administered with the toxin, all bispecific antibodies showed higher toxin-neutralizing capacity than the monomeric ones, but only their fusion to the anti-endocytic receptor Mac-1 nanobody allowed the mice to survive a 10-fold lethal dose. In a model of delayed neutralization of the toxin, the anti- Mac-1 bispecific antibodies outperformed a sheep anti-toxin polyclonal IgG that had shown similar neutralization potency in the co-administration experiments. This strategy should have widespread application in the development of nanobody-based neutralizing therapeutics, which can be produced economically and more safely than conventional antisera.

Characterization of HIV-1 entry inhibitors with broad activity against R5 and X4 viral strains

BackgroundCombined antiretroviral therapy has drastically reduced mortality and morbidity of HIV-infected individuals. Nevertheless long-term toxicity and appearance of viral resistance hampers the prolonged effectiveness of combination therapy, requiring a continuous input of drugs to replace those utilized in combination regimens. We here investigated the anti-HIV activity of novel derivatives of the suradista chemical class.MethodsCompounds were tested on acute HIV-1 infection of activated peripheral blood mononuclear cells. HIV production was monitored by enzyme-linked immunosorbent assay measuring the protein p24 released in culture supernatants. Fusion assays were carried out to study the mechanism of action of these compounds. A modified version of a previously established recombinant vaccinia virus-based assay was used measuring activation of a reporter gene upon fusion of two distinct cell populations. Flow cytometry was performed in competition assays for the binding of several antibodies targeting different sites of the viral envelope glycoprotein gp120, or the receptor CD4, or the coreceptors CXCR4 and CCR5.ResultsFour compounds inhibited replication of a prototypic R5 (BaL) and X4 (IIIB) laboratory-adapted HIV-1 strain at low micromolar concentrations, in the absence of cytotoxicity. Approximately a ten fold greater activity was achieved against the X4 as compared to the R5 strain.The compounds blocked X4 and R5 HIV-1 fusion, a step of viral entry. This activity appeared specific for HIV-1, as entry of human herpesvirus 6 (HHV-6) and influenza virus was not substantially affected. Further investigation of the inhibitory mechanism revealed that these new molecules target the viral envelope, rather than the coreceptors, as previously shown for a congener of the same class characterized by a long plasmatic half-life. Indeed ND-4043, the most active compound, specifically competed with binding of monoclonal antibodies against the CD4-binding site (CD4-BS) and coreceptor-binding site (CoR-BS) of gp120. These compounds displayed broad anti-HIV activity, as they inhibited various primary R5, X4 and, importantly, dualtropic R5X4 HIV-1 isolates. Of the four derivatives tested, the dimeric compounds were consistently more potent than the monomeric ones.ConclusionsGiven their unique features, these molecules represent promising candidates for further development and exploitation as anti-HIV therapeutics.Electronic supplementary materialThe online version of this article (doi:10.1186/s12967-015-0461-9) contains supplementary material, which is available to authorized users.