Role Of Hydroxylation Research Articles

Role of hydroxyl on metal surface in hydrogenation reactions

The important role of surface hydroxyl in metal catalysis is attracting more attentions but rarely studied for liquid-phase hydrogenation reactions. Here we report such deliberate research with two model substrates, p-chloronitrobenzene and cinnamaldehyde. Graphene-supported iridium nanoparticles with hydroxyl on the metal surface were prepared by hydrothermal synthesis, and the surface hydroxyl can be removed by a mild pre-reduction. The catalyst with surface hydroxyl exhibited around three times higher rate for the hydrogenation of p-chloronitrobenzene than the catalyst without hydroxyl, and an opposite trend was found for the hydrogenation of cinnamaldehyde. Kinetic study revealed that although the surface hydroxyl halved the coverage of H on iridium, it increased the rate constant by a factor of eight through reducing the reaction barrier for the hydrogenation of p-chloronitrobenzene. Theoretical calculation confirmed that the surface hydroxyl can polarize the nitro group via a weak hydrogen-bond interaction and thus facilitate its hydrogenation.

Effects of dietary collagen cofactors and hydroxyproline on the growth performance, textural properties and collagen deposition in swim bladder of Nibea coibor based on orthogonal array analysis

The global demand for collagen is continuously growing over years. Nutritional regulation of quality and collagen deposition in the swim bladder, an ideal collagen source of marine product, is a promising method for improving the economic value of fish. In this study, to enhance growth efficiency and collagen deposition in swim bladder of an important economic marine fish, the chu’s croaker (Nibea coibor), a L9(34) orthogonal array was designed with three levels for each factor, which are hydroxyproline (Hyp) and the key cofactors for proline hydroxylation during collagen post-translation modification, such as A1-A3 (Hyp): 0, 10 and 20 g/kg; B1-B3 (vitamin C, VC): 0, 0.20 and 0.40 g/kg; C1-C3 (Fe2+): 0, 0.20 and 0.40 g/kg; D1-D3 (α-ketoglutarate, AKG): 0, 10 and 20 g/kg, to formulate the trial feeds. An 8-week feed trial was carried out on 405 fish (initial weight 269.04 ± 3.18 g) which were randomly distributed into the nine treatment groups with three replicates of 15 fish per cage. Results indicated that appropriate increase of dietary Hyp and VC level is more beneficial to collagen deposition and textural properties in swim bladder, while Hyp and AKG exerted more significant effects on the growth performance. Gene expression analysis of collagen metabolism indicated that Hyp mainly improved the synthesis of type I collagen and inhibited collagen degradation, while VC and AKG mainly play an important role in hydroxylation of proline residues on collagen. The best combination for growth performance and collagen deposition in swim bladder were suggested to be A2B2C1D3 and A2B2C1D1, respectively. The results demonstrated that appropriate dietary supplementation of Hyp and cofactors can improve growth and collagen production of swim bladder. Our result would provide reference data for nutritional regulation of the species and optimization of the commercial feed to provide fish products with high quality.

Enhanced Formaldehyde Oxidation Performance of the Mesoporous TiO2(B)-Supported Pt Catalyst: The Role of Hydroxyls.

As one of the crystal phases of titania, TiO2(B) was first utilized as a catalyst carrier for the oxidation of formaldehyde (HCHO). The mesoporous TiO2(B) loaded with Pt nanoparticles enhanced the HCHO oxidation reaction whose reaction rate was 4.5–8.4 times those of other crystalline TiO2-supported Pt catalysts. Simultaneously, Pt/TiO2(B) exhibited long-term stable HCHO oxidation performance. The structural characterization results showed that in comparison with Pt/anatase, Pt/TiO2(B) had more abundant hydroxyls, facilitating increasing the content of oxygen species. Studies on the role of hydroxyls in HCHO oxidation of Pt/TiO2(B) illustrated that synergistic involvement of terminally bound hydroxyls and bridging hydroxyls in HCHO oxidation accelerated the transformation from HCHO to formate via dioxymethylene. Moreover, hydroxyls could avoid the accumulation of excessive formate on Pt/TiO2(B) and promote the rapid oxidation of CO. Accordingly, the hydroxyl groups could accelerate each substep of formaldehyde oxidation, which enabled Pt/TiO2(B) to exhibit excellent formaldehyde oxidation performance.

Изменение физико-химических и культуральных свойств бактерий Azospirillum baldaniorum Sp245 под влиянием некоторых синтетических кумаринов

Due to the small number of studies on the role of coumarins in associative symbiotic relationships, some aspects of the influence of synthetic coumarins on the physicochemical and cultural properties of Azospirillum baldaniorum Sp245 were studied for the first time. To reveal the role of hydroxylation in position 7 of the fused aromatic ring – 1-(2-oxo-2H-chromen-3-yl)butan-1,3-dione, comparative studies of the effect of the original and hydroxylated coumarins on the culture of a model strain of azospirilla were carried out. The survival of bacteria after the addition of coumarins was studied by counting CFU on an agar medium. The biofilm formation activity of the culture was assessed using crystal violet. The change in the surface of bacteria under the action of coumarins was studied by the electrical polarizability of bacterial cells on an ELUS electrooptical analyzer (EloSystemGbR, Germany). The yield and monosaccharide composition of extracellular glycopolymers were studied using gas-liquid chromatography.For the first time, an increase in the yield of EPS of bacteria during growth in the presence of 1-(7-hydroxy-2-oxo-2Hchromen-3-yl)butan-1,3-dione by 1.2 and 1.7 times for concentrations of 50 and 100 μM respectively was observed. It has been established for the first time that the hydroxylated substance has a higher antibacterial activity compared to the unsubstituted one. A decrease in the number of viable cells in planktonic culture and inhibition of biofilm growth were revealed. It has been shown by electro-optical analysis that the presence of coumarins in the cultivation medium in all concentrations studied leads to a change in the electrical polarizability of A. baldaniorum Sp245 cells. The use of electrooptical analysis of cell suspensions using monospecific antibodies obtained against lipopolysaccharides of this strain made it possible to reveal the absence of changes in carbohydrate antigenic determinants on the surface of bacterial cells. This is consistent with the data of the analysis of the composition of extracellular polysaccharides by GLC, during which no differences were found in the qualitative composition and ratio of monosaccharides. An increase in the yield of bacterial EPS during growth in the presence of 1-(7-hydroxy-2-oxo-2H-chromen-3-yl) butan-1,3-dione by 1.2 and 1.7 times for concentrations of 50 and 100 μM was shown. The results obtained allow us to consider the changes that have occurred as features of the adaptation of bacteria to the associative conditions of existence.

The role of hydroxylation on·OH generation for enhanced ozonation of benzoic acids: Reactivity, ozonation efficiency and radical formation mechanism

• Hydroxyl groups activated benzoic acid for enhanced reactivity with ozone. • Possible pathways for the generation of O 2 ·- and·OH in ozonation of benzoic acids were proposed. • Plausible mechanism for the activated ozonation of benzoic acid was elucidated. • Synergistic effect in co-ozonation and reduced superiority in catalytic ozonation were observed with extra·OH production.

Augmentation of progestin signaling rescues testis organization and spermatogenesis in zebrafish with the depletion of androgen signaling.

Disruption of androgen signaling is known to cause testicular malformation and defective spermatogenesis in zebrafish. However, knockout of cyp17a1, a key enzyme responsible for the androgen synthesis, in ar-/- male zebrafish paradoxically causes testicular hypertrophy and enhanced spermatogenesis. Because Cyp17a1 plays key roles in hydroxylation of pregnenolone and progesterone (P4), and converts 17α-hydroxypregnenolone to dehydroepiandrosterone and 17α-hydroxyprogesterone to androstenedione, we hypothesize that the unexpected phenotype in cyp17a1-/-;androgen receptor (ar)-/- zebrafish may be mediated through an augmentation of progestin/nuclear progestin receptor (nPgr) signaling. In support of this hypothesis, we show that knockout of cyp17a1 leads to accumulation of 17α,20β-dihydroxy-4-pregnen-3-one (DHP) and P4. Further, administration of progestin, a synthetic DHP mimetic, is sufficient to rescue testicular development and spermatogenesis in ar-/- zebrafish, whereas knockout of npgr abolishes the rescue effect of cyp17a1-/- in the cyp17a1-/-;ar-/- double mutant. Analyses of the transcriptomes among the mutants with defective testicular organization and spermatogenesis (ar-/-, ar-/-;npgr-/- and cyp17a-/-;ar-/-;npgr-/-), those with normal phenotype (control and cyp17a1-/-), and rescued phenotype (cyp17a1-/-;ar-/-) reveal a common link between a downregulated expression of insl3 and its related downstream genes in cyp17a-/-;ar-/-;npgr-/- zebrafish. Taken together, our data suggest that genetic or pharmacological augmentation of the progestin/nPgr pathway is sufficient to restore testis organization and spermatogenesis in zebrafish with the depletion of androgen signaling.

Dynamics of Antimicrobial Peptide Encapsulation in Carbon Nanotubes: The Role of Hydroxylation.

IntroductionCarbon nanotubes (CNTs) have been widely employed as biomolecule carriers, but there is a need for further functionalization to broaden their therapeutic application in aqueous environments. A few reports have unraveled biomolecule–CNT interactions as a measure of response of the nanocarrier to drug-encapsulation dynamics.MethodsHerein, the dynamics of encapsulation of the antimicrobial peptide HA-FD-13 (accession code 2L24) into CNTs and hydroxylated CNTs (HCNTs) is discussed.ResultsThe van der Waals (vdW) interaction energy of CNT–peptide and HCNT–peptide complexes decreased, reaching −110.6 and −176.8 kcal.Mol−1, respectively, once encapsulation of the peptide inside the CNTs had been completed within 15 ns. The free energy of the two systems decreased to −43.91 and −69.2 kcal.Mol−1 in the same order.DiscussionThe peptide was encased in the HCNTs comparatively more rapidly, due to the presence of both electrostatic and vdW interactions between the peptide and HCNTs. However, the peptide remained encapsulated throughout the vdW interaction in both systems. The negative values of the free energy of the two systems showed that the encapsulation process had occurred spontaneously. Of note, the lower free energy in the HCNT system suggested more stable peptide encapsulation.

Isomeric sp2-C-conjugated porous organic polymer-mediated photo- and sono-catalytic detoxification of sulfur mustard simulant under ambient conditions

Isomeric sp2-C-conjugated porous organic polymer-mediated photo- and sono-catalytic detoxification of sulfur mustard simulant under ambient conditions

Characterization and Utilization of Sulphuric Acid and Bitter Leaf Extract Activated Carbon from Rice Husk for Zn(II) Adsorption

The world is clamoring for green synthetic modes of scientific and technological operations. From this point of view, an attempt was made to prepare activated carbon from rice husk using aqueous bitter leaf extract and a mineral acid (H2SO4) separately. The surface characteristics and the adsorption properties of the activated carbons from both methods were compared. The effects of adsorption variables on the adsorption of Zn(II) by bitter leaf extract activated carbon (RHAC1) and H2SO4 activated carbon (RHAC2) were conducted through batch studies. The morphological characterization revealed RHAC1 to be fibrous, more porous and contained finer particles than the chemical-activated counterpart. The role of hydroxyl and carbonyl groups in the adsorption of Zn(II) was pivotal. The optimum pH values for the adsorption of Zn(II) by both samples was 7. The adsorption kinetics and equilibrium isotherm obeyed Elovich and Freundlich models respectively while the evaluated Langmuir qmax were 71.47 and 67.12 mg g–1 for RHAC1 and RHAC2 respectively. The thermodynamic parameters revealed that the process was endothermic and spontaneous at all evaluated temperatures. Therefore, bitter leaf aqueous extract, as an activating agent for carbon production, could serve as a better or close substitute for the less environment-friendly H2SO4.

CYP1A1* 2 A gene polymorphism frequency in Syrian breast cancer patients

IntroductionCYP1A1 plays an important role in procarcinogen activation and xenobiotic metabolism. It has a role in hydroxylation of estrogen that is one of the key mediators for breast cancer development. The CYP1A1*2A (m1) is the polymorphism in the 3′-flanking region of the gene. The aim of this study was to determine the frequency of CYP1A1* 2A polymorphism in breast cancer patients and healthy Syrian individuals. Materials and methodsGenomic DNA samples were isolated from 120 Syrian participants (60 breast cancer women and 60 healthy individuals). The PCR-RFLP technique was adopted to determine CYP1A1* 2A gene polymorphism. ResultsThe frequency of homozygote genotypes was 78.33% (TT) vs 1.67% (CC) in breast cancer patients, and 85% (TT) vs 1.67% (CC) in controls, respectively. The allelic frequency was 88.33% vs 92% for T and 11.67% vs 8% for C in breast cancer patients and controls, respectively. The frequency of the heterozygote genotype TC was 20% vs 13.33% in breast cancer patients and controls, respectively. No significant association was found between CYP1A1*2A gene polymorphism and the risk of breast cancer (p = 0202, OR = 0.626 (0.303–1.291)). ConclusionThese findings indicated that CYP1A1*2A polymorphism was not associated with increased risk of breast cancer in Syrian women. CYP1A1* 2A gene polymorphism in Syrian population (breast cancer patients and healthy individuals) were consistent with Iranian population. However, they were different from other populations such as in Iraq, Korea, China, Taiwan, Japan, Brazil, Mexico and Siberia.

Introducing an effective iron-based catalyst for heterogeneous electro-Fenton removal of Gemcitabine using three-dimensional graphene as cathode

Five natural iron minerals include hematite, magnetite, siderite, limonite and pyrite as natural sources of iron were investigated to determine the best one which has the highest catalytic ability in the heterogeneous electro-Fenton process. The process has emerged as a simple, green, cost-effective and efficient method for the removal of persistent and pathogenic anti-cancer drug pollutants like Gemcitabine. On the other hand, different effective factors like the initial concentration of Gemcitabine, the amount of pyrite as the chosen efficient iron mineral, applied current intensity, initial pH and time of treatment process were optimized using response surface methodology to represent the best experimental condition. The role of hydroxyl (•OH) and superoxide anion (•O2−) radicals was monitored using scavengers of active radicals. The degradation efficiency of Gemcitabine and total organic carbon analysis reached 98.33% and 78.2% respectively, in the optimum condition after 5 h of electrolysis. The gained high value of coefficient of 0.995 by analysis of variance indicated the reliability of the presented model. Gas chromatography–mass spectrometry analysis identified nine by-products like small molecules of acids, amides, amines and esters.

Role of Hydroxyl, Superoxide, and Nitrate Radicals on the Fate of Bromide Ions in Photocatalytic TiO2 Suspensions

The influence of bromide ions on systems containing highly reactive radical species is of great interest for environmental remediation, atmospheric chemistry, and the synthesis of high-added-value ...

The role of hydroxyl and carboxyl functional groups in adsorption of copper by carbon nanotube and hybrid graphene–carbon nanotube: insights from molecular dynamic simulation

In the present study, an all-atomic molecular dynamic simulation was used to investigate adsorption of copper ions (Cu (II)) by carbon nanotube and hybrid graphene–carbon nanotube in aqueous solution. In order to study oxygenated functional groups effect including hydroxyl (–OH) and carboxyl (–COOH), these nano-structures were functionalized with OH and COOH groups. To this end, oxygenated functional groups of these Nano-structures including OH and COOH were functionalized with hydroxyl (–OH) and carboxyl (–COOH) groups. The simulation results showed that more Cu (II) ions are adsorbed by hybrid graphene–carbon nanotube than by carbon nanotube alone. Conjugation of graphene and carbon nanotube creates a network of open-pores structures, which increases Cu (II) adsorption sites. According to the results, of the two functional groups, COOH was found to be more effective in adsorbing Cu (II) than OH. Of the nano-structures investigated, hybrid COOH-graphene–carbon nanotube showed the greatest Cu (II) adsorption in aqueous solution.

Role of Hydroxyl on Conductivity Switching of Poly(ethylene oxide)/TiO2 Electrical Bistable Devices

Conductivity switching in a semiconductor nanoparticle/polymer composite electrical bistable device is typically associated with the electron trapping between the semiconductor trap center and the polymer matrix. However, the switch‐on mechanism is still not clear, and even in the same metal oxide (MO) nanoparticle/polymer system, two different models are applied to explain the conductivity switching mechanisms, including Fowler–Nordheim (F–N) tunneling current and trapped charge‐limit‐current (TCLC). Therefore, the analysis of the conductivity‐switching mechanism in MO/polymer composite devices is crucial to facilitate technology development. Herein, poly(ethylene oxide) (PEO) films are deposited on top of the various TiO2 films, and the two different electrical bistabilities are observed. The corresponding conductivity‐switching mechanisms are found to be significantly related to the different TiO2 surface traps. The results demonstrate that the F–N tunneling current dominates in the devices where a large number of hydroxyl groups are present in TiO2, whereas, after removing the hydroxyl groups from the device, the switching‐on current is dominated by the TCLC mechanism.

Variability of surface components in gold catalysts – The role of hydroxyls and state of gold on activity and selectivity of Au-Nb2O5 and Au-ZnNb2O6 in methanol oxidation

The aim of this study was to use gold catalysts supported on niobium(V) oxide and mixed niobium-zinc oxide in methanol oxidation and to characterize step by step changes in the surface of catalysts that were caused by the activation of the catalyst and methanol oxidation. The purpose was to identify the species important for the activity and selectivity of the reaction. The following surface species were identified by XPS in as prepared catalysts: (i) highly nucleophilic oxygen with the excessive negative charge; (ii) lattice oxygen O2− in the metal oxide; (iii) oxygen in surface hydroxyls; (iv) negatively charged gold NPs (Au0)δ−; and (v) metal cations (niobium, zinc and gold). Activation of catalysts resulted in dehydroxylation accompanied by the formation of highly nucleophilic oxygen and metallic gold showing low activity in selective methanol oxidation. The interaction of the reaction products changed surface species towards basic hydroxyls and next to (Au0)δ− inducing the activity jump and total oxidation of methanol.

Antibacterial cotton fabric with in situ generated silver nanoparticles by one-step hydrothermal method

ABSTRACTThe cotton fabrics were immersed in 1–5 mM aqueous silver nitrate solutions maintained at 80°C for 24 h to in situ generate silver nanoparticles. The presence of silver nanoparticles in the nanocomposite films was proved by microscopic observation. Fourier transform infrared spectra indicated the role of hydroxyl and carboxyl groups of cotton fabric in reducing the silver salt to nanosilver. The nanocomposite cotton fabrics showed good antibacterial activity against Gram-negative and Gram-positive bacteria. The antibacterial cotton fabrics can be considered for medical applications such as surgical aprons, wound cleaning, and dressing.

Comment on “Clustering of Oxygen Vacancies at CeO2(111) : Critical Role of Hydroxyls”

Received 25 March 2016DOI:https://doi.org/10.1103/PhysRevLett.117.279601© 2016 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasChemical Physics & Physical ChemistryDefectsSurface & interfacial phenomenaVacanciesTechniquesDensity functional theoryScanning tunneling microscopyInterdisciplinary PhysicsCondensed Matter, Materials & Applied Physics

Reactivity of Perovskites with Water: Role of Hydroxylation in Wetting and Implications for Oxygen Electrocatalysis

Oxides are instrumental to applications such as catalysis, sensing, and wetting, where the reactivity with water can greatly influence their functionalities. We find that the coverage of hydroxyls (*OH) measured at fixed relative humidity trends with the electron-donor (basic) character of wetted perovskite oxide surfaces. Using ambient pressure X-ray photoelectron spectroscopy, we report that the affinity toward hydroxylation, coincident with strong adsorption energies calculated for dissociated water and hydroxyl groups, leads to strong H bonding that is favorable for wetting while detrimental to catalysis of the oxygen reduction reaction (ORR). Our findings provide novel insights into the coupling between wetting and catalytic activity and suggest that catalyst hydrophobicity should be considered in aqueous oxygen electrocatalysis.

Role of the Surface Chemistry of Ceria Surfaces on Silicate Adsorption

Ceria nanoparticles (NPs) have been widely explored as a promising material in various fields. As synthesized under various physicochemical conditions, it exhibits the different surface chemistry. Here, the role of hydroxyl and nitrate group on ceria surface, formed under various physicochemical conditions, for the silicate adsorption was experimentally and theoretically investigated based on the adsorption isotherms and theoretical analyses using density functional theory (DFT) calculation. Experimental results acquired from adsorption isotherms with Freundlich model indicated that the nitrate group shows a much higher affinity with silicate than the hydroxyl groups. These phenomena were demonstrated through the theoretical approaches that exhibit the binding energy of the NO3-ceria (-4.383 eV) on the SiO2 surface being much higher than that of the OH-ceria (-3.813 eV). In good agreement with the experimental and the theoretical results based on adsorption properties, the results of chemical mechanical planarization (CMP) also show that the nitrate groups significantly enhance the removal of SiO2 than the hydroxyl groups. The results investigated in this study will provide researchers, studying the ceria NPs, with guidelines on the importance of exploring the surface chemistry of ceria.

Role of hydroxyl (OH) on structural and ferrimagnetism of annealed CoFe2O4 nanoparticles

Cobalt ferrites (CoFe2O4) with high magnetic moments and coercivity are proposed for the fabrication of media recording devices; however, their very high coercivity, which produces noise, is big hurdle in the practical form of these devices. Cobalt ferrites with high magnetic moment and moderate coercivity, and the role of hydroxyls on the structural and ferrimagnetic properties, have been investigated in detail. The proposed research investigates the following aspects that are important in understanding the role of hydroxyls: (1) the average particle size and presence of hydroxyls are correlated to the annealing temperatures, and (2) the hydroxyls have considerably influenced the structure and magnetic ordering in the nanocrystal. The prepared single spinel structure of cobalt ferrites exhibits good saturated hysteresis loops with ferrimagnetic behaviour and annealing at high temperature observed to play a significant role for the tuning of particle size, saturation magnetisation, coercivity and remnant magnetisation. The removal of hydroxyl at high temperatures in CoFe2O4 shows a stable crystallinity with high saturation magnetic moment and moderate coercivity. The novel aspect of the proposed system is the presence of hydroxyls at low annealing temperature, and later, the removal of these hydroxyls at high annealing temperature plays an important role for modifying the magnetic properties. The application of the research can be imagined as applications of media recording devices with low noise and high efficiency and also as antimicrobial/medical applications in biomaterials.