The hydroxyl species and acid sites on diatomite surface: a combined IR and Raman study

NASA Astrophysics Data System (ADS)

Yuan, P.; Wu, D. Q.; He, H. P.; Lin, Z. Y.

2004-04-01

Diffuse reflectance infrared Fourier transform spectroscopy (DRIFT), Raman spectroscopy of adsorbed pyridine molecules (Py-Raman) and in situ Py-IR have been used to investigate the hydroxyl species and acid sites on diatomite surfaces. The Lewis (L) and Brønsted (B) acid sites, and various hydroxyl species, including isolated hydroxyl groups, H-bonded hydroxyl groups and physically adsorbed water, are identified. The L acid sites in diatomite samples are resulted from the clay impurities, and the B acid sites are resulted from some moderate strength H-bonded hydroxyl groups. At room temperature, both of the isolated and H-bonded silanols associate with the physically adsorbed water by hydrogen bond. After calcination treatment, physically adsorbed water will be desorbed from the silanols, and the silanols will condense with the increase of temperature. Generally, the H-bonded silanols condense more easily than the isolated ones. The properties of surface hydroxyl species of diatomaceous silica are more similar to precipitated silica rather than fumed silica.

Preparation of porphyrins and their metal complexes

DOEpatents

Ellis, Jr., Paul E.; Langdale, Wayne A.

1997-01-01

A hydroxyl-containing pyrrolic compound having a hydroxyl group or a hydroxyl-containing group in the 2-position, optionally substituted in the beta positions, is condensed in an acidified two immiscible phase solvent system to produce excellent yields of the corresponding porphyrin or metal porphyrin.

Preparation of porphyrins and their metal complexes

DOEpatents

Ellis, P.E. Jr.; Langdale, W.A.

1997-08-19

A hydroxyl-containing pyrrolic compound having a hydroxyl group or a hydroxyl-containing group in the 2-position, optionally substituted in the beta positions, is condensed in an acidified two immiscible phase solvent system to produce excellent yields of the corresponding porphyrin or metal porphyrin.

The Unexpected and Exceptionally Facile Chemical Modification of the Phenolic Hydroxyl Group of Tyrosine by Polyhalogenated Quinones under Physiological Conditions.

PubMed

Qu, Na; Li, Feng; Shao, Bo; Shao, Jie; Zhai, Guijin; Wang, Fuyi; Zhu, Ben-Zhan

2016-10-17

The phenolic hydroxyl group of tyrosine residue plays a crucial role in the structure and function of many proteins. However, little study has been reported about its modification by chemical agents under physiological conditions. In this study, we found, unexpectedly, that the phenolic hydroxyl group of tyrosine can be rapidly and efficiently modified by tetrafluoro-1,4-benzoquinone and other polyhalogenated quinones, which are the major genotoxic and carcinogenic quinoid metabolites of polyhalogenated aromatic compounds. The modification was found to be mainly due to the formation of a variety of fluoroquinone-O-tyrosine conjugates and their hydroxylated derivatives via nucleophilic substitution pathway. Analogous modifications were observed for tyrosine-containing peptides. Further studies showed that the blockade of the reactive phenolic hydroxyl group of tyrosine in the substrate peptide, even by very low concentration of tetrafluoro-1,4-benzoquinone, can prevent the kinase catalyzed tyrosine phosphorylation. This is the first report showing the exceptionally facile chemical modification of the phenolic hydroxyl group of tyrosine by polyhalogenated quinones under normal physiological conditions, which may have potential biological and toxicological implications.

Unraveling the impact of hydroxylation on interactions of bile acid cationic lipids with model membranes by in-depth calorimetry studies.

PubMed

Singh, Manish; Bajaj, Avinash

2014-09-28

We used eight bile acid cationic lipids differing in the number of hydroxyl groups and performed in-depth differential scanning calorimetry studies on model membranes doped with different percentages of these cationic bile acids. These studies revealed that the number and positioning of free hydroxyl groups on bile acids modulate the phase transition and co-operativity of membranes. Lithocholic acid based cationic lipids having no free hydroxyl groups gel well with dipalmitoylphosphatidylcholine (DPPC) membranes. Chenodeoxycholic acid lipids having one free hydroxyl group at the 7'-carbon position disrupt the membranes and lower their co-operativity. Deoxycholic acid and cholic acid based cationic lipids have free hydroxyl groups at the 12'-carbon position, and at 7'- and 12'-carbon positions respectively. Doping of these lipids at high concentrations increases the co-operativity of membranes suggesting that these lipids might induce self-assembly in DPPC membranes. These different modes of interactions between cationic lipids and model membranes would help in future for exploring their use in DNA/drug delivery.

Formyl-ended heterobifunctional poly(ethylene oxide): synthesis of poly(ethylene oxide) with a formyl group at one end and a hydroxyl group at the other end.

PubMed

Nagasaki, Y; Kutsuna, T; Iijima, M; Kato, M; Kataoka, K; Kitano, S; Kadoma, Y

1995-01-01

Well-defined poly(ethylene oxide) (PEO) with a formyl group at one end and a hydroxyl group at the other terminus was synthesized by the anionic ring opening polymerization of ethylene oxide (EO) with a new organometallic initiator possessing an acetal moiety, potassium 3,3-diethoxypropyl alkoxide. Hydrolysis of the acetal moiety produced a formyl group-terminated heterobifunctional PEO with a hydroxyl group at the other end.

Xylosylation of Phenolic Hydroxyl Groups of the Monomeric Lignin Model Compounds 4-Methylguaiacol and Vanillyl Alcohol by Coriolus versicolor

PubMed Central

Kondo, Ryuichiro; Yamagami, Hikari; Sakai, Kokki

1993-01-01

When 4-methylguaiacol (MeG), a phenolic lignin model compound, was added to a culture that was inoculated with Coriolus versicolor, it was bioconverted into 2-methoxy-4-methylphenyl β-d-xyloside (MeG-Xyl). The phenolic hydroxyl group of vanillyl alcohol was much more extensively xylosylated than the alcoholic hydroxyl group. When a mixture of MeG and commercial UDP-xylose was incubated with cell extracts of mycelia, transformation of UDP-xylose into MeG-Xyl was observed. This result suggested that UDP-xylosyltransferase was involved in the xylosylation of phenolic hydroxyl groups of lignin model compounds. PMID:16348869

Compositions and methods for hydrocarbon functionalization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gunnoe, Thomas Brent; Fortman, George; Boaz, Nicholas C.

Embodiments of the present disclosure provide for methods of hydrocarbon functionalization, methods and systems for converting a hydrocarbon into a compound including at least one group ((e.g., hydroxyl group) (e.g., methane to methanol)), functionalized hydrocarbons, and the like.

Use of molecular dynamics to assess the biophysiological role of hydroxyl groups in glycerol dyalkyl glycerol teraethers

NASA Astrophysics Data System (ADS)

Huguet, Carme; Costenaro, Lionel; Fietz, Susanne; Daura, Xavier

2015-04-01

The cell membrane of some Archaea is constituted by lipids that span the whole membrane width and contain two alkyl chains bound by two glycerol groups (glycerol dyalkyl glycerol teraethers or GDGTs). These lipids confer stability to the membrane in mesophile to extremophile environments. Besides the more frequently studied isoprenoid archaeal lipids, both mono- and dihydroxy-GDGTs (OH-GDGT) have been recently reported to occur in marine sediments (1). OH-GDGTs contain up to two cyclopentane moieties and have been identified in both core and intact forms. In 2013, a correlation between OH-GDGTs and temperature was reported, with higher relative OH-GDGT abundances at high latitudes (2,3). The physiological function of the hydroxyl group in a GDGT is not yet known, but given the field results, it could be linked to an adaptation of the membrane to changes in temperature. For hydroxydiether lipid cores in methanogenic bacteria, it has been postulated that the hydroxyl group may alter the cell membrane properties: either extending the polar head group region or creating a hydrophilic pocket (4). It has also been suggested that the hydroxylation of the biphytany (l) moiety may result in enhanced membrane rigidity (1). To improve our understanding of the effect of the hydroxylation on physical properties of membranes, we performed molecular-dynamics simulations of GDGT membranes presenting and lacking these additional OH groups. This is an approach with a great development potential in the archaea lipid field, especially in relation to proxy validation. Our results indicate that the addition of an OH increases the membrane fluidity, thus providing an advantage in cold environments. We also observe a widening of the polar head group area, which could enhance transport. 1. Liu et al. 2012, GCA 2. Huguet et al. 2013, Org. Geochem 3. Fietz et al. 2013 4. Sprott et al. 1990. J. Biol. Chem. 265, 13735-13740.

Flow of quasi-two dimensional water in graphene channels

NASA Astrophysics Data System (ADS)

Fang, Chao; Wu, Xihui; Yang, Fengchang; Qiao, Rui

2018-02-01

When liquids confined in slit channels approach a monolayer, they become two-dimensional (2D) fluids. Using molecular dynamics simulations, we study the flow of quasi-2D water confined in slit channels featuring pristine graphene walls and graphene walls with hydroxyl groups. We focus on to what extent the flow of quasi-2D water can be described using classical hydrodynamics and what are the effective transport properties of the water and the channel. First, the in-plane shearing of quasi-2D water confined between pristine graphene can be described using the classical hydrodynamic equation, and the viscosity of the water is ˜50% higher than that of the bulk water in the channel studied here. Second, the flow of quasi-2D water around a single hydroxyl group is perturbed at a position of tens of cluster radius from its center, as expected for low Reynolds number flows. Even though water is not pinned at the edge of the hydroxyl group, the hydroxyl group screens the flow greatly, with a single, isolated hydroxyl group rendering drag similar to ˜90 nm2 pristine graphene walls. Finally, the flow of quasi-2D water through graphene channels featuring randomly distributed hydroxyl groups resembles the fluid flow through porous media. The effective friction factor of the channel increases linearly with the hydroxyl groups' area density up to 0.5 nm-2 but increases nonlinearly at higher densities. The effective friction factor of the channel can be fitted to a modified Carman equation at least up to a hydroxyl area density of 2.0 nm-2. These findings help understand the liquid transport in 2D material-based nanochannels for applications including desalination.

Novel protocol for highly efficient gas-phase chemical derivatization of surface amine groups using trifluoroacetic anhydride

NASA Astrophysics Data System (ADS)

Duchoslav, Jiri; Kehrer, Matthias; Hinterreiter, Andreas; Duchoslav, Vojtech; Unterweger, Christoph; Fürst, Christian; Steinberger, Roland; Stifter, David

2018-06-01

In the current work, chemical derivatization of amine (NH2) groups with trifluoroacetic anhydride (TFAA) as an analytical method to improve the information scope of X-ray photoelectron spectroscopy (XPS) is investigated. TFAA is known to successfully label hydroxyl (OH) groups. With the introduction of a newly developed gas-phase derivatization protocol conducted at ambient pressure and using a catalyst also NH2 groups can now efficiently be labelled with a high yield and without the formation of unwanted by-products. By establishing a comprehensive and self-consistent database of reference binding energies for XPS a promising approach for distinguishing hydroxyl from amine groups is presented. The protocol was verified on different polymers, including poly(allylamine), poly(ethyleneimine), poly(vinylalcohol) and chitosan, the latter one containing both types of addressed chemical groups.

Mechanism and kinetics of the atmospheric degradation of 2-formylcinnamaldehyde with O3 and hydroxyl OH radicals - a theoretical study

NASA Astrophysics Data System (ADS)

Thangamani, D.; Shankar, R.; Vijayakumar, S.; Kolandaivel, P.

2016-10-01

In the present investigation, the reaction mechanism and kinetics of 2-formylcinnamaldehyde (2-FC) with O3 and hydroxyl OH radicals were studied. The reaction of 2-FC with O3 radical are initiated by the formation of primary ozonide, whereas the reaction of 2-FC with the hydroxyl OH radical are initiated by two different ways: (1). H-atom abstraction by hydroxyl OH radical from the -CHO and -CH = CHCHO group of 2-FC (2). Hydroxyl OH addition to the -CH = CHCHO group to the ring-opened 2-FC. These reactions lead to the formation of an alkyl radical. The reaction pathways corresponding to the reactions between 2-FC with O3 and hydroxyl OH radicals have been analysed using density functionals of B3LYP and M06-2X level of methods with the 6-31+G(d,p) basis set. Single-point energy calculations for the most favourable reactive species are determined by B3LYP/6-311++G(d,p) and CCSD(T)/6-31+G(d,p) levels of theory. From the obtained results, the hydroxyl OH addition at C8 position of 2-FC are most favourable than the C9 position of 2-FC. The subsequent reactions of the alkyl radicals, formed from the hydroxyl OH addition at C8 position, are analysed in detail. The individual and overall rate constant for the most favourable reactions are calculated by canonical variational transition theory with small-curvature tunnelling corrections over the temperature range of 278-350 K. The calculated theoretical rate constants are in good agreement with the available experimental data. The Arrhenius plot of the rate constants with the temperature are fitted and the atmospheric lifetimes of the 2-FC with hydroxyl OH radical reaction in the troposphere calculate for the first time, which can be applied to the study on the atmospheric implications. The condensed Fukui function has been verified for the most favourable reaction sites. This study can be regarded as an attempt to investigate the O3-initiated and hydroxyl OH-initiated reaction mechanisms of 2-FC in the atmosphere.

Surface Coverage and Metallicity of ZnO Surfaces from First-Principles Calculations

NASA Astrophysics Data System (ADS)

Zhang, Xiao; Schleife, Andre; The Schleife research Group Team

Zinc oxide (ZnO) surfaces are widely used in different applications such as catalysis, biosensing, and solar cells. These surfaces are, in many cases, chemically terminated by hydroxyl groups. In experiment, a transition of the ZnO surface electronic properties from semiconducting to metallic was reported upon increasing the hydroxyl coverage to more than approximately 80 %. The reason for this transition is not well understood yet. We report on first-principles calculations based on density functional theory for the ZnO [ 10 1 0 ] surface, taking different amounts of hydroxyl coverage into account. We calculated band structures for fully relaxed configurations and verified the existence of this transition. However, we only find the fully covered surface to be metallic. We thus explore the possibility for clustering of the surface-terminating hydroxyl groups based on total-energy calculations. We also found that the valence band maximum consists of oxygen p states from both the surface hydroxyl groups and the surface oxygen atoms of the material. The main contribution to the metallicity is found to be from the hydroxyl groups.

Intramolecular dehydration of biomass-derived sugar alcohols in high-temperature water.

PubMed

Yamaguchi, Aritomo; Muramatsu, Natsumi; Mimura, Naoki; Shirai, Masayuki; Sato, Osamu

2017-01-25

The intramolecular dehydration of biomass-derived sugar alcohols d-sorbitol, d-mannitol, galactitol, xylitol, ribitol, l-arabitol, erythritol, l-threitol, and dl-threitol was investigated in high-temperature water at 523-573 K without the addition of any acid catalysts. d-Sorbitol and d-mannitol were dehydrated into isosorbide and isomannide, respectively, as dianhydrohexitol products. Galactitol was dehydrated into anhydrogalactitols; however, the anhydrogalactitols could not be dehydrated into dianhydrogalactitol products because of the orientation of the hydroxyl groups at the C-3 and C-6 positions. Pentitols such as xylitol, ribitol, and l-arabitol were dehydrated into anhydropentitols. The dehydration rates of the pentitols containing hydroxyl groups in the trans form, which remained as hydroxyl groups in the product tetrahydrofuran, were larger than those containing hydroxyl groups in the cis form because of the structural hindrance caused by the hydroxyl groups in the cis form during the dehydration process. In the case of the tetritols, the dehydration of erythritol was slower than that of threitol, which could also be explained by the structural hindrance of the hydroxyl groups. The dehydration of l-threitol was faster than that of dl-threitol, which implies that molecular clusters were formed by hydrogen bonding between the sugar alcohols in water, which could be an important factor that affects the dehydration process.

Adsorption behaviour of hydrogarnet for humic acid

NASA Astrophysics Data System (ADS)

Maeda, Hirotaka; Kurosaki, Yuichi; Nakayama, Masanobu; Ishida, Emile Hideki; Kasuga, Toshihiro

2018-04-01

Discharge of humic acid (HA) in aqueous environments is a key health and aesthetic issue. The present work investigates the use of hydrogarnet as a novel adsorbent for HA. Hydrogarnet was hydrothermally synthesized with different solvents to control the chemical composition. Hydrogarnet with three types of chemical compositions had better adsorption properties for HA than hydrogarnet with a single chemical composition. Controlling the chemical composition of hydrogarnet increased the number of hydroxyl groups and the overall binding energy of the system, leading to changes in the zeta potential. The enhancement of these adsorption properties is related to the increased numbers of hydroxyl groups on the surface and their diverse binding energies.

Re-engineering an artificial sweetener: transforming sucralose residuals in water via advanced oxidation.

PubMed

Keen, Olya S; Linden, Karl G

2013-07-02

Sucralose is an artificial sweetener persistently present in wastewater treatment plant effluents and aquatic environments impacted by human activity. It has a potential to accumulate in the water cycle due to its resistance to common water and wastewater treatment processes. This study examined UV/H2O2 advanced oxidation and found that hydroxyl substitution of the chlorine atoms on the sucralose molecule can form a carbohydrate consisting of fructose and sugar alcohol, very similar to environmentally benign sucrose. The second-order reaction rate constant for loss of parent molecule via reaction with hydroxyl radical was determined to be (1.56 ± 0.03)·10(9) M(-1)s(-1). The degradation pathway involves substitution of a single chlorine by a hydroxyl group, with cyclic moiety being a preferential site for initial dechlorination. Further reaction leads to full dechlorination of the molecule, presumably via hydroxyl group substitution as well. No direct photolysis by UV wavelengths above 200 nm was observed. Because of its photostability when exposed to UV wavelengths ≥200 nm, known stability with ozone, limits of quantification by mass spectrometry close to or below environmental concentrations (<5 μg/L) without preconcentration, and otherwise stable nature, sucralose can be used as an in situ hydroxyl radical probe for UV-based and ozone-based AOP processes. As a compound safe for human consumption, sucralose makes a suitable full scale hydroxyl radical probe fit even for drinking water treatment plant applications. Its main drawback as a probe is lack of UV detection and as a result a need for mass spectrometry analysis.

Effect of Acid on Surface Hydroxyl Groups on Kaolinite and Montmorillonite

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sihvonen, Sarah K.; Murphy, Kelly A.; Washton, Nancy M.

Mineral dust aerosol participates in heterogeneous chemistry in the atmosphere. In particular, the hydroxyl groups on the surface of aluminosilicate clay minerals are important for heterogeneous atmospheric processes. These functional groups may be altered by acidic processing during atmospheric transport. In this study, we exposed kaolinite (KGa-1b) and montmorillonite (STx-1b) to aqueous sulfuric acid and then rinsed the soluble reactants and products off in order to explore changes to functional groups on the mineral surface. To quantify the changes due to acid treatment of edge hydroxyl groups, we use 19F magic angle spinning nuclear magnetic resonance spectroscopy and a probemore » molecule, 3,3,3-trifluoropropyldimethylchlorosilane. We find that the edge hydroxyl groups (OH) increase in both number and density with acid treatment. Chemical reactions in the atmosphere may be impacted by the increase in OH at the mineral edge.« less

Chemoselective Hydroxyl Group Transformation: An Elusive Target‡

PubMed Central

Trader, Darci J.; Carlson, Erin E.

2012-01-01

The selective reaction of one functional group in the presence of others is not a trivial task. A noteworthy amount of research has been dedicated to the chemoselective reaction of the hydroxyl moiety. This group is prevalent in many biologically important molecules including natural products and proteins. However, targeting the hydroxyl group is difficult for many reasons including its relatively low nucleophilicity in comparison to other ubiquitous functional groups such as amines and thiols. Additionally, many of the developed chemoselective reactions cannot be used in the presence of water. Despite these complications, chemoselective transformation of the hydroxyl moiety has been utilized in the synthesis of complex natural product derivatives, the reaction of tyrosine residues in proteins, the isolation of natural products and is the mechanism of action of myriad drugs. Here, methods for selective targeting of this group, as well as applications of several devised methods, are described. PMID:22695722

Promotional effect of surface hydroxyls on electrochemical reduction of CO 2 over SnO x/Sn electrode

DOE PAGES

Cui, Chaonan; Han, Jinyu; Zhu, Xinli; ...

2016-01-16

In this study, tin oxide (SnO x) formation on tin-based electrode surfaces during CO 2 electrochemical reduction can have a significant impact on the activity and selectivity of the reaction. In the present study, density functional theory (DFT) calculations have been performed to understand the role of SnO x in CO 2 reduction using a SnO monolayer on the Sn(112) surface as a model for SnO x. Water molecules have been treated explicitly and considered actively participating in the reaction. The results showed that H 2O dissociates on the perfect SnO monolayer into two hydroxyl groups symmetrically on the surface.more » CO 2 energetically prefers to react with the hydroxyl, forming a bicarbonate (HCO 3(t)*) intermediate, which can then be reduced to either formate (HCOO*) by hydrogenating the carbon atom or carboxyl (COOH*) by protonating the oxygen atom. Both steps involve a simultaneous Csingle bondO bond breaking. Further reduction of HCOO* species leads to the formation of formic acid in the acidic solution at pH < 4, while the COOH* will decompose to CO and H 2O via protonation. Whereas the oxygen vacancy (VO) in the oxide monolayer maybe formed by the reduction, it can be recovered by H 2O dissociation, resulting in two embedded hydroxyl groups. The results show that the hydroxylated surface with two symmetric hydroxyls is energetically more favorable for CO 2 reduction than the hydroxylated VO surface with two embedded hydroxyls. The reduction potential for the former has a limiting-potential of –0.20 V (RHE), lower than that for the latter (–0.74 V (RHE)). Compared to the pure Sn electrode, the formation of SnO x monolayer on the electrode under the operating conditions promotes CO 2 reduction more effectively by forming surface hydroxyls, thereby providing a new channel via COOH* to the CO formation, although formic acid is still the major reduction product.« less

Effect of the ortho-Hydroxyl Groups on a Bipyridine Ligand of Iridium Complexes for the High-Pressure Gas Generation from the Catalytic Decomposition of Formic Acid.

PubMed

Iguchi, Masayuki; Zhong, Heng; Himeda, Yuichiro; Kawanami, Hajime

2017-12-14

The hydroxyl groups of a 2,2'-bipyridine (bpy) ligand near the metal center activated the catalytic performance of the Ir complex for the dehydrogenation of formic acid at high pressure. The position of the hydroxyl groups on the ligand affected the catalytic durability for the high-pressure H 2 generation through the decomposition of formic acid. The Ir complex with a bipyridine ligand functionalized with para-hydroxyl groups shows a good durability with a constant catalytic activity during the reaction even under high-pressure conditions, whereas deactivation was observed for an Ir complex with a bipyridine ligand with ortho-hydroxyl groups (2). In the presence of high-pressure H 2 , complex 2 decomposed into the ligand and an Ir trihydride complex through the isomerization of the bpy ligand. This work provides the development of a durable catalyst for the high-pressure H 2 production from formic acid. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Structural features, kinetics and SAR study of radical scavenging and antioxidant activities of phenolic and anilinic compounds

PubMed Central

2013-01-01

Background Phenolic compounds are widely distributed in plant kingdom and constitute one of the most important classes of natural and synthetic antioxidants. In the present study fifty one natural and synthetic structurally variant phenolic, enolic and anilinic compounds were examined as antioxidants and radical scavengers against DPPH, hydroxyl and peroxyl radicals. The structural diversity of the used phenolic compounds includes monophenols with substituents frequently present in natural phenols e.g. alkyl, alkoxy, ester and carboxyl groups, besides many other electron donating and withdrawing groups, in addition to polyphenols with 1–3 hydroxyl groups and aminophenols. Some common groups e.g. alkyl, carboxyl, amino and second OH groups were incorporated in ortho, meta and para positions. Results SAR study indicates that the most important structural feature of phenolic compounds required to possess good antiradical and antioxidant activities is the presence of a second hydroxyl or an amino group in o- or p-position because of their strong electron donating effect in these positions and the formation of a stable quinone-like products upon two hydrogen-atom transfer process; otherwise, the presence of a number of alkoxy (in o or p-position) and /or alkyl groups (in o, m or p-position) should be present to stabilize the resulted phenoxyl radical and reach good activity. Anilines showed also similar structural feature requirements as phenols to achieve good activities, except o-diamines which gave low activity because of the high energy of the resulted 1,2-dimine product upon the 2H-transfer process. Enols with ene-1,2-diol structure undergo the same process and give good activity. Good correlations were obtained between DPPH inhibition and inhibition of both OH and peroxyl radicals. In addition, good correlations were obtained between DPPH inhibition and antioxidant activities in sunflower oil and liver homogenate systems. Conclusions In conclusion, the structures of good anti radical and antioxidant phenols and anilines are defined. The obtained good correlations imply that measuring anti DPPH activity can be used as a simple predictive test for the anti hydroxyl and peroxyl radical, and antioxidant activities. Kinetic measurements showed that strong antioxidants with high activity have also high reaction rates indicating that factors stabilizing the phenoxyl radicals lower also the activation energy of the hydrogen transfer process. PMID:23497653

Role of oxygen functional groups in reduced graphene oxide for lubrication

PubMed Central

Gupta, Bhavana; Kumar, Niranjan; Panda, Kalpataru; Kanan, Vigneshwaran; Joshi, Shailesh; Visoly-Fisher, Iris

2017-01-01

Functionalized and fully characterized graphene-based lubricant additives are potential 2D materials for energy-efficient tribological applications in machine elements, especially at macroscopic contacts. Two different reduced graphene oxide (rGO) derivatives, terminated by hydroxyl and epoxy-hydroxyl groups, were prepared and blended with two different molecular weights of polyethylene glycol (PEG) for tribological investigation. Epoxy-hydroxyl-terminated rGO dispersed in PEG showed significantly smaller values of the friction coefficient. In this condition, PEG chains intercalate between the functionalized graphene sheets, and shear can take place between the PEG and rGO sheets. However, the friction coefficient was unaffected when hydroxyl-terminated rGO was coupled with PEG. This can be explained by the strong coupling between graphene sheets through hydroxyl units, causing the interaction of PEG with the rGO to be non- effective for lubrication. On the other hand, antiwear properties of hydroxyl-terminated rGO were significantly enhanced compared to epoxy-hydroxyl functionalized rGO due to the integrity of graphene sheet clusters. PMID:28344337

Acid-degradable and bioerodible modified polyhydroxylated materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Frechet, Jean M. J.; Bachelder, Eric M.; Beaudette, Tristan T.

Compositions and methods of making a modified polyhydroxylated polymer comprising a polyhydroxylated polymer having reversibly modified hydroxyl groups, whereby the hydroxyl groups are modified by an acid-catalyzed reaction between a polydroxylated polymer and a reagent such as acetals, aldehydes, vinyl ethers and ketones such that the modified polyhydroxylated polymers become insoluble in water but freely soluble in common organic solvents allowing for the facile preparation of acid-sensitive materials. Materials made from these polymers can be made to degrade in a pH-dependent manner. Both hydrophobic and hydrophilic cargoes were successfully loaded into particles made from the present polymers using single andmore » double emulsion techniques, respectively. Due to its ease of preparation, processability, pH-sensitivity, and biocompatibility, of the present modified polyhydroxylated polymers should find use in numerous drug delivery applications.« less

IDENTIFICATION AND QUANTIFICATION OF AEROSOL POLAR OXYGENATED COMPOUNDS BEARING CARBOXYLIC AND/OR HYDROXYL GROUPS. 1. METHOD DEVELOPMENT

EPA Science Inventory

In this study, a new analytical technique was developed for the identification and quantification of multi-functional compounds containing simultaneously at least one hydroxyl or one carboxylic group, or both. This technique is based on derivatizing first the carboxylic group(s) ...

2-Pyridinyl Thermolabile Groups as General Protectants for Hydroxyl, Phosphate, and Carboxyl Functions.

PubMed

Brzezinska, Jolanta; Witkowska, Agnieszka; Kaczyński, Tomasz P; Krygier, Dominika; Ratajczak, Tomasz; Chmielewski, Marcin K

2017-03-02

Application of 2-pyridinyl thermolabile protecting groups (2-PyTPGs) for protection of hydroxyl, phosphate, and carboxyl functions is presented in this unit. Their characteristic feature is a unique removal process following the intramolecular cyclization mechanism and induced only by temperature rise. Deprotection rate of 2-PyTPGs is dependent on certain parameters, such as solvent (aqueous or non-aqueous medium), pH values, and electron distribution in a pyridine ring. The presented approach pertains not only to protecting groups but also to an advanced system of controlling certain properties of 2-pyridinyl derivatives. We improved the "chemical switch" method, allowing us to regulate the protecting group stability by inversing the electron distribution in 2-PyTPG. Together with pH values manipulation, this allows us to regulate the protecting group stability. Moreover, phosphite cyclization to oxazaphospholidine provides a very stable but easily reversible tool for phosphate protection/modifications. For all TPGs we confirmed their utility in a system of protecting groups. This concept can contribute to designing the general protecting group that could be useful in bioorganic chemistry. © 2017 by John Wiley & Sons, Inc. Copyright © 2017 John Wiley & Sons, Inc.

Thiaflavan scavenges radicals and inhibits DNA oxidation: a story from the ferrocene modification.

PubMed

Lai, Hai-Wang; Liu, Zai-Qun

2014-06-23

4-Thiaflavan is a sulfur-substituted flavonoid with a benzoxathiin scaffold. The aim of this work is to compare abilities of sulfur and oxygen atom, hydroxyl groups, and ferrocene moiety at different positions of 4-thiaflavan to trap radicals and to inhibit DNA oxidation. It is found that abilities of thiaflavans to trap radicals and to inhibit DNA oxidation are increased in the presence of ferrocene moiety and are further improved by the electron-donating group attaching to thiaflavan skeleton. It can be concluded that the ferrocene moiety plays the major role for thiaflavans to be antioxidants even in the absence of phenolic hydroxyl groups. On the other hand, the antioxidant effectiveness of phenolic hydroxyl groups in thiaflavans can be improved by the electron-donating group. The influences of sulfur and oxygen atoms in thiaflavans on the antioxidant property of para-hydroxyl group exhibit different manners when the thiaflavans are used to trap radicals and to inhibit DNA oxidation. Copyright © 2014 Elsevier Masson SAS. All rights reserved.

Influence of surface hydroxylation on 3-aminopropyltriethoxysilane growth mode during chemical functionalization of GaN Surfaces: an angle-resolved X-ray photoelectron spectroscopy Study.

PubMed

Arranz, A; Palacio, C; García-Fresnadillo, D; Orellana, G; Navarro, A; Muñoz, E

2008-08-19

A comparative study of the chemical functionalization of undoped, n- and p-type GaN layers grown on sapphire substrates by metal-organic chemical vapor deposition was carried out. Both types of samples were chemically functionalized with 3-aminopropyltriethoxysilane (APTES) using a well-established silane-based approach for functionalizing hydroxylated surfaces. The untreated surfaces as well as those modified by hydroxylation and APTES deposition were analyzed using angle-resolved X-ray photoelectron spectroscopy. Strong differences were found between the APTES growth modes on n- and p-GaN surfaces that can be associated with the number of available hydroxyl groups on the GaN surface of each sample. Depending on the density of surface hydroxyl groups, different mechanisms of APTES attachment to the GaN surface take place in such a way that the APTES growth mode changes from a monolayer to a multilayer growth mode when the number of surface hydroxyl groups is decreased. Specifically, a monolayer growth mode with a surface coverage of approximately 78% was found on p-GaN, whereas the formation of a dense film, approximately 3 monolayers thick, was observed on n-GaN.

Action mechanism of tyrosinase on meta- and para-hydroxylated monophenols.

PubMed

Fenoll, L G; Rodríguez-López, J N; Varón, R; García-Ruiz, P A; García-Cánovas, F; Tudela, J

2000-04-01

The relationship between the structure and activity of meta- and para-hydroxylated monophenols was studied during their tyrosinase-catalysed hydroxylation and the rate-limiting steps of the reaction mechanism were identified. The para-hydroxylated substrates permit us to study the effect of a substituent (R) in the carbon-1 position (C-1) of the benzene ring on the nucleophilic attack step, while the meta group permits a similar study of the effect on the electrophilic attack step. Substrates with a -OCH3 group on C-1, as p-hydroxyanisol (4HA) and m-hydroxyanisol (3HA), or with a -CH2OH group, as p-hydroxybenzylalcohol (4HBA) and m-hydroxybenzylalcohol (3HBA), were used because the effect of the substituent (R) size was assumed to be similar. However, the electron-donating effect of the -OCH3 group means that the carbon-4 position (C-4) is favoured for nucleophilic attack (para-hydroxylated substrates) or for electrophilic attack (meta-hydroxylated substrates). The electron-attracting effect of the -CH2OH group has the opposite effect, hindering nucleophilic (para) or electrophilic (meta) attack of C-4. The experimental data point to differences between the maximum steady-state rate (V(M)Max) of the different substrates, the value of this parameter depends on the nucleophilic and electrophilic attack. However, differences are greatest in the Michaelis constants (K(M)m), with the meta-hydroxylated substrates having very large values. The catalytic efficiency k(M)cat/K(M)m is much greater for thepara-hydroxylated substrates although it varies greatly between one substrate and the other. However, it varies much less in the meta-hydroxylated substrates since this parameter describes the power of the nucleophilic attack, which is weaker in the meta OH. The large increase in the K(M)m of the meta-hydroxylated substrates might suggest that the phenolic OH takes part in substrate binding. Since this is a weaker nucleophil than the para-hydroxylated substrates, the binding constant decreases, leading to an increase in K(M)m. The catalytic efficiency of tyrosinase on a monophenol (para or meta) is directly related to the nucleophilic power of the oxygen of the phenolic OH. The oxidation step is not limiting since if this were the case, the para and meta substrates would have the same V(M)max. The small difference between the absolute values of V(M)max suggests that the rate constants of the nucleophilic and electrophilic attacks are on the same order of magnitude.

Variation in Optoelectronic Properties of Azo Dye-Sensitized TiO 2 Semiconductor Interfaces with Different Adsorption Anchors: Carboxylate, Sulfonate, Hydroxyl and Pyridyl Groups

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Lei; Cole, Jacqueline M.; Dai, Chencheng

2014-05-28

The optoelectronic properties of four azo dye-sensitized TiO2 interfaces are systematically studied as a function of a changing dye anchoring group: carboxylate, sulfonate, hydroxyl, and pyridyl. The variation in optoelectronic properties of the free dyes and those in dye/TiO 2 nanocomposites are studied both experimentally and computationally, in the context of prospective dye-sensitized solar cell (DSSC) applications. Experimental UV/vis absorption spectroscopy, cyclic voltammetry, and DSSC device performance testing reveal a strong dependence on the nature of the anchor of the optoelectronic properties of these dyes, both in solution and as dye/TiO2 nanocomposites. First-principles calculations on both an isolated dye/TiO2 clustermore » model (using localized basis sets) and each dye modeled onto the surface of a 2D periodic TiO2 nanostructure (using plane wave basis sets) are presented. Detailed examination of these experimental and computational results, in terms of light harvesting, electron conversion and photovoltaic device performance characteristics, indicates that carboxylate is the best anchoring group, and hydroxyl is the worst, whereas sulfonate and pyridyl groups exhibit competing potential. Different sensitization solvents are found to affect critically the extent of dye adsorption achieved in the dye-sensitization of the TiO2 semiconductor, especially where the anchor is a pyridyl group.« less

Glucuronidation of 6 alpha-hydroxy bile acids by human liver microsomes.

PubMed Central

Radomińska-Pyrek, A; Zimniak, P; Irshaid, Y M; Lester, R; Tephly, T R; St Pyrek, J

1987-01-01

The glucuronidation of 6-hydroxylated bile acids by human liver microsomes has been studied in vitro; for comparison, several major bile acids lacking a 6-hydroxyl group were also investigated. Glucuronidation rates for 6 alpha-hydroxylated bile acids were 10-20 times higher than those of substrates lacking a hydroxyl group in position 6. The highest rates measured were for hyodeoxy- and hyocholic acids, and kinetic analyses were carried out using these substrates. Rigorous product identification by high-field proton nuclear magnetic resonance and by electron impact mass spectrometry of methyl ester/peracetate derivatives revealed that 6-O-beta-D-glucuronides were the exclusive products formed in these enzymatic reactions. These results, together with literature data, indicate that 6 alpha-hydroxylation followed by 6-O-glucuronidation constitutes an alternative route of excretion of toxic hydrophobic bile acids. PMID:3110212

Reaction of hydroxy and carbonyl compounds with sulfur tetrafluoride. XVI. Reactions of vicinal dihydric alcohols with sulfur tetrafluoride (in Russian)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Burmakov, A.I.; Hassanein, S.M.; Kunshenko, B.V.

1986-11-20

During the action of sulfur tetrafluoride on ethanediol, d,l-1,2-propanediol, d,l-3,3,3-trifluoro-1,2-propanediol regioselective substitution of one of the hydroxyl groups by a fluorine atom occurs, depending on the electronic nature of the groups present in the molecule. The second hydroxy group in converted into a fluorosulfite group.

Dissociative adsorption of a multifunctional compound on a semiconductor surface: a theoretical study of the adsorption of hydroxylamine on Ge(100).

PubMed

Park, Hyunkyung; Kim, Do Hwan

2018-06-06

The adsorption behavior of hydroxylamine on a Ge(100) surface was investigated using density functional theory (DFT) calculations. These calculations predicted that hydroxylamine, a multifunctional compound consisting of a hydroxyl group and an amine group, would initially become adsorbed through N-dative bonding, or alternatively through the hydroxyl group via O-H dissociative adsorption. An N-O dissociative reaction may also occur, mainly via N-dative molecular adsorption, and the N-O dissociative product was calculated to be the most stable of all the possible adsorption structures. The calculations furthermore indicated the formation of the N-O dissociative product from the N-dative structure to be nearly barrierless and the dissociated hydroxyl and amine groups to be bonded to two Ge atoms of adjacent Ge dimers. Simulated STM images suggested the change in electron density that would occur upon adsorption of hydroxylamine in various adsorption configurations, and specifically indicated the N-O dissociative product to have greater electron density around the amine groups, and the hydroxyl groups to mainly contribute electron density to the unoccupied electronic states.

Structure-Activity and Lipophilicity Relationships of Selected Antibacterial Natural Flavones and Flavanones of Chilean Flora.

PubMed

Echeverría, Javier; Opazo, Julia; Mendoza, Leonora; Urzúa, Alejandro; Wilkens, Marcela

2017-04-10

In this study, we tested eight naturally-occurring flavonoids-three flavanones and five flavones-for their possible antibacterial properties against four Gram-positive and four Gram-negative bacteria. Flavonoids are known for their antimicrobial properties, and due their structural diversity; these plant-derived compounds are a good model to study potential novel antibacterial mechanisms. The lipophilicity and the interaction of antibacterial compounds with the cell membrane define the success or failure to access its target. Therefore, through the determination of partition coefficients in a non-polar/aqueous phase, lipophilicity estimation and the quantification of the antibacterial activity of different flavonoids, flavanones, and flavones, a relationship between these parameters was assessed. Active flavonoids presented diffusion coefficients between 9.4 × 10 -10 and 12.3 × 10 -10 m²/s and lipophilicity range between 2.0 to 3.3. Active flavonoids against Gram-negative bacteria showed a narrower range of lipophilicity values, compared to active flavonoids against Gram-positive bacteria, which showed a wide range of lipophilicity and cell lysis. Galangin was the most active flavonoid, whose structural features are the presence of two hydroxyl groups located strategically on ring A and the absence of polar groups on ring B. Methylation of one hydroxyl group decreases the activity in 3- O -methylgalangin, and methylation of both hydroxyl groups caused inactivation, as shown for 3,7- O -dimethylgalangin. In conclusion, the amphipathic features of flavonoids play a crucial role in the antibacterial activity. In these compounds, hydrophilic and hydrophobic moieties must be present and could be predicted by lipophilicity analysis.

Bacterial Conversion of Hydroxylamino Aromatic Compounds by both Lyase and Mutase Enzymes Involves Intramolecular Transfer of Hydroxyl Groups

PubMed Central

Nadeau, Lloyd J.; He, Zhongqi; Spain, Jim C.

2003-01-01

Hydroxylamino aromatic compounds are converted to either the corresponding aminophenols or protocatechuate during the bacterial degradation of nitroaromatic compounds. The origin of the hydroxyl group of the products could be the substrate itself (intramolecular transfer mechanism) or the solvent water (intermolecular transfer mechanism). The conversion of hydroxylaminobenzene to 2-aminophenol catalyzed by a mutase from Pseudomonas pseudoalcaligenes JS45 proceeds by an intramolecular hydroxyl transfer. The conversions of hydroxylaminobenzene to 2- and 4-aminophenol by a mutase from Ralstonia eutropha JMP134 and to 4-hydroxylaminobenzoate to protocatechuate by a lyase from Comamonas acidovorans NBA-10 and Pseudomonas sp. strain 4NT were proposed, but not experimentally proved, to proceed by the intermolecular transfer mechanism. GC-MS analysis of the reaction products formed in H218O did not indicate any 18O-label incorporation during the conversion of hydroxylaminobenzene to 2- and 4-aminophenols catalyzed by the mutase from R. eutropha JMP134. During the conversion of 4-hydroxylaminobenzoate catalyzed by the hydroxylaminolyase from Pseudomonas sp. strain 4NT, only one of the two hydroxyl groups in the product, protocatechuate, was 18O labeled. The other hydroxyl group in the product must have come from the substrate. The mutase in strain JS45 converted 4-hydroxylaminobenzoate to 4-amino-3-hydroxybenzoate, and the lyase in Pseudomonas strain 4NT converted hydroxylaminobenzene to aniline and 2-aminophenol but not to catechol. The results indicate that all three types of enzyme-catalyzed rearrangements of hydroxylamino aromatic compounds proceed via intramolecular transfer of hydroxyl groups. PMID:12732549

Characterization and Neutralization of Recovered Lewisite Munitions

DTIC Science & Technology

2006-12-01

chlorine being rated as 1.0.51 Oxidative Species Relative Oxidizing Strength* Fluorine 2.23 Hydroxyl Radical 2.06 Atomic Oxygen 1.78 Hydrogen...containing carbon-carbon double bonds, aldehyde groups or hydroxyl groups. As an electrophile , the permnanganate ion is strongly attracted to the electrons

Chemisorption of hydrogen atoms and hydroxyl groups on stretched graphene: A coupled QM/QM study

NASA Astrophysics Data System (ADS)

Katin, Konstantin P.; Prudkovskiy, Vladimir S.; Maslov, Mikhail M.

2017-09-01

Using the density functional theory coupled with the nonorthogonal tight-binding model, we analyze the chemisorption of hydrogen atoms and hydroxyl groups on the unstrained and stretched graphene sheets. Drawback of finite cluster model of graphene for the chemisorption energy calculation in comparison with the QM/QM approach applied is discussed. It is shown that the chemisorption energy for the hydroxyl group is sufficiently lower than for hydrogen at stretching up to 7.5%. The simultaneous paired chemisorption of hydrogen and hydroxyl groups on the same hexagon has also been examined. Adsorption of two radicals in ortho and para positions is found to be more energetically favorable than those in meta position at any stretching considered. In addition the energy difference between adsorbent pairs in ortho and para positions decreases as the stretching rises. It could be concluded that the graphene stretching leads to the loss of preferred mutual arrangement of two radicals on its surface.

Polyvinyl alcohol cross-linked with two aldehydes

NASA Technical Reports Server (NTRS)

Sheibley, D. W.; Rieker, L. L.; Hsu, L. C.; Manzo, M. A. (Inventor)

1982-01-01

A film forming polyvinyl alcohol resin is admixed, in aqueous solution, with a dialdehyde crosslinking agent which is capable of crosslinking the polyvinyl alcohol resin and a water soluble acid aldehyde containing a reactive aldehyde group capable of reacting with hydroxyl groups in the polyvinyl alcohol resin and an ionizable acid hydrogen atom. The dialdehyde is present in an amount sufficient to react with from 1 to 20% by weight of the theoretical amount required to react with all of the hydroxyl groups of the polyvinyl alcohol. The amount of acid aldehyde is from 1 to 50% by weight, same basis, and is sufficient to reduce the pH of the aqueous admixture to 5 or less. The admixture is then formed into a desired physical shape, such as by casting a sheet or film, and the shaped material is then heated to simultaneously dry and crosslink the article.

Epoxy Monomers Cured by High Cellulosic Nanocrystal Loading.

PubMed

Khelifa, Farid; Habibi, Youssef; Bonnaud, Leila; Dubois, Philippe

2016-04-27

The present study focuses on the use of cellulose nanocrystals (CNC) as the main constituent of a nanocomposite material and takes advantage of hydroxyl groups, characteristic of the CNC chemical structure, to thermally cross-link an epoxy resin. An original and simple approach is proposed, based on the collective sticking of CNC building blocks with the help of a DGEBA/TGPAP-based epoxy resin. Scientific findings suggest that hydroxyl groups act as a toxic-free cross-linking agent of the resin. The enhanced protection against water degradation as compared to neat CNC film and the improvement of mechanical properties of the synthesized films are attributed to a good compatibility between the CNC and the resin. Moreover, the preservation of CNC optical properties at high concentrations opens the way to applying these materials in photonic devices.

Fast MAS 1H NMR Study of Water Adsorption and Dissociation on the (100) Surface of Ceria Nanocubes: A Fully Hydroxylated, Hydrophobic Ceria Surface

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gill, Lance; Beste, Ariana; Chen, Banghao

1H nuclear magnetic resonance (NMR) spectroscopy was used to study hydroxylic surface species on ceria nanocubes, a crystalline, high-surface-area CeO 2 that presents mostly (100) facets. Water adsorption and desorption experiments in combination with fast magic angle spinning (MAS, 20–40 kHz) 1H NMR provide high-resolution 1H spectra that allow the observation of ten resonance bands (water or hydroxyl) on or under the (100) surface. Assignments were made using a combination of adsorption and temperature-programmed desorption, quantitative spin counting, deuterium exchange, spin–lattice (T 1) and spin–spin (T 2) relaxation, and DFT calculations. In air, the (100) surface exists as a fullymore » hydroxylated surface. Water adsorption and dissociation on dry ceria surfaces occur first at oxygen vacancies, but Ce 3+ centers are not required since water dissociation is barrier-less on the fully oxidized surface. Surface $-$OH functionality occurs in two resolved bands representing isolated $-$OH (1 ppm) and hydrogen-bonded $-$OH (9 ppm), the latter being dominant. Deuterium exchange of surface hydroxyls with D 2O does not occur under mild or forcing conditions. Despite large differences in the T 1 of surface hydroxyls and physisorbed water, surface hydroxyl T 1 values are independent of the presence or absence of physisorbed water, demonstrating that the protons within these two functional group pools are not in intimate contact. These observations show that, once hydroxylated, the surface $-$OH functionality preferentially forms hydrogen bonds with surface lattice oxygen, i.e., the hydroxylated (100) surface of ceria is hydrophobic. Near this surface it is energetically more favorable for physisorbed water to hydrogen bond to itself rather than to the surface. DFT calculations support this notion. Impurity Na + remaining in incompletely washed ceria nanocubes increases the surface hydrophilicity. In conclusion, sharp, low-field resonances observed in spectra of noncalcined nanocubes arise from kinetically trapped subsurface $-$OH.« less

Fast MAS 1H NMR Study of Water Adsorption and Dissociation on the (100) Surface of Ceria Nanocubes: A Fully Hydroxylated, Hydrophobic Ceria Surface

DOE PAGES

Gill, Lance; Beste, Ariana; Chen, Banghao; ...

2017-03-22

1H nuclear magnetic resonance (NMR) spectroscopy was used to study hydroxylic surface species on ceria nanocubes, a crystalline, high-surface-area CeO 2 that presents mostly (100) facets. Water adsorption and desorption experiments in combination with fast magic angle spinning (MAS, 20–40 kHz) 1H NMR provide high-resolution 1H spectra that allow the observation of ten resonance bands (water or hydroxyl) on or under the (100) surface. Assignments were made using a combination of adsorption and temperature-programmed desorption, quantitative spin counting, deuterium exchange, spin–lattice (T 1) and spin–spin (T 2) relaxation, and DFT calculations. In air, the (100) surface exists as a fullymore » hydroxylated surface. Water adsorption and dissociation on dry ceria surfaces occur first at oxygen vacancies, but Ce 3+ centers are not required since water dissociation is barrier-less on the fully oxidized surface. Surface $-$OH functionality occurs in two resolved bands representing isolated $-$OH (1 ppm) and hydrogen-bonded $-$OH (9 ppm), the latter being dominant. Deuterium exchange of surface hydroxyls with D 2O does not occur under mild or forcing conditions. Despite large differences in the T 1 of surface hydroxyls and physisorbed water, surface hydroxyl T 1 values are independent of the presence or absence of physisorbed water, demonstrating that the protons within these two functional group pools are not in intimate contact. These observations show that, once hydroxylated, the surface $-$OH functionality preferentially forms hydrogen bonds with surface lattice oxygen, i.e., the hydroxylated (100) surface of ceria is hydrophobic. Near this surface it is energetically more favorable for physisorbed water to hydrogen bond to itself rather than to the surface. DFT calculations support this notion. Impurity Na + remaining in incompletely washed ceria nanocubes increases the surface hydrophilicity. In conclusion, sharp, low-field resonances observed in spectra of noncalcined nanocubes arise from kinetically trapped subsurface $-$OH.« less

Advance in dietary polyphenols as aldose reductases inhibitors: structure-activity relationship aspect.

PubMed

Xiao, Jianbo; Ni, Xiaoling; Kai, Guoyin; Chen, Xiaoqing

2015-01-01

The dietary polyphenols as aldose reductases inhibitors (ARIs) have attracted great interest among researchers. The aim of this review is to give an overview of the research reports on the structure-activity relationship of dietary polyphenols inhibiting aldose reductases (AR). The molecular structures influence the inhibition of the following: (1) The methylation and methoxylation of the hydroxyl group at C3, C3', and C4' of flavonoids decreased or little affected the inhibitory potency. However, the methylation and methoxylation of the hydroxyl group at C5, C6, and C8 significantly enhanced the inhibition. Moreover, the methylation and methoxylation of C7-OH influence the inhibitory activity depending on the substitutes on rings A and B of flavonoids. (2) The glycosylation on 3-OH of flavonoids significantly increased or little affected the inhibition. However, the glycosylation on 7-OH and 4'-OH of flavonoids significantly decreased the inhibition. (3) The hydroxylation on A-ring of flavones and isoflavones, especially at positions 5 and 7, significantly improved the inhibition and the hydroxylation on C3' and C4' of B-ring of flavonoids remarkably enhanced the inhibition; however, the hydroxylation on the ring C of flavones significantly weakened the inhibition. (4) The hydrogenation of the C2=C3 double bond of flavones reduced the inhibition. (5) The hydrogenation of α=β double bond of stilbenes hardly affected the inhibition and the hydroxylation on C3' of stilbenes decreased the inhibition. Moreover, the methylation of the hydroxyl group of stilbenes obviously reduced the activity. (6) The hydroxylation on C4 of chalcone significantly increased the inhibition and the methylation on C4 of chalcone remarkably weakened the inhibition.

Hydrogen-bond rich ionic liquids with hydroxyl cationic tails

NASA Astrophysics Data System (ADS)

Deng, Li; Shi, Rui; Wang, Yanting; Ou-Yang, Zhong-Can

2013-02-01

To investigate if the amphiphilic feature exhibited in ionic liquids (ILs) with nonpolar cationic tails still exists in ILs with polar tails, by performing molecular dynamics simulations for 1-(8-hydroxyoctyl)-3-methyl-imidazolium nitrate (COH) and 1-octyl-3-methyl-imidazolium nitrate (C8), we found that, in COH, cationic tail groups can no longer aggregate to form separated nonpolar tail domains, instead hydroxyl groups form a rich number of hydrogen bonds with other groups, indicating that the hydroxyl substituent changes the IL system from an amphiphilic liquid to a polar liquid. Due to the large amount of hydrogen bonds, COH has slower dynamics than C8.

Distribution of Hydroxyl Groups in Kukersite Shale Oil: Quantitative Determination Using Fourier Transform Infrared (FT-IR) Spectroscopy.

PubMed

Baird, Zachariah Steven; Oja, Vahur; Järvik, Oliver

2015-05-01

This article describes the use of Fourier transform infrared (FT-IR) spectroscopy to quantitatively measure the hydroxyl concentrations among narrow boiling shale oil cuts. Shale oil samples were from an industrial solid heat carrier retort. Reference values were measured by titration and were used to create a partial least squares regression model from FT-IR data. The model had a root mean squared error (RMSE) of 0.44 wt% OH. This method was then used to study the distribution of hydroxyl groups among more than 100 shale oil cuts, which showed that hydroxyl content increased with the average boiling point of the cut up to about 350 °C and then leveled off and decreased.

Polarizable continuum model associated with the self-consistent-reaction field for molecular adsorbates at the interface.

PubMed

Wang, Jing-Bo; Ma, Jian-Yi; Li, Xiang-Yuan

2010-01-07

In this work, a new procedure has been developed in order to realize the self-consistent-reaction field computation for interfacial molecules. Based on the extension of the dielectric polarizable continuum model, the quantum-continuum calculations for interfacial molecules have been carried out. This work presents an investigation into how the molecular structure influences the adsorbate-solvent interaction and consequently alters the orientation angle at the air/water interface. Taking both electrostatic and non-electrostatic energies into account, we investigate the orientation behavior of three interfacial molecules, 2,6-dimethyl-4-hydroxy-benzonitrile, 3,5-dimethyl-4-hydroxy-benzonitrile and p-cyanophenol, at the air/water interface. The results show that the hydrophilic hydroxyl groups in 2,6-dimethyl-4-hydroxy-benzonitrile and in p-cyanophenol point from the air to the water side, but the hydroxyl group in 3,5-dimethyl-4-hydroxy-benzonitrile takes the opposite direction. Our detailed analysis reveals that the opposite orientation of 3,5-dimethyl-4-hydroxy-benzonitrile results mainly from the cavitation energy. The different orientations of the hydrophilic hydroxyl group indicate the competition of electrostatic and cavitation energies. The theoretical prediction gives a satisfied explanation of the most recent sum frequency generation measurement for these molecules at the interface.

Possible mechanism of structural incorporation of Al into diatomite during the deposition process I. Via a condensation reaction of hydroxyl groups.

PubMed

Liu, Dong; Yu, Wenbin; Deng, Liangliang; Yuan, Weiwei; Ma, Lingya; Yuan, Peng; Du, Peixin; He, Hongping

2016-01-01

The structural incorporation of aluminium (Al) into diatomite is investigated by preparing several Al-diatomite composites by loading an Al precursor, hydroxyl aluminum polymer (Al13), onto the surface of diatomite and heating at various temperatures. The results indicate that Al was incorporated and implanted into the structure of diatomite by the condensation reaction of the hydroxyl groups of Al13 and diatomite, and the Si-O-Al(OH) groups were formed during the condensation reaction. Al incorporation by the condensation reaction of hydroxyl groups of Al13 with single silanols of diatomite occurred more readily than that with geminal silanols. The Al incorporation increased solid acidity of diatomite after Al incorporation. The acidity improvement was various for different types of acid sites, depending on the preparation temperature of the Al-incorporated diatomite. Both Brønsted and Lewis acid sites increased greatly after heating at 250 and 350 °C, but only L acid sites significantly improved after heating at 500 °C. These results demonstrate that the structural incorporation of Al(3+) ions into diatomite can occur by the condensation reaction of the hydroxyl groups of the Al precursors and diatomite. Moreover, the rich solid acid sites of Al-incorporated diatomite show its promising application as a solid acid catalyst. Copyright © 2015 Elsevier Inc. All rights reserved.

Hydrogen speciation in hydrated layers on nuclear waste glass

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aines, R.D.; Weed, H.C.; Bates, J.K.

1987-01-15

The hydration of an outer layer on nuclear waste glasses is known to occur during leaching, but the actual speciation of hydrogen (as water or hydroxyl groups) in these layers has not been determined. As part of the Nevada Nuclear Waste Storage Investigations Project, we have used infrared spectroscopy to determine hydrogen speciations in three nuclear waste glass compositions (SRL-131 & 165, and PNL 76-68), which were leached at 90{sup 0}C (all glasses) or hydrated in a vapor-saturated atmosphere at 202{sup 0}C (SRL-131 only). Hydroxyl groups were found in the surface layers of all the glasses. Molecular water was foundmore » in the surface of SRL-131 and PNL 76-68 glasses that had been leached for several months in deionized water, and in the vapor-hydrated sample. The water/hydroxyl ratio increases with increasing reaction time; molecular water makes up most of the hydrogen in the thick reaction layers on vapor-phase hydrated glass while only hydroxyl occurs in the least reacted samples. Using the known molar absorptivities of water and hydroxyl in silica-rich glass the vapor-phase layer contained 4.8 moles/liter of molecular water, and 0.6 moles water in the form hydroxyl. A 15 {mu}m layer on SRL-131 glass formed by leaching at 90{sup 0}C contained a total of 4.9 moles/liter of water, 2/3 of which was as hydroxyl. The unreacted bulk glass contains about 0.018 moles/liter water, all as hydroxyl. The amount of hydrogen added to the SRL-131 glass was about 70% of the original Na + Li content, not the 300% that would result from alkali=hydronium ion interdiffusion. If all the hydrogen is then assumed to be added as the result of alkali-H{sup +} interdiffusion, the molecular water observed may have formed from condensation of the original hydroxyl groups.« less

The size of the hydroxyl group and its contribution to the affinity of atropine for muscarine-sensitive acetylcholine receptors.

PubMed Central

Barlow, R. B.; Ramtoola, S.

1980-01-01

1 From measurements of the affinity constants of hydratropyltropine and its methiodide for muscarine-sensitive acetylcholine receptors in the guinea-pig ileum, the increment in log K for the hydroxyl group in atropine is 2.06 and in the methiodide it is 2.16. These effects are slightly bigger than any so far recorded with these receptors. 2 The estimate of the increment in apparent molal volume for the hydroxyl group is 1.1 cm3/mol in atropine and 1.0 cm3/mol in the methobromide. 3 The large effect of the group on affinity may be linked to its small apparent size in water as suggested in the previous paper. PMID:7470742

Materials for use as proton conducting membranes for fuel cells

DOEpatents

Einsla, Brian R [Blacksburg, VA; McGrath, James E [Blacksburg, VA

2009-01-06

A family of polymers having pendent sulfonate moieties connected to polymeric main chain phenyl groups are described. These polymers are prepared by the steps of polymerization (using a monomer with a phenyl with an alkoxy substitution), deportation by converting the alkoxy to a hydroxyl, and functionalization of the polymer with a pendant sulfonate group. As an example, sulfonated poly(arylene ether sulfone) copolymers with pendent sulfonic acid groups are synthesized by the direct copolymerization of methoxy-containing poly(arylene ether sulfone)s, then converting the methoxy groups to the reactive hydroxyl form, and finally functionalizing the hydroxyl form with proton-conducting sites through nucleophilic substitution. The family of polymers may have application in proton exchange membranes and in other applications.

Synthetic route to meso-tetra hydrocarbyl or substituted hydrocarbyl porphyrins and derivatives

DOEpatents

Wijesekera, T.P.; Wagner, R.W.

1993-08-31

The hydroxyl group in a pyrrolic compound having in the 2-position thereof a group having the formula R(OH)CH-R is hydrocarbyl or substituted hydrocarbyl, is replaced by a group, for example a p-nitrobenzoate group, having better leaving properties than those of hydroxyl for a subsequent self-condensation and cyclization of the pyrrolic compound to form a meso-hydrocarbyl or meso-substituted hydrocarbyl porphyrin.

Synthetic route to meso-tetra hydrocarbyl or substituted hydrocarbyl porphyrins and derivatives

DOEpatents

Wijesekera, Tilak P.; Wagner, Richard W.

1993-01-01

The hydroxyl group in a pyrrolic compound having in the 2-position thereof a group having the formula R(OH)CH--R is hydrocarbyl or substituted hydrocarbyl, is replaced by a group, for example a p-nitrobenzoate group, having better leaving properties than those of hydroxyl for a subsequent self-condensation and cyclization of the pyrrolic compound to form a meso-hydrocarbyl or meso-substituted hydrocarbyl porphyrin.

Characterization and Neutralization of Arsenical-Based WWII Era Chemical Munition Fills

DTIC Science & Technology

2006-08-01

Fluorine 2.23 Hydroxyl Radical 2.06 Atomic Oxygen 1.78 Hydrogen Peroxide 1.31 Perhydroxyl Radical 1.25 Permanganate 1.24 Hypobromous Acid 1.17 Chlorine...containing carbon-carbon double bonds, aldehyde groups or hydroxyl groups. As an electrophile , the permanganate ion is strongly attracted to the

Sphingolipid hydroxylation in mammals, yeast and plants - An integrated view.

PubMed

Marquês, Joaquim Trigo; Susana Marinho, H; de Almeida, Rodrigo Freire Martins

2018-05-07

This review is focused on sphingolipid backbone hydroxylation, a small but widespread structural feature, with profound impact on membrane biophysical properties. We start by summarizing sphingolipid metabolism in mammalian cells, yeast and plants, focusing on how distinct hydroxylation patterns emerge in different eukaryotic kingdoms. Then, a comparison of the biophysical properties in membrane model systems and cellular membranes from diverse organisms is made. From an integrative perspective, these results can be rationalized considering that superficial hydroxyl groups in the backbone of sphingolipids (by intervening in the H-bond network) alter the balance of favorable interactions between membrane lipids. They may strengthen the bonding or compete with other hydroxyl groups, in particular the one of membrane sterols. Different sphingolipid hydroxylation patterns can stabilize/disrupt specific membrane domains or change whole plasma membrane properties, and therefore be important in the control of protein distribution, function and lateral diffusion and in the formation and overtime stability of signaling platforms. The recent examples explored throughout this review unveil a potentially key role for sphingolipid backbone hydroxylation in both physiological and pathological situations, as they can be of extreme importance for the proper organization of cell membranes in mammalian cells, yeast and, most likely, also in plants. Copyright © 2017. Published by Elsevier Ltd.

Hydroxylation of organic polymer surface: method and application.

PubMed

Yang, Peng; Yang, Wantai

2014-03-26

It may be hardly believable that inert C-H bonds on a polymeric material surface could be quickly and efficiently transformed into C-OH by a simple and mild way. Thanks to the approaches developed recently, it is now possible to transform surface H atoms of a polymeric substrate into monolayer OH groups by a simple/mild photochemical reaction. Herein the method and application of this small-molecular interfacial chemistry is highlighted. The existence of hydroxyl groups on material surfaces not only determines the physical and chemical properties of materials but also provides effective reaction sites for postsynthetic sequential modification to fulfill the requirements of various applications. However, organic synthetic materials based on petroleum, especially polyolefins comprise mainly C and H atoms and thus present serious surface problems due to low surface energy and inertness in reactivity. These limitations make it challenging to perform postsynthetic surface sequential chemical derivatization toward enhanced functionalities and properties and also cause serious interfacial problems when bonding or integrating polymer substrates with natural or inorganic materials. Polymer surface hydroxylation based on direct conversion of C-H bonds on polymer surfaces is thus of significant importance for academic and practical industrial applications. Although highly active research results have reported on small-molecular C-H bond activation in solution (thus homogeneous), most of them, featuring the use of a variety of transition metals as catalysts, present a slow reaction rate, a low atom economy and an obvious environmental pollution. In sharp contrast to these conventional C-H activation strategies, the present Spotlight describes a universal confined photocatalytic oxidation (CPO) system that is able to directly convert polymer surface C-H bonds to C-OSO3(-) and, subsequently, to C-OH through a simple hydrolysis. Generally speaking, these newly implanted hydroxyl groups preserve their own reactivity toward other complementary compounds, thus creating a novel base with distinct surface properties. Thanks to this functionalized platform, a wide range of organic, inorganic and metal materials have been attached to conventional organic polymer substrates through the rational engineering of surface molecular templates from small functional groups to macromolecules. It is expected that the proposed novel CPO method and its versatile usages in advanced material applications will offer new opportunities for a variety of scientific communities, especially for those working on surface/interface modulation.

Evaluation of oxidation behavior of γ-irradiated EPDM/PP compounds

NASA Astrophysics Data System (ADS)

Zaharescu, T.; Jipa, S.; Setnescu, R.; Setnescu, T.

2007-12-01

The oxidation effect of irradiation on ethylene-propylene diene terpolymer/polypropylene blends is presented. The polymer samples consisting of both materials under various ratios (20:80, 40:60, 60:40 and 80:20) were exposed to γ-irradiation ( 137Cs). The irradiation effects were assessed by two methods: oxygen uptake and IR spectroscopy (1720 cm -1 and 3350 cm -1, the characteristic bands for carbonyl and hydroxyl groups, respectively). The carbonyl and hydroxyl indexes were calculated for all formulations. From oxygen uptake investigation the kinetic parameters for thermal oxidation of irradiated samples were calculated. The contribution of each component to the progress of degradation is discussed.

Enumeration of sugars and sugar alcohols hydroxyl groups by aqueous-based acetylation and MALDI-TOF mass spectrometry

USDA-ARS?s Scientific Manuscript database

A method is described for enumerating hydroxyl groups on analytes in aqueous media is described, and applied to some common polyalcohols (erythritol, mannitol, and xylitol) and selected carbohydrates. The analytes were derivatized in water with vinyl acetate in presence of sodium phosphate buffer. ...

Structural evolution of fluorinated graphene upon molten-alkali treatment probed by X-ray absorption near-edge structure spectroscopy

NASA Astrophysics Data System (ADS)

Liang, Xianqing; Pan, Deyou; Lao, Ming; Liang, Shuiying; Huang, Dan; Zhou, Wenzheng; Guo, Jin

2017-05-01

The structural evolution of fluorinated graphene (FG) nanosheets upon molten-alkali treatment has been systematically investigated utilizing X-ray absorption near-edge structure (XANES) spectroscopy. It is found that the hydroxyl groups can progressively displace fluorine atoms to form covalent bonds to the graphene sheets under designed molten-alkali condition. The XANES spectra also reveal the formation of epoxide groups through intramolecular dehydration of neighbouring hydroxyl groups after substitution reaction. At high alkali-FG weight ratio, the restoration of the π-conjugated structure in graphene sheets can be observed due to the gradual decomposition of epoxide groups. Our experimental results indicate that the surface chemistry and electronic structure of hydroxyl-functionalized FG (HFG) can be readily tuned by varying the ratio of reactants.

Investigation of chitosan-phenolics systems as wood adhesives.

PubMed

Peshkova, Svetlana; Li, Kaichang

2003-04-24

Chitosan-phenolics systems were investigated as wood adhesives. Adhesion between two pieces of wood veneer developed only when all three components-chitosan, a phenolic compound, and laccase-were present. For the adhesive systems containing a phenolic compound with only one phenolic hydroxyl group, adhesive strengths were highly dependent upon the chemical structures of phenolic compounds used in the system and the relative oxidation rates of the phenolic compounds by laccase. The adhesive strengths were also directly related to the viscosity of the adhesive systems. However, for the adhesive systems containing a phenolic compound with two or three phenolic hydroxyl groups adjacent to each other, no correlations among adhesive strengths, relative oxidation rates of the phenolic compounds by laccase, and viscosities were observed. The adhesion mechanisms of these chitosan-phenolics systems were proposed to be similar to those of mussel adhesive proteins.

Suppression of LPS-induced inflammatory responses by the hydroxyl groups of dexamethasone

PubMed Central

Chuang, Ting-Yun; Cheng, An-Jie; Chen, I-Ting; Lan, Tien-Yun; Huang, I-Hsuan; Shiau, Chung-Wai; Hsu, Chia-Lin; Liu, Ya-Wen; Chang, Zee-Fen; Tseng, Ping-Hui; Kuo, Jean-Cheng

2017-01-01

The innate immune response is a central process that is activated during pathogenic infection in order to maintain physiological homeostasis. It is well known that dexamethasone (Dex), a synthetic glucocorticoid, is a potent immunosuppressant that inhibits the cytokine production induced by bacterial lipopolysaccharides (LPS). Nevertheless, the extent to which the functional groups of Dex control the excessive activation of inflammatory reactions remains unknown. Furthermore, importantly, the role of Dex in the innate immune response remains unclear. Here we explore the mechanism of LPS-induced TNF-α secretion and reveal p38 MAPK signaling as a target of Dex that is involved in control of tumor necrosis factor-α (TNF-α)-converting enzyme (TACE) activity; that later mediates the shedding of TNF-α that allows its secretion. We further demonstrate that the 11-hydroxyl and 21-hydroxyl groups of Dex are the main groups that are involved in reducing LPS-induced TNF-α secretion by activated macrophages. Blockage of the hydroxyl groups of Dex inhibits immunosuppressant effect of Dex during LPS-induced TNF-α secretion and mouse mortality. Our findings demonstrate Dex signaling is involved in the control of innate immunity. PMID:28537905

Relationship between in vivo chlorzoxazone hydroxylation, hepatic cytochrome P450 2E1 content and liver injury in obese non-alcoholic fatty liver disease patients.

PubMed

Orellana, Myriam; Rodrigo, Ramón; Varela, Nelson; Araya, Julia; Poniachik, Jaime; Csendes, Attila; Smok, Gladys; Videla, Luis A

2006-01-01

The aim of the present study was to test the hypothesis that induction of cytochrome P450 2E1 (CYP2E1) in the liver of patients with non-alcoholic fatty liver disease (NAFLD) is correlated both with the in vivo activity of the cytochrome and with the development of liver injury. For this purpose, the liver content of CYP2E1 was determined by Western blot and the CYP2E1 activity by the in vivo hydroxylation of chlorzoxazone (CLZ). The study groups were obese women with an average body mass index (BMI) of 40.3kg/m(2), who underwent therapeutic gastroplasty or gastrectomy with a gastro-jejunal anastomosis. Further, the hepatic histology was determined to establish the pathological score grouping the subjects into three categories: control, steatosis and steatohepatitis. The liver CYP2E1 content and the CLZ hydroxylation of obese patients with steatosis and, particularly, with steatohepatitis were significantly higher than controls and correlated positively with both the severity of the liver damage. These data provide evidence that CYP2E1 would be involved in the mechanism of liver injury found in obese NAFLD patients. Also, the correlation between liver CYP2E1 content and in vivo CLZ hydroxylation would validate the latter as a reliable indicator of liver injury in NAFLD, thus providing a simple and not invasive method to study these patients.

Synthesis, antimicrobial evaluation and molecular modeling of 5-hydroxyisoquinolinium salt series; the effect of the hydroxyl moiety.

PubMed

Soukup, Ondrej; Dolezal, Rafael; Malinak, David; Marek, Jan; Salajkova, Sarka; Pasdiorova, Marketa; Honegr, Jan; Korabecny, Jan; Nachtigal, Petr; Nachon, Florian; Jun, Daniel; Kuca, Kamil

2016-02-15

In the present paper, we describe the synthesis of a new group of 5-hydroxyisoquinolinium salts with different lengths of alkyl side-chain (C10-C18), and their chromatographic analysis and biological assay for in vitro activity against bacterial and fungal strains. We compare the lipophilicity and efficacy of hydroxylated isoquinolinium salts with the previously published (non-hydroxylated) isoquinolinium salts from the point of view of antibacterial and antifungal versatility and cytotoxic safety. Compound 11 (C18) had to be excluded from the testing due to its low solubility. Compounds 9 and 10 (C14, C16) showed only moderate efficacy against G+ bacteria, notably with excellent potency against Staphyloccocus aureus, but no effect against G- bacteria. In contrast, non-hydroxylated isoquinolinium salts showed excellent antimicrobial efficacy within the whole series, particularly 14 (C14) against G+ strains and 15 (C16) against fungi. The electronic properties and desolvation energies of 5-hydroxyisoquinolinium and isoquinolinium salts were studied by quantum-chemistry calculations employing B3LYP/6-311++G(d,p) method and an implicit water-solvent simulation model (SCRF). Despite the positive mesomeric effect of the hydroxyl moiety reducing the electron density of the quaternary nitrogen, it is probably the higher lipophilicity and lower desolvation energy of isoquinolinium salts, which is responsible for enhanced antimicrobial versatility and efficacy. Copyright © 2016 Elsevier Ltd. All rights reserved.

Implications of the fluorescence for the conformational analysis of polymeric profisetinidins and procyanidins

Treesearch

Carin A. Helfer; Joo-Sang Sun; Mark A. Matties; Wayne L. Mattice; Richard W. Hemingway; Jan P. Steynberg; Lisa A. Kelly

1995-01-01

The common monomeric units in the polymeric proeyanidins are catechin and epicatechin, which have a hydroxyl group at C(5). This hydroxyl group is absent in the profisetinidins. The fluorescence properties have been characterized for the profisetinidin monomer and dimers, and compared with previous results for the procyanidins. There is a measurable heterogeneity in...

Implications of the fluorescence for the conformational analysis of polymeric profisentinidins and procyanidins

Treesearch

Carin A. Heifer; Joo-Sang Sun; Mark A. Matties; Wayne L. Mattice; Richard W. Hemingway; Jan P. Steynberg; Lisa A. Kelly

1995-01-01

The common monomeric units in the polymeric procyanidins are catechin and epicatechin, which have a hydroxyl group at C(5). this hydroxyl group is absent in the profisetinidins. The fluorescence properties have been characterized for the profisentinidin monomer and dimers, and compared with previous results for the procyanidins. There is a measurable heterogeneity in...

Structural properties of TiO2 nanomaterials

NASA Astrophysics Data System (ADS)

Kusior, Anna; Banas, Joanna; Trenczek-Zajac, Anita; Zubrzycka, Paulina; Micek-Ilnicka, Anna; Radecka, Marta

2018-04-01

The surface of solids is characterized by active, energy-rich sites that determine physicochemical interaction with gaseous and liquid media and possible applications in photocatalysis. The behavior of materials in such processes is related to their form and amount of various species, especially water and forms of oxygen adsorbed on the surface. The preparation of materials with controlled morphology, which includes modifications of the size, geometry, and composition, is currently an important way of optimizing properties, as many of them depend on not only the size and phase composition, but also on shape. Hydroxylated centers on the surface, which can be treated as trapping sites, are particularly significant. Water adsorbed on the surface bridging hydroxyl groups can distinctly modulate the properties of the surface of titania. The saturation of the surface with hydroxyl groups may improve the photocatalytic properties. TiO2 nanomaterials were obtained via different methods. SEM and TEM analysis were performed to study the morphology. The analysis of XRD and Raman data revealed a phase composition of obtained materials. To examine the surface properties, FTIR absorption spectra of TiO2 nanomaterials were recorded. The photocatalytic activity of titanium dioxide nanoparticles was investigated through the decomposition of methylene blue. It was demonstrated that each surface modification affects the amount of adsorbed hydroxyl groups. The different contributions of the two species to the ν(H2O) FTIR bands for different nanostructures result from the preparation conditions. It was noted that pre-adsorbed water (the surface-bridging hydroxyl) might significantly modulate the surface properties of the material. The increase in hydroxyl group density on the titanium dioxide surface enhances the effectiveness of the photocatalytic processes. It was demonstrated that flower-like titania obtained via hydrothermal synthesis exhibits the weakest catalytic activity, in contrast to the typical spherical TiO2.

Oxime ether lipids containing hydroxylated head groups are more superior siRNA delivery agents than their nonhydroxylated counterparts.

PubMed

Gupta, Kshitij; Mattingly, Stephanie J; Knipp, Ralph J; Afonin, Kirill A; Viard, Mathias; Bergman, Joseph T; Stepler, Marissa; Nantz, Michael H; Puri, Anu; Shapiro, Bruce A

2015-01-01

To evaluate the structure-activity relationship of oxime ether lipids (OELs) containing modifications in the hydrophobic domains (chain length, degree of unsaturation) and hydrophilic head groups (polar domain hydroxyl groups) toward complex formation with siRNA molecules and siRNA delivery efficiency of resulting complexes to a human breast cancer cell line (MDA-MB-231). Ability of lipoplex formation between oxime ether lipids with nucleic acids were examined using biophysical techniques. The potential of OELs to deliver nucleic acids and silence green fluorescent protein (GFP) gene was analyzed using MDA-MB-231 and MDA-MB-231/GFP cells, respectively. Introduction of hydroxyl groups to the polar domain of the OELs and unsaturation into the hydrophobic domain favor higher transfection and gene silencing in a cell culture system.

Adsorption of Pb(II) ions onto biomass from Trifolium resupinatum: equilibrium and kinetic studies

NASA Astrophysics Data System (ADS)

Athar, Makshoof; Farooq, Umar; Aslam, Muhammad; Salman, M.

2013-09-01

The present study provides information about the binding of Pb(II) ions on an eco-friendly and easily available biodegradable biomass Trifolium resupinatum. The powdered biomass was characterized by FTIR, potentiometric titration and surface area analyses. The FTIR spectrum showed the presence of hydroxyl, carbonyl and amino functional groups and Pb(II) ions bound with the oxygen- and nitrogen-containing sites (hydroxyl and amino groups). The acidic groups were also confirmed by titrations. Effects of various environmental parameters (time, pH and concentration) have been studied. The biosorption process achieved equilibrium in a very short period of time (25 min). Non-linear approach for Langmuir and Freundlich models was used to study equilibrium process and root mean-square error was used as an indicator to decide the fitness of the mathematical model. The biosorption process was found to follow pseudo-second-order kinetics and was very fast. Thus, the biomass can be cost-effectively used for the binding of Pb(II) ions from aqueous solutions.

Improved Steroids Detection and Evidence for Their Regiospecific Decompositions Using Anion Attachment Mass Spectrometry.

PubMed

Dumont, Quentin; Bárcenas, Mariana; Dossmann, Héloïse; Bailloux, Isabelle; Buisson, Corinne; Mechin, Nathalie; Molina, Adeline; Lasne, Françoise; Rannulu, Nalaka S; Cole, Richard B

2016-04-05

Nonpolar anabolic steroids are doping agents that typically do not provide strong signals by electrospray ionization-mass spectrometry (ESI-MS) owing especially to the low polarity of the functional groups present. We have investigated the addition of anions, in ammonium salt form, to anabolic steroid samples as ionization enhancers and have confirmed that lower instrumental limits of detection (as low as 10 ng/mL for fluoxymesterone-M) are obtained by fluoride anion attachment mass spectrometry, as compared to ESI(+)/(-) or atmospheric pressure photoionization (APPI)(+). Moreover, collision-induced decomposition (CID) spectra of precursor fluoride adducts of the bifunctional steroid "reduced pregnenolone" (containing two hydroxyl groups) and its d4-analogue provide evidence of regiospecific decompositions after attachment of fluoride anion to a specific hydroxyl group of the steroid. This type of charting of specific CID reaction pathways can offer value to selected reaction monitoring experiments (SRM) as it may result in a gain in selectivity in detection as well as in improvements in quantification.

Regioselective Benzoylation of Diols and Carbohydrates by Catalytic Amounts of Organobase.

PubMed

Lu, Yuchao; Hou, Chenxi; Ren, Jingli; Xin, Xiaoting; Xu, Hengfu; Pei, Yuxin; Dong, Hai; Pei, Zhichao

2016-05-17

A novel metal-free organobase-catalyzed regioselective benzoylation of diols and carbohydrates has been developed. Treatment of diol and carbohydrate substrates with 1.1 equiv. of 1-benzoylimidazole and 0.2 equiv. of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) in MeCN under mild conditions resulted in highly regioselective benzoylation for the primary hydroxyl group. Importantly, compared to most commonly used protecting bulky groups for primary hydroxyl groups, the benzoyl protective group offers a new protection strategy.

Mechanisms of the Formation of Adenine, Guanine, and Their Analogues in UV-Irradiated Mixed NH3:H2O Molecular Ices Containing Purine

NASA Astrophysics Data System (ADS)

Bera, Partha P.; Stein, Tamar; Head-Gordon, Martin; Lee, Timothy J.

2017-08-01

We investigated the formation mechanisms of the nucleobases adenine and guanine and the nucleobase analogues hypoxanthine, xanthine, isoguanine, and 2,6-diaminopurine in a UV-irradiated mixed 10:1 H2O:NH3 ice seeded with precursor purine by using ab initio and density functional theory computations. Our quantum chemical investigations suggest that a multistep reaction mechanism involving purine cation, hydroxyl and amino radicals, together with water and ammonia, explains the experimentally obtained products in an independent study. The relative abundances of these products appear to largely follow from relative thermodynamic stabilities. The key role of the purine cation is likely to be the reason why purine is not functionalized in pure ammonia ice, where cations are promptly neutralized by free electrons from NH3 ionization. Amine group addition to purine is slightly favored over hydroxyl group attachment based on energetics, but hydroxyl is much more abundant due to higher abundance of H2O. The amino group is preferentially attached to the 6 position, giving 6-aminopurine, that is, adenine, while the hydroxyl group is preferentially attached to the 2 position, leading to 2-hydroxypurine. A second substitution by hydroxyl or amino group occurs at either the 6 or the 2 position depending on the first substitution. Given that H2O is far more abundant than NH3 in the experimentally studied ices (as well as based on interstellar abundances), xanthine and isoguanine are expected to be the most abundant bi-substituted photoproducts.

Influence of hydroxyl groups on the biological properties of cationic polymethacrylates as gene vectors.

PubMed

Ma, Ming; Li, Feng; Yuan, Zhe-fan; Zhuo, Ren-xi

2010-07-01

In this study poly(aminoethyl methacrylate) (PAEMA), poly(3-amino-2-hydroxypropyl methacrylate) (PAHPMA), poly(2-(2-aminoethylamino)ethyl methacrylate) (PAEAEMA) and poly(3-(2-aminoethylamino) 2-hydroxypropyl methacrylate) (PAEAHPMA) were synthesized using atom transfer radical polymerization to evaluate the effect of hydroxyl groups on the relative properties of cationic polymeric gene vectors. The results of heparin displacement assays showed that PAHPMA possessed a stronger binding capacity than PAEMA. PAHPMA/DNA complexes and PAEAHPMA/DNA complexes had lower zeta potentials than those of PAEMA and PAEAEMA. MTT assay results indicated that PAHPMA and PAEAHPMA exhibited obviously lower cytotoxicities than PAEMA and PAEAEMA. Subsequently, in vitro gene transfection studies in 293T cells without serum showed that PAHPMA exhibited a lower transfection efficiency than PAEMA and PAEAHPMA/DNA complexes possessed a similar transfection efficiency to PAEAEMA/DNA complexes. Moreover, PAHPMA and PAEAHPMA retained similar transfection efficiencies in DMEM with 10% serum, but PAEMA and PAEAEMA showed slightly lower transfection efficiencies than in the absence of serum. The reason for these phenomena might be attributed to the introduction of hydroxyl groups into PAHPMA and PAEAHPMA, i.e. the existence of hydroxyl groups might increase the binding capacity to DNA and at the same time decrease the surface charge of the polymer/DNA complexes due to the formation of hydrogen bonds between the polymers and DNA. Therefore, a lower zeta potential and stronger binding ability may result in a lower gene transfection efficiency. This effect of hydroxyl groups decreased with increasing amino group density on the polymer. Copyright 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Promotional effect of surface hydroxyls on electrochemical reduction of CO2 over SnOx/Sn electrode

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cui, Chaonan; Han, Jinyu; Zhu, Xinli

Tin oxide (SnOx) formation on tin-based electrode surfaces during CO2 electrochemical reduction can have a significant impact on the activity and selectivity of the reaction. In the present study, density functional theory (DFT) calculations have been performed to understand the role of SnOx in CO2 reduction using a SnO monolayer on the Sn(112) surface as a model for SnOx. Water molecules have been treated explicitly and considered actively participating in the reaction. The results showed that H2O dissociates on the perfect SnO monolayer into two hydroxyl groups symmetrically on the surface. CO2 energetically prefers to react with the hydroxyl, formingmore » a bicarbonate (HCO3(t)*) intermediate, which can then be reduced to either formate (HCOO*) by hydrogenating the carbon atom or carboxyl (COOH*) by protonating the oxygen atom. Both steps involve a simultaneous C-O bond breaking. Further reduction of HCOO* species leads to the formation of formic acid in the acidic solution at pH < 4, while the COOH* will decompose to CO and H2O via protonation. Whereas the oxygen vacancy (VO) in the monolayer maybe formed by the reduction of the monolayer, it can be recovered by H2O dissociation, resulting in two embedded hydroxyl groups. However, the hydroxylated surface with two symmetric hydroxyls is energetically more favorable for CO2 reduction than the hydroxylated VO surface with two embedded hydroxyls. The reduction potential for the former has a limiting-potential of -0.20 V (RHE), lower than that for the latter (-0.74 V (RHE)). Compared to the pure Sn electrode, the formation of SnOx monolayer on the electrode under the operating conditions promotes CO2 reduction more effectively by forming surface hydroxyls, thereby, providing a new channel via COOH* to the CO formation, although formic acid is still the major reduction product. The work was supported in part by National Natural Sciences Foundation of China (Grant #21373148 and #21206117). The High Performance Computing Center of Tianjin University is acknowledged for providing services to the computing cluster. CC acknowledges the support of 24 China Scholarship Council (CSC). QG acknowledges the support of NSF-CBET program (Award no. CBET-1438440). DM was supported by the US Department of Energy, Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences & Biosciences. The computations were performed in part using the Molecular Science Computing Facility in the William R. Wiley Environmental Molecular Sciences Laboratory (EMSL), which is a U.S. Department of Energy national scientific user facility located at Pacific Northwest National Laboratory (PNNL) in Richland, Washington.« less

The Effect of Surface Chemical Functionality Upon Ice Adhesion

NASA Technical Reports Server (NTRS)

Smith, Joseph G., Jr.; Wohl, Christopher J.; Doss, Jereme; Spence, Destiny; Kreeger, Richard E.; Palacios, Jose; Knuth, Taylor; Hadley, Kevin R.; McDougal, Nicholas D.

2015-01-01

In nature, anti-freeze proteins present in fish utilize specific organic functionalities to disrupt ice crystal formation and propagation. Based on these structures, surfaces with controlled chemical functionality and chain length were evaluated both experimentally and computationally to assess the effect of both parameters in mitigating ice formation. Linear aliphatic dimethylethoxysilanes terminated with methyl or hydroxyl groups were prepared, characterized, and used to coat aluminum. The effect upon icing using a microdroplet freezing apparatus and the Adverse Environment Rotor Test Stand found hydroxyl-terminated materials exhibited a greater propensity for ice formation and adhesion. Molecular dynamics simulations of a silica substrate bearing functionalized species of similar composition were brought into contact with a pre-equilibrated ice crystal. Several parameters including chain mobility were monitored to ascertain the size of a quasi-liquid layer. The studies suggested that chain mobility affected the interface between ice and the surface more than terminal group chemical composition.

VARIABLE CHARGE SOILS: MINERALOGY AND CHEMISTRY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Van Ranst, Eric; Qafoku, Nikolla; Noble, Andrew

2016-09-19

Soils rich in particles with amphoteric surface properties in the Oxisols, Ultisols, Alfisols, Spodosols and Andisols orders (1) are considered to be variable charge soils (2) (Table 1). The term “variable charge” is used to describe organic and inorganic soil constituents with reactive surface groups whose charge varies with pH and ionic concentration and composition of the soil solution. Such groups are the surface carboxyl, phenolic and amino functional groups of organic materials in soils, and surface hydroxyl groups of Fe and Al oxides, allophane and imogolite. The hydroxyl surface groups are also present on edges of some phyllosilicate mineralsmore » such as kaolinite, mica, and hydroxyl-interlayered vermiculite. The variable charge is developed on the surface groups as a result of adsorption or desorption of ions that are constituents of the solid phase, i.e., H+, and the adsorption or desorption of solid-unlike ions that are not constituents of the solid phase. Highly weathered soils and subsoils (e.g., Oxisols and some Ultisols, Alfisols and Andisols) may undergo isoelectric weathering and reach a “zero net charge” stage during their development. They usually have a slightly acidic to acidic soil solution pH, which is close to either the point of zero net charge (PZNC) (3) or the point of zero salt effect (PZSE) (3). They are characterized by high abundances of minerals with a point of zero net proton charge (PZNPC) (3) at neutral and slightly basic pHs; the most important being Fe and Al oxides and allophane. Under acidic conditions, the surfaces of these minerals are net positively charged. In contrast, the surfaces of permanent charge phyllosilicates are negatively charged regardless of ambient conditions. Variable charge soils therefore, are heterogeneous charge systems.« less

Switchable nanoassembly from an azobenzene-containing dye.

PubMed

Wang, Jing; Ha, Chang-Sik

2011-07-01

In this work, we investigated optical properties and the morphology of the amphiphilic azobenzene dye 1 containing hydroxyl azobenzene and C10 alkyl chains. Since the hydroxyl group on 1 has a pKa of 9.38, the deprotonation of the hydroxyl group occurs at pH > pKa (9.38) and thus the 1 nanoparticles are negatively charged. The deprotonated hydroxyl group is hydrophilic relative to the long alkyl chain that is hydrophobic, while the hydrophobic and hydrophilic parts are connected by covalent bonds. When such an azobenzene molecule 1 with both hydrophobic and hydrophilic groups exists in solution, "self-aggregation" may occur due to the hydrophobic interaction between the long alkyl chains. The scattered morphology at pH 7.0 (neutral state) and the aggregated morphology at pH 10.5 (anionic state) of 1 were demostrated by transmission electron microscopy (TEM) and atomic force microscopy (AFM) images. Formation of supramolecular aggregation-induced vesicular-like structures are highly interesting due to the ability to respond to external triggers, pH. The pH value can be reversed by adding acid or base to the system, that is, switching the aggregation "on" and "off" can be repeated.

Importance of specific purine amino and hydroxyl groups for efficient cleavage by a hammerhead ribozyme.

PubMed Central

Fu, D J; McLaughlin, L W

1992-01-01

Eight modified ribozymes of 19 residues have been prepared with individual purine amino or hydroxyl groups excised. The modified ribozymes were chemically synthesized with the substitution of a single 2'-deoxyadenosine, 2'-deoxyguanosine, inosine, or purine riboside for residues G10, A11, G13, or A14. Five of the modified ribozymes cleaved the 24-mer substrate with little change in rate as monitored by simple first-order kinetics. However, deletion of the 2-amino group at G10 (replacement with inosine) or deletion of either of the 2'-hydroxyls at G10 or G13 (replacement with 2'-deoxyguanosine) resulted in ribozymes with a drastic decrease in cleavage efficiency. Increasing the concentration of the Mg2+ cofactor from 10 mM to 50 mM significantly enhanced cleavage efficiency by these three derivatives. Steady-state kinetic assays for these three ribozymes indicated that the modifications result in both an increase in Km and a decrease in kcat. These results suggest that the exocyclic amino group at-G10 and the hydroxyls at G10 and G13 are important both for ribozyme-substrate binding and for the Mg(2+)-catalyzed cleavage reaction. PMID:1570323

Ordered hydroxyls on Ca 3Ru 2O 7(001)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Halwidl, Daniel; Mayr-Schmölzer, Wernfried; Fobes, David

As complex ternary perovskite-type oxides are increasingly used in solid oxide fuel cells, electrolysis and catalysis, it is necessary to obtain a better understanding of their surface chemical properties. Here we report a pronounced ordering of hydroxyls on the cleaved (001) surface of the Ruddlesden-Popper perovskite Ca 3Ru 2O 7 upon water adsorption at 105 K and subsequent annealing to room temperature. Density functional theory calculations predict the dissociative adsorption of a single water molecule (E ads = 1.64 eV), forming an (OH) ads group adsorbed in a Ca-Ca bridge site, with an H transferred to a neighboring surface oxygenmore » atom, O surf. Scanning tunneling microscopy images show a pronounced ordering of the hydroxyls with (2 × 1), c(2 × 6), (1 × 3), and (1 × 1) periodicity. The present work demonstrates the importance of octahedral rotation and tilt in perovskites, for influencing surface reactivity, which here induces the ordering of the observed OH overlayers.« less

Ordered hydroxyls on Ca 3Ru 2O 7(001)

DOE PAGES

Halwidl, Daniel; Mayr-Schmölzer, Wernfried; Fobes, David; ...

2017-06-20

As complex ternary perovskite-type oxides are increasingly used in solid oxide fuel cells, electrolysis and catalysis, it is necessary to obtain a better understanding of their surface chemical properties. Here we report a pronounced ordering of hydroxyls on the cleaved (001) surface of the Ruddlesden-Popper perovskite Ca 3Ru 2O 7 upon water adsorption at 105 K and subsequent annealing to room temperature. Density functional theory calculations predict the dissociative adsorption of a single water molecule (E ads = 1.64 eV), forming an (OH) ads group adsorbed in a Ca-Ca bridge site, with an H transferred to a neighboring surface oxygenmore » atom, O surf. Scanning tunneling microscopy images show a pronounced ordering of the hydroxyls with (2 × 1), c(2 × 6), (1 × 3), and (1 × 1) periodicity. The present work demonstrates the importance of octahedral rotation and tilt in perovskites, for influencing surface reactivity, which here induces the ordering of the observed OH overlayers.« less

Curable liquid hydrocarbon prepolymers containing hydroxyl groups and process for producing same

NASA Technical Reports Server (NTRS)

Rhein, R. A.; Ingham, J. D. (Inventor)

1978-01-01

Production of hydroxyl containing curable liquid hydrocarbon prepolymers by ozonizing a high molecular weight saturated hydrocarbon polymer such as polyisobutylene or ethylene propylene rubber is discussed. The ozonized material is reduced using reducing agents, preferably diisobutyl aluminum hydride, to form the hydroxyl containing liquid prepolymers having a substantially lower molecular weight than the parent polymer. The resulting curable liquid hydroxyl containing prepolymers can be poured into a mold and readily cured, with reactants such as toluene diisocyanate, to produce highly stable elastomers having a variety of uses such as binders for solid propellants.

Hydroxyl group as IR probe to detect the structure of ionic liquid-acetonitrile mixtures

NASA Astrophysics Data System (ADS)

Xu, Jing; Deng, Geng; Zhou, Yu; Ashraf, Hamad; Yu, Zhi-Wu

2018-06-01

Task-specific ionic liquids (ILs) are those with functional groups introduced in the cations or anions of ILs to bring about specific properties for various tasks. In this work, the hydrogen bonding interactions between a hydroxyl functionalized IL 1-(2-hydroxylethyl)-3-methylimidazolium tetrafluoroborate ([C2OHMIM][BF4]) and acetonitrile were investigated in detail by infrared spectroscopy, excess spectroscopy, two-dimensional correlation spectroscopy, combined with hydrogen nuclear magnetic resonance and density functional theory calculations (DFT). The hydroxyl group rather than C2sbnd H is found to be the main interaction site in the cation. And the ν(Osbnd H) is more sensitive than v(C-Hs) to the environment, which has been taken as an intrinsic probe to reflect the structural change of IL. Examining the region of ν(Osbnd H), by combining excess spectroscopy and DFT calculation, a number of species were identified in the mixtures. Other than the hydrogen bond between a cation and an anion, the hydroxyl group allows the formation of a hydrogen bond between two like-charged cations. The Osbnd H⋯O hydrogen bonding interactions in the hydroxyl-mediated cation-cation complexes are cooperative, while Osbnd H⋯F and C2sbnd H⋯F hydrogen bonding interactions in cation-anion complexes are anti-cooperative. These in-depth studies on the properties of the ionic liquid-acetonitrile mixtures may shed light on exploring their applications as mixed solvents and understanding the nature of doubly ionic hydrogen bonds.

In vitro metabolism studies of desoxy-methyltestosterone (DMT) and its five analogues, and in vivo metabolism of desoxy-vinyltestosterone (DVT) in horses.

PubMed

Kwok, Wai Him; Kwok, Karen Y; Leung, David K K; Leung, Gary N W; Wong, Colton H F; Wong, Jenny K Y; Wan, Terence S M

2015-08-01

The positive findings of norbolethone in 2002 and tetrahydrogestrinone in 2003 in human athlete samples confirmed that designer steroids were indeed being abused in human sports. In 2005, an addition to the family of designer steroids called 'Madol' [also known as desoxy-methyltestosterone (DMT)] was seized by government officials at the US-Canadian border. Two years later, a positive finding of DMT was reported in a mixed martial arts athlete's sample. It is not uncommon that doping agents used in human sports would likewise be abused in equine sports. Designer steroids would, therefore, pose a similar threat to the horseracing and equestrian communities. This paper describes the in vitro metabolism studies of DMT and five of its structural analogues with different substituents at the 17α position (RH, ethyl, vinyl, ethynyl and 2 H 3 -methyl). In addition, the in vivo metabolism of desoxy-vinyltestosterone (DVT) in horses will be presented. The in vitro studies revealed that the metabolic pathways of DMT and its analogues occurred predominantly in the A-ring by way of a combination of enone formation, hydroxylation and reduction. Additional biotransformation involving hydroxylation of the 17α-alkyl group was also observed for DMT and some of its analogues. The oral administration experiment revealed that DVT was extensively metabolised and the parent drug was not detected in urine. Two in vivo metabolites, derived respectively from (1) hydroxylation of the A-ring and (2) di-hydroxylation together with A-ring double-bond reduction, could be detected in urine up to a maximum of 46 h after administration. Another in vivo metabolite, derived from hydroxylation of the A-ring with additional double-bond reduction and di-hydroxylation of the 17α-vinyl group, could be detected in urine up to a maximum of 70 h post-administration. All in vivo metabolites were excreted mainly as glucuronides and were also detected in the in vitro studies. Copyright © 2015 John Wiley & Sons, Ltd. Copyright © 2015 John Wiley & Sons, Ltd.

[Simple method for precognition of drug interaction between oral iron and phenolic hydroxyl group-containing drugs].

PubMed

Sunagane, Nobuyoshi; Yoshinobu, Etsuko; Murayama, Nobuko; Terawaki, Yasufumi; Kamimura, Naoki; Uruno, Tsutomu

2005-02-01

In the present study, we devised a simple method for detecting the drug interaction between oral iron preparations and phenolic hydroxyl group-containing drugs, using the coloring reaction as indicator, due to the formation of complexes or chelates. In the method, oral iron preparations and test drugs in amounts as much as single dose for adults were added to 10 ml of purified water to make sample suspensions for testing. Thirty minutes after mixing an oral iron suspension and a test drug suspension, the change of color in the mixture was observed macroscopically and graded as 0 to 3, with a marked color change judged as grade 3 and no color change as grade 0. Screening of 14 test drugs commonly used orally was carried out. When using sodium ferrous citrate preparations as oral iron, 5 were classified as grade 3, 2 as grade 2, 4 as grade 1, and 3 as grade 0, respectively. To verify usefulness of the method, the interactions suggested by screening were pharmacokinetically assessed by measuring serum concentrations of the drug in mice. When a levodopa or droxidopa preparation, judged as grade 3 in screening, was concomitantly administered with an iron preparation, a significant reduction in bioavailability of the test drug was observed, indicating possible drug interaction between the test drug and oral iron. Combined administration of an acetaminophen preparation, judged as grade 1, and oral iron preparation showed no influence on the bioavailability of the test drug, implying no detectable interactions between them. In conclusion, the simple method devised in the present study is useful for precognition of drug interactions between oral iron preparations and phenolic hydroxyl group-containing drugs, and the drugs with a higher grade in screening may induce drug interactions with oral iron.

Oxime ether lipids containing hydroxylated head groups are more superior siRNA delivery agents than their nonhydroxylated counterparts

PubMed Central

Gupta, Kshitij; Mattingly, Stephanie J; Knipp, Ralph J; Afonin, Kirill A; Viard, Mathias; Bergman, Joseph T; Stepler, Marissa; Nantz, Michael H; Puri, Anu; Shapiro, Bruce A

2015-01-01

Aim: To evaluate the structure–activity relationship of oxime ether lipids (OELs) containing modifications in the hydrophobic domains (chain length, degree of unsaturation) and hydrophilic head groups (polar domain hydroxyl groups) toward complex formation with siRNA molecules and siRNA delivery efficiency of resulting complexes to a human breast cancer cell line (MDA-MB-231). Materials & methods: Ability of lipoplex formation between oxime ether lipids with nucleic acids were examined using biophysical techniques. The potential of OELs to deliver nucleic acids and silence green fluorescent protein (GFP) gene was analyzed using MDA-MB-231 and MDA-MB-231/GFP cells, respectively. Results & conclusion: Introduction of hydroxyl groups to the polar domain of the OELs and unsaturation into the hydrophobic domain favor higher transfection and gene silencing in a cell culture system. PMID:26107486

Hypotheses on the evolution of hyaluronan: A highly ironic acid

PubMed Central

Csoka, Antonei B; Stern, Robert

2013-01-01

Hyaluronan is a high-molecular-weight glycosaminoglycan (GAG) prominent in the extracellular matrix. Emerging relatively late in evolution, it may have evolved to evade immune recognition. Chondroitin is a more ancient GAG and a possible hyaluronan precursor. Epimerization of a 4-hydroxyl in N-acetylgalactosamine in chondroitin to N-acetylglucosamine of hyaluronan is the only structural difference other than chain length between these two polymers. The axial 4-hydroxyl group extends out perpendicular from the equatorial plane of N-acetylgalactosamine in chondroitin. We suspect that this hydroxyl is a prime target for immune recognition. Conversion of a thumbs-up hydroxyl group into a thumbs-down position in the plane of the sugar endows hyaluronan with the ability to avoid immune recognition. Chitin is another potential precursor to hyaluronan. But regardless whether of chondroitin or of chitin origin, an ancient chondroitinase enzyme sequence seems to have been commandeered to catalyze the cleavage of the new hyaluronan substrate. The evolution of six hyaluronidase-like sequences in the human genome from a single chondroitinase as found in Caenorhabditis elegans can now be traced. Confirming our previous predictions, two duplication events occurred, with three hyaluronidase-like sequences occurring in the genome of Ciona intestinalis (sea squirt), the earliest known chordate. This was probably followed by en masse duplication, with six such genes present in the genome of zebra fish onwards. These events occurred, however, much earlier than predicted. It is also apparent on an evolutionary time scale that in several species, this gene family is continuing to evolve. PMID:23315448

Effect of fullerenol surface chemistry on nanoparticle binding-induced protein misfolding

NASA Astrophysics Data System (ADS)

Radic, Slaven; Nedumpully-Govindan, Praveen; Chen, Ran; Salonen, Emppu; Brown, Jared M.; Ke, Pu Chun; Ding, Feng

2014-06-01

Fullerene and its derivatives with different surface chemistry have great potential in biomedical applications. Accordingly, it is important to delineate the impact of these carbon-based nanoparticles on protein structure, dynamics, and subsequently function. Here, we focused on the effect of hydroxylation -- a common strategy for solubilizing and functionalizing fullerene -- on protein-nanoparticle interactions using a model protein, ubiquitin. We applied a set of complementary computational modeling methods, including docking and molecular dynamics simulations with both explicit and implicit solvent, to illustrate the impact of hydroxylated fullerenes on the structure and dynamics of ubiquitin. We found that all derivatives bound to the model protein. Specifically, the more hydrophilic nanoparticles with a higher number of hydroxyl groups bound to the surface of the protein via hydrogen bonds, which stabilized the protein without inducing large conformational changes in the protein structure. In contrast, fullerene derivatives with a smaller number of hydroxyl groups buried their hydrophobic surface inside the protein, thereby causing protein denaturation. Overall, our results revealed a distinct role of surface chemistry on nanoparticle-protein binding and binding-induced protein misfolding.Fullerene and its derivatives with different surface chemistry have great potential in biomedical applications. Accordingly, it is important to delineate the impact of these carbon-based nanoparticles on protein structure, dynamics, and subsequently function. Here, we focused on the effect of hydroxylation -- a common strategy for solubilizing and functionalizing fullerene -- on protein-nanoparticle interactions using a model protein, ubiquitin. We applied a set of complementary computational modeling methods, including docking and molecular dynamics simulations with both explicit and implicit solvent, to illustrate the impact of hydroxylated fullerenes on the structure and dynamics of ubiquitin. We found that all derivatives bound to the model protein. Specifically, the more hydrophilic nanoparticles with a higher number of hydroxyl groups bound to the surface of the protein via hydrogen bonds, which stabilized the protein without inducing large conformational changes in the protein structure. In contrast, fullerene derivatives with a smaller number of hydroxyl groups buried their hydrophobic surface inside the protein, thereby causing protein denaturation. Overall, our results revealed a distinct role of surface chemistry on nanoparticle-protein binding and binding-induced protein misfolding. Electronic supplementary information (ESI) is available: Fluorescence spectra, ITC, CD spectra and other data as described in the text. See DOI: 10.1039/c4nr01544d

Resonance Enhanced Multi-Photon Ionization and Uv-Uv Hole-Burning Spectroscopic Studies of Jet-Cooled Acetanilide Derivatives

NASA Astrophysics Data System (ADS)

Moon, Ceol Joo; Min, Ahreum; Ahn, Ahreum; Lee, Seung Jun; Choi, Myong Yong; Kim, Seong Keun

2013-06-01

Conformational investigations and photochemistry of jet-cooled methacetine (MA) and phenacetine (PA) using one color resonant two-photon ionization (REMPI), UV-UV hole-burning and IR-dip spectroscopy are presented. MA and PA are derivatives of acetanilide, substituted by methoxyl, ethoxyl group in the para position of acetanilide, respectively. Moreover, we have investigated conformational information of the acetanilide derivatives (AAP, MA and PA)-water. In this work, we will present and discuss the solvent effects of the hydroxyl group of acetanilide derivatives in the excited state.

Exploring the reaction channels between arsine and the hydroxyl radical

NASA Astrophysics Data System (ADS)

Viana, Rommel B.

2017-10-01

The aim of this study was to present the reaction mechanism channels between arsine (AsH3) and hydroxyl (OH) which was evaluated at CCSD(T)/CBS//CCSD/cc-pVTZ level. One potential channel is the hydrogen abstraction pathway (R1), leading to AsH2 and H2O products, which occurs due to the formation of an entrance complex (AsH3OH) followed by a 1,2-hydrogen shift pathway (involving the proton transfer from the arsine group to hydroxyls, with one leading to the products). Additional channels are accessed via H-elimination pathways of the entrance complexes, forming arsinous acid (AsH2OH; R2) and arsine oxide (AsH3O; R3). In this respect, R2 is the only exoergic route of the three exit channels, representing the major branching ratio at 200-1000 K and, after 2000 K, R1 increases gradually becoming the major route of this reaction. In contrast, even at 4000 K, R3 is a highly unfeasible pathway. Therefore, the information predicted here provides new insights into the neutral-neutral chemical reaction dynamics regarding the Group V hydrides. On the other side, the R2 pathway may have some potential to solve the arsine oxidation puzzle as a possible primary pathway to the arsenic-oxygen species formation.

Diffusion of hydroxyl ions from calcium hydroxide and Aloe vera pastes.

PubMed

Batista, Victor Eduardo de Souza; Olian, Douglas Dáquila; Mori, Graziela Garrido

2014-01-01

This study evaluated the diffusion through the dentinal tubules of hydroxyl ions from different calcium hydroxide (CH) pastes containing Aloe vera. Sixty single-rooted bovine teeth were used. The tooth crowns were removed, the root canals were instrumented and the specimens were assigned to 4 groups (n=15) according to the intracanal medication: Group CH/S - CH powder and saline paste; Group CH/P - CH powder and propylene glycol paste; Group CH/A - calcium hydroxide powder and Aloe vera gel paste; Group CH/A/P - CH powder, Aloe vera powder and propylene glycol paste. After placement of the root canal dressings, the teeth were sealed coronally and apically with a two-step epoxy adhesive. The teeth were placed in identified flasks containing deionized water and stored in an oven with 100% humidity at 37 °C. After 3 h, 24 h, 72 h, 7 days, 15 days and 30 days, the deionized water in the flasks was collected and its pH was measured by a pH meter. The obtained data were subjected to statistical analysis at a significance level of 5%. The results demonstrated that all pastes provided diffusion of hydroxyl ions through the dentinal tubules. The combination of Aloe vera and CH (group CH/A) provided a constant release of calcium ions. Group CH/A/P showed the highest pH at 24 and 72 h. In conclusion, the experimental pastes containing Aloe vera were able to enable the diffusion of hydroxyl ions through the dentinal tubules.

Identification of the related substances of tilmicosin by liquid chromatography/ion trap mass spectrometry.

PubMed

Stoev, Georgi; Nazarov, Valeri

2008-06-01

Structures of seven impurities of the veterinary drug tilmicosin have been elucidated by multiple fragmentation with ion trap tandem mass spectrometry. All related compounds possess the main lactone ring of tilmicosin. The differences in their structures are due to the hydroxyl, mycaminose, 3,5-dimethylpiperidine and mycinose groups connected to C(3), C(5), C(6), C(14) of the lactone ring, respectively. The following compounds of the impurity profile of tilmicosin were identified: B - tilmicosin with a hydroxyl group at C(3); C - tilmicosin without a methyl group at the N-atom connected to C(3) of the mycaminose ring; D - tilmicosin with a hydroxyl group at C(6) of the mycaminose ring; E - tilmicosin with a methoxy group at C(3), F - desmicosin; G - 20-dihydrodesmicosin; and H - tilmicosin without a mycaminose ring. Isomers of the compounds B, C, D, E and H were identified by their mass chromatograms and retention times. The concentrations of the impurities varied in the range of 0.1% to 2.9%.

Spectroscopic and Photochemical Properties of Water-Soluble Fullerenol

EPA Science Inventory

Fullerenol, a hydroxylated form of C60-fullerene, is of potential environmental and biological significance due to its buckyball structure, hydroxyl groups and high water solubility. Although fullerenol is known to be an efficient triplet photosensitizer, little is known about it...

Galloylglucoses of low molecular weight as mordant in electron microscopy. II. The moiety and functional groups possibly involved in the mordanting effect

PubMed Central

1976-01-01

Synthetic pentamonogalloylglucose applied to fixed tissues acts as a mordant, inducing high and diversified contrast similar to that obtained with natural gallotannins of low molecular weight (LMGG). By the separate use of each of the two moieties of the galloylglucose molecule, it was found that gallic acid is the mordanting agent. Glucose may contribute, however, to the effect by increasing the solubility and cross-linking potential of the compound, since the mordanting induced by gallic acid alone is weaker than that produced by its hexose esters. As suggested by results obtained with various phenolics and benzoic acid derivatives, the functional groups required for the mordanting effect of such agents are the carboxyl group, and at least one hydroxyl group concomitantly present on the benzene ring. In the case of galloylglucoses, it is assumed that the effect is due to hydrolysis products (gallic, digallic, or trigallic acids) or to the multiple hydroxyl groups of the intact molecule. Esters of gallic acid (propyl- and methylgallate), as well as pyrogallol, produce a "reversed staining" of all membranes, except for those of communicating (gap) junctions. PMID:783173

Growth of large zeolite crystals in space

NASA Technical Reports Server (NTRS)

Sacco, A., Jr.; Dixon, A.; Thompson, R.; Scott, G.; Ditr, J.

1988-01-01

Synthesis studies performed using close analogs of triethanolamine (TEA) have shown that all three hydroxyl groups and the amine group in this molecule are necessary to provide nucleation suppression. Studies using C-13 nuclear magnetic resonance (NMR) revealed that the hydroxyl ions and the amine group are involved in the formation of an aluminum complex. It was also shown that silicate species fo not interact this way with TEA in an alkaline solution. These results suggest that successful aluminum complexation leads to nucleation in zeolite-A crystallization.

Structure, electronic properties, and aggregation behavior of hydroxylated carbon nanotubes

DOE Office of Scientific and Technical Information (OSTI.GOV)

López-Oyama, A. B.; Silva-Molina, R. A.; Ruíz-García, J.

2014-11-07

We present a combined experimental and theoretical study to analyze the structure, electronic properties, and aggregation behavior of hydroxylated multiwalled carbon nanotubes (OH–MWCNT). Our MWCNTs have average diameters of ∼2 nm, lengths of approximately 100–300 nm, and a hydroxyl surface coverage θ∼0.1. When deposited on the air/water interface the OH–MWCNTs are partially soluble and the floating units interact and link with each other forming extended foam-like carbon networks. Surface pressure-area isotherms of the nanotube films are performed using the Langmuir balance method at different equilibration times. The films are transferred into a mica substrate and atomic force microscopy images showmore » that the foam like structure is preserved and reveals fine details of their microstructure. Density functional theory calculations performed on model hydroxylated carbon nanotubes show that low energy atomic configurations are found when the OH groups form molecular islands on the nanotube's surface. This patchy behavior for the OH species is expected to produce nanotubes having reduced wettabilities, in line with experimental observations. OH doping yields nanotubes having small HOMO–LUMO energy gaps and generates a nanotube → OH direction for the charge transfer leading to the existence of more hole carriers in the structures. Our synthesized OH–MWCNTs might have promising applications.« less

Structure, electronic properties, and aggregation behavior of hydroxylated carbon nanotubes.

PubMed

López-Oyama, A B; Silva-Molina, R A; Ruíz-García, J; Gámez-Corrales, R; Guirado-López, R A

2014-11-07

We present a combined experimental and theoretical study to analyze the structure, electronic properties, and aggregation behavior of hydroxylated multiwalled carbon nanotubes (OH-MWCNT). Our MWCNTs have average diameters of ~2 nm, lengths of approximately 100-300 nm, and a hydroxyl surface coverage θ~0.1. When deposited on the air/water interface the OH-MWCNTs are partially soluble and the floating units interact and link with each other forming extended foam-like carbon networks. Surface pressure-area isotherms of the nanotube films are performed using the Langmuir balance method at different equilibration times. The films are transferred into a mica substrate and atomic force microscopy images show that the foam like structure is preserved and reveals fine details of their microstructure. Density functional theory calculations performed on model hydroxylated carbon nanotubes show that low energy atomic configurations are found when the OH groups form molecular islands on the nanotube's surface. This patchy behavior for the OH species is expected to produce nanotubes having reduced wettabilities, in line with experimental observations. OH doping yields nanotubes having small HOMO-LUMO energy gaps and generates a nanotube → OH direction for the charge transfer leading to the existence of more hole carriers in the structures. Our synthesized OH-MWCNTs might have promising applications.

Fluorine follows water: Effect on electrical conductivity of silicate minerals by experimental constraints from phlogopite

NASA Astrophysics Data System (ADS)

Li, Yan; Jiang, Haotian; Yang, Xiaozhi

2017-11-01

Fluorine and hydroxyl groups are minor constituents of silicate minerals, and share a lot of similarities concerning their physical and chemical properties. Hydroxyl groups significantly enhance the electrical conductivity of many silicate minerals, and it is expected that fluorine would have a comparable effect. This, however, has never been documented quantitatively. Here we present experimental approaches on this issue, by investigating the electrical conductivity of phlogopite with a wide range of fluorine content (but with broadly similar contents for other major elements). Electrical conductivities of gem-quality single crystal phlogopites, with samples prepared along the same orientation (normal to the (0 0 1) plane), were determined at 1 GPa and 200-650 °C using an end-loaded piston cylinder apparatus and a Solartron-1260 Impedance/Gain Phase Analyzer over the frequency range of 106 to 0.1 Hz. The complex spectra usually show an arc in the high frequency range and a short tail in the low frequency range, which are caused by lattice conduction and electrode effects, respectively. The electrical conductivity increases with increasing fluorine content, and the main charge carriers are fluorine. The activation enthalpies are ∼180 to 200 kJ/mol, nearly independent of fluorine content. The conductivity is linearly proportional to the content of fluorine, with an exponent factor of ∼1. The results demonstrate that conduction by fluorine leads to very high electrical conductivity at high temperatures. The influence of fluorine on electrical conductivity may be compared to that of hydrogen in nominally anhydrous minerals. This, along with the close association of fluorine and hydroxyl groups in silicate minerals and their similar crystal-chemical behaviors, suggests a more general role of fluorine in enhancing the electrical conductivity of many silicate minerals. Fluorine-rich assemblages, e.g., phlogopite and amphibole, could be locally enriched in the upper mantle, and if they form connected networks as observed for some natural samples, regionally high electrical conductivities could be produced. It has been recently proposed that the transition zone is probably a major reservoir for fluorine in the mantle, due to the significant dissolution of fluorine in wadsleyite and ringwoodite and the coupled incorporation with hydroxyl groups. As such, geophysically-resolved high electrical conductivities in the transition zone may be accounted for by fluorine in the dominant minerals, rather than by hydroxyl groups. The results of this work would stimulate a wide scope of future studies on the deep fluorine cycle, the deep water cycle and the geodynamical properties of the mantle.

Thermodynamic and redox properties of graphene oxides for lithium-ion battery applications: a first principles density functional theory modeling approach.

PubMed

Kim, Sunghee; Kim, Ki Chul; Lee, Seung Woo; Jang, Seung Soon

2016-07-27

Understanding the thermodynamic stability and redox properties of oxygen functional groups on graphene is critical to systematically design stable graphene-based positive electrode materials with high potential for lithium-ion battery applications. In this work, we study the thermodynamic and redox properties of graphene functionalized with carbonyl and hydroxyl groups, and the evolution of these properties with the number, types and distribution of functional groups by employing the density functional theory method. It is found that the redox potential of the functionalized graphene is sensitive to the types, number, and distribution of oxygen functional groups. First, the carbonyl group induces higher redox potential than the hydroxyl group. Second, more carbonyl groups would result in higher redox potential. Lastly, the locally concentrated distribution of the carbonyl group is more beneficial to have higher redox potential compared to the uniformly dispersed distribution. In contrast, the distribution of the hydroxyl group does not affect the redox potential significantly. Thermodynamic investigation demonstrates that the incorporation of carbonyl groups at the edge of graphene is a promising strategy for designing thermodynamically stable positive electrode materials with high redox potentials.

DNA Binding Hydroxyl Radical Probes.

PubMed

Tang, Vicky J; Konigsfeld, Katie M; Aguilera, Joe A; Milligan, Jamie R

2012-01-01

The hydroxyl radical is the primary mediator of DNA damage by the indirect effect of ionizing radiation. It is a powerful oxidizing agent produced by the radiolysis of water and is responsible for a significant fraction of the DNA damage associated with ionizing radiation. There is therefore an interest in the development of sensitive assays for its detection. The hydroxylation of aromatic groups to produce fluorescent products has been used for this purpose. We have examined four different chromophores which produce fluorescent products when hydroxylated. Of these, the coumarin system suffers from the fewest disadvantages. We have therefore examined its behavior when linked to a cationic peptide ligand designed to bind strongly to DNA.

Chemical Isotope Labeling LC-MS for High Coverage and Quantitative Profiling of the Hydroxyl Submetabolome in Metabolomics.

PubMed

Zhao, Shuang; Luo, Xian; Li, Liang

2016-11-01

A key step in metabolomics is to perform accurate relative quantification of the metabolomes in comparative samples with high coverage. Hydroxyl-containing metabolites are an important class of the metabolome with diverse structures and physical/chemical properties; however, many of them are difficult to detect with high sensitivity. We present a high-performance chemical isotope labeling liquid chromatography mass spectrometry (LC-MS) technique for in-depth profiling of the hydroxyl submetabolome, which involves the use of acidic liquid-liquid extraction to enrich hydroxyl metabolites into ethyl acetate from an aqueous sample. After drying and then redissolving in acetonitrile, the metabolite extract is labeled using a base-activated 12 C- or 13 C-dansylation reaction. A fast step-gradient LC-UV method is used to determine the total concentration of labeled metabolites. On the basis of the concentration information, a 12 C-labeled individual sample is mixed with an equal mole amount of a 13 C-labeled pool or control for relative metabolite quantification. The 12 C-/ 13 C-labeled mixtures are individually analyzed by LC-MS, and the resultant peak pairs of labeled metabolites in MS are measured for relative quantification and metabolite identification. A standard library of 85 hydroxyl compounds containing MS, retention time, and MS/MS information was constructed for positive metabolite identification based on matches of two or all three of these parameters with those of an unknown. Using human urine as an example, we analyzed samples of 1:1 12 C-/ 13 C-labeled urine in triplicate with triplicate runs per sample and detected an average of 3759 ± 45 peak pairs or metabolites per run and 3538 ± 71 pairs per sample with 3093 pairs in common (n = 9). Out of the 3093 peak pairs, 2304 pairs (75%) could be positively or putatively identified based on metabolome database searches, including 20 pairs positively identified using the dansylated hydroxyl standards library. The majority of detected metabolites were those containing hydroxyl groups. This technique opens a new avenue for the detailed characterization of the hydroxyl submetabolome in metabolomics research.

Knowledge-based modeling of a legume lectin and docking of the carbohydrate ligand: the Ulex europaeus lectin I and its interaction with fucose.

PubMed

Gohier, A; Espinosa, J F; Jimenez-Barbero, J; Carrupt, P A; Pérez, S; Imberty, A

1996-12-01

Ulex europaeus isolectin I is specific for fucose-containing oligosaccharide such as H type 2 trisaccharide alpha-L-Fuc (1-->2) beta-D-Gal (1-->4) beta-D-GlcNAc. Several legume lectins have been crystallized and modeled, but no structural data are available concerning such fucose-binding lectin. The three-dimensional structure of Ulex europaeus isolectin I has been constructed using seven legume lectins for which high-resolution crystal structures were available. Some conserved water molecules, as well as the structural cations, were taken into account for building the model. In the predicted binding site, the most probable locations of the secondary hydroxyl groups were determined using the GRID method. Several possible orientations could be determined for a fucose residue. All of the four possible conformations compatible with energy calculations display several hydrogen bonds with Asp-87 and Ser-132 and a stacking interaction with Tyr-220 and Phe-136. In two orientations, the O-3 and O-4 hydroxyl groups of fucose are the most buried ones, whereas two other, the O-2 and O-3 hydroxyl groups are at the bottom of the site. Possible docking modes are also studied by analysis of the hydrophobic and hydrophilic surfaces for both the ligand and the protein. The SCORE method allows for a quantitative evaluation of the complementarity of these surfaces, on the basis of molecular lipophilicity calculations. The predictions presented here are compared with known biochemical data.

The metabolism of anabolic-androgenic steroids in the greyhound.

PubMed

McKinney, Andrew R; Cawley, Adam T; Young, E Bruce; Kerwick, Carmel M; Cunnington, Karen; Stewart, Rhiannon T; Ambrus, Joseph I; Willis, Anthony C; McLeod, Malcolm D

2013-04-01

Effective control of the use of anabolic-androgenic steroids (AASs) in animal sports is essential in order to ensure both animal welfare and integrity. In order to better police their use in Australian and New Zealand greyhound racing, thorough metabolic studies have been carried out on a range of registered human and veterinary AASs available in the region. Canine metabolic data are presented for the AASs boldenone, danazol, ethylestrenol, mesterolone, methandriol, nandrolone and norethandrolone. The principal Phase I metabolic processes observed were the reduction of A-ring unsaturations and/or 3-ketones with either 3α,5β- or 3β,5α-stereochemistry, the oxidation of secondary 17β-hydroxyl groups and 16α-hydroxylation. The Phase II β-glucuronylation of sterol metabolites was extensive. The presented data have enabled the effective analysis of AASs and their metabolites in competition greyhound urine samples.

Fragmentation characteristics of hydroxycinnamic acids in ESI-MSn by density functional theory.

PubMed

Yin, Zhi-Hui; Sun, Chang-Hai; Fang, Hong-Zhuang

2017-07-01

This work aims to analyze the electrospray ionization multistage mass spectrometry (ESI-MS n ) fragmentation characteristics of hydroxycinnamic acids (HCAs) in negative ion mode. The geometric parameters, energies, natural bond orbitals and frontier orbitals of fragments were calculated by density functional theory (DFT) to investigate mass spectral fragmentation mechanisms. The results showed that proton transfer always occurred during fragmentation of HCAs; their quasi-molecular ions ([M - H] - ) existed in more than one form and were mainly with the lowest energy. The fragmentation characteristics included the followings: (1) according to the different substitution position of phenolic hydroxyl group, the ring contraction reaction by CO elimination from benzene was in an increasingly difficult order: m-phenolic hydroxyl > p-phenolic hydroxyl > o-phenolic hydroxyl; and (2) ortho effect always occurred in o-dihydroxycinnamic acids (o-diHCAs), i.e. one phenolic hydroxyl group offered H + , which combined with the other one to lose H 2 O. In addition, there was a nucleophilic reaction during ring contraction in diHCAs that oxygen atom attacked the carbon atom binding with the other phenolic hydroxyl to lose CO 2 . The fragmentation characteristics and mechanism of HCAs could be used for analysis and identification of such compounds quickly and effectively, and as reference for structural analogues by ESI-MS. Copyright © 2017 John Wiley & Sons, Ltd. Copyright © 2017 John Wiley & Sons, Ltd.

Metabolite proving fungal cleavage of the aromatic core part of a fluoroquinolone antibiotic

PubMed Central

2012-01-01

Liquid cultures of the basidiomycetous fungus Gloeophyllum striatum were employed to study the biodegradation of pradofloxacin, a new veterinary fluoroquinolone antibiotic carrying a CN group at position C-8. After 16 days of incubation, metabolites were purified by micro-preparative high-performance liquid chromatography. Four metabolites could be identified by co-chromatography with chemically synthesized standards. The chemical structures of three compounds were resolved by 1H-nuclear magnetic resonance spectroscopy plus infrared spectroscopy in one case. All metabolites were confirmed by high resolution mass spectrometry-derived molecular formulae. They comprised compounds in which the carboxyl group or the fluorine atom had been exchanged for a hydroxyl group. Furthermore, replacement of the CN group and the intact amine moiety by a hydroxyl group as well as degradation of the amine substituent were observed. The chemical structure of a catechol-type fluoroquinolone metabolite (F-5) could be fully defined for the first time. The latter initiated a hypothetical degradation sequence providing a unique metabolite, F-13, which consisted of the cyclopropyl-substituted pyridone ring still carrying C-7 and C-8 of pradofloxacin, now linked by a double bond and substituted by a hydroxyl and the CN group, respectively. Most likely, all reactions were hydroxyl radical-driven. Metabolite F-13 proves fungal cleavage of the aromatic fluoroquinolone core for the first time. Hence, two decades after the emergence of the notion of the non-biodegradability of fluoroquinolones, fungal degradation of all key structural elements has been proven. PMID:22214407

Free radical scavenging injectable hydrogels for regenerative therapy.

PubMed

Komeri, Remya; Thankam, Finosh Gnanaprakasam; Muthu, Jayabalan

2017-02-01

Pathological free radicals generated from inflamed and infarcted cardiac tissues interferes natural tissue repair mechanisms. Hypoxic microenvironment at the injured zone of non-regenerating cardiac tissues hinders the therapeutic attempts including cell therapy. Here we report an injectable, cytocompatible, free radical scavenging synthetic hydrogel formulation for regenerative therapy. New hydrogel (PEAX-P) is prepared with D-xylitol-co-fumarate-co-poly ethylene adipate-co-PEG comaromer (PEAX) and PEGDiacrylate. PEAX-P hydrogel swells 4.9 times the initial weight and retains 100.07kPa Young modulus at equilibrium swelling, which is suitable for cardiac applications. PEAX-P hydrogel retains elastic nature even at 60% compressive strain, which is favorable to fit with the dynamic and elastic natural tissue counterparts. PEAX-P hydrogel scavenges 51% DPPH radical, 40% hydroxyl radicals 41% nitrate radicals with 31% reducing power. The presence of hydrogel protects 62% cardiomyoblast cells treated with stress inducing media at LD 50 concentration. The free hydroxyl groups in sugar alcohols of the comacromer influence the free radical scavenging. Comparatively, PEAX-P hydrogel based on xylitol evinces slightly lower scavenging characteristics than with previously reported PEAM-P hydrogel containing mannitol having more hydroxyl groups. The possible free radical scavenging mechanism of the present hydrogel relies on the free π electrons associated with uncrosslinked fumarate bonds, hydrogen atoms associated with sugar alcohols/PEG and radical dilution by free water in the matrix. Briefly, the present PEAX-P hydrogel is a potential injectable system for combined antioxidant and regenerative therapy. Copyright © 2016 Elsevier B.V. All rights reserved.

Aromatic aldehydes at the active site of aldehyde oxidoreductase from Desulfovibrio gigas: reactivity and molecular details of the enzyme-substrate and enzyme-product interaction.

PubMed

Correia, Hugo D; Marangon, Jacopo; Brondino, Carlos D; Moura, Jose J G; Romão, Maria J; González, Pablo J; Santos-Silva, Teresa

2015-03-01

Desulfovibrio gigas aldehyde oxidoreductase (DgAOR) is a mononuclear molybdenum-containing enzyme from the xanthine oxidase (XO) family, a group of enzymes capable of catalyzing the oxidative hydroxylation of aldehydes and heterocyclic compounds. The kinetic studies reported in this work showed that DgAOR catalyzes the oxidative hydroxylation of aromatic aldehydes, but not heterocyclic compounds. NMR spectroscopy studies using (13)C-labeled benzaldehyde confirmed that DgAOR catalyzes the conversion of aldehydes to the respective carboxylic acids. Steady-state kinetics in solution showed that high concentrations of the aromatic aldehydes produce substrate inhibition and in the case of 3-phenyl propionaldehyde a suicide substrate behavior. Hydroxyl-substituted aromatic aldehydes present none of these behaviors but the kinetic parameters are largely affected by the position of the OH group. High-resolution crystallographic structures obtained from single crystals of active-DgAOR soaked with benzaldehyde showed that the side chains of Phe425 and Tyr535 are important for the stabilization of the substrate in the active site. On the other hand, the X-ray data of DgAOR soaked with trans-cinnamaldehyde showed a cinnamic acid molecule in the substrate channel. The X-ray data of DgAOR soaked with 3-phenyl propionaldehyde showed clearly how high substrate concentrations inactivate the enzyme by binding covalently at the surface of the enzyme and blocking the substrate channel. The different reactivity of DgAOR versus aldehyde oxidase and XO towards aromatic aldehydes and N-heterocyclic compounds is explained on the basis of the present kinetic and structural data.

Mobilization of Copper ions by Flavonoids in Human Peripheral Lymphocytes Leads to Oxidative DNA Breakage: A Structure Activity Study.

PubMed

Arif, Hussain; Rehmani, Nida; Farhan, Mohd; Ahmad, Aamir; Hadi, Sheikh Mumtaz

2015-11-09

Epidemiological studies have linked dietary consumption of plant polyphenols with lower incidence of various cancers. In particular, flavonoids (present in onion, tomato and other plant sources) induce apoptosis and cytotoxicity in cancer cells. These can therefore be used as lead compounds for the synthesis of novel anticancer drugs with greater bioavailability. In the present study, we examined the chemical basis of cytotoxicity of flavonoids by studying the structure-activity relationship of myricetin (MN), fisetin (FN), quercetin (QN), kaempferol (KL) and galangin (GN). Using single cell alkaline gel electrophoresis (comet assay), we established the relative efficiency of cellular DNA breakage as MN > FN > QN > KL > GN. Also, we determined that the cellular DNA breakage was the result of mobilization of chromatin-bound copper ions and the generation of reactive oxygen species. The relative DNA binding affinity order was further confirmed using molecular docking and thermodynamic studies through the interaction of flavonoids with calf thymus DNA. Our results suggest that novel anti-cancer molecules should have ortho-dihydroxy groups in B-ring and hydroxyl groups at positions 3 and 5 in the A-ring system. Additional hydroxyl groups at other positions further enhance the cellular cytotoxicity of the flavonoids.

Mobilization of Copper ions by Flavonoids in Human Peripheral Lymphocytes Leads to Oxidative DNA Breakage: A Structure Activity Study

PubMed Central

Arif, Hussain; Rehmani, Nida; Farhan, Mohd; Ahmad, Aamir; Hadi, Sheikh Mumtaz

2015-01-01

Epidemiological studies have linked dietary consumption of plant polyphenols with lower incidence of various cancers. In particular, flavonoids (present in onion, tomato and other plant sources) induce apoptosis and cytotoxicity in cancer cells. These can therefore be used as lead compounds for the synthesis of novel anticancer drugs with greater bioavailability. In the present study, we examined the chemical basis of cytotoxicity of flavonoids by studying the structure–activity relationship of myricetin (MN), fisetin (FN), quercetin (QN), kaempferol (KL) and galangin (GN). Using single cell alkaline gel electrophoresis (comet assay), we established the relative efficiency of cellular DNA breakage as MN > FN > QN > KL > GN. Also, we determined that the cellular DNA breakage was the result of mobilization of chromatin-bound copper ions and the generation of reactive oxygen species. The relative DNA binding affinity order was further confirmed using molecular docking and thermodynamic studies through the interaction of flavonoids with calf thymus DNA. Our results suggest that novel anti-cancer molecules should have ortho-dihydroxy groups in B-ring and hydroxyl groups at positions 3 and 5 in the A-ring system. Additional hydroxyl groups at other positions further enhance the cellular cytotoxicity of the flavonoids. PMID:26569217

Poly(hydroxyl urethane) compositions and methods of making and using the same

DOEpatents

Luebke, David; Nulwala, Hunaid; Tang, Chau

2016-01-26

Methods and compositions relating to poly(hydroxyl urethane) compounds are described herein that are useful as, among other things, binders and adhesives. The cross-linked composition is achieved through the reaction of a cyclic carbonate, a compound having two or more thiol groups, and a compound having two or more amine functional groups. In addition, a method of adhesively binding two or more substrates using the cross-linked composition is provided.

Poly(hydroxyl urethane) compositions and methods of making and using the same

DOEpatents

Luebke, David; Nulwala, Hunaid; Tang, Chau

2014-12-16

Methods and compositions relating to poly(hydroxyl urethane) compounds are described herein that are useful as, among other things, binders and adhesives. The cross-linked composition is achieved through the reaction of a cyclic carbonate, a compound having two or more thiol groups, and a compound having two or more amine functional groups. In addition, a method of adhesively binding two or more substrates using the cross-linked composition is provided.

Density Functional Theory Calculations of the Quantum Capacitance of Graphene Oxide as a Supercapacitor Electrode.

PubMed

Song, Ce; Wang, Jinyan; Meng, Zhaoliang; Hu, Fangyuan; Jian, Xigao

2018-03-31

Graphene oxide has become an attractive electrode-material candidate for supercapacitors thanks to its higher specific capacitance compared to graphene. The quantum capacitance makes relative contributions to the specific capacitance, which is considered as the major limitation of graphene electrodes, while the quantum capacitance of graphene oxide is rarely concerned. This study explores the quantum capacitance of graphene oxide, which bears epoxy and hydroxyl groups on its basal plane, by employing density functional theory (DFT) calculations. The results demonstrate that the total density of states near the Fermi level is significantly enhanced by introducing oxygen-containing groups, which is beneficial for the improvement of the quantum capacitance. Moreover, the quantum capacitances of the graphene oxide with different concentrations of these two oxygen-containing groups are compared, revealing that more epoxy and hydroxyl groups result in a higher quantum capacitance. Notably, the hydroxyl concentration has a considerable effect on the capacitive behavior. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

A comprehensive review of techniques for biofunctionalization of titanium

PubMed Central

2011-01-01

A number of surface modification techniques using immobilization of biofunctional molecules of Titanium (Ti) for dental implants as well as surface properties of Ti and Ti alloys have been developed. The method using passive surface oxide film on titanium takes advantage of the fact that the surface film on Ti consists mainly of amorphous or low-crystalline and non-stoichiometric TiO2. In another method, the reconstruction of passive films, calcium phosphate naturally forms on Ti and its alloys, which is characteristic of Ti. A third method uses the surface active hydroxyl group. The oxide surface immediately reacts with water molecules and hydroxyl groups are formed. The hydroxyl groups dissociate in aqueous solutions and show acidic and basic properties. Several additional methods are also possible, including surface modification techniques, immobilization of poly(ethylene glycol), and immobilization of biomolecules such as bone morphogenetic protein, peptide, collagen, hydrogel, and gelatin. PMID:22324003

Evaluation of newly synthesized and commercially available charged cyclomaltooligosaccharides (cyclodextrins) for capillary electrokinetic chromatography.

PubMed

Culha, Mustafa; Schell, Fred M; Fox, Shannon; Green, Thomas; Betts, Thomas; Sepaniak, Michael J

2004-01-22

A highly new charged cyclodextrin (CD) derivatives, (6-O-carboxymethyl-2,3-di-O-methyl)cyclomaltoheptaoses (CDM-beta-CDs), was synthesized and characterized as anionic reagents for capillary electrophoresis (CE) in an electrokinetic chromatography mode of separation. Substitution with dimethyl groups at the secondary hydroxyl sites of the CD is aimed at influencing the magnitude and selectivity of analyte-CD interactions, while substitution by carboxymethyl groups at the primary hydroxyl sites provides for high charge and electrophoretic mobility. Full regioselective methylation at the secondary hydroxyl sites was achieved in this work, while substitution at the primary hydroxyl sites generated a mixture of multiply charged products. The separation performance of CDM-beta-CD was evaluated using a variety of analyte mixtures. The results obtained from commercially available negatively charged cyclodextrins, heptakis(2,3-di-O-methyl-6-O-sulfo)cyclomaltoheptaose (HDMS-beta-CD) and O-(carboxymethyl)cyclomaltoheptaose (CM-beta-CD) with an average degree of substitution one (DS 1), were compared to CDM-beta-CD using a sample composed of eight positional isomers of dihydroxynaphthalene. Four hydroxylated polychlorobiphenyl derivatives, a group of chiral and isomeric catchecins, and chiral binaphthyl compounds were also separated with CDM-beta-CD. The effect of adding neutral beta-cyclodextrin (beta-CD) into the running buffer containing charged cyclodextrins was investigated and provided evidence of significant inter-CD interactions. Under certain running buffer conditions, the charged cyclodextrins also appear to adsorb to the capillary walls to various degrees.

Hydroxylation of p-substituted phenols by tyrosinase: Further insight into the mechanism of tyrosinase activity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Munoz-Munoz, Jose Luis; Berna, Jose; Garcia-Molina, Maria del Mar

2012-07-27

Highlights: Black-Right-Pointing-Pointer The action the copper complexes and tyrosinase on phenols is equivalent. Black-Right-Pointing-Pointer Isotope effect showed that nucleophilic attack to copper atom may be the slower step. Black-Right-Pointing-Pointer The value of {rho} (Hammett constant) supports an electrophilic aromatic substitution. Black-Right-Pointing-Pointer Data obtained in steady state pH 7 conditions support the mechanism of Scheme 1SM. -- Abstract: A study of the monophenolase activity of tyrosinase by measuring the steady state rate with a group of p-substituted monophenols provides the following kinetic information: k{sub cat}{sup m} and the Michaelis constant, K{sub M}{sup m}. Analysis of these data taking into account chemicalmore » shifts of the carbon atom supporting the hydroxyl group ({delta}) and {sigma}{sub p}{sup +}, enables a mechanism to be proposed for the transformation of monophenols into o-diphenols, in which the first step is a nucleophilic attack on the copper atom on the form E{sub ox} (attack of the oxygen of the hydroxyl group of C-1 on the copper atom) followed by an electrophilic attack (attack of the hydroperoxide group on the ortho position with respect to the hydroxyl group of the benzene ring, electrophilic aromatic substitution with a reaction constant {rho} of -1.75). These steps show the same dependency on the electronic effect of the substituent groups in C-4. Furthermore, a study of a solvent deuterium isotope effect on the oxidation of monophenols by tyrosinase points to an appreciable isotopic effect. In a proton inventory study with a series of p-substituted phenols, the representation of k{sub cat}{sup f{sub n}}/k{sub cat}{sup f{sub 0}} against n (atom fractions of deuterium), where k{sub cat}{sup f{sub n}} is the catalytic constant for a molar fraction of deuterium (n) and k{sub cat}{sup f{sub 0}} is the corresponding kinetic parameter in a water solution, was linear for all substrates. These results indicate that only one of the proton transfer processes from the hydroxyl groups involved the catalytic cycle is responsible for the isotope effects. We suggest that this step is the proton transfer from the hydroxyl group of C-1 to the peroxide of the oxytyrosinase form (E{sub ox}). After the nucleophilic attack, the incorporation of the oxygen in the benzene ring occurs by means of an electrophilic aromatic substitution mechanism in which there is no isotopic effect.« less

Potential benefits of triethylamine as n-electron donor in the estimation of forskolin by electronic absorption and emission spectroscopy

NASA Astrophysics Data System (ADS)

Raju, Gajula; Ram Reddy, A.

2016-02-01

Diterpenoid forskolin was isolated from Coleus forskolii. The electronic absorption and emission studies of forskolin were investigated in various solvents with an aim to improve its detection limits. The two chromophores present in the diterpenoid are not conjugated leading to the poor absorption and emission of UV light. The absorption and fluorescence spectra were solvent specific. In the presence of a monodentate ligand, triethylamine the detection of forskolin is improved by 3.63 times in ethanol with the fluorescence method and 3.36 times in DMSO by the absorption spectral method. The longer wavelength absorption maximum is blue shifted while the lower energy fluorescence maximum is red shifted in the presence of triethylamine. From the wavelength of fluorescence maxima of the exciplex formed between excited forskolin and triethylamine it is concluded that the order of reactivity of hydroxyl groups in the excited state forskolin is in the reverse order to that of the order of the reactivity of hydroxyl groups in its ground state.

α- tocopherol’s location in membranes is not affected by their composition

DOE PAGES

Marquardt, Drew; Kucerka, Norbert; Katsaras, John; ...

2014-10-15

To this day, α-tocopherol's (aToc) role in humans is not well known. In previous studies, we have tried to connect aToc's biological function with its location in a-lipid bilayer. In the present study, we have determined, by means of small-angle neutron diffraction, that not only is aToc's hydroxyl group located high in the membrane but its tail also resides far from the center of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) bilayers. In addition, we located aToc's hydroxyl group above the lipid backbone in 1-palmitoyl-2-oleoyl- sn-glycero-3-phosphoethanolamine (POPE), 1-palmitoyl-2-oleoyl- sn-glycero-3-phospho-L-serine (POPS), and Sphingomyelin bilayers, suggesting that aToc's location near the lipid water interface may be amore » universal property of vitamin E. Lastly, in light of these data, how aToc efficiently terminates lipid hydroperoxy radicals at the membrane center remains an open question.« less

Transesterification of PHA to oligomers covalently bonded with (bio)active compounds containing either carboxyl or hydroxyl functionalities.

PubMed

Kwiecień, Iwona; Radecka, Iza; Kowalczuk, Marek; Adamus, Grażyna

2015-01-01

This manuscript presents the synthesis and structural characterisation of novel biodegradable polymeric controlled-release systems of pesticides with potentially higher resistance to weather conditions in comparison to conventional forms of pesticides. Two methods for the preparation of pesticide-oligomer conjugates using the transesterification reaction were developed. The first method of obtaining conjugates, which consist of bioactive compounds with the carboxyl group and polyhydroxyalkanoates (PHAs) oligomers, is "one-pot" transesterification. In the second method, conjugates of bioactive compounds with hydroxyl group and polyhydroxyalkanoates oligomers were obtained in two-step method, through cyclic poly(3-hydroxybutyrate) oligomers. The obtained pesticide-PHA conjugates were comprehensively characterised using GPC, 1H NMR and mass spectrometry techniques. The structural characterisation of the obtained products at the molecular level with the aid of mass spectrometry confirmed that both of the synthetic strategies employed led to the formation of conjugates in which selected pesticides were covalently bonded to PHA oligomers via a hydrolysable ester bond.

Hydroxyl orientations in cellobiose and other polyhydroxy compounds – modeling versus experiment

USDA-ARS?s Scientific Manuscript database

Theoretical and experimental gas-phase studies of carbohydrates show that their hydroxyl groups are located in homodromic partial rings that resemble cooperative hydrogen bonds, albeit with long H…O distances and small O-H…O angles. On the other hand, anecdotal experience with disaccharide crystal ...

Hydrogen speciation in hydrated layers on nuclear waste glass

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aines, R.D.; Weed, H.C.; Bates, J.K.

1987-12-31

The hydration of an outer layer on nuclear waste glasses in known to occur during leaching, but the actual speciation of hydrogen (as water or hydroxyl groups) in these layers has not been determined. As part of the Nevada Nuclear Waste Storage Investigations Project, we have used infrared spectroscopy to determine hydrogen speciations in three nuclear waste glass compositions (SRL-131 & 165, and PNL 76-68), which were leached at 90{sup 0}C (all glasses) or hydrated in a vapor-saturated atmosphere at 202{sup 0}C (SRL-131 only). Hydroxyl groups were found in the surface layers of all the glasses. In addition, molecular watermore » was found in the surface of SRL-131 and PNL 76-68 glasses that had been leached for several months in deionized water, and in the vapor-hydrated sample. The water/hydroxyl ratio increases with increasing reaction time; molecular water makes up most of the hydrogen in the thick reaction layers on vapor-phase hydrated glass while only hydroxyl occurs in the least reacted samples. The hydrated layer on the nuclear waste glasses appears to be of relatively low water content (4 to 7% by weight) and is not substantially hydroxylated. Thus, these layers do not have many of the properties associated with gel layers.« less

Support effects and reaction mechanism of acetylene trimerization over silica-supported Cu4 clusters: A DFT study

NASA Astrophysics Data System (ADS)

Maleki, Farahnaz; Schlexer, Philomena; Pacchioni, Gianfranco

2018-02-01

Oxide-supported Cu nanoparticles and clusters catalyze a variety of important reactions, such as CO/CO2 hydrogenation to methanol. Recent studies demonstrate that also sub-nanometer clusters consisting of only a few atoms can actively catalyze chemical reactions. In this study, we investigate the interaction between Cu4 clusters and silica-surfaces, considering the de-hydroxylated and the fully hydroxylated α-quartz surfaces. We also considered various dopants such as Ti- and Nb-ions substitutional to Si, respectively, in order to see if an electronic change of the support has an effect on the reaction of the supported cluster. We find that hydroxyl groups can enhance the adsorption energy of the cluster, whereas the dopants have only little effects on the adsorption mode of the Cu cluster. On the fully hydroxylated surface, the cluster may react with the hydroxyl groups via reverse hydrogen spillover. Finally, we explore the reactivity of the silica-supported Cu4 cluster in terms of acetylene trimerization, for which extended Cu surfaces have shown catalytic activity. We find that this reaction should occur with activation barriers below 0.8 eV; Nb-doping of the support does not seem to produce any direct effect on the reactivity of the Cu tetramer.

FTIR and 1H MAS NMR investigations on the correlation between the frequency of stretching vibration and the chemical shift of surface OH groups of solids

NASA Astrophysics Data System (ADS)

Brunner, Eike; Karge, H. G.; Pfeifer, H.

1992-03-01

The study of surface hydroxyl groups of solids, especially of zeolites, belongs to the 'classical' topics of IR spectroscopy since physico-chemical information may be derived from the wavenumber (nu) OH of the stretching vibration of the different hydroxyls. On the other hand, the last decade has seen the development of high resolution solid-state NMR spectroscopy and through the use of the so-called magic-angle-spinning technique (MAS) the signals of different hydroxyl species can be resolved in the 1H NMR spectra of solids. The chemical shift (delta) H describing the position of these lines may be used as well as (nu) OH to characterize quantitatively the strength of acidity of surface OH groups of solids. In a first comparison of (nu) OH with (delta) H for several types of surface OH groups, a linear correlation between them could be found. The aim of this paper was to prove the validity of this correlation for a wide variety of hydroxyls. The IR measurements were carried out on a Perkin-Elmer FTIR spectrometer 1800 at the Fritz Haber Institute of the Max Planck Society, Berlin, and the 1H MAS NMR spectra were recorded on a Bruker MSL- 300 at the University of Leipzig.

Infrared spectroscopy of flavones and flavonols. Reexamination of the hydroxyl and carbonyl vibrations in relation to the interactions of flavonoids with membrane lipids

NASA Astrophysics Data System (ADS)

Baranović, Goran; Šegota, Suzana

2018-03-01

Detailed vibrational assignments for twelve flavonoids (seven flavones (flavone, 3- and 5-hydroxyflavone, chrysin, apigenin, fisetin and luteolin) and five flavonols (galangin, kaempferol, quercetin, morin and myricetin)) have been made based on own and reported experimental data and calculations at the B3LYP/6-31 + G(d,p) level of theory. All the molecules are treated in a uniform way by using the same set of redundancy-free set of internal coordinates. A generalized harmonic mode mixing is used to corroborate the vibrational characteristics of this important class of molecules. Each flavonoid molecule can be treated from the vibrational point of view as made of relatively weakly coupled chromone and phenyl part. It has been shown that the strongest band around 1600 cm- 1 need not be attributable to the Cdbnd O stretching. The way the vibrations of any of the hydroxyl groups are mixed with ring vibrations and vibrations of other neighboring hydroxyl groups is rather involved. This imposes severe limitations on any attempt to describe normal modes of a flavonol in terms of hydroxyl or carbonyl group vibrations. The role of water molecules in the appearance of flavonoid IR spectra is emphasized. Knowing for the great affinity of phosphate groups in lipids towards water, the immediate consequence is a reasonable assumption that flavonoid lipid interactions is mediated by water.

Microbial biotransformation of bioactive flavonoids.

PubMed

Cao, Hui; Chen, Xiaoqing; Jassbi, Amir Reza; Xiao, Jianbo

2015-01-01

The bioactive flavonoids are considered as the most important phytochemicals in food, which exert a wide range of biological benefits for human being. Microbial biotransformation strategies for production of flavonoids have attracted considerable interest because they allow yielding novel flavonoids, which do not exist in nature. In this review, we summarize the existing knowledge on the production and biotransformation of flavonoids by various microbes. The main reactions during microbial biotransformation are hydroxylation, dehydroxylation, O-methylation, O-demethylation, glycosylation, deglycosylation, dehydrogenation, hydrogenation, C ring cleavage of the benzo-γ-pyrone system, cyclization, and carbonyl reduction. Cunninghamella, Penicillium, and Aspergillus strains are very popular to biotransform flavonoids and they can perform almost all the reactions with excellent yields. Aspergillus niger is one of the most applied microorganisms in the flavonoids' biotransformation; for example, A. niger can transfer flavanone to flavan-4-ol, 2'-hydroxydihydrochalcone, flavone, 3-hydroxyflavone, 6-hydroxyflavanone, and 4'-hydroxyflavanone. The hydroxylation of flavones by microbes usually happens on the ortho position of hydroxyl group on the A ring and C-4' position of the B ring and microbes commonly hydroxylate flavonols at the C-8 position. The microorganisms tend to hydroxylate flavanones at the C-5, 6, and 4' positions; however, for prenylated flavanones, dihydroxylation often takes place on the C4α=C5α double bond on the prenyl group (the side chain of A ring). Isoflavones are usually hydroxylated at the C-3' position of the B ring by microorganisms. The microbes convert flavonoids to their 7-O-glycosides and 3-O-glycosides (when flavonoids have a hydroxyl moiety at the C-3 position). The demethylation of multimethoxyl flavonoids by microbes tends to happen at the C-3' and C-4' positions of the B ring. Multimethoxyl flavanones and isoflavone are demethylated at the C-7 and C-4' positions. The O-methylation of flavonols happens at the C-3' and C-4' and microorganisms O-methylate flavones at the C-6 position and the O-methylation of flavanones, usually took place on the hydroxyl groups of the A ring. The prenyl flavanones were cyclized at the prenyl side chain to form a new five-member ring attached to the A ring. Chalcones were regioselectively cyclized to flavanones. Hydrogenation of flavonoids was only reported on transformation of chalcones to dihydrochalcones. The dehydrogenation of flavanoids to flavonoids was not comprehensively studied. Copyright © 2014 Elsevier Inc. All rights reserved.

Moringa oleifera Lam. seed extract prevents fat diet induced oxidative stress in mice and protects liver cell-nuclei from hydroxyl radical mediated damage.

PubMed

Das, Nilanjan; Ganguli, Debdutta; Dey, Sanjit

2015-12-01

High fat diet (HFD) prompts metabolic pattern inducing reactive oxygen species (ROS) production in mitochondria thereby triggering multitude of chronic disorders in human. Antioxidants from plant sources may be an imperative remedy against this disorder. However, it requires scientific validation. In this study, we explored if (i) Moringa oleifera seed extract (MoSE) can neutralize ROS generated in HFD fed mice; (ii) protect cell-nuclei damage developed by Fenton reaction in vitro. Swiss mice were fed with HFD to develop oxidative stress model (HFD group). Other groups were control, seed extract alone treated, and MoSE simultaneously (HS) treated. Treatment period was of 15 days. Antioxidant enzymes with tissue nitrite content (TNC) and lipid peroxidation (LPO) were estimated from liver homogenate. HS group showed significantly higher (P < 0.05) superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), reduced glutathione (GSH) activity, and ferric reducing antioxidant power (FRAP) compared to only HFD fed group. Further, TNC and LPO decreased significantly (P < 0.05) in HS group compared to HFD fed group. MoSE also protected hepatocytes nuclei from the hydroxyl radicals generated by Fenton reaction. MoSE was found to be polyphenol rich with potent reducing power, free radicals and hydroxyl radicals scavenging activity. Thus, MoSE exhibited robust antioxidant prospective to neutralize ROS developed in HFD fed mice and also protected the nuclei damage from hydroxyl radicals. Hence, it can be used as herbal medication against HFD induced ROS mediated disorders.

Standardization of chemical analytical techniques for pyrolysis bio-oil: history, challenges, and current status of methods

DOE PAGES

Ferrell, Jack R.; Olarte, Mariefel V.; Christensen, Earl D.; ...

2016-07-05

Here, we discuss the standardization of analytical techniques for pyrolysis bio-oils, including the current status of methods, and our opinions on future directions. First, the history of past standardization efforts is summarized, and both successful and unsuccessful validation of analytical techniques highlighted. The majority of analytical standardization studies to-date has tested only physical characterization techniques. In this paper, we present results from an international round robin on the validation of chemical characterization techniques for bio-oils. Techniques tested included acid number, carbonyl titrations using two different methods (one at room temperature and one at 80 °C), 31P NMR for determination ofmore » hydroxyl groups, and a quantitative gas chromatography–mass spectrometry (GC-MS) method. Both carbonyl titration and acid number methods have yielded acceptable inter-laboratory variabilities. 31P NMR produced acceptable results for aliphatic and phenolic hydroxyl groups, but not for carboxylic hydroxyl groups. As shown in previous round robins, GC-MS results were more variable. Reliable chemical characterization of bio-oils will enable upgrading research and allow for detailed comparisons of bio-oils produced at different facilities. Reliable analytics are also needed to enable an emerging bioenergy industry, as processing facilities often have different analytical needs and capabilities than research facilities. We feel that correlations in reliable characterizations of bio-oils will help strike a balance between research and industry, and will ultimately help to -determine metrics for bio-oil quality. Lastly, the standardization of additional analytical methods is needed, particularly for upgraded bio-oils.« less

Standardization of chemical analytical techniques for pyrolysis bio-oil: history, challenges, and current status of methods

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ferrell, Jack R.; Olarte, Mariefel V.; Christensen, Earl D.

Here, we discuss the standardization of analytical techniques for pyrolysis bio-oils, including the current status of methods, and our opinions on future directions. First, the history of past standardization efforts is summarized, and both successful and unsuccessful validation of analytical techniques highlighted. The majority of analytical standardization studies to-date has tested only physical characterization techniques. In this paper, we present results from an international round robin on the validation of chemical characterization techniques for bio-oils. Techniques tested included acid number, carbonyl titrations using two different methods (one at room temperature and one at 80 °C), 31P NMR for determination ofmore » hydroxyl groups, and a quantitative gas chromatography–mass spectrometry (GC-MS) method. Both carbonyl titration and acid number methods have yielded acceptable inter-laboratory variabilities. 31P NMR produced acceptable results for aliphatic and phenolic hydroxyl groups, but not for carboxylic hydroxyl groups. As shown in previous round robins, GC-MS results were more variable. Reliable chemical characterization of bio-oils will enable upgrading research and allow for detailed comparisons of bio-oils produced at different facilities. Reliable analytics are also needed to enable an emerging bioenergy industry, as processing facilities often have different analytical needs and capabilities than research facilities. We feel that correlations in reliable characterizations of bio-oils will help strike a balance between research and industry, and will ultimately help to -determine metrics for bio-oil quality. Lastly, the standardization of additional analytical methods is needed, particularly for upgraded bio-oils.« less

Improved lignin polyurethane properties with Lewis acid treatment.

PubMed

Chung, Hoyong; Washburn, Newell R

2012-06-27

Chemical modification strategies to improve the mechanical properties of lignin-based polyurethanes are presented. We hypothesized that treatment of lignin with Lewis acids would increase the concentration of hydroxyl groups available to react with diisocyanate monomers. Under the conditions used, hydrogen bromide-catalyzed modification resulted in a 28% increase in hydroxyl group content. Associated increases in hydrophilicity of solvent-cast thin films were also recorded as evidenced by decreases in water contact angle. Polyurethanes were then prepared by first preparing a prepolymer based on mixtures of toluene-2,4-diisocyanate (TDI) and unmodified or modified lignin, then polymerization was completed through addition of polyethylene glycol (PEG), resulting in mass ratios of TDI:lignin:PEG of 43:17:40 in the compositions investigated here. The mixture of TDI and unmodified lignin resulted in a lignin powder at the bottom of the liquid, suggesting it did not react directly with TDI. However, a homogeneous solution resulted when TDI and the hydrogen bromide-treated lignin were mixed, suggesting demethylation indeed increased reactivity and resulted in better integration of lignin into the urethane network. Significant improvements in mechanical properties of modified lignin polyurethanes were observed, with a 6.5-fold increase in modulus, which were attributed to better integration of the modified lignin into the covalent polymer network due to the higher concentration of hydroxyl groups. This research indicates that chemical modification strategies can lead to significant improvements in the properties of lignin-based polymeric materials using a higher fraction of an inexpensive lignin monomer from renewable resources and a lower fraction an expensive, petroleum-derived isocyanate monomer to achieve the required material properties.

Selectivity of substrate binding and ionization of 2-methyl-3-hydroxypyridine-5-carboxylic acid oxygenase.

PubMed

Luanloet, Thikumporn; Sucharitakul, Jeerus; Chaiyen, Pimchai

2015-08-01

2-Methyl-3-hydroxypyridine-5-carboxylic acid (MHPC) oxygenase (EC 1.14.12.4) from Pseudomonas sp. MA-1 is a flavin-dependent monooxygenase that catalyzes a hydroxylation and aromatic ring cleavage reaction. The functional roles of two residues, Tyr223 and Tyr82, located ~ 5 Å away from MHPC, were characterized using site-directed mutagenesis, along with ligand binding, product analysis and transient kinetic experiments. Mutation of Tyr223 resulted in enzyme variants that were impaired in their hydroxylation activity and had Kd values for substrate binding 5-10-fold greater than the wild-type enzyme. Because this residue is adjacent to the water molecule that is located next to the 3-hydroxy group of MHPC, the results indicate that the interaction between Tyr223, H2 O and the 3-hydroxyl group of MHPC are important for substrate binding and hydroxylation. By contrast, the Kd for substrate binding of Tyr82His and Tyr82Phe variants were similar to that of the wild-type enzyme. However, only ~ 40-50% of the substrate was hydroxylated in the reactions of both variants, whereas most of the substrate was hydroxylated in the wild-type enzyme reaction. In free solution, MHPC or 5-hydroxynicotinic acid exists in a mixture of monoanionic and tripolar ionic forms, whereas only the tripolar ionic form binds to the wild-type enzyme. The binding of tripolar ionic MHPC would allow efficient hydroxylation through an electrophilic aromatic substitution mechanism. For the Tyr82His and Tyr82Phe variants, both forms of substrates can bind to the enzymes, indicating that the mutation at Tyr82 abolished the selectivity of the enzyme towards the tripolar ionic form. Transient kinetic studies indicated that the hydroxylation rate constants of both Tyr82 variants are approximately two- to 2.5-fold higher than that of the wild-type enzyme. Altogether, our findings suggest that Tyr82 is important for the binding selectivity of MHPC oxygenase towards the tripolar ionic species, whereas the interaction between Tyr223 and the substrate is important for ensuring hydroxylation. These results highlight how the active site of a flavoenzyme is able to deal with the presence of multiple forms of a substrate in solution and ensure efficient hydroxylation. © 2015 FEBS.

A first principle study of graphene functionalized with hydroxyl, nitrile, or methyl groups

NASA Astrophysics Data System (ADS)

Barhoumi, M.; Rocca, D.; Said, M.; Lebègue, S.

2017-01-01

By means of ab initio calculations, we study the functionalization of graphene by different chemical groups such as hydroxyl, nitrile, or methyl. Two extreme cases of functionalization are considered: a single group on a supercell of graphene and a sheet of graphene fully functionalized. Once the equilibrium geometry is obtained by density functional theory, we found that the systems are metallic when a single group is attached to the sheet of graphene. With the exception of the nitrile functionalized boat configuration, a large bandgap is obtained at full coverage. Specifically, by using the GW approximation, our calculated bandgaps are direct and range between 5.0 and 5.5 eV for different configurations of hydroxyl functionalized graphene. An indirect GW bandgap of 6.50 eV was found in nitrile functionalized graphene while the methyl group functionalization leads to a direct bandgap with a value of 4.50 eV. Since in the two limiting cases of minimal and full coverage, the electronic structure changes drastically from a metal to a wide bandgap semiconductor, a series of intermediate states might be expected by tuning the amount of functionalization with these different groups.

Metabolic capabilities of cytochrome P450 enzymes in Chinese liver microsomes compared with those in Caucasian liver microsomes

PubMed Central

Yang, Junling; He, Minxia M; Niu, Wei; Wrighton, Steven A; Li, Li; Liu, Yang; Li, Chuan

2012-01-01

AIM The most common causes of variability in drug response include differences in drug metabolism, especially when the hepatic cytochrome P450 (CYP) enzymes are involved. The current study was conducted to assess the differences in CYP activities in human liver microsomes (HLM) of Chinese or Caucasian origin. METHODS The metabolic capabilities of CYP enzymes in 30 Chinese liver microsomal samples were compared with those of 30 Caucasian samples utilizing enzyme kinetics. Phenacetin O-deethylation, coumarin 7-hydroxylation, bupropion hydroxylation, amodiaquine N-desethylation, diclofenac 4′-hydroxylation (S)-mephenytoin 4′-hydroxylation, dextromethorphan O-demethylation, chlorzoxazone 6-hydroxylation and midazolam 1′-hydroxylation/testosterone 6β-hydroxylation were used as probes for activities of CYP1A2, CYP2A6, CYP2B6, CYP2C8, CYP2C9, CYP2C19, CYP2D6, CYP2E1 and CYP3A, respectively. Mann-Whitney U test was used to assess the differences. RESULTS The samples of the two ethnic groups were not significantly different in cytochrome-b5 concentrations but were significantly different in total CYP concentrations and NADPH-P450 reductase activity (P < 0.05). Significant ethnic differences in intrinsic clearance were observed for CYP1A2, CYP2C9, CYP2C19 and CYP2E1; the median values of the Chinese group were 54, 58, 26, and 35% of the corresponding values of the Caucasian group, respectively. These differences were associated with differences in Michaelis constant or maximum velocity. Despite negligible difference in intrinsic clearance, the Michaelis constant of CYP2B6 appeared to have a significant ethnic difference. No ethnic difference was observed for CYP2A6, CYP2C8, CYP2D6 and CYP3A. CONCLUSIONS These data extend our knowledge on the ethnic differences in CYP enzymes and will have implications for drug discovery and drug therapy for patients from different ethnic origins. PMID:21815912

Probing Competitive and Co-operative Hydroxyl and Ammonium Hydrogen-Bonding Directed Epoxidations.

PubMed

Brambilla, Marta; Brennan, Méabh B; Csatayová, Kristína; Davies, Stephen G; Fletcher, Ai M; Kennett, Alice M R; Lee, James A; Roberts, Paul M; Russell, Angela J; Thomson, James E

2017-10-06

The diastereoselectivities and rates of epoxidation (upon treatment with Cl 3 CCO 2 H then m-CPBA) of a range of cis- and trans-4-aminocycloalk-2-en-1-ol derivatives (containing five-, six-, and seven-membered rings) have been investigated. In all cases where the two potential directing groups can promote epoxidation on opposite faces of the ring scaffold, evidence of competitive epoxidation pathways, promoted by hydrogen-bonding to either the in situ formed ammonium moiety or the hydroxyl group, was observed. In contrast to the relative directing group abilities already established for the six-membered ring system (NHBn ≫ OH > NBn 2 ), an N,N-dibenzylammonium moiety appeared more proficient than a hydroxyl group at directing the stereochemical course of the epoxidation reaction in a five- or seven-membered system. In the former case, this was rationalized by the drive to minimize torsional strain in the transition state being coupled with assistance from hydrogen-bonding to the ammonium moiety. In the latter case, this was ascribed to the steric bulk of the ammonium moiety disfavoring conformations in which hydrogen-bonding to the hydroxyl group results in direction of the epoxidation to the syn face. In cases where the two potential directing groups can promote epoxidation on the same face of the ring scaffold, an enhancement of epoxidation diastereoselectivity was not observed, while introduction of a second, allylic heteroatom to the substrate results in diminishment of the rate of epoxidation in all cases. Presumably, reduction of the nucleophilicity of the olefin by the second, inductively electron-withdrawing heteroatom is the dominant factor, and any assistance to the epoxidation reaction by the potential to form hydrogen-bonds to two directing groups rather than one is clearly unable to overwhelm it.

Chemical Characterization and Water Content Determination of Bio-Oils Obtained from Various Biomass Species using 31P NMR Spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

David, K.; Ben, H.; Muzzy, J.

2012-03-01

Pyrolysis is a promising approach to utilize biomass for biofuels. One of the key challenges for this conversion is how to analyze complicated components in the pyrolysis oils. Water contents of pyrolysis oils are normally analyzed by Karl Fischer titration. The use of 2-chloro-4,4,5,5,-tetramethyl-1,3,2-dioxaphospholane followed by {sup 31}P NMR analysis has been used to quantitatively analyze the structure of hydroxyl groups in lignin and whole biomass. Results: {sup 31}P NMR analysis of pyrolysis oils is a novel technique to simultaneously characterize components and analyze water contents in pyrolysis oils produced from various biomasses. The water contents of various pyrolysis oilsmore » range from 16 to 40 wt%. The pyrolysis oils obtained from Loblolly pine had higher guaiacyl content, while that from oak had a higher syringyl content. Conclusion: The comparison with Karl Fischer titration shows that {sup 31}P NMR could also reliably be used to measure the water content of pyrolysis oils. Simultaneously with analysis of water content, quantitative characterization of hydroxyl groups, including aliphatic, C-5 substituted/syringyl, guaiacyl, p-hydroxyl phenyl and carboxylic hydroxyl groups, could also be provided by {sup 31}P NMR analysis.« less

Metabolomic Discovery of Novel Urinary Galabiosylceramide Analogs as Fabry Disease Biomarkers

NASA Astrophysics Data System (ADS)

Boutin, Michel; Auray-Blais, Christiane

2015-03-01

Fabry disease is an X-linked, complex, multisystemic lysosomal storage disorder presenting marked phenotypic and genotypic variability among affected male and female patients. Glycosphingolipids, mainly globotriaosylceramide (Gb3) isoforms/analogs, globotriaosylsphingosine (lyso-Gb3) and analogs, as well as galabiosylceramide (Ga2) isoforms/analogs accumulate in the vascular endothelium, nerves, cardiomyocytes, renal glomerular and tubular epithelial cells, and biological fluids. The search for biomarkers reflecting disease severity and progression is still on-going. A metabolomic study using quadrupole time-of-flight mass spectrometry has revealed 22 galabiosylceramide isoforms/analogs in urine of untreated Fabry patients classified in seven groups according to their chemical structure: (1) Saturated fatty acid; (2) one extra double bond; (3) two extra double bonds; (4) hydroxylated saturated fatty acid; (5) hydroxylated fatty acid and one extra double bond; (6) hydrated sphingosine and hydroxylated fatty acid; (7) methylated amide linkage. Relative quantification of both Ga2 and Gb3 isoforms/analogs was performed. All these biomarkers are significantly more abundant in urine samples from untreated Fabry males compared with healthy male controls. A significant amount of Ga2 isoforms/analogs, accounting for 18% of all glycosphingolipids analyzed (Ga2 + Gb3 and respective isoforms/analogs), were present in urine of Fabry patients. Gb3 isoforms containing saturated fatty acids are the most abundant (60.9%) compared with 26.3% for Ga2. A comparison between Ga2 isoforms/analogs and their Gb3 counterparts also showed that the proportion of analogs with hydroxylated fatty acids is significantly greater for Ga2 (35.8%) compared with Gb3 (1.9%). These results suggest different biological pathways involved in the synthesis and/or degradation of Gb3 and Ga2 metabolites.

Hydroxyl Ion Diffusion through Radicular Dentine When Calcium Hydroxide Is Used under Different Conditions

PubMed Central

Cai, Michael; Castro Salgado, Jacqueline

2018-01-01

Calcium hydroxide’s anti-bacterial action relies on high pH. The aim here was to investigate hydroxyl ion diffusion through dentine under different conditions. Teeth were divided into control (n = 4) and four experimental groups (n = 10): Group 1—no medicament; Group 2—Calmix; Group 3—Calmix/Ledermix; Group 4—Calasept Plus/Ledermix; Group 5—Pulpdent/smear layer. Deep (inner dentine) and shallow (outer dentine) cavities were cut into each root. pH was measured in these cavities for 12 weeks. The inner and outer dentine pH in Group 2 was significantly higher than all groups. Inner dentine pH in Group 3 was slightly higher than that in Group 4 initially but subsequently comparable. After Day 2, Group 5 had significantly lower pH than Groups 3 and 4. The outer dentine pH in Group 3 started higher than that in Groups 4 and 5, but by Day 28 the difference was insignificant. The time for the inner dentine to reach maximum pH was one week for Group 2 and four weeks for Groups 3 and 4. The time for the outer dentine to reach maximum pH was eight weeks for all experimental groups. Mixing different Ca(OH)2 formulations with Ledermix gave similar hydroxyl ion release but pH and total diffusion was lower than Ca(OH)2 alone. The smear layer inhibited diffusion. PMID:29342093

ipso-Hydroxylation and Subsequent Fragmentation: a Novel Microbial Strategy To Eliminate Sulfonamide Antibiotics

PubMed Central

Ricken, Benjamin; Cichocka, Danuta; Parisi, Martina; Lenz, Markus; Wyss, Dominik; Martínez-Lavanchy, Paula M.; Müller, Jochen A.; Shahgaldian, Patrick; Tulli, Ludovico G.; Kohler, Hans-Peter E.; Kolvenbach, Boris A.

2013-01-01

Sulfonamide antibiotics have a wide application range in human and veterinary medicine. Because they tend to persist in the environment, they pose potential problems with regard to the propagation of antibiotic resistance. Here, we identified metabolites formed during the degradation of sulfamethoxazole and other sulfonamides in Microbacterium sp. strain BR1. Our experiments showed that the degradation proceeded along an unusual pathway initiated by ipso-hydroxylation with subsequent fragmentation of the parent compound. The NADH-dependent hydroxylation of the carbon atom attached to the sulfonyl group resulted in the release of sulfite, 3-amino-5-methylisoxazole, and benzoquinone-imine. The latter was concomitantly transformed to 4-aminophenol. Sulfadiazine, sulfamethizole, sulfamethazine, sulfadimethoxine, 4-amino-N-phenylbenzenesulfonamide, and N-(4-aminophenyl)sulfonylcarbamic acid methyl ester (asulam) were transformed accordingly. Therefore, ipso-hydroxylation with subsequent fragmentation must be considered the underlying mechanism; this could also occur in the same or in a similar way in other studies, where biotransformation of sulfonamides bearing an amino group in the para-position to the sulfonyl substituent was observed to yield products corresponding to the stable metabolites observed by us. PMID:23835177

Oxidation of Peptides by Methyl(trifluoromethyl)dioxirane: the Protecting Group Matters

PubMed Central

Rella, Maria Rosaria; Williard, Paul G.

2011-01-01

Representative Boc protected and acetyl protected peptide methyl esters bearing alkyl side chains undergo effective oxidation using methyl(trifluoromethyl)dioxirane (1b) under mild conditions. We observe a protecting group dependency in the chemoselectivity displayed by the dioxirane 1b. N-hydroxylation occurs in the case of the Boc protected peptides, side chain hydroxylation takes place in the case of acetyl protected peptides. Both are attractive transformations since they yield derivatized peptides that serve as valuable synthons. PMID:17221970

Hydroetching of high surface area ceramics using moist supercritical fluids

DOEpatents

Fryxell, Glen; Zemanian, Thomas S.

2004-11-02

Aerogels having a high density of hydroxyl groups and a more uniform pore size with fewer bottlenecks are described. The aerogel is exposed to a mixture of a supercritical fluid and water, whereupon the aerogel forms a high density of hydroxyl groups. The process also relaxes the aerogel into a more open uniform internal structure, in a process referred to as hydroetching. The hydroetching process removes bottlenecks from the aerogels, and forms the hydrogels into more standard pore sizes while preserving their high surface area.

Role of oxygen functional groups for structure and dynamics of interfacial water on low rank coal surface: a molecular dynamics simulation

NASA Astrophysics Data System (ADS)

You, Xiaofang; Wei, Hengbin; Zhu, Xianchang; Lyu, Xianjun; Li, Lin

2018-07-01

Molecular dynamics simulations were employed to study the effects of oxygen functional groups for structure and dynamics properties of interfacial water molecules on the subbituminous coal surface. Because of complex composition and structure, the graphite surface modified by hydroxyl, carboxyl and carbonyl groups was used to represent the surface model of subbituminous coal according to XPS results, and the composing proportion for hydroxyl, carbonyl and carboxyl is 25:3:5. The hydration energy with -386.28 kJ/mol means that the adsorption process between water and coal surface is spontaneous. Density profiles for oxygen atoms and hydrogen atoms indicate that the coal surface properties affect the structural and dynamic characteristics of the interfacial water molecules. The interfacial water exhibits much more ordering than bulk water. The results of radial distribution functions, mean square displacement and local self-diffusion coefficient for water molecule related to three oxygen moieties confirmed that the water molecules prefer to absorb with carboxylic groups, and adsorption of water molecules at the hydroxyl and carbonyl is similar.

A functionalizable polyester with free hydroxyl groups and tunable physiochemical and biological properties

PubMed Central

You, Zhengwei; Cao, Haiping; Gao, Jin; Shin, Paul H.; Day, Billy W.; Wang, Yadong

2010-01-01

Polyesters with free functional groups allow facile modifications with biomolecules, which can lead to versatile biomaterials that afford controlled interactions with cells and tissues. Efficient synthesis of functionalizable polyesters is still a challenge that greatly limits the availability and widespread applications of biofunctionalized synthetic polymers. Here we report a simple route to prepare a functionalizable polyester, poly(sebacoyl diglyceride) (PSeD) bearing free hydroxyl groups. The key synthetic step is an epoxide ring-opening polymerization, instead of the traditional polycondensation, that produces poly(glycerol sebacate) (PGS) [1]. PSeD has a more defined structure with mostly linear backbone, more free hydroxyl groups, higher molecular weight, and lower polydispersity than PGS. Crosslinking PSeD with sebacic acid yields a polymer five times tougher and more elastic than cured PGS. PSeD exhibits good cytocompatibility in vitro. Furthermore, functionalization by glycine proceeds with high efficiency. This versatile synthetic platform can offer a large family of biodegradable, functionalized polymers with tunable physiochemical and biological properties useful for a wide range of biomedical applications. PMID:20149441

Phase behavior in quaternary ammonium ionic liquid-propanol solutions: Hydrophobicity, molecular conformations, and isomer effects

NASA Astrophysics Data System (ADS)

Abe, Hiroshi; Kohki, Erica; Nakada, Ayumu; Kishimura, Hiroaki

2017-07-01

In ionic liquids (ILs), the effects of a quaternary ammonium cation containing a hydroxyl group were investigated and compared with the effect of a standard quaternary ammonium cation. The cation possessing a hydroxyl group is choline, Chol+, and the anion is bis(trifluoromethylsulfonyl)imide, TFSI-. Crystal polymorphism of pure [Chol][TFSI] was observed upon both cooling and heating by simultaneous X-ray diffraction and differential scanning calorimetry measurements. In contrast, [N3111][TFSI] (N3111+: N-trimethyl-N-propylammonium), a standard IL, demonstrated simple crystallization upon cooling. By adding 1-propanol or 2-propanol, the phase behaviors of the [Chol][TFSI]-based and [N3111][TFSI]-based mixtures were clearly distinguished. By Raman spectroscopy, the TFSI- anion conformers in the liquid state were shown to vary according to the propanol concentration, propanol isomer, and type of cation. The anomalous behaviors of pure [Chol][TFSI] and its mixtures are derived from hydrogen bonding of the hydroxyl group of Chol+ cation coupled with the hydrophobicity and packing efficiency of propanol.

Radionuclide-binding compound, a radionuclide delivery system, a method of making a radium complexing compound, a method of extracting a radionuclide, and a method of delivering a radionuclide

DOEpatents

Fisher, Darrell R.; Wai, Chien M.; Chen, Xiaoyuan

2000-01-01

The invention pertains to compounds which specifically bind radionuclides, and to methods of making radionuclide complexing compounds. In one aspect, the invention includes a radionuclide delivery system comprising: a) a calix[n]arene-crown-[m]-ether compound, wherein n is an integer greater than 3, and wherein m is an integer greater than 3, the calix[n]arene-crown-[m]-ether compound comprising at least two ionizable groups; and b) an antibody attached to the calix[n]arene-crown-[m]-ether compound. In another aspect, the invention includes a method of making a radium complexing compound, comprising: a) providing a calix[n]arene compound, wherein n is an integer greater than 3, the calix[n]arene compound comprising n phenolic hydroxyl groups; b) providing a crown ether precursor, the crown ether precursor comprising a pair of tosylated ends; c) reacting the pair of tosylated ends with a pair of the phenolic hydroxyl groups to convert said pair of phenolic hydroxyl groups to ether linkages, the ether linkages connecting the crown ether precursor to the calix[n]arene to form a calix[n]arene-crown-[m]-ether compound, wherein m is an integer greater than 3; d) converting remaining phenolic hydroxyl groups to esters; e) converting the esters to acids, the acids being proximate a crown-[m]-ether portion of the calix[n]arene-crown-[m]-ether compound; and f) providing a Ra.sup.2+ ion within the crown-[m]-ether portion of the calix[n]arene-crown-[m]-ether compound.

High-value utilization of eucalyptus kraft lignin: Preparation and characterization as efficient dye dispersant.

PubMed

Zhang, Hui; Yu, Boming; Zhou, Wanpeng; Liu, Xinxin; Chen, Fangeng

2018-04-01

The dark color of industrial lignin is the main obstacle for their high value-added use in areas such as dyestuff dispersants. A kind of light-colored lignosulfonate with favorable dispersibility and remarkable stain resistance is prepared using fractionated eucalyptus kraft lignin. The fractionated lignins named as D (insoluble part) and X (soluble part) and sulfonated lignin fractions named as SD and SX are characterized by FTIR spectroscopy, 1 H NMR spectroscopy, GPC and brightness test. The results reveal that fraction X presents a lower molecular weight but a higher hydroxyl content than that of fraction D, which lead to the differences on the SO 3 H content, dispersibility and color performance of SD and SX. The sulfonated fractions perform a similar molecular weight to that of unsulfonated lignins and show light color due to the phenolic hydroxyl blocking of 1,4-BS (1,4-butane sultone) and the postprocessing of sodium borohydride. The SX that performs the best of all exhibits obvious decrease on phenolic hydroxyl groups and increase on brightness value which is improved by 85.8% compared with control sample. The SX reaches the highest level (grade 5) in the dispersibility test and presents remarkable stain resistance on different textiles, especially on the dacron and cotton. Copyright © 2017 Elsevier B.V. All rights reserved.

First principles calculations of interactions of ZrCl4 precursors with the bare and hydroxylated ZrO2 surfaces

NASA Astrophysics Data System (ADS)

Iskandarova, I. M.; Knizhnik, A. A.; Bagatur'yants, A. A.; Potapkin, B. V.; Korkin, A. A.

2004-05-01

First-principles calculations have been performed to determine the structures and relative energies of different zirconium chloride groups chemisorbed on the tetragonal ZrO2(001) surface and to study the effects of the surface coverage with metal chloride groups and the degree of hydroxylation on the adsorption energies of metal precursors. It is shown that the molecular and dissociative adsorption energies of the ZrCl4 precursor on the bare t-ZrO2(001) surface are too small to hold ZrCl4 molecules on the surface during an atomic layer deposition (ALD) cycle at temperatures higher than 300°C. On the contrary, it has been found that molecular adsorption on the fully hydroxylated zirconia surface leads to the formation of a stable adsorbed complex. This strong adsorption of ZrCl4 molecules can lead to a decrease in the film growth rate of the ALD process at lower temperatures (<200°C). The energies of interaction between adsorbed ZrCl4 groups at a 50% surface coverage has been found to be relatively small, which explains the maximum film growth rate observed in the ZrCl4:H2O ALD process. Moreover, we found that the adsorbed ZrCl4 precursors after hydrolysis give rise to very stable hydroxyl groups, which can be responsible for film growth at high temperatures (up to 900°C).

Effects of humic acids with different polarities on the photocatalytic activity of nano-TiO2 at environment relevant concentration.

PubMed

Wu, Wei; Shan, Guoqiang; Xiang, Qian; Zhang, Yinqing; Yi, Shujun; Zhu, Lingyan

2017-10-01

Large volume production and application of nano-TiO 2 make it inevitably release to natural waters and its environmental behaviors would be affected by natural organic matters. In this study, the mechanisms of humic acid (HA) affecting the photocatalytic performance of nano-TiO 2 were elucidated by using three HA fractions from the same source but with different polarities. Bulk HA was fractionated on a silica gel column to get three fractions with polarity increasing in the order of FA, FB and FC. FA was fulvic acid-like while FB and FC were humic acid-like. All the three fractions (at 0.1 mg/L) promoted the generation of hydroxyl radicals (OHs) by nano-TiO 2 , and thus in turn facilitated the photocatalytic degradation of bispheol A (BPA). FA and FC displayed a stronger promotion effect than FB and the bulk HA. Online in situ flow cell ATR-FTIR and XPS analyses indicated that HA fractions could form charge-transfer complex with nano-TiO 2 surface through the phenolic hydroxyl and carboxylic groups, which favored the separation of photogenerated electron-hole pairs. Through step methylation experiments, it was verified that the phenolic hydroxyl and carboxylic groups of HA fractions played important roles in promoting the photocatalytic performance of nano-TiO 2 , and the effect of carboxylic group was more significant than the phenolic hydroxyl group. Copyright © 2017 Elsevier Ltd. All rights reserved.

Ethyl 4-(4-hydroxy­phen­yl)-6-methyl-2-oxo-1,2,3,4-tetra­hydro­pyrimidine-5-carboxyl­ate monohydrate

PubMed Central

Das, Ushati; Chheda, Shardul B.; Pednekar, Suhas R.; Karambelkar, Narendra P; Guru Row, T. N.

2008-01-01

There are three formula units in the asymmetric unit of the title compound, C14H16N2O4·H2O. Mol­ecules are linked by N—H⋯O hydrogen bonds into dimers with the common R 2 2(8) graph-set motif. Between dimers, single N—H⋯O hydrogen bonds are formed between the other N—H group of each pyrimidine ring and the hydroxyl groups. The water mol­ecules accept O—H⋯O hydrogen bonds from the hydroxyl groups and donate hydrogen bonds to the ester groups. PMID:21581452

[Effect of the steroid molecule structure on the direction of its hydroxylation by the fungus Curvularia lunata].

PubMed

Andriushina, V A; Iaderets, V V; Stytsenko, T S; Druzhinina, A V; Voĭshvillo, N E

2013-01-01

The main and side products of hydroxylation by the C. lunata VKPM F-981 mycelium of fourteen delta(4)-3-ketosteroids of the estrane, androstane, and pregnane series and six of their delta(5)-3beta-hydroxy analogues were identified by H1 PMR spectroscopy and comparison with standard samples. The obtained experimental data are considered in terms of the triangular model of the enzyme-substrate interaction. The dependence of the direction of hydroxylation of steroid molecules and the orientation of hydroxy groups on the structure of the initial substrate was revealed.

Radical Polymerization of Diene Hydrocarbons in a Presence of Peroxide of Hydrogen and Solvent. 1. Effectiveness of Initiation and Rate of Expansion H2O2 during Oligomerization in Metallic Equipment

DTIC Science & Technology

1990-04-10

the hydroxyl groups. These are liquid oligobutadienes of brand R-15M and R-45M (firm "Sinclair Retgochemical Suc."/OSA) [5, 6, 10] and hydroxyl... ionic mechanism. Most promising, in view of simplicity and cheapness, is considered the I DOC - 90010000 PAGE - method of the radical polymerization of...Initiators of polimerization in this method are the hydroxyl radicals, which are generated during the homolytic decomposition of peroxide of hydrogen PDO

Molecular structure, functionality and applications of oxidized starches: A review.

PubMed

Vanier, Nathan Levien; El Halal, Shanise Lisie Mello; Dias, Alvaro Renato Guerra; da Rosa Zavareze, Elessandra

2017-04-15

During oxidation, the hydroxyl groups of starch molecules are first oxidized to carbonyl groups, then to carboxyl groups. The contents of the carbonyl and carboxyl groups in a starch molecule therefore indicate the extent of starch oxidation. The mechanisms of starch oxidation with different oxidizing agents, including sodium hypochlorite, hydrogen peroxide, ozone and sodium periodate, are described in this review. The effects of these oxidizing agents on the molecular, physicochemical, thermal, pasting and morphological properties of starch are described as well. In addition, the main industrial applications of oxidized starches are presented. The present review is important for understanding the effects of oxidation on starch properties, and this information may facilitate the development of novel oxidized starches for both food and non-food applications. Copyright © 2016 Elsevier Ltd. All rights reserved.

A delicate case of unidirectional proton transfer from water to an aromatic heterocyclic anion.

PubMed

Biswas, Sohag; Mallik, Bhabani S

2016-11-21

We present the characteristic proton transfer process from water to the pyrazole anion, infrared signatures of hydroxyl groups and the free energy profile of the process in aqueous solution combining first principles simulations, wavelet analysis and metadynamics. Our results show that the presence of minimum three water molecules in the gas phase cluster with a particular arrangement is sufficient to facilitate the proton transfer process from water to the anion. The overall reaction is very rapid in aqueous solution, and the free energy barrier for this process is found to be 4.2 kcal mol -1 . One of the earlier reported fundamental reasons for the transfer of proton from water to the anion is the change in the acidity of OH groups surrounding the anion. We have correlated the stretching frequencies of the surrounding OH groups with this acidity. We find that the development of less energetic vibrational states, and the OH mode having lowest average stretching frequency contains the most acidic proton. A large frequency shift of the OH mode belonging to one of the surrounding water molecules is observed during the transfer of proton from water to the anion; this shift is due to the change in acidity of the adjacent hydroxyl groups in the vicinity of the anion.

Sources and composition of submicron organic mass in marine aerosol particles

DOE PAGES

Frossard, Amanda A.; Russell, Lynn M.; Burrows, Susannah M.; ...

2014-11-27

Recent studies have proposed a variety of interpretations of the sources and composition of atmospheric marine aerosol particles (aMA) based on a range of physical and chemical measurements collected during open-ocean research cruises. To investigate the processes that affect marine organic particles, this study uses the characteristic functional group composition (from Fourier transform infrared (FTIR) spectroscopy) of aMAP from five ocean regions to show that: (i) The organic functional group composition of aMAP that can be identified as atmospheric primary marine (ocean-derived) aerosol (aPMA) is 65±12% hydroxyl, 21±9% alkane, 6±6% amine, and 7±8% carboxylic acid functional groups. Contributions from photochemicalmore » reactions add carboxylic acid groups (15%-25%), shipping effluent in seawater and ship emissions add additional alkane groups (up to 70%), and coastal emissions mix in alkane and carboxylic acid groups from coastal pollution sources. (ii) The organic composition of aPMA is nearly identical to model generated primary marine aerosol particles (gPMA) from bubbled seawater (55% hydroxyl, 32% alkane, and 13% amine functional groups), indicating that its overall functional group composition is the direct consequence of the organic constituents of the seawater source. (iii) While the seawater organic functional group composition was nearly invariant across all three ocean regions studied, the gPMA alkane group fraction increased with chlorophyll-a concentrations (r = 0.79). gPMA from productive seawater had a larger fraction of alkane functional groups (35%) compared to gPMA from non-productive seawater (16%), likely due to the presence of surfactants in productive seawater that stabilize the bubble film and lead to preferential drainage of the more soluble (lower alkane group fraction) organic components. gPMA has a hydroxyl group absorption peak location characteristic of monosaccharides and disaccharides, where the seawater OM hydroxyl group peak location is closer to that of polysaccharides. This may result from the larger saccharides preferentially remaining in the seawater during gPMA and aPMA production« less

Sources and composition of submicron organic mass in marine aerosol particles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Frossard, Amanda A.; Russell, Lynn M.; Burrows, Susannah M.

Recent studies have proposed a variety of interpretations of the sources and composition of atmospheric marine aerosol particles (aMA) based on a range of physical and chemical measurements collected during open-ocean research cruises. To investigate the processes that affect marine organic particles, this study uses the characteristic functional group composition (from Fourier transform infrared (FTIR) spectroscopy) of aMAP from five ocean regions to show that: (i) The organic functional group composition of aMAP that can be identified as atmospheric primary marine (ocean-derived) aerosol (aPMA) is 65±12% hydroxyl, 21±9% alkane, 6±6% amine, and 7±8% carboxylic acid functional groups. Contributions from photochemicalmore » reactions add carboxylic acid groups (15%-25%), shipping effluent in seawater and ship emissions add additional alkane groups (up to 70%), and coastal emissions mix in alkane and carboxylic acid groups from coastal pollution sources. (ii) The organic composition of aPMA is nearly identical to model generated primary marine aerosol particles (gPMA) from bubbled seawater (55% hydroxyl, 32% alkane, and 13% amine functional groups), indicating that its overall functional group composition is the direct consequence of the organic constituents of the seawater source. (iii) While the seawater organic functional group composition was nearly invariant across all three ocean regions studied, the gPMA alkane group fraction increased with chlorophyll-a concentrations (r = 0.79). gPMA from productive seawater had a larger fraction of alkane functional groups (35%) compared to gPMA from non-productive seawater (16%), likely due to the presence of surfactants in productive seawater that stabilize the bubble film and lead to preferential drainage of the more soluble (lower alkane group fraction) organic components. gPMA has a hydroxyl group absorption peak location characteristic of monosaccharides and disaccharides, where the seawater OM hydroxyl group peak location is closer to that of polysaccharides. This may result from the larger saccharides preferentially remaining in the seawater during gPMA and aPMA production« less

Sources and composition of submicron organic mass in marine aerosol particles

NASA Astrophysics Data System (ADS)

Frossard, Amanda A.; Russell, Lynn M.; Burrows, Susannah M.; Elliott, Scott M.; Bates, Timothy S.; Quinn, Patricia K.

2014-11-01

The sources and composition of atmospheric marine aerosol particles (aMA) have been investigated with a range of physical and chemical measurements from open-ocean research cruises. This study uses the characteristic functional group composition (from Fourier transform infrared spectroscopy) of aMA from five ocean regions to show the following: (i) The organic functional group composition of aMA that can be identified as mainly atmospheric primary marine (ocean derived) aerosol particles (aPMA) is 65 ± 12% hydroxyl, 21 ± 9% alkane, 6 ± 6% amine, and 7 ± 8% carboxylic acid functional groups. Contributions from photochemical reactions add carboxylic acid groups (15%-25%), shipping effluent in seawater and ship emissions add additional alkane groups (up to 70%), and coastal or continental emissions mix in alkane and carboxylic acid groups. (ii) The organic composition of aPMA is nearly identical to model-generated primary marine aerosol particles from bubbled seawater (gPMA, which has 55 ± 14% hydroxyl, 32 ± 14% alkane, and 13 ± 3% amine functional groups), indicating that its overall functional group composition is the direct consequence of the organic constituents of the seawater source. (iii) While the seawater organic functional group composition was nearly invariant across all three ocean regions studied and the ratio of organic carbon to sodium (OC/Na+) in the gPMA remained nearly constant over a broad range of chlorophyll a concentrations, the gPMA alkane group fraction appeared to increase with chlorophyll a concentrations (r = 0.66). gPMA from productive seawater had a larger fraction of alkane functional groups (42 ± 9%) compared to gPMA from nonproductive seawater (22 ± 10%), perhaps due to the presence of surfactants in productive seawater that stabilize the bubble film and lead to preferential drainage of the more soluble (lower alkane group fraction) organic components. gPMA has a hydroxyl group absorption peak location characteristic of monosaccharides and disaccharides, where the seawater organic mass hydroxyl group peak location is closer to that of polysaccharides. This may result from the larger saccharides preferentially remaining in the seawater during gPMA and aPMA production.

Development of fluorescent probes based on protection-deprotection of the key functional groups for biological imaging.

PubMed

Tang, Yonghe; Lee, Dayoung; Wang, Jiaoliang; Li, Guanhan; Yu, Jinghua; Lin, Weiying; Yoon, Juyoung

2015-08-07

Recently, the strategy of protection-deprotection of functional groups has been widely employed to design fluorescent probes, as the protection-deprotection of functional groups often induces a marked change in electronic properties. Significant advances have been made in the development of analyte-responsive fluorescent probes based on the protection-deprotection strategy. In this tutorial review, we highlight the representative examples of small-molecule based fluorescent probes for bioimaging, which are operated via the protection-deprotection of key functional groups such as aldehyde, hydroxyl, and amino functional groups reported from 2010 to 2014. The discussion includes the general protection-deprotection methods for aldehyde, hydroxyl, or amino groups, as well as the design strategies, sensing mechanisms, and deprotection modes of the representative fluorescent imaging probes applied to bio-imaging.

Tannin structural elucidation and quantitative ³¹P NMR analysis. 2. Hydrolyzable tannins and proanthocyanidins.

PubMed

Melone, Federica; Saladino, Raffaele; Lange, Heiko; Crestini, Claudia

2013-10-02

An unprecedented analytical method that allows simultaneous structural and quantitative characterization of all functional groups present in tannins is reported. In situ labeling of all labile H groups (aliphatic and phenolic hydroxyls and carboxylic acids) with a phosphorus-containing reagent (Cl-TMDP) followed by quantitative ³¹P NMR acquisition constitutes a novel fast and reliable analytical tool for the analysis of tannins and proanthocyanidins with significant implications for the fields of food and feed analyses, tannery, and the development of natural polyphenolics containing products.

Identifying organic aerosol sources by comparing functional group composition in chamber and atmospheric particles

PubMed Central

Russell, Lynn M.; Bahadur, Ranjit; Ziemann, Paul J.

2011-01-01

Measurements of submicron particles by Fourier transform infrared spectroscopy in 14 campaigns in North America, Asia, South America, and Europe were used to identify characteristic organic functional group compositions of fuel combustion, terrestrial vegetation, and ocean bubble bursting sources, each of which often accounts for more than a third of organic mass (OM), and some of which is secondary organic aerosol (SOA) from gas-phase precursors. The majority of the OM consists of alkane, carboxylic acid, hydroxyl, and carbonyl groups. The organic functional groups formed from combustion and vegetation emissions are similar to the secondary products identified in chamber studies. The near absence of carbonyl groups in the observed SOA associated with combustion is consistent with alkane rather than aromatic precursors, and the absence of organonitrate groups can be explained by their hydrolysis in humid ambient conditions. The remote forest observations have ratios of carboxylic acid, organic hydroxyl, and nonacid carbonyl groups similar to those observed for isoprene and monoterpene chamber studies, but in biogenic aerosols transported downwind of urban areas the formation of esters replaces the acid and hydroxyl groups and leaves only nonacid carbonyl groups. The carbonyl groups in SOA associated with vegetation emissions provides striking evidence for the mechanism of esterification as the pathway for possible oligomerization reactions in the atmosphere. Forest fires include biogenic emissions that produce SOA with organic components similar to isoprene and monoterpene chamber studies, also resulting in nonacid carbonyl groups in SOA. PMID:21317360

Probing the surface of γ-Al2O3 by oxygen-17 dynamic nuclear polarization enhanced solid-state NMR spectroscopy.

PubMed

Li, Wenzheng; Wang, Qiang; Xu, Jun; Aussenac, Fabien; Qi, Guodong; Zhao, Xingling; Gao, Pan; Wang, Chao; Deng, Feng

2018-06-14

γ-Al2O3 is an important catalyst and catalyst support of industrial interest. Its acid/base characteristics are correlated to the surface structure, which has always been an issue of concern. In this work, the complex (sub-)surface oxygen species on surface-selectively labelled γ-Al2O3 were probed by 17O dynamic nuclear polarization surface-enhanced NMR spectroscopy (DNP-SENS). Direct 17O MAS and indirect 1H-17O cross-polarization (CP)/MAS DNP experiments enable observation of the (sub-)surface bare oxygen species and hydroxyl groups. In particular, a two-dimensional (2D) 17O 3QMAS DNP spectrum was for the first time achieved for γ-Al2O3, in which two O(Al)4 and one O(Al)3 bare oxygen species were identified. The 17O isotropic chemical shifts (δcs) vary from 56.7 to 81.0 ppm and the quadrupolar coupling constants (CQ) range from 0.6 to 2.5 MHz for the three oxygen species. The coordinatively unsaturated O(Al)3 species is characterized by a higher field chemical shift (56.7 ppm) and the largest CQ value (2.5 MHz) among these oxygen sites. 2D 1H → 17O HETCOR DNP experiments allow us to discriminate three bridging (Aln)-μ2-OH and two terminal (Aln)-μ1-OH hydroxyl groups. The structural features of the bare oxygen species and hydroxyl groups are similar for the γ-Al2O3 samples isotopically labelled by 17O2 gas or H217O. The results presented here show that the combination of surface-selective labelling and DNP-SENS is an effective approach for characterizing oxides with complex surface species.

The Juxtaposition of Ribose Hydroxyl Groups: The Root of Biological Catalysis and the RNA World?

NASA Astrophysics Data System (ADS)

Bernhardt, Harold S.

2015-06-01

We normally think of enzymes as being proteins; however, the RNA world hypothesis suggests that the earliest biological catalysts may have been composed of RNA. One of the oldest surviving RNA enzymes we are aware of is the peptidyl transferase centre (PTC) of the large ribosomal RNA, which joins amino acids together to form proteins. Recent evidence indicates that the enzymatic activity of the PTC is principally due to ribose 2 '-OHs. Many other reactions catalyzed by RNA and/or in which RNA is a substrate similarly utilize ribose 2 '-OHs, including phosphoryl transfer reactions that involve the cleavage and/or ligation of the ribose-phosphate backbone. It has recently been proposed by Yakhnin (2013) that phosphoryl transfer reactions were important in the prebiotic chemical evolution of RNA, by enabling macromolecules composed of polyols joined by phosphodiester linkages to undergo recombination reactions, with the reaction energy supplied by the phosphodiester bond itself. The almost unique juxtaposition of the ribose 2'-hydroxyl and 3'-oxygen in ribose-containing polymers such as RNA, which gives ribose the ability to catalyze such reactions, may have been an important factor in the selection of ribose as a component of the first biopolymer. In addition, the juxtaposition of hydroxyl groups in free ribose: (i) allows coordination of borate ions, which could have provided significant and preferential stabilization of ribose in a prebiotic environment; and (ii) enhances the rate of permeation by ribose into a variety of lipid membrane systems, possibly favouring its incorporation into early metabolic pathways and an ancestral ribose-phosphate polymer. Somewhat more speculatively, hydrogen bonds formed by juxtaposed ribose hydroxyl groups may have stabilized an ancestral ribose-phosphate polymer against degradation (Bernhardt and Sandwick 2014). I propose that the almost unique juxtaposition of ribose hydroxyl groups constitutes the root of both biological catalysis and the RNA world.

Photodynamic activity of pyropheophorbide methyl ester and pyropheophorbide a in dimethylformamide solution.

PubMed

Al-Omari, Saleh; Ali, Ahmad

2009-03-01

Comparative spectroscopic study including the photosensitizers of pyropheophorbide methyl ester (PPME) and pyropheophorbide a (PPa) was performed to study their photodynamic activity. The investigated photosensitizers in a homogeneous system of dimethylformamide (DMF) are not photostable upon irradiation. The photobleaching efficiency of PPa is higher than that of PPME. Combining these results with the data obtained by measuring the singlet oxygen quantum yield and the hydroxyl group generation, it was revealed that the photobleaching efficiency could be correlated with the singlet oxygen quantum yield and the hydroxyl group production of the photosensitizer.

Molecular Hydrogen Formation from Proximal Glycol Pairs on TiO2(110)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Long; Li, Zhenjun; Smith, R. Scott

2014-04-16

Understanding hydrogen formation on TiO2 surfaces is of great importance as it could provide fundamental insight into water splitting for hydrogen production using solar energy. In this work, hydrogen formation from glycols having different numbers of methyl end-groups have been studied using temperature pro-grammed desorption on reduced, hydroxylated, and oxidized TiO2(110) surfaces. The results from OD-labeled glycols demon-strate that gas-phase molecular hydrogen originates exclusively from glycol hydroxyl groups. The yield is controlled by a combi-nation of glycol coverage, steric hindrance, TiO2(110) order and the amount of subsurface charge. Combined, these results show that proximal pairs of hydroxyl aligned glycol moleculesmore » and subsurface charge are required to maximize the yield of this redox reaction. These findings highlight the importance of geometric and electronic effects in hydrogen formation from adsorbates on TiO2(110).« less

Spectral Response and Diagnostics of Biological Activity of Hydroxyl-Containing Aromatic Compounds

NASA Astrophysics Data System (ADS)

Tolstorozhev, G. B.; Mayer, G. V.; Bel'kov, M. V.; Shadyro, O. I.

2016-08-01

Using IR Fourier spectra and employing quantum-chemical calculations of electronic structure, spectra, and proton-acceptor properties, synthetic derivatives of aminophenol exhibiting biological activity in the suppression of herpes, influenza, and HIV viruses have been investigated from a new perspective, with the aim of establishing the spectral response of biological activity of the molecules. It has been experimentally established that the participation of the aminophenol hydroxyl group in intramolecular hydrogen bonds is characteristic of structures with antiviral properties. A quantum-chemical calculation of the proton-acceptor ability of the investigated aminophenol derivatives has shown that biologically active structures are characterized by a high proton-acceptor ability of oxygen of the hydroxyl group. A correlation that has been obtained among the formation of an intramolecular hydrogen bond, high proton-acceptor ability, and antiviral activity of substituted aminophenols enables us to predict the pharmacological properties of new medical preparations of the given class of compounds.

Interactions of Kraft lignin and wheat gluten during biomaterial processing: evidence for the role of phenolic groups.

PubMed

Kaewtatip, Kaewta; Menut, Paul; Auvergne, Remi; Tanrattanakul, Varaporn; Morel, Marie-Helene; Guilbert, Stephane

2010-04-14

The chemical interactions between Kraft lignin and wheat gluten under processing conditions were investigated by determining the extent of the protein network formation. To clarify the role of different chemical functions found in lignin, the effect of Kraft lignin was compared with that of an esterified lignin, in which hydroxyl groups had been suppressed by esterification, and with a series of simple aromatics and phenolic structures with different functionalities (conjugated double bonds, hydroxyl, carboxylic acid, and aldehyde). The protein solubility was determined by using the Kjeldahl method. The role of the hydroxyl function was assessed by the significantly lower effect of esterified lignin. The importance of the phenolic radical scavenging structure is evidenced by the effect of guaiacol, which results in a behavior similar to that of the Kraft lignin. In addition, the significant effect of conjugated double bonds on gluten reactivity, through nucleophilic addition, was demonstrated.

Potential benefits of triethylamine as n-electron donor in the estimation of forskolin by electronic absorption and emission spectroscopy.

PubMed

Raju, Gajula; Ram Reddy, A

2016-02-05

Diterpenoid forskolin was isolated from Coleus forskolii. The electronic absorption and emission studies of forskolin were investigated in various solvents with an aim to improve its detection limits. The two chromophores present in the diterpenoid are not conjugated leading to the poor absorption and emission of UV light. The absorption and fluorescence spectra were solvent specific. In the presence of a monodentate ligand, triethylamine the detection of forskolin is improved by 3.63 times in ethanol with the fluorescence method and 3.36 times in DMSO by the absorption spectral method. The longer wavelength absorption maximum is blue shifted while the lower energy fluorescence maximum is red shifted in the presence of triethylamine. From the wavelength of fluorescence maxima of the exciplex formed between excited forskolin and triethylamine it is concluded that the order of reactivity of hydroxyl groups in the excited state forskolin is in the reverse order to that of the order of the reactivity of hydroxyl groups in its ground state. Copyright © 2015. Published by Elsevier B.V.

AlNbO oxides as new supports for hydrocarbon oxidation II. Catalytic properties of VO sub x -grafted AlNbO oxides

DOE Office of Scientific and Technical Information (OSTI.GOV)

Oliveira, P.G. Pries de; Eon, J.G.; Volta, J.C.

1992-09-01

Vanadium oxides were immobilized by grafting VOCl{sub 3} on AlNbO oxides calcined between 500 and 750 C. Chemical analysis, XPS, and STEM measurements suggest an incomplete but homogeneous stoichiometric reaction between superficial hydroxyl groups and vanadyl oxychloride. By FTIR studies, it is observed that the interaction involves preferentially basic hydroxyl groups bonded to aluminium cations. UV-visible spectra show that mainly V{sup 5+} is present at the solid surface. Corresponding spectra are compatible with tetrahedral symmetry, in agreement with a previous {sup 51}V NMR investigation. The acido-basic properties of the catalyst were tested by isopropanol decomposition and compared with the correspondingmore » supports. It has been observed that basicity is higher for VO{sub x} grafted on AlBnO oxide calcined at high temperature and corresponding to the AlNbO{sub 4} structure. VO{sub x} grafted on AlNbO oxides calcined at intermediate temperatures and corresponding to a AlNbO disorganized structure present a good selectivity for the oxidative dehydrogenation of propane into propene. It has been observed that, for both reactions, the turnover number increases with the temperature of calcination of the catalysts. The reactivity of the aluminium niobiate support.« less

Effect of acetylated wood flour or coupling agent on moisture, UV, and biological resistance of extruded woodfiber-plastic composites

Treesearch

Rebecca E. Ibach; Craig M. Clemons

2006-01-01

Although moisture sorption in woodfiber-thermoplastic composites (WPCs) is slower than in unmodified solid wood, it still affects strength and ultimately results in decay of the material in moist outdoor exposure conditions. Chemical modification of the hydroxyl groups of wood with acetic anhydride esterifies the hydroxyl making the wood more hydrophobic and...

Investigation of Water Dissociation and Surface Hydroxyl Stability on Pure and Ni-Modified CoOOH by Ambient Pressure Photoelectron Spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Zhu; Kronawitter, Coleman X.; Waluyo, Iradwikanari

Water adsorption and reaction on pure and Ni-modified CoOOH nanowires were investigated using ambient pressure photoemission spectroscopy (APPES). The unique capabilities of APPES enable us to observe water dissociation and monitor formation of surface species on pure and Ni-modified CoOOH under elevated pressures and temperatures for the first time. Over a large range of pressures (UHV to 1 Torr), water dissociates readily on the pure and Ni-modified CoOOH surfaces at 27 °C. With an increase in H 2O pressure, a greater degree of surface hydroxylation was observed for all samples. At 1 Torr H 2O, ratios of different oxygen speciesmore » indicate a transformation of CoOOH to CoO xH y in pure and Ni-modified CoOOH. In temperature dependent studies, desorption of weakly bound water and surface dehydroxylation were observed with increasing temperature. In conclusion, larger percentages of surface hydroxyl groups at higher temperatures were observed on Ni-modified CoOOH compared to pure CoOOH, which indicates an increased stability of surface hydroxyl groups on these Ni-modified surfaces.« less

Investigation of Water Dissociation and Surface Hydroxyl Stability on Pure and Ni-Modified CoOOH by Ambient Pressure Photoelectron Spectroscopy

DOE PAGES

Chen, Zhu; Kronawitter, Coleman X.; Waluyo, Iradwikanari; ...

2017-09-07

Water adsorption and reaction on pure and Ni-modified CoOOH nanowires were investigated using ambient pressure photoemission spectroscopy (APPES). The unique capabilities of APPES enable us to observe water dissociation and monitor formation of surface species on pure and Ni-modified CoOOH under elevated pressures and temperatures for the first time. Over a large range of pressures (UHV to 1 Torr), water dissociates readily on the pure and Ni-modified CoOOH surfaces at 27 °C. With an increase in H 2O pressure, a greater degree of surface hydroxylation was observed for all samples. At 1 Torr H 2O, ratios of different oxygen speciesmore » indicate a transformation of CoOOH to CoO xH y in pure and Ni-modified CoOOH. In temperature dependent studies, desorption of weakly bound water and surface dehydroxylation were observed with increasing temperature. In conclusion, larger percentages of surface hydroxyl groups at higher temperatures were observed on Ni-modified CoOOH compared to pure CoOOH, which indicates an increased stability of surface hydroxyl groups on these Ni-modified surfaces.« less

Copper removal by algal biomass: biosorbents characterization and equilibrium modelling.

PubMed

Vilar, Vítor J P; Botelho, Cidália M S; Pinheiro, José P S; Domingos, Rute F; Boaventura, Rui A R

2009-04-30

The general principles of Cu(II) binding to algal waste from agar extraction, composite material and algae Gelidium, and different modelling approaches, are discussed. FTIR analyses provided a detailed description of the possible binding groups present in the biosorbents, as carboxylic groups (D-glucuronic and pyruvic acids), hydroxyl groups (cellulose, agar and floridean starch) and sulfonate groups (sulphated galactans). Potentiometric acid-base titrations showed a heterogeneous distribution of two major binding groups, carboxyl and hydroxyl, following the quasi-Gaussian affinity constant distribution suggested by Sips, which permitted to estimate the maximum amount of acid functional groups (0.36, 0.25 and 0.1 mmol g(-1)) and proton binding parameters (pK(H)=5.0, 5.3 and 4.4; m(H)=0.43, 0.37, 0.33), respectively for algae Gelidium, algal waste and composite material. A non-ideal, semi-empirical, thermodynamically consistent (NICCA) isotherm fitted better the experimental ion binding data for different pH values and copper concentrations, considering only the acid functional groups, than the discrete model. Values of pK(M) (3.2; 3.6 and 3.3), n(M) (0.98, 0.91, 1.0) and p (0.67, 0.53 and 0.43) were obtained, respectively for algae Gelidium, algal waste and composite material. NICCA model reflects the complex macromolecular systems that take part in biosorption considering the heterogeneity of the biosorbent, the competition between protons and metals ions to the binding sites and the stoichiometry for different ions.

Influence of Various Phenolic Compounds on Properties of Gelatin Film Prepared from Horse Mackerel Trachurus japonicus Scales.

PubMed

Le, Thuy; Maki, Hiroki; Okazaki, Emiko; Osako, Kazufumi; Takahashi, Kigen

2018-06-15

Influence of various phenolic compounds on physical properties and antioxidant activity of gelatin film from horse mackerel Trachurus japonicus scales was investigated. Tensile strength (TS) of the film was enhanced whereas elongation at break was declined by adding 1% to 5% phenolic compounds. Rutin was the most effective to improve the TS compared to the other tested phenolic compounds including ferulic acid, caffeic acid, gallic acid, and catechin. Gelatin films with the phenolic compounds showed the excellent UV barrier properties. FTIR spectra exhibited that wavenumber of amide-A band of films decreased with formation of hydrogen bonding between amino groups of gelatin and hydroxyl groups of the phenolic compounds. Gelatin film incorporated with rutin which has the largest number of hydroxyl groups among the tested compounds demonstrated the lowest wavenumber for the amide-A peak. It is indicated that hydroxyl groups contained in the phenolic compounds contribute to formation of hydrogen bonds involved in improvement of the mechanical properties of the films. The incorporation of the phenolic compounds with gelatin films also led to the increasing of total phenolic contents and DPPH radical scavenging activities. Thus, it is concluded that phenolic compounds can promote the quality of gelatin film. Properties of gelatin film derived from horse mackerel scales can be improved by adding of phenolic compounds. Phenolic compounds containing a large number of hydroxyl groups should be selected to enhance physical properties of the gelatin film. A biodegradable film prepared from horse mackerel gelatin incorporated with phenolic compounds, which has good physical properties and antioxidant properties, can solve environmental problems caused by synthetic plastic materials. © 2018 Institute of Food Technologists®.

Protective effect of D-002, a mixture of beeswax alcohols, against indomethacin-induced gastric ulcers and mechanism of action.

PubMed

Pérez, Yohani; Oyárzabal, Ambar; Mas, Rosa; Molina, Vivian; Jiménez, Sonia

2013-01-01

D-002, a mixture of higher aliphatic beeswax alcohols, produces gastroprotective and antioxidant effects. To investigate the gastroprotective effect of D-002 against indomethacin-induced ulcers, oxidative variables and myeloperoxidase (MPO) activity in the rat gastric mucosa were examined. Rats were randomized into six groups: a negative vehicle control and five indomethacin (50 mg/kg) treated groups, comprising a positive control, three groups treated orally with D-002 (5, 25 and 100 mg/kg) and one group with omeprazole 20 mg/kg intraperitoneally (ip). The contents of malondialdehyde (MDA), protein carbonyl groups (PCG), hydroxyl radical generation and catalase (CAT), glutathione peroxidase (GSH-PX), superoxide dismutase (SOD) and MPO enzyme activities in the rat gastric mucosa were assessed. Indomethacin increased the content of MDA and PCG, the generation of *OH radical and MPO enzyme activity, while it decreased the CAT, GSH-PX and SOD activities as compared to the negative controls. D-002 (5-100 mg/kg) significantly and dose-dependently reduced indomethacin-induced ulceration to 75 %. Also, D-002 decreased the content of MDA and PCG, the generation of hydroxyl radicals and MPO activity as compared to the positive controls. The highest dose of D-002 (100 mg/kg) increased significantly GSH-PX and SOD activities, while all doses used increased CAT activities. Omeprazole 20 mg/kg, the reference drug, reduced significantly the ulcers (93 %), MDA and PCG, the generation of hydroxyl radicals and MPO activity, and increased the CAT, GSH-PX and SOD activities. D-002 treatment produced gastroprotective effects against indomethacin-induced gastric ulceration, which can be related to the reduction of hydroxyl radical generation, lipid peroxidation, protein oxidation and MPO activity, and to the increase of the antioxidant enzymes activities in the rat gastric mucosa.

Ferricyanide-based analysis of aqueous lignin suspension revealed sequestration of water-soluble lignin moieties

DOE Office of Scientific and Technical Information (OSTI.GOV)

Joshua, C. J.; Simmons, B. A.; Singer, S. W.

This study describes the application of a ferricyanide-based assay as a simple and inexpensive assay for rapid analysis of aqueous lignin samples. The assay measures the formation of Prussian blue from the redox reaction between a mixture of potassium ferricyanide and ferric chloride, and phenolic hydroxyl groups of lignin or lignin-derived phenolic moieties. This study revealed that soluble lignin moieties exhibited stronger ferricyanide reactivity than insoluble aggregates. The soluble lignin moieties exhibited higher ferricyanide reactivity because of increased access of the phenolic hydroxyl groups to the ferricyanide reagents. Ferricyanide reactivity of soluble lignin moieties correlated inversely with the molecular weightmore » distributions of the molecules, probably due to the involvement of phenolic hydroxyl groups in bond formation. The insoluble lignin aggregates exhibited low ferricyanide reactivity due to sequestration of the phenolic hydroxyl groups within the solid matrix. The study also highlighted the sequestration of polydispersed water-soluble lignin moieties by insoluble aggregates. The sequestered moieties were released by treatment with 0.01 M NaOH at 37 °C for 180 min. The redox assay was effective on different types of lignin extracts such as Klason lignin from switchgrass, ionic-liquid derived lignin from Eucalyptus and alkali lignin extracts. The assay generated a distinct profile for each lignin sample that was highly reproducible. The assay was also used to monitor consumption of syringic acid by Sphingobium sp. SYK-6. The simplicity and reproducibility of this assay makes it an excellent and versatile tool for qualitative and semi-quantitative characterization and comparative profiling of aqueous lignin samples.« less

Ferricyanide-based analysis of aqueous lignin suspension revealed sequestration of water-soluble lignin moieties

DOE PAGES

Joshua, C. J.; Simmons, B. A.; Singer, S. W.

2016-06-02

This study describes the application of a ferricyanide-based assay as a simple and inexpensive assay for rapid analysis of aqueous lignin samples. The assay measures the formation of Prussian blue from the redox reaction between a mixture of potassium ferricyanide and ferric chloride, and phenolic hydroxyl groups of lignin or lignin-derived phenolic moieties. This study revealed that soluble lignin moieties exhibited stronger ferricyanide reactivity than insoluble aggregates. The soluble lignin moieties exhibited higher ferricyanide reactivity because of increased access of the phenolic hydroxyl groups to the ferricyanide reagents. Ferricyanide reactivity of soluble lignin moieties correlated inversely with the molecular weightmore » distributions of the molecules, probably due to the involvement of phenolic hydroxyl groups in bond formation. The insoluble lignin aggregates exhibited low ferricyanide reactivity due to sequestration of the phenolic hydroxyl groups within the solid matrix. The study also highlighted the sequestration of polydispersed water-soluble lignin moieties by insoluble aggregates. The sequestered moieties were released by treatment with 0.01 M NaOH at 37 °C for 180 min. The redox assay was effective on different types of lignin extracts such as Klason lignin from switchgrass, ionic-liquid derived lignin from Eucalyptus and alkali lignin extracts. The assay generated a distinct profile for each lignin sample that was highly reproducible. The assay was also used to monitor consumption of syringic acid by Sphingobium sp. SYK-6. The simplicity and reproducibility of this assay makes it an excellent and versatile tool for qualitative and semi-quantitative characterization and comparative profiling of aqueous lignin samples.« less

Glycerol dehydratation by the B12-independent enzyme may not involve the migration of a hydroxyl group: a computational study.

PubMed

Feliks, Mikolaj; Ullmann, G Matthias

2012-06-21

A combination of continuum electrostatic and density functional calculations has been employed to study the mechanism of the B(12)-independent glycerol dehydratase, a novel glycyl-radical enzyme involved in the microbial conversion of glycerol to 3-hydroxylpropionaldehyde. The calculations indicate that the dehydratation of glycerol by the B(12)-independent enzyme does not need to involve a mechanistically complicated migration of the middle hydroxyl group to one of the two terminal positions of a molecule, as previously suggested. Instead, the reaction can proceed in three elementary steps. First, a radical transfer from the catalytically active Cys433 to the ligand generates a substrate-related intermediate. Second, a hydroxyl group splits off at the middle position of the ligand and is protonated by the neighboring His164 to form a water molecule. The other active site residue Glu435 accepts a proton from one of the terminal hydroxyl groups of the ligand and a C═O double bond is created. Third, the reaction is completed by a radical back transfer from the product-related intermediate to Cys433. On the basis of our calculations, the catalytic functions of the active site residues have been suggested. Cys433 is a radical relay site; His164 and Glu435 make up a proton accepting/donating system; Asn156, His281, and Asp447 form a network of hydrogen bonds responsible for the electrostatic stabilization of the transition state. A synergistic participation of these residues in the reaction seems to be crucial for the catalysis.

Structural insight into the active site of mushroom tyrosinase using phenylbenzoic acid derivatives.

PubMed

Oyama, Takahiro; Yoshimori, Atsushi; Takahashi, Satoshi; Yamamoto, Tetsuya; Sato, Akira; Kamiya, Takanori; Abe, Hideaki; Abe, Takehiko; Tanuma, Sei-Ichi

2017-07-01

So far, many inhibitors of tyrosinase have been discovered for cosmetic and clinical agents. However, the molecular mechanisms underlying the inhibition in the active site of tyrosinase have not been well understood. To explore this problem, we examined here the inhibitory effects of 4'-hydroxylation and methoxylation of phenylbenzoic acid (PBA) isomers, which have a unique scaffold to inhibit mushroom tyrosinase. The inhibitory effect of 3-PBA, which has the most potent inhibitory activity among the isomers, was slightly decreased by 4'-hydroxylation and further decreased by 4'-methoxylation against mushroom tyrosinase. Surprisingly, 4'-hydroxylation but not methoxylation of 2-PBA appeared inhibitory activity. On the other hand, both 4'-hydroxylation and methoxylation of 4-PBA increased the inhibitory activity against mushroom tyrosinase. In silico docking analyses using the crystallographic structure of mushroom tyrosinase indicated that the carboxylic acid or 4'-hydroxyl group of PBA derivatives could chelate with cupric ions in the active site of mushroom tyrosinase, and that the interactions of Asn260 and Phe264 in the active site with the adequate-angled biphenyl group are involved in the inhibitory activities of the modified PBAs, by parallel and T-shaped π-π interactions, respectively. Furthermore, Arg268 could fix the angle of the aromatic ring of Phe264, and Val248 is supposed to interact with the inhibitors as a hydrophobic manner. These results may enhance the structural insight into mushroom tyrosinase for the creation of novel tyrosinase inhibitors. Copyright © 2017 Elsevier Ltd. All rights reserved.

RNA Structural Analysis by Evolving SHAPE Chemistry

PubMed Central

Spitale, Robert C.; Flynn, Ryan A.; Torre, Eduardo A.; Kool, Eric T.; Chang, Howard Y.

2017-01-01

RNA is central to the flow of biological information. From transcription to splicing, RNA localization, translation, and decay, RNA is intimately involved in regulating every step of the gene expression program, and is thus essential for health and understanding disease. RNA has the unique ability to base-pair with itself and other nucleic acids to form complex structures. Hence the information content in RNA is not simply its linear sequence of bases, but is also encoded in complex folding of RNA molecules. A general chemical functionality that all RNAs have is a 2’-hydroxyl group in the ribose ring, and the reactivity of the 2'-hydroxyl in RNA is gated by local nucleotide flexibility. In other words, the 2'-hydroxyl is reactive at single-stranded and conformationally flexible positions but is unreactive at nucleotides constrained by base pairing. Recent efforts have been focused on developing reagents that modify RNA as a function of RNA 2’ hydroxyl group flexibility. Such RNA structure probing techniques can be read out by primer extension in experiments termed RNA SHAPE (Selective 2’ Hydroxyl Acylation and Primer Extension). Herein we describe the efforts devoted to the design and utilization of SHAPE probes for characterizing RNA structure. We also describe current technological advances that are being used to utilize SHAPE chemistry with deep sequencing to probe many RNAs in parallel. The merger of chemistry with genomics is sure to open the door to genome-wide exploration of RNA structure and function. PMID:25132067

Synthesis and characterization of a novel bio-based resin from maleated soybean oil polyols

NASA Astrophysics Data System (ADS)

Li, Y. T.; Yang, L. T.; Zhang, H.

2017-02-01

In this paper, a novel bio-based resin was prepared by the radical copolymerization of maleated soybean oil polyols (MSBOP) and styrene (ST). Structure of the product was studied by Fourier transformation infrared spectrometer (FT-IR), and the result was found to be consistent with that of theoretical structure. Swelling experiments indicated that the crosslinking degree increased with the increase of hydroxyl value. Thermal analysis by differential scanning calorimetry (DSC) and thermo-gravimetric analysis (TG) revealed that glass transition temperature (Tg) of the polymer increased with increasing hydroxyl values, and that its thermal stability showed a good correlation with the hydroxyl value. The tensile strength and impact strength were significantly affected by the hydroxyl value of soybean oil polyols. With increasing hydroxyl value, the tensile strength presented an increasing trend, while the impact strength showed a decreasing one. Moreover, the property of the polymer from elastomer to plastic character also depended on the functionality of the hydroxyl value of soybean oil polyols.

Selective aminolysis of acetylated lignin: Toward simultaneously improving thermal-oxidative stability and maintaining mechanical properties of polypropylene.

PubMed

Ye, Dezhan; Kong, Jinfeng; Gu, Shaojin; Zhou, Yingshan; Huang, Caoxing; Xu, Weilin; Zhang, Xi

2018-03-01

Even with outstanding radical capturing ability, the utilization of lignin as a natural antioxidant in polypropylene (PP) still has been pended. Usually, the compatibility of its blends is improved based on the reaction of hydroxyl content, thus leading to the decreasing content of phenolic hydroxyl (Ph-OH) group and inferior thermal-oxidative stability of lignin blends. Here, the selective aminolysis of acetylated Kraft lignin (pyr-KL) was investigated, which structures were characterized using FTIR, 31 P-NMR and GPC. The Ph-OH group of acetylated KL could be released by the addition of pyrrolidine; however the aliphatic hydroxyl group is still blocked. With the control of reaction conditions, the highest oxidation induction time of pyr-KL/PP (0.5wt% loading) reaches up to 22.6min, almost 2.6 times than that of pure PP. More importantly, the mechanical properties of PP were also maintained under the loading of pyr-KL, which is much better than that of curde KL/PP. Copyright © 2017 Elsevier B.V. All rights reserved.

Metal-ion interactions with carbohydrates. Crystal structure and FT-IR study of the SmCl3-ribose complex.

PubMed

Lu, Yan; Guo, Jianyu

2006-04-10

A single-crystal of SmCl3.C5H10O5.5H2O was obtained from methanol-water solution and its structure determined by X-ray. Two forms of the complex as a pair of anomers and related conformers were found in the single-crystal in a disordered state. One ligand is alpha-D-ribopyranose in the 4C1 conformation and the other one is beta-D-ribopyranose. The anomeric ratio is 1:1. Both ligands provide three hydroxyl groups in ax-eq-ax orientation for coordination. The Sm3+ ion is nine-coordinated with five Sm-O bonds from water molecules, three Sm-O bonds from hydroxyl groups of the D-ribopyranose and one Sm-Cl bond. The hydroxyl groups, water molecules and chloride ions form an extensive hydrogen-bond network. The IR spectral C-C, O-H, C-O, and C-O-H vibrations were observed to be shifted in the complex and the IR results are in accord with those of X-ray diffraction.

Ionizing radiation and tritium transmutation both cause formation of 5-hydroxymethyl-2'-deoxyuridine in cellular DNA.

PubMed Central

Teebor, G W; Frenkel, K; Goldstein, M S

1984-01-01

HeLa cells grown in the presence of [methyl-3H]thymidine contained large amounts of 5-hydroxymethyl-2'-deoxyuridine (HMdU) in their DNA. When the cells were grown in [6-3H]thymidine and their DNA was labeled to the same specific activity, no HMdU was present. When such [6-3H]thymidine-labeled cells were exposed to increasing amounts of gamma-radiation, small but increasing amounts of HMdU were formed in their DNA. This indicates that HMdU can be formed in DNA by two distinct mechanisms. The first is the result of the transmutation of 3H to 3He (beta decay) in the methyl group of thymidine, leading to formation of a carbocation. This short-lived ion reacts with hydroxide ions of water, yielding the hydroxymethyl group. HMdU that is formed by this mechanism is formed at the rate of beta decay of 3H. It appears only in [methyl-3H]thymidine residues and is present in the DNA of both nonirradiated and gamma-irradiated cells. The second mechanism is the result of the radiolysis of water caused by ionizing radiation. The resultant radical species, particularly hydroxyl radicals, may react with many sites on DNA. When the methyl group of thymine is attacked by hydroxyl radicals, the hydroxymethyl group is formed. The formation of HMdU by this mechanism was detected only when [6-3H]thymidine-labeled cells were used, since transmutation of 3H in position 6 of thymine cannot yield HMdU. PMID:6582490

Ionizing radiation and tritium transmutation both cause formation of 5-hydroxymethyl-2'-deoxyuridine in cellular DNA.

PubMed

Teebor, G W; Frenkel, K; Goldstein, M S

1984-01-01

HeLa cells grown in the presence of [methyl-3H]thymidine contained large amounts of 5-hydroxymethyl-2'-deoxyuridine (HMdU) in their DNA. When the cells were grown in [6-3H]thymidine and their DNA was labeled to the same specific activity, no HMdU was present. When such [6-3H]thymidine-labeled cells were exposed to increasing amounts of gamma-radiation, small but increasing amounts of HMdU were formed in their DNA. This indicates that HMdU can be formed in DNA by two distinct mechanisms. The first is the result of the transmutation of 3H to 3He (beta decay) in the methyl group of thymidine, leading to formation of a carbocation. This short-lived ion reacts with hydroxide ions of water, yielding the hydroxymethyl group. HMdU that is formed by this mechanism is formed at the rate of beta decay of 3H. It appears only in [methyl-3H]thymidine residues and is present in the DNA of both nonirradiated and gamma-irradiated cells. The second mechanism is the result of the radiolysis of water caused by ionizing radiation. The resultant radical species, particularly hydroxyl radicals, may react with many sites on DNA. When the methyl group of thymine is attacked by hydroxyl radicals, the hydroxymethyl group is formed. The formation of HMdU by this mechanism was detected only when [6-3H]thymidine-labeled cells were used, since transmutation of 3H in position 6 of thymine cannot yield HMdU.

Influence of Mechanical Stretching on Adsorption Properties of Nitrogen-Doped Graphene

NASA Astrophysics Data System (ADS)

Dolinskii, I. Yu.; Katin, K. P.; Grishakov, K. S.; Prudkovskii, V. S.; Kargin, N. I.; Maslov, M. M.

2018-04-01

This paper presents the results of quantum chemical modeling of chemisorption of atomic hydrogen and epoxy, carboxyl, and hydroxyl functional groups on nitrogen-doped graphene. It is shown that the substitutional nitrogen atom does not bind to adsorbing groups directly, but significantly increases the adsorption activity of neighboring carbon atoms. Mechanical stretching of doped graphene reduces the adsorption energy of all the aforementioned radicals. This reduction is significantly greater for the epoxy group than for the other functional groups. The results obtained confirm that, upon a sufficient stretching of a nitrogen-doped graphene sheet, the dissociation of molecular hydrogen and oxygen with subsequent precipitation of the resulting radicals onto graphene can be energetically favorable.

NMR and X-ray studies of isomeric 22,23-dihydroxy stigmastanes

NASA Astrophysics Data System (ADS)

Khripach, Vladimir A.; Zhabinskii, Vladimir N.; Ivanova, Galina V.; Fando, Galina P.; Tsavlovskii, Dmitrii V.; Khripach, Natalya B.; Lyakhov, Alexander S.; Misharin, Alexander Yu.

2010-06-01

A comparative conformational study of steroidal side chain of (22 R,23 R)- and (22 S,23 S)-dihydroxy stigmastane derivatives was performed using single crystal X-ray diffraction and NMR spectroscopy. The preferred conformation in solution was shown to be close to that in the crystal. (22 R,23 R)-Isomers typical for natural plant steroid hormones brassinosteroids adopt a conformation in which both hydroxyl groups are pointed toward unhindered α-side of the steroidal plane and can thus participate in biochemical processes. Unnatural (22 S,23 S)-counterparts exhibit a conformation with the two hydroxyl groups oriented in the opposite direction and sterically hindered by 21-methyl group and terminal side chain fragment.

Induction of protein oxidation in human low density lipoprotein by the photosensitive organic hydroperoxide, N,N'-bis(2-hydroxyperoxy-2-methoxyethyl)-1,4,5,8-naphthalene-tetra-carb oxylic- diimide.

PubMed

Matsugo, S; Yan, L J; Han, D; Packer, L

1995-01-05

We have developed a new molecular probe, N,N'-bis(2-hydroxyperoxy-2-methyoxyethyl)-1,4,5,8-naphthalen e-tetra-carboxylic- diimide (NP-III), that specifically generates hydroxyl radical upon irradiation with longer wavelength ultraviolet light (UVA). Hydroxyl radicals are generated only upon irradiation, thus NP-III is a new controllable hydroxyl radical source. Apolipoprotein (apo-B) of human low density lipoprotein (LDL), and bovine serum alubumin (BSA), were irradiated with UVA in the presence of NP-III and their oxidation was evaluated by two independent methods: assay of protein carbonyl groups and gel electrophoresis. NP-III oxidized apo-B and BSA in a time- and concentration-dependent manner. The results demonstrate that NP-III is a controllable, precise, and potentially tagetable source of hydroxyl radicals with which to induce protein oxidation.

Importance of tetrahedral intermediate formation in the catalytic mechanism of the serine proteases chymotrypsin and subtilisin.

PubMed

Petrillo, Teodolinda; O'Donohoe, Catrina A; Howe, Nicole; Malthouse, J Paul G

2012-08-07

Two new inhibitors in which the terminal α-carboxyl groups of Z-Ala-Ala-Phe-COOH and Z-Ala-Pro-Phe-COOH have been replaced with a proton to give Z-Ala-Ala-Phe-H and Z-Ala-Pro-Phe-H, respectively, have been synthesized. Using these inhibitors, we estimate that for α-chymotrypsin and subtilisin Carlsberg the terminal carboxylate group decreases the level of inhibitor binding 3-4-fold while a glyoxal group increases the level of binding by 500-2000-fold. We show that at pH 7.2 the effective molarities of the catalytic hydroxyl group of the active site serine are 41000-229000 and 101000-159000 for α-chymotrypsin and subtilisin Carlsberg, respectively. It is estimated that oxyanion stabilization and the increased effective molarity of the catalytic serine hydroxyl group can account for the catalytic efficiency of the reaction. We argue that substrate binding induces the formation of a strong hydrogen bond or low-barrier hydrogen bond between histidine-57 and aspartate-102 that increases the pK(a) of the active site histidine, allowing it to be an effective general base catalyst for the formation of the tetrahedral intermediate and increasing the effective molarity of the catalytic hydroxyl group of serine-195. A catalytic mechanism for acyl intermediate formation in the serine proteases is proposed.

Cobalt(II) ion as a promoter of hydroxyl radical and possible 'crypto-hydroxyl' radical formation under physiological conditions. Differential effects of hydroxyl radical scavengers.

PubMed

Moorhouse, C P; Halliwell, B; Grootveld, M; Gutteridge, J M

1985-12-13

Co(II) ions react with hydrogen peroxide under physiological conditions to form a 'reactive species' that can hydroxylate aromatic compounds (phenol and salicylate) and degrade deoxyribose to thiobarbituric-acid-reactive material. Catalase decreases the formation of this species but superoxide dismutase or low concentrations of ascorbic acid have little effect. EDTA, present in excess over the Co(II), can accelerate deoxyribose degradation and aromatic hydroxylation. In the presence of EDTA, deoxyribose degradation by the reactive species is inhibited competitively by scavengers of the hydroxyl radical (.OH), their effectiveness being related to their second-order rate constants for reaction with .OH. In the absence of EDTA the scavengers inhibit only at much higher concentrations and their order of effectiveness is changed. It is suggested that, in the presence of EDTA, hydroxyl radical is formed 'in free solution' and attacks deoxyribose or an aromatic molecule. In the absence of EDTA, .OH radical is formed in a 'site-specific' manner and is difficult to intercept by .OH scavengers. The relationship of these results to the proposed 'crypto .OH' radical is discussed.

Controlled supramolecular assembly of micelle-like gold nanoparticles in PS-b-P2VP diblock copolymers via hydrogen bonding.

PubMed

Jang, Se Gyu; Kramer, Edward J; Hawker, Craig J

2011-10-26

We report a facile strategy to synthesize amphiphilic gold (Au) nanoparticles functionalized with a multilayer, micelle-like structure consisting of a Au core, an inner hydroxylated polyisoprene (PIOH) layer, and an outer polystyrene shell (PS). Careful control of enthalpic interactions via a systematic variation of structural parameters, such as number of hydroxyl groups per ligand (N(OH)) and styrene repeating units (N(PS)) as well as areal chain density of ligands on the Au-core surface (Σ), enables precise control of the spatial distribution of these nanoparticles. This control was demonstrated in a lamellae-forming poly(styrene-b-2-vinylpyridine) (PS-b-P2VP) diblock copolymer matrix, where the favorable hydrogen-bonding interaction between hydroxyl groups in the PIOH inner shell and P2VP chains in the PS-b-P2VP diblock copolymer matrix, driving the nanoparticles to be segregated in P2VP domains, could be counter balanced by the enthalphic penalty of mixing of the PS outer brush with the P2VP domains. By varying N(OH), N(PS), and Σ, the nanoparticles could be positioned in the PS or P2VP domains or at the PS/P2VP interface. In addition, the effect of additives interfering with the hydrogen-bond formation between hydroxyl groups on Au nanoparticles and P2VP chains in a diblock copolymer matrix was investigated, and an interesting pea-pod-like segregation of Au nanoparticles in PS domains was observed.

Non-linear hydroxyl radical formation rate in dispersions containing mixtures of pyrite and chalcopyrite particles

NASA Astrophysics Data System (ADS)

Kaur, Jasmeet; Schoonen, Martin A.

2017-06-01

The formation of hydroxyl radicals was studied in mixed pyrite-chalcopyrite dispersions in water using the conversion rate of adenine as a proxy for hydroxyl radical formation rate. Experiments were conducted as a function of pH, presence of phosphate buffer, surface loading, and pyrite-to-chalcopyrite ratio. The results indicate that hydroxyl radical formation rate in mixed systems is non-linear with respect to the rates in the pure endmember dispersions. The only exception is a set of experiments in which phosphate buffer is used. In the presence of phosphate buffer, the hydroxyl radical formation is suppressed in mixtures and the rate is close to that predicted based on the reaction kinetics of the pure endmembers. The non-linear hydroxyl radical formation in dispersions containing mixtures of pyrite and chalcopyrite is likely the result of two complementary processes. One is the fact that pyrite and chalcopyrite form a galvanic couple. In this arrangement, chalcopyrite oxidation is accelerated, while pyrite passes electrons withdrawn from chalcopyrite to molecular oxygen, the oxidant. The incomplete reduction of molecular oxygen leads to the formation of hydrogen peroxide and hydroxyl radical. The galvanic coupling appears to be augmented by the fact that chalcopyrite generates a significant amount of hydrogen peroxide upon dispersal in water. This hydrogen peroxide is then available for conversion to hydroxyl radical, which appears to be facilitated by pyrite as chalcopyrite itself produces only minor amounts of hydroxyl radical. In essence, pyrite is a ;co-factor; that facilitates the conversion of hydrogen peroxide to hydroxyl radical. This conversion reaction is a surface-mediated reaction. Given that hydroxyl radical is one of the most reactive species in nature, the formation of hydroxyl radicals in aqueous systems containing chalcopyrite and pyrite has implications for the stability of organic molecules, biomolecules, the viability of microbes, and exposure to dust containing the two metal sulfides may present a health burden.

Prooxidative Potential of Photo-Irradiated Aqueous Extracts of Grape Pomace, a Recyclable Resource from Winemaking Process.

PubMed

Tsukada, Mana; Nakashima, Takuji; Kamachi, Toshiaki; Niwano, Yoshimi

2016-01-01

Our previous study revealed that aqueous extract of grape pomace obtained from a winemaking process could exert bactericidal action upon photo-irradiation via reactive oxygen species (ROS) formation. In the present study, we focused on chemical composition and prooxidative profile of the extract. Liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS) analysis showed that polyphenolic compounds including catechin monomers, dimers, trimers, and polyphenolic glucosides were contained. The polyphenol rich fraction used for the LC-ESI-MS analysis generated hydrogen peroxide (H2O2) upon photo-irradiation possibly initiated by photo-oxidation of phenolic hydroxyl group. That is, reduction of dissolved oxygen by proton-coupled electron transferred from the photo-oxidized phenolic hydroxyl group would form H2O2. The resultant H2O2 was then photolyzed to generate hydroxyl radical (•OH). The prooxidative profile of the extract in terms of •OH generation pattern upon photo-irradiation was similar to that of grape seed extract (GSE) as an authentic polyphenol product and (+)-catechin as a pure polyphenolic compound, and in all the three samples •OH generation could be retained during photo-irradiation for at least a couple of hours. The prooxidant activity of the photo-irradiated extract indicated by •OH yield was more potent than that of the photo-irradiated GSE and (+)-catechin, and this was well reflected in their bactericidal activity in which the photo-irradiated extract could kill the bacteria more efficiently than did the photo-irradiated GSE and (+)-catechin.

Prooxidative Potential of Photo-Irradiated Aqueous Extracts of Grape Pomace, a Recyclable Resource from Winemaking Process

PubMed Central

Nakashima, Takuji; Kamachi, Toshiaki

2016-01-01

Our previous study revealed that aqueous extract of grape pomace obtained from a winemaking process could exert bactericidal action upon photo-irradiation via reactive oxygen species (ROS) formation. In the present study, we focused on chemical composition and prooxidative profile of the extract. Liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS) analysis showed that polyphenolic compounds including catechin monomers, dimers, trimers, and polyphenolic glucosides were contained. The polyphenol rich fraction used for the LC-ESI-MS analysis generated hydrogen peroxide (H2O2) upon photo-irradiation possibly initiated by photo-oxidation of phenolic hydroxyl group. That is, reduction of dissolved oxygen by proton-coupled electron transferred from the photo-oxidized phenolic hydroxyl group would form H2O2. The resultant H2O2 was then photolyzed to generate hydroxyl radical (•OH). The prooxidative profile of the extract in terms of •OH generation pattern upon photo-irradiation was similar to that of grape seed extract (GSE) as an authentic polyphenol product and (+)-catechin as a pure polyphenolic compound, and in all the three samples •OH generation could be retained during photo-irradiation for at least a couple of hours. The prooxidant activity of the photo-irradiated extract indicated by •OH yield was more potent than that of the photo-irradiated GSE and (+)-catechin, and this was well reflected in their bactericidal activity in which the photo-irradiated extract could kill the bacteria more efficiently than did the photo-irradiated GSE and (+)-catechin. PMID:27341398

Structure-charge relationship - the case of hematite (001)

DOE PAGES

Lutzenkirchen, Johannes; Heberling, Frank; Supljika, Filip; ...

2015-01-16

We present a multidisciplinary study on the hematite (001)–aqueous solution interface, in particular the relationship between surface structure (studied via surface diffraction in a humid atmosphere) and the macroscopic charging (studied via surface- and zeta-potential measurements in electrolyte solutions as a function of pH). Upon aging in water changes in the surface structure are observed, that are accompanied by drastic changes in the zeta-potential. Surprisingly the surface potential is not accordingly affected. We interpret our results by increasing hydration of the surface with time and enhanced reactivity of singly-coordinated hydroxyl groups that cause the isoelectric point of the surface tomore » shift to values that are reminiscent of those typically reported for hematite particles. In its initial stages after preparation the hematite surface is very flat and only weakly hydrated. Our model links the entailing weak water structure with the observed low isoelectric point reminiscent of hydrophobic surfaces. The absence of an aging effect on the surface potential vs. pH curves is interpreted as domination of the surface potential by the doubly coordinated hydroxyls, which are present on both surfaces.« less

Interactions of flavonoids with iron and copper ions: a mechanism for their antioxidant activity.

PubMed

Mira, Lurdes; Fernandez, M Tereza; Santos, Marta; Rocha, Rui; Florêncio, M Helena; Jennings, Keith R

2002-11-01

The metal chelating properties of flavonoids suggest that they may play a role in metal-overload diseases and in all oxidative stress conditions involving a transition metal ion. A detailed study has been made of the ability of flavonoids to chelate iron (including Fe3+) and copper ions and its dependence of structure and pH. The acid medium may be important in some pathological conditions. In addition, the ability of flavonoids to reduce iron and copper ions and their activity-structure relationships were also investigated. To fulfill these objectives, flavones (apigenin, luteolin, kaempferol, quercetin, myricetin and rutin), isoflavones (daidzein and genistein), flavanones (taxifolin, naringenin and naringin) and a flavanol (catechin) were investigated. All flavonoids studied show higher reducing capacity for copper ions than for iron ions. The flavonoids with better Fe3+ reducing activity are those with a 2,3-double bond and possessing both the catechol group in the B-ring and the 3-hydroxyl group. The copper reducing activity seems to depend largely on the number of hydroxyl groups. The chelation studies were carried out by means of ultraviolet spectroscopy and electrospray ionisation mass spectrometry. Only flavones and the flavanol catechin interact with metal ions. At pH 7.4 and pH 5.5 all flavones studied appear to chelate Cu2+ at the same site, probably between the 5-hydroxyl and the 4-oxo groups. Myricetin and quercetin, however, at pH 7.4, appear to chelate Cu2+ additionally at the ortho-catechol group, the chelating site for catechin with Cu2+ at pH 7.4. Chelation studies of Fe3+ to flavonoids were investigated only at pH 5.5. Only myricetin and quercetin interact strongly with Fe3+, complexation probably occurring again between the 5-hydroxyl and the 4-oxo groups. Their behaviour can be explained by their ability to reduce Fe3+ at pH 5.5, suggesting that flavonoids reduce Fe3+ to Fe2+ before association.

Modification of agonist binding moiety in hybrid derivative 5/7-{[2-(4-aryl-piperazin-1-yl)-ethyl]-propyl-amino}-5,6,7,8-tetrahydro-naphthalen-1-ol/-2-amino versions: Impact on functional activity and selectivity for dopamine D2/D3 receptors

PubMed Central

Gopishetty, Bhaskar; Zhang, Suhong; Kharkar, Prashant S.; Antonio, Tamara; Reith, Maarten; Dutta, Aloke K.

2013-01-01

The goal of the present study was to explore, in our previously developed hybrid template, the effect of introduction of additional heterocyclic rings (mimicking catechol hydroxyl groups as bioisosteric replacement) on selectivity and affinity for the D3 versus D2 receptor. In addition, we wanted to explore the effect of derivatization of functional groups of the agonist binding moiety in compounds developed by us earlier from the hybrid template. Binding affinity (Ki) of the new compounds was measured with tritiated spiperone as the radioligand and HEK-293 cells expressing either D2 or D3 receptors. Functional activity of selected compounds was assessed in the GTPγS binding assay. In the imidazole series, compound 10a exhibited the highest D3 affinity whereas the indole derivative 13 exhibited similar high D3 affinity. Functionalization of the amino group in agonist (+)-9d with different sulfonamides derivatives improved the D3 affinity significantly with (+)-14f exhibiting the highest affinity. However, functionalization of the hydroxyl and amino groups of 15 and (+)-9d, known agonist and partial agonist, to sulfonate ester and amide in general modulated the affinity. In both cases loss of agonist potency resulted from such derivatization. PMID:23623679

Riccardin C derivatives as anti-MRSA agents: structure-activity relationship of a series of hydroxylated bis(bibenzyl)s.

PubMed

Sawada, Hiromi; Okazaki, Miki; Morita, Daichi; Kuroda, Teruo; Matsuno, Kenji; Hashimoto, Yuichi; Miyachi, Hiroyuki

2012-12-15

Members of a series of macrocyclic bis(bibenzyl) riccardin-class derivatives were found to exhibit antibacterial activity towards methicillin-resistant Staphylococcus aureus (anti-MRSA activity). Structure-activity relationship (SAR) studies were conducted, focusing on the number and position of the hydroxyl groups. The minimum essential structure for anti-MRSA activity was also investigated. Copyright © 2012 Elsevier Ltd. All rights reserved.

Preparation of linear hydroxy substituted polyphosphazenes. [flame retardant polyurethane foam

NASA Technical Reports Server (NTRS)

Paciorek, K. L.; Ito, T. I.; Kratzer, R. H.

1978-01-01

The synthesis of partially hydroxy-substituted phosphazene prepolymers amenable to processing into cellular, flexible polyurethane foams was investigated. Factors determined include (1) the environment of the hydroxyl group; (2) the ease of the hexachlorocyclotriphosphazene polymerization; (3) the nature of the nonreactive substituents; and (4) the mode of introduction of the hydroxyl entity. The specific approaches taken, the rationale of the selections made, and the results are discussed.

Mucor hiemalis mediated 14α-hydroxylation on steroids: in vivo and in vitro investigations of 14α-hydroxylase activity.

PubMed

Kolet, Swati P; Haldar, Saikat; Niloferjahan, Siddiqui; Thulasiram, Hirekodathakallu V

2014-07-01

Transformation of testosterone and progesterone into synthetically challenging 14α-hydroxy derivatives was achieved by using fungal strain Mucor hiemalis. Prolonged incubation led to the formation of corresponding 6β/7α,14α-dihydroxy metabolites. The position and stereochemistry of newly introduced hydroxyl group was determined by detailed spectroscopic analyses. The time course experiment indicated that fungal strain initiated transformation by hydroxylation at 14α-position followed by at 6β- or 7α-positions. Studies using cell-free extracts suggest that the 14α-hydroxylase activity is NADPH dependent and belongs to the cytochrome P450 family. Copyright © 2014 Elsevier Inc. All rights reserved.

Coq6 Is Responsible for the C4-deamination Reaction in Coenzyme Q Biosynthesis in Saccharomyces cerevisiae*

PubMed Central

Ozeir, Mohammad; Pelosi, Ludovic; Ismail, Alexandre; Mellot-Draznieks, Caroline; Fontecave, Marc; Pierrel, Fabien

2015-01-01

The yeast Saccharomyces cerevisiae is able to use para-aminobenzoic acid (pABA) in addition to 4-hydroxybenzoic acid as a precursor of coenzyme Q, a redox lipid essential to the function of the mitochondrial respiratory chain. The biosynthesis of coenzyme Q from pABA requires a deamination reaction at position C4 of the benzene ring to substitute the amino group with an hydroxyl group. We show here that the FAD-dependent monooxygenase Coq6, which is known to hydroxylate position C5, also deaminates position C4 in a reaction implicating molecular oxygen, as demonstrated with labeling experiments. We identify mutations in Coq6 that abrogate the C4-deamination activity, whereas preserving the C5-hydroxylation activity. Several results support that the deletion of Coq9 impacts Coq6, thus explaining the C4-deamination defect observed in Δcoq9 cells. The vast majority of flavin monooxygenases catalyze hydroxylation reactions on a single position of their substrate. Coq6 is thus a rare example of a flavin monooxygenase that is able to act on two different carbon atoms of its C4-aminated substrate, allowing its deamination and ultimately its conversion into coenzyme Q by the other proteins constituting the coenzyme Q biosynthetic pathway. PMID:26260787

Selective chemical labeling reveals the genome-wide distribution of 5-hydroxymethylcytosine.

PubMed

Song, Chun-Xiao; Szulwach, Keith E; Fu, Ye; Dai, Qing; Yi, Chengqi; Li, Xuekun; Li, Yujing; Chen, Chih-Hsin; Zhang, Wen; Jian, Xing; Wang, Jing; Zhang, Li; Looney, Timothy J; Zhang, Baichen; Godley, Lucy A; Hicks, Leslie M; Lahn, Bruce T; Jin, Peng; He, Chuan

2011-01-01

In contrast to 5-methylcytosine (5-mC), which has been studied extensively, little is known about 5-hydroxymethylcytosine (5-hmC), a recently identified epigenetic modification present in substantial amounts in certain mammalian cell types. Here we present a method for determining the genome-wide distribution of 5-hmC. We use the T4 bacteriophage β-glucosyltransferase to transfer an engineered glucose moiety containing an azide group onto the hydroxyl group of 5-hmC. The azide group can be chemically modified with biotin for detection, affinity enrichment and sequencing of 5-hmC-containing DNA fragments in mammalian genomes. Using this method, we demonstrate that 5-hmC is present in human cell lines beyond those previously recognized. We also find a gene expression level-dependent enrichment of intragenic 5-hmC in mouse cerebellum and an age-dependent acquisition of this modification in specific gene bodies linked to neurodegenerative disorders.

Evolution of Functional Groups during Pyrolysis Oil Upgrading

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stankovikj, Filip; Tran, Chi-Cong; Kaliaguine, Serge

In this paper, we examine the evolution of functional groups (carbonyl, carboxyl, phenol, and hydroxyl) during stabilization at 100–200 °C of two typical wood derived pyrolysis oils from BTG and Amaron in a batch reactor over Ru/C catalyst for 4h. An aqueous and an oily phase were obtained. The content of functional groups in both phases were analyzed by GC/MS, 31P-NMR, 1H-NMR, elemental analysis, KF titration, carbonyl groups by Faix, Folin – Ciocalteu method and UV-Fluorescence. The consumption of hydrogen was between 0.007 and 0.016 g/g oil, and 0.001-0.020 g of CH4/g of oil, 0.005-0.016 g of CO2/g oil andmore » 0.03-0.10 g H2O/g oil were formed. The content of carbonyl, hydroxyl, and carboxyl groups in the volatile GC-MS detectable fraction decreased (80, 65, and ~70% respectively), while their behavior in the total oil and hence in the non-volatile fraction was more complex. The carbonyl groups initially decreased having minimum at ~125-150°C and then increased, while the hydroxyl groups had reversed trend. This might be explained by initial hydrogenation of the carbonyl groups to form hydroxyls, followed by continued dehydration reactions at higher temperatures that may increase their content. The 31P-NMR was on the limit of its sensitivity for the carboxylic groups to precisely detect changes in the non-volatile fraction, however the more precise titration method showed that the concentration of carboxylic groups in the non-volatile fraction remains constant with increased stabilization temperature. The UV-Fluorescence results show that repolymerization increases with temperature. ATR-FTIR method coupled with deconvolution of the region between 1490 and 1850 cm-1 showed to be a good tool for following the changes in carbonyl groups and phenols of the stabilized pyrolysis oils. The deconvolution of the IR bands around 1050 and 1260 cm-1 correlated very well with the changes in the 31P-NMR silent O groups (likely ethers). Most of the H2O formation could be explained from the significant reduction of these silent O groups (from 12% in the fresh oils, to 6 to 2% in the stabilized oils) most probably belonging to ethers.« less

Function of specific 2'-hydroxyl groups of guanosines in a hammerhead ribozyme probed by 2' modifications.

PubMed Central

Williams, D M; Pieken, W A; Eckstein, F

1992-01-01

The importance of the 2'-hydroxyl group of several guanosine residues for the catalytic efficiency of a hammerhead ribozyme has been investigated. Five ribozymes in which single guanosine residues were substituted with 2'-amino-, 2'-fluoro-, or 2'-deoxyguanosine were chemically synthesized. The comparison of the catalytic activity of the three 2' modifications at a specific position allows conclusions about the functional role of the parent 2'-hydroxyl group. Substitutions of nonconserved nucleotides within the ribozyme caused little alteration in the catalytic activity relative to that obtained with the unmodified ribozyme. In contrast, when either of the guanosines within the single-stranded loop between stem I and stem II of the ribozyme was replaced by 2'-deoxyguanosine or 2'-fluoro-2'-deoxyguanosine, the catalytic activities of the resulting ribozymes were reduced by factors of at least 150. The catalytic activities of the corresponding ribozymes containing 2'-amino-2'-deoxyguanosine substitutions at these positions, however, were both reduced by factors of 15. These effects resulted from decreases in the respective kcat values, whereas variations in the Km values were comparatively small. A different pattern of reactivity of the three 2' modifications was observed at the guanosine immediately 3' to stem II of the ribozyme. Whereas both 2'-deoxyguanosine and 2'-amino-2'-deoxyguanosine at this position showed catalytic activity similar to that of the unmodified ribozyme, the activity of the corresponding 2'-fluoro-2'-deoxyguanosine-containing ribozyme was reduced by a factor of 15. The implications of these substitution-specific reactivities on the functional role of the native 2'-hydroxyl groups are discussed. Images PMID:1736306

Number of Hydroxyl Groups on the B-Ring of Flavonoids Affects Their Antioxidant Activity and Interaction with Phorbol Ester Binding Site of PKCδ C1B Domain: In Vitro and in Silico Studies.

PubMed

Kongpichitchoke, Teeradate; Hsu, Jue-Liang; Huang, Tzou-Chi

2015-05-13

Although flavonoids have been reported for their benefits and nutraceutical potential use, the importance of their structure on their beneficial effects, especially on signal transduction mechanisms, has not been well clarified. In this study, three flavonoids, pinocembrin, naringenin, and eriodictyol, were chosen to determine the effect of hydroxyl groups on the B-ring of flavonoid structure on their antioxidant activity. In vitro assays, including DPPH scavenging activity, ROS quantification by flow cytometer, and proteins immunoblotting, and in silico analysis by molecular docking between the flavonoids and C1B domain of PKCδ phorbol ester binding site were both used to complete this study. Eriodictyol (10 μM), containing two hydroxyl groups on the B-ring, exhibited significantly higher (p < 0.05) antioxidant activity than pinocembrin and naringenin. The IC50 values of eriodictyol, naringenin, and pinocembrin were 17.4 ± 0.40, 30.2 ± 0.61, and 44.9 ± 0.57 μM, respectively. In addition, eriodictyol at 10 μM remarkably inhibited the phosphorylation of PKCδ at 63.4% compared with PMA-activated RAW264.7, whereas pinocembrin and naringenin performed inhibition activity at 76.8 and 72.6%, respectively. According to the molecular docking analysis, pinocembrin, naringenin, and eriodictyol showed -CDOCKER_energy values of 15.22, 16.95, and 21.49, respectively, reflecting that eriodictyol could bind with the binding site better than the other two flavonoids. Interestingly, eriodictyol had a remarkably different pose to bind with the kinase as a result of the two hydroxyl groups on its B-ring, which consequently contributed to greater antioxidant activity over pinocembrin and naringenin.

The 4′-Hydroxyl Group of Resveratrol Is Functionally Important for Direct Activation of PPARα

PubMed Central

Takizawa, Yoshie; Nakata, Rieko; Fukuhara, Kiyoshi; Yamashita, Hiroshi; Kubodera, Hideo; Inoue, Hiroyasu

2015-01-01

Long-term moderate consumption of red wine is associated with a reduced risk of developing lifestyle-related diseases such as cardiovascular disease and cancer. Therefore, resveratrol, a constituent of grapes and various other plants, has attracted substantial interest. This study focused on one molecular target of resveratrol, the peroxisome proliferator activated receptor α (PPARα). Our previous study in mice showed that resveratrol-mediated protection of the brain against stroke requires activation of PPARα; however, the molecular mechanisms involved in this process remain unknown. Here, we evaluated the chemical basis of the resveratrol-mediated activation of PPARα by performing a docking mode simulation and examining the structure-activity relationships of various polyphenols. The results of experiments using the crystal structure of the PPARα ligand-binding domain and an analysis of the activation of PPARα by a resveratrol analog 4-phenylazophenol (4-PAP) in vivo indicate that the 4′-hydroxyl group of resveratrol is critical for the direct activation of PPARα. Activation of PPARα by 5 μM resveratrol was enhanced by rolipram, an inhibitor of phosphodiesterase (PDE) and forskolin, an activator of adenylate cyclase. We also found that resveratrol has a higher PDE inhibitory activity (IC50 = 19 μM) than resveratrol analogs trans-4-hydroxystilbene and 4-PAP (IC50 = 27-28 μM), both of which has only 4′-hydroxyl group, indicating that this 4′-hydroxyl group of resveratrol is not sufficient for the inhibition of PDE. This result is consistent with that 10 μM resveratrol has a higher agonistic activity of PPARα than these analogs, suggesting that there is a feedforward activation loop of PPARα by resveratrol, which may be involved in the long-term effects of resveratrol in vivo. PMID:25798826

Elucidation of hydroxyl groups-antioxidant relationship in mono- and dihydroxyflavones based on O-H bond dissociation enthalpies.

PubMed

Treesuwan, Witcha; Suramitr, Songwut; Hannongbua, Supa

2015-06-01

Radical scavenging potential is the key to anti-oxidation of hydroxyflavones which generally found in fruits and vegetables. The objective of this work was to investigate the influence of hydroxyl group on the O-H bond dissociation enthalpies (BDE) from a series of mono- and dihydroxyflavones. Calculation at the B3LYP/6-31G(d,p) level reveals the important roles of an additional one hydroxyl group to boost the BDE of hydroxyflavones that were a stabilization of the generated radicals through attractive H-bond interactions, an ortho- and para-dihydroxyl effect, and a presence of the 3-OH in dihydroxyflavones. On the other hand, the meta-dihydroxyl effect and range-hydroxyl effect especially associated with the either 5-OH or 8-OH promoted greater BDE. Results did not only confirm that dihydroxyflavones had lower BDE than monohydroxyflavones but also suggest the selective potent hydroxyflavone molecules that are the 6'-hydroxyflavone (for monohydroxyflavone) and the 5',6'-, 7,8- and 3',4'-dihydroxyflavone which the corresponding radical preferable generated at C6'-O•, C8-O• and C4'-O•, respectively. Electron distribution was limited only over the two connected rings of hydroxyflavones while the expansion distribution into C-ring could be enhanced if the radical was formed especially for the 2',3'- and 5',6'dihydroxyflavone radicals. The delocalized bonds were strengthened after radical was generated. However the 5-O• in 5,6-dihydroxyflavone and the 3-O• in 3,6'-dihydroxyflavone increased the bond order at C4-O11 which might interrupt the conjugated delocalized bonds at the keto group.

Effect of mechanical activation on structure changes and reactivity in further chemical modification of lignin.

PubMed

Zhao, Xiaohong; Zhang, Yanjuan; Hu, Huayu; Huang, Zuqiang; Yang, Mei; Chen, Dong; Huang, Kai; Huang, Aimin; Qin, Xingzhen; Feng, Zhenfei

2016-10-01

Lignin was treated by mechanical activation (MA) in a customized stirring ball mill, and the structure and reactivity in further esterification were studied. The chemical structure and morphology of MA-treated lignin and the esterified products were analyzed by chemical analysis combined with UV/vis spectrometer, FTIR,NMR, SEM and particle size analyzer. The results showed that MA contributed to the increase of aliphatic hydroxyl, phenolic hydroxyl, carbonyl and carboxyl groups but the decrease of methoxyl groups. Moreover, MA led to the decrease of particle size and the increase of specific surface area and roughness of surface in lignin. The reactivity of lignin was enhanced significantly for the increase of hydroxyl content and the improvement of mass transfer in chemical reaction caused by the changes of molecular structure and morphological structure. The process of MA is green and simple, and is an effective method for enhancing the reactivity of lignin. Copyright © 2016 Elsevier B.V. All rights reserved.

KM+, a mannose-binding lectin from Artocarpus integrifolia: amino acid sequence, predicted tertiary structure, carbohydrate recognition, and analysis of the beta-prism fold.

PubMed Central

Rosa, J. C.; De Oliveira, P. S.; Garratt, R.; Beltramini, L.; Resing, K.; Roque-Barreira, M. C.; Greene, L. J.

1999-01-01

The complete amino acid sequence of the lectin KM+ from Artocarpus integrifolia (jackfruit), which contains 149 residues/mol, is reported and compared to those of other members of the Moraceae family, particularly that of jacalin, also from jackfruit, with which it shares 52% sequence identity. KM+ presents an acetyl-blocked N-terminus and is not posttranslationally modified by proteolytic cleavage as is the case for jacalin. Rather, it possesses a short, glycine-rich linker that unites the regions homologous to the alpha- and beta-chains of jacalin. The results of homology modeling implicate the linker sequence in sterically impeding rotation of the side chain of Asp141 within the binding site pocket. As a consequence, the aspartic acid is locked into a conformation adequate only for the recognition of equatorial hydroxyl groups on the C4 epimeric center (alpha-D-mannose, alpha-D-glucose, and their derivatives). In contrast, the internal cleavage of the jacalin chain permits free rotation of the homologous aspartic acid, rendering it capable of accepting hydrogen bonds from both possible hydroxyl configurations on C4. We suggest that, together with direct recognition of epimeric hydroxyls and the steric exclusion of disfavored ligands, conformational restriction of the lectin should be considered to be a new mechanism by which selectivity may be built into carbohydrate binding sites. Jacalin and KM+ adopt the beta-prism fold already observed in two unrelated protein families. Despite presenting little or no sequence similarity, an analysis of the beta-prism reveals a canonical feature repeatedly present in all such structures, which is based on six largely hydrophobic residues within a beta-hairpin containing two classic-type beta-bulges. We suggest the term beta-prism motif to describe this feature. PMID:10210179

The Nitrite-Scavenging Properties of Catechol, Resorcinol, and Hydroquinone: A Comparative Study on Their Nitration and Nitrosation Reactions.

PubMed

Lu, Yunhao; Dong, Yanzuo; Li, Xueli; He, Qiang

2016-10-14

The nitration and nitrosation reactions of catechol, resorcinol, and hydroquinone (0.05 mmol/L) with sodium nitrite (0.05 mmol/L) at pH 3 and 37 °C were studied by using liquid chromatography and mass spectrometry (LC-MS) and atom charge analysis, which was aimed to provide chemical insight into the nitrite-scavenging behavior of polyphenols. The 3 benzenediols showed different mechanisms to scavenge nitrite due to their differences in hydroxyl position. Catechol was nitrated with 1 NO 2 group at the hydroxyl oxygen, and resorcinol was nitrosated with 2 NO groups at the C 2 and C 4 (or C 6 ) positions of the benzene ring. Hydroquinone could scavenge nitrite through both nitration and nitrosation mechanisms. The nitrated hydroquinone had 1 NO 2 group at the hydroxyl oxygen in the molecule, while the nitrosated 1 containing 2 NO groups at the benzene ring might have 3 structure probabilities. The results may provide a structure-activity understanding on the nitrite-scavenging property of polyphenols, so as to promote their application in the food industry for the removal of possibly toxic nitrites found in many vegetables and often in processed meat products. © 2016 Institute of Food Technologists®.

Catalytic Hydroxylation of Polyethylenes

PubMed Central

2017-01-01

Polyolefins account for 60% of global plastic consumption, but many potential applications of polyolefins require that their properties, such as compatibility with polar polymers, adhesion, gas permeability, and surface wetting, be improved. A strategy to overcome these deficiencies would involve the introduction of polar functionalities onto the polymer chain. Here, we describe the Ni-catalyzed hydroxylation of polyethylenes (LDPE, HDPE, and LLDPE) in the presence of mCPBA as an oxidant. Studies with cycloalkanes and pure, long-chain alkanes were conducted to assess precisely the selectivity of the reaction and the degree to which potential C–C bond cleavage of a radical intermediate occurs. Among the nickel catalysts we tested, [Ni(Me4Phen)3](BPh4)2 (Me4Phen = 3,4,7,8,-tetramethyl-1,10-phenanthroline) reacted with the highest turnover number (TON) for hydroxylation of cyclohexane and the highest selectivity for the formation of cyclohexanol over cyclohexanone (TON, 5560; cyclohexanol/(cyclohexanone + ε-caprolactone) ratio, 10.5). The oxidation of n-octadecane occurred at the secondary C–H bonds with 15.5:1 selectivity for formation of an alcohol over a ketone and 660 TON. Consistent with these data, the hydroxylation of various polyethylene materials by the combination of [Ni(Me4Phen)3](BPh4)2 and mCPBA led to the introduction of 2.0 to 5.5 functional groups (alcohol, ketone, alkyl chloride) per 100 monomer units with up to 88% selectivity for formation of alcohols over ketones or chloride. In contrast to more classical radical functionalizations of polyethylene, this catalytic process occurred without significant modification of the molecular weight of the polymer that would result from chain cleavage or cross-linking. Thus, the resulting materials are new compositions in which hydroxyl groups are located along the main chain of commercial, high molecular weight LDPE, HDPE, and LLDPE materials. These hydroxylated polyethylenes have improved wetting properties and serve as macroinitiators to synthesize graft polycaprolactones that compatibilize polyethylene–polycaprolactone blends. PMID:28852704

Elastohydrodynamics of farm-based blends comprising amphiphilic oils

USDA-ARS?s Scientific Manuscript database

Vegetable oils contain non-polar hydrocarbon chains and polar ester groups (and possibly also other functional groups such as hydroxyl groups in castor oil). The presence of polar and non-polar groups within the same molecule gives vegetable oil amphiphilic character. The density, refractive index, ...

Analysis of mycolic acids from a group of corynebacteria by capillary gas chromatography and mass spectrometry.

PubMed

Gailly, C; Sandra, P; Verzele, M; Cocito, C

1982-06-15

The cell wall of leprosy-derived corynebacteria (a group of 'diphtheroids' isolated from human leprosy lesions and patients' blood) was previously shown to contain, in addition to peptidoglycan and arabinogalactan, mycolic acids. These alpha-branched beta-hydroxy fatty acids were attributed to the corynomycolic group, according to their RF in monodimensional thin-layer chromatography. In the present work, mycolic acids from leprosy-derived and reference corynebacteria have been fractionated by monodimensional and bidimensional thin-layer chromatography and by gas chromatography. Pyrolyzed mycolic acids have been analyzed on conventional packed columns, whereas intact methyl esters of mycolic acids with free and silylated beta-hydroxyl group have been analyzed on capillary columns, and their structure has been established by mass spectrometry. In all leprosy-derived corynebacteria, some 20 components containing 24-36 carbon atoms and 0-4 double bonds were obtained. The three major groups had 32, 34 and 36 carbons, and the frequency of unsaturated versus saturated chains increased proportionally to the molecular weight. For comparison, the main components of a reference corynebacterium. Corynebacterium diphtheriae PW8, had 30 and 32 carbons, and their hydrocarbon chains were essentially saturated. This work confirms the relative chemical homogeneity of different leprosy-derived corynebacteria and describes some peculiar traits in the chemical structure of this group of organisms. In addition, it shows the complexity of the mycolic acid fraction of corynebacterial cell wall and suggests that the mycolic acid pattern is a sort of fingerprint of each bacterial strain grown under standard conditions. Finally, the fractionation of intact corynomycolic acid methyl esters with free or silylated beta-hydroxyl group by capillary gas chromatography proved to be the best analytical procedure at present available for resolving this complex mixture of corynomycolate isomers. Structural determination of silylated samples by mass spectrometry is preferred because they have more diagnostic fragments.

Comparison of salicylate and D-phenylalanine for detection of hydroxyl radicals in chemical and biological reactions.

PubMed

Bailey, S M; Fauconnet, A L; Reinke, L A

1997-02-01

Hydroxylation of salicylate and D-phenylalanine was measured to test the usefulness of these compounds for hydroxyl radical (HO(•)) detection in chemical and biological systems. When HO(•) were produced by the photolytic decomposition of hydrogen peroxide, nearly equal amounts of 2,5- and 2,3-dihydroxybenzoic acid (DHBA) were produced from salicylate, with catechol as a minor product. In the photolytic reaction, nearly equal concentrations of p-,m-, and o-tyrosine were formed from D-phenylalanine. When salicylate or D-phenylalanine was present with Fenton reagents or in iron(II) autoxidation systems, the relative proportions of hydroxylated products were similar to those observed after photolysis, although less total products were usually detected. In contrast, when similar experiments were conducted with isolated hepatic microsomes and perfused livers, 2,5-DHBA was the primary product from salicylate, and p-tyrosine was the major product from D-phenylalanine. Cytochrome P-450 enzymes can hydroxylate salicylate to produce 2,5-DHBA, and it is likely that phenylalanine hydroxylase produces most of the p-tyrosine detected in hepatic tissues. Thus, although both salicylate and D-phenylalanine are useful probes for hydroxyl radical formation in chemical systems, hydroxylated products formed from enzymatic reactions complicate interpretation of data from both compounds in vivo.

Evaporation and Hydrocarbon Chain Conformation of Surface Lipid Films

PubMed Central

Sledge, Samiyyah M.; Khimji, Hussain; Borchman, Douglas; Oliver, Alexandria; Michael, Heidi; Dennis, Emily K.; Gerlach, Dylan; Bhola, Rahul; Stephen, Elsa

2016-01-01

Purpose The inhibition of the rate of evaporation (Revap) by surface lipids is relevant to reservoirs and dry eye. Our aim was to test the idea that lipid surface films inhibit Revap. Methods Revap were determined gravimetrically. Hydrocarbon chain conformation and structure were measured using a Raman microscope. Six 1-hydroxyl hydrocarbons (11–24 carbons in length) and human meibum were studied. Reflex tears were obtained from a 62-year-old male. Results The Raman scattering intensity of the lipid film deviated by about 7 % for hydroxyl lipids and varied by 21 % for meibum films across the entire film at a resolution of 5 µm2. All of the surface lipids were ordered. Revap of the shorter chain hydroxyl lipids were slightly (7%) but significantly lower compared with the longer chain hydroxyl lipids. Revap of both groups was essentially similar to that of buffer. A hydroxyl lipid film did not influence Revap over an estimated average thickness range of 0.69 to >6.9 µm. Revap of human tears and buffer with and without human meibum (34.4 µm thick) was not significantly different. Revap of human tears was not significantly different from buffer. Conclusions Human meibum and hydroxyl lipids, regardless of their fluidity, chain length, or thickness did not inhibit Revap of buffer or tears even though they completely covered the surface. It is unlikely that hydroxyl lipids can be used to inhibit Revap of reservoirs. Our data do not support the widely accepted (yet unconfirmed) idea that the tear film lipid layer inhibits Revap of tears. PMID:27395776

Chemoselective methylation of phenolic hydroxyl group prevents quinone methide formation and repolymerization during lignin depolymerization

DOE PAGES

Kim, Kwang Ho; Dutta, Tanmoy; Walter, Eric D.; ...

2017-03-22

Chemoselective blocking of the phenolic hydroxyl (Ar–OH) group by methylation was found to suppress secondary repolymerization and charring during lignin depolymerization. Methylation of Ar–OH prevents formation of reactive quinone methide intermediates, which are partly responsible for undesirable secondary repolymerization reactions. Instead, this structurally modified lignin produces more relatively low molecular weight products from lignin depolymerization compared to unmodified lignin. This result demonstrates that structural modification of lignin is desirable for production of low molecular weight phenolic products. Finally, this approach could be directed toward alteration of natural lignification processes to produce biomass that is more amenable to chemical depolymerization.

A Novel Mechanism of Sugar Selection Utilized by a Human X-family DNA Polymerase†

PubMed Central

Brown, Jessica A.; Fiala, Kevin A.; Fowler, Jason D.; Sherrer, Shanen M.; Newmister, Sean A.; Dyum, Wade W.; Suo, Zucai

2009-01-01

During DNA synthesis, most DNA polymerases and reverse transcriptases select against ribonucleotides via a steric clash between the ribose 2′-hydroxyl group and the bulky side chain of an active site residue. Here, we demonstrated that human DNA polymerase λ used a novel sugar selection mechanism to discriminate against ribonucleotides, whereby the ribose 2′-hydroxyl group was excluded mostly by a backbone segment and slightly by the side chain of Y505. Such a steric clash was further demonstrated to be dependent on the size and orientation of the substituent covalently attached at the ribonucleotide C2′ position. PMID:19900463

Hydration and rotational diffusion of levoglucosan in aqueous solutions

NASA Astrophysics Data System (ADS)

Corezzi, S.; Sassi, P.; Paolantoni, M.; Comez, L.; Morresi, A.; Fioretto, D.

2014-05-01

Extended frequency range depolarized light scattering measurements of water-levoglucosan solutions are reported at different concentrations and temperatures to assess the effect of the presence and distribution of hydroxyl groups on the dynamics of hydration water. The anhydro bridge, reducing from five to three the number of hydroxyl groups with respect to glucose, considerably affects the hydration properties of levoglucosan with respect to those of mono and disaccharides. In particular, we find that the average retardation of water dynamics is ≈3-4, that is lower than ≈5-6 previously found in glucose, fructose, trehalose, and sucrose. Conversely, the average number of retarded water molecules around levoglucosan is 24, almost double that found in water-glucose mixtures. These results suggest that the ability of sugar molecules to form H-bonds through hydroxyl groups with surrounding water, while producing a more effective retardation, it drastically reduces the spatial extent of the perturbation on the H-bond network. In addition, the analysis of the concentration dependence of the hydration number reveals the aptitude of levoglucosan to produce large aggregates in solution. The analysis of shear viscosity and rotational diffusion time suggests a very short lifetime for these aggregates, typically faster than ≈20 ps.

Rheological and Thermal Properties of Bio-based Hyperbranched Polyesters

NASA Astrophysics Data System (ADS)

Bubeck, Robert; Dumitrascu, Adina; Zhang, Tracy; Smith, Patrick

Hyperbranched poly(ester)s (HBPEs) of designed molecular structures and targeted molecular weight can be prepared from a variety of multi-functional acids and alcohols. These polymers find application in the areas of coatings and rheology modifiers for coatings. These functional polymers can be synthesized in variety of architectures, possessing either hydroxyl or carboxyl reactive end-groups suitable for the attachment of active entities. The rheological characteristics as related to variation in molecular structure were determined using cone and plate or couette geometries. Viscosities of the HBPEs were found to be near Newtonian. HB polymers permit the control of Tg that is not as readily attained with linear polymers. Accordingly, Tg and viscosity are affected little as a function of Mw but vary dramatically with the nature of the end-groups, are highly dependent on hydrogen bonding of the hydroxyl end groups, and decrease dramatically with the incorporation of aliphatic end-caps. The thermal properties and the degradation characteristics of the HBPEs were determined. Thermal degradation of the hydroxyl-terminal HBPEs is initiated by dehydrative ether formation (crosslinking) while decarboxylation is the initial decomposition event for the carboxyl-terminal polymers. Midland, MI Campus.

Analyzing the adsorption of blood plasma components by means of fullerene-containing silica gels and NMR spectroscopy in solids

NASA Astrophysics Data System (ADS)

Melenevskaya, E. Yu.; Mokeev, M. V.; Nasonova, K. V.; Podosenova, N. G.; Sharonova, L. V.; Gribanov, A. V.

2012-10-01

The results from studying the adsorption of blood plasma components (e.g., protein, triglycerides, cholesterol, and lipoproteins of low and high density) using silica gels modified with fullerene molecules (in the form of C60 or the hydroxylated form of C60(OH) x ) and subjected to hydration (or, alternatively, dehydration) are presented. The conditions for preparing adsorbents that allow us to control the adsorption capacity of silica gel and the selectivity of adsorption toward the components of blood plasma, are revealed. The nature and strength of the interactions of the introduced components (fullerene molecules and water) with functional groups on the silica surface are studied by means of solid state NMR spectroscopy (NMR-SS). Conclusions regarding the nature of the centers that control adsorption are drawn on the basis of NMR-SS spectra in combination with direct measurements of adsorption. The interaction of the oxygen of the hydroxyl group of silica gel with fullerene, leading to the formation of electron-donor complexes of C60-H, C60-OH, or C60-OSi type, is demonstrated by the observed changes in the NMR-SS spectra of silica gels in the presence of fullerene.

Effects of CO2 adsorption on proton migration on a hydrated ZrO2 surface: an ab initio molecular dynamics study.

PubMed

Sato, Ryuhei; Shibuta, Yasushi; Shimojo, Fuyuki; Yamaguchi, Shu

2017-08-02

Hydration reactions on a carbonate-terminated cubic ZrO 2 (110) surface were analyzed using ab initio molecular dynamics (AIMD) simulations. After hydration reactions, carbonates were still present on the surface at 500 K. However, these carbonates are very weak conjugate bases and only act as steric hindrance in proton hopping processes between acidic chemisorbed H 2 O molecules (Zr-OH 2 ) and monodentate hydroxyl groups (Zr-OH - ). Similar to a carbonate-free hydrated surface, Zr-OH 2 , Zr-OH - , and polydentate hydroxyl groups ([double bond splayed left]OH + ) were observed, while the ratio of acidic Zr-OH 2 was significantly larger than that on the carbonate-free hydrated surface. A thermodynamic discussion and bond property analysis reveal that CO 2 adsorption significantly decreases the basicity of surface oxide ions ([double bond splayed left]O), whereas the acidity of Zr-OH 2 is not affected. As a result, protons released from [double bond splayed left]OH + react with Zr-OH - to form Zr-OH 2 , leading to a deficiency of proton acceptor sites, which decreases the proton conductivity by the hopping mechanism.

Specific intermolecular interactions of conserved water molecules with amino acids in the Galectin-1 carbohydrate recognition domain

NASA Astrophysics Data System (ADS)

Di Lella, Santiago; Petruk, Ariel A.; Armiño, Diego J. Alonso de; Álvarez, Rosa M. S.

2010-08-01

Water molecules, rigidly associated to protein surfaces, play a key role in stabilizing biomolecules and participating in their biological functions. Recent studies on the solvation properties of the carbohydrate recognition domain of Galectin-1 by means of molecular dynamic simulations have revealed the existence of several water sites which were well correlated to both the bound water molecules observed in the crystal structure of the protein in the free state and to some of the hydroxyl groups of the carbohydrate ligand observed in the crystal structure of the complexed protein. In this work, we present a study using quantum mechanical methods (B3LYP/6-311++G(3df,3dp)//B3LYP/6-31+G(d)) to determine the energy involved in the binding of these water molecules to specific amino acids in the carbohydrate recognition domain of the protein. By modeling the hydroxyl groups of the carbohydrate by methanol, the energies associated to the local interactions between the ligand and the protein have been evaluated by replacing specific water molecules with methanol. The values of the binding energies have been compared to those previously obtained by the molecular dynamic method.

Reactivity of formic acid (HCOOD and DCOOH) at uranium and UO 2.0 surfaces

NASA Astrophysics Data System (ADS)

Manner, William L.; Lloyd, Jane A.; Paffett, Mark T.

1999-10-01

Interactions of DCOOH and HCOOD with uranium and UO 2.0 surfaces have been examined using surface-specific techniques of thermal desorption mass spectroscopy (TDMS), X-ray photoelectron spectroscopy (XPS), and static secondary ion mass spectroscopy (SSIMS). On the clean uranium surface, formate is the predominant product following formic acid adsorption at 100 K. A wide range of products is observed after annealing to 200 K, including formate, hydroxyl, O ads, and H ads (D ads) groups. Adsorbed formate decomposes by 300 K increasing the concentration of the remaining surface products. Surface-adsorbed carbon following TDMS measurements remains as the carbide, as indicated from XPS and SSIMS measurements. The only gaseous species created in high yields from the clean surface upon annealing are H 2, HD, and D 2. On the oxide surface (UO 2.0), adsorbed formate groups are more stable toward dissociation in comparison with the clean uranium surface. Between 100 and 300 K the predominant species on the UO 2.0 surface are surface formate and hydroxyl groups. Hydroxyl groups react between 300 and 350 K to release water from the surface. Adsorbed formate groups decompose between 400 and 500 K to release CO and H 2CO (D 2CO) groups from the oxide surface. Carbon was not detected on the oxide surface by XPS or SSIMS after annealing to 500 K, indicating that all carbon-containing species either desorb in the form of CO-containing products or migrate into the surface.

Effect of green tea catechins and hydrolyzable tannins on benzo[a]pyrene-induced DNA adducts and structure-activity relationship.

PubMed

Cao, Pengxiao; Cai, Jian; Gupta, Ramesh C

2010-04-19

Green tea catechins and hydrolyzable tannins are gaining increasing attention as chemopreventive agents. However, their mechanism of action is poorly understood. We investigated the effects of four green tea catechins and two hydrolyzable tannins on microsome-induced benzo[a]pyrene (BP)-DNA adducts and the possible structure-activity relationship. BP (1 microM) was incubated with rat liver microsomes and DNA in the presence of the test compound (1-200 microM) or vehicle. The purified DNA was analyzed by (32)P-postlabeling. The inhibitory activity of the catechins was in the following descending order: epigallocatechin gallate (IC(50) = 16 microM) > epicatechin gallate (24 microM) > epigallocatechin (146 microM) > epicatechin (462 microM), suggesting a correlation between the number of adjacent aromatic hydroxyl groups in the molecular structure and their potencies. Tannic acid (IC(50) = 4 microM) and pentagalloglucose (IC(50) = 26 microM) elicited as much DNA adduct inhibitory activity as the catechins or higher presumably due to the presence of more functional hydroxyl groups. To determine if the activity of these compounds was due to direct interaction of phenolic groups with electrophilic metabolite(s) of BP, DNA was incubated with anti-benzo[a]pyrene-7,8-diol-9,10-epoxide (anti-BPDE) (0.5 microM) in the presence of test compounds (200 microM) or vehicle. Significant inhibition of DNA adduct formation was found (tannic acid > pentagalloglucose > epigallocatechin gallate > epicatechin gallate). This notion was confirmed by analysis of the reaction products of anti-BPDE with the catechins and pentagalloglucose by electrospray ionization mass spectrometry and liquid chromatography-mass spectrometry. In conclusion, our data demonstrate that green tea catechins and the hydrolyzable tannins are highly effective in inhibiting BP-DNA adduct formation at least, in part, due to direct interaction of adjacent hydroxyl groups in their structures and that the activity is higher with an increasing number of functional hydroxyl groups.

Effect of Green Tea Catechins and Hydrolyzable Tannins on Benzo[a]pyrene-Induced DNA Adducts and Structure–Activity Relationship

PubMed Central

Cao, Pengxiao; Cai, Jian; Gupta, Ramesh C.

2016-01-01

Green tea catechins and hydrolyzable tannins are gaining increasing attention as chemopreventive agents. However, their mechanism of action is poorly understood. We investigated the effects of four green tea catechins and two hydrolyzable tannins on microsome-induced benzo[a]pyrene (BP)–DNA adducts and the possible structure–activity relationship. BP (1 μM) was incubated with rat liver microsomes and DNA in the presence of the test compound (1–200 μM) or vehicle. The purified DNA was analyzed by 32P-postlabeling. The inhibitory activity of the catechins was in the following descending order: epigallocatechin gallate (IC50 = 16 μM) > epicatechin gallate (24 μM) > epigallocatechin (146 μM) > epicatechin (462 μM), suggesting a correlation between the number of adjacent aromatic hydroxyl groups in the molecular structure and their potencies. Tannic acid (IC50 = 4 μM) and pentagalloglucose (IC50 = 26 μM) elicited as much DNA adduct inhibitory activity as the catechins or higher presumably due to the presence of more functional hydroxyl groups. To determine if the activity of these compounds was due to direct interaction of phenolic groups with electrophilic metabolite(s) of BP, DNA was incubated with anti-benzo[a]pyrene-7,8-diol-9,10-epoxide (anti-BPDE) (0.5 μM) in the presence of test compounds (200 μM) or vehicle. Significant inhibition of DNA adduct formation was found (tannic acid > pentagalloglucose > epigallocatechin gallate > epicatechin gallate). This notion was confirmed by analysis of the reaction products of anti-BPDE with the catechins and pentagalloglucose by electrospray ionization mass spectrometry and liquid chromatography–mass spectrometry. In conclusion, our data demonstrate that green tea catechins and the hydrolyzable tannins are highly effective in inhibiting BP–DNA adduct formation at least, in part, due to direct interaction of adjacent hydroxyl groups in their structures and that the activity is higher with an increasing number of functional hydroxyl groups. PMID:20218540

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cheng, Chiu Tung; Chan, Man Nin; Wilson, Kevin R.

Oxygenated organic molecules are abundant in atmospheric aerosols and are transformed by oxidation reactions near the aerosol surface by gas-phase oxidants such as hydroxyl (OH) radicals. To gain better insights into how the structure of an organic molecule, particularly in the presence of hydroxyl groups, controls the heterogeneous reaction mechanisms of oxygenated organic compounds, this study investigates the OH-radical initiated oxidation of aqueous tartaric acid (C 4 H 6 O 6 ) droplets using an aerosol flow tube reactor. The molecular composition of the aerosols before and after reaction is characterized by a soft atmospheric pressure ionization source (Direct Analysismore » in Real Time) coupled with a high-resolution mass spectrometer. The aerosol mass spectra reveal that four major reaction products are formed: a single C 4 functionalization product (C 4 H 4 O 6 ) and three C 3 fragmentation products (C 3 H 4 O 4 , C 3 H 2 O 4 , and C 3 H 2 O 5 ). The C 4 functionalization product does not appear to originate from peroxy radical self-reactions but instead forms via an α-hydroxylperoxy radical produced by a hydrogen atom abstraction by OH at the tertiary carbon site. The proximity of a hydroxyl group to peroxy group enhances the unimolecular HO 2 elimination from the α-hydroxylperoxy intermediate. This alcohol-to-ketone conversion yields 2-hydroxy-3-oxosuccinic acid (C 4 H 4 O 6 ), the major reaction product. While in general, C-C bond scission reactions are expected to dominate the chemistry of organic compounds with high average carbon oxidation states (OS C ), our results show that molecular structure can play a larger role in the heterogeneous transformation of tartaric acid (OS C = 1.5). These results are also compared with two structurally related dicarboxylic acids (succinic acid and 2,3-dimethylsuccinic acid) to elucidate how the identity and location of functional groups (methyl and hydroxyl groups) alter heterogeneous reaction mechanisms.« less

Biotransformation of fluorophenyl pyridine carboxylic acids by the model fungus Cunninghamella elegans.

PubMed

Palmer-Brown, William; Dunne, Brian; Ortin, Yannick; Fox, Mark A; Sandford, Graham; Murphy, Cormac D

2017-09-01

1. Fluorine plays a key role in the design of new drugs and recent FDA approvals included two fluorinated drugs, tedizolid phosphate and vorapaxar, both of which contain the fluorophenyl pyridyl moiety. 2. To investigate the likely phase-I (oxidative) metabolic fate of this group, various fluorinated phenyl pyridine carboxylic acids were incubated with the fungus Cunninghamella elegans, which is an established model of mammalian drug metabolism. 3.  19 F NMR spectroscopy established the degree of biotransformation, which varied depending on the position of fluorine substitution, and gas chromatography-mass spectrometry (GC-MS) identified alcohols and hydroxylated carboxylic acids as metabolites. The hydroxylated metabolites were further structurally characterised by nuclear magnetic resonance spectroscopy (NMR), which demonstrated that hydroxylation occurred on the 4' position; fluorine in that position blocked the hydroxylation. 4. The fluorophenyl pyridine carboxylic acids were not biotransformed by rat liver microsomes and this was a consequence of inhibitory action, and thus, the fungal model was crucial in obtaining metabolites to establish the mechanism of catabolism.

Salt permeation and exclusion in hydroxylated and functionalized silica pores.

PubMed

Leung, Kevin; Rempe, Susan B; Lorenz, Christian D

2006-03-10

We use combined ab initio molecular dynamics (AIMD), grand canonical Monte Carlo, and molecular dynamics techniques to study the effect of pore surface chemistry and confinement on the permeation of salt into silica nanopore arrays filled with water. AIMD shows that 11.6 A diameter hydroxylated silica pores are relatively stable in water, whereas amine groups on functionalized pore surfaces abstract silanol protons, turning into NH3+. Free energy calculations using an ab initio parametrized force field show that the hydroxylated pores strongly attract Na+ and repel Cl- ions. Pores lined with NH3+ have the reverse surface charge polarity. Finally, studies of ions in carbon nanotubes suggest that hydration of Cl- is more strongly frustrated by pure confinement effects than Na+.

Raman and IR Spectroscopic Study of Hydrous Pyroxenes

NASA Astrophysics Data System (ADS)

Kung, J.; Li, C.; Stalder, R.; Inoue, T.; Chuang, S.; Balfan-Casanova, N.; Skogby, H.

2017-12-01

Pyroxene group is one of major composed minerals at upper mantle and is nominally anhydrous mineral (NAM), in terms of its crystal chemistry. The analysis of field specimens showed the mantle-derived pyroxene phase containing some amount of hydrogen within crystal structure, the major incorporation mechanism to be as hydroxyl, OH¯, which chemical component treats as `water', H2O. Compared with the other mantle-derived olivine and garnet, the crystal chemistry of pyroxene phases (opx and cpx) is more complex that can result in different OH¯ bonding environments that would greatly affect the geophysics-interested physical properties, for example, elasticity and transport properties. In order to understand how the hydroxyl bonding condition with different composition of opx and cpx in this study, IR and Raman spectroscopies were employed to investigate the lattice modes and hydroxyl-bonding environments with different composition and crystal structures. The studied pyroxene specimens included natural hydrous pyroxenes and synthesized hydrous orthoenstatite (OEN) at high pressure and temperature (4-7 GPa, 1300-1400°C). The measured IR band range was carried out from 2800 to 3600 cm-1 and the Raman range from 50 to 3600 cm-1. The analysis showed that the band of 3600 cm-1 is the major feature in natural opx specimens but its intensity would be varied in different crystal orientation. For synthesized OEN, the number of observed IR band is higher than that reported in previous studies. The common major bands observed in natural cpx are around 3500 cm-1. The Raman measurement of studied specimen is to characterize the variation of Raman mode as function of composition and possible Raman active hydroxyl-related modes. In this meeting the results will be presented and discussed.

Structure-activity relationship of carbamate-linked cationic lipids bearing hydroxyethyl headgroup for gene delivery.

PubMed

Zhi, Defu; Zhang, Shubiao; Qureshi, Farooq; Zhao, Yinan; Cui, Shaohui; Wang, Bing; Chen, Huiying; Yang, Baoling; Zhao, Defeng

2013-12-01

A novel series of carbamate-linked cationic lipids containing hydroxyl headgroup were synthesized and included in formulations for transfection assays. The DNA-lipid complexes were characterized for their ability to bind DNA, their size, ζ-potential and cytotoxicity. Compared with our previously reported cationic transfection lipid DDCDMA lacking the hydroxyl group and the commercially available, these cationic liposomes exhibited relatively higher transfection efficiency. Copyright © 2013 Elsevier B.V. All rights reserved.

Chain-breaking antioxidant activity of hydroxylated and methoxylated magnolol derivatives: the role of H-bonds.

PubMed

Baschieri, Andrea; Pulvirenti, Luana; Muccilli, Vera; Amorati, Riccardo; Tringali, Corrado

2017-07-26

Chemical modification of magnolol, an uncommon dimeric neolignan contained in Magnolia genus trees, provides a unique array of polyphenols having interesting biological activity potentially related to radical scavenging. The chain-breaking antioxidant activity of four new hydroxylated and methoxylated magnolol derivatives was explored by experimental and computational methods. The measurement of the rate constant of the reaction with ROO˙ radicals (k inh ) in an apolar solvent showed that the introduction of hydroxyl groups ortho to the phenolic OH in magnolol increased the k inh value, being 2.4 × 10 5 M -1 s -1 and 3.3 × 10 5 M -1 s -1 for the mono and the dihydroxy derivatives respectively (k inh of magnolol is 6.1 × 10 4 M -1 s -1 ). The di-methoxylated derivative is less reactive than magnolol (k inh = 1.1 × 10 4 M -1 s -1 ), while the insertion of both hydroxyl and methoxyl groups showed no effect (6.0 × 10 4 M -1 s -1 ). Infrared spectroscopy and theoretical calculations allowed a rationalization of these results and pointed out the crucial role of intramolecular H-bonds. We also show that a correct estimation of the rate constant of the reaction with ROO˙ radicals, by using BDE(OH) calculations, requires that the geometry of the radical is as close as possible to that of the parent phenol.

Conformational analyses of 2,3-dihydroxypropanoic acid as a function of solvent and ionization state as determined by NMR spectroscopy.

PubMed

Drake, Michael D; Harsha, Alex K; Terterov, Sergei; Roberts, John D

2006-03-01

Vicinal (1)H--(1)H coupling constants were used to determine the conformational preferences of 2,3-dihydroxypropanoic acid (1) (DL-glyceric acid) in various solvents and its different carboxyl ionization states. The stereospecific assignments of J(12) and J(13) were confirmed through the point-group substitution of the C-3 hydrogen with deuterium, yielding rac-(2SR,3RS)-[3-(2)H]-1, and the observation of only J(13) in the (1)H NMR spectra. While hydrogen bonding and steric strain may be expected to drive the conformational equilibrium, their role is overshadowed by a profound gauche effect between the vicinal hydroxyl groups that mimics other substituted ethanes, such as 1,2-ethanediol and 1,2-difluoroethane. At low pH, the conformational equilibrium is heavily weighted toward the gauche-hydroxyl rotamers with a range of 81% in DMSO-d(6) to 92% in tert-butyl alcohol-d(10). At high pH, the equilibrium exhibits a larger dependence upon the polarity and solvating capability of the medium, although the gauche effect still dominates in D(2)O, 1,4-dioxane-d(8), methanol-d(4), and ethanol-d(6) (96, 89, 85, and 83% gauche-hydroxyls respectively). The observed preference for the gauche-hydroxyl rotamers is believed to stem primarily from hyperconjugative sigma(C--H) --> sigma*(C--OH) interactions.

Modulating optical properties of graphene oxide: role of prominent functional groups.

PubMed

Johari, Priya; Shenoy, Vivek B

2011-09-27

To modulate the electronic and optical properties of graphene oxide via controlled deoxidation, a proper understanding of the role of the individual functional group in determining these properties is required. We, therefore, have performed ab initio density functional theory based calculations to study the electronic and optical properties of model structures of graphene oxide with different coverages and compositions. In particular, we considered various concentrations of major functional groups like epoxides, hydroxyls, and carbonyls, which mainly consititute the graphene oxide and the reduced graphene oxide. Our calculated electron energy loss spectra (EELS) demonstrate the π plasmon peak to be less sensitive, while π + σ plasmon is found to have a significant blue shift of about 1.0-3.0 eV, when the concentration of epoxy and hydroxyl functional groups in graphene oxide vary from 25% to 75%. However, the increase in carbonyl groups in the center of the graphene sheet creates holes, which lead to the red shift of the EELS. In the case of 37.5% of oxygen-to-carbon ratio, we find the π plasmon peak to be shifted by roughly 1.0 eV as compared to that of the pristine graphene. Our results agree well with the experimental findings which suggest a blue shift in the EELS of graphene oxide and an absorption feature due to a π electron transition of the carbonyl groups at a lower energy than that of epoxy and hydroxyl groups. We also show that the increase in the width of the hole created by the carbonyl groups significantly decreases the optical gap and opens the band gap, and thus, we argue that reduced graphene oxide with mostly carbonyl groups could be a useful material for developing tunable opto-electronic nanodevices. © 2011 American Chemical Society

Biosynthesis of the carbohydrate antigenic determinants, Globo H, blood group H, and Lewis b: a role for prostate cancer cell alpha1,2-L-fucosyltransferase.

PubMed

Chandrasekaran, E V; Chawda, Ram; Locke, Robert D; Piskorz, Conrad F; Matta, Khushi L

2002-03-01

Prostate carcinoma LNCaP cells were unique among several human cancer cell lines which include two other prostate cancer cell lines, PC-3 and DU-145, in expressing alpha1,2-L-fucosyltransferase (FT) as an exclusive FT activity. Affinity gel-GDP and Sephacryl S100 HR columns were used for a partial purification of this enzyme from 3.9 x 10(9) LNCaP cells (approximately 200-fold; 40% yield). The K(m) value (2.7 mM) for the LacNAc type 2 acceptor was quite similar to the one reported for the cloned blood group H gene-specified alpha1,2-FT [Chandrasekaran et al. (1996) Biochemistry 35, 8914-8924]. N-Ethylmaleimide was a potent inhibitor (K(i ) 12.5 microM). The enzyme showed four-fold acceptor preference for the LacNAc type 2 unit in comparison to the T-hapten in mucin core 2 structure. Its main features were similar to those of the cloned enzyme: (1) C-6 sulfation of terminal Gal in the LacNAc unit increased the acceptor efficiency, whereas C-6 sialylation abolished acceptor ability; (2) C-6 sulfation of GlcNAc in LacNAc type 2 decreased by 80% the acceptor ability, whereas LacNAc type 1 was unaffected; (3) Lewis x did not serve as an acceptor; (4) the C-4 hydroxyl rather than the C-6 hydroxyl group of the GlcNAc moiety in LacNAc type1 was essential for activity; and (5) the acrylamide copolymer of Galbeta1,3GlcNAcbeta-O-Al was the best acceptor among the acrylamide copolymers. Additionally, highly significant biological features of alpha1,2FT were identified in the present study. The synthesis of Globo H and Lewis b determinants became evident from the fact that Galbeta1,3GalNAcbeta1,3Galalpha-O-Me and Galbeta1,3(Fucalpha1,4)Glc-NAcbeta1,3Galbeta-O-Me served as high-affinity acceptors for this enzyme. Further, D-Fucbeta1,3Gal-NAcbeta1,3Galalpha-O-Me was a very efficient acceptor, indicating that the C-6 hydroxyl group of the terminal Gal moiety in Globo H is not essential for the enzyme activity. Thus, the present study was able to demonstrate three different catalytic roles of LNCaP alpha1,2-FT, namely, the expressions of blood group H, Lewis b from Lewis a, and Globo H.

New halogenated phenylcoumarins as tyrosinase inhibitors.

PubMed

Matos, Maria João; Santana, Lourdes; Uriarte, Eugenio; Delogu, Giovanna; Corda, Marcella; Fadda, Maria Benedetta; Era, Benedetta; Fais, Antonella

2011-06-01

With the aim to find out structural features for the tyrosinase inhibitory activity, in the present communication we report the synthesis and pharmacological evaluation of a new series of phenylcoumarin derivatives with different number of hydroxyl or ether groups and bromo substituent in the scaffold. The synthesized compounds 5-12 were evaluated as mushroom tyrosinase inhibitors showing, two of them, lower IC(50) than the umbelliferone. Compound 12 (IC(50)=215 μM) is the best tyrosinase inhibitor of this series. Copyright © 2011 Elsevier Ltd. All rights reserved.

Aliphatic peptidyl hydroperoxides as a source of secondary oxidation in hydroxyl radical protein footprinting

PubMed Central

Saladino, Jessica; Liu, Mian; Live, David; Sharp, Joshua S.

2009-01-01

Hydroxyl radical footprinting is a technique for studying protein structure and binding that entails oxidizing a protein system of interest with diffusing hydroxyl radicals, and then measuring the amount of oxidation of each amino acid. One important issue in hydroxyl radical footprinting is limiting amino acid oxidation by secondary oxidants to prevent uncontrolled oxidation which can cause amino acids to appear more solvent accessible than they really are. Previous work suggested that hydrogen peroxide was the major secondary oxidant of concern in hydroxyl radical footprinting experiments; however, even after elimination of all hydrogen peroxide, some secondary oxidation was still detected. Evidence is presented for the formation of peptidyl hydroperoxides as the most abundant product upon oxidation of aliphatic amino acids. Both reverse phase liquid chromatography and catalase treatment were shown to be ineffective at eliminating peptidyl hydroperoxides. The ability of these peptidyl hydroperoxides to directly oxidize methionine is demonstrated, suggesting the value of methionine amide as an in situ protectant. Hydroxyl radical footprinting protocols require the use of an organic sulfide or similar peroxide scavenger in addition to removal of hydrogen peroxide in order to successfully eradicate all secondary oxidizing species and prevent uncontrolled oxidation of sulfur-containing residues. PMID:19278868

Evaporation and Hydrocarbon Chain Conformation of Surface Lipid Films.

PubMed

Sledge, Samiyyah M; Khimji, Hussain; Borchman, Douglas; Oliver, Alexandria L; Michael, Heidi; Dennis, Emily K; Gerlach, Dylan; Bhola, Rahul; Stephen, Elsa

2016-10-01

The inhibition of the rate of evaporation (R evap ) by surface lipids is relevant to reservoirs and dry eye. Our aim was to test the idea that lipid surface films inhibit R evap . R evap were determined gravimetrically. Hydrocarbon chain conformation and structure were measured using a Raman microscope. Six 1-hydroxyl hydrocarbons (11-24 carbons in length) and human meibum were studied. Reflex tears were obtained from a 62-year-old male. The Raman scattering intensity of the lipid film deviated by about 7 % for hydroxyl lipids and varied by 21 % for meibum films across the entire film at a resolution of 5 μm 2 . All of the surface lipids were ordered. R evap of the shorter chain hydroxyl lipids were slightly (7%) but significantly lower compared with the longer chain hydroxyl lipids. R evap of both groups was essentially similar to that of buffer. A hydroxyl lipid film did not influence R evap over an estimated average thickness range of 0.69 to >6.9 μm. R evap of human tears and buffer with and without human meibum (34.4 μm thick) was not significantly different. R evap of human tears was not significantly different from buffer. Human meibum and hydroxyl lipids, regardless of their fluidity, chain length, or thickness did not inhibit R evap of buffer or tears even though they completely covered the surface. It is unlikely that hydroxyl lipids can be used to inhibit R evap of reservoirs. Our data do not support the widely accepted (yet unconfirmed) idea that the tear film lipid layer inhibits R evap of tears. Copyright © 2016 Elsevier Inc. All rights reserved.

Synthesis and characterization of two dehydroacetic acid derivatives and molybdenum(V) complexes: an NMR and crystallographic study

NASA Astrophysics Data System (ADS)

Cindrić, Marina; Vrdoljak, Višnja; Kajfež Novak, Tanja; Ćurić, Manda; Brbot-Šaranović, Ana; Kamenar, Boris

2004-09-01

Two enaminones ethyl 4-(4-hydroxy-6-methyl-2 H-pyran-2-on-3-yl)-2-(tryptamino)-4-oxo-2-butenoate ( HL1) and 3-(1-tryptaminoetylidene)-6-methyl-2 H-pyran-2,4(3H)-dione ( HL2) have been prepared by the reactions of tryptamine with 2-hydroxy-4-(4-hydroxy)-6-methyl)-2 Hbb-pyrane-2-on-3-yl)-4-oxo-2-butenoate (ehmpb) or with dehydroacetic acid (dha). The NMR spectroscopy confirmed that both tautomeric forms of HL1: endo-enol (tautomer A with hydroxyl group at position 4) and exo-enol form (tautomer B with hydroxyl group at position 7) are present in the DMSO- d6 solution. The molecular and crystal structure as well as the NMR data of HL2 showed that the condensation of dha and tryptamine occurs at acetyl-carbonyl and not at the pyrone-carbonyl group. Also new dinuclear [Mo 2O 4(L 1) 2(CH 3OH) 2] ( 1) and hexanuclear molybdenum(V) complexes (C 10H 12NH)[Mo 6O 12(OCH 3) 4(acac) 3] ( 2) have been prepared by the reactions of [Mo 2O 3(acac) 4] (acac=acetilacetonate ion) with HL1 or with tryptamine. All compounds have been characterized also by means of elemental analyses, IR spectroscopy as well as by thermal analyses.

CYP3A5 Contributes significantly to CYP3A-mediated drug oxidations in liver microsomes from Japanese subjects.

PubMed

Yamaori, Satoshi; Yamazaki, Hiroshi; Iwano, Shunsuke; Kiyotani, Kazuma; Matsumura, Keiko; Honda, Goro; Nakagawa, Kazuko; Ishizaki, Takashi; Kamataki, Tetsuya

2004-04-01

The purpose of this study was to evaluate a contribution of polymorphic cytochrome P450 (CYP) 3A5 to the oxidation of diltiazem, midazolam and testosterone by liver microsomes from Japanese subjects. Twenty-seven liver samples were classified into three groups according to the CYP3A5 genotypes; CYP3A5(*)1/(*)1 (n=3), (*)1/(*)3 (n=12) and (*)3/(*)3 (n=12). The results of genotyping and immunochemical quantitation of CYP3A5 protein showed a good accordance between the CYP3A5 genotype and CYP3A5 content but not CYP3A4 content in liver microsomes. The expression levels of hepatic CYP3A5 protein ranged from 20 to 60% of the sum of CYP3A4 and CYP3A5 contents in subjects with at least one wild type allele ((*)1). The CYP3A5 contents correlated well with liver microsomal activities of diltiazem N-demethylation, midazolam 1'- and 4-hydroxylations and testosterone 6beta-hydroxylation among subjects carrying at least one (*)1 allele. In addition, the correlation coefficients of CYP3A5 contents with the rates of diltiazem N-demethylation, midazolam 1'-hydroxylation and testosterone 6beta- hydroxylation were higher than those of CYP3A4, although the value of CYP3A5 with the midazolam 4-hydroxylation rate was similar to that of CYP3A4. Kinetic analyses revealed a biphasic diltiazem N-demethylation in liver microsomes from subjects carrying the (*)1 allele. The apparent V(max)/K(m) values for recombinant CYP3A5 indicated the greater contributions to diltiazem N-demethylation and midazolam 1'-hydroxylation as compared with CYP3A4. These results suggest that polymorphic CYP3A5 contributes markedly to the drug oxidations, particularly diltiazem N-demethylation, midazolam 1'- hydroxylation and testosterone 6beta-hydroxylation by liver microsomes from Japanese subjects.

Effect of Bovine Serum Albumin Treatment on the Aging and Activity of Antibodies in Paper Diagnostics.

PubMed

Huang, Ziwei; Gengenbach, Thomas; Tian, Junfei; Shen, Wei; Garnier, Gil

2018-01-01

Paper and cellulosic films are used in many designs of low-cost diagnostics such as paper-based blood grouping devices. A major issue limiting their commercialization is the short stability of the functional biomolecules. To address this problem, the effect of relative humidity (RH) and bovine serum albumin (BSA) on the antibody bioactivity and the surface chemical composition of a paper blood typing biodiagnostic were studied. An IgM blood typing antibody was physisorbed from solution onto paper - with or without BSA pretreatment, and aged for periods up to 9 weeks under various conditions with a series of RH. The blood typing efficiency of the antibodies and the substrate surface chemical composition were analyzed by image analysis and X-ray photoelectron spectroscopy (XPS), respectively. This study tests two hypotheses. The first is that the hydroxyl groups in paper promote antibody denaturation on paper; the second hypothesis is that proteins such as BSA can partially block the hydroxyl groups within paper, thus preserving antibody bioactivity. Results show that high RH is detrimental to antibody longevity on paper, while BSA can block hydroxyl groups and prolong antibody longevity by almost an order of magnitude-regardless of humidity. This study opens up new engineering concepts to develop robust and marketable paper diagnostics. The simplest is to store paper and antibody based diagnostics in moisture proof packages.

Effect of Bovine Serum Albumin Treatment on the Aging and Activity of Antibodies in Paper Diagnostics

NASA Astrophysics Data System (ADS)

Huang, Ziwei; Gengenbach, Thomas; Tian, Junfei; Shen, Wei; Garnier, Gil

2018-05-01

Paper and cellulosic films are used in many designs of low-cost diagnostics such as paper-based blood grouping devices. A major issue limiting their commercialization is the short stability of the functional biomolecules. To address this problem, the effect of relative humidity (RH) and bovine serum albumin (BSA) on the antibody bioactivity and the surface chemical composition of a paper blood typing biodiagnostic were studied. An IgM blood typing antibody was physisorbed from solution onto paper - with or without BSA pretreatment, and aged for periods up to 9 weeks at room temperature and under different RH conditions. The blood typing efficiency of the antibodies and the substrate surface chemical composition were analyzed by image analysis and X-ray photoelectron spectroscopy (XPS), respectively. This study tests two hypotheses. The first is that the hydroxyl groups in paper promote antibody denaturation on paper; the second hypothesis is that proteins such as BSA can partially block the hydroxyl groups with paper, thus preserving antibody bioactivity. Results show that high RH is detrimental to antibody longevity on paper, while BSA can block hydroxyl groups and prolong antibody longevity by almost an order of magnitude – regardless of humidity. This study opens up new engineering concepts to develop robust and marketable paper diagnostics. The simplest is to store paper and antibody based diagnostics in moisture proof packages.

Removal behaviors of sulfamonomethoxine and its degradation intermediates in fresh aquaculture wastewater using zeolite/TiO2 composites.

PubMed

Nomura, Youhei; Fukahori, Shuji; Fukada, Haruhisa; Fujiwara, Taku

2017-10-15

Removal efficiencies of sulfamonomethoxine (SMM) and its degradation intermediates formed by treatment with zeolite/TiO 2 composites through adsorption and photocatalysis were investigated in fresh aquaculture wastewater (FAWW). Coexistent substances in the FAWW showed no inhibitory effects against SMM adsorption. Although coexistent substances in the FAWW inhibited the photocatalytic decomposition of SMM, the composites mitigated the inhibition, possibly because of concentration of SMM on their surface by adsorption. LC/MS/MS analyses revealed that hydroxylation of amino phenyl and pyrimidinyl portions, transformation of the amino group in the amino phenyl portion into a nitroso group, and substitution of the methoxy group with a hydroxyl group occurring in the initial reaction resulted in the formation of various intermediates during the photocatalysis of SMM. All detected intermediates had a ring structure, and almost all intermediates disappeared at the same time SMM was completely decomposed. Ph-OH formed by hydroxylation of the phenyl portion was detected upon decomposition of SMM during photocatalysis. The removal of Ph-OH by the composites proceeded more rapidly than that by TiO 2 alone under ultraviolet irradiation. The SMM and Ph-OH were completely degraded by the composites within 30min, showing that the zeolite/TiO 2 composites were effective in removing SMM and its intermediates from FAWW. Copyright © 2017 Elsevier B.V. All rights reserved.

Energy for Wild-Type Acetylcholine Receptor Channel Gating from Different Choline Derivatives

PubMed Central

Bruhova, Iva; Gregg, Timothy; Auerbach, Anthony

2013-01-01

Agonists, including the neurotransmitter acetylcholine (ACh), bind at two sites in the neuromuscular ACh receptor channel (AChR) to promote a reversible, global change in protein conformation that regulates the flow of ions across the muscle cell membrane. In the synaptic cleft, ACh is hydrolyzed to acetate and choline. Replacement of the transmitter’s ester acetyl group with a hydroxyl (ACh→choline) results in a +1.8 kcal/mol reduction in the energy for gating generated by each agonist molecule from a low- to high-affinity change of the transmitter binding site (ΔGB). To understand the distinct actions of structurally related agonist molecules, we measured ΔGB for 10 related choline derivatives. Replacing the hydroxyl group of choline with different substituents, such as hydrogen, chloride, methyl, or amine, increased the energy for gating (i.e., it made ΔGB more negative relative to choline). Extending the ethyl hydroxide tail of choline to propyl and butyl hydroxide also increased this energy. Our findings reveal the amount of energy that is available for the AChR conformational change provided by different, structurally related agonists. We speculate that a hydrogen bond between the choline hydroxyl and the backbone carbonyl of αW149 positions this agonist’s quaternary ammonium group so as to reduce the cation-π interaction between this moiety and the aromatic groups at the binding site. PMID:23442907

A novel mechanism of sugar selection utilized by a human X-family DNA polymerase.

PubMed

Brown, Jessica A; Fiala, Kevin A; Fowler, Jason D; Sherrer, Shanen M; Newmister, Sean A; Duym, Wade W; Suo, Zucai

2010-01-15

During DNA synthesis, most DNA polymerases and reverse transcriptases select against ribonucleotides via a steric clash between the ribose 2'-hydroxyl group and the bulky side chain of an active-site residue. In this study, we demonstrated that human DNA polymerase lambda used a novel sugar selection mechanism to discriminate against ribonucleotides, whereby the ribose 2'-hydroxyl group was excluded mostly by a backbone segment and slightly by the side chain of Y505. Such steric clash was further demonstrated to be dependent on the size and orientation of the substituent covalently attached at the ribonucleotide C2'-position. Copyright 2009 Elsevier Ltd. All rights reserved.

Photoactivatable Rhodamine Spiroamides and Diazoketones Decorated with "Universal Hydrophilizer" or Hydroxyl Groups.

PubMed

Roubinet, Benoit; Bischoff, Matthias; Nizamov, Shamil; Yan, Sergey; Geisler, Claudia; Stoldt, Stefan; Mitronova, Gyuzel Y; Belov, Vladimir N; Bossi, Mariano L; Hell, Stefan W

2018-05-11

Photoactivatable rhodamine spiroamides and spirocyclic diazoketones emerged recently as synthetic markers applicable in multicolor superresolution microscopy. However, their applicability in single molecule localization microscopy (SMLM) is often limited by aggregation, unspecific adhesion and low reactivity caused by insufficient solubility and precipitation from aqueous solutions. We report here two synthetic modifications increasing the polarity of compact polycyclic and hydrophobic labels decorated with a reactive group: attachment of 3-sulfo-L-alanyl - beta-alanine dipeptide (a "universal hydrophilizer") or allylic hydroxylation in photosensitive rhodamine diazoketones (and spiroamides). The superresolution images of tubulin and keratin filaments in fixed and living cells exemplify the performance of "blinking" spiroamides derived from N,N,N',N'-tetramethyl rhodamine.

The effects of certain glycols, substituted glycols and related organic solvents on the thermal stability of soluble collagen

PubMed Central

Hart, G. J.; Russell, A. E.; Cooper, D. R.

1971-01-01

The effects of a number of related diols, substituted diols and glycerol on the thermal stability of acid-soluble calf skin collagen were investigated. Thermal transition temperatures were determined by optical rotation measurement. Short-chain diols with terminal hydroxyl groups, i.e. ethylene glycol and propane-1,3-diol, stabilized the protein at all accessible concentrations. Stabilization was also observed with glycerol and diethylene glycol. Higher homologues in the diol series produced various effects, as did hydroxyl-group positional isomerism. Monoalkyl substitution of diols progressively lowered the denaturation temperature of collagen. Results are discussed in relation to possible mechanisms of perturbant action. PMID:5169191

H-Bonding Networks in Sugar Alcohols: Identifying Glucophores?

NASA Astrophysics Data System (ADS)

Alonso, E. R.; Mata, Santiago; Cabezas, Carlos; Peña, Isabel; Alonso, José L.

2016-06-01

The conformational behaviour of sorbitol and dulcitol has been investigated for the first time using a combination of chirped pulse Fourier transform microwave spectroscopy (CP-FTMW) coupled with a laser ablation (LA) source. The observed conformers have been found to be overstabilised by cooperative networks of intramolecular hydrogen bonds between vicinal hydroxyl groups stretching throughout the whole molecule. A common structural signature - involving hydroxyl groups in the H-bond - has been characterized and ascribed to the glucophore's AH and B sites in accordance with Shallenberger's old proposal. R. S. Shallenberger, T. E. Acree, Nature, 1967, 216, 480-482 R. S. Shallenberger, T. E. Acree, C. Y. Lee, Nature, 1969, 221, 555-556

Methemoglobinemia Hemotoxicity of Some Antimalarial 8-Aminoquinoline Analogues and Their Hydroxylated Derivatives: Density Functional Theory Computation of Ionization Potentials.

PubMed

Ding, Yuanqing; Liu, Haining; Tekwani, Babu L; Nanayakkara, N P Dhammika; Khan, Ikhlas A; Walker, Larry A; Doerksen, Robert J

2016-07-18

The administration of primaquine (PQ), an essential drug for the treatment and radical cure of malaria, can lead to methemoglobin formation and life-threatening hemolysis for glucose-6-phosphate dehydrogenase deficient patients. The ionization potential (IP, a quantitative measure of the ability to lose an electron) of the metabolites generated by antimalarial 8-aminoquinoline (8-AQ) drugs like PQ has been believed to be correlated in part to this methemoglobinemia hemotoxicity: the lower the IP of an 8-AQ derivative, the higher the concentration of methemoglobin generated. In this work, demethoxylated primaquine (AQ02) was employed as a model, by intensive computation at the B3LYP-SCRF(PCM)/6-311++G**//B3LYP/6-31G** level in water, to study the effects of hydroxylation at various positions on the ionization potential. Compared to the parent AQ02, the IPs of AQ02's metabolites hydroxylated at N1', C5, and C7 were lower by 61, 30, and 19 kJ/mol, respectively, while differences in the IP relative to PQ were small for hydroxylation at all other positions. The C6 position, at which the IP of the hydroxylated metabolite was greater than that of AQ02, by 2 kJ/mol, was found to be unique. Several literature and proposed 8-AQ analogues were studied to evaluate substituent effects on their potential to generate methemoglobin, with the finding that hydroxylations at N1' and C5 contribute the most to the potential hemotoxicity of PQ-based antimalarials, whereas hydroxylation at C7 has little effect. Phenoxylation at C5 in PQ-based 8-AQs can block the hydroxylation at C5 and reduce the potential for methemoglobin generation, while -CF3 and chlorines attached to the phenolic ring can further reduce the risk. The H-shift at N1' during the cationization of hydroxylated metabolites of 8-AQs sharply decreased their IPs, but this effect can be significantly reduced by the introduction of an electron-withdrawing group to the quinoline core. The results and this approach may be utilized for the design of safer antimalarial 8-AQ analogues.

Supramolecular structures on silica surfaces and their adsorptive properties.

PubMed

Belyakov, Vladimir N; Belyakova, Lyudmila A; Varvarin, Anatoly M; Khora, Olexandra V; Vasilyuk, Sergei L; Kazdobin, Konstantin A; Maltseva, Tetyana V; Kotvitskyy, Alexey G; Danil de Namor, Angela F

2005-05-01

The study of adsorptive and chemical immobilization of beta-cyclodextrin on a surface of hydroxylated silicas with various porous structure is described. Using IR spectroscopy, thermal gravimetrical analysis with a programmed heating, and chemical analysis of the silica surface, it is shown that the process of adsorption-desorption of beta-cyclodextrin depends on the porous structure of the silica. The reaction of esterification was used for chemical grafting of beta-cyclodextrin on the surface of hydroxylated silicas. Hydrolytic stability of silicas chemically modified by beta-cyclodextrin apparently is explained by simultaneous formation of chemical and hydrogen bonds between surface silanol groups and hydroxyl groups of beta-cyclodextrin. The uptake of the cations Cu(II), Cd(II), and Pb(II) and the anions Cr(VI) and As(V) by silicas modified with beta-cyclodextrin is investigated as a function of equilibrium ion concentrations. The increase of ion uptake and selectivity of ion extraction in comparison with starting silicas is established. It is due to the formation of surface inclusion complexes of the "host-guest" type in which one molecule of beta-cyclodextrin interacts simultaneously with several ions.

Surface segregation of additives on SnO 2 based powders and their relationship with macroscopic properties

NASA Astrophysics Data System (ADS)

Pereira, Gilberto J.; Castro, Ricardo H. R.; Hidalgo, Pilar; Gouvêa, Douglas

2002-07-01

Surface properties of ceramic powders frequently play an important role in producing high-quality, high-performance, and reliable ceramic products. These properties are related to the surface bond types and interactions with the surroundings. Oxide surfaces generally contain adsorbed hydroxyl groups and modifications in the chemical composition of the surface may be studied by infrared spectroscopy. In this work, we prepared SnO 2 containing Fe or Mg ions by organic chemical route derived from Pechini's method. The prepared powders were characterized by infrared spectroscopy (FT-IR), X-ray diffraction (XRD), dynamic electrophoretic mobility and surface area determination. Results demonstrated that the studied additives segregate onto the oxide surface and modify the hydroxyl IR bands of the adsorbed hydroxyl groups. These surface modifications change some macroscopic properties of the powder such as the isoelectric point (IEP) in aqueous suspensions and the final specific surface area. The increase of the surface area with additive concentration is supposedly due to the reduction of surface energy of the powders when additives segregate on the powder surface.

Electrocatalytic Oxidation of Formate with Nickel Diphosphane Dipeptide Complexes. Effect of Ligands Modified with Amino Acids

DOE Office of Scientific and Technical Information (OSTI.GOV)

Galan, Brandon R.; Reback, Matthew L.; Jain, Avijita

2013-09-03

A series of nickel bis-diphosphine complexes with dipeptides appended to the ligands were investigated for the catalytic oxidation of formate. Typical rates of ~7 s -1 were found, similar to the parent complex (~8 s -1), with amino acid size and positioning contributing very little to rate or operating potential. Hydroxyl functionalities did result in lower rates, which were recovered by protecting the hydroxyl group. The results suggest that the overall dielectric introduced by the dipeptides does not play an important role in catalysis, but free hydroxyl groups do influence activity suggesting contributions from intra- or intermolecular interactions. These observationsmore » are important in developing a fundamental understanding of the affect that an enzyme-like outer coordination sphere can have upon molecular catalysts. This work was funded by the US DOE Basic Energy Sciences, Chemical Sciences, Geoscience and Biosciences Division (BRG, AJ, AMA, WJS), the US DOE Basic Energy Sciences, Physical Bioscience program (MLR). Pacific Northwest National Laboratory is operated by Battelle for the U.S. Department of Energy.« less

Formation of hydroxyl-functionalized stilbenoid molecular sieves at the liquid/solid interface on top of a 1-decanol monolayer.

PubMed

Bellec, Amandine; Arrigoni, Claire; Douillard, Ludovic; Fiorini-Debuisschert, Céline; Mathevet, Fabrice; Kreher, David; Attias, André-Jean; Charra, Fabrice

2014-10-31

Specific molecular tectons can be designed to form molecular sieves through self-assembly at the solid-liquid interface. After demonstrating a model tecton bearing apolar alkyl chains, we then focus on a modified structure involving asymmetric functionalization of some alkyl chains with polar hydroxyl groups in order to get chemical selectivity in the sieving. As the formation of supramolecular self-assembled networks strongly depends on molecule-molecule, molecule-substrate and molecule-solvent interactions, we compared the tectons' self-assembly on graphite for two types of solvent. We demonstrate the possibility to create hydroxylated stilbenoid molecular sieves by using 1-decanol as a solvent. Interestingly, with this solvent, the porous network is developed on top of a 1-decanol monolayer.

Monosaccharides as Scaffolds for the Synthesis of Novel Compounds

NASA Astrophysics Data System (ADS)

Murphy, Paul V.; Velasco-Torrijos, Trinidad

This chapter focuses on monosaccharides and scaffolds their derivatives as scaffolds for the synthesis of primarily bioactive compounds. Such carbohydrate derivatives have been designed to modulate mainly protein-protein and peptide-protein interactions although modulators of carbohydrate-protein and carbohydrate-nucleic acid interactions have also been of interest. The multiple hydroxyl groups that are present on saccharides have made pyranose, furanose and iminosugars ideal templates or scaffolds to which recognition or pharmacophoric groups can be grafted to generate novel compounds for medicinal chemistry. The synthesis of compounds for evaluations require strategies for regioselective reactions of saccharide hydroxyl groups and use of orthogonally stable protecting groups. Syntheses have been carried out on the solid phase and in solution. Also the use of uronic acids, amino sugars and sugar amino acids has facilitated the synthesis of peptidomimetics and prospecting libraries as they enable, through presence of amino or carboxylic acid groups, chemoselective approaches to be employed in solution and on solid phase. Sugar amino acids are readily incorporated, as peptide isosteres, to generate sugar-peptide hybrids or for the synthesis of novel carbopeptoids . The synthesis of new cyclic compounds, derived in part from saccharides, and their application as scaffolds is an emerging area and recent examples include spirocyclic compounds, benzodiazepine-saccharide hybrids and macrolide-saccharide hybrids. Potent bioactive saccharide derivatives have been identified that include enzyme inhibitors , somatostatin receptor ligands, integrin ligands, anti-viral compounds, shiga toxin inhibitors and cell growth inhibitors. Some saccharide derivatives have demonstrated improved cellular permeability when compared with peptides and are in clinical trials.

Diastereoselective Additions of Allylmetal Reagents to Free and Protected syn-α,β-Dihydroxyketones Enable Efficient Synthetic Routes to Methyl Trioxacarcinoside A

PubMed Central

Smaltz, Daniel J.; Švenda, Jakub

2012-01-01

Two routes to the 2,6-dideoxysugar methyl trioxacarcinoside A are described. Each was enabled by an apparent α-chelation-controlled addition of an allylmetal reagent to a ketone substrate containing a free α-hydroxyl group and a β-hydroxyl substituent, either free or protected as the corresponding di-tert-butylmethyl silyl ether. Both routes provide practical access to gram-quantities of trioxacarcinose A in a form suitable for glycosidic coupling reactions. PMID:22404560

Radiocarbon tracer measurements of atmospheric hydroxyl radical concentrations

NASA Technical Reports Server (NTRS)

Campbell, M. J.; Farmer, J. C.; Fitzner, C. A.; Henry, M. N.; Sheppard, J. C.

1986-01-01

The usefulness of the C-14 tracer in measurements of atmospheric hydroxyl radical concentration is discussed. The apparatus and the experimental conditions of three variations of a radiochemical method of atmosphere analysis are described and analyzed: the Teflon bag static reactor, the flow reactor (used in the Wallops Island tests), and the aircraft OH titration reactor. The procedure for reduction of the aircraft reactor instrument data is outlined. The problems connected with the measurement of hydroxyl radicals are discussed. It is suggested that the gas-phase radioisotope methods have considerable potential in measuring tropospheric impurities present in very low concentrations.

Functional Analysis of Cytochrome P450s Involved in Streptovaricin Biosynthesis and Generation of Anti-MRSA Analogues.

PubMed

Liu, Yuanzhen; Chen, Xu; Li, Zhengyuan; Xu, Wei; Tao, Weixin; Wu, Jie; Yang, Jian; Deng, Zixin; Sun, Yuhui

2017-10-20

The streptovaricins, chemically related to the rifamycins, are highly effective antibacterial agents, particularly against mycobacteria. Herein, a bioassay-guided investigation of Streptomyces spectabilis CCTCC M2017417 has led to the characterization of streptovaricins as potent compounds against methicillin-resistant Staphylococcus aureus (MRSA). We identified the streptovaricin biosynthetic gene cluster from S. spectabilis CCTCC M2017417 based on genomic sequencing and bioinformatic analysis. Targeted in-frame deletion of five cytochrome P450 genes (stvP1-P5) resulted in the identification of four new streptovaricin analogues and revealed the functions of these genes as follows: stvP1, stvP4, and stvP5 are responsible for the hydroxylation of C-20, Me-24, and C-28, respectively. stvP2 is possibly involved in formation of the methylenedioxy bridge, and stvP3, a conserved gene found in the biosynthetic cluster for naphthalenic ansamycins, might be related to the formation of a naphthalene ring. Biochemical verification of the hydroxylase activity of StvP1, StvP4, and StvP5 was performed, and StvP1 showed unexpected biocatalytic specificity and promiscuity. More importantly, anti-MRSA studies of streptovaricins and derivatives revealed significant structure-activity relationships (SARs): The hydroxyl group at C-28 plays a vital role in antibacterial activity. The hydroxyl group at C-20 substantially enhances activity in the absence of the methoxycarbonyl side chain at C-24, which can increase the activity regardless of the presence of a hydroxyl group at C-20. The inner lactone ring between C-21 and C-24 shows a positive effect on activity. This work provides meaningful information on the SARs of streptovaricins and demonstrates the utility of the engineering of streptovaricins to yield novel anti-MRSA molecules.

Crystal structure of a complex of HIV-1 protease with a dihydroxyethylene-containing inhibitor: comparisons with molecular modeling.

PubMed Central

Thanki, N.; Rao, J. K.; Foundling, S. I.; Howe, W. J.; Moon, J. B.; Hui, J. O.; Tomasselli, A. G.; Heinrikson, R. L.; Thaisrivongs, S.; Wlodawer, A.

1992-01-01

The structure of a crystal complex of recombinant human immunodeficiency virus type 1 (HIV-1) protease with a peptide-mimetic inhibitor containing a dihydroxyethylene isostere insert replacing the scissile bond has been determined. The inhibitor is Noa-His-Hch psi [CH(OH)CH(OH)]Vam-Ile-Amp (U-75875), and its Ki for inhibition of the HIV-1 protease is < 1.0 nM (Noa = 1-naphthoxyacetyl, Hch = a hydroxy-modified form of cyclohexylalanine, Vam = a hydroxy-modified form of valine, Amp = 2-pyridylmethylamine). The structure of the complex has been refined to a crystallographic R factor of 0.169 at 2.0 A resolution by using restrained least-squares procedures. Root mean square deviations from ideality are 0.02 A and 2.4 degrees, for bond lengths and angles, respectively. The bound inhibitor diastereomer has the R configurations at both of the hydroxyl chiral carbon atoms. One of the diol hydroxyl groups is positioned such that it forms hydrogen bonds with both the active site aspartates, whereas the other interacts with only one of them. Comparison of this X-ray structure with a model-built structure of the inhibitor, published earlier, reveals similar positioning of the backbone atoms and of the side-chain atoms in the P2-P2' region, where the interaction with the protein is strongest. However, the X-ray structure and the model differ considerably in the location of the P3 and P3' end groups, and also in the positioning of the second of the two central hydroxyl groups. Reconstruction of the central portion of the model revealed the source of the hydroxyl discrepancy, which, when corrected, provided a P1-P1' geometry very close to that seen in the X-ray structure. PMID:1304383

Antioxidant Properties of Kynurenines: Density Functional Theory Calculations

PubMed Central

2016-01-01

Kynurenines, the main products of tryptophan catabolism, possess both prooxidant and anioxidant effects. Having multiple neuroactive properties, kynurenines are implicated in the development of neurological and cognitive disorders, such as Alzheimer's, Parkinson's, and Huntington's diseases. Autoxidation of 3-hydroxykynurenine (3HOK) and its derivatives, 3-hydroxyanthranilic acid (3HAA) and xanthommatin (XAN), leads to the hyperproduction of reactive oxygen species (ROS) which damage cell structures. At the same time, 3HOK and 3HAA have been shown to be powerful ROS scavengers. Their ability to quench free radicals is believed to result from the presence of the aromatic hydroxyl group which is able to easily abstract an electron and H-atom. In this study, the redox properties for kynurenines and several natural and synthetic antioxidants have been calculated at different levels of density functional theory in the gas phase and water solution. Hydroxyl bond dissociation enthalpy (BDE) and ionization potential (IP) for 3HOK and 3HAA appear to be lower than for xanthurenic acid (XAA), several phenolic antioxidants, and ascorbic acid. BDE and IP for the compounds with aromatic hydroxyl group are lower than for their precursors without hydroxyl group. The reaction rate for H donation to *O-atom of phenoxyl radical (Ph-O*) and methyl peroxy radical (Met-OO*) decreases in the following rankings: 3HOK ~ 3HAA > XAAOXO > XAAENOL. The enthalpy absolute value for Met-OO* addition to the aromatic ring of the antioxidant radical increases in the following rankings: 3HAA* < 3HOK* < XAAOXO* < XAAENOL*. Thus, the high free radical scavenging activity of 3HAA and 3HOK can be explained by the easiness of H-atom abstraction and transfer to O-atom of the free radical, rather than by Met-OO* addition to the kynurenine radical. PMID:27861556

Mechanistic Insights of Ethanol Steam Reforming over Ni–CeO x (111): The Importance of Hydroxyl Groups for Suppressing Coke Formation

DOE PAGES

Liu, Zongyuan; Duchoň, Tomáš; Wang, Huanru; ...

2015-07-30

We have studied the reaction of ethanol and water over Ni–CeO 2-x(111) model surfaces to elucidate the mechanistic steps associated with the ethanol steam reforming (ESR) reaction. Our results provide insights about the importance of hydroxyl groups to the ESR reaction over Ni-based catalysts. Systematically, we have investigated the reaction of ethanol on Ni–CeO 2-x(111) at varying Ce³⁺ concentrations (CeO 1.8–2.0) with absence/presence of water using a combination of soft X-ray photoelectron spectroscopy (sXPS) and temperature-programmed desorption (TPD). Consistent with previous reports, upon annealing, metallic Ni formed on reduced ceria while NiO was the main component on fully oxidized ceria.more » Ni⁰ is the active phase leading to both the C–C and C–H cleavage of ethanol but is also responsible for carbon accumulation or coking. We have identified a Ni₃C phase that formed prior to the formation of coke. At temperatures above 600K, the lattice oxygen from ceria and the hydroxyl groups from water interact cooperatively in the removal of coke, likely through a strong metal–support interaction between nickel and ceria that facilitates oxygen transfer.« less

Molecular Insights into the Local Anesthetic Receptor within Voltage-Gated Sodium Channels Using Hydroxylated Analogs of Mexiletine

PubMed Central

Desaphy, Jean-François; Dipalma, Antonella; Costanza, Teresa; Carbonara, Roberta; Dinardo, Maria Maddalena; Catalano, Alessia; Carocci, Alessia; Lentini, Giovanni; Franchini, Carlo; Camerino, Diana Conte

2011-01-01

We previously showed that the β-adrenoceptor modulators, clenbuterol and propranolol, directly blocked voltage-gated sodium channels, whereas salbutamol and nadolol did not (Desaphy et al., 2003), suggesting the presence of two hydroxyl groups on the aromatic moiety of the drugs as a molecular requisite for impeding sodium channel block. To verify such an hypothesis, we synthesized five new mexiletine analogs by adding one or two hydroxyl groups to the aryloxy moiety of the sodium channel blocker and tested these compounds on hNav1.4 channels expressed in HEK293 cells. Concentration–response relationships were constructed using 25-ms-long depolarizing pulses at −30 mV applied from an holding potential of −120 mV at 0.1 Hz (tonic block) and 10 Hz (use-dependent block) stimulation frequencies. The half-maximum inhibitory concentrations (IC50) were linearly correlated to drug lipophilicity: the less lipophilic the drug, minor was the block. The same compounds were also tested on F1586C and Y1593C hNav1.4 channel mutants, to gain further information on the molecular interactions of mexiletine with its receptor within the sodium channel pore. In particular, replacement of Phe1586 and Tyr1593 by non-aromatic cysteine residues may help in the understanding of the role of π–π or π–cation interactions in mexiletine binding. Alteration of tonic block suggests that the aryloxy moiety of mexiletine may interact either directly or indirectly with Phe1586 in the closed sodium channel to produce low-affinity binding block, and that this interaction depends on the electrostatic potential of the drug aromatic tail. Alteration of use-dependent block suggests that addition of hydroxyl groups to the aryloxy moiety may modify high-affinity binding of the drug amine terminal to Phe1586 through cooperativity between the two pharmacophores, this effect being mainly related to drug lipophilicity. Mutation of Tyr1593 further impaired such cooperativity. In conclusion, these results confirm our former hypothesis by showing that the presence of hydroxyl groups to the aryloxy moiety of mexiletine greatly reduced sodium channel block, and provide molecular insights into the intimate interaction of local anesthetics with their receptor. PMID:22403541

Identification of compounds inhibiting the C-S lyase activity of a cell extract from a Staphylococcus sp. isolated from human skin.

PubMed

Egert, M; Höhne, H-M; Weber, T; Simmering, R; Banowski, B; Breves, R

2013-12-01

The C-S lyase activity of bacteria in the human armpit releases highly malodorous, volatile sulfur compounds from nonvolatile precursor molecules. Such compounds significantly contribute to human body odour. Hence, C-S lyase represents an attractive target for anti-body-odour cosmetic products. Here, aiming at a final use in an ethanol-based deodorant formulation, 267 compounds and compound mixtures were screened for their ability to inhibit the C-S lyase activity of a Stapyhlococcus sp. crude extract. Staphylococcus sp. Isolate 128, closely related to Staphylococcus hominis, was chosen as the test bacterium, as it showed a reproducibly high specific C-S lyase activity on three different culturing media. Using a photometric assay and benzylcysteine as substrate, six rather complex, plant-derived compound mixtures and five well defined chemical compounds or compound mixtures were identified as inhibitors, leading to an inhibition of ≥70% at concentrations of ≤0·5% in the assay. The inhibition data have demonstrated that compounds with two vicinal hydroxyl groups or one hydroxyl and one keto group bound to an aryl residue are characteristic for the inhibition. The substances identified as C-S lyase inhibitors have the potential to improve the performance of anti-body-odour cosmetic products, for example, ethanol-based deodorants. Bacterial C-S lyase represents one of the key enzymes involved in human body odour formation. The aim of this study was to identify compounds inhibiting the C-S lyase activity of a Staphylococcus sp. isolate from the human skin. The compounds identified as the best inhibitors are characterized by the following features: two vicinal hydroxyl groups or one hydroxyl and one keto group bound to an aryl residue. They might be used to improve the performance of cosmetic products aiming to prevent the formation of microbially caused human body odour, for example, ethanol-based deodorants. © 2013 The Society for Applied Microbiology.

In vivo transport of three radioactive [18F]-fluorinated deoxysucrose analogs by the maize sucrose transporter ZmSUT1.

PubMed

Tran, Thu M; Hampton, Carissa S; Brossard, Tom W; Harmata, Michael; Robertson, J David; Jurisson, Silvia S; Braun, David M

2017-06-01

Sucrose transporter (SUT) proteins translocate sucrose across cell membranes; however, mechanistic aspects of sucrose binding by SUTs are not well resolved. Specific hydroxyl groups in sucrose participate in hydrogen bonding with SUT proteins. We previously reported that substituting a radioactive fluorine-18 [ 18 F] at the C-6' position within the fructosyl moiety of sucrose did not affect sucrose transport by the maize (Zea mays) ZmSUT1 protein. To determine how 18 F substitution of hydroxyl groups at two other positions within sucrose, the C-1' in the fructosyl moiety or the C-6 in the glucosyl moiety, impact sucrose transport, we synthesized 1'-[F 18 ]fluoro-1'-deoxysucrose and 6-[F 18 ]fluoro-6-deoxysucrose ([ 18 F]FDS) analogs. Each [ 18 F]FDS derivative was independently introduced into wild-type or sut1 mutant plants, which are defective in sucrose phloem loading. All three (1'-, 6'-, and 6-) [ 18 F]FDS derivatives were efficiently and equally translocated, similarly to carbon-14 [ 14 C]-labeled sucrose. Hence, individually replacing the hydroxyl groups at these positions within sucrose does not interfere with substrate recognition, binding, or membrane transport processes, and hydroxyl groups at these three positions are not essential for hydrogen bonding between sucrose and ZmSUT1. [ 18 F]FDS imaging afforded several advantages compared to [ 14 C]-sucrose detection. We calculated that 1'-[ 18 F]FDS was transported at approximately a rate of 0.90 ± 0.15 m.h-1 in wild-type leaves, and at 0.68 ± 0.25 m.h-1 in sut1 mutant leaves. Collectively, our data indicated that [ 18 F]FDS analogs are valuable tools to probe sucrose-SUT interactions and to monitor sucrose transport in plants. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

Biosynthesis of Costunolide, Dihydrocostunolide, and Leucodin. Demonstration of Cytochrome P450-Catalyzed Formation of the Lactone Ring Present in Sesquiterpene Lactones of Chicory

PubMed Central

de Kraker, Jan-Willem; Franssen, Maurice C.R.; Joerink, Maaike; de Groot, Aede; Bouwmeester, Harro J.

2002-01-01

Chicory (Cichorium intybus) is known to contain guaianolides, eudesmanolides, and germacranolides. These sesquiterpene lactones are postulated to originate from a common germacranolide, namely (+)-costunolide. Whereas a pathway for the formation of germacra-1(10),4,11(13)-trien-12-oic acid from farnesyl diphosphate had previously been established, we now report the isolation of an enzyme activity from chicory roots that converts the germacrene acid into (+)-costunolide. This (+)-costunolide synthase catalyzes the last step in the formation of the lactone ring present in sesquiterpene lactones and is dependent on NADPH and molecular oxygen. Incubation of the germacrene acid in the presence of 18O2 resulted in the incorporation of one atom of 18O into (+)-costunolide. The label was situated at the ring oxygen atom. Hence, formation of the lactone ring most likely occurs via C6-hydroxylation of the germacrene acid and subsequent attack of this hydroxyl group at the C12-atom of the carboxyl group. Blue light-reversible CO inhibition and experiments with cytochrome P450 inhibitors demonstrated that the (+)-costunolide synthase is a cytochrome P450 enzyme. In addition, enzymatic conversion of (+)-costunolide into 11(S),13-dihydrocostunolide and leucodin, a guaianolide, was detected. The first-mentioned reaction involves an enoate reductase, whereas the formation of leucodin from (+)-costunolide probably involves more than one enzyme, including a cytochrome P450 enzyme. PMID:12011356

Surface monofunctionalized polymethyl pentene hollow fiber membranes by plasma treatment and hemocompatibility modification for membrane oxygenators

NASA Astrophysics Data System (ADS)

Huang, Xin; Wang, Weiping; Zheng, Zhi; Fan, Wenling; Mao, Chun; Shi, Jialiang; Li, Lei

2016-01-01

The hemocompatibility of polymethyl pentene (PMP) hollow fiber membranes (HFMs) was improved through surface modification for membrane oxygenator applications. The modification was performed stepwise with the following: (1) oxygen plasma treatment, (2) functionalization of monosort hydroxyl groups through NaBH4 reduction, and (3) grafting 2-methacryloyloxyethyl phosphorylcholine (MPC) or heparin. SEM, ATR-FTIR, and XPS analyses were conducted to confirm successful grafting during the modification. The hemocompatibility of PMP HFMs was analyzed and compared through protein adsorption, platelet adhesion, and coagulation tests. Pure CO2 and O2 permeation rates, as well as in vitro gas exchange rates, were determined to evaluate the mass transfer properties of PMP HFMs. SEM results showed that different nanofibril topographies were introduced on the HFM surface. ATR-FTIR and XPS spectra indicated the presence of functionalization of monosort hydroxyl group and the grafting of MPC and heparin. Hemocompatibility evaluation results showed that the modified PMP HFMs presented optimal hemocompatibility compared with pristine HFMs. Gas permeation results revealed that gas permeation flux increased in the modified HFMs because of dense surface etching during the plasma treatment. The results of in vitro gas exchange rates showed that all modified PMP HFMs presented decreased gas exchange rates because of potential surface fluid wetting. The proposed strategy exhibits a potential for fabricating membrane oxygenators for biomedical applications to prevent coagulation formation and alter plasma-induced surface topology and composition.

Biosynthesis of costunolide, dihydrocostunolide, and leucodin. Demonstration of cytochrome p450-catalyzed formation of the lactone ring present in sesquiterpene lactones of chicory.

PubMed

de Kraker, Jan-Willem; Franssen, Maurice C R; Joerink, Maaike; de Groot, Aede; Bouwmeester, Harro J

2002-05-01

Chicory (Cichorium intybus) is known to contain guaianolides, eudesmanolides, and germacranolides. These sesquiterpene lactones are postulated to originate from a common germacranolide, namely (+)-costunolide. Whereas a pathway for the formation of germacra-1(10),4,11(13)-trien-12-oic acid from farnesyl diphosphate had previously been established, we now report the isolation of an enzyme activity from chicory roots that converts the germacrene acid into (+)-costunolide. This (+)-costunolide synthase catalyzes the last step in the formation of the lactone ring present in sesquiterpene lactones and is dependent on NADPH and molecular oxygen. Incubation of the germacrene acid in the presence of 18O2 resulted in the incorporation of one atom of 18O into (+)-costunolide. The label was situated at the ring oxygen atom. Hence, formation of the lactone ring most likely occurs via C6-hydroxylation of the germacrene acid and subsequent attack of this hydroxyl group at the C12-atom of the carboxyl group. Blue light-reversible CO inhibition and experiments with cytochrome P450 inhibitors demonstrated that the (+)-costunolide synthase is a cytochrome P450 enzyme. In addition, enzymatic conversion of (+)-costunolide into 11(S),13-dihydrocostunolide and leucodin, a guaianolide, was detected. The first-mentioned reaction involves an enoate reductase, whereas the formation of leucodin from (+)-costunolide probably involves more than one enzyme, including a cytochrome P450 enzyme.

Synthesis and Characterization of Hydroxyapatite/Fullerenol Nanocomposites.

PubMed

Djordjevic, Aleksandar; Ignjatovic, Nenad; Seke, Mariana; Jovic, Danica; Uskokovic, Dragan; Rakocevic, Zlatko

2015-02-01

Fullerenols are polyhydroxylated, water soluble derivatives of fullerene C60, with potential application in medicine as diagnostic agents, antioxidants or nano drug carriers. This paper describes synthesis and physical characterization of a new nanocomposite hydroxyapatite/fullerenol. Surface of the nanocomposite hydroxyapatite/fullerenol is inhomogeneous with the diameter of the particles in the range from 100 nm to 350 nm. The ζ potential of this nanocomposite is ten times lower when compared to hydroxyapatite. Surface phosphate groups of hydroxyapatite are prone to forming hydrogen bonds, when in close contact with hydroxyl groups, which could lead to formation of hydrogen bonds between hydroxyapatite and hydroxyl groups of fullerenol. The surface of hydroxyapatite particles (-2.5 mV) was modified by fullerenol particles, as confirmed by the obtained ζ potential value of the nanocomposite biomaterial hydroxyapatite/fullerenol (-25.0 mV). Keywords: Hydroxyapatite, Fullerenol, Nanocomposite, Surface Analysis.

Tyrosine-like condensed derivatives as tyrosinase inhibitors.

PubMed

Matos, Maria João; Santana, Lourdes; Uriarte, Eugenio; Serra, Silvia; Corda, Marcella; Fadda, Maria Benedetta; Era, Benedetta; Fais, Antonella

2012-05-01

We report the pharmacological evaluation of a new series of 3-aminocoumarins differently substituted with hydroxyl groups, which have been synthesized because they include in their structures the tyrosine fragment (tyrosine-like compounds), with the aim of discovering structural features necessary for tyrosinase inhibitory activity. The synthesized compounds 4 and 7-9 were evaluated in vitro as mushroom tyrosinase inhibitors. Two of the described compounds showed lower IC50 (concentration giving 50% inhibition of tyrosinase activity) than umbelliferone, used as a reference compound. Compound 7 (IC50=53µm) was the best tyrosinase inhibitor of this small series, having an IC50 value 10-fold lower than umbelliferone. Compound 7 (3-amino-7-hydroxycoumarin) had amino and hydroxyl groups precisely mimicking the same positions that both groups occupy on the tyrosine molecule. © 2012 The Authors. JPP © 2012 Royal Pharmaceutical Society.

Steroids excreted in urine by neonates with 21-hydroxylase deficiency. 2. Characterization, using GC-MS and GC-MS/MS, of pregnanes and pregnenes with an oxo- group on the A- or B-ring.

PubMed

Christakoudi, Sofia; Cowan, David A; Taylor, Norman F

2012-04-01

Urine from neonates with 21-hydroxylase deficiency contains a large range of metabolites of 17-hydroxyprogesterone, 21-deoxycortisol and androgens but few have been previously described. We present the second part of a comprehensive project to characterize and identify these in order to enhance diagnosis and to further elucidate neonatal steroid metabolism. Steroids were analyzed, after extraction and enzymatic conjugate hydrolysis, as methyloxime-trimethylsilyl ether derivatives on gas-chromatographs coupled to quadrupole and ion-trap mass-spectrometers. GC-MS and GC-MS/MS spectra were used together to determine the structure of the A- and B-rings containing an oxo group. Fragmentations indicating presence of 3-, 6-, and 7-oxo groups and also 1β-, 2α-, 4β-, and 6β-hydroxyls are presented and discussed for the first time. Interpretation was aided by comparison with spectra of available relevant standards, of oxidation products of standards and urinary metabolites and of deuterated derivatives. Endogenous 1-enes and 2(3)-ene artifacts of non-hydrolyzed 3α-sulfates are also reported. D-ring and side chain structure was determined according to our previously published criteria. Likely metabolic relationships were also explored. We conclude that GC-MS combined with GC-MS/MS allows identification of the A- and B-ring structure of pregnane and pregnenes in the presence of an oxo group on one of these rings. Major oxygenations are 1β, 15β, 16α and 21-hydroxy and 6- and 7-oxo groups. Minor positions of hydroxylation are those at 2α, 4β and 6β. Three major metabolic streams exist in affected neonates in addition to the classical 3α-hydroxy-5β-pregnane pathway, i.e. these of the 3-oxo-4-enes as well as 3α- and 3β-hydroxy-5α-anes. Copyright © 2011 Elsevier Inc. All rights reserved.

Regioselective Synthesis of Cellulose Ester Homopolymers

Treesearch

Daiqiang Xu; Kristen Voiges; Thomas Elder; Petra Mischnick; Kevin J. Edgar

2012-01-01

Regioselective synthesis of cellulose esters is extremely difficult due to the small reactivity differences between cellulose hydroxyl groups, small differences in steric demand between acyl moieties of interest, and the difficulty of attaching and detaching many protecting groups in the presence of cellulose ester moieties without removing the ester groups. Yet the...

Microbial transformations of diosgenin by the white-rot basidiomycete Coriolus versicolor.

PubMed

Wu, Guang-Wei; Gao, Jin-Ming; Shi, Xin-Wei; Zhang, Qiang; Wei, Shao-Peng; Ding, Kan

2011-10-28

Microbial transformation of diosgenin (3β-hydroxy-5-spirostene) using white-rot fungus Coriolus versicolor afforded four previously unreported polyhydroxylated steroids, 25(R)-spirost-5-en-3β,7α,15α,21-tetraol (5), 25(R)-spirost-5-en-3β,7β,12β,21-tetrol (6), (25R)-spirost-5-en-3β,7α,12β,21-tetraol (7), and (25R)-spirost-5-en-3β,7β,11α,21-tetraol (8), along with three known congeners, 25(R)-spirost-5-en-3β,7β-diol (2), 25(R)-spirost-5-en-3β,7β,21-triol (3), and 25(R)-spirost-5-en-3β,7β,12β-triol (4). These structures were elucidated by 1D and 2D NMR as well as HR-ESIMS analysis. In addition, we provide evidence for two new microbial hydroxylations of diosgenin: C-21 primary carbon hydroxylation and C-15 hydroxylation. The 3β-hydroxyl group and double bond in the B-ring of diosgenin were found to be important structural determinants for their activity.

Method of making a membrane having hydrophilic and hydrophobic surfaces for adhering cells or antibodies by using atomic oxygen or hydroxyl radicals

NASA Technical Reports Server (NTRS)

Koontz, Steven L. (Inventor); Spaulding, Glenn F. (Inventor)

1994-01-01

A portion of an organic polymer article such as a membrane is made hydrophilic by exposing a hydrophobic surface of the article to a depth of about 50 to about 5000 angstroms to atomic oxygen or hydroxyl radicals at a temperature below 100C., preferably below 40 C, to form a hydrophilic uniform surface layer of hydrophilic hydroxyl groups. The atomic oxygen and hydroxyl radicals are generated by a flowing afterglow microwave discharge, and the surface is outside of a plasma produced by the discharge. A membrane having both hydrophilic and hydrophobic surfaces can be used in an immunoassay by adhering antibodies to the hydrophobic surface. In another embodiment, the membrane is used in cell culturing where cells adhere to the hydrophilic surface. Prior to adhering cells, the hydrophilic surface may be grafted with a compatibilizing compound. A plurality of hydrophilic regions bounded by adjacent hydrophobic regions can be produced such that a maximum of one cell per each hydrophilic region adheres.

Oxygen activation at the plasma membrane: relation between superoxide and hydroxyl radical production by isolated membranes.

PubMed

Heyno, Eiri; Mary, Véronique; Schopfer, Peter; Krieger-Liszkay, Anja

2011-07-01

Production of reactive oxygen species (hydroxyl radicals, superoxide radicals and hydrogen peroxide) was studied using EPR spin-trapping techniques and specific dyes in isolated plasma membranes from the growing and the non-growing zones of hypocotyls and roots of etiolated soybean seedlings as well as coleoptiles and roots of etiolated maize seedlings. NAD(P)H mediated the production of superoxide in all plasma membrane samples. Hydroxyl radicals were only produced by the membranes of the hypocotyl growing zone when a Fenton catalyst (FeEDTA) was present. By contrast, in membranes from other parts of the seedlings a low rate of spontaneous hydroxyl radical formation was observed due to the presence of small amounts of tightly bound peroxidase. It is concluded that apoplastic hydroxyl radical generation depends fully, or for the most part, on peroxidase localized in the cell wall. In soybean plasma membranes from the growing zone of the hypocotyl pharmacological tests showed that the superoxide production could potentially be attributed to the action of at least two enzymes, an NADPH oxidase and, in the presence of menadione, a quinone reductase.

Effect of Myricetin, Pyrogallol, and Phloroglucinol on Yeast Resistance to Oxidative Stress

PubMed Central

Mendes, Vanda; Vilaça, Rita; de Freitas, Victor; Ferreira, Pedro Moradas; Mateus, Nuno; Costa, Vítor

2015-01-01

The health beneficial effects of dietary polyphenols have been attributed to their intrinsic antioxidant activity, which depends on the structure of the compound and number of hydroxyl groups. In this study, the protective effects of pyrogallol, phloroglucinol, and myricetin on the yeast Saccharomyces cerevisiae were investigated. Pyrogallol and myricetin, which have a pyrogallol structure in the B ring, increased H2O2 resistance associated with a reduction in intracellular oxidation and protein carbonylation, whereas phloroglucinol did not exert protective effects. The acquisition of oxidative stress resistance in cells pretreated with pyrogallol and myricetin was not associated with an induction of endogenous antioxidant defences as assessed by the analysis of superoxide dismutase and catalase activities. However, myricetin, which provided greater stress resistance, prevented H2O2-induced glutathione oxidation. Moreover, myricetin increased the chronological lifespan of yeast lacking the mitochondrial superoxide dismutase (Sod2p), which exhibited a premature aging phenotype and oxidative stress sensitivity. These findings show that the presence of hydroxyl groups in the ortho position of the B ring in pyrogallol and myricetin contributes to the antioxidant protection afforded by these compounds. In addition, myricetin may alleviate aging-induced oxidative stress, particularly when redox homeostasis is compromised due to downregulation of endogenous defences present in mitochondria. PMID:26000072

Bile alcohols function as the ligands of membrane-type bile acid-activated G protein-coupled receptor

PubMed Central

Iguchi, Yusuke; Yamaguchi, Masafumi; Sato, Hiroyuki; Kihira, Kenji; Nishimaki-Mogami, Tomoko; Une, Mizuho

2010-01-01

TGR5 is a G protein-coupled receptor that is activated by bile acids, resulting in an increase in cAMP levels and the subsequent modulation of energy expenditure in brown adipose tissue and muscle. Therefore, the development of a TGR5-specific agonist could lead to the prevention and treatment of various metabolic disorders related to obesity. In the present study, we evaluated the ability of bile alcohols, which are structurally and physiologically similar to bile acids and are produced as the end products of cholesterol catabolism in evolutionarily primitive vertebrates, to act as TGR5 agonists. In a cell-based reporter assay and a cAMP production assay performed in vitro, most bile alcohols with a side chain containing hydroxyl group(s) were highly efficacious agonists for TGR5 comparable to its most potent ligand in the naturally occurring bile acid, lithocholic acid. However, the abilities of the bile alcohols to activate TGR5 varied with the position and number of the hydroxyl substituent in the side chain. Additionally, the conformation of the steroidal nucleus of bile alcohols is also important for its activity as a TGR5 agonist. Thus, we have provided new insights into the structure-activity relationships of bile alcohols as TGR5 agonists. PMID:20023205

A new, major C27 biliary bile acid in the Red-winged tinamou (Rhynchotus rufescens):(25R)-1β,3α,7α-trihydroxy-5β-cholestan-27-oic acid*

PubMed Central

Hagey, Lee R.; Kakiyama, Genta; Muto, Akina; Iida, Takashi; Mushiake, Kumiko; Goto, Takaaki; Mano, Nariyasu; Goto, Junichi; Oliveira, Cleida A.; Hofmann, Alan F.

2009-01-01

The chemical structures of the three major bile acids present in the gallbladder bile of the Red-winged tinamou (Rhynchotus rufescens), an early evolving, ground-living bird related to ratites, were determined. Bile acids were isolated by preparative reversed-phase HPLC. Two of the compounds were identified as the taurine N-acylamidates of (25R)-3α,7α-dihydroxy-5β-cholestan-27-oic acid (constituting 22% of biliary bile acids) and (25R)-3α,7α,12α-trihydroxy-5β-cholestan-27-oic acid (constituting 51%). The remaining compound, constituting 21% of biliary bile acids, was an unknown C27 bile acid. Its structure was elucidated by LC/ESI-MS/MS and NMR and shown to be the taurine conjugate of (25R)-1β,3α,7α-trihydroxy-5β-cholestan-27-oic acid, a C27 trihydroxy bile acid not previously reported. Although C27 bile acids with a 1β-hydroxyl group have been identified as trace bile acids in the alligator, this is the first report of a major biliary C27 bile acid possessing a 1β-hydroxyl group. PMID:19011113

Electrocatalytic behavior of a nanocomposite of Ni/Pd supported by carbonized PVA nanofibers towards formic acid, ethanol and urea oxidation: A physicochemical and electro-analysis study

NASA Astrophysics Data System (ADS)

Mohamed, Ibrahim M. A.; Yasin, Ahmed S.; Barakat, Nasser A. M.; Song, Seung A.; Lee, Ha Eun; Kim, Seong Su

2018-03-01

A nanocomposite of Ni/Pd supported by carbonized poly-vinyl alcohol (PVA) nanofibers (NFs) was synthesized via electrospinning followed by calcination under an argon atmosphere. The as-synthesized NFs were studied using physicochemical analyses, such as field-emission scanning electron microscopy (FESEM), Transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTsbnd IR) and X-ray photoelectron spectroscopy (XPS), to investigate the morphology, crystallinity, effect of carbonization and surface chemistry of the NFs, respectively. Cyclic voltammetry (CV) and chronoamperometry (CA) were utilized to study the performance of the NFs towards electrooxidation reactions. The designed NFs present superior electrocatalytic behavior in an acid medium towards formic acid oxidation, as well as urea and ethanol oxidation in an alkaline medium. The electrocatalytic performance of the bimetallic NFs appears to arise from the assembly of bimetallic Ni/Pd@NFs based on PVA, which has hydroxyl groups. These hydroxyl groups can decrease the negative processes that occur as a result of metal-metal interactions, such as the aggregation process. This study introduces a novel non-precious electrocatalyst to facilitate the commercialization of fuel cells based on formic acid, urea and ethanol.

Enzymatic routes for the synthesis of ursodeoxycholic acid.

PubMed

Eggert, Thorsten; Bakonyi, Daniel; Hummel, Werner

2014-12-10

Ursodeoxycholic acid, a secondary bile acid, is used as a drug for the treatment of various liver diseases, the optimal dose comprises the range of 8-10mg/kg/day. For industrial syntheses, the structural complexity of this bile acid requires the use of an appropriate starting material as well as the application of regio- and enantio-selective enzymes for its derivatization. Most strategies for the synthesis start from cholic acid or chenodeoxycholic acid. The latter requires the conversion of the hydroxyl group at C-7 from α- into β-position in order to obtain ursodeoxycholic acid. Cholic acid on the other hand does not only require the same epimerization reaction at C-7 but the removal of the hydroxyl group at C-12 as well. There are several bacterial regio- and enantio-selective hydroxysteroid dehydrogenases (HSDHs) to carry out the desired reactions, for example 7α-HSDHs from strains of Clostridium, Bacteroides or Xanthomonas, 7β-HSDHs from Clostridium, Collinsella, or Ruminococcus, or 12α-HSDH from Clostridium or from Eggerthella. However, all these bioconversion reactions need additional steps for the regeneration of the coenzymes. Selected multi-step reaction systems for the synthesis of ursodeoxycholic acid are presented in this review. Copyright © 2014 Elsevier B.V. All rights reserved.

Adsorption of natural dissolved organic matter at the oxide/water interface

USGS Publications Warehouse

Davis, James A.

1982-01-01

Natural organic matter is readily adsorbed by alumina and kaolinite in the pH range of natural waters. Adsorption occurs by complex formation between surface hydroxyls and the acidic functional groups of the organic matter. Oxides with relatively acidic surface hydroxyls, e.g. silica, do not react strongly with the organic matter. Under conditions typical for natural waters, almost complete surface coverage by adsorbed organic matter may be expected for alumina, hydrous iron oxides and the edge sites of aluminosilicates. Potentiometric titration and electrophoresis indicate that most of the acidic functional groups of the adsorbed organic matter are neutralized by protons from solution. The organic coating is expected to have a great influence on subsequent adsorption of inorganic cations and anions.

Flexible substrate for printed wiring

NASA Technical Reports Server (NTRS)

Asakura, M.; Yabe, K.; Tanaka, H.; Soda, A.

1982-01-01

A very flexible substrate for printed wiring is disclosed which is composed of a blend of phenoxy resin-polyisocyanate-brominated epoxy resin in which the equivalent ration of the functional groups is hydroxyl grouped: isocyanate group: epoxy group = 1:0.2 to 2:0.5 to 3. The product has outstanding solder resistance and is applied to metal without using adhesives.

Structural requirements of the human sodium-dependent bile acid transporter (hASBT): Role of 3- and 7-OH moieties on binding and translocation of bile acids

PubMed Central

González, Pablo M.; Lagos, Carlos F.; Ward, Weslyn C.; Polli, James E.

2014-01-01

Bile acids (BAs) are the end products of cholesterol metabolism. One of the critical steps in their biosynthesis involves the isomerization of the 3β-hydroxyl (-OH) group on the cholestane ring to the common 3α-configuration on BAs. BAs are actively recaptured from the small intestine by the human Apical Sodium-dependent Bile Acid Transporter (hASBT) with high affinity and capacity. Previous studies have suggested that no particular hydroxyl group on BAs is critical for binding or transport by hASBT, even though 3β-hydroxylated BAs were not examined. The aim of this study was to elucidate the role of the 3α-OH group on BAs binding and translocation by hASBT. Ten 3β-hydroxylated BAs (Iso-bile acids, iBAs) were synthesized, characterized, and subjected to hASBT inhibition and uptake studies. hASBT inhibition and uptake kinetics of iBAs were compared to that of native 3α-OH BAs. Glycine conjugates of native and isomeric BAs were subjected to molecular dynamics simulations in order to identify topological descriptors related to binding and translocation by hASBT. Iso-BAs bound to hASBT with lower affinity and exhibited reduced translocation than their respective 3α-epimers. Kinetic data suggests that, in contrast to native BAs where hASBT binding is the rate-limiting step, iBAs transport was rate-limited by translocation and not binding. Remarkably, 7-dehydroxylated iBAs were not hASBT substrates, highlighting the critical role of 7-OH group on BA translocation by hASBT, especially for iBAs. Conformational analysis of gly-iBAs and native BAs identified topological features for optimal binding as: concave steroidal nucleus, 3-OH “on-” or below-steroidal plane, 7-OH below-plane, and 12-OH moiety towards-plane. Our results emphasize the relevance of the 3α-OH group on BAs for proper hASBT binding and transport and revealed the critical role of 7-OH group on BA translocation, particularly in the absence of a 3α-OH group. Results have implications for BA prodrug design. PMID:24328955

Importance of Unimolecular HO 2 Elimination in the Heterogeneous OH Reaction of Highly Oxygenated Tartaric Acid Aerosol

DOE PAGES

Cheng, Chiu Tung; Chan, Man Nin; Wilson, Kevin R.

2016-07-09

Oxygenated organic molecules are abundant in atmospheric aerosols and are transformed by oxidation reactions near the aerosol surface by gas-phase oxidants such as hydroxyl (OH) radicals. To gain better insights into how the structure of an organic molecule, particularly in the presence of hydroxyl groups, controls the heterogeneous reaction mechanisms of oxygenated organic compounds, this paper investigates the OH-radical initiated oxidation of aqueous tartaric acid (C 4H 6O 6) droplets using an aerosol flow tube reactor. The molecular composition of the aerosols before and after reaction is characterized by a soft atmospheric pressure ionization source (Direct Analysis in Real Time)more » coupled with a high-resolution mass spectrometer. The aerosol mass spectra reveal that four major reaction products are formed: a single C 4 functionalization product (C 4H 4O 6) and three C 3 fragmentation products (C 3H 4O 4, C 3H 2O 4, and C 3H 2O 5). The C 4 functionalization product does not appear to originate from peroxy radical self-reactions but instead forms via an α-hydroxylperoxy radical produced by a hydrogen atom abstraction by OH at the tertiary carbon site. The proximity of a hydroxyl group to peroxy group enhances the unimolecular HO 2 elimination from the α-hydroxylperoxy intermediate. This alcohol-to-ketone conversion yields 2-hydroxy-3-oxosuccinic acid (C 4H 4O 6), the major reaction product. While in general, C–C bond scission reactions are expected to dominate the chemistry of organic compounds with high average carbon oxidation states (OS C), our results show that molecular structure can play a larger role in the heterogeneous transformation of tartaric acid (OS C = 1.5). Finally, these results are also compared with two structurally related dicarboxylic acids (succinic acid and 2,3-dimethylsuccinic acid) to elucidate how the identity and location of functional groups (methyl and hydroxyl groups) alter heterogeneous reaction mechanisms.« less

Two-dimensional titanium carbonitrides and their hydroxylated derivatives: Structural, electronic properties and stability of MXenes Ti3C2-xNx(OH)2 from DFTB calculations

NASA Astrophysics Data System (ADS)

Enyashin, A. N.; Ivanovskii, A. L.

2013-11-01

The structural, electronic properties and stability of the new MXene compounds—two-dimensional pristine carbonitrides Ti3C2-xNx and their hydroxylated derivatives Ti3C2-xNx(OH)2 are studied by means of DFTB calculations. The genesis of the properties is discussed in the sequence: binary MXenes Ti3C2 (Ti3N2)→hydroxylated forms Ti3C2(OH)2 (Ti3N2(OH)2)→pristine MXene Ti3C2-xNx→hydroxylated Ti3C2-xNx(OH)2. All examined materials are metallic-like. The most favorable type of OH-covering is presented by the occupation of the hollow sites between three neighboring carbon (nitrogen) atoms. Two-dimensional MXene carbonitrides with random distribution of C and N atoms are found to be thermodynamically more favorable.

Identify OH groups in TiOF{sub 2} and their impact on the lithium intercalation properties

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Wei; Body, Monique; Legein, Christophe

A detailed investigation on the chemical composition of the cubic form of titanium oxyfluoride-based compound reveals the presence of OH groups substituting the oxide/ fluoride sublattice. The substitution of oxide by hydroxyl groups induces the presence of titanium vacancies (□) which were characterized by {sup 1}H and {sup 19}F solid-state NMR. {sup 1}H NMR shows that OH groups are present as bridging Ti-OH-Ti or terminal OH groups, i.e. sitting close to a titanium vacancy Ti-OH-□. The electrochemical properties vs. Li{sup +}/Li indicates that the presence of OH groups prevents the intercalation of lithium in the upper voltage region (1.2–3 Vmore » vs. Li{sup +}/Li). Indeed, a partial dehydroxylation of the framework enables to improve the reversibility of the lithium insertion/de-insertion processes. Since the presence of OH groups in this type of compounds is usual and depends on the synthesis method employed, this work enables to rationalize the different electrochemical behaviors reported in the literature and further highlights the importance of a good knowledge of the chemical composition with regard to the physico-chemical properties. - Graphical abstract: The substitution of oxide by hydroxyl groups inducing the formation of titanium vacancies (□), i.e., Ti{sub 1−x}□{sub x}O{sub 1-4x}(OH){sub 4x+y}F{sub 2−y}, was characterized by solid-state {sup 1}H and {sup 19}F NMR. - Highlights: • Evidences of the presence of OH groups and titanium vacancies in titanium oxyfluoride. • {sup 1}H NMR showed the presence of Ti-OH-Ti and Ti-OH-□ species. • The presence of OH groups limits the insertion of lithium within the interstitial sites.« less

The Hydroxyl at Position C1 of Genipin Is the Active Inhibitory Group that Affects Mitochondrial Uncoupling Protein 2 in Panc-1 Cells

PubMed Central

Hou, Jianwei; Ding, Yue; Zhang, Tong; Zhang, Yong; Wang, Jianying; Shi, Chenchen; Fu, Wenwei; Cai, Zhenzhen

2016-01-01

Genipin (GNP) effectively inhibits uncoupling protein 2 (UCP2), which regulates the leakage of protons across the inner mitochondrial membrane. UCP2 inhibition may induce pancreatic adenocarcinoma cell death by increasing reactive oxygen species (ROS) levels. In this study, the hydroxyls at positions C10 (10-OH) and C1 (1-OH) of GNP were hypothesized to be the active groups that cause these inhibitory effects. Four GNP derivatives in which the hydroxyl at position C10 or C1 was replaced with other chemical groups were synthesized and isolated. Differences in the inhibitory effects of GNP and its four derivatives on pancreatic carcinoma cell (Panc-1) proliferation were assessed. The effects of GNP and its derivatives on apoptosis, UCP2 inhibition and ROS production were also studied to explore the relationship between GNP’s activity and its structure. The derivatives with 1-OH substitutions, geniposide (1-GNP1) and 1-ethyl-genipin (1-GNP2) lacked cytotoxic effects, while the other derivatives that retained 1-OH, 10-piv-genipin (10-GNP1) and 10-acetic acid-genipin (10-GNP2) exerted biological effects similar to those of GNP, even in the absence of 10-OH. Thus, 1-OH is the key functional group in the structure of GNP that is responsible for GNP’s apoptotic effects. These cytotoxic effects involve the induction of Panc-1 cell apoptosis through UCP2 inhibition and subsequent ROS production. PMID:26771380

The Hydroxyl at Position C1 of Genipin Is the Active Inhibitory Group that Affects Mitochondrial Uncoupling Protein 2 in Panc-1 Cells.

PubMed

Yang, Yang; Yang, Yifu; Hou, Jianwei; Ding, Yue; Zhang, Tong; Zhang, Yong; Wang, Jianying; Shi, Chenchen; Fu, Wenwei; Cai, Zhenzhen

2016-01-01

Genipin (GNP) effectively inhibits uncoupling protein 2 (UCP2), which regulates the leakage of protons across the inner mitochondrial membrane. UCP2 inhibition may induce pancreatic adenocarcinoma cell death by increasing reactive oxygen species (ROS) levels. In this study, the hydroxyls at positions C10 (10-OH) and C1 (1-OH) of GNP were hypothesized to be the active groups that cause these inhibitory effects. Four GNP derivatives in which the hydroxyl at position C10 or C1 was replaced with other chemical groups were synthesized and isolated. Differences in the inhibitory effects of GNP and its four derivatives on pancreatic carcinoma cell (Panc-1) proliferation were assessed. The effects of GNP and its derivatives on apoptosis, UCP2 inhibition and ROS production were also studied to explore the relationship between GNP's activity and its structure. The derivatives with 1-OH substitutions, geniposide (1-GNP1) and 1-ethyl-genipin (1-GNP2) lacked cytotoxic effects, while the other derivatives that retained 1-OH, 10-piv-genipin (10-GNP1) and 10-acetic acid-genipin (10-GNP2) exerted biological effects similar to those of GNP, even in the absence of 10-OH. Thus, 1-OH is the key functional group in the structure of GNP that is responsible for GNP's apoptotic effects. These cytotoxic effects involve the induction of Panc-1 cell apoptosis through UCP2 inhibition and subsequent ROS production.

Nanostructure and surface activation of mayenite (12CaO·7Al2O3) ceramics via femtosecond laser irradiation in solvents

NASA Astrophysics Data System (ADS)

Visbal, Heidy; Hirano, Minami; Omura, Takuya; Shimizu, Masahiro; Takaishi, Taigo; Hirao, Kazuyuki

2017-07-01

Mayenite (12CaO·7Al2O3) is a highly interesting functional material due to the wide variety of its possible future applications. In this study, we used femtosecond laser irradiation in several solvents with varying polarities to increase the specific surface area of 12CaO·7Al2O3 ceramics and reduce their particle size without any structural degradation or loss of crystallinity. We observed that when femtosecond laser irradiation was applied to solvents bearing hydroxyl groups, a smaller particle size was obtained with the particle size decreasing as the polarity of the solvent increased. Using infrared spectroscopy, we confirmed the presence of hydroxyl and carbonyl surface functional groups at the surface of 12CaO·7Al2O3 ceramics after femtosecond laser irradiation. This is attributed to the direct chemical bonds breaking of the solvent via multiphoton ionization and/or tunneling ionization, followed by the Coulomb explosion and the subsequent production of ions that are adsorbed on the surfaces of 12CaO·7Al2O3 ceramics. Femtosecond laser irradiation in polar solvents with hydroxyl groups can reduce the particle size and increase the specific surface area without degradation or loss of crystallinity of 12CaO·7Al2O3 ceramics. Additionally, this method can be used for the surface modification and introduction of functional groups on the 12CaO·7Al2O3 ceramics surface.

Where and What Is Pristine Marine Aerosol?

NASA Astrophysics Data System (ADS)

Russell, L. M.; Frossard, A. A.; Long, M. S.; Burrows, S. M.; Elliott, S.; Bates, T. S.; Quinn, P.

2014-12-01

The sources and composition of atmospheric marine aerosol particles have been measured by functional group composition (from Fourier transform infrared spectroscopy) to identify the organic composition of the pristine primary marine (ocean-derived) particles as 65% hydroxyl, 21% alkane, 6% amine, and 7% carboxylic acid functional groups [Frossard et al., 2014a,b]. Pristine but non-primary components from photochemical reactions (likely from biogenic marine vapor emissions) add carboxylic acid groups. Non-pristine contributions include shipping effluent in seawater and ship emissions, which add additional alkane groups (up to 70%), and coastal or continental emissions mix in alkane and carboxylic acid groups. The pristine primary marine (ocean-derived) organic aerosol composition is nearly identical to model generated primary marine aerosol particles from bubbled seawater, indicating that its overall functional group composition is the direct consequence of the organic constituents of the seawater source. While the seawater organic functional group composition was nearly invariant across all three ocean regions studied and the ratio of organic carbon to sodium (OC/Na+) in the generated primary marine aerosol particles remained nearly constant over a broad range of chlorophyll-a concentrations, the generated primary marine aerosol particle alkane group fraction increased with chlorophyll-a concentrations. In addition, the generated primary marine aerosol particles have a hydroxyl group absorption peak location characteristic of monosaccharides and disaccharides, where the seawater hydroxyl group peak location is closer to that of polysaccharides. References Cited Frossard, Amanda A., Lynn M. Russell, Paola Massoli, Timothy S. Bates, and Patricia K. Quinn, "Side-by-Side Comparison of Four Techniques Explains the Apparent Differences in the Organic Composition of Generated and Ambient Marine Aerosol Particles," Aerosol Science and Technology - Aerosol Research Letter, 48:v-x, doi10.1080/02786826.2013.879979, 2014a. Frossard, A.A., L.M. Russell, M.S. Long, S.M. Burrows, S.M. Elliot, T.S. Bates, and P.K. Quinn, "Sources and Composition of Submicron Organic Mass in Marine Aerosol Particles," Journal of Geophysical Research - Atmospheres, submitted 2014b.

Effect of Oxygen-containing Functional Groups on Protein Stability in Ionic Liquid Solutions

NASA Technical Reports Server (NTRS)

Turner, Megan B.; Holbrey, John D.; Spear, Scott K.; Pusey, Marc L.; Rogers, Robin D.

2004-01-01

The ability of functionalized ionic liquids (ILs) to provide an environment of increased stability for biomolecules has been studied. Serum albumin is an inexpensive, widely available protein that contributes to the overall colloid osmotic blood pressure within the vascular system. Albumin is used in the present study as a marker of biomolecular stability in the presence of various ILs in a range of concentrations. The incorporation of hydroxyl functionality into the methylimidazolium-based cation leads to increased protein stability detected by fluorescence spectroscopy and circular dichroic (CD) spectrometry.

No-carrier-added (NCA) aryl ([sup 18]F) fluorides via the nucleophilic aromatic substitution of electron rich aromatic rings

DOEpatents

Yushin Ding; Fowler, J.S.; Wolf, A.P.

1993-10-19

A method for synthesizing no-carrier-added (NCA) aryl [.sup.18 F] fluoride substituted aromatic aldehyde compositions bearing an electron donating group is described. The method of the present invention includes the step of reacting aromatic nitro aldehydes having a suitably protected hydroxyl substitutent on an electron rich ring. The reaction is The U.S. Government has rights in this invention pursuant to Contract Number DE-AC02-76CH00016, between the U.S. Department of Energy and Associated Universities Inc.

No-carrier-added (NCA) aryl (18E) fluorides via the nucleophilic aromatic substitution of electron rich aromatic rings

DOEpatents

Ding, Yu-Shin; Fowler, Joanna S.; Wolf, Alfred P.

1993-01-01

A method for synthesizing no-carrier-added (NCA) aryl [.sup.18 F] fluoride substituted aromatic aldehyde compositions bearing an electron donating group is described. The method of the present invention includes the step of reacting aromatic nitro aldehydes having a suitably protected hydroxyl substitutent on an electron rich ring. The reaction is The U.S. Government has rights in this invention pursuant to Contract Number DE-AC02-76CH00016, between the U.S. Department of Energy and Associated Universities Inc.

Exploring the effect of oxygen-containing functional groups on the water-holding capacity of lignite.

PubMed

Liu, Jie; Jiang, Xiangang; Cao, Yu; Zhang, Chen; Zhao, Guangyao; Zhao, Maoshuang; Feng, Li

2018-05-07

Graphene oxide with different degrees of oxidation was prepared and selected as a model compound of lignite to study quantitatively, using both experiment and theoretical calculation methods, the effect on water-holding capacity of oxygen-containing functional groups. The experimental results showed that graphite can be oxidized, and forms epoxy groups most easily, followed by hydroxyl and carboxyl groups. The prepared graphene oxide forms a membrane-state as a single layer structure, with an irregular surface. The water-holding capacity of lignite increased with the content of oxygen-containing functional groups. The influence on the configuration of water molecule clusters and binding energy of water molecules of different oxygen-containing functional groups was calculated by density functional theory. The calculation results indicated that the configuration of water molecule clusters was totally changed by oxygen-containing functional groups. The order of binding energy produced by oxygen-containing functional groups and water molecules was as follows: carboxyl > edge phenol hydroxyl >epoxy group. Finally, it can be concluded that the potential to form more hydrogen bonds is the key factor influencing the interaction energy between model compounds and water molecules.

Surface characteristics and bioactivity of oxide film on titanium metal formed by thermal oxidation.

PubMed

Park, Yeong-Joon; Song, Ho-Jun; Kim, In; Yang, Hong-So

2007-04-01

In this study, we characterized the surface of oxide film formed on titanium metal through the use of thermal treatment and investigated the effect of surface characteristics on the bioactivity of titanium. The as-received sample group was prepared by polishing and cleaning CP-Ti as a control group, and thermally oxidized sample groups were prepared by heat treating at 530, 600, 700, 800, 900, and 1000 degrees C respectively. Micro-morphology, crystalline structure, chemical composition, and binding state were evaluated using FE-SEM, XRD, and XPS. The bioactivity of sample groups was investigated by observing the degree of calcium phosphate formation from immersion testing in MEM. The surface characterization tests showed that hydroxyl group content in titanium oxide film was increased, as the density of titanium atoms was high and the surface area was large. In MEM immersion test, initial calcium phosphate formation was dependent upon the thickness of titanium oxide, and resultant calcium phosphate formation depended on the content of the hydroxyl group of the titanium oxide film surface.

2,3-trans-3,4-trans-3,4-Dihydroxy-L-proline: An amino acid in toxic peptides of Amanita virosa mushrooms

PubMed Central

Buku, A.; Faulstich, H.; Wieland, T.; Dabrowski, J.

1980-01-01

Among the four possible stereoisomers of 3,4-dihydroxy-L-proline,2,3-trans-3,4-trans-3,4-dihydroxy-L-proline (IV) had not been found in nature previously. It has now been detected as a component of virotoxins, toxic peptides of Amanita virosa mushrooms. Because periodate failed to effect an oxidative glycol splitting reaction, the two hydroxyl groups in positions 3 and 4 were expected to be in a trans configuration. Furthermore, the formation of a 4-lactone on treatment with acids pointed to the carboxyl group and the hydroxyl group at position 4 being in a cis configuration. These results are in agreement with structure IV only. Final proof for structure IV was given by NMR spectroscopy and direct comparison with the 2,3-cis-3,4-trans-3,4-dihydroxy-L-proline isomer. PMID:16592813

Structure-anti-MRSA activity relationship of macrocyclic bis(bibenzyl) derivatives.

PubMed

Sawada, Hiromi; Onoda, Kenji; Morita, Daichi; Ishitsubo, Erika; Matsuno, Kenji; Tokiwa, Hiroaki; Kuroda, Teruo; Miyachi, Hiroyuki

2013-12-15

We synthesized a series of macrocyclic bis(bibenzyl) derivatives, including riccardin-, isoplagiochin- and marchantin-class structures, and evaluated their antibacterial activity towards methicillin-resistant Staphylococcus aureus (anti-MRSA activity). The structure-activity relationships and the results of molecular dynamics simulations indicated that bis(bibenzyl)s with potent anti-MRSA activity commonly have a 4-hydroxyl group at the D-benzene ring and a 2-hydroxyl group at the C-benzene ring in the hydrophilic part of the molecule, and an unsubstituted phenoxyphenyl group in the hydrophobic part of the molecule containing the A-B-benzene rings. Pharmacological characterization of the bis(bibenzyl) derivatives and 2-phenoxyphenol fragment 25, previously proposed as the minimum structure of riccardin C 1 for anti-MRSA activity, indicated that they have different action mechanisms: the bis(bibenzyl)s are bactericidal, while 25 is bacteriostatic, showing only weak bactericidal activity. Copyright © 2013 Elsevier Ltd. All rights reserved.

Regioselective Galactofuranosylation for the Synthesis of Disaccharide Patterns Found in Pathogenic Microorganisms.

PubMed

Legentil, Laurent; Cabezas, Yari; Tasseau, Olivier; Tellier, Charles; Daligault, Franck; Ferrières, Vincent

2017-07-21

Koenigs-Knorr glycosylation of acceptors with more than one free hydroxyl group by 2,3,5,6-tetrabenzoyl galactofuranosyl bromide was performed using diphenylborinic acid 2-aminoethyl ester (DPBA) as inducer of regioselectivity. High regioselectivity for the glycosylation on the equatorial hydroxyl group of the acceptor was obtained thanks to the transient formation of a borinate adduct of the corresponding 1,2-cis diol. Nevertheless formation of orthoester byproducts hampered the efficiency of the method. Interestingly electron-withdrawing groups on O-6 or on C-1 of the acceptor displaced the reaction in favor of the desired galactofuranosyl containing disaccharide. The best yield was obtained for the furanosylation of p-nitrophenyl 6-O-acetyl mannopyranoside. Precursors of other disaccharides, found in the glycocalix of some pathogens, were synthesized according to the same protocol with yields ranging from 45 to 86%. This is a good alternative for the synthesis of biologically relevant glycoconjugates.

Substitution effect on a hydroxylated chalcone: Conformational, topological and theoretical studies

NASA Astrophysics Data System (ADS)

Custodio, Jean M. F.; Vaz, Wesley F.; de Andrade, Fabiano M.; Camargo, Ademir J.; Oliveira, Guilherme R.; Napolitano, Hamilton B.

2017-05-01

The effect of substituents on two hydroxylated chalcones was studied in this work. The first chalcone, with a dimethylamine group (HY-DAC) and the second, with three methoxy groups (HY-TRI) were synthesized and crystallized from ethanol on centrosymmetric space group P21/c. The geometric parameters and supramolecular arrangement for both structures obtained from single crystal X-ray diffraction data were analyzed. The intermolecular interactions were investigated by Hirshfeld surfaces with their respective 2D plot for quantification of each type of contact. Additionally, the observed interactions were characterized by QTAIM analysis, and DFT calculations were applied for theoretical vibrational spectra, localization and quantification of frontier orbitals and potential electrostatic map. The flatness of both structures was affected by the substituents, which led to different monoclinic crystalline packing. The calculated harmonic vibrational frequencies and homo-lumo gap confirmed the stability of the structures, while intermolecular interactions were confirmed by potential electrostatic map and QTAIM analysis.

Effect of Agitation in Alkalization Process on the Characteristics of Sodium Carboxymethyl Sago and Cassava Starches

NASA Astrophysics Data System (ADS)

Titi, C. S.; Fachrudin, R.; Ruriani, E.; Yuliasih, I.

2018-05-01

Sodium carboxymethyl starch (Sodium CMS) is a modified starch prepared by two successive processes, alkalization and etherification. Alkalization will change the activated hydroxyl group of starch to more reactive alkoxide (St-O-), and then carboxymethyl group will substitute the hydroxyl group into sodium CMS. This research investigated the effect of agitation (1000 rpm of stirring and 4000 rpm of homogenization) in alkalization process to the modification of native starch into sodium CMS. Cassava and sago starches were mixed with sodium hydroxide (1.8 and 1.9 moles per mole anhydrous glucose units). The combination of NaOH and homogenizing gave the highest degrees of substitution for cassava (DS 0.73) and sago (DS 0.55) starches. The sodium CMS characteristics (paste clarity, water and oil absorption capacities, solubility, swelling power) were a function of mixing method but not on the amount of NaOH used.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tang, Mingyi; Xu, Xiaoyang, E-mail: xiaoyangxu2012@163.com; Wu, Tao

Highlights: • Graphene oxide (GO) was modified by chemical reactions to functionalized GO (FGO). • The FGOs and the GO were then subjected to in situ free radical polymerization. • Hydroxyl groups of GO were the most reactive grafting sites. - Abstract: Graphene oxide (GO) was modified using chemical reactions to obtain three types of functionalized GO sheets (FGO). The FGO sheets and the GO were then subjected to in situ free radical polymerization in order to study the grafting polymerization. The FGO and grafted-.FGO were analyzed with Fourier transform infrared spectroscopy, scanning electronic microscopy, thermo-gravimetric analysis (TGA) and X-raymore » photoelectron spectroscopy (XPS). The grafting percentages in the materials were calculated using the TGA and XPS results. The FGO sheets with different functional groups exhibited different grafting abilities, and hydroxyl groups were proven to be the most reactive grafting sites for the in situ free radical grafting polymerization of polyacrylamide.« less

Influence of Functional Groups on the Viscosity of Organic Aerosol.

PubMed

Rothfuss, Nicholas E; Petters, Markus D

2017-01-03

Organic aerosols can exist in highly viscous or glassy phase states. A viscosity database for organic compounds with atmospherically relevant functional groups is compiled and analyzed to quantify the influence of number and location of functional groups on viscosity. For weakly functionalized compounds the trend in viscosity sensitivity to functional group addition is carboxylic acid (COOH) ≈ hydroxyl (OH) > nitrate (ONO 2 ) > carbonyl (CO) ≈ ester (COO) > methylene (CH 2 ). Sensitivities to group addition increase with greater levels of prior functionalization and decreasing temperature. For carboxylic acids a sharp increase in sensitivity is likely present already at the second addition at room temperature. Ring structures increase viscosity relative to linear structures. Sensitivities are correlated with analogously derived sensitivities of vapor pressure reduction. This may be exploited in the future to predict viscosity in numerical models by piggybacking on schemes that track the evolution of organic aerosol volatility with age.

Visible-near infrared spectra of hydrous carbonates, with implications for the detection of carbonates in hyperspectral data of Mars

NASA Astrophysics Data System (ADS)

Harner, Patrick L.; Gilmore, Martha S.

2015-04-01

We present visible-near infrared (VNIR, 0.35-5 μm) spectra for a suite of hydrous carbonates that may be relevant to the surface of Mars. This includes VNIR spectra for ikaite, nesquehonite, synthetic monohydrocalcite and lansfordite over the 0.35-2.5 μm range that are new to the literature. The spectral features of the hydrous carbonates are dominated by absorptions at ∼1.0, 1.2, 1.4-1.5, 1.9 and 2.8 μm that are due to overtones and combinations of fundamental water and hydroxyl vibrations. Absorptions due to (CO3)2-, Mg-OH, Fe-OH, and/or water are seen at ∼2.3-2.5, 3.4, and 3.9 μm in hydrous Mg and Mg-Fe3+ carbonates containing hydroxyl groups, but are weaker than in the common anhydrous carbonates. When present in the hydrous carbonates, the positions of the centers of the 2.3 μm and/or 2.5 μm absorptions are often shifted relative to the anhydrous carbonates, which may be diagnostic. Some or all of the (CO3)2- absorptions typical of anhydrous carbonates are weak to absent in the hydrous carbonates, and thus this group may be difficult to distinguish from other hydrous minerals like sulfates, phyllosilicates or chlorides in Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) data using standard spectral search parameters for anhydrous carbonates. We present strategies for recognizing hydrous carbonates in CRISM data using combinations of spectral parameters that measure the intensity and shape of the water-related absorptions in these minerals.

Removal of 2,4-D from aqueous solutions by adsorption processes using two biopolymers: chitin and chitosan and their optical properties

NASA Astrophysics Data System (ADS)

El Harmoudi, H.; El Gaini, L.; Daoudi, E.; Rhazi, M.; Boughaleb, Y.; El Mhammedi, M. A.; Migalska-Zalas, A.; Bakasse, M.

2014-07-01

Chitin, extracted primarily from exoskeleton shellfish, is one of the most abundant biopolymer in the world. It is estimated to be produced annually almost as much as cellulose. The development of fishing activities in Morocco (coastline of 3500 km on both the Atlantic and the Mediterranean) induced an important fish industry waste. The aim of this work is to recover chitin, extracted from shellfish waste, and chitosan, produced by deacetylation of chitin, in the adsorption of organic pesticide 2,4-dichlorophenoxyacetate (2,4-D). The chitosan samples were prepared from chitin from crustacean shells. The chitin deacetylation was carried out in aqueous sodium hydroxide. Characterization of chitin and chitosan was performed by infrared spectroscopy, nuclear magnetic resonance and theoretical calculation of UV-Vis spectra and optical parameters. Analysis of theoretical spectra shows a substantial sensitivity to the hydroxyl and amino groups. The presented hydroxyl group in chitin determines the conformation of the molecule and also the stereochemistry of chemical reactions and kinetics. The presence of functional groups causes the substantial changes of both absorption spectra as well as permanent dipole moment. The adsorption of 2,4-D by chitin and chitosan was performed at different pH values, the pesticide-adsorbent contact time and initial pesticide concentration. The adsorption is described by Langmuir-type isotherm and Freundlich-type isotherm. Recovery tests of 2,4-D confirm the initial interest in using chitin and chitosan as a depolluting agent.

IRON(III) NITRATE-CATALYZED FACILE SYNTHESIS OF DIPHENYLMETHYL (DPM) ETHERS FROM ALCOHOLS

EPA Science Inventory

Diphenyl methyl (DPM) ethers constitute important structural portion of some pharmaceutical entities and also as protective group for hydroxyl groups in synthetic chemistry. DPM ethers are normally prepared using concentrated acids or base as catalysts, which may result in the fo...

Producing Lignin-Based Polyols through Microwave-Assisted Liquefaction for Rigid Polyurethane Foam Production.

PubMed

Xue, Bai-Liang; Wen, Jia-Long; Sun, Run-Cang

2015-02-10

Lignin-based polyols were synthesized through microwave-assisted liquefaction under different microwave heating times (5-30 min). The liquefaction reactions were carried out using polyethylene glycol (PEG-400)/glycerol as liquefying solvents and 97 wt% sulfur acid as a catalyst at 140 °C. The polyols obtained were analyzed for their yield, composition and structural characteristics using gel permeation chromatography (GPC), Fourier transform infrared (FT-IR) and nuclear magnetic resonance (NMR) spectra. FT-IR and NMR spectra showed that the liquefying solvents reacted with the phenol hydroxyl groups of the lignin in the liquefied product. With increasing microwave heating time, the viscosity of polyols was slightly increased and their corresponding molecular weight ( M W ) was gradually reduced. The optimal condition at the microwave heating time (5 min) ensured a high liquefaction yield (97.47%) and polyol with a suitable hydroxyl number (8.628 mmol/g). Polyurethane (PU) foams were prepared by polyols and methylene diphenylene diisocyanate (MDI) using the one-shot method. With the isocyanate/hydroxyl group ([NCO]/[OH]) ratio increasing from 0.6 to 1.0, their mechanical properties were gradually increased. This study provided some insight into the microwave-assisted liquefied lignin polyols for the production of rigid PU foam.

Hydroxylated chalcones with dual properties: xanthine oxidase inhibitors and radical scavengers

PubMed Central

Hofmann, Emily; Webster, Jonathan; Do, Thuy; Kline, Reid; Snider, Lindsey; Hauser, Quintin; Higginbottom, Grace; Campbell, Austin; Ma, Lili; Paula, Stefan

2016-01-01

In this study, we evaluated the abilities of a series of chalcones to inhibit the activity of the enzyme xanthine oxidase (XO) and to scavenge radicals. 20 mono- and polyhydroxylated chalcone derivatives were synthesized by Claisen-Schmidt condensation reactions and then tested for inhibitory potency against XO, a known generator of reactive oxygen species (ROS). In parallel, the ability of the synthesized chalcones to scavenge a stable radical was determined. Structure-activity relationship analysis in conjunction with molecular docking indicated that the most active XO inhibitors carried a minimum of three hydroxyl groups. Moreover, the most effective radical scavengers had two neighboring hydroxyl groups on at least one of the two phenyl rings. Since it has been proposed previously that XO inhibition and radical scavenging could be useful properties for reduction of ROS-levels in tissue, we determined the chalcones’ effects to rescue neurons subjected to ROS-induced stress created by the addition of β-amyloid peptide. Best protection was provided by chalcones that combined good inhibitory potency with high radical scavenging ability in a single molecule, an observation that points to a potential therapeutic value of this compound class. PMID:26762836

Fine Tuning of Antibiotic Activity by a Tailoring Hydroxylase in a Trans-AT Polyketide Synthase Pathway.

PubMed

Mohammad, Hadi H; Connolly, Jack A; Song, Zhongshu; Hothersall, Joanne; Race, Paul R; Willis, Christine L; Simpson, Thomas J; Winn, Peter J; Thomas, Christopher M

2018-04-16

The addition or removal of hydroxy groups modulates the activity of many pharmacologically active biomolecules. It can be integral to the basic biosynthetic factory or result from associated tailoring steps. For the anti-MRSA antibiotic mupirocin, removal of a C8-hydroxy group late in the biosynthetic pathway gives the active pseudomonic acid A. An extra hydroxylation, at C4, occurs in the related but more potent antibiotic thiomarinol A. We report here in vivo and in vitro studies that show that the putative non-haem-iron(II)/α-ketoglutaratedependent dioxygenase TmuB, from the thiomarinol cluster, 4-hydroxylates various pseudomonic acids whereas C8-OH, and other substituents around the tetrahydropyran ring, block enzyme action but not substrate binding. Molecular modelling suggested a basis for selectivity, but mutation studies had a limited ability to rationally modify TmuB substrate specificity. 4-Hydroxylation had opposite effects on the potency of mupirocin and thiomarinol. Thus, TmuB can be added to the toolbox of polyketide tailoring technologies for the in vivo generation of new antibiotics in the future. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Comparative Study of Surface Chemical Composition and Oxide Layer Modification upon Oxygen Plasma Cleaning and Piranha Etching on a Novel Low Elastic Modulus Ti25Nb21Hf Alloy

NASA Astrophysics Data System (ADS)

Paredes, Virginia; Salvagni, Emiliano; Rodríguez-Castellón, Enrique; Manero, José María

2017-08-01

Metals are widely employed for many biological artificial replacements, and it is known that the quality and the physical/chemical properties of the surface are crucial for the success of the implant. Therefore, control over surface implant materials and their elastic moduli may be crucial to avoid undesired effects. In this study, surface modification upon cleaning and activation of a low elastic modulus Ti alloy (Ti25Hf21Nb) was investigated. Two different methods, oxygen plasma (OP) cleaning and piranha (PI) solution, were studied and compared. Both surface treatments were effective for organic contaminant removal and to increase the Ti-oxide layer thickness rather than other metal-oxides present at the surface, which is beneficial for biocompatibility of the material. Furthermore, both techniques drastically increased hydrophilicity and introduced oxidation and hydroxylation (OH)-functional groups at the surface that may be beneficial for further chemical modifications. However, these treatments did not alter the surface roughness and bulk material properties. The surfaces were fully characterized in terms of surface roughness, wettability, oxide layer composition, and hydroxyl surface density through analytical techniques (interferometry, X-ray photoelectron spectroscopy (XPS), contact angle, and zinc complexation). These findings provide essential information when planning surface modifications for cleanliness, oxide layer thickness, and surface hydroxyl density, as control over these factors is essential for many applications, especially in biomaterials.

Effect of surface hydroxyl groups on heat capacity of mesoporous silica

NASA Astrophysics Data System (ADS)

Marszewski, Michal; Butts, Danielle; Lan, Esther; Yan, Yan; King, Sophia C.; McNeil, Patricia E.; Galy, Tiphaine; Dunn, Bruce; Tolbert, Sarah H.; Hu, Yongjie; Pilon, Laurent

2018-05-01

This paper quantifies the effect of surface hydroxyl groups on the effective specific and volumetric heat capacities of mesoporous silica. To achieve a wide range of structural diversity, mesoporous silica samples were synthesized by various methods, including (i) polymer-templated nanoparticle-based powders, (ii) polymer-templated sol-gel powders, and (iii) ambigel silica samples dried by solvent exchange at room temperature. Their effective specific heat capacity, specific surface area, and porosity were measured using differential scanning calorimetry and low-temperature nitrogen adsorption-desorption measurements. The experimentally measured specific heat capacity was larger than the conventional weight-fraction-weighted specific heat capacity of the air and silica constituents. The difference was attributed to the presence of OH groups in the large internal surface area. A thermodynamic model was developed based on surface energy considerations to account for the effect of surface OH groups on the specific and volumetric heat capacity. The model predictions fell within the experimental uncertainty.

PPIB mutations cause severe osteogenesis imperfecta.

PubMed

van Dijk, Fleur S; Nesbitt, Isabel M; Zwikstra, Eline H; Nikkels, Peter G J; Piersma, Sander R; Fratantoni, Silvina A; Jimenez, Connie R; Huizer, Margriet; Morsman, Alice C; Cobben, Jan M; van Roij, Mirjam H H; Elting, Mariet W; Verbeke, Jonathan I M L; Wijnaendts, Liliane C D; Shaw, Nick J; Högler, Wolfgang; McKeown, Carole; Sistermans, Erik A; Dalton, Ann; Meijers-Heijboer, Hanne; Pals, Gerard

2009-10-01

Deficiency of cartilage-associated protein (CRTAP) or prolyl 3-hydroxylase 1(P3H1) has been reported in autosomal-recessive lethal or severe osteogenesis imperfecta (OI). CRTAP, P3H1, and cyclophilin B (CyPB) form an intracellular collagen-modifying complex that 3-hydroxylates proline at position 986 (P986) in the alpha1 chains of collagen type I. This 3-prolyl hydroxylation is decreased in patients with CRTAP and P3H1 deficiency. It was suspected that mutations in the PPIB gene encoding CyPB would also cause OI with decreased collagen 3-prolyl hydroxylation. To our knowledge we present the first two families with recessive OI caused by PPIB gene mutations. The clinical phenotype is compatible with OI Sillence type II-B/III as seen with COL1A1/2, CRTAP, and LEPRE1 mutations. The percentage of 3-hydroxylated P986 residues in patients with PPIB mutations is decreased in comparison to normal, but it is higher than in patients with CRTAP and LEPRE1 mutations. This result and the fact that CyPB is demonstrable independent of CRTAP and P3H1, along with reported decreased 3-prolyl hydroxylation due to deficiency of CRTAP lacking the catalytic hydroxylation domain and the known function of CyPB as a cis-trans isomerase, suggest that recessive OI is caused by a dysfunctional P3H1/CRTAP/CyPB complex rather than by the lack of 3-prolyl hydroxylation of a single proline residue in the alpha1 chains of collagen type I.

Zeta Potential Measurements on Solid Surfaces for in Vitro Biomaterials Testing: Surface Charge, Reactivity Upon Contact With Fluids and Protein Absorption

PubMed Central

Ferraris, Sara; Cazzola, Martina; Peretti, Veronica; Stella, Barbara; Spriano, Silvia

2018-01-01

Surface properties of biomaterials (e.g., roughness, chemical composition, charge, wettability, and hydroxylation degree) are key features to understand and control the complex interface phenomena that happens upon contact with physiological fluids. Numerous physico-chemical techniques can be used in order to investigate in depth these crucial material features. Among them, zeta potential measurements are widely used for the characterization of colloidal suspensions, but actually poorly explored in the study of solid surfaces, even if they can give significant information about surface charge in function of pH and indirectly about surface functional groups and reactivity. The aim of the present research is application of zeta potential measurements of solid surfaces for the in vitro testing of biomaterials. In particular, bare and surface modified Ti6Al4V samples have been compared in order to evaluate their isoelectric points (IEPs), surface charge at physiological pH, in vitro bioactivity [in simulated body fluid (SBF)] and protein absorption. Zeta potential titration was demonstrated as a suitable technique for the surface characterization of surface treated Ti6Al4V substrates. Significant shift of the isoelectric point was recorded after a chemical surface treatment (because of the exposition of hydroxyl groups), SBF soaking (because of apatite precipitation IEP moves close to apatite one) and protein absorption (IEP moves close to protein ones). Moreover, the shape of the curve gives information about exposed functional groups (e.g., a plateau in the basic range appears due to the exposition of acidic OH groups and in the acidic range due to exposition of basic NH2 groups). PMID:29868575

Crystal Structure of the Catalytic Domain of Drosophila [beta]1,4-Galactosyltransferase-7

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ramakrishnan, Boopathy; Qasba, Pradman K.

2010-11-03

The {beta}1,4-galactosyltransferase-7 ({beta}4Gal-T7) enzyme, one of seven members of the {beta}4Gal-T family, transfers in the presence of manganese Gal from UDP-Gal to an acceptor sugar (xylose) that is attached to a side chain hydroxyl group of Ser/Thr residues of proteoglycan proteins. It exhibits the least protein sequence similarity with the other family members, including the well studied family member {beta}4Gal-T1, which, in the presence of manganese, transfers Gal from UDP-Gal to GlcNAc. We report here the crystal structure of the catalytic domain of {beta}4Gal-T7 from Drosophila in the presence of manganese and UDP at 1.81 {angstrom} resolution. In the crystalmore » structure, a new manganese ion-binding motif (HXH) has been observed. Superposition of the crystal structures of {beta}4Gal-T7 and {beta}4Gal-T1 shows that the catalytic pocket and the substrate-binding sites in these proteins are similar. Compared with GlcNAc, xylose has a hydroxyl group (instead of an N-acetyl group) at C2 and lacks the CH{sub 2}OH group at C5; thus, these protein structures show significant differences in their acceptor-binding site. Modeling of xylose in the acceptor-binding site of the {beta}4Gal-T7 crystal structure shows that the aromatic side chain of Tyr{sup 177} interacts strongly with the C5 atom of xylose, causing steric hindrance to any additional group at C5. Because Drosophila Cd7 has a 73% protein sequence similarity to human Cd7, the present crystal structure offers a structure-based explanation for the mutations in human Cd7 that have been linked to Ehlers-Danlos syndrome.« less

Synthesis of novel benzohydrazone-oxadiazole hybrids as β-glucuronidase inhibitors and molecular modeling studies.

PubMed

Taha, Muhammad; Ismail, Nor Hadiani; Imran, Syahrul; Selvaraj, Manikandan; Rahim, Abdul; Ali, Muhammad; Siddiqui, Salman; Rahim, Fazal; Khan, Khalid Mohammed

2015-12-01

A series of compounds consisting of 25 novel oxadiazole-benzohydrazone hybrids (6-30) were synthesized through a five-step reaction sequence and evaluated for their β-glucuronidase inhibitory potential. The IC50 values of compounds 6-30 were found to be in the range of 7.14-44.16μM. Compounds 6, 7, 8, 9, 11, 13, 18, and 25 were found to be more potent than d-saccharic acid 1,4-lactone (48.4±1.25μM). These compounds were further subjected for molecular docking studies to confirm the binding mode towards human β-d-glucuronidase active site. Docking study for compound 13 (IC50=7.14±0.30μM) revealed that it adopts a binding mode that fits within the entire pocket of the binding site of β-d-glucuronidase. Compound 13 has the maximum number of hydrogens bonded to the residues of the active site as compared to the other compounds, that is, the ortho-hydroxyl group forms hydrogen bond with carboxyl side chain of Asp207 (2.1Å) and with hydroxyl group of Tyr508 (2.6Å). The other hydroxyl group forms hydrogen bond with His385 side chain (2.8Å), side chain carboxyl oxygen of Glu540 (2.2Å) and Asn450 side-chain's carboxamide NH (2.1Å). Copyright © 2015 Elsevier Ltd. All rights reserved.

Molecular interactions in nanocellulose assembly

NASA Astrophysics Data System (ADS)

Nishiyama, Yoshiharu

2017-12-01

The contribution of hydrogen bonds and the London dispersion force in the cohesion of cellulose is discussed in the light of the structure, spectroscopic data, empirical molecular-modelling parameters and thermodynamics data of analogue molecules. The hydrogen bond of cellulose is mainly electrostatic, and the stabilization energy in cellulose for each hydrogen bond is estimated to be between 17 and 30 kJ mol-1. On average, hydroxyl groups of cellulose form hydrogen bonds comparable to those of other simple alcohols. The London dispersion interaction may be estimated from empirical attraction terms in molecular modelling by simple integration over all components. Although this interaction extends to relatively large distances in colloidal systems, the short-range interaction is dominant for the cohesion of cellulose and is equivalent to a compression of 3 GPa. Trends of heat of vaporization of alkyl alcohols and alkanes suggests a stabilization by such hydroxyl group hydrogen bonding to be of the order of 24 kJ mol-1, whereas the London dispersion force contributes about 0.41 kJ mol-1 Da-1. The simple arithmetic sum of the energy is consistent with the experimental enthalpy of sublimation of small sugars, where the main part of the cohesive energy comes from hydrogen bonds. For cellulose, because of the reduced number of hydroxyl groups, the London dispersion force provides the main contribution to intermolecular cohesion. This article is part of a discussion meeting issue `New horizons for cellulose nanotechnology'.

CO 2 hydrogenation catalyzed by iridium complexes with a proton-responsive ligand

DOE PAGES

Onishi, Naoya; Xu, Shaoan; Manaka, Yuichi; ...

2015-02-18

In this study, the catalytic cycle for the production of formic acid by CO₂ hydrogenation and the reverse reaction has received renewed attention because they are viewed as offering a viable scheme for hydrogen storage and release. In this Forum Article, CO₂ hydrogenation catalyzed by iridium complexes bearing N^N-bidentate ligands is reported. We describe how a ligand containing hydroxyl groups as proton-responsive substituents enhances catalytic performance by an electronic effect of the oxyanions and a pendent-base effect through secondary coordination sphere interaction. In particular, [(Cp*IrCl)₂(TH2BPM)]Cl₂ (Cp* = pentamethyl cyclopentadienyl, TH2BPM = 4,4',6,6'-tetrahydroxy-2,2'-bipyrimidine) promotes enormously the catalytic hydrogenation of CO₂ bymore » these synergistic effects under atmospheric pressure and at room temperature. Additionally, newly designed complexes with azole-type ligands are applied to CO₂ hydrogenation. The catalytic efficiencies of the azole-type complexes are much higher than that of the unsubstituted bipyridine complex [Cp*Ir(bpy)(OH₂)]SO₄. Furthermore, the introduction of one or more hydroxyl groups into ligands such as 2-pyrazolyl-6-hydroxypyridine, 2-pyrazolyl-4,6-dihydroxyl pyrimidine, and 4-pyrazolyl-2,6-dihydroxyl pyrimidine enhanced catalytic activity. It is clear that the incorporation of electron-donating hydroxyl groups into proton-responsive ligands is effective for promoting the hydrogenation of CO₂.« less

Polychlorinated biphenyls and their hydroxylated metabolites in the serum of e-waste dismantling workers from eastern China.

PubMed

Ma, Shengtao; Ren, Guofa; Zeng, Xiangying; Yu, Zhiqiang; Sheng, Guoying; Fu, Jiamo

2017-05-05

A number of studies have reported on the exposure of e-waste dismantling workers to significantly high concentrations of halogenated organic pollutants such as polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers. Such exposure can have adverse health effects. However, little information on the metabolites of these contaminants exists. In this study, we investigated PCBs levels and their hydroxylated metabolites (OH-PCB) in the serum of e-waste workers in Taizhou in eastern China. Our results indicate elevated PCB and OH-PCB levels in the serum of the workers, with medians of 443.7 and 133.9 ng/g lw, respectively. Tri- to hexachlorinated PCB congeners were the dominant homologue groups in all of the samples. 4-OH-CB107 was the predominant homologue among the hydroxylated metabolites, accounting for 88.9% of the total OH-PCB concentrations. While dietary sources (e.g., fish) appear to be an important route for PCB accumulation in non-occupational exposure groups, exposure via ingestion of house dust and inhalation of pollutants derived from the recycling of PCB-containing e-wastes may primarily contribute to the high body burden observed in the occupational groups. Since we found concentrations of metabolites higher than those of their parent compounds, further studies need to pay more attention to their bioaccumulation and toxicity.

Isolation and identification of metabolites of osthole in rats.

PubMed

Lv, X; Wang, C-Y; Hou, J; Zhang, B-J; Deng, S; Tian, Y; Huang, S-S; Zhang, H-L; Shu, X-H; Zhen, Y-H; Liu, K-X; Yao, J-H; Ma, X-C

2012-11-01

Osthole (Ost), one of the major components of Cnidium monnieri (L.) Cusson, is had the structure of an isopentenoxy-coumarin with a range of pharmacological activities. In the present study, the metabolism of Ost in male Sprague-Dawley rats was investigated by identifying Ost metabolites excreted in rat urine. Following an oral dose of 40 mg/kg Ost, 10 phase I and 3 phase II metabolites were isolated from the urine of rats, and their structures identified on the basis of a range of spectroscopic data, including 2D-NMR techniques. These metabolites were fully characterized as 5'-hydroxyl-osthole (M-1), osthenol (M-2), 4'-hydroxyl-osthole (M-3), 3, 5'-dihydroxyl-osthole (M-4), 5'-hydroxyl-osthenol (M-5), 4'-hydroxyl-2', 3'-dihydro-osthenol (M-6), 4'-hydroxyl-osthenol (M-7), 3, 4'-dihydroxyl-osthole (M-8), 2', 3'-dihydroxyl-osthole (M-9), 5'-hydroxyl-2', 3'-dihydroosthole (M-10), osthenol-7-O-β-D-glucuronide (M-11), osthole-4'-O-β-D-glucuronide (M-12) and osthole-5'-O-β-D-glycuronate (M-13). This is the first identification of M-1, M-3 to M-13 in vivo. On the basis of the metabolites profile, a possible metabolic pathway for Ost metabolism in rats has been proposed. This is the first systematic study on the phases I and II metabolites of 8-isopentenoxy-coumarin derivative.

Characterization and in vitro antioxidant activity of Albizia stipulata Boiv. gum exudates.

PubMed

Thanzami, K; Malsawmtluangi, C; Lalhlenmawia, H; Seelan, T Veenus; Palanisamy, Selvamani; Kandasamy, Ruckmani; Pachuau, Lalduhsanga

2015-09-01

The objective of the present study is to characterize the physicochemical properties and to determine the in vitro antioxidant activity of Albizia stipulata Boiv. gum exudates collected from Northeast India. The total carbohydrate, uronic acid and protein contents, monosaccharide composition and the molecular weight distribution of the purified gum was determined. The powder flow property and preliminary compressibility test were performed on the dried gum exudates. Fourier transform infrared spectroscopy (FTIR) study was performed to analyze the functional groups present in the structure. Differential scanning calorimetry (DSC) and thermogravimetry (TGA/DTA) analyses were performed to study the thermal stability of the gum. The antioxidant properties of the gum were evaluated by determining 2,2-diphenyl-1-picrylhydrazyl (DPPH), hydroxyl scavenging activities and reducing power. The total carbohydrate and protein contents of the gum were found to be 75.17±3.21% and 2.60±1.05% respectively. The viscosity of 2% aqueous solution of the gum exhibited non-Newtonian type of flow showing pH dependent swelling. Arabinose and galactose were found to be the main monosaccharides present in the gum exudates and the molecular weight distribution of the gum was also found to be polydispersed. Results from DPPH, hydroxyl scavenging and reducing power studies showed the gum possesses antioxidant properties. Copyright © 2015 Elsevier B.V. All rights reserved.

Mechanistic Study on Electron Capture Dissociation of the Oligosaccharide-Mg2+ Complex

NASA Astrophysics Data System (ADS)

Huang, Yiqun; Pu, Yi; Yu, Xiang; Costello, Catherine E.; Lin, Cheng

2014-08-01

Electron capture dissociation (ECD) has shown great potential in structural characterization of glycans. However, our current understanding of the glycan ECD process is inadequate for accurate interpretation of the complex glycan ECD spectra. Here, we present the first comprehensive theoretical investigation on the ECD fragmentation behavior of metal-adducted glycans, using the cellobiose-Mg2+ complex as the model system. Molecular dynamics simulation was carried out to determine the typical glycan-Mg2+ binding patterns and the lowest-energy conformer identified was used as the initial geometry for density functional theory-based theoretical modeling. It was found that the electron is preferentially captured by Mg2+ and the resultant Mg+• can abstract a hydroxyl group from the glycan moiety to form a carbon radical. Subsequent radical migration and α-cleavage(s) result in the formation of a variety of product ions. The proposed hydroxyl abstraction mechanism correlates well with the major features in the ECD spectrum of the Mg2+-adducted cellohexaose. The mechanism presented here also predicts the presence of secondary, radical-induced fragmentation pathways. These secondary fragment ions could be misinterpreted, leading to erroneous structural determination. The present study highlights an urgent need for continuing investigation of the glycan ECD mechanism, which is imperative for successful development of bioinformatics tools that can take advantage of the rich structural information provided by ECD of metal-adducted glycans.

How does the axial ligand of cytochrome P450 biomimetics influence the regioselectivity of aliphatic versus aromatic hydroxylation?

PubMed

de Visser, Sam P; Tahsini, Laleh; Nam, Wonwoo

2009-01-01

The catalytic activity of high-valent iron-oxo active species of heme enzymes is known to be dependent on the nature of the axial ligand trans to the iron-oxo group. In a similar fashion, experimental studies on iron-oxo porphyrin biomimetic systems have shown a significant axial ligand effect on ethylbenzene hydroxylation, with an axial acetonitrile ligand leading to phenyl hydroxylation products and an axial chloride anion giving predominantly benzyl hydroxylation products. To elucidate the fundamental factors that distinguish this regioselectivity reversal in iron-oxo porphyrin catalysis, we have performed a series of density functional theory calculations on the hydroxylation of ethylbenzene by [Fe(IV)=O(Por(+.))L] (Por = porphyrin; L = NCCH(3) or Cl(-)), which affords 1-phenylethanol and p-ethylphenol products. The calculations confirm the experimentally determined product distributions. Furthermore, a detailed analysis of the electronic differences between the two oxidants shows that their reversed regioselectivity is a result of differences in orbital interactions between the axial ligand and iron-oxo porphyrin system. In particular, three high-lying orbitals (pi*(xz), pi*(yz) and a(2u)), which are singly occupied in the reactant complex, are stabilised with an anionic ligand such as Cl(-), which leads to enhanced HOMO-LUMO energy gaps. As a consequence, reactions leading to cationic intermediates through the two-electron reduction of the metal centre are disfavoured. The aliphatic hydroxylation mechanism, in contrast, is a radical process in which only one electron is transferred in the rate-determining transition state, which means that the effect of the axial ligand on this mechanism is much smaller.

Hydroxylated PBDEs induce developmental arrest in zebrafish

DOE Office of Scientific and Technical Information (OSTI.GOV)

Usenko, Crystal Y., E-mail: Crystal_usenko@baylor.edu; Hopkins, David C.; Trumble, Stephen J., E-mail: Stephen_trumble@baylor.edu

The ubiquitous spread of polybrominated diphenyl ethers (PBDEs) has led to concerns regarding the metabolites of these congeners, in particular hydroxylated PBDEs. There are limited studies regarding the biological interactions of these chemicals, yet there is some concern they may be more toxic than their parent compounds. In this study three hydroxylated PBDEs were assessed for toxicity in embryonic zebrafish: 3-OH-BDE 47, 5-OH-BDE 47, and 6-OH-BDE 47. All three congeners induced developmental arrest in a concentration-dependent manner; however, 6-OH-BDE 47 induced adverse effects at lower concentrations than the other congeners. Furthermore, all three induced cell death; however apoptosis was notmore » observed. In short-term exposures (24–28 hours post fertilization), all hydroxylated PBDEs generated oxidative stress in the region corresponding to the cell death at 5 and 10 ppm. To further investigate the short-term effects that may be responsible for the developmental arrest observed in this study, gene regulation was assessed for embryos exposed to 0.625 ppm 6-OH-BDE 47 from 24 to 28 hpf. Genes involved in stress response, thyroid hormone regulation, and neurodevelopment were significantly upregulated compared to controls; however, genes related to oxidative stress were either unaffected or downregulated. This study suggests that hydroxylated PBDEs disrupt development, and may induce oxidative stress and potentially disrupt the cholinergic system and thyroid hormone homeostasis. -- Highlights: ► OH-PBDEs induce developmental arrest in a concentration-dependent manner. ► Hydroxyl group location influences biological interaction. ► OH-PBDEs induce oxidative stress. ► Thyroid hormone gene regulation was disrupted following exposure. ► To our knowledge, this is the first whole organism study of OH-PBDE toxicity.« less

Structure and Dynamics of Water/Methanol Mixtures at Hydroxylated Silica Interfaces Relevant to Chromatography.

PubMed

Gupta, Prashant Kumar; Meuwly, Markus

2016-09-19

The spectroscopy and dynamics of water/methanol (MeOH) mixtures at hydroxylated silica surfaces is investigated from atomistic simulations. The particular focus is on how the structural dynamics of MeOH changes when comparing surface-bound and MeOH in the bulk. From analyzing the frequency frequency correlation functions it is found that the dynamics on the picosecond time scale differs by almost a factor of two. While the relaxation time is 2.0 ps for MeOH in the bulk solvent it is considerably slowed-down to 3.5 ps for surface-bound MeOH. Surface-adsorbed MeOH molecules reside there for several nanoseconds and their H-bonds are strongly oriented towards the surface-OH groups. These results are of particular relevance for chromatographic systems where the solvent may play a central role in their function. The present simulations suggest that surface-sensitive spectroscopic techniques should be useful in better characterizing such heterogeneous systems and provide detailed insight into solvent dynamics and structure relevant in chromatographic applications. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Mangiferin - a bioactive xanthonoid, not only from mango and not just antioxidant.

PubMed

Matkowski, Adam; Kuś, Piotr; Góralska, Edyta; Woźniak, Dorota

2013-03-01

Mangiferin is a plant natural polyphenol of C-glycosylxanthone structure and various pharmacological activities. It can be found in many plant species, among which the mango tree (Mangifera indica) is one of the primary sources. Mangiferin is also present in some medicinal herbs, influencing their therapeutic and preventive properties, and in honeybush (Cyclopia sp.), a popular South African herbal tea. Mangiferin dissolves well in water, so it can be easily extracted into infusions and decoctions. In the mangiferin molecule, four aromatic hydroxyl groups determine its strong antiradical and antioxidant properties. Mangiferin is also an efficient iron chelator, therefore preventing the generation of hydroxyl radical in Fenton-type reactions. Numerous published in vitro and in vivo pharmacological studies, demonstrated many other activities of mangiferin: analgesic, antidiabetic, antisclerotic, atimicrobial and antiviral, cardio-, hepato-, and neuroprotective, antiinflammatory, antiallergic, MAO inhibiting and memory improving, as well as radioprotective against X-ray, gamma, and UV radiation. Several studies indicated also its ability to inhibit cancerogenesis and cancer cells growth by apoptosis induction in vitro and in vivo. It is also used in cosmetics, due to antioxidant and UV-protecting properties.

Mechanisms of LiCoO2 Cathode Degradation by Reaction with HF and Protection by Thin Oxide Coatings.

PubMed

Tebbe, Jonathon L; Holder, Aaron M; Musgrave, Charles B

2015-11-04

Reactions of HF with uncoated and Al and Zn oxide-coated surfaces of LiCoO2 cathodes were studied using density functional theory. Cathode degradation caused by reaction of HF with the hydroxylated (101̅4) LiCoO2 surface is dominated by formation of H2O and a LiF precipitate via a barrierless reaction that is exothermic by 1.53 eV. We present a detailed mechanism where HF reacts at the alumina coating to create a partially fluorinated alumina surface rather than forming AlF3 and H2O and thus alumina films reduce cathode degradation by scavenging HF and avoiding H2O formation. In contrast, we find that HF etches monolayer zinc oxide coatings, which thus fail to prevent capacity fading. However, thicker zinc oxide films mitigate capacity loss by reacting with HF to form a partially fluorinated zinc oxide surface. Metal oxide coatings that react with HF to form hydroxyl groups over H2O, like the alumina monolayer, will significantly reduce cathode degradation.

Aminoacyl transfer from an adenylate anhydride to polyribonucleotides

NASA Technical Reports Server (NTRS)

Weber, A. L.; Lacey, J. C., Jr.

1975-01-01

Imidazole catalysis of phenylalanyl transfer from phenylalanine adenylate to hydroxyl groups of homopolyribonucleotides is studied as a possible chemical model of biochemical aminoacylation of transfer RNA (tRNA). The effect of pH on imidazole-catalyzed transfer of phenylalanyl residues to poly(U) and poly(A) double helix strands, the number of peptide linkages and their lability to base and neutral hydroxylamine, and the nature of adenylate condensation products are investigated. The chemical model entertained exhibits a constraint by not acylating the hydroxyl groups of polyribonucleotides in a double helix. The constraint is consistent with selective biochemical aminoacylation at the tRNA terminus. Interest in imidazole as a model of histidine residue in protoenzymes participating in prebiotic aminoacyl transfer to polyribonucleotides, and in rendering the tRNA a more efficient adaptor, is indicated.

Accelerated degradation of lignin by lignin peroxidase isozyme H8 (LiPH8) from Phanerochaete chrysosporium with engineered 4-O-methyltransferase from Clarkia breweri.

PubMed

Pham, Le Thanh Mai; Kim, Yong Hwan

2014-11-01

Free-hydroxyl phenolic units can decrease or even abort the catalytic activity of lignin peroxidase H8 during oxidation of veratryl alcohol and model lignin dimers, resulting in slow and inefficient lignin degradation. In this study we applied engineered 4-O-methyltransferase from Clarkia breweri to detoxify the inhibiting free-hydroxyl phenolic groups by converting them to methylated phenolic groups. The multistep, enzyme-catalyzed process that combines 4-O-methyltransferase and lignin peroxidase H8 suggested in this work can increase the efficiency of lignin-degradation. This study also suggests approaching the field of multi-enzyme in vitro systems to improve the understanding and development of plant biomass in biorefinery operations. Copyright © 2014 Elsevier Inc. All rights reserved.

Improved Stability of Proline-Derived Direct Thrombin Inhibitors through Hydroxyl to Heterocycle Replacement.

PubMed

Chobanian, Harry R; Pio, Barbara; Guo, Yan; Shen, Hong; Huffman, Mark A; Madeira, Maria; Salituro, Gino; Terebetski, Jenna L; Ormes, James; Jochnowitz, Nina; Hoos, Lizbeth; Zhou, Yuchen; Lewis, Dale; Hawes, Brian; Mitnaul, Lyndon; O'Neill, Kim; Ellsworth, Kenneth; Wang, Liangsu; Biftu, Tesfaye; Duffy, Joseph L

2015-05-14

Modification of the previously disclosed (S)-N-(2-(aminomethyl)-5-chlorobenzyl)-1-((R)-2-hydroxy-3,3-dimethylbutanoyl)pyrrolidine-2-carboxamide 2 by optimization of the P3 group afforded novel, low molecular weight thrombin inhibitors. Heterocycle replacement of the hydroxyl functional group helped maintain thrombin in vitro potency while improving the chemical stability and pharmacokinetic profile. These modifications led to the identification of compound 10, which showed excellent selectivity over related serine proteases as well as in vivo efficacy in the rat arteriovenous shunt. Compound 10 exhibited significantly improved chemical stability and pharmacokinetic properties over 2 and may be utilized as a structurally differentiated preclinical tool comparator to dabigatran etexilate (Pro-1) to interrogate the on- and off-target effects of oral direct thrombin inhibitors.

Rheological Properties of Graphene Oxide/Konjac Glucomannan Sol.

PubMed

Zhu, Wenkun; Duan, Tao; Hu, Zuowen

2018-05-01

We have demonstrated there is a significant intermolecular interaction between GO and KGM that results from hydrogen bonding and physical cross-linking by studying the rheological properties of a graphene oxide/konjac glucomannan (GO/KGM) solution. When the addition of GO was 5%, the storage modulus (G') and loss modulus (G″) were only improved by 0.25%. However, G' and G″ were improved by approximately 90% and 73.4%, respectively, when the GO content was increased to 7.5%. The moduli also displayed a relationship between the power function and concentration. Furthermore, the formation mechanism of GO/KGM was investigated by Raman, FT-IR, XPS and SEM. The results suggested that hydrogen bonding and physical crosslinking are generated from the abundant carboxy and hydroxyl groups of graphene oxide and the hydroxyl groups of konjac glucomannan.

The crystal structure of xanthine oxidoreductase during catalysis: Implications for reaction mechanism and enzyme inhibition

PubMed Central

Okamoto, Ken; Matsumoto, Koji; Hille, Russ; Eger, Bryan T.; Pai, Emil F.; Nishino, Takeshi

2004-01-01

Molybdenum is widely distributed in biology and is usually found as a mononuclear metal center in the active sites of many enzymes catalyzing oxygen atom transfer. The molybdenum hydroxylases are distinct from other biological systems catalyzing hydroxylation reactions in that the oxygen atom incorporated into the product is derived from water rather than molecular oxygen. Here, we present the crystal structure of the key intermediate in the hydroxylation reaction of xanthine oxidoreductase with a slow substrate, in which the carbon–oxygen bond of the product is formed, yet the product remains complexed to the molybdenum. This intermediate displays a stable broad charge–transfer band at ≈640 nm. The crystal structure of the complex indicates that the catalytically labile Mo—OH oxygen has formed a bond with a carbon atom of the substrate. In addition, the Mo⋕S group of the oxidized enzyme has become protonated to afford Mo—SH on reduction of the molybdenum center. In contrast to previous assignments, we find this last ligand at an equatorial position in the square-pyramidal metal coordination sphere, not the apical position. A water molecule usually seen in the active site of the enzyme is absent in the present structure, which probably accounts for the stability of this intermediate toward ligand displacement by hydroxide. PMID:15148401

Biological and nonbiological modifications of carbamates

PubMed Central

Knaak, James B.

1971-01-01

Methylcarbamate insecticides undergo hydrolysis, oxidation, dealkylation, and conjugation in animals, plants, and insects to form similar or identical products. Carbaryl is hydroxylated in biological systems to form hydroxy, dihydro-dihydroxy, and N-hydroxymethyl carbaryl and is hydrolysed to form 1-naphthol. The products are conjugated, stored, or excreted. Carbofuran is hydroxylated at the 3 position and propoxur at the 5 position to form hydroxylated derivatives. N-hydroxymethyl derivatives of these two carbamates may also be formed. Hydrolysis appears to be the major metabolic pathway of carbofuran in the animal. Aldicarb is oxidized to its sulfoxide and then hydrolysed to the oxime sulfoxide in animals and plants. Plants hydrolyse the oxime sulfoxide to form the corresponding aldehyde, which is an intermediate in the formation of 2-methyl-2-(methyl-sulfinyl)propanol. Methomyl, which is structurally similar to aldicarb, is metabolized in plants to acetonitrile, carbon dioxide, and methylamine. Bux and Meobal undergo hydrolysis and hydroxylation to form N-hydroxy methylcarbamates, as well as hydroxybutylphenyl and hydroxymethylphenyl methylcarbamates. Zectran, which contains a dimethylamino group, is converted to the methylamino, amino, and methylformamido derivatives by insects and plants. In soil and water, methylcarbamate insecticides are hydrolysed to their respective phenols or oximes. PMID:4999481

Reaction mechanisms of DNT with hydroxyl radicals for advanced oxidation processes-a DFT study.

PubMed

Zhou, Yang; Yang, Zhilin; Yang, Hong; Zhang, Chaoyang; Liu, Xiaoqiang

2017-04-01

In advanced oxidation processes (AOPs), the detailed degradation mechanisms of a typical explosive of 2,4-dinitrotoluene (DNT) can be investigated by the density function theory (DFT) method at the SMD/M062X/6-311+G(d) level. Several possible degradation routes for DNT were explored in the current study. The results show that, for oxidation of the methyl group, the dominant degradation mechanism of DNT by hydroxyl radicals (•OH) is a series of sequential H-abstraction reactions, and the intermediates obtained are in good agreement with experimental findings. The highest activation energy barrier is less than 20 kcal mol -1 . Other routes are dominated by an addition-elimination mechanism, which is also found in 2,4,6-trinitrotoluene, although the experiment did not find the corresponding products. In addition, we also eliminate several impossible mechanisms, such as dehydration, HNO 3 elimination, the simultaneous addition of two •OH radials, and so on. The information gained about these degradation pathways is helpful in elucidating the detailed reaction mechanism between nitroaromatic explosives and hydroxyl radicals for AOPs. Graphical Abstract The degradation mechanism of an important explosive, 2,6-dinitrotoluene (DNT), by the hydroxyl radical for advanced oxidation progresses.

Synthesis and antioxidant, anti-inflammatory and gastroprotector activities of anethole and related compounds.

PubMed

Freire, Rosemayre S; Morais, Selene M; Catunda-Junior, Francisco Eduardo A; Pinheiro, Diana C S N

2005-07-01

Some derivatives of trans-anethole [1-methoxy-4-(1-propenyl)-benzene] (1) were synthesized, by introducing hydroxyl groups in the double bond of the propenyl moiety. Two types of reactions were performed: (i) oxymercuration/demercuration that formed two products, the mono-hydroxyl derivative, 1-hydroxy-1-(4-methoxyphenyl)-propane (2) and in lesser extent the dihydroxyl derivative, 1,2-dihydroxy-1-(4-methoxyphenyl)-propane (3) and (ii) epoxidation with m-chloroperbenzoic acid that also led to the formation of two products, the dihydroxyl derivative (3) and the correspondent m-chloro-benzoic acid mono-ester, 1-hydroxy-1(4-methoxyphenyl)-2-m-chlorobenzoyl-propane (4). The structures of these compounds were confirmed mainly by mass, IR, 1H and 13C NMR spectral data. The activity of anethole and hydroxylated derivatives was evaluated using antioxidant, anti-inflammatory and gastroprotector tests. Compounds (2) and (3) were more active antioxidant agents than (1) and (4). In the anti-inflammatory assay, anethole showed lower activity than hydroxylated derivatives. Anethole and in lesser extent its derivatives 2 and 4 showed significant gastroprotector activity. All tested compounds do not alter significantly the total number of white blood cells.

Three Cd(II) MOFs with Different Functional Groups: Selective CO2 Capture and Metal Ions Detection.

PubMed

Wang, Zhong-Jie; Han, Li-Juan; Gao, Xiang-Jing; Zheng, He-Gen

2018-05-07

Three Cd(II) iso-frameworks {[Cd(BIPA)(IPA)]·DMF} n (1), {[Cd(BIPA)(HIPA)]·DMF} n (2), and {[Cd(BIPA)(NIPA)]·2H 2 O} n (3) were synthesized from the self-assembly of the BIPA ligand (BIPA = bis(4-(1 H-imidazol-1-yl)phenyl)amine) and different carboxylic ligands (H 2 IPA = isophthalic acid, H 2 HIPA = 5-hydroxyisophthalic acid, H 2 NIPA = 5-nitroisophthalic acid) with Cd(II), which have amino groups, amino and phenolic hydroxyl groups, and amino and nitro groups, respectively. Both 1 and 2 exhibit CO 2 uptakes of more than 20 wt %, indicating that amino and phenolic hydroxyl functionalized groups are beneficial to CO 2 adsorption. Their applications and mechanisms in detecting metal ions were researched. The results exhibit that 1 and 2 are dual-responsive photoluminescent sensors for Hg 2+ and Pb 2+ ions with low detection concentration and high quenching constant. Besides, like most MOFs, 3 can detect a trace quantity of Fe 3+ and Cu 2+ .

Developing cellulosic waste products as platform chemicals: protecting group chemistry of α-glucoisosaccharinic acid.

PubMed

Almond, Michael; Suleiman, Mustapha G; Hawkins, Matthew; Winder, Daniel; Robshaw, Thomas; Waddoups, Megan; Humphreys, Paul N; Laws, Andrew P

2018-01-02

Alpha and beta-glucoisosaccharinic acids ((2S,4S)-2,4,5-trihydroxy-2-(hydroxymethyl)pentanoic acid and (2R,4S)-2,4,5-trihydroxy-2-(hydroxymethyl)pentanoic acid) which are produced when cellulosic materials are treated with aqueous alkali are potentially valuable platform chemicals. Their highly functionalised carbon skeleton, with fixed chirality at C-2 and C-4, makes them ideal starting materials for use in synthesis. In order to assess the potential of these saccharinic acids as platform chemicals we have explored the protecting group chemistry of the lactone form of alpha-glucoisosaccharinic acid (α-GISAL). We report here the use of single and multiple step reaction pathways leading to the regioselective protection of the three different hydroxyl groups of α-GISAL. We report strategies for protecting the three different hydroxyl groups individually or in pairs. We also report the synthesis of a range of tri-O-protected α-GISAL derivatives where a number of the products contain orthogonal protecting groups. Copyright © 2017 Elsevier Ltd. All rights reserved.

Nonfouling Characteristics of Dextran-Containing Surfaces

PubMed Central

Martwiset, Surangkhana; Koh, Anna E.; Chen, Wei

2008-01-01

Hydroxyl groups in dextrans have been selectively oxidized to aldehyde groups by sodium periodate in a controlled fashion with percentage of conversion ranging from 6% to 100%. Dextrans (10 k, 70 k, 148 k, 500 k, and 2 000 kDa) and oxidized 10 k dextrans have been successfully grafted to functionalized silicon surfaces. The effect of molecular weight on protein adsorption is not nearly as striking as that of the extent of oxidation. When ∼ 25% of the hydroxyl groups have been converted to aldehyde groups, there is negligible protein adsorption on surfaces containing the oxidized polysaccharides. Conformations of grafted polymers depend strongly on their chemical structures, i.e. the relative amounts of –OH and –CHO groups. That the dependence of the chain conformation as well as the protein resistance on the balance of the hydrogen bond donors (-OH) and the acceptors (-OH and –CHO) implies the importance of chemical structure of surface molecules, specifically the interactions between surface and surrounding water molecules on protein adsorption. Oxidized dextrans are potential poly(ethylene glycol)-alternatives for nonfouling applications. PMID:16952261

Physical-Mechanical Properties and Micromorphology of Calcium Cements Exposed to Polyacrylic and Phosphoric Acids.

PubMed

de Souza, Gustavo Fernandes; Arrais, Ana Beatriz; Aragão, Cícero Flávio Soares; Ferreira, Isana Alvares; Borges, Boniek Castillo Dutra

2018-01-01

To evaluate if physical and mechanical properties of self-curing calcium hydroxide cements were affected by contact with polyacrylic and phosphoric acids. Resin-containing (Life (LF)) and resin-free (Hydro C (HyC)) materials were subjected to polyacrylic acid conditioning and rinsing (POL); phosphoric acid conditioning and rinsing (PHO); rinsing only; and no treatment ( n = 10). Water sorption/solubility, release of hydroxyl ions (pH), roughness (Ra), and impact resistance were evaluated. Additional samples ( n = 1) were prepared for scanning electron microscopy (SEM) analysis of the surface morphology. Data were analyzed by two-way ANOVA and Tukey post hoc test ( P < 0.05). Water sorption was significantly higher for LF when in contact with PHO and lower for POL ( P < 0.05). The mean solubility was higher with POL for both cements ( P < 0.05). PHO increased the mean surface roughness for HyC ( P < 0.01); a significant decrease was noted for LF after contact with both acids ( P < 0.01). PHO promoted lower release of hydroxyl ions on both cements ( P < 0.05). For LF, rinsing, PHO, and POL presented similar morphology, differing from the control group. For HyC, PHO and POL presented similar morphology, differing from the control group. PHO had a negative effect on the physical properties of the cements tested, except for the solubility test. POL affected roughness and solubility of HyC cement. Clinical procedures that require polyacrylic and phosphoric acid conditioning must be done carefully on self-curing calcium hydroxide cements in order to avoid negative impact on their properties.

Cell surface acid-base properties of Escherichia coli and Bacillus brevis and variation as a function of growth phase, nitrogen source and C:N ratio.

PubMed

Hong, Yongsuk; Brown, Derick G

2006-07-01

Potentiometric titration has been conducted to systematically examine the acid-base properties of the cell surfaces of Escherichia coli K-12 and Bacillus brevis as a function of growth phase, nitrogen source (ammonium or nitrate), and carbon to nitrogen (C:N) ratio of the growth substrate. The two bacterial species revealed four distinct proton binding sites, with pK(a) values in the range of 3.08-4.05 (pK(1)), 4.62-5.57 (pK(2)), 6.47-7.30 (pK(3)), and 9.68-10.89 (pK(4)) corresponding to phosphoric/carboxylic, carboxylic, phosphoric, and hydroxyl/amine groups, respectively. Two general observations in the data are that for B. brevis the first site concentration (N(1)), corresponding to phosphoric/carboxylic groups (pK(1)), varied as a function of nitrogen source, while for E. coli the fourth site concentration (N(4)), corresponding to hydroxyl/amine groups (pK(4)), varied as a function of C:N ratio. Correspondingly, it was found that N(1) was the highest of the four site concentrations for B. brevis and N(4) was the highest for E. coli. The concentrations of the remaining sites showed little variation. Finally, comparison between the titration data and a number of cell surface compositional studies in the literature indicates one distinct difference between the two bacteria is that pK(4) of the Gram-negative E. coli can be attributed to hydroxyl groups while that of the Gram-positive B. brevis can be attributed to amine groups.

Rhemium-186-monoaminemonoamidedithiol-conjugated bisphosphonate derivatives for bone pain palliation.

PubMed

Ogawa, Kazuma; Mukai, Takahiro; Arano, Yasushi; Otaka, Akira; Ueda, Masashi; Uehara, Tomoya; Magata, Yasuhiro; Hashimoto, Kazuyuki; Saji, Hideo

2006-05-01

To develop a radiopharmaceutical for the palliation of painful bone metastases based on the concept of bifunctional radiopharmaceuticals, we synthesized a bisphosphonate derivative labeled with rhenium-186 (186Re) that contains a hydroxyl group at the central carbon of its bisphosphonate structure, we attached a stable 186Re-MAMA chelate to the amino group of a 4-amino butylidene-bisphosphonate derivative [N-[2-[[4-[(4-hydroxy-4,4-diphosphonobutyl)amino]-4-oxobutyl]-2-thioethylamino]acetyl]-2-aminoethanethiolate] oxorhenium (V) (186Re-MAMA-HBP) and we investigated the effect of a hydroxyl group at the central carbon of its bisphosphonate structure on affinity for hydroxyapatite and on biodistribution by conducting a comparative study with [N-[2-[[3-(3,3-diphosphonopropylcarbamoyl)propyl]-2-thioethylamino]acetyl]-2-aminoethanethiolate] oxorhenium (V) (186Re-MAMA-BP). The precursor of 186Re-MAMA-HBP, trityl (Tr)-MAMA-HBP, was obtained by coupling a Tr-MAMA derivative to 4-amino-1-hydroxybutylidene-1,1-bisphosphonate. 186Re-MAMA-HBP was prepared by a reaction with 186ReO(4-) and SnCl2 in citrate buffer after the deprotection of the Tr groups of Tr-MAMA-HBP. After reversed-phase high-performance liquid chromatography, 186Re-MAMA-HBP had a radiochemical purity of over 95%. Compared with 186Re-MAMA-BP, 186Re-MAMA-HBP showed a greater affinity for hydroxyapatite beads in vitro and accumulated a significantly higher level in the femur in vivo. Thus, the introduction of a hydroxyl group into 186Re complex-conjugated bisphosphonates would be effective in enhancing accumulation in bones. These findings provide useful information on the design of bone-seeking therapeutic radiopharmaceuticals.

Microbial Baeyer-Villiger oxidation of 5α-steroids using Beauveria bassiana. A stereochemical requirement for the 11α-hydroxylation and the lactonization pathway.

PubMed

Świzdor, Alina; Panek, Anna; Milecka-Tronina, Natalia

2014-04-01

Beauveria bassiana KCH 1065, as was recently demonstrated, is unusual amongst fungal biocatalysts in that it converts C19 3-oxo-4-ene and 3β-hydroxy-5-ene as well as 3β-hydroxy-5α-saturated steroids to 11α-hydroxy ring-D lactones. The Baeyer-Villiger monooxygenase (BVMO) of this strain is distinguished from other enzymes catalyzing BVO of steroidal ketones by the fact that it oxidizes solely substrates with 11α-hydroxyl group. The current study using a series of 5α-saturated steroids (androsterone, 3α-androstanediol and androstanedione) has highlighted that a small change of the steroid structure can result in significant differences of the metabolic fate. It was found that the 3α-stereochemistry of hydroxyl group restricted "normal" binding orientation of the substrate within 11α-hydroxylase and, as a result, androsterone and 3α-androstanediol were converted into a mixture of 7β-, 11α- and 7α-hydroxy derivatives. Hydroxylation of androstanedione occurred only at the 11α-position, indicating that the 3-oxo group limits the alternative binding orientation of the substrate within the hydroxylase. Only androstanedione and 3α-androstanediol were metabolized to hydroxylactones. The study uniquely demonstrated preference for oxidation of equatorial (11α-, 7β-) hydroxyketones by BVMO from B. bassiana. The time course experiments suggested that the activity of 17β-HSD is a factor determining the amount of produced ring-D lactones. The obtained 11α-hydroxylactones underwent further transformations (oxy-red reactions) at C-3. During conversion of androstanedione, a minor dehydrogenation pathway was observed with generation of 11α,17β-dihydroxy-5α-androst-1-en-3-one. The introduction of C1C2 double bond has been recorded in B. bassiana for the first time. Copyright © 2014 Elsevier Inc. All rights reserved.

Probing surface sites of TiO2: reactions with [HRe(CO)5] and [CH3Re(CO)5].

PubMed

Lobo-Lapidus, Rodrigo J; Gates, Bruce C

2010-10-04

Two carbonyl complexes of rhenium, [HRe(CO)(5)] and [CH(3)Re(CO)(5)], were used to probe surface sites of TiO(2) (anatase). These complexes were adsorbed from the gas phase onto anatase powder that had been treated in flowing O(2) or under vacuum to vary the density of surface OH sites. Infrared (IR) spectra demonstrate the variation in the number of sites, including Ti(+3)-OH and Ti(+4)-OH. IR and extended X-ray absorption fine structure (EXAFS) spectra show that chemisorption of the rhenium complexes led to their decarbonylation, with formation of surface-bound rhenium tricarbonyls, when [HRe(CO)(5)] was adsorbed, or rhenium tetracarbonyls, when [CH(3)Re(CO)(5)] was adsorbed. These reactions were accompanied by the formation of water and surface carbonates and removal of terminal hydroxyl groups associated with Ti(+3) and Ti(+4) ions on the anatase. Data characterizing the samples after adsorption of [HRe(CO)(5)] or [CH(3)Re(CO)(5)] determined a ranking of the reactivity of the surface OH sites, with the Ti(+3)-OH groups being the more reactive towards the rhenium complexes but the less likely to be dehydroxylated. The two rhenium pentacarbonyl probes provided complementary information, suggesting that the carbonate species originate from carbonyl ligands initially bonded to the rhenium and from hydroxyl groups of the titania surface, with the reaction leading to the formation of water and bridging hydroxyl groups on the titania. The results illustrate the value of using a family of organometallic complexes as probes of oxide surface sites.

Enhanced in vitro biological activity generated by surface characteristics of anodically oxidized titanium--the contribution of the oxidation effect.

PubMed

Wurihan; Yamada, A; Suzuki, D; Shibata, Y; Kamijo, R; Miyazaki, T

2015-05-20

Anodically oxidized titanium surfaces, prepared by spark discharge, have micro-submicron surface topography and nano-scale surface chemistry, such as hydrophilic functional groups or hydroxyl radicals in parallel. The complexity of the surface characteristics makes it difficult to draw a clear conclusion as to which surface characteristic, of anodically oxidized titanium, is critical in each biological event. This study examined the in vitro biological changes, induced by various surface characteristics of anodically oxidized titanium with, or without, release of hydroxyl radicals onto the surface. Anodically oxidized titanium enhanced the expression of genes associated with differentiating osteoblasts and increased the degree of matrix mineralization by these cells in vitro. The phenotypes of cells on the anodically oxidized titanium were the same with, or without, release of hydroxyl radicals. However, the nanomechanical properties of this in vitro mineralized tissue were significantly enhanced on surfaces, with release of hydroxyl radicals by oxidation effects. In addition, the mineralized tissue, produced in the presence of bone morphogenetic protein-2 on bare titanium, had significantly weaker nanomechanical properties, despite there being higher osteogenic gene expression levels. We show that enhanced osteogenic cell differentiation on modified titanium is not a sufficient indicator of enhanced in vitro mineralization. This is based on the inferior mechanical properties of mineralized tissues, without either being cultured on a titanium surface with release of hydroxyl radicals, or being supplemented with lysyl oxidase family members.

Synthesis of Transesterified Palm Olein-Based Polyol and Rigid Polyurethanes from this Polyol.

PubMed

Arniza, Mohd Zan; Hoong, Seng Soi; Idris, Zainab; Yeong, Shoot Kian; Hassan, Hazimah Abu; Din, Ahmad Kushairi; Choo, Yuen May

Transesterification of palm olein with glycerol can increase the functionality by introducing additional hydroxyl groups to the triglyceride structure, an advantage compared to using palm olein directly as feedstock for producing palm-based polyol. The objective of this study was to synthesize transesterified palm olein-based polyol via a three-step reaction: (1) transesterification of palm olein, (2) epoxidation and (3) epoxide ring opening. Transesterification of palm olein yielded approximately 78 % monoglyceride and has an hydroxyl value of approximately 164 mg KOH g -1 . The effect of formic acid and hydrogen peroxide concentrations on the epoxidation reaction was studied. The relationships between epoxide ring-opening reaction time and residual oxirane oxygen content and hydroxyl value were monitored. The synthesized transesterified palm olein-based polyol has hydroxyl value between 300 and 330 mg KOH g -1 and average molecular weight between 1,000 and 1,100 Da. On the basis of the hydroxyl value and average molecular weight of the polyol, the transesterified palm olein-based polyol is suitable for producing rigid polyurethane foam, which can be designed to exhibit desirable properties. Rigid polyurethane foams were synthesized by substituting a portion of petroleum-based polyol with the transesterified palm olein-based polyol. It was observed that by increasing the amount of transesterified palm olein-based polyol, the core density and compressive strength were reduced but at the same time the insulation properties of the rigid polyurethane foam were improved.

Method of making carbon nanotube composite materials

DOEpatents

O'Bryan, Gregory; Skinner, Jack L; Vance, Andrew; Yang, Elaine Lai; Zifer, Thomas

2014-05-20

The present invention is a method of making a composite polymeric material by dissolving a vinyl thermoplastic polymer, un-functionalized carbon nanotubes and hydroxylated carbon nanotubes and optionally additives in a solvent to make a solution and removing at least a portion of the solvent after casting onto a substrate to make thin films. The material has enhanced conductivity properties due to the blending of the un-functionalized and hydroxylated carbon nanotubes.

A facile synthetic route to poly(p-phenylene terephthalamide) with dual functional groups.

PubMed

Du, Shuming; Wang, Wenbin; Yan, Yan; Zhang, Jie; Tian, Ming; Zhang, Liqun; Wan, Xinhua

2014-09-07

Claisen rearrangement reaction was employed for the first time to obtain a novel PPTA bearing reactive allyl and hydroxyl groups which may act as a sizing agent of Kevlar fibers to improve the interface structure and interfacial adhesion of rubber or epoxy based composites.

Dihydroflavonol 4-reductase genes encode enzymes with contrasting substrate specificity and show divergent gene expression profiles in Fragaria species.

PubMed

Miosic, Silvija; Thill, Jana; Milosevic, Malvina; Gosch, Christian; Pober, Sabrina; Molitor, Christian; Ejaz, Shaghef; Rompel, Annette; Stich, Karl; Halbwirth, Heidi

2014-01-01

During fruit ripening, strawberries show distinct changes in the flavonoid classes that accumulate, switching from the formation of flavan 3-ols and flavonols in unripe fruits to the accumulation of anthocyanins in the ripe fruits. In the common garden strawberry (Fragaria×ananassa) this is accompanied by a distinct switch in the pattern of hydroxylation demonstrated by the almost exclusive accumulation of pelargonidin based pigments. In Fragaria vesca the proportion of anthocyanins showing one (pelargonidin) and two (cyanidin) hydroxyl groups within the B-ring is almost equal. We isolated two dihydroflavonol 4-reductase (DFR) cDNA clones from strawberry fruits, which show 82% sequence similarity. The encoded enzymes revealed a high variability in substrate specificity. One enzyme variant did not accept DHK (with one hydroxyl group present in the B-ring), whereas the other strongly preferred DHK as a substrate. This appears to be an uncharacterized DFR variant with novel substrate specificity. Both DFRs were expressed in the receptacle and the achenes of both Fragaria species and the DFR2 expression profile showed a pronounced dependence on fruit development, whereas DFR1 expression remained relatively stable. There were, however, significant differences in their relative rates of expression. The DFR1/DFR2 expression ratio was much higher in the Fragaria×ananassa and enzyme preparations from F.×ananassa receptacles showed higher capability to convert DHK than preparations from F. vesca. Anthocyanin concentrations in the F.×ananassa cultivar were more than twofold higher and the cyanidin:pelargonidin ratio was only 0.05 compared to 0.51 in the F. vesca cultivar. The differences in the fruit colour of the two Fragaria species can be explained by the higher expression of DFR1 in F.×ananassa as compared to F. vesca, a higher enzyme efficiency (Kcat/Km values) of DFR1 combined with the loss of F3'H activity late in fruit development of F.×ananassa.

Dihydroflavonol 4-Reductase Genes Encode Enzymes with Contrasting Substrate Specificity and Show Divergent Gene Expression Profiles in Fragaria Species

PubMed Central

Miosic, Silvija; Thill, Jana; Milosevic, Malvina; Gosch, Christian; Pober, Sabrina; Molitor, Christian; Ejaz, Shaghef; Rompel, Annette; Stich, Karl; Halbwirth, Heidi

2014-01-01

During fruit ripening, strawberries show distinct changes in the flavonoid classes that accumulate, switching from the formation of flavan 3-ols and flavonols in unripe fruits to the accumulation of anthocyanins in the ripe fruits. In the common garden strawberry (Fragaria×ananassa) this is accompanied by a distinct switch in the pattern of hydroxylation demonstrated by the almost exclusive accumulation of pelargonidin based pigments. In Fragaria vesca the proportion of anthocyanins showing one (pelargonidin) and two (cyanidin) hydroxyl groups within the B-ring is almost equal. We isolated two dihydroflavonol 4-reductase (DFR) cDNA clones from strawberry fruits, which show 82% sequence similarity. The encoded enzymes revealed a high variability in substrate specificity. One enzyme variant did not accept DHK (with one hydroxyl group present in the B-ring), whereas the other strongly preferred DHK as a substrate. This appears to be an uncharacterized DFR variant with novel substrate specificity. Both DFRs were expressed in the receptacle and the achenes of both Fragaria species and the DFR2 expression profile showed a pronounced dependence on fruit development, whereas DFR1 expression remained relatively stable. There were, however, significant differences in their relative rates of expression. The DFR1/DFR2 expression ratio was much higher in the Fragaria×ananassa and enzyme preparations from F.×ananassa receptacles showed higher capability to convert DHK than preparations from F. vesca. Anthocyanin concentrations in the F.×ananassa cultivar were more than twofold higher and the cyanidin:pelargonidin ratio was only 0.05 compared to 0.51 in the F. vesca cultivar. The differences in the fruit colour of the two Fragaria species can be explained by the higher expression of DFR1 in F.×ananassa as compared to F. vesca, a higher enzyme efficiency (K cat/K m values) of DFR1 combined with the loss of F3’H activity late in fruit development of F.×ananassa. PMID:25393679

Flexible composite film for printed circuit board

NASA Technical Reports Server (NTRS)

Yabe, K.; Asakura, M.; Tanaka, H.; Soda, A.

1982-01-01

A flexible printed circuit for a printed circuit board in which layers of reaction product composed of a combination of phenoxy resin - polyisocyanate - brominated epoxy resin, and in which the equivalent ratio of those functional groups is hydroxyl group: isocyanate group: epoxy group - 1 : 0.2 to 2 : 0.5 to 3 are laminated on at least one side of saturated polyester film is discussed.

Proline Hydroxylation in Cell Wall Proteins: Is It Yet Possible to Define Rules?

PubMed

Duruflé, Harold; Hervé, Vincent; Balliau, Thierry; Zivy, Michel; Dunand, Christophe; Jamet, Elisabeth

2017-01-01

Cell wall proteins (CWPs) play critical and dynamic roles in plant cell walls by contributing to developmental processes and response to environmental cues. Since the CWPs go through the secretion pathway, most of them undergo post-translational modifications (PTMs) which can modify their biological activity. Glycosylation is one of the major PTMs of CWPs and refers to N -glycosylation, O -glycosylation and glypiation. Each of these PTMs occurs in different amino acid contexts which are not all well defined. This article deals with the hydroxylation of Pro residues which is a prerequisite for O -glycosylation of CWPs on hydroxyproline (Hyp) residues. The location of Hyp residues is well described in several structural CWPs, but yet rarely described in other CWPs. In this article, it is studied in detail in five Arabidopsis thaliana proteins using mass spectrometry data: one of them (At4g38770, AtPRP4) is a structural CWP containing 32.5% of Pro residues arranged in typical motifs, the others are either rich (27-28%, At1g31580 and At2g10940) or poor (6-8%, At1g09750 and At3g08030) in Pro residues. The known rules of Pro hydroxylation allowed a good prediction of Hyp location in AtPRP4. However, they could not be applied to the other proteins whatever their Pro content. In addition, variability of the Pro hydroxylation patterns was observed within some amino acid motifs in all the proteins and new patterns of Pro hydroxylation are described. Altogether, this work shows that Hyp residues are present in more protein families than initially described, and that Pro hydroxylation patterns could be different in each of them. This work paves the way for completing the existing Pro hydroxylation code.

Enthalpy-Entropy Compensation in the Binding of Modulators at Ionotropic Glutamate Receptor GluA2.

PubMed

Krintel, Christian; Francotte, Pierre; Pickering, Darryl S; Juknaitė, Lina; Pøhlsgaard, Jacob; Olsen, Lars; Frydenvang, Karla; Goffin, Eric; Pirotte, Bernard; Kastrup, Jette S

2016-06-07

The 1,2,4-benzothiadiazine 1,1-dioxide type of positive allosteric modulators of the ionotropic glutamate receptor A2 (GluA2) are promising lead compounds for the treatment of cognitive disorders, e.g., Alzheimer's disease. The modulators bind in a cleft formed by the interface of two neighboring ligand binding domains and act by stabilizing the agonist-bound open-channel conformation. The driving forces behind the binding of these modulators can be significantly altered with only minor substitutions to the parent molecules. In this study, we show that changing the 7-fluorine substituent of modulators BPAM97 (2) and BPAM344 (3) into a hydroxyl group (BPAM557 (4) and BPAM521 (5), respectively), leads to a more favorable binding enthalpy (ΔH, kcal/mol) from -4.9 (2) and -7.5 (3) to -6.2 (4) and -14.5 (5), but also a less favorable binding entropy (-TΔS, kcal/mol) from -2.3 (2) and -1.3 (3) to -0.5 (4) and 4.8 (5). Thus, the dissociation constants (Kd, μM) of 4 (11.2) and 5 (0.16) are similar to those of 2 (5.6) and 3 (0.35). Functionally, 4 and 5 potentiated responses of 10 μM L-glutamate at homomeric rat GluA2(Q)i receptors with EC50 values of 67.3 and 2.45 μM, respectively. The binding mode of 5 was examined with x-ray crystallography, showing that the only change compared to that of earlier compounds was the orientation of Ser-497 pointing toward the hydroxyl group of 5. The favorable enthalpy can be explained by the formation of a hydrogen bond from the side-chain hydroxyl group of Ser-497 to the hydroxyl group of 5, whereas the unfavorable entropy might be due to desolvation effects combined with a conformational restriction of Ser-497 and 5. In summary, this study shows a remarkable example of enthalpy-entropy compensation in drug development accompanied with a likely explanation of the underlying structural mechanism. Copyright © 2016 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Alleviation effect of arbutin on oxidative stress generated through tyrosinase reaction with l-tyrosine and l-DOPA

PubMed Central

2014-01-01

Background Hydroxyl radical that has the highest reactivity among reactive oxygen species (ROS) is generated through l-tyrosine-tyrosinase reaction. Thus, the melanogenesis might induce oxidative stress in the skin. Arbutin (p-hydroxyphenyl-β-d-glucopyranoside), a well-known tyrosinase inhibitor has been widely used for the purpose of skin whitening. The aim of the present study was to examine if arbutin could suppress the hydroxyl radical generation via tyrosinase reaction with its substrates, l-tyrosine and l-DOPA. Results The hydroxyl radical, which was determined by an electron spin resonance-spin trapping technique, was generated by the addition of not only l-tyrosine but l-DOPA to tyrosinase in a concentration dependent manner. Arbutin could inhibit the hydroxyl radical generation in the both reactions. Conclusion It is presumed that arbutin could alleviate oxidative stress derived from the melanogenic pathway in the skin in addition to its function as a whitening agent in cosmetics. PMID:25297374

IR study of dickite-formamide intercalate, Al 2Si 2O 5(OH) 4-H 2NCOH

NASA Astrophysics Data System (ADS)

Zamama, M.; Knidiri, Mohamed

2000-05-01

Direct intercalation of formamide (FAM) in dickite occurs spontaneously when samples are treated by ultrason. The X-ray diffraction patterns show that this intercalation increases the d 001 spacing from 7.19 to 10.77 Å. It is concluded from infrared studies that hydrogen bonds are formed between CO groups of formamide and inner surface hydroxyls of dickite, indicated by the shift of the hydroxyl bands from 3708, 3654 cm -1 and 3622 for natural dickite to 3575, 3520, 3450 and 3612 cm -1 for FAM-intercalated dickite.

IR study of dickite-formamide intercalate, Al2Si2O5(OH)4-H2NCOH.

PubMed

Zamama, M; Knidiri, M

2000-05-01

Direct intercalation of formamide (FAM) in dickite occurs spontaneously when samples are treated by ultrason. The X-ray diffraction patterns show that this intercalation increases the d001 spacing from 7.19 to 10.77 A. It is concluded from infrared studies that hydrogen bonds are formed between C=O groups of formamide and inner surface hydroxyls of dickite, indicated by the shift of the hydroxyl bands from 3708, 3654 cm(-1) and 3622 for natural dickite to 3575, 3520, 3450 and 3612 cm(-1) for FAM-intercalated dickite.

Ionothermal synthesis, crystal structure, and magnetic study of Co2PO4OH isostructural with caminite.

PubMed

Wang, Guangmei; Valldor, Martin; Spielberg, Eike T; Mudring, Anja-Verena

2014-03-17

A new framework cobalt(II) hydroxyl phosphate, Co2PO4OH, was prepared by ionothermal synthesis using 1-butyl-4-methyl-pyridinium hexafluorophosphate as the ionic liquid. As the formation of Co2PO4F competes in the synthesis, the synthesis conditions have to be judiciously chosen to obtain well-crystallized, single phase Co2PO4OH. Single-crystal X-ray diffraction analyses reveal Co2PO4OH crystallizes with space group I41/amd (a = b = 5.2713(7) Å, c = 12.907(3) Å, V = 358.63(10) Å(3), and Z = 4). Astonishingly, it does not crystallize isotypically with Co2PO4F but rather isotypically with the hydroxyl minerals caminite Mg1.33[SO4(OH)0.66(H2O)0.33] and lipscombite Fe(2–y)PO4(OH) (0 ≤ y ≤ 2/3). Phosphate tetrahedra groups interconnect four rod-packed face-sharing ∞(1){CoO(6/2)} octahedra chains to form a three-dimensional framework structure. The compound Co2PO4OH was further characterized by powder X-ray diffraction, Fourier transform–infrared, and ultraviolet–visible spectroscopy, confirming the discussed structure. The magnetic measurement reveals that Co2PO4OH undergoes a magnetic transition and presents at low temperatures a canted antiferromagnetic spin order in the ground state.

Side-chain hydroxylation in the metabolism of 8-aminoquinoline antiparasitic agents.

PubMed

Idowu, O R; Peggins, J O; Brewer, T G

1995-01-01

Primaquine, 8-(4-amino-1-methylbutylamino)-6-methoxyquinoline, is an antimalarial 8-aminoquinoline derivative. Although it has been in use since 1952, its metabolism has not been clearly defined. This is due to the instability of the expected aminophenol metabolites and their amphoteric nature, which makes their isolation difficult. Recent studies on the metabolism of WR 238605, a new primaquine analog, has shown that these problems may be solved by extracting the metabolites in the presence of ethyl chloroformate. Subsequent identification of the ethoxycarbonyl derivatives of the metabolites has made it possible to define the in vitro metabolism of primaquine. The primary metabolic pathways of primaquine involved hydroxylation of the phenyl ring of the quinoline nucleus and C-hydroxylation of the 3'-position of the 8-aminoalkylamino side chain. Ring-hydroxylation of primaquine gives rise to 5-hydroxyprimaquine, which on demethylation produces 5-hydroxy-6-demethylprimaquine. Side-chain hydroxylation of primaquine gives rise to 3'-hydroxyprimaquine, which also undergoes O-demethylation to 3'-hydroxy-6-demethylprimaquine. 6-Demethylprimaquine, a putative metabolite of primaquine, also underwent metabolism involving 3'-hydroxylation of the side chain. WR 6026, 8-(6-diethylaminohexylamino)-6-methoxy-4-methylquinoline, is an antileishmanial 8-aminoquinoline derivative. The in vitro metabolism of WR 6026 also results in the formation of side chain-oxygenated metabolites. The present results, together with previous observations on the metabolism of WR 238605 and closely related primaquine analog, suggest that side-chain oxygenation is an important metabolic pathway of antiparasitic 8-aminoquinoline compounds in general.

Impact of 2′-hydroxyl sampling on the conformational properties of RNA: Update of the CHARMM all-atom additive force field for RNA

PubMed Central

Denning, Elizabeth J.; Priyakumar, U. Deva; Nilsson, Lennart; MacKerell, Alexander D.

2011-01-01

Here, we present an update of the CHARMM27 all-atom additive force field for nucleic acids that improves the treatment of RNA molecules. The original CHARMM27 force field parameters exhibit enhanced Watson-Crick (WC) base pair opening which is not consistent with experiment while analysis of MD simulations show the 2′-hydroxyl moiety to almost exclusively sample the O3′ orientation. Quantum mechanical studies of RNA related model compounds indicate the energy minimum associated with the O3′ orientation to be too favorable, consistent with the MD results. Optimization of the dihedral parameters dictating the energy of the 2′-hydroxyl proton targeting the QM data yielded several parameter sets, which sample both the base and O3′ orientations of the 2′-hydroxyl to varying degrees. Selection of the final dihedral parameters was based on reproduction of hydration behavior as related to a survey of crystallographic data and better agreement with experimental NMR J-coupling values. Application of the model, designated CHARMM36, to a collection of canonical and non-canonical RNA molecules reveals overall improved agreement with a range of experimental observables as compared to CHARMM27. The results also indicate the sensitivity of the conformational heterogeneity of RNA to the orientation of the 2′-hydroxyl moiety and support a model whereby the 2′-hydroxyl can enhance the probability of conformational transitions in RNA. PMID:21469161

Effect of Hydroxyl Concentration on Chemical Sensitivity of Polyvinyl Alcohol/Carbon-Black Composite Chemiresistors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hughes, Robert C.; Patel, Sanjay V.; Yelton, W. Graham

1999-05-19

The sensitivity and selectivity of polyvinyl alcohol (PVA) / carbon black composite films have been found to vary depending upon the hydroxylation percentage ("-OH") of the polymer. These chemiresistors made from PVA films whose polymer backbone is 88% hydroxylated (PVA88) have a high sensitivity to water, while chemiresistors made from PVA75 have a higher sensitivity to methanol. The minor differences in polymer composition result in films with different Hildebrand volubility parameters. The relative responses of several different PVA-based chemiresistors to solvents with different volubility parameters are presented. In addition, polyvinyl acetate (PVAC) films with PVA88 are used in an arraymore » to distinguish the responses to methanol-water mixtures.« less

Antihypertensive neutral lipid

DOEpatents

Snyder, Fred L.; Blank, Merle L.

1986-01-01

The invention relates to the discovery of a class of neutral acetylated ether-linked glycerolipids having the capacity to lower blood pressure in warm-blooded animals. This physiological effect is structure sensitive requiring a long chain alkyl group at the sn-1 position and a short carbon chain acyl group (acetyl or propionyl) at the sn-2 position, and a hydroxyl group at the sn-3 position.

Antihypertensive neutral lipid

DOEpatents

Snyder, F.L.; Blank, M.L.

1984-10-26

The invention relates to the discovery of a class of neutral acetylated either-linked glycerolipids having the capacity to lower blood presure in warm-blooded animals. This physiological effect is structure sensitive requiring a long chain alkyl group at the sn-1 position and a short carbon chain acyl group (acetyl or propionyl) at the sn-2 position, and a hydroxyl group at the sn-3 position.

Water Contact Angle Dependence with Hydroxyl Functional Groups on Silica Surfaces under CO2 Sequestration Conditions.

PubMed

Chen, Cong; Zhang, Ning; Li, Weizhong; Song, Yongchen

2015-12-15

Functional groups on silica surfaces under CO2 sequestration conditions are complex due to reactions among supercritical CO2, brine and silica. Molecular dynamics simulations have been performed to investigate the effects of hydroxyl functional groups on wettability. It has been found that wettability shows a strong dependence on functional groups on silica surfaces: silanol number density, space distribution, and deprotonation/protonation degree. For neutral silica surfaces with crystalline structure (Q(3), Q(3)/Q(4), Q(4)), as silanol number density decreases, contact angle increases from 33.5° to 146.7° at 10.5 MPa and 318 K. When Q(3) surface changes to an amorphous structure, water contact angle increases 20°. Water contact angle decreases about 12° when 9% of silanol groups on Q(3) surface are deprotonated. When the deprotonation degree increases to 50%, water contact angle decreases to 0. The dependence of wettability on silica surface functional groups was used to analyze contact angle measurement ambiguity in literature. The composition of silica surfaces is complicated under CO2 sequestration conditions, the results found in this study may help to better understand wettability of CO2/brine/silica system.

Putative free radical-scavenging activity of an extract of Cineraria maritima in preventing selenite-induced cataractogenesis in Wistar rat pups

PubMed Central

Anitha, Thirugnanasambandhar Sivasubramanian; Muralidharan, Arumugam Ramachandran; Annadurai, Thangaraj; Jesudasan, Christdas Arul Nelson; Thomas, Philip Aloysius

2013-01-01

Purpose To investigate the possible free radical-scavenging activity of an extract of Cineraria maritima on selenite-induced cataractous lenses in Wistar rat pups. Methods In the present study, Wistar rat pups were divided into three experimental groups. On P10, Group I (control) rat pups received an intraperitoneal injection of 0.89% saline. Rats in groups II (selenite-challenged, untreated) and III (selenite-challenged, C. maritima treated) received a subcutaneous injection of sodium selenite (19 μmol/kg bodyweight); Group III rat pups also received an intraperitoneal injection of the extract of C. maritima (350 mg/kg bodyweight) once daily P9–14. Both eyes of each pup were examined from P16 until P30. Cytochemical localization of nitroblue tetrazolium salts and generation of superoxide, hydroxyl, and nitric oxide levels were measured. The expression of the inducible nitric oxide synthase gene was evaluated with reverse transcription-PCR. Immunoblot analysis was also performed to confirm the differential expression of the inducible nitric oxide synthase protein. Results Subcutaneous injection of sodium selenite led to severe oxidative damage in the lenticular tissues, shown by increased formation of formazan crystals, elevated generation of superoxide, hydroxyl, and nitric oxide radicals, and elevated inducible nitric oxide synthase gene and protein expression that possibly contributed to the opacification of the lens and thus cataract formation. When rat pups were treated with intraperitoneal administration of the extract of C. maritima, the generation of free radicals as well as the messenger ribonucleic acid and protein expression of inducible nitric oxide synthase were maintained at near normal levels. Conclusions The data generated by this study suggest that an ethanolic extract of C. maritima possibly prevents cataractogenesis in a rat model by minimizing free radical generation. PMID:24357923

Predictions of glass transition temperature for hydrogen bonding biomaterials.

PubMed

van der Sman, R G M

2013-12-19

We show that the glass transition of a multitude of mixtures containing hydrogen bonding materials correlates strongly with the effective number of hydroxyl groups per molecule, which are available for intermolecular hydrogen bonding. This correlation is in compliance with the topological constraint theory, wherein the intermolecular hydrogen bonds constrain the mobility of the hydrogen bonded network. The finding that the glass transition relates to hydrogen bonding rather than free volume agrees with our recent finding that there is little difference in free volume among carbohydrates and polysaccharides. For binary and ternary mixtures of sugars, polyols, or biopolymers with water, our correlation states that the glass transition temperature is linear with the inverse of the number of effective hydroxyl groups per molecule. Only for dry biopolymer/sugar or sugar/polyol mixtures do we find deviations due to nonideal mixing, imposed by microheterogeneity.

iHyd-PseCp: Identify hydroxyproline and hydroxylysine in proteins by incorporating sequence-coupled effects into general PseAAC.

PubMed

Qiu, Wang-Ren; Sun, Bi-Qian; Xiao, Xuan; Xu, Zhao-Chun; Chou, Kuo-Chen

2016-07-12

Protein hydroxylation is a posttranslational modification (PTM), in which a CH group in Pro (P) or Lys (K) residue has been converted into a COH group, or a hydroxyl group (-OH) is converted into an organic compound. Closely associated with cellular signaling activities, this type of PTM is also involved in some major diseases, such as stomach cancer and lung cancer. Therefore, from the angles of both basic research and drug development, we are facing a challenging problem: for an uncharacterized protein sequence containing many residues of P or K, which ones can be hydroxylated, and which ones cannot? With the explosive growth of protein sequences in the post-genomic age, the problem has become even more urgent. To address such a problem, we have developed a predictor called iHyd-PseCp by incorporating the sequence-coupled information into the general pseudo amino acid composition (PseAAC) and introducing the "Random Forest" algorithm to operate the calculation. Rigorous jackknife tests indicated that the new predictor remarkably outperformed the existing state-of-the-art prediction method for the same purpose. For the convenience of most experimental scientists, a user-friendly web-server for iHyd-PseCp has been established at http://www.jci-bioinfo.cn/iHyd-PseCp, by which users can easily obtain their desired results without the need to go through the complicated mathematical equations involved.

The effect of surfactant-free TiO2 surface hydroxyl groups on physicochemical, optical and self-cleaning properties of developed coatings on polycarbonate

NASA Astrophysics Data System (ADS)

Yaghoubi, H.; Dayerizadeh, A.; Han, S.; Mulaj, M.; Gao, W.; Li, X.; Muschol, M.; Ma, S.; Takshi, A.

2013-12-01

TiO2 is a prototypical transition metal oxide with physicochemical properties that can be modified more readily through sol-gel synthesis than through other techniques. Herein, we report on the change in the density of the hydroxyl groups on the surface of synthesized surfactant-free TiO2 nanoparticles in water due to varying the pH (7.3, 8.3, 9.3 and 10.3) of the peroxotitanium complex, i.e. the amorphous sol, prior to refluxing. This resulted in colloidal solutions with differing crystallinity, nanoparticle size, optical indirect bandgaps and photocatalytic activity. It was shown that increasing the density of hydroxyl groups on TiO2 particles coupled with low-temperature annealing (90 °C) induced an anatase to rutile transformation. Increasing the pH of the peroxotitanium complex interrupted the formation of anatase phase in crystalline sol, as evidenced by intensity increases of the Raman bands at ˜822 (Ti-O-H) and 906 cm-1 (vibrational Ti-O-H) and an intensity decrease of the band at 150 cm-1 (anatase photonic Eg). Films prepared from higher pH suspensions showed lower roughness. The reaction rate constants for photo-induced self-cleaning activity of TiO2 films prepared from colloidal solutions at pH 7.3, 8.3, 9.3 and 10.3 were estimated at 0.017 s-1, 0.014 s-1, 0.007 s-1 and 0.006 s-1, respectively.

Tuning of electronic properties and dynamical stability of graphene oxide with different functional groups

NASA Astrophysics Data System (ADS)

Dabhi, Shweta D.; Jha, Prafulla K.

2017-09-01

The structural, electronic and vibrational properties of graphene oxide (GO) with varying proportion of epoxy and hydroxyl functional groups have been studied using density functional theory. The functional groups and oxygen density have an obvious influence on the electronic and vibrational properties. The dependence of band gap on associated functional groups and oxygen density shows a possibility of tuning the band gap of graphene by varying the functional groups as well as oxidation level. The absorption of high oxygen content in graphene leads to the gap opening and resulting in a transition from semimetal to semiconductor. Phonon dispersion curves show no imaginary frequency or no softening of any phonon mode throughout the Brillouin zone which confirms the dynamical stability of all considered GO models. Different groups and different oxygen density result into the varying characteristics of phonon modes. The computed results show good agreement with the experimental observations. Our results present interesting possibilities for engineering the electronic properties of graphene and GO and impact the fabrication of new electronics.

Effects of curing conditions on the structure of sodium carboxymethyl starch/mineral matrix system: FT-IR investigation.

PubMed

Kaczmarska, Karolina; Grabowska, Beata; Bobrowski, Artur; Cukrowicz, Sylwia

2018-04-24

Strength properties of the microwave cured molding sands containing binders in a form of the aqueous solution of sodium carboxymethyl starch (CMS-Na) are higher than the same molding composition cured by conventional heating. Finding the reason of this effect was the main purpose in this study. Structural changes caused by both physical curing methods of molding sands systems containing mineral matrix (silica sand) and polymer water-soluble binder (CMS-Na) were compared. It was shown, by means of the FT-IR spectroscopic studies, that the activation of the polar groups in the polymer macromolecules structure as well as silanol groups on the mineral matrix surfaces was occurred in the microwave radiation. Binding process in microwave-cured samples was an effect of formation the hydrogen bonds network between hydroxyl and/or carbonyl groups present in polymer and silanol groups present in mineral matrix. FT-IR studies of structural changes in conventional and microwave cured samples confirm that participation of hydrogen bonds is greater after microwave curing than conventional heating. Copyright © 2018 Elsevier B.V. All rights reserved.

Vibrational Study of Melatonin and its Radioprotective Activity towards Hydroxyl Radical

NASA Astrophysics Data System (ADS)

Singh, Gurpreet; Kaur, Sarvpreet; Saini, G. S. S.

2011-12-01

Vibrational study of Melatonin (N-acetyl 5-methoxytrypatamin) was done using FTIR and Raman spectroscopy. DFT calculations were employed to the structural analysis of melatonin and to the end products. The theoretical calculations confirmed the different observed vibrational modes. The optimized structure energy calculations of the different end products confirmed the most probable site of the hydroxyl radical attack is the hydrogen attached to nitrogen present in the indole ring.

Photocatalytic Hydrogen-Evolution Cross-Couplings: Benzene C-H Amination and Hydroxylation.

PubMed

Zheng, Yi-Wen; Chen, Bin; Ye, Pan; Feng, Ke; Wang, Wenguang; Meng, Qing-Yuan; Wu, Li-Zhu; Tung, Chen-Ho

2016-08-17

We present a blueprint for aromatic C-H functionalization via a combination of photocatalysis and cobalt catalysis and describe the utility of this strategy for benzene amination and hydroxylation. Without any sacrificial oxidant, we could use the dual catalyst system to produce aniline directly from benzene and ammonia, and phenol from benzene and water, both with evolution of hydrogen gas under unusually mild conditions in excellent yields and selectivities.

Producing Lignin-Based Polyols through Microwave-Assisted Liquefaction for Rigid Polyurethane Foam Production

PubMed Central

Xue, Bai-Liang; Wen, Jia-Long; Sun, Run-Cang

2015-01-01

Lignin-based polyols were synthesized through microwave-assisted liquefaction under different microwave heating times (5–30 min). The liquefaction reactions were carried out using polyethylene glycol (PEG-400)/glycerol as liquefying solvents and 97 wt% sulfur acid as a catalyst at 140 °C. The polyols obtained were analyzed for their yield, composition and structural characteristics using gel permeation chromatography (GPC), Fourier transform infrared (FT-IR) and nuclear magnetic resonance (NMR) spectra. FT-IR and NMR spectra showed that the liquefying solvents reacted with the phenol hydroxyl groups of the lignin in the liquefied product. With increasing microwave heating time, the viscosity of polyols was slightly increased and their corresponding molecular weight (MW) was gradually reduced. The optimal condition at the microwave heating time (5 min) ensured a high liquefaction yield (97.47%) and polyol with a suitable hydroxyl number (8.628 mmol/g). Polyurethane (PU) foams were prepared by polyols and methylene diphenylene diisocyanate (MDI) using the one-shot method. With the isocyanate/hydroxyl group ([NCO]/[OH]) ratio increasing from 0.6 to 1.0, their mechanical properties were gradually increased. This study provided some insight into the microwave-assisted liquefied lignin polyols for the production of rigid PU foam. PMID:28787959

Syntheses and characterizations of secondary Pb-O bonding supported Pb(II)-sulfonate complexes

NASA Astrophysics Data System (ADS)

Huang, Guo-Zhen; Zou, Xin; Zhu, Zhi-Biao; Deng, Zhao-Peng; Huo, Li-Hua; Gao, Shan

2018-06-01

The reaction of Pb(II) salts and mono- or disulfonates leads to the formation of eight new Pb(II)-mono/disulfonate complexes, [Pb(L1)(H2O)]2 (1), [Pb4(L2)2(AcO)2]n·5nH2O (2), [Pb(L3)(H2O)]2 (3), [Pb(HL4)(H2O)2]n·nH2O (4), [Pb(HL5)(H2O)2]n·2nH2O (5), [Pb(H2L6)(H2O)]n·nDMF·2nH2O (6), [Pb2(H3L7)4(H2O)6]·2H2O (7) and [Pb(H2L7)(H2O)]n·nH2O (8) (H2L1= 2-hydroxy-5-methyl-benzenesulfonic acid, H3L2= 2-hydroxyl-5-methyl- 1,3-benzenedisulfonic acid, H2L3= 2-hydroxy-5-nitro-benzenesulfonic acid, H3L4= 2-hydroxyl-5-bromo-1,3- benzenedisulfonic acid, H3L5= 2-hydroxyl-5-carboxyl-benzenesulfonic acid, H4L6= 2,5-dihydroxyl-3-carboxyl- benzenesulfonic acid, H4L7= 2,4-dihydroxyl-5-carboxyl-benzenesulfonic acid, DMF = N,N'-dimethyl-formamide, AcO- = acetate), which have been characterized by elemental analysis, IR, TG, PL, powder and single-crystal X-ray diffraction. In view of the primary Pb-O bonds, these eight complexes exhibit diverse dinuclear (1, 3 and 7), helical chain (4), wave-like chain (5), linear chain (6), zigzag chain (8) and layer structure (2), in which the Pb(II) cations present different hemi-directed geometries. Taking the secondary Pb-O bonds into account, chain structure for complex 7, layer motifs for complexes 1 and 3-6, as well as 3-D framework for complex 8 are observed with Pb(II) cations showing more intricate holo-directed geometries. The various coordination modes of these seven different mono/disulfonate anions are responsible for the formation of these multiple structures. Furthermore, the introduction of hydroxyl and carboxyl groups increases the coordination ability of sulfonate to the p-block metal cation. Luminescent analyses indicate that complex 7 presents purple emission at 395 nm at room temperature.

GRID and docking analyses reveal a molecular basis for flavonoid inhibition of Src family kinase activity.

PubMed

Wright, Bernice; Watson, Kimberly A; McGuffin, Liam J; Lovegrove, Julie A; Gibbins, Jonathan M

2015-11-01

Flavonoids reduce cardiovascular disease risk through anti-inflammatory, anti-coagulant and anti-platelet actions. One key flavonoid inhibitory mechanism is blocking kinase activity that drives these processes. Flavonoids attenuate activities of kinases including phosphoinositide-3-kinase, Fyn, Lyn, Src, Syk, PKC, PIM1/2, ERK, JNK and PKA. X-ray crystallographic analyses of kinase-flavonoid complexes show that flavonoid ring systems and their hydroxyl substitutions are important structural features for their binding to kinases. A clearer understanding of structural interactions of flavonoids with kinases is necessary to allow construction of more potent and selective counterparts. We examined flavonoid (quercetin, apigenin and catechin) interactions with Src family kinases (Lyn, Fyn and Hck) applying the Sybyl docking algorithm and GRID. A homology model (Lyn) was used in our analyses to demonstrate that high-quality predicted kinase structures are suitable for flavonoid computational studies. Our docking results revealed potential hydrogen bond contacts between flavonoid hydroxyls and kinase catalytic site residues. Identification of plausible contacts indicated that quercetin formed the most energetically stable interactions, apigenin lacked hydroxyl groups necessary for important contacts and the non-planar structure of catechin could not support predicted hydrogen bonding patterns. GRID analysis using a hydroxyl functional group supported docking results. Based on these findings, we predicted that quercetin would inhibit activities of Src family kinases with greater potency than apigenin and catechin. We validated this prediction using in vitro kinase assays. We conclude that our study can be used as a basis to construct virtual flavonoid interaction libraries to guide drug discovery using these compounds as molecular templates. Crown Copyright © 2015. Published by Elsevier Inc. All rights reserved.

A domain swapping approach to elucidate differential regiospecific hydroxylation by geraniol and linalool synthases from perilla.

PubMed

Sato-Masumoto, Naoko; Ito, Michiho

2014-06-01

Geraniol and linalool are acyclic monoterpenes found in plant essential oils that have attracted much attention for their commercial use and in pharmaceutical studies. They are synthesized from geranyl diphosphate (GDP) by geraniol and linalool synthases, respectively. Both synthases are very similar at the amino acid level and share the same substrate; however, the position of the GDP to which they introduce hydroxyl groups is different. In this study, the mechanisms underlying the regiospecific hydroxylation of geraniol and linalool synthases were investigated using a domain swapping approach and site-directed mutagenesis in perilla. Sequences of the synthases were divided into ten domains (domains I to IV-4), and each corresponding domain was exchanged between both enzymes. It was shown that different regions were important for the formation of geraniol and linalool, namely, domains IV-1 and -4 for geraniol, and domains III-b, III-d, and IV-4 for linalool. These results suggested that the conformation of carbocation intermediates and their electron localization were seemingly to be different between geraniol and linalool synthases. Further, five amino acids in domain IV-4 were apparently indispensable for the formation of geraniol and linalool. According to three-dimensional structural models of the synthases, these five residues seemed to be responsible for the different spatial arrangement of the amino acid at H524 in the case of geraniol synthase, while N526 is the corresponding residue in linalool synthase. These results suggested that the side-chains of these five amino acids, in combination with several relevant domains, localized the positive charge in the carbocation intermediate to determine the position of the introduced hydroxyl group. Copyright © 2014 Elsevier Ltd. All rights reserved.

Kinetics of surface processes for Mo(CO){sub 6} on partially dehydroxylated alumina and hydroxylated alumina. Observation of Mo(CO){sub 5}(ads)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reddy, K.P.; Brown, T.L.

1995-03-15

The adsorption of Mo(CO){sub 6} on partially dehydroxylated alumina (PDA) and hydroxylated alumina (HA) has been studied using IR and UV-vis spectroscopy. The results from these experiments suggest that the initially physisorbed Mo(CO){sub 6} coordinates to two distinct Lewis acid sites on the surface of PDA, one much more abundant than the other, with an apparent single rate constant 2.3 x 10{sup {minus}3} s{sup {minus}1} at 298 K. The Mo(CO){sub 6}(ads) in turn loses CO reversibly, with an apparent single rate constant 1.8 x 10{sup {minus}4} s{sup {minus}1} at 298 K to form Mo(CO){sub 5}(ads). Upon removal of gas phasemore » CO released in the first step, Mo(CO){sub 5}(ads) loses two additional COs to form Mo(CO){sub 3}(ads). Alternatively, on HA physisorbed Mo(CO){sub 6} undergoes nucleophilic attack by hydroxyl groups, which results in cis-labilization of a carbonyl group, leading in turn to the formation of Mo(CO){sub 5}(L), where L is a surface hydroxyl. The Mo(CO){sub 5}(L) so formed loses additional carbonyls to form a lower subcarbonyl. The decarbonylation process appears to be faster than on PDA. The experimental data indicate that there are no Al{sup 31} exposed on HA. All the observed decarbonylation processes are reversible under CO at room temperature on both HA and PDA. The addition of CO{sub 2} to the subcarbonyl on HA results in the formation of a bicarbonate, with displacement of the subcarbonyls. 24 refs., 11 figs., 1 tab.« less

Comparison of Polyurethanes with Polyhydroxyurethanes: Effect of the Hydroxyl Group on Structure-Property Relationships

NASA Astrophysics Data System (ADS)

Leitsch, Emily K.; Lombardo, Vince M.; Scheidt, Karl A.; Torkelson, John M.

2014-03-01

Polyurethanes (PUs) are commonly synthesized by rapid step-growth polymerization through the reaction of a multifunctional alcohol with a polyisocyanate. PUs can be prepared at ambient conditions utilizing a variety of starting material molecular weights and backbones, resulting in highly tunable thermal and physical properties. The urethane linkages as well as the nanophase separated morphology attainable in PU materials lead to desirable properties including elastomeric character and adhesion. The isocyanate-based monomers used in the synthesis of traditional PUs have come under increasing regulatory pressure and thus inspired the investigation of alternative routes for the formation of PU materials. We examine an alternative route to synthesize PU- the reaction of five-membered cyclic carbonate with amines. This reaction results in the formation of a urethane linkage with an adjacent alcohol group. The effects of this hydroxyl group on the thermal and mechanical properties of the resulting polymer are investigated and compared with an analogous traditional PU system.

Nucleic Acid Detection Methods

DOEpatents

Smith, Cassandra L.; Yaar, Ron; Szafranski, Przemyslaw; Cantor, Charles R.

1998-05-19

The invention relates to methods for rapidly determining the sequence and/or length a target sequence. The target sequence may be a series of known or unknown repeat sequences which are hybridized to an array of probes. The hybridized array is digested with a single-strand nuclease and free 3'-hydroxyl groups extended with a nucleic acid polymerase. Nuclease cleaved heteroduplexes can be easily distinguish from nuclease uncleaved heteroduplexes by differential labeling. Probes and target can be differentially labeled with detectable labels. Matched target can be detected by cleaving resulting loops from the hybridized target and creating free 3-hydroxyl groups. These groups are recognized and extended by polymerases added into the reaction system which also adds or releases one label into solution. Analysis of the resulting products using either solid phase or solution. These methods can be used to detect characteristic nucleic acid sequences, to determine target sequence and to screen for genetic defects and disorders. Assays can be conducted on solid surfaces allowing for multiple reactions to be conducted in parallel and, if desired, automated.

Electronic Structure Calculations of Ammonia Adsorption on Graphene and Graphene Oxide with Epoxide and Hydroxyl Groups

NASA Astrophysics Data System (ADS)

Nancy Anna Anasthasiya, A.; Khaneja, Mamta; Jeyaprakash, B. G.

2017-10-01

Ammonia adsorption on graphene (G) and graphene oxide (GO) was investigated through density functional theory calculations. In the GO system, the obtained binding energy, band gap, charge transfer and electronic structure revealed that the epoxide (GO-O) and hydroxyl groups (GO-OH) in GO enhance the NH3 adsorption, which leads to the chemisorption of NH3 on GO. The dissociation of NH3 to NH2 and formation of OH was also observed when the O and H atoms were separated at 0.985 Å, 1.019 Å, 1.035 Å, and 1.044 Å for various GO systems. The maximum charge transfer value was found to be 0.054 |e| with the binding energy of 1.143 eV for GO with a single epoxide (GO-1O) group. The charge transfer from NH3 to G or GO and the bond formation in this study agree with the reported experimental results.

Synthetic tripodal receptors for carbohydrates. Pyrrole, a hydrogen bonding partner for saccharidic hydroxyls.

PubMed

Francesconi, Oscar; Gentili, Matteo; Roelens, Stefano

2012-09-07

The carbohydrate recognition properties of synthetic tripodal receptors relying on H-bonding interactions have highlighted the crucial role played by the functional groups matching saccharidic hydroxyls. Herein, pyrrole and pyridine, which emerged as two of the most effective H-bonding groups, were quantitatively compared through their isostructural substitution within the architecture of a shape-persistent bicyclic cage receptor. NMR and ITC binding studies gave for the pyrrolic receptor a 20-fold larger affinity toward octyl-β-d-glucopyranoside in CDCl(3), demonstrating the superior recognition properties of pyrrole under conditions in which differences would depend on the intrinsic binding ability of the two groups. The three-dimensional structures of the two glucoside complexes in solution were elucidated by combined NMR and molecular mechanics computational techniques, showing that the origin of the stability difference between the two closely similar complex structures resides in the ability of pyrrole to establish shorter/stronger H-bonds with the glucosidic ligand compared to pyridine.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ahmad, Bhat Zahoor; Want, Basharat, E-mail: bawant@kashmiruniversity.ac.in

We investigate the structure and ferroelectric behavior of a lanthanide based metal-organic framework (MOF), [Nd(C{sub 4}H{sub 5}O{sub 6})(C{sub 4}H{sub 4}O{sub 6})][3H{sub 2}O]. X-ray crystal structure analyses reveal that it crystallizes in the P4{sub 1}2{sub 1}2 space group with Nd centres, coordinated by nine oxygen atoms, forming a distorted capped square antiprismatic geometry. The molecules, bridged by tartrate ligands, form a 2D chiral structure. The 2D sheets are further linked into a 3D porous framework via strong hydrogen-bonding scheme (O-H…O ≈ 2.113 Å). Dielectric studies reveal two anomalies at 295 K and 185 K. The former is a paraelectric-ferroelectric transition, and the later is attributed tomore » the freezing down of the motion of the hydroxyl groups. The phase transition is of second order, and the spontaneous polarization in low temperature phase is attributed to the ordering of protons of hydroxyl groups. The dielectric nonlinearity parameters have been calculated using Landau– Devonshire phenomenological theory. In addition, the most recent semiempirical models, Sparkle/PM7, Sparkle/RM1, and Sparkle/AM1, are tested on the present system to assay the accuracy of semiempirical quantum approaches to predict the geometries of solid MOFs. Our results show that Sparkle/PM7 model is the most accurate to predict the unit cell structure and coordination polyhedron geometry. The semiempirical methods are also used to calculate different ground state molecular properties.« less

Structure, ferroelectric ordering, and semiempirical quantum calculations of lanthanide based metal-organic framework: [Nd(C4H5O6)(C4H4O6)][3H2O

NASA Astrophysics Data System (ADS)

Ahmad, Bhat Zahoor; Want, Basharat

2016-04-01

We investigate the structure and ferroelectric behavior of a lanthanide based metal-organic framework (MOF), [Nd(C4H5O6)(C4H4O6)][3H2O]. X-ray crystal structure analyses reveal that it crystallizes in the P41212 space group with Nd centres, coordinated by nine oxygen atoms, forming a distorted capped square antiprismatic geometry. The molecules, bridged by tartrate ligands, form a 2D chiral structure. The 2D sheets are further linked into a 3D porous framework via strong hydrogen-bonding scheme (O-H…O ≈ 2.113 Å). Dielectric studies reveal two anomalies at 295 K and 185 K. The former is a paraelectric-ferroelectric transition, and the later is attributed to the freezing down of the motion of the hydroxyl groups. The phase transition is of second order, and the spontaneous polarization in low temperature phase is attributed to the ordering of protons of hydroxyl groups. The dielectric nonlinearity parameters have been calculated using Landau- Devonshire phenomenological theory. In addition, the most recent semiempirical models, Sparkle/PM7, Sparkle/RM1, and Sparkle/AM1, are tested on the present system to assay the accuracy of semiempirical quantum approaches to predict the geometries of solid MOFs. Our results show that Sparkle/PM7 model is the most accurate to predict the unit cell structure and coordination polyhedron geometry. The semiempirical methods are also used to calculate different ground state molecular properties.

Intramolecular interactions in the polar headgroup of sphingosine: serinol.

PubMed

Loru, Donatella; Peña, Isabel; Alonso, José L; Sanz, M Eugenia

2016-03-04

The intramolecular interactions in the lipid sphingosine have been elucidated through the investigation of the amino alcohol serinol which mimics its polar headgroup. Intricate networks of intramolecular hydrogen bonds involving the hydroxyl groups and the amino group contribute to the stabilisation of five different conformations observed in the broadband rotational spectrum.

Chemical groups and structural characterization of lignin via thiol-mediated demethylation

Treesearch

Lihong Hu; Hui Pan; Yonghong Zhou; Chung-Yun Hse; Chengguo Liu; Baofang Zhang; Bin Xu

2014-01-01

A new approach to increase the reactivity of lignin by thiol-mediated demethylation was investigated in this study. Demethylated lignin was characterized by the changes in its hydroxyl and methoxyl groups, molecular weight, and other properties using titration and spectroscopy methods including FT-IR, 1H NMR, UV,and GPC. The total...

Electrospun polyvinylpyrrolidone (PVP)/green tea extract composite nanofiber mats and their antioxidant activities

NASA Astrophysics Data System (ADS)

Pusporini, Pusporini; Edikresnha, Dhewa; Sriyanti, Ida; Suciati, Tri; Miftahul Munir, Muhammad; Khairurrijal, Khairurrijal

2018-05-01

Electrospinning was employed to make PVP (polyvinylpyrrolidone)/GTE (green tea extract) composite nanofiber mats. The electrospun PVP nanofiber mat as well as the PVP/GTE nanofiber mats were uniform. The average fiber diameter of PVP/GTE composite nanofiber mat decreased with increasing the GTE weight fraction (or decreasing the PVP weight fraction) in the PVP/GTE solution because the PVP/GTE solution concentration decreased. Then, the broad FTIR peak representing the stretching vibrations of O–H in hydroxyl groups of phenols and the stretching of N–H in amine groups of the GTE paste shifted to higher wavenumbers in the PVP/GTE composite nanofiber mats. These peak shifts implied that PVP and catechins of GTE in the PVP/GTE composite nanofiber mats had intermolecular interactions via hydrogen bonds between carbonyl groups of PVP and hydroxyl groups of catechins in GTE. Lastly, the antioxidant activity of the PVP/GTE composite nanofiber mat increased with reducing the average fiber diameter because the amount of catechins in the composite nanofiber mat increased with the increase of surface area due to the reduction of the average fiber diameter.

Surface Modification by Atmospheric Pressure Plasma for Improved Bonding

NASA Astrophysics Data System (ADS)

Williams, Thomas Scott

An atmospheric pressure plasma source operating at temperatures below 150?C and fed with 1.0-3.0 volume% oxygen in helium was used to activate the surfaces of the native oxide on silicon, carbon-fiber reinforced epoxy composite, stainless steel type 410, and aluminum alloy 2024. Helium and oxygen were passed through the plasma source, whereby ionization occurred and ˜10 16 cm-3 oxygen atoms, ˜1015 cm -3 ozone molecules and ˜1016 cm-3 metastable oxygen molecules (O21Deltag) were generated. The plasma afterglow was directed onto the substrate material located 4 mm downstream. Surface properties of the plasma treated materials have been investigated using water contact angle (WCA), atomic force microscopy (AFM), infrared spectroscopy (IR), and x-ray photoelectron spectroscopy (XPS). The work presented herein establishes atmospheric-pressure plasma as a surface preparation technique that is well suited for surface activation and enhanced adhesive bond strength in a variety of materials. Atmospheric plasma activation presents an environmentally friendly alternative to wet chemical and abrasive methods of surface preparation. Attenuated total internal reflection infrared spectroscopy was used to study the aging mechanism of the native oxide on silicon. During storage at ambient conditions, the water contact angle of a clean surface increased from <5° to 40° over a period of 12 hours. When stored under a nitrogen purge, the water contact angle of a clean surface increased from <5° to 30° over a period of 40-60 hours. The change in contact angle resulted from the adsorption of nonanal onto the exposed surface hydroxyl groups. The rate of adsorption of nonanal under a nitrogen purged atmosphere ranged from 0.378+/-0.011 hr-1 to 0.182+/-0.008 hr -1 molecules/(cm2•s), decreasing as the fraction of hydrogen-bonded hydroxyl groups increased from 49% to 96% on the SiO 2 surface. The adsorption of the organic contaminant could be suppressed indefinitely by storing the silicon wafers in the presence of activated carbon or in a freezer at -22°C. The enhancement of adhesive bond strength and durability for carbon-fiber reinforced epoxy composite, stainless steel type 410, and aluminum alloy 2024 was demonstrated with the atmospheric pressure helium-oxygen plasma. All surfaces studied were converted from a hydrophobic state with a water contact angle of 65° to 80° into a hydrophilic state with a water contact angle between 20° and 40° within 5 seconds of plasma exposure. X-ray photoelectron spectroscopy confirmed that the carbon atoms on the carbon-fiber/epoxy composite were oxidized, yielding 17 atom% carboxylic acid groups, 10% ketones or aldehydes and 9% alcohols. Analysis of stainless steel and aluminum by XPS illustrate oxidation of the metal surface and an increase in the concentration of hydroxyl groups in the oxide film. Following plasma activation, the total hydroxyl species concentration on stainless steel increased from 31% to 57%, while aluminum exhibited an increase from 4% to 16% hydroxyl species. Plasma activation of the surface led to an increase in bond strength of the different surfaces by up to 150% when using Cytec FM300 and FM300-2 epoxy adhesives. Wedge crack extension tests following plasma activation revealed cohesive failure percentages of 97% for carbon-fiber/epoxy composite bonded to stainless steel, and 96% for aluminum bonded to itself. The bond strength and durability of the substrates correlated with changes in the specific surface chemistry, not the wetting angle or the morphological properties of the material. This suggests that enhanced chemical bonding at the interface was responsible for the improvement in mechanical properties following plasma activation. The surface preparation of polymers and composites using atmospheric pressure plasmas is a promising technique for replacing traditional methods of surface preparation by sanding, grit blasting or peel ply. After oxygen plasma activation and joining the materials together with epoxy, one observes 100% cohesive failure within the cured film adhesive. Depending on the material, the lap shear strength can be increased several fold over that achieved by either solvent wiping or abrasion. The trends in adhesion with plasma exposure time do not correlate well with surface wetting or roughness; instead they correlate with the fraction of the polymer surface sites that are converted into carboxylic acid groups.

Tegument galactosylceramides of the cestode Spirometra mansonoides.

PubMed

Singh, B N; Costello, C E; Levery, S B; Walenga, R W; Beach, D H; Mueller, J F; Holz, G G

1987-11-01

The brush border-like surface of the tegument of the adult and the plerocercoid larva of a pseudophyllidean cestode, Spirometra mansonoides, has been shown to contain hydroxylated galactosylceramides. D-Galactosyl-N-(2-D-hydroxyoctadecanoyl)-D-phytosphingosine, D-galactosyl-N-(2-D-hydroxyoctadecanoyl)-D-dihydrosphingosine and D-galactosyl-N-(octadecanoyl)-D-phytosphingosine were identified as major glycosphingolipids in a tegumental plasma membrane fraction with associated microtriches, by combinations of chromatography (column, high performance thin-layer, gas-liquid), mass spectrometry (electron impact, field desorption, fast atom bombardment, collisionally induced decomposition) and proton nuclear magnetic resonance spectrometry. Galactosylceramides with hydroxylated long chain bases and fatty acids are known to occur in some eukaryotic microbes and in cells of vertebrate tissues exposed to plasma membrane destabilizing environments. This has led to a proposal that the capacity of hydroxylated ceramide moieties for intermolecular hydrogen bonding among themselves and with phosphoglycerides acts to stabilize the plasma membrane. Saturated fatty acyl groups in the ceramides would enhance stabilization by their orderly packing in the lipid bilayer. Consequently, the presence of such hydroxylated galactosylceramides in the tegument surface of S. mansonoides may contribute to the maintenance of its normal barrier properties in the face of the varied environmental insults encountered by the cestode in its life-cycle.

Lincomycin Biosynthesis Involves a Tyrosine Hydroxylating Heme Protein of an Unusual Enzyme Family

PubMed Central

Novotna, Jitka; Olsovska, Jana; Novak, Petr; Mojzes, Peter; Chaloupkova, Radka; Kamenik, Zdenek; Spizek, Jaroslav; Kutejova, Eva; Mareckova, Marketa; Tichy, Pavel; Damborsky, Jiri; Janata, Jiri

2013-01-01

The gene lmbB2 of the lincomycin biosynthetic gene cluster of Streptomyces lincolnensis ATCC 25466 was shown to code for an unusual tyrosine hydroxylating enzyme involved in the biosynthetic pathway of this clinically important antibiotic. LmbB2 was expressed in Escherichia coli, purified near to homogeneity and shown to convert tyrosine to 3,4-dihydroxyphenylalanine (DOPA). In contrast to the well-known tyrosine hydroxylases (EC 1.14.16.2) and tyrosinases (EC 1.14.18.1), LmbB2 was identified as a heme protein. Mass spectrometry and Soret band-excited Raman spectroscopy of LmbB2 showed that LmbB2 contains heme b as prosthetic group. The CO-reduced differential absorption spectra of LmbB2 showed that the coordination of Fe was different from that of cytochrome P450 enzymes. LmbB2 exhibits sequence similarity to Orf13 of the anthramycin biosynthetic gene cluster, which has recently been classified as a heme peroxidase. Tyrosine hydroxylating activity of LmbB2 yielding DOPA in the presence of (6R)-5,6,7,8-tetrahydro-L-biopterin (BH4) was also observed. Reaction mechanism of this unique heme peroxidases family is discussed. Also, tyrosine hydroxylation was confirmed as the first step of the amino acid branch of the lincomycin biosynthesis. PMID:24324587

Hydroxyl radical mediated DNA base modification by manmade mineral fibres.

PubMed Central

Leanderson, P; Söderkvist, P; Tagesson, C

1989-01-01

Manmade mineral fibres (MMMFs) were examined for their ability to hydroxylate 2-deoxyguanosine (dG) to 8-hydroxydeoxyguanosine (8-OH-dG), a reaction that is mediated by hydroxyl radicals. It appeared that (1) catalase and the hydroxyl radical scavengers, dimethylsulphoxide and sodium benzoate, inhibited the hydroxylation, whereas Fe2+ and H2O2 potentiated it; (2) pretreatment of MMMFs with the iron chelator, deferoxamine, or with extensive heat (200-400 degrees C), attenuated the hydroxylation; (3) the hydroxylation obtained by various MMMFs varied considerably; (4) there was no apparent correlation between the hydroxylation and the surface area of different MMMFs, although increasing the surface area of a fibre by crushing it increased its hydroxylating capacity; and (5) there was good correlation between the hydroxylation of dG residues in DNA and the hydroxylation of pure dG in solution for the 16 different MMMFs investigated. These findings indicate that MMMFs cause a hydroxyl radical mediated DNA base modification in vitro and that there is considerable variation in the reactivity of different fibre species. The DNA modifying ability seems to depend on physical or chemical characteristics, or both, of the fibre. PMID:2765416

Spectroscopic investigation of phenolic groups ionization in the vipoxin neurotoxic phospholipase A 2: comparison with the X-ray structure in the region of the tyrosyl residues

NASA Astrophysics Data System (ADS)

Georgieva, Dessislava Nikolova; Genov, Nicolay; Rajashankar, Kanagalaghatta R.; Aleksiev, Boris; Betzel, Christian

1998-12-01

The neurotoxin vipoxin is the major lethal component of the venom of Vipera ammodites meridionalis, the most toxic snake in Europe. It is a complex between a toxic phospholipase A 2 (PLA 2) and a non-toxic protein inhibitor (Inh). Tyrosyl residues are involved in the catalytic site (Tyr 52 and 73) and in the substrate binding (Tyr 22). Spectroscopic studies demonstrated differences in the ionization behavior of the various phenolic hydroxyl groups in the toxic PLA 2. The tyrosyl side chains of the enzyme can be classified into three groups: (a) three phenolic hydroxyls are accessible to the solvent and titrate normally, with a p Keff=10.45; (b) three residues are partially 'buried' and participate in hydrogen bonds with neighboring functional groups. They titrate anomalously with a p Keff=12.17; (c) two tyrosines with a p Keff=13.23 are deeply 'buried' in the hydrophobic interior of PLA 2. They became accessible to the titrating agent only after alkaline denaturation of the protein molecule. The spectroscopic data are related to the X-ray structure of the vipoxin PLA 2. The refined model was investigated in the region of the tyrosyl side chains. The accessible surface area of each tyrosyl residue and each phenolic hydroxyl group was calculated. A good correlation between the spectrophotometric and the crystallographic data was observed. The ionization behavior of the phenolic groups is explained by peculiarities of the protein three-dimensional structure and the participation of tyrosines in the catalytic site hydrogen bond network. Attempts are made to assign the calculated p Keff values to individual residues. The high degree of 'exposure' on the protein surface of Tyr 22 and 75 is probably important for their function as parts of the substrate binding and pharmacological sites.

Single-layer nanosheets with exceptionally high and anisotropic hydroxyl ion conductivity

PubMed Central

Sun, Pengzhan; Ma, Renzhi; Bai, Xueyin; Wang, Kunlin; Zhu, Hongwei; Sasaki, Takayoshi

2017-01-01

When the dimensionality of layered materials is reduced to the physical limit, an ultimate two-dimensional (2D) anisotropy and/or confinement effect may bring about extraordinary physical and chemical properties. Layered double hydroxides (LDHs), bearing abundant hydroxyl groups covalently bonded within 2D host layers, have been proposed as inorganic anion conductors. However, typical hydroxyl ion conductivities for bulk or lamellar LDHs, generally up to 10−3 S cm−1, are considered not high enough for practical applications. We show that single-layer LDH nanosheets exhibited exceptionally high in-plane conductivities approaching 10−1 S cm−1, which were the highest among anion conductors and comparable to proton conductivities in commercial proton exchange membranes (for example, Nafion). The in-plane conductivities were four to five orders of magnitude higher than the cross-plane or cross-membrane values of restacked LDH nanosheets. This 2D superionic transport characteristic might have great promises in a variety of applications including alkaline fuel cells and water electrolysis. PMID:28439551

A QM/MM study of the reaction mechanism of (R)-hydroxynitrile lyases from Arabidopsis thaliana (AtHNL).

PubMed

Zhu, Wenyou; Liu, Yongjun; Zhang, Rui

2015-01-01

Hydroxynitrile lyases (HNLs) catalyze the conversion of chiral cyanohydrins to hydrocyanic acid (HCN) and aldehyde or ketone. Hydroxynitrile lyase from Arabidopsis thaliana (AtHNL) is the first R-selective HNL enzyme containing an α/β-hydrolases fold. In this article, the catalytic mechanism of AtHNL was theoretically studied by using QM/MM approach based on the recently obtained crystal structure in 2012. Two computational models were constructed, and two possible reaction pathways were considered. In Path A, the calculation results indicate that the proton transfer from the hydroxyl group of cyanohydrin occurs firstly, and then the cleavage of C1-C2 bond and the rotation of the generated cyanide ion (CN(-)) follow, afterwards, CN(-) abstracts a proton from His236 via Ser81. The C1-C2 bond cleavage and the protonation of CN(-) correspond to comparable free energy barriers (12.1 vs. 12.2 kcal mol(-1)), suggesting that both of the two processes contribute a lot to rate-limiting. In Path B, the deprotonation of the hydroxyl group of cyanohydrin and the cleavage of C1-C2 bond take place in a concerted manner, which corresponds to the highest free energy barrier of 13.2 kcal mol(-1). The free energy barriers of Path A and B are very similar and basically agree well with the experimental value of HbHNL, a similar enzyme of AtHNL. Therefore, both of the two pathways are possible. In the reaction, the catalytic triad (His236, Ser81, and Asp208) acts as the general acid/base, and the generated CN(-) is stabilized by the hydroxyl group of Ser81 and the main-chain NH-groups of Ala13 and Phe82. © 2014 Wiley Periodicals, Inc.

Ester Cross-Link Profiling of the Cutin Polymer of Wild-Type and Cutin Synthase Tomato Mutants Highlights Different Mechanisms of Polymerization1

PubMed Central

Philippe, Glenn; Gaillard, Cédric; Petit, Johann; Geneix, Nathalie; Dalgalarrondo, Michèle; Bres, Cécile; Mauxion, Jean-Philippe; Franke, Rochus; Rothan, Christophe; Marion, Didier; Bakan, Bénédicte

2016-01-01

Cuticle function is closely related to the structure of the cutin polymer. However, the structure and formation of this hydrophobic polyester of glycerol and hydroxy/epoxy fatty acids has not been fully resolved. An apoplastic GDSL-lipase known as CUTIN SYNTHASE1 (CUS1) is required for cutin deposition in tomato (Solanum lycopersicum) fruit exocarp. In vitro, CUS1 catalyzes the self-transesterification of 2-monoacylglycerol of 9(10),16-dihydroxyhexadecanoic acid, the major tomato cutin monomer. This reaction releases glycerol and leads to the formation of oligomers with the secondary hydroxyl group remaining nonesterified. To check this mechanism in planta, a benzyl etherification of nonesterified hydroxyl groups of glycerol and hydroxy fatty acids was performed within cutin. Remarkably, in addition to a significant decrease in cutin deposition, mid-chain hydroxyl esterification of the dihydroxyhexadecanoic acid was affected in tomato RNA interference and ethyl methanesulfonate-cus1 mutants. Furthermore, in these mutants, the esterification of both sn-1,3 and sn-2 positions of glycerol was impacted, and their cutin contained a higher molar glycerol-to-dihydroxyhexadecanoic acid ratio. Therefore, in planta, CUS1 can catalyze the esterification of both primary and secondary alcohol groups of cutin monomers, and another enzymatic or nonenzymatic mechanism of polymerization may coexist with CUS1-catalyzed polymerization. This mechanism is poorly efficient with secondary alcohol groups and produces polyesters with lower molecular size. Confocal Raman imaging of benzyl etherified cutins showed that the polymerization is heterogenous at the fruit surface. Finally, by comparing tomato mutants either affected or not in cutin polymerization, we concluded that the level of cutin cross-linking had no significant impact on water permeance. PMID:26676255

Ester Cross-Link Profiling of the Cutin Polymer of Wild-Type and Cutin Synthase Tomato Mutants Highlights Different Mechanisms of Polymerization.

PubMed

Philippe, Glenn; Gaillard, Cédric; Petit, Johann; Geneix, Nathalie; Dalgalarrondo, Michèle; Bres, Cécile; Mauxion, Jean-Philippe; Franke, Rochus; Rothan, Christophe; Schreiber, Lukas; Marion, Didier; Bakan, Bénédicte

2016-02-01

Cuticle function is closely related to the structure of the cutin polymer. However, the structure and formation of this hydrophobic polyester of glycerol and hydroxy/epoxy fatty acids has not been fully resolved. An apoplastic GDSL-lipase known as CUTIN SYNTHASE1 (CUS1) is required for cutin deposition in tomato (Solanum lycopersicum) fruit exocarp. In vitro, CUS1 catalyzes the self-transesterification of 2-monoacylglycerol of 9(10),16-dihydroxyhexadecanoic acid, the major tomato cutin monomer. This reaction releases glycerol and leads to the formation of oligomers with the secondary hydroxyl group remaining nonesterified. To check this mechanism in planta, a benzyl etherification of nonesterified hydroxyl groups of glycerol and hydroxy fatty acids was performed within cutin. Remarkably, in addition to a significant decrease in cutin deposition, mid-chain hydroxyl esterification of the dihydroxyhexadecanoic acid was affected in tomato RNA interference and ethyl methanesulfonate-cus1 mutants. Furthermore, in these mutants, the esterification of both sn-1,3 and sn-2 positions of glycerol was impacted, and their cutin contained a higher molar glycerol-to-dihydroxyhexadecanoic acid ratio. Therefore, in planta, CUS1 can catalyze the esterification of both primary and secondary alcohol groups of cutin monomers, and another enzymatic or nonenzymatic mechanism of polymerization may coexist with CUS1-catalyzed polymerization. This mechanism is poorly efficient with secondary alcohol groups and produces polyesters with lower molecular size. Confocal Raman imaging of benzyl etherified cutins showed that the polymerization is heterogenous at the fruit surface. Finally, by comparing tomato mutants either affected or not in cutin polymerization, we concluded that the level of cutin cross-linking had no significant impact on water permeance. © 2016 American Society of Plant Biologists. All Rights Reserved.

First principles study of the atomic layer deposition of alumina by TMA-H2O-process.

PubMed

Weckman, Timo; Laasonen, Kari

2015-07-14

Atomic layer deposition (ALD) is a coating technology used to produce highly uniform thin films. Aluminiumoxide, Al2O3, is mainly deposited using trimethylaluminium (TMA) and water as precursors and is the most studied ALD-process to date. However, only few theoretical studies have been reported in the literature. The surface reaction mechanisms and energetics previously reported focus on a gibbsite-like surface model but a more realistic description of the surface can be achieved when the hydroxylation of the surface is taken into account using dissociatively adsorbed water molecules. The adsorbed water changes the structure of the surface and reaction energetics change considerably when compared to previously studied surface model. Here we have studied the TMA-H2O process using density functional theory on a hydroxylated alumina surface and reproduced the previous results for comparison. Mechanisms and energetics during both the TMA and the subsequent water pulse are presented. TMA is found to adsorb exothermically onto the surface. The reaction barriers for the ligand-exchange reactions between the TMA and the surface hydroxyl groups were found to be much lower compared to previously presented results. TMA dissociation on the surface is predicted to saturate at monomethylaluminium. Barriers for proton diffusion between surface sites are observed to be low. TMA adsorption was also found to be cooperative with the formation of methyl bridges between the adsorbants. The water pulse was studied using single water molecules reacting with the DMA and MMA surface species. Barriers for these reactions were found to reasonable in the process conditions. However, stabilizing interactions amongst water molecules were found to lower the reaction barriers and the dynamical nature of water is predicted to be of importance. It is expected that these calculations can only set an upper limit for the barriers during the water pulse.

Two-dimensional titanium carbonitrides and their hydroxylated derivatives: Structural, electronic properties and stability of MXenes Ti{sub 3}C{sub 2−x}N{sub x}(OH){sub 2} from DFTB calculations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Enyashin, A.N.; Ivanovskii, A.L., E-mail: ivanovskii@ihim.uran.ru

2013-11-15

The structural, electronic properties and stability of the new MXene compounds—two-dimensional pristine carbonitrides Ti{sub 3}C{sub 2−x}N{sub x} and their hydroxylated derivatives Ti{sub 3}C{sub 2−x}N{sub x}(OH){sub 2} are studied by means of DFTB calculations. The genesis of the properties is discussed in the sequence: binary MXenes Ti{sub 3}C{sub 2} (Ti{sub 3}N{sub 2})→hydroxylated forms Ti{sub 3}C{sub 2}(OH){sub 2} (Ti{sub 3}N{sub 2}(OH){sub 2})→pristine MXene Ti{sub 3}C{sub 2−x}N{sub x}→hydroxylated Ti{sub 3}C{sub 2−x}N{sub x}(OH){sub 2}. All examined materials are metallic-like. The most favorable type of OH-covering is presented by the occupation of the hollow sites between three neighboring carbon (nitrogen) atoms. Two-dimensional MXene carbonitrides withmore » random distribution of C and N atoms are found to be thermodynamically more favorable. - Graphical abstract: The side views of the optimized atomic structures of some examined hydroxylated derivatives of MXene Ti{sub 3}CN and their electronic band structures. Display Omitted - Highlights: • Very recently 2D titanium carbonitrides have been synthesized. • Structural, electronic properties and stability for these materials were evaluated. • The hydroxylated derivatives of 2D titanium carbonitrides are examined.« less

Energetic and electronic computation of the two-hydrogen atom donation process in catecholic and non-catecholic anthocyanidins.

PubMed

Ali, Hussein M; Ali, Isra H

2018-03-15

Antioxidant activity of anthocyanidins is greatly affected by the 3-hydroxyl group and/or a catecholic moiety. The two-hydrogen atom donation process is frequently used to explain the high antioxidant activity of polyphenolic compounds leading to the formation of stable diketones e.g. 1,2-quinones. Thermodynamic parameters, HOMO and spin density were computed to identify the favoured path, either through the 3-hydroxyl group or through the catecholic moiety in a series of catecholic and non-catecholic 3-oxy- (and deoxy)-anthocyanidins. DFT calculations showed that the donation process in non-catecholic anthocyanidins depended on the substituents on ring B. Anthocyanidins with 3',5'-diOMe groups showed donation through 3,4'-OH or, otherwise, through 3,5-OH groups. Catecholic 3-oxyanthocyanidins, on the other hand, showed donation through the 3,4'-OH path rather than the catecholic path (4',3'-path). The 3,4'-path was favoured by the formation of planar 3-radicals in the first step and the stabilization of 4'-radicals in the second step by H-bonding with the 3'-OH group. Copyright © 2017 Elsevier Ltd. All rights reserved.

Different routes to methanol: Inelastic neutron scattering spectroscopy of adsorbates on supported copper catalysts

DOE PAGES

Kandemir, Timur; Friedrich, Matthias; Parker, Stewart F.; ...

2016-04-14

We have investigated methanol synthesis with model supported copper catalysts, Cu/ZnO and Cu/MgO, using CO/H 2 and CO 2/H 2 as feedstocks. Under CO/H 2 both catalysts show chemisorbed methoxy as a stable intermediate, the Cu/MgO catalyst also shows hydroxyls on the support. Under CO 2/H 2 the catalysts behave differently, in that formate is also seen on the catalyst. For the Cu/ZnO catalyst hydroxyls are present on the metal whereas for the Cu/MgO hydroxyls are found on the support. Furthermore, these results are consistent with a recently published model for methanol synthesis and highlight the key role of ZnOmore » in the process.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Song, Jie; Viengkham, Malathong; Bertozzi, Carolyn R.

The controlled integration of organic and inorganic components confers natural bone with superior mechanical properties. Bone biogenesis is thought to occur by templated mineralization of hard apatite crystals by an elastic protein scaffold, a process we sought to emulate with synthetic biomimetic hydrogel polymers. Crosslinked polymethacrylamide and polymethacrylate hydrogels were functionalized with mineral-binding ligands and used to template the formation of hydroxyapatite. Strong adhesion between the organic and inorganic materials was achieved for hydrogels functionalized with either carboxylate or hydroxy ligands. The mineral-nucleating potential of hydroxyl groups identified here broadens the design parameters for synthetic bone-like composites and suggests amore » potential role for hydroxylated collagen proteins in bone mineralization.« less

Aromatic hydroxylation by cytochrome P450: model calculations of mechanism and substituent effects.

PubMed

Bathelt, Christine M; Ridder, Lars; Mulholland, Adrian J; Harvey, Jeremy N

2003-12-10

The mechanism and selectivity of aromatic hydroxylation by cytochrome P450 enzymes is explored using new B3LYP density functional theory computations. The calculations, using a realistic porphyrin model system, show that rate-determining addition of compound I to an aromatic carbon atom proceeds via a transition state with partial radical and cationic character. Reactivity is shown to depend strongly on ring substituents, with both electron-withdrawing and -donating groups strongly decreasing the addition barrier in the para position, and it is shown that the calculated barrier heights can be reproduced by a new dual-parameter equation based on radical and cationic Hammett sigma parameters.

Local structure of Iridium organometallic catalysts covalently bonded to carbon nanotubes.

NASA Astrophysics Data System (ADS)

Blasco, J.; Cuartero, V.; Subías, G.; Jiménez, M. V.; Pérez-Torrente, J. J.; Oro, L. A.; Blanco, M.; Álvarez, P.; Blanco, C.; Menéndez, R.

2016-05-01

Hybrid catalysts based on Iridium N-heterocyclic carbenes anchored to carbon nanotubes (CNT) have been studied by XAFS spectroscopy. Oxidation of CNT yields a large amount of functional groups, mainly hydroxyl groups at the walls and carboxylic groups at the tips, defects and edges. Different kinds of esterification reactions were performed to functionalize oxidized CNT with imidazolium salts. Then, the resulting products were reacted with an Ir organometallic compound to form hybrid catalysts efficient in hydrogen transfer processes. XANES spectroscopy agree with the presence of Ir(I) in these catalysts and the EXAFS spectra detected differences in the local structure of Ir atoms between the initial Ir organometallic compound and the Ir complexes anchored to the CNT. Our results confirm that the halide atom, present in the Ir precursor, was replaced by oxygen from -OH groups at the CNT wall in the first coordination shell of Ir. The lability of this group accounts for the good recyclability and the good efficiency shown by these hybrid catalysts.

Solar Insolation Effect on the Local Distribution of Lunar Hydroxyl

NASA Astrophysics Data System (ADS)

Kim, Suyeon; Yi, Yu; Hong, Ik-Seon; Sohn, Jongdae

2018-03-01

Moon mineralogy mapper (M3)'s work proved that the moon is not completely dry but has some hydroxyl/water. M3's data confirmed that the amount of hydroxyl on the lunar surface is inversely related to the measured signal brightness, suggesting the lunar surface is sensitive to temperature by solar insolation. We tested the effect of solar insolation on the local distribution of hydroxyl by using M3 data, and we found that most craters had more hydroxyl in shade areas than in sunlit areas. This means that the local distribution of hydroxyl is absolutely influenced by the amount of sunshine. We investigated the factors affecting differences in hydroxyl; we found that the higher the latitude, the larger the difference during daytime. We also measured the pyroxene content and found that pyroxene affects the amount of hydroxyl, but it does not affect the difference in hydroxyl between sunlit and shaded areas. Therefore, we confirmed that solar insolation plays a significant role in the local distribution of hydroxyl, regardless of surface composition.

Possible involvement of G-proteins and cAMP in the induction of progesterone hydroxylating enzyme system in the vascular wilt fungus Fusarium oxysporum.

PubMed

Poli, Anna; Di Pietro, Antonio; Zigon, Dusan; Lenasi, Helena

2009-02-01

Fungi present the ability to hydroxylate steroids. In some filamentous fungi, progesterone induces an enzyme system which converts the compound into a less toxic hydroxylated product. We investigated the progesterone response in the vascular wilt pathogen Fusarium oxysporum, using mass spectrometry and high performance liquid chromatography (HPLC). Progesterone was mainly transformed into 15alpha-hydroxyprogesterone, which was found predominantly in the extracellular medium. The role of two conserved fungal signaling cascades in the induction of the progesterone-transforming enzyme system was studied, using knockout mutants lacking the mitogen-activated protein kinase Fmk1 or the heterotrimeric G-protein beta subunit Fgb1 functioning upstream of the cyclic adenosine monophosphate (cAMP) pathway. No steroid hydroxylation was induced in the Deltafgb1 strain, suggesting a role for the G-protein beta subunit in progesterone signaling. Exogenous cAMP restored the induction of progesterone-transforming activity in the Deltafgb1 strain, suggesting that steroid signaling in F. oxysporum is mediated by the cAMP-PKA pathway.

Laser-saturated fluorescence measurements in laminar sooting diffusion flames

NASA Technical Reports Server (NTRS)

Wey, Changlie

1993-01-01

The hydroxyl radical is known to be one of the most important intermediate species in the combustion processes. The hydroxyl radical has also been considered a dominant oxidizer of soot particles in flames. In this investigation the hydroxyl concentration profiles in sooting diffusion flames were measured by the laser-saturated fluorescence (LSF) method. The temperature distributions in the flames were measured by the two-line LSF technique and by thermocouple. In the sooting region the OH fluorescence was too weak to make accurate temperature measurements. The hydroxyl fluorescence profiles for all four flames presented herein show that the OH fluorescence intensities peaked near the flame front. The OH fluorescence intensity dropped sharply toward the dark region of the flame and continued declining to the sooting region. The OH fluorescence profiles also indicate that the OH fluorescence decreased with increasing height in the flames for all flames investigated. Varying the oxidizer composition resulted in a corresponding variation in the maximum OH concentration and the flame temperature. Furthermore, it appears that the maximum OH concentration for each flame increased with increasing flame temperature.

CYP2J2 and CYP2C19 Are the Major Enzymes Responsible for Metabolism of Albendazole and Fenbendazole in Human Liver Microsomes and Recombinant P450 Assay Systems

PubMed Central

Wu, Zhexue; Lee, Doohyun; Joo, Jeongmin; Shin, Jung-Hoon; Kang, Wonku; Oh, Sangtaek; Lee, Do Yup; Lee, Su-Jun; Yea, Sung Su; Lee, Hye Suk

2013-01-01

Albendazole and fenbendazole are broad-spectrum anthelmintics that undergo extensive metabolism to form hydroxyl and sulfoxide metabolites. Although CYP3A and flavin-containing monooxygenase have been implicated in sulfoxide metabolite formation, the enzymes responsible for hydroxyl metabolite formation have not been identified. In this study, we used human liver microsomes and recombinant cytochrome P450s (P450s) to characterize the enzymes involved in the formation of hydroxyalbendazole and hydroxyfenbendazole from albendazole and fenbendazole, respectively. Of the 10 recombinant P450s, CYP2J2 and/or CYP2C19 was the predominant enzyme catalyzing the hydroxylation of albendazole and fenbendazole. Albendazole hydroxylation to hydroxyalbendazole is primarily mediated by CYP2J2 (0.34 μl/min/pmol P450, which is a rate 3.9- and 8.1-fold higher than the rates for CYP2C19 and CYP2E1, respectively), whereas CYP2C19 and CYP2J2 contributed to the formation of hydroxyfenbendazole from fenbendazole (2.68 and 1.94 μl/min/pmol P450 for CYP2C19 and CYP2J2, respectively, which are rates 11.7- and 8.4-fold higher than the rate for CYP2D6). Correlation analysis between the known P450 enzyme activities and the rate of hydroxyalbendazole and hydroxyfenbendazole formation in samples from 14 human liver microsomes showed that albendazole hydroxylation correlates with CYP2J2 activity and fenbendazole hydroxylation correlates with CYP2C19 and CYP2J2 activities. These findings were supported by a P450 isoform-selective inhibition study in human liver microsomes. In conclusion, our data for the first time suggest that albendazole hydroxylation is primarily catalyzed by CYP2J2, whereas fenbendazole hydroxylation is preferentially catalyzed by CYP2C19 and CYP2J2. The present data will be useful in understanding the pharmacokinetics and drug interactions of albendazole and fenbendazole in vivo. PMID:23959307

CYP2J2 and CYP2C19 are the major enzymes responsible for metabolism of albendazole and fenbendazole in human liver microsomes and recombinant P450 assay systems.

PubMed

Wu, Zhexue; Lee, Doohyun; Joo, Jeongmin; Shin, Jung-Hoon; Kang, Wonku; Oh, Sangtaek; Lee, Do Yup; Lee, Su-Jun; Yea, Sung Su; Lee, Hye Suk; Lee, Taeho; Liu, Kwang-Hyeon

2013-11-01

Albendazole and fenbendazole are broad-spectrum anthelmintics that undergo extensive metabolism to form hydroxyl and sulfoxide metabolites. Although CYP3A and flavin-containing monooxygenase have been implicated in sulfoxide metabolite formation, the enzymes responsible for hydroxyl metabolite formation have not been identified. In this study, we used human liver microsomes and recombinant cytochrome P450s (P450s) to characterize the enzymes involved in the formation of hydroxyalbendazole and hydroxyfenbendazole from albendazole and fenbendazole, respectively. Of the 10 recombinant P450s, CYP2J2 and/or CYP2C19 was the predominant enzyme catalyzing the hydroxylation of albendazole and fenbendazole. Albendazole hydroxylation to hydroxyalbendazole is primarily mediated by CYP2J2 (0.34 μl/min/pmol P450, which is a rate 3.9- and 8.1-fold higher than the rates for CYP2C19 and CYP2E1, respectively), whereas CYP2C19 and CYP2J2 contributed to the formation of hydroxyfenbendazole from fenbendazole (2.68 and 1.94 μl/min/pmol P450 for CYP2C19 and CYP2J2, respectively, which are rates 11.7- and 8.4-fold higher than the rate for CYP2D6). Correlation analysis between the known P450 enzyme activities and the rate of hydroxyalbendazole and hydroxyfenbendazole formation in samples from 14 human liver microsomes showed that albendazole hydroxylation correlates with CYP2J2 activity and fenbendazole hydroxylation correlates with CYP2C19 and CYP2J2 activities. These findings were supported by a P450 isoform-selective inhibition study in human liver microsomes. In conclusion, our data for the first time suggest that albendazole hydroxylation is primarily catalyzed by CYP2J2, whereas fenbendazole hydroxylation is preferentially catalyzed by CYP2C19 and CYP2J2. The present data will be useful in understanding the pharmacokinetics and drug interactions of albendazole and fenbendazole in vivo.

Role of metal ions in catalysis by HIV integrase analyzed using a quantitative PCR disintegration assay.

PubMed

Diamond, Tracy L; Bushman, Frederic D

2006-01-01

Paired metal ions have been proposed to be central to the catalytic mechanisms of RNase H nucleases, bacterial transposases, Holliday junction resolvases, retroviral integrases and many other enzymes. Here we present a sensitive assay for DNA transesterification in which catalysis by human immunodeficiency virus-type 1 (HIV-1) integrase (IN) connects two DNA strands (disintegration reaction), allowing detection using quantitative PCR (qPCR). We present evidence suggesting that the three acidic residues of the IN active site function through metal binding using metal rescue. In this method, the catalytic acidic residues were each substituted with cysteines. Mn2+ binds tightly to the sulfur atoms of the cysteine residues, but Mg2+ does not. We found that Mn2+, but not Mg2+, could rescue catalysis of each cysteine-substituted enzyme, providing evidence for functionally important metal binding by all three residues. We also used the PCR-boosted assay to show that HIV-1 IN could carry out transesterification reactions involving DNA 5' hydroxyl groups as well as 3' hydroxyls as nucleophiles. Lastly, we show that Mn2+ by itself (i.e. without enzyme) can catalyze formation of a low level of PCR-amplifiable product under extreme conditions, allowing us to estimate the rate enhancement due to the IN-protein scaffold as at least 60 million-fold.

Role of metal ions in catalysis by HIV integrase analyzed using a quantitative PCR disintegration assay

PubMed Central

Diamond, Tracy L.; Bushman, Frederic D.

2006-01-01

Paired metal ions have been proposed to be central to the catalytic mechanisms of RNase H nucleases, bacterial transposases, Holliday junction resolvases, retroviral integrases and many other enzymes. Here we present a sensitive assay for DNA transesterification in which catalysis by human immunodeficiency virus-type 1 (HIV-1) integrase (IN) connects two DNA strands (disintegration reaction), allowing detection using quantitative PCR (qPCR). We present evidence suggesting that the three acidic residues of the IN active site function through metal binding using metal rescue. In this method, the catalytic acidic residues were each substituted with cysteines. Mn2+ binds tightly to the sulfur atoms of the cysteine residues, but Mg2+ does not. We found that Mn2+, but not Mg2+, could rescue catalysis of each cysteine-substituted enzyme, providing evidence for functionally important metal binding by all three residues. We also used the PCR-boosted assay to show that HIV-1 IN could carry out transesterification reactions involving DNA 5′ hydroxyl groups as well as 3′ hydroxyls as nucleophiles. Lastly, we show that Mn2+ by itself (i.e. without enzyme) can catalyze formation of a low level of PCR-amplifiable product under extreme conditions, allowing us to estimate the rate enhancement due to the IN-protein scaffold as at least 60 million-fold. PMID:17085478

Novel 20(S)-sulfonylamidine derivatives of camptothecin and the use thereof as a potent antitumor agent: a patent evaluation of WO2015048365 (A1).

PubMed

Beretta, Giovanni Luca; Zaffaroni, Nadia; Varchi, Greta

2016-05-01

A series of camptothecin (CPT) derivatives featuring acyl-esterification of the 20(S)-hydroxyl group with a residue containing a sulfonylamidine moiety is synthesized via a Cu catalyzed three-component reaction. The compounds show remarkable cytotoxicity against a panel of tumor cells, including a cell line exhibiting Multi-Drug Resistant (MDR) phenotype. The patent develops 9a, the best derivative of the series, that i) selectively poisons DNA Topoisomerase I (TopoI); ii) induces cell-cycle S-phase arrest with activation of the DNA damage response pathway and apoptosis induction and iii) shows considerable in vivo antitumor potency. We envision that the peculiar modification of the 20(S)-hydroxyl group of CPT with a sulfonylamidine residue will play a continuing role in affording new TopoI poison drug candidates for therapeutic applications.

Progesterone biotransformation by plant cell suspension cultures.

PubMed Central

Yagen, B; Gallili, G E; Mateles, R I

1978-01-01

Progesterone was converted to 5alpha-pregnane-3alpha-ol-20-one, delta4-pregnene-20alpha-ol-3-one, delta4-pregnene-14alpha-ol-3,20-dione, delta4-pregnene-7beta,14alpha-diol-3,20-dione, and delta4-pregnene-6beta,11alpha-diol-3,20-dione by cell cultures of Lycopersicon esculentum. Cell cultures of Capsicum frutescens (green) metabolized progesterone to delta4-pregnene-20alpha-ol-3-one in very high yield, and Vinca rosea yielded delta4-pregnene-20beta-ol-3-one and delta4-pregnene-14alpha-ol-3,20-dione. A stereospecific reduction of the keto groups and a double bond and stereospecific introduction of hydroxyl groups at the 6, 11, and 14 positions have been observed. The mono- and dihydroxylated progesterones have not previously been reported as metabolic products of progesterone by plant cell systems and represent de novo hydroxylation of a nonglycosylated steroid. PMID:697360

Triphenylphosphine-based functional porous polymer as an efficient heterogeneous catalyst for the synthesis of cyclic carbonates from CO2

NASA Astrophysics Data System (ADS)

Wu, Siduo; Teng, Chao; Cai, Sheng; Jiang, Biwang; Wang, Yong; Meng, Hong; Tao, Huchun

2017-11-01

A novel triphenylphosphine-based porous polymer (TPDB) with a high Brunauer-Emmett-Teller (BET) surface area was synthesized through Friedel-Crafts alkylation of triphenylphosphine and α-dibromo- p-xylene. Then, the functional hydroxyl groups were successfully grafted onto the polymer framework by post modification of TPDB with 3-bromo-1-propanol (BP) and triethanolamine (TEA). The resulting sample TPDB-BP-TEA was characterized by various techniques such as FT-IR, TG, SEM, EDS mapping, ICP-MS, and N2 adsorption-desorption. This new polymer was tested as the catalyst in the solvent-free cycloaddition reaction of CO2 with epoxides, which exhibited excellent performance, with high yield, selectivity, and stable recyclability for several catalytic cycles. The comparison experiment results demonstrate that the bromide ions and hydroxyl groups, as well as high surface area, are key factors in improving the catalytic activity of this new catalyst.

Preparation and Characterization of ZnO Nanoparticles Supported on Amorphous SiO2

PubMed Central

Chen, Ying; Ding, Hao; Sun, Sijia

2017-01-01

In order to reduce the primary particle size of zinc oxide (ZnO) and eliminate the agglomeration phenomenon to form a monodisperse state, Zn2+ was loaded on the surface of amorphous silica (SiO2) by the hydrogen bond association between hydroxyl groups in the hydrothermal process. After calcining the precursors, dehydration condensation among hydroxyl groups occurred and ZnO nanoparticles supported on amorphous SiO2 (ZnO–SiO2) were prepared. Furthermore, the SEM and TEM observations showed that ZnO nanoparticles with a particle size of 3–8 nm were uniformly and dispersedly loaded on the surface of amorphous SiO2. Compared with pure ZnO, ZnO–SiO2 showed a much better antibacterial performance in the minimum inhibitory concentration (MIC) test and the antibacterial properties of the paint adding ZnO–SiO2 composite. PMID:28796157

Intercalation of paracetamol into the hydrotalcite-like host

NASA Astrophysics Data System (ADS)

Kovanda, František; Maryšková, Zuzana; Kovář, Petr

2011-12-01

Hydrotalcite-like compounds are often used as host structures for intercalation of various anionic species. The product intercalated with the nonionic, water-soluble pharmaceuticals paracetamol, N-(4-hydroxyphenyl)acetamide, was prepared by rehydration of the Mg-Al mixed oxide obtained by calcination of hydrotalcite-like precursor at 500 °C. The successful intercalation of paracetamol molecules into the interlayer space was confirmed by powder X-ray diffraction and infrared spectroscopy measurements. Molecular simulations showed that the phenolic hydroxyl groups of paracetamol interact with hydroxide sheets of the host via the hydroxyl groups of the positively charged sites of Al-containing octahedra; the interlayer water molecules are located mostly near the hydroxide sheets. The arrangement of paracetamol molecules in the interlayer is rather disordered and interactions between neighboring molecules cause their tilting towards the hydroxide sheets. Dissolution tests in various media showed slower release of paracetamol intercalated in the hydrotalcite-like host in comparison with tablets containing the powdered pharmaceuticals.

Extraction of agar from Gelidium sesquipedale (Rhodopyta) and surface characterization of agar based films.

PubMed

Guerrero, P; Etxabide, A; Leceta, I; Peñalba, M; de la Caba, K

2014-01-01

The chemical structure of the agar obtained from Gelidium sesquipedale (Rhodophyta) has been determined by (13)C nuclear magnetic resonance ((13)C NMR) and Fourier transform infrared spectroscopy (FTIR). Agar (AG) films with different amounts of soy protein isolate (SPI) were prepared using a thermo-moulding method, and transparent and hydrophobic films were obtained and characterized. FTIR analysis provided a detailed description of the binding groups present in the films, such as carboxylic, hydroxyl and sulfonate groups, while the surface composition was examined using X-ray photoelectron spectroscopy (XPS). The changes observed by FTIR and XPS spectra suggested interactions between functional groups of agar and SPI. This is a novel approach to the characterization of agar-based films and provides knowledge about the compatibility of agar and soy protein for further investigation of the functional properties of biodegradable films based on these biopolymers. Copyright © 2013 Elsevier Ltd. All rights reserved.

Cultivating Fluorescent Flowers with Highly Luminescent Carbon Dots Fabricated by a Double Passivation Method.

PubMed

Han, Shuai; Chang, Tao; Zhao, Haiping; Du, Huanhuan; Liu, Shan; Wu, Baoshuang; Qin, Shenjun

2017-07-07

In this work, we present the fabrication of highly luminescent carbon dots (CDs) by a double passivation method with the assistance of Ca(OH)₂. In the reaction process, Ca 2+ protects the active functional groups from overconsumption during dehydration and carbonization, and the electron-withdrawing groups on the CD surface are converted to electron-donating groups by the hydroxyl ions. As a result, the fluorescence quantum yield of the CDs was found to increase with increasing Ca(OH)₂ content in the reaction process. A blue-shift optical spectrum of the CDs was also found with increasing Ca(OH)₂ content, which could be attributed to the increasing of the energy gaps for the CDs. The highly photoluminescent CDs obtained (quantum yield: 86%) were used to cultivate fluorescent carnations by a water culture method, while the results of fluorescence microscopy analysis indicated that the CDs had entered the plant tissue structure.

JILA Science | Exploring the frontiers of physics

Science.gov Websites

group are lighting up dark excitons. Specifically, the Raschke group developed a method to observe dark into a highly reactive hydroxyl radical (OH). And when CO and OH meet, one byproduct is carbon dioxide one of the nation's leading research institutes in the physical sciences. Learn more about JILA -->

Aldehyde-containing urea-absorbing polysaccharides

NASA Technical Reports Server (NTRS)

Mueller, W. A.; Hsu, G. C.; Marsh, H. E., Jr. (Inventor)

1977-01-01

A novel aldehyde containing polymer (ACP) is prepared by reaction of a polysaccharide with periodate to introduce aldehyde groups onto the C2 - C3 carbon atoms. By introduction of ether and ester groups onto the pendant primary hydroxyl solubility characteristics are modified. The ACP is utilized to absorb nitrogen bases such as urea in vitro or in vivo.

Chemical Modification of Soy Flour Protein and its Properties

Treesearch

Yuzhi Xu; Chunpeng Wang; Fuxiang Chu; Charles R. Frihart; Linda F. Lorenz; Nicole M. Stark

2012-01-01

This work is to examine ways to chemically modify soy proteins flours and analyze the results and determine the adhesive performance. Reaction with acetic anhydride converts amine and hydroxyl groups to amides and esters, respectively that are less polar and can make the adhesive more water resistant.The succinic anhydride reacts with these same groups but the products...

In Situ Grafting of Hyperbranched Poly(Etherketone)s onto Multiwalled Carbon Nanotubes Via A3 + B2 Approach (Preprint)

DTIC Science & Technology

2007-04-01

MWNTs.20 These defects would provide sites for the electrophilic substitution reaction. In our previous work, FT-IR had been used to characterize the...various surface functionalities.22 In this study, MWNTs containing polar surface groups such as amino-, hydroxyl-, and fluorine groups displayed similar

Crystallization and preliminary X-ray crystallographic analysis of YfcM: an important factor for EF-P hydroxylation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kobayashi, Kan; RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198; Suzuki, Takehiro

2014-08-27

E. coli YfcM was expressed, purified and crystallized. Crystals of YfcM were obtained by the in situ proteolysis crystallization method. Using these crystals, an X-ray diffraction data set was collected at 1.45 Å resolution. Elongation factor P (EF-P) plays an essential role in the translation of polyproline-containing proteins in bacteria. It becomes functional by the post-translational modification of its highly conserved lysine residue. It is first β-lysylated by PoxA and then hydroxylated by YfcM. In this work, the YfcM protein from Escherichia coli was overexpressed, purified and crystallized. The crystal of YfcM was obtained by the in situ proteolysis crystallizationmore » method and diffracted X-rays to 1.45 Å resolution. It belonged to space group C2, with unit-cell parameters a = 124.4, b = 37.0, c = 37.6 Å, β = 101.2°. The calculated Matthews coefficient (V{sub M}) of the crystal was 1.91 Å{sup 3} Da{sup −1}, indicating that one YfcM molecule is present in the asymmetric unit with a solvent content of 35.7%.« less

Phosphate-Linked Silibinin Dimers (PLSd): New Promising Modified Metabolites.

PubMed

Romanucci, Valeria; Gravante, Raffaele; Cimafonte, Martina; Marino, Cinzia Di; Mailhot, Gilles; Brigante, Marcello; Zarrelli, Armando; Fabio, Giovanni Di

2017-08-11

By exploiting the regioselective protection of the hydroxyl groups of silibinin along with the well-known phosphoramidite chemistry, we have developed an efficient strategy for the synthesis of new silibinin-modified species, which we have named Phosphate-Linked Silibinin Dimers (PLSd), in which the monomer units are linked by phosphodiester bonds. The antioxidant abilities of the new PLSd were estimated on HepG2 cells using DPPH free radical scavenging and xanthine/xanthine oxidase assays. The new phosphate-metabolites showed a higher anti-oxidant activity than the silibinin, as well as very low toxicity. The ability to scavenge reactive oxygen species (ROS) such as singlet oxygen () and hydroxyl radical () reveals that the two dimers are able to scavenge about two times more effectively than silibinin. Finally, solubility studies have shown that the PLSd present good water solubility (more than 20 mg·L -1 ) under circumneutral pH values, whereas the silibinin was found to be very poorly soluble (less than 0.4 mg·L -1 ) and not stable under alkaline conditions. Together, the above promising results warrant further investigation of the future potential of the PLSd as anti-oxidant metabolites within the large synthetic polyphenols field.

Investigating Hydroxyl at Asteroid 951 Gaspra

NASA Astrophysics Data System (ADS)

Granahan, James C.

2015-11-01

Recent investigations [Granahan, 2011; 2014] of Galileo Near Infrared Mapping Spectrometer (NIMS) observations of asteroid 951 Gaspra have detected an infrared absorption feature near 2.8 micrometers. These were detected in NIMS data acquired by the Galileo spacecraft on October 29, 1991 at wavelengths ranging from 0.7 - 5.2 micrometers [Carlson et al., 1992]. This abstract presents a summary of the investigation to identify the material creating the 2.8 micrometer spectral absorption feature. The current best match for the observed 951 Gaspra feature is the phyllosilicate bound hydroxyl signature present in a thermally desiccated QUE 99038 carbonaceous chondrite as measured by Takir et al. [2013].The 951 Gaspra absorption feature has been compared to a variety of hydroxyl bearing signatures. Many phyllosilicates, hydroxyl bearing minerals, have absorption minima at different positions (2.7 or 2.85 micrometers). It also differs from similar absorptions in a potential R chondrite analog, LAP 04840. The spectra LAP 04840 has a 2.7 micrometer feature due to biotite and a 2.9 micrometer feature due to adsorbed water [Klima et al., 2007]. 2.8 micrometer absorption minima have been found for adsorbed hydroxyl on the Moon [McCord et al., 2011] and various carbonaceous chondrites [Calvin and King, 1997; Takir et al., 2013]. The best match, with a minimum Euclidean distance difference to the 951 Gaspra feature, is found in the spectrum of QUE 99038 [Takir et al., 2013]. This spectrum is the product of an infrared measurement of a sample that had its adsorbed water baked off and removed in a vacuum chamber. The remaining hydroxyl in the sample belongs to a mixture of phyllosilicates dominated by the presence of cronstedtite.References: Calvin, W. M., and T. V. King (1997), Met. Planet. Sci., 32, 693-702. Carlson, R. W., et al. (1992), Bull. American Astro. Soc., 24, 932. Granahan, J. C. (2011), Icarus, 213, 265-272. Granahan, J. C. (2014), 45th LPSC, #1092. Klima, R., C. et al. (2007), 38th LPSC, #1710. McCord, T. B., et al. (2011), JGR, 116, E00G05. Takir, D., et al. (2013), Met. Planet. Sci., 48, 1618-1637.

Alpha-Hydroxylation of lignoceric and nervonic acids in the brain. Effects of altered thyroid function on postnatal development of the hydroxylase activity.

PubMed

Murad, S; Strycharz, G D; Kishimoto, Y

1976-09-10

Rat brain postnuclear preparations catalyzed the alpha-hydroxylation of nervonic acid with an apparent Km of 3 muM. Evidence has been presented which suggests that nervonic acid in the brain is hydroxylated by the same enzyme system which hydroxylates lignoceric acid. The hydroxylase activity in brains of normal (euthyroid) rats increased rapidly from a low in the period immediately following birth to a maximum at the 23rd day and then declined to a low level characteristic of the mature brain. Neonatal hypothyroidism retarded the development of the activity and shifted its peak to the 39th day after birth. Conversely, neonatal hyperthyroidism accelerated the entire developmental pattern and shifted the peak to the 16th day after birth. The hydroxylase activity in mouse brain was also increased by thyroid hormone administration from the 13th through the 18th day after birth. Unlike normal mice, the low activity in jimpy mice was not affected by this treatment. It is concluded that thyroid hormones play an important role in the control of brain fatty acid alpha-hydroxylation. The stimulation of alpha-hydroxy fatty acid synthesis in response to hyperthyroidism during the early postnatal period may be one of the major effects of thyroid hormones in accelerating myelination of the central nervous system.

Methods for treating a liquid using draw solutions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wilson, Aaron D; Orme, Christopher J.

Draw solutions comprising at least one N-cyclicalkyl-cycloalkylamine and a secondary solvent. The N-cyclicalkyl-cycloalkylamine comprises the chemical structure: ##STR00001## wherein n is 0, 1, or 2, n' is 0, 1, or 2, and each of R.sup.1-R.sup.6 is independently selected from the group consisting of an alkyl group, an alkoxy group, an acetyl group, an aryl group, a hydrogen group, a hydroxyl group, and a phosphorus-containing group. Methods of treating a liquid using the draw solution are also disclosed.

Biodegradation of Trinitrotoluene (Alpha TNT) and Its Production Isomers

DTIC Science & Technology

1975-07-01

medium, suqgesting that some of the nitro groups may be released as nitrite. DO .ETn 1473 EDITION OF t NOV 6» IS OBSOLETE iMW- vr IJNWASS...nitrite in the medium and the formation of catechol, Tewfik and Evans (2) demonstrated the biodegradation of 3,5-dinitro-o- cresol via reduction of the 5... nitro group to an amino group which is then replaced by a hydroxyl group. After this the same series of reactions occur with the 3- nitro group

Metabolites of 5F-AKB-48, a synthetic cannabinoid receptor agonist, identified in human urine and liver microsomal preparations using liquid chromatography high-resolution mass spectrometry.

PubMed

Holm, Niels Bjerre; Pedersen, Anders Just; Dalsgaard, Petur Weihe; Linnet, Kristian

2015-03-01

New types of synthetic cannabinoid designer drugs are constantly introduced to the illicit drug market to circumvent legislation. Recently, N-​(1-Adamant​yl)-​1-​(5-​fluoropentyl)-​1H-​indazole-​3-​carboxamide (5F-AKB-48), also known as 5F-APINACA, was identified as an adulterant in herbal products. This compound deviates from earlier JHW-type synthetic cannabinoids by having an indazole ring connected to an adamantyl group via a carboxamide linkage. Synthetic cannabinoids are completely metabolized, and identification of the metabolites is thus crucial when using urine as the sample matrix. Using an authentic urine sample and high-resolution accurate-mass Fourier transform Orbitrap mass spectrometry, we identified 16 phase-I metabolites of 5F-AKB-48. The modifications included mono-, di-, and trihydroxylation on the adamantyl ring alone or in combination with hydroxylation on the N-fluoropentylindazole moiety, dealkylation of the N-fluoropentyl side chain, and oxidative loss of fluorine as well as combinations thereof. The results were compared to human liver microsomal (HLM) incubations, which predominantly showed time-dependent formation of mono-, di-, and trihydroxylated metabolites having the hydroxyl groups on the adamantyl ring. The results presented here may be used to select metabolites specific of 5F-AKB-48 for use in clinical and forensic screening. Copyright © 2014 John Wiley & Sons, Ltd.

Crystal structures of human cholinesterases in complex with huprine W and tacrine: elements of specificity for anti-Alzheimer's drugs targeting acetyl- and butyryl-cholinesterase.

PubMed

Nachon, Florian; Carletti, Eugénie; Ronco, Cyril; Trovaslet, Marie; Nicolet, Yvain; Jean, Ludovic; Renard, Pierre-Yves

2013-08-01

The multifunctional nature of Alzheimer's disease calls for MTDLs (multitarget-directed ligands) to act on different components of the pathology, like the cholinergic dysfunction and amyloid aggregation. Such MTDLs are usually on the basis of cholinesterase inhibitors (e.g. tacrine or huprine) coupled with another active molecule aimed at a different target. To aid in the design of these MTDLs, we report the crystal structures of hAChE (human acetylcholinesterase) in complex with FAS-2 (fasciculin 2) and a hydroxylated derivative of huprine (huprine W), and of hBChE (human butyrylcholinesterase) in complex with tacrine. Huprine W in hAChE and tacrine in hBChE reside in strikingly similar positions highlighting the conservation of key interactions, namely, π-π/cation-π interactions with Trp86 (Trp82), and hydrogen bonding with the main chain carbonyl of the catalytic histidine residue. Huprine W forms additional interactions with hAChE, which explains its superior affinity: the isoquinoline moiety is associated with a group of aromatic residues (Tyr337, Phe338 and Phe295 not present in hBChE) in addition to Trp86; the hydroxyl group is hydrogen bonded to both the catalytic serine residue and residues in the oxyanion hole; and the chlorine substituent is nested in a hydrophobic pocket interacting strongly with Trp439. There is no pocket in hBChE that is able to accommodate the chlorine substituent.

Recognition Tunneling of Canonical and Modified RNA Nucleotides for Their Identification with the Aid of Machine Learning.

PubMed

Im, JongOne; Sen, Suman; Lindsay, Stuart; Zhang, Peiming

2018-06-28

In the present study, we demonstrate a tunneling nanogap technique to identify individual RNA nucleotides, which can be used as a mechanism to read the nucleobases for direct sequencing of RNA in a solid-state nanopore. The tunneling nanogap is composed of two electrodes separated by a distance of <3 nm and functionalized with a recognition molecule. When a chemical entity is captured in the gap, it generates electron tunneling currents, a process we call recognition tunneling (RT). Using RT nanogaps created in a scanning tunneling microscope (STM), we acquired the electron tunneling signals for the canonical and two modified RNA nucleotides. To call the individual RNA nucleotides from the RT data, we adopted a machine learning algorithm, support vector machine (SVM), for the data analysis. Through the SVM, we were able to identify the individual RNA nucleotides and distinguish them from their DNA counterparts with reasonably high accuracy. Since each RNA nucleoside contains a hydroxyl group at the 2'-position of its sugar ring in an RNA strand, it allows for the formation of a tunneling junction at a larger nanogap compared to the DNA nucleoside in a DNA strand, which lacks the 2' hydroxyl group. It also proves advantageous for the manufacture of RT devices. This study is a proof-of-principle demonstration for the development of an RT nanopore device for directly sequencing single RNA molecules, including those bearing modifications.

Antioxidant Chemistry of Graphene-Based Materials and its Role in Oxidation Protection Technology

PubMed Central

Qiu, Yang; Wang, Zhongying; Owens, Alisa C.E.; Kulaots, Indrek; Chen, Yantao; Kane, Agnes B.; Hurt, Robert H.

2015-01-01

Two-dimensional nanomaterials have potential as a new class of antioxidants that combine physical barrier function with ultrahigh surface area for free radical scavenging. This work presents the first measurements of the chemical reactivities of graphene-based materials toward a set of model free radicals and reactive oxygen species using electron paramagnetic resonance spectroscopy (EPR) and sacrificial dye protection assays. Graphene-based materials are shown to protect a variety of molecular targets from oxidation by these species, and to be highly effective as hydroxyl-radical scavengers. When hydroxyl radical is produced photolytically, the overall antioxidant effect is a combination of preventative antioxidant activity (UV absorption) and ·OH radical scavenging. Few-layer graphene is more active than monolayer graphene oxide, despite its lower surface area, which indicates that the primary scavenging sites are associated with the sp2-carbon network rather than oxygen-containing functional groups. To explain this trend, we propose that GO is a weak hydrogen donor, due to the non-phenolic nature of most OH groups on GO, which reside at basal sp3-carbon sites that do not allow for radical resonance stabilization following hydrogen donation. As an example application of graphene antioxidant behavior, we show that encapsulation of TiO2 nanoparticles in graphene nanosacks reduces undesired photo-oxidative damage to nearby organic target molecules, which suggests graphene encapsulation as a new approach to managing adverse environmental or health impacts of redox-active nanomaterials. PMID:25157875

Determination of hydroxylated fatty acids from the biopolymer of tomato cutin and their fate during incubation in soil.

PubMed

Hauff, Simone; Chefetz, Benny; Shechter, Michal; Vetter, Walter

2010-01-01

The plant cuticle is a thin, predominantly lipid layer that covers all primary aerial surfaces of vascular plants. The monomeric building blocks of the cutin biopolymer are mainly ω-hydroxy fatty acids. Analysis of ω-hydroxy fatty acids from cutin isolated from tomato fruits at different stages of decomposition in soil. Different derivatives and mass spectrometric techniques were used for peak identification and evaluation. Preparation of purified cutin involving dewaxing and HCl treatment. Incubation of purified cutin for 20 months in soil. Pentafluorobenzoyl derivatives were used for GC/MS operated in the electron capture negative ion (ECNI) mode and trimethylsilyl ethers for GC/MS operated in the electron ionisation (EI) mode for analysis of ω-hydroxy fatty acids. Six ω-hydroxy fatty acids were detected in the purified cutin, three of which were identified as degradation products of 9,16-dihydroxyhexadecanoic acid as a consequence of the HCl treatment involved in the purification step. Incubation of the isolated cutin in soil was accompanied with decrease in concentration of all hydroxyl fatty acids. We produced evidence that the HCl treatment only affected free hydroxyl groups and thus could be used for proportioning free and bound OH-groups on cutin fatty acids. The method enabled a direct quantification of the ω-hydroxy fatty acids throughout the incubation phase. Copyright © 2010 John Wiley & Sons, Ltd.

Spectral and computational features of the binding between riparins and human serum albumin

NASA Astrophysics Data System (ADS)

Camargo, Cintia Ramos; Caruso, Ícaro Putinhon; Gutierrez, Stanley Juan Chavez; Fossey, Marcelo Andres; Filho, José Maria Barbosa; Cornélio, Marinônio Lopes

2018-02-01

The green Brazilian bay leaf, a spice much prized in local cuisine (Aniba riparia, Lauraceae), contains chemical compounds presenting benzoyl-derivatives named riparins, which have anti-inflammatory, antimicrobial and anxiolytic properties. However, it is unclear what kind of interaction riparins perform with any molecular target. As a profitable target, human serum albumin (HSA) is one of the principal extracellular proteins, with an exceptional capacity to interact with several molecules, and it also plays a crucial role in the transport, distribution, and metabolism of a wide variety of endogenous and exogenous ligands. To outline the HSA-riparin interaction mechanism, spectroscopy and computational methods were synergistically applied. An evaluation through fluorescence spectroscopy showed that the emission, attributed to Trp 214, at 346 nm decreased with titrations of riparins. A static quenching mechanism was observed in the binding of riparins to HSA. Fluorescence experiments performed at 298, 308 and 318 K made it possible to conduct thermodynamic analysis indicating a spontaneous reaction in the complex formation (ΔG < 0). The enthalpy-entropy balance experiment with a molecular modeling calculation revealed that hydrophobic, hydrogen bond and non-specific interactions are present for riparin I-III with HSA. The set of results from fractional fluorescence changes obtained through Schatchard was inconclusive in establishing what kind of cooperativity is present in the interaction. To shed light upon the HSA-riparins complex, Hill's approach was utilized to distinguish the index of affinity and the binding constant. A correspondence between the molecular structures of riparins, due to the presence of the hydroxyl group in the B-ring, with thermodynamic parameters and index of affinity were observed. Riparin III performs an intramolecular hydrogen bond, which affects the Hill coefficient and the binding constant. Therefore, the presence of hydroxyl groups is capable of modulating the interaction between riparins and HSA. Site marker competitive experiments indicated Site I as being the most suitable, and the molecular modeling tools reinforced the experimental results detailing the participation of residues.

Sweet Structural Signatures Unveiled in Ketohexoses.

PubMed

Bermúdez, Celina; Peña, Isabel; Mata, Santiago; Alonso, José L

2016-11-14

The conformational behaviour of naturally occurring ketohexoses has been revealed in a supersonic expansion by Fourier transform microwave spectroscopy coupled with a laser ablation source. Three, two and one conformers of d-tagatose, d-psicose and l-sorbose, respectively, have been identified by their rotational constants extracted from the analysis of the spectra. Singular structural signatures involving the hydroxyl groups OH (1) and OH (2) have been disentangled from the intricate intramolecular hydrogen bond networks stabilising the most abundant conformers. The present results place the old Shallenberger and Kier sweetness theories on a firmer footing. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Topological defect clustering and plastic deformation mechanisms in functionalized graphene

NASA Astrophysics Data System (ADS)

Nunes, Ricardo; Araujo, Joice; Chacham, Helio

2011-03-01

We present ab initio results suggesting that strain plays a central role in the clustering of topological defects in strained and functionalized graphene models. We apply strain onto the topological-defect graphene networks from our previous work, and obtain topological-defect clustering patterns which are in excellent agreement with recent observations in samples of reduced graphene oxide. In our models, the graphene layer, containing an initial concentration of isolated topological defects, is covered by hydrogen or hydroxyl groups. Our results also suggest a rich variety of plastic deformation mechanism in functionalized graphene systems. We acknowledge support from the Brazilian agencies: CNPq, Fapemig, and INCT-Materiais de Carbono.

Determination of hydroxylated polycyclic aromatic hydrocarbons by HPLC-photoionization tandem mass spectrometry in wood smoke particles and soil samples.

PubMed

Avagyan, Rozanna; Nyström, Robin; Boman, Christoffer; Westerholm, Roger

2015-06-01

A simple and fast method for analysis of hydroxylated polycyclic aromatic hydrocarbons using pressurized liquid extraction and high performance liquid chromatography utilizing photoionization tandem mass spectrometry was developed. Simultaneous separation and determination of nine hydroxylated polycyclic aromatic hydrocarbons and two hydroxy biphenyls could be performed in negative mode with a run time of 12 min, including equilibration in 5 min. The calibration curves were in two concentration ranges; 1-50 ng/mL and 0.01-50 μg/mL, with coefficients of correlation R (2) > 0.997. The limits of detection and method quantification limits were in the range of 9-56 pg and 5-38 ng/g, respectively. A two-level full factorial experimental design was used for screening of conditions with the highest impact on the extraction. The extraction procedure was automated and suitable for a large number of samples. The extraction recoveries ranged from 70 to 102 % and the matrix effects were between 92 and 104 %. The overall method was demonstrated on wood smoke particles and soil samples with good analytical performance, and five OH-PAHs were determined in the concentration range of 0.19-210 μg/g. As far as we know, hydroxylated polycyclic aromatic hydrocarbons were determined in wood smoke and soil samples using photoionization mass spectrometry for the first time in this present study. Accordingly, this study shows that high performance liquid chromatography photoionization tandem mass spectrometry can be a good option for the determination of hydroxylated polycyclic aromatic hydrocarbons in complex environmental samples. Graphical Abstract The method developed in this study was used to determine hydroxylated polycyclic aromatic hydrocarbons in wood smoke and soil.

Coniferyl aldehyde 5-hydroxylation and methylation direct syringyl lignin biosynthesis in angiosperms

PubMed Central

Osakabe, Keishi; Tsao, Cheng Chung; Li, Laigeng; Popko, Jacqueline L.; Umezawa, Toshiaki; Carraway, Daniel T.; Smeltzer, Richard H.; Joshi, Chandrashekhar P.; Chiang, Vincent L.

1999-01-01

A central question in lignin biosynthesis is how guaiacyl intermediates are hydroxylated and methylated to the syringyl monolignol in angiosperms. To address this question, we cloned cDNAs encoding a cytochrome P450 monooxygenase (LsM88) and a caffeate O-methyltransferase (COMT) from sweetgum (Liquidambar styraciflua) xylem. Mass spectrometry-based functional analysis of LsM88 in yeast identified it as coniferyl aldehyde 5-hydroxylase (CAld5H). COMT expressed in Escherichia coli methylated 5-hydroxyconiferyl aldehyde to sinapyl aldehyde. Together, CAld5H and COMT converted coniferyl aldehyde to sinapyl aldehyde, suggesting a CAld5H/COMT-mediated pathway from guaiacyl to syringyl monolignol biosynthesis via coniferyl aldehyde that contrasts with the generally accepted route to sinapate via ferulate. Although the CAld5H/COMT enzyme system can mediate the biosynthesis of syringyl monolignol intermediates through either route, kcat/Km of CAld5H for coniferyl aldehyde was ≈140 times greater than that for ferulate. More significantly, when coniferyl aldehyde and ferulate were present together, coniferyl aldehyde was a noncompetitive inhibitor (Ki = 0.59 μM) of ferulate 5-hydroxylation, thereby eliminating the entire reaction sequence from ferulate to sinapate. In contrast, ferulate had no effect on coniferyl aldehyde 5-hydroxylation. 5-Hydroxylation also could not be detected for feruloyl-CoA or coniferyl alcohol. Therefore, in the presence of coniferyl aldehyde, ferulate 5-hydroxylation does not occur, and the syringyl monolignol can be synthesized only from coniferyl aldehyde. Endogenous coniferyl, 5-hydroxyconiferyl, and sinapyl aldehydes were detected, consistent with in vivo operation of the CAld5H/COMT pathway from coniferyl to sinapyl aldehydes via 5-hydroxyconiferyl aldehyde for syringyl monolignol biosynthesis. PMID:10430877

Hydroxyl radical mediates cisplatin-induced apoptosis in human hair follicle dermal papilla cells and keratinocytes through Bcl-2-dependent mechanism.

PubMed

Luanpitpong, Sudjit; Nimmannit, Ubonthip; Chanvorachote, Pithi; Leonard, Stephen S; Pongrakhananon, Varisa; Wang, Liying; Rojanasakul, Yon

2011-08-01

Induction of massive apoptosis of hair follicle cells by chemotherapy has been implicated in the pathogenesis of chemotherapy-induced alopecia (CIA), but the underlying mechanisms of regulation are not well understood. The present study investigated the apoptotic effect of cisplatin in human hair follicle dermal papilla cells and HaCaT keratinocytes, and determined the identity and role of specific reactive oxygen species (ROS) involved in the process. Treatment of the cells with cisplatin induced ROS generation and a parallel increase in caspase activation and apoptotic cell death. Inhibition of ROS generation by antioxidants inhibited the apoptotic effect of cisplatin, indicating the role of ROS in the process. Studies using specific ROS scavengers further showed that hydroxyl radical, but not hydrogen peroxide or superoxide anion, is the primary oxidative species responsible for the apoptotic effect of cisplatin. Electron spin resonance studies confirmed the formation of hydroxyl radicals induced by cisplatin. The mechanism by which hydroxyl radical mediates the apoptotic effect of cisplatin was shown to involve down-regulation of the anti-apoptotic protein Bcl-2 through ubiquitin-proteasomal degradation. Bcl-2 was also shown to have a negative regulatory role on hydroxyl radical. Together, our results indicate an essential role of hydroxyl radical in cisplatin-induced cell death of hair follicle cells through Bcl-2 regulation. Since CIA is a major side effect of cisplatin and many other chemotherapeutic agents with no known effective treatments, the knowledge gained from this study could be useful in the design of preventive treatment strategies for CIA through localized therapy without compromising the chemotherapy efficacy.

Lettuce Costunolide Synthase (CYP71BL2) and Its Homolog (CYP71BL1) from Sunflower Catalyze Distinct Regio- and Stereoselective Hydroxylations in Sesquiterpene Lactone Metabolism*

PubMed Central

Ikezawa, Nobuhiro; Göpfert, Jens Christian; Nguyen, Don Trinh; Kim, Soo-Un; O'Maille, Paul E.; Spring, Otmar; Ro, Dae-Kyun

2011-01-01

Sesquiterpene lactones (STLs) are terpenoid natural products possessing the γ-lactone, well known for their diverse biological and medicinal activities. The occurrence of STLs is sporadic in nature, but most STLs have been isolated from plants in the Asteraceae family. Despite the implication of the γ-lactone group in many reported bioactivities of STLs, the biosynthetic origins of the γ-lactone ring remains elusive. Germacrene A acid (GAA) has been suggested as a central precursor of diverse STLs. The regioselective (C6 or C8) and stereoselective (α or β) hydroxylation on a carbon of GAA adjacent to its carboxylic acid at C12 is responsible for the γ-lactone formation. Here, we report two cytochrome P450 monooxygenases (P450s) capable of catalyzing 6α- and 8β-hydroxylation of GAA from lettuce and sunflower, respectively. To identify these P450s, sunflower trichomes were isolated to generate a trichome-specific transcript library, from which 10 P450 clones were retrieved. Expression of these clones in a yeast strain metabolically engineered to synthesize substrate GAA identified a P450 catalyzing 8β-hydroxylation of GAA, but the STL was not formed by spontaneous lactonization. Subsequently, we identified the closest homolog of the GAA 8β-hydroxylase from lettuce and discovered 6α-hydroxylation of GAA by the recombinant enzyme. The resulting 6α-hydroxy-GAA spontaneously undergoes a lactonization to yield the simplest form of STL, costunolide. Furthermore, we demonstrate the milligram per liter scale de novo synthesis of costunolide using the lettuce P450 in an engineered yeast strain, an important advance that will enable exploitation of STLs. Evolution and homology models of these two P450s are discussed. PMID:21515683

Steroid hydroxylation by basidiomycete peroxygenases: a combined experimental and computational study.

PubMed

Babot, Esteban D; Del Río, José C; Cañellas, Marina; Sancho, Ferran; Lucas, Fátima; Guallar, Víctor; Kalum, Lisbeth; Lund, Henrik; Gröbe, Glenn; Scheibner, Katrin; Ullrich, René; Hofrichter, Martin; Martínez, Angel T; Gutiérrez, Ana

2015-06-15

The goal of this study is the selective oxyfunctionalization of steroids under mild and environmentally friendly conditions using fungal enzymes. With this purpose, peroxygenases from three basidiomycete species were tested for the hydroxylation of a variety of steroidal compounds, using H2O2 as the only cosubstrate. Two of them are wild-type enzymes from Agrocybe aegerita and Marasmius rotula, and the third one is a recombinant enzyme from Coprinopsis cinerea. The enzymatic reactions on free and esterified sterols, steroid hydrocarbons, and ketones were monitored by gas chromatography, and the products were identified by mass spectrometry. Hydroxylation at the side chain over the steroidal rings was preferred, with the 25-hydroxyderivatives predominating. Interestingly, antiviral and other biological activities of 25-hydroxycholesterol have been reported recently (M. Blanc et al., Immunity 38:106-118, 2013, http://dx.doi.org/10.1016/j.immuni.2012.11.004). However, hydroxylation in the ring moiety and terminal hydroxylation at the side chain also was observed in some steroids, the former favored by the absence of oxygenated groups at C-3 and by the presence of conjugated double bonds in the rings. To understand the yield and selectivity differences between the different steroids, a computational study was performed using Protein Energy Landscape Exploration (PELE) software for dynamic ligand diffusion. These simulations showed that the active-site geometry and hydrophobicity favors the entrance of the steroid side chain, while the entrance of the ring is energetically penalized. Also, a direct correlation between the conversion rate and the side chain entrance ratio could be established that explains the various reaction yields observed. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

Steroid Hydroxylation by Basidiomycete Peroxygenases: a Combined Experimental and Computational Study

PubMed Central

Babot, Esteban D.; del Río, José C.; Cañellas, Marina; Sancho, Ferran; Lucas, Fátima; Guallar, Víctor; Kalum, Lisbeth; Lund, Henrik; Gröbe, Glenn; Scheibner, Katrin; Ullrich, René; Hofrichter, Martin; Martínez, Angel T.

2015-01-01

The goal of this study is the selective oxyfunctionalization of steroids under mild and environmentally friendly conditions using fungal enzymes. With this purpose, peroxygenases from three basidiomycete species were tested for the hydroxylation of a variety of steroidal compounds, using H2O2 as the only cosubstrate. Two of them are wild-type enzymes from Agrocybe aegerita and Marasmius rotula, and the third one is a recombinant enzyme from Coprinopsis cinerea. The enzymatic reactions on free and esterified sterols, steroid hydrocarbons, and ketones were monitored by gas chromatography, and the products were identified by mass spectrometry. Hydroxylation at the side chain over the steroidal rings was preferred, with the 25-hydroxyderivatives predominating. Interestingly, antiviral and other biological activities of 25-hydroxycholesterol have been reported recently (M. Blanc et al., Immunity 38:106–118, 2013, http://dx.doi.org/10.1016/j.immuni.2012.11.004). However, hydroxylation in the ring moiety and terminal hydroxylation at the side chain also was observed in some steroids, the former favored by the absence of oxygenated groups at C-3 and by the presence of conjugated double bonds in the rings. To understand the yield and selectivity differences between the different steroids, a computational study was performed using Protein Energy Landscape Exploration (PELE) software for dynamic ligand diffusion. These simulations showed that the active-site geometry and hydrophobicity favors the entrance of the steroid side chain, while the entrance of the ring is energetically penalized. Also, a direct correlation between the conversion rate and the side chain entrance ratio could be established that explains the various reaction yields observed. PMID:25862224

Effect of drying temperatures on structural performance and photocatalytic activity of BiOCl synthesized by a soft chemical method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guang, Lu, E-mail: lu_g@163.com; Hui, Wang; Xuejun, Zou

2016-07-15

A group of BiOCl photocatalysts with different drying temperatures were prepared by a soft chemical method. The effects of drying temperatures on the crystalline phase, morphology, surface area and optical property of as-prepared samples were investigated in detail by XRD, SEM, N{sub 2} absorption–desorption and DRS. Moreover, their photocatalytic activities on the degradation of rhodamine B were evaluated under visible light irradiation. It was found that the sample dried at 120 °C had the best photocatalytic activity, which was mainly attributed to the highest exposing proportion of {001} facets correspond to BiOCl, largest BET and minimum bandgap. The degradation mechanismmore » was explored that superoxide radicals were mainly contributed to the degradation of chromophore, however, holes and hydroxyl were mainly contributed to the photo degradation. Moreover, holes and hydroxyl dominated the degradation of RhB. - Graphical abstract: Holes, hydroxyl and superoxide radicals can attribute to the degradation process but take different degradation pathways. Superoxide radicals mainly contribute to the degradation of chromophore, however, holes and hydroxyl mainly contribute to the photo degradation. Display Omitted - Highlights: • BiOCl nanosheets were prepared by a soft chemical method. • Effect of drying temperatures on as-prepared BiOCl samples was studied. • The highest removal efficiency of RhB was obtained over the sample dried at 120 °C.« less

Heterologous pathway assembly reveals molecular steps of fungal terreic acid biosynthesis.

PubMed

Kong, Chuixing; Huang, Hezhou; Xue, Ying; Liu, Yiqi; Peng, Qiangqiang; Liu, Qi; Xu, Qin; Zhu, Qiaoyun; Yin, Ying; Zhou, Xiangshan; Zhang, Yuanxing; Cai, Menghao

2018-02-01

Terreic acid is a potential anticancer drug as it inhibits Bruton's tyrosine kinase; however, its biosynthetic molecular steps remain unclear. In this work, the individual reactions of terreic acid biosynthesis were determined by stepwise pathway assembly in a heterologous host, Pichia pastoris, on the basis of previous knockout studies in a native host, Aspergillus terreus. Polyketide synthase AtX was found to catalyze the formation of partially reduced polyketide 6-methylsalicylic acid, followed by 3-methylcatechol synthesis by salicylate 1-monooxygenase AtA-mediated decarboxylative hydroxylation of 6-methylsalicylic acid. Our results show that cytochrome P450 monooxygenase AtE hydroxylates 3-methylcatechol, thus producing the next product, 3-methyl-1,2,4-benzenetriol. A smaller putative cytochrome P450 monooxygenase, AtG, assists with this step. Then, AtD causes epoxidation and hydroxyl oxidation of 3-methyl-1,2,4-benzenetriol and produces a compound terremutin, via which the previously unknown function of AtD was identified as cyclooxygenation. The final step involves an oxidation reaction of a hydroxyl group by a glucose-methanol-choline oxidoreductase, AtC, which leads to the final product: terreic acid. Functions of AtD and AtG were determined for the first time. All the genes were reanalyzed and all intermediates and final products were isolated and identified. Our model fully defines the molecular steps and corrects previous results from the literature.

Cocrystals of kaempferol, quercetin and myricetin with 4,4‧-bipyridine: Crystal structures, analyses of intermolecular interactions and antibacterial properties

NASA Astrophysics Data System (ADS)

Zhang, Yu-Nan; Yin, He-Mei; Zhang, Yu; Zhang, Da-Jun; Su, Xin; Kuang, Hai-Xue

2017-02-01

With an aim to explore the interactions of Osbnd H⋯N between hydroxyl moiety of the flavonoids and the pyridyl ring of N-containing aromatic amines, three flavonols with varying B-ring-hydroxyl groups (kaempferol, quercetin, and myricetin) were selected to combine with 4,4‧-bipyridine. As a result, three new cocrystals of flavonols were obtained with a solution evaporation approach. These three cocrystals were characterized by single crystal X-ray diffraction, XPRD, IR and NMR methods. The resulting cocrystals were kaempferol: 4,4‧-bipyridine (2:1) (KAE·BPY·2H2O), quercetin: 4,4‧-bipyridine (1:1.5) (QUE·BPY), and myricetin: 4,4‧-bipyridine (1:2) (MYR·BPY·H2O). Structural analyses show that an array of hydrogen bonds and π-π stacking interactions interconnect the molecules to form a two-dimensional (2D) supramolecular layer in KAE·BPY·2H2O, QUE·BPY, and MYR·BPY·H2O. In the three cocrystals, they present as three different synthons-ⅠR88(58), Ⅳ R44(42) and, Ⅶ R66(29) with 4,4‧-bipyridine, respectively-which may yield a strategy for constructing the supramolecule. Cocrystals of flavonols combined with N-containing aromatic amines, 7-OH, B-ring-hydroxyl number and/or the location of the flavonols to play a significant part in extending the dimensionality of the cocrystals. The resulting motif formation and crystal packing in these flavonols cocrystals has combined with N-containing aromatic amines. Additionally, the antibacterial properties of the three cocrystals against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) have been investigated.

Synthesis and characterization of covalently bound benzocaine graphite oxide derivative

NASA Astrophysics Data System (ADS)

Kabbani, Ahmad; Kabbani, Mohamad; Safadi, Khadija

2015-09-01

Graphite oxide (GO) derived materials include chemically functionalize or reduced graphene oxide (exfoliated from GO) sheets, assembled paper-like forms , and graphene-based composites GO consists of intact graphitic regions interspersed with sp3-hybridized carbons containing hydroxyl and epoxide functional groups on the top and bottom surfaces of each sheet and sp2-hybridized carbons containing carboxyl and carbonyl groups mostly at the sheet edges. Hence, GO is hydrophilic and readily disperses in water to form stable colloidal suspensions Due to the attached oxygen functional groups, GO was used to prepare different derivatives which result in some physical and chemical properties that are dramatically different from their bulk counterparts .The present work discusses the covalent cross linking of graphite oxide to benzocaine or ethyl ester of para-aminobenzoic acid,structure I,used in many over-the-counter ointment drug.Synthesis is done via diazotization of the amino group.The product is characterized via IR,Raman, X-ray photoelectron spectroscopy as well as electron microscopy.

Pd-Catalyzed Acetoxylation of γ-C(sp3)-H Bonds of Amines Directed by a Removable Bts-Protecting Group.

PubMed

Zheng, Yong; Song, Weibin; Zhu, Yefu; Wei, Bole; Xuan, Lijiang

2018-02-16

Pd-catalyzed acetoxylation of γ-C(sp 3 )-H bonds directed by Bts-protected amines using inexpensive PhI(OAc) 2 as oxidant is reported. The Bts-protecting group is easily introduced and removed under mild conditions. This protocol provides an important strategy for the construction of γ-hydroxyl amine derivatives.

Surface bioactivity modification of titanium by CO 2 plasma treatment and induction of hydroxyapatite: In vitro and in vivo studies

NASA Astrophysics Data System (ADS)

Hu, Xixue; Shen, Hong; Shuai, Kegang; Zhang, Enwei; Bai, Yanjie; Cheng, Yan; Xiong, Xiaoling; Wang, Shenguo; Fang, Jing; Wei, Shicheng

2011-01-01

Since metallic biomaterials used for orthopedic and dental implants possess a paucity of reactive functional groups, bioactivity modification of these materials is challenging. In the present work, the titanium discs and rods were treated with carbon dioxide plasma and then incubated in a modified simulated body fluid 1.5SBF to obtain a hydroxyapatite layer. Surface hydrophilicity of samples, changes of surface chemistry, surface morphologies of samples, and structural analysis of formed hydroxyapatite were investigated by contact angle to water, X-ray photoelectron spectrometer (XPS), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) and X-ray diffraction (XRD). The results demonstrated that hydrophilicity of titanium surface was improved and hydroxyl groups increased after modification with carbon dioxide plasma treatment. The hydroxyl groups on the surface of titanium were the richest after carbon dioxide plasma treatment under the condition of 20 W for less than 30 s. The hydroxyapatite formability of titanium surface was enhanced by carbon dioxide plasma pretreatment, which was attributed to the surface chemistry. MC3T3-E1 cell as a model cell was cultured on the Ti, CPT-Ti and CPT/SBF-Ti discs in vitro, and the results of the morphology and differentiation of the cell showed that CPT/SBF-Ti was the highest bioactive. The relative parameters of the new bone around the Ti and CPT/SBF-Ti rods including bone mineral density (BMD), a ratio of bone volume to total volume (BV/TV), trabecular thickness (Tb.Th.) and trabecular number (Tb.N.) were analyzed by a micro-computed tomography (micro-CT) after 4-, 8- and 12-week implantation periods in vivo. The results indicated that the CPT/SBF-Ti was more advantageous for new bone formation.

Protein immobilization onto various surfaces using a polymer-bound isocyanate

NASA Astrophysics Data System (ADS)

Kang, Hyun-Jin; Cha, Eun Ji; Park, Hee-Deung

2015-01-01

Silane coupling agents have been widely used for immobilizing proteins onto inorganic surfaces. However, the immobilization method using silane coupling agents requires several treatment steps, and its application is limited to only surfaces containing hydroxyl groups. The aim of this study was to develop a novel method to overcome the limitations of the silane-based immobilization method using a polymer-bound isocyanate. Initially, polymer-bound isocyanate was dissolved in organic solvent and then was used to dip-coat inorganic surfaces. Proteins were then immobilized onto the dip-coated surfaces by the formation of urea bonds between the isocyanate groups of the polymer and the amine groups of the protein. The reaction was verified by FT-IR in which NCO stretching peaks disappeared, and CO and NH stretching peaks appeared after immobilization. The immobilization efficiency of the newly developed method was insensitive to reaction temperatures (4-50 °C), but the efficiency increased with reaction time and reached a maximum after 4 h. Furthermore, the method showed comparable immobilization efficiency to the silane-based immobilization method and was applicable to surfaces that cannot form hydroxyl groups. Taken together, the newly developed method provides a simple and efficient platform for immobilizing proteins onto surfaces.

Modelling the Interaction of Catecholamines with the α1A Adrenoceptor Towards a Ligand-induced Receptor Structure

NASA Astrophysics Data System (ADS)

Kinsella, Gemma K.; Rozas, Isabel; Watson, Graeme W.

2005-06-01

Adrenoceptors are members of the important G protein coupled receptor family for which the detailed mechanism of activation remains unclear. In this study, we have combined docking and molecular dynamics simulations to model the ligand induced effect on an homology derived human α1A adrenoceptor. Analysis of agonist/α1A adrenoceptor complex interactions focused on the role of the charged amine group, the aromatic ring, the N-methyl group of adrenaline, the beta hydroxyl group and the catechol meta and para hydroxyl groups of the catecholamines. The most critical interactions for the binding of the agonists are consistent with many earlier reports and our study suggests new residues possibly involved in the agonist-binding site, namely Thr-174 and Cys-176. We further observe a number of structural changes that occur upon agonist binding including a movement of TM-V away from TM-III and a change in the interactions of Asp-123 of the conserved DRY motif. This may cause Arg-124 to move out of the TM helical bundle and change the orientation of residues in IC-II and IC-III, allowing for increased affinity of coupling to the G-protein.

Elastohydrodynamic Traction Properties of Seed Oils

USDA-ARS?s Scientific Manuscript database

The elastohydrodynamic traction coefficient (tc) properties of nine seed oils of varying chemical structures, PAO and hexadecane, were investigated using a ball-on disk traction apparatus. The seed oils were: castor oil, a triglyceride with hydroxyl functional group; jojoba, a monoglyceride; and s...

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lu, Weigang; Yuan, Daqiang; Yakovenko, Andrey A

A super-paddlewheel (comprised of two paddlewheels) metal–organic polyhedron (MOP) containing surface hydroxyl groups was synthesized and characterized. Condensation reactions with linear alkyl anhydrides lead to new MOPs with enhanced solubility. As a result, the surface-modified MOP 4 was demonstrated as a homogeneous Lewis-acid catalyst.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lu, Weigang; Yuan, Daqiang; Yakovenko, Andrey

A super-paddlewheel (comprised of two paddlewheels) metal-organic polyhedron (MOP) containing surface hydroxyl groups was synthesized and characterized. Condensation reactions with linear alkyl anhydrides lead to new MOPs with enhanced solubility. As a result, the surface-modified MOP 4 was demonstrated as a homogeneous Lewis-acid catalyst.

Oxidation of Secondary Alcohols by Duckweed: A Biotransformation Experiment for Undergraduate Students.

ERIC Educational Resources Information Center

Karfarski, Pawel; And Others

1988-01-01

Describes an experiment designed to use the ability of duckweed to convert the secondary hydroxyl moieties into ketone groups. Discusses the preparation of plant material, materials, procedures, and results for this biotransformation experiment for undergraduate students. (CW)

Non-covalent interaction between dietary stilbenoids and human serum albumin: Structure-affinity relationship, and its influence on the stability, free radical scavenging activity and cell uptake of stilbenoids.

PubMed

Cao, Hui; Jia, Xueping; Shi, Jian; Xiao, Jianbo; Chen, Xiaoqing

2016-07-01

Dietary stilbenoids are associated with many benefits for human health, which depend on their bioavailability and bioaccessibility. The stilbenoid-human serum albumin (HSA) interactions are investigated to explore the structure-affinity relationship and influence on the stability, free radical scavenging activity and cell uptake of stilbenoids. The structure-affinity relationship of the stilbenoids-HSA interaction was found as: (1) the methoxylation enhanced the affinity, (2) an additional hydroxyl group increases the affinity and (3) the glycosylation significantly weakened the affinity. HSA obviously masked the free radical scavenging potential of stilbenoids. The stabilities of stilbenoids in different medium were determined as: HSA solution>human plasma>Dulbecco's modified Eagle's medium. It appears that the milk enhanced the cell uptake of stilbenoids with multi-hydroxyl groups and weakened the cell uptake of stilbenoids with methoxyl group on EA.hy 926 endothelial cells. The stilbenoids are hardly absorbed by human umbilical vein endothelial cells in the presence of milk. Copyright © 2016 Elsevier Ltd. All rights reserved.

Structure-affinity relationship of the interaction between phenolic acids and their derivatives and β-lactoglobulin and effect on antioxidant activity.

PubMed

Wu, Simin; Zhang, Yunyue; Ren, Fazheng; Qin, Yinghui; Liu, Jiaxin; Liu, Jingwen; Wang, Qingyu; Zhang, Hao

2018-04-15

In this study, 71 phenolic acids and their derivatives were used to investigate the structure-affinity relationship of β-lactoglobulin binding, and the effect of this interaction on antioxidant activity. Based on a fluorescence quenching method, an improved mathematical model was adopted to calculate the binding constants, with a correction for the inner-filter effect. Hydroxylation at the 3-position increased the affinity of the phenolic acids for β-lactoglobulin, while hydroxylation at the 2- or 4-positions had a negative effect. Complete methylation of all hydroxy groups, except at the 3-position, enhanced the binding affinity. Replacing the hydroxy groups with methyl groups at the 2-position also had a positive effect. Hydrogen bonding was one of the binding forces for the interaction. The antioxidant activity of phenolic acid-β-lactoglobulin complexes was higher than that of phenolic acids alone. These findings provide an understanding of the structure-activity relationship of the interaction between β-lactoglobulin and phenolic acids. Copyright © 2017 Elsevier Ltd. All rights reserved.

Analysis of acid-base interactions at Al2O3 (11-20) interfaces by means of single molecule force spectroscopy

NASA Astrophysics Data System (ADS)

Mosebach, Bastian; Ozkaya, Berkem; Giner, Ignacio; Keller, Adrian; Grundmeier, Guido

2017-10-01

Single molecule force spectroscopy (SMFS) was employed to investigate the interaction forces between aliphatic amino, hydroxyl and ether groups and aluminum oxide single crystal surfaces in an aqueous electrolyte at pH = 6. The force studies were based on the variation of the terminal group of polyethylene glycol which was bound via a Ssbnd Au bond to the gold coated AFM tip. X-ray Photoelectron Spectroscopy (XPS) was performed to characterize the surface chemistry of the substrate. Force distance curves were measured between the PEG-NH2, sbnd OH and sbnd OCH3 functionalized atomic force microscope (AFM) tip and the non-polar single crystalline Al2O3(11-20) surface. The experimental results exhibit non-equilibrium desorption events which hint at acid-base interactions of the electron donating hydroxyl and amino groups with Al-ions in the surface of the oxide. The observed desorption forces for the sbnd NH2, sbnd OH/Al2O3(11-20) were in the range of 100-200 pN.

Nucleic acid detection methods

DOEpatents

Smith, C.L.; Yaar, R.; Szafranski, P.; Cantor, C.R.

1998-05-19

The invention relates to methods for rapidly determining the sequence and/or length a target sequence. The target sequence may be a series of known or unknown repeat sequences which are hybridized to an array of probes. The hybridized array is digested with a single-strand nuclease and free 3{prime}-hydroxyl groups extended with a nucleic acid polymerase. Nuclease cleaved heteroduplexes can be easily distinguish from nuclease uncleaved heteroduplexes by differential labeling. Probes and target can be differentially labeled with detectable labels. Matched target can be detected by cleaving resulting loops from the hybridized target and creating free 3-hydroxyl groups. These groups are recognized and extended by polymerases added into the reaction system which also adds or releases one label into solution. Analysis of the resulting products using either solid phase or solution. These methods can be used to detect characteristic nucleic acid sequences, to determine target sequence and to screen for genetic defects and disorders. Assays can be conducted on solid surfaces allowing for multiple reactions to be conducted in parallel and, if desired, automated. 18 figs.

Coordination chemistry with phosphine and phosphine oxide-substituted hydroxyferrocenes.

PubMed

Atkinson, Robert C J; Gibson, Vernon C; Long, Nicholas J; White, Andrew J P

2010-08-28

New unsymmetrical hydroxyferrocenes were synthesised from dibromoferrocene. The oxygen heteroatom was introduced via lithiation and quenching with bis-trimethylsilylperoxide followed by hydrolysis to unmask the hydroxyl functionality. The coordination chemistry of 1'-(diphenylphosphino)-1-hydroxyferrocene 2 was explored with palladium and rhodium precursors. A dinuclear palladium methyl complex with bridging ferrocenyloxo groups was obtained from the reaction between 2 and (cyclooctadiene)methylchloropalladium(II). With tetracarbonyldichlorodirhodium(I), two complexes were isolated. The major product was a bis ligand cis phosphine ligated complex with one ligand bound in a chelating mode and one with a pendant hydroxyl group. A minor product was crystallographically characterised as a dinuclear ferrocenyloxo-bridged rhodium carbonyl complex. The coordination chemistry of 2 and the corresponding phosphine oxide 3 was examined with group 4 metals and the resulting complexes examined as ethylene polymerisation catalysts. The ligands were found to bind in either a chelating fashion or with pendant phosphine donors. In all cases, low to moderately active ethylene polymerisation catalysts were found. The catalysts were very unstable and catalyst residues were observed in the isolated polymer indicating a short catalyst lifetime.

Silicon nitride boundary lubrication: Effect of oxygenates

NASA Astrophysics Data System (ADS)

Gates, Richard S.; Hsu, Stephen M.

1995-07-01

A ball-on-three-flat (BTF) wear tester was used to investigate the boundary lubricating characteristics of oxygenates on a commercial silicon nitride. A wide variety of oxygen-containing compounds containing hydroxyl functioal groups were more effective compared to a base case of neat paraffin oil. Decreases of up to 58% in friction coefficient, and 95% in wear were obtained. In most cases, films were obseved in and around the wear scar, suggesting chemical reactions had taken place in the contact. Additional wear tests, conducted using neat shorter-chain linear primary alcohols, i.e., 6-10 carbons, demonstrated boundary lubrication protection, with longer chain length providing better antiwear performance. A study of several C8 compounds with specific oxygen-containing functional groups (primary alcohol, secondary alcohols, acid, aldehyde, and ketone) demonstrated that the primary alcohol had the strongest boundary lubricating effect. Varying the amount of water in the alcohols had little effect on friction and wear, suggesting that the boundary lubrication effects observed were not merely due to dissolved water in these fluids, but some characteristic chemical interaction with the hydroxyl functional group of the alcohols and acids.

Mistletoe lectin I in complex with galactose and lactose reveals distinct sugar-binding properties

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mikeska, Ruth; Wacker, Roland; Arni, Raghuvir

2005-01-01

The structures of mistletoe lectin I in complex with lactose and galactose reveal differences in binding by the two known sites in subdomains α1 and γ2 and suggest the presence of a third low-affinity site in subdomain β1. The structures of mistletoe lectin I (ML-I) from Viscum album complexed with lactose and galactose have been determined at 2.3 Å resolution and refined to R factors of 20.9% (R{sub free} = 23.6%) and 20.9 (R{sub free} = 24.6%), respectively. ML-I is a heterodimer and belongs to the class of ribosome-inactivating proteins of type II, which consist of two chains. The A-chainmore » has rRNA N-glycosidase activity and irreversibly inhibits eukaryotic ribosomes. The B-chain is a lectin and preferentially binds to galactose-terminated glycolipids and glycoproteins on cell membranes. Saccharide binding is performed by two binding sites in subdomains α1 and γ2 of the ML-I B-chain separated by ∼62 Å from each other. The favoured binding of galactose in subdomain α1 is achieved via hydrogen bonds connecting the 4-hydroxyl and 3-hydroxyl groups of the sugar moiety with the side chains of Asp23B, Gln36B and Lys41B and the main chain of 26B. The aromatic ring of Trp38B on top of the preferred binding pocket supports van der Waals packing of the apolar face of galactose and stabilizes the sugar–lectin complex. In the galactose-binding site II of subdomain γ2, Tyr249B provides the hydrophobic stacking and the side chains of Asp235B, Gln238B and Asn256B are hydrogen-bonding partners for galactose. In the case of the galactose-binding site I, the 2-hydroxyl group also stabilizes the sugar–protein complex, an interaction thus far rarely detected in galactose-specific lectins. Finally, a potential third low-affinity galactose-binding site in subunit β1 was identified in the present ML-I structures, in which a glycerol molecule from the cryoprotectant buffer has bound, mimicking the sugar compound.« less

Silver Coordination Polymers for Prevention of Implant Infection: Thiol Interaction, Impact on Respiratory Chain Enzymes, and Hydroxyl Radical Induction▿ †

PubMed Central

Gordon, Oliver; Vig Slenters, Tünde; Brunetto, Priscilla S.; Villaruz, Amer E.; Sturdevant, Daniel E.; Otto, Michael; Landmann, Regine; Fromm, Katharina M.

2010-01-01

Prosthetic joint replacements are used increasingly to alleviate pain and improve mobility of the progressively older and more obese population. Implant infection occurs in about 5% of patients and entails significant morbidity and high social costs. It is most often caused by staphylococci, which are introduced perioperatively. They are a source of prolonged seeding and difficult to treat due to antibiotic resistance; therefore, infection prevention by prosthesis coating with nonantibiotic-type anti-infective substances is indicated. A renewed interest in topically used silver has fostered development of silver nanoparticles, which, however, present a potential health hazard. Here we present new silver coordination polymer networks with tailored physical and chemical properties as nanostructured coatings on metallic implant substrates. These compounds exhibited strong biofilm sugar-independent bactericidal activity on in vitro-grown biofilms and prevented murine Staphylococcus epidermidis implant infection in vivo with slow release of silver ions and limited transient leukocyte cytotoxicity. Furthermore, we describe the biochemical and molecular mechanisms of silver ion action by gene screening and by targeting cell metabolism of S. epidermidis at different levels. We demonstrate that silver ions inactivate enzymes by binding sulfhydryl (thiol) groups in amino acids and promote the release of iron with subsequent hydroxyl radical formation by an indirect mechanism likely mediated by reactive oxygen species. This is the first report investigating the global metabolic effects of silver in the context of a therapeutic application. We anticipate that the compounds presented here open a new treatment field with a high medical impact. PMID:20660682

Three methods for in situ cross-linking of polyvinyl alcohol films for application as ion-conducting membranes in potassium hydroxide electrolyte. [battery separators

NASA Technical Reports Server (NTRS)

Philipp, W. H.; Hsu, L. C.

1979-01-01

Three methods of in situ cross-linking polyvinyl alcohol films are presented. They are: (1) acetalization with a dialdehyde such as glutaraldehyde, (2) acetalization with aldehyde groups formed by selective oxidative cleaving of the few percent of 1,2 diol units present in polyvinyl alcohol, and (3) cross-linking by hydrogen abstraction by reaction with hydrogen atoms and hydroxyl radicals from irradiated water. For the third method, improvement in film conductivity in KOH solution at the expense of mechanical strength is obtained by the presence of polyacrylic acid in the polyvinyl alcohol films. Resistivities in 45 percent KOH are given for in situ cross-linked films prepared by each of the three methods.

Synthesis and chemical reactions of the steroidal hormone 17α-methyltestosterone.

PubMed

El-Desoky, El-Sayed Ibrahim; Reyad, Mahmoud; Afsah, Elsayed Mohammed; Dawidar, Abdel-Aziz Mahmoud

2016-01-01

Structural modifications of natural products with complex structures like steroids require great synthetic effort. A review of literature is presented on the chemistry of the steroidal hormone 17α-methyltestosterone that is approved by Food and Drug Administration (FDA) in the United States as an androgen for estrogen-androgen hormone replacement therapy treatment. The analog also offers special possibilities for the prevention/treatment of hormone-sensitive cancers. The testosterone skeleton has important functionalities in the molecule that can act as a carbonyl component, an active methylene compound, α,β-unsaturated enone and tertiary hydroxyl group in various chemical reactions to access stereoisomeric steroidal compounds with potent activity. In addition, microbiological methods of synthesis and transformation of this hormone are presented. Copyright © 2015 Elsevier Inc. All rights reserved.

Quantification of hydroxyl radical produced during phacoemulsification.

PubMed

Gardner, Jonathan M; Aust, Steven D

2009-12-01

To quantitate hydroxyl radicals produced during phacoemulsification with various irrigating solutions and conditions used in cataract surgery. Chemistry and Biochemistry Department, Utah State University, Logan, Utah, USA. All experiments were performed using an Infiniti Vision System phacoemulsifier with irrigation and aspiration. Hydroxyl radicals were quantitated using electron spin resonance spectroscopy and a spectrophotometric assay for malondialdehyde, which is formed by the oxidation of deoxyribose by the hydroxyl radical. Hydroxyl radical production increased during longitudinal-stroking phacoemulsification as power levels were increased in a nonlinear, nonexponential fashion. The detection of hydroxyl radical was reduced in irrigating solutions containing organic molecules (eg, citrate, acetate, glutathione, dextrose) and further reduced in Navstel, an irrigating solution containing a viscosity-modifying agent, hydroxypropyl methylcellulose. Hydroxyl radicals produced in settings representative of those used in phacoemulsification cataract surgery were quantitated using the deoxyribose method. Hydroxyl radical production was dependent on the level of ultrasound power applied and the irrigating solution used. Oxidative stress on the eye during phacoemulsification may be minimized by using irrigating solutions that contain organic molecules, including the viscosity-modifying agent hydroxypropyl methylcellulose, that can compete for reaction with hydroxyl radicals.

Evidence for a hydroxide ion bridging two magnesium ions at the active site of the hammerhead ribozyme.

PubMed Central

Hermann, T; Auffinger, P; Scott, W G; Westhof, E

1997-01-01

In the presence of magnesium ions, cleavage by the hammerhead ribozyme RNA at a specific residue leads to 2'3'-cyclic phosphate and 5'-OH extremities. In the cleavage reaction an activated ribose 2'-hydroxyl group attacks its attached 3'-phosphate. Molecular dynamics simulations of the crystal structure of the hammerhead ribozyme, obtained after flash-freezing of crystals under conditions where the ribozyme is active, provide evidence that a mu-bridging OH-ion is located between two Mg2+ions close to the cleavable phosphate. Constrained simulations show further that a flip from the C3'- endo to the C2'- endo conformation of the ribose at the cleavable phosphate brings the 2'-hydroxyl in proximity to both the attacked phosphorous atom and the mu-bridging OH-ion. Thus, the simulations lead to a detailed new insight into the mechanism of hammerhead ribozyme cleavage where a mu-hydroxo bridged magnesium cluster, located on the deep groove side, provides an OH-ion that is able to activate the 2'-hydroxyl nucleophile after a minor and localized conformational change in the RNA. PMID:9254698

Origin of Coverage Dependence in Photoreactivity of Carboxylate on TiO2(110): Hindering by Charged Coadsorbed Hydroxyls

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Zhitao; Henderson, Michael A.; Lyubinetsky, Igor

2015-09-30

The influence of reactant coverage on photochemical activity was explored using scanning tunneling microscopy (STM) and ultraviolet photoelectron spectroscopy (UPS). We observed diminished reactivity of carboxylate species (trimethyl acetate, TMA) on TiO2(110) as a function of increasing coverage. This effect was not linked to intermolecular interactions of TMA but to the accumulation of the coadsorbed bridging hydroxyls (HOb) deposited during (thermal) dissociative adsorption of the parent, trimethylacetic acid (TMAA). Confirmation of the hindering influence of HOb groups was obtained by the observation that HOb species originated from H2O dissociation at O-vacancy sites have a similar hindering effect on TMA photochemistry.more » Though HOb’s are photoinactive on TiO2(110) under ultrahigh vacuum conditions, UPS results show that these sites trap photoexcited electrons, which in turn likely (electrostatically) attract and neutralize photoexcited holes, thus suppressing the hole-mediated photoreactivity of TMA. This negative influence of surface hydroxyls on hole-mediated photochemistry is likely a major factor in other anaerobic photochemical processes on reducible oxide surfaces.« less

Inhibition of metallopeptidases by flavonoids and related compounds.

PubMed

Bormann, H; Melzig, M F

2000-02-01

To elucidate possible mechanisms of activity in medicinal plants containing flavonoids, the inhibitory potency of twenty flavones, flavonols, flavanones, phenylacrylic acids and various hydroxylated phenylacetic acids on the activity of neutral endopeptidase (NEP; EC 3.4.24.11), angiotensin-converting enzyme (ACE; EC 3.4.15.1) and aminopeptidase N (APN; EC 3.4.11.2) was investigated in vitro. The screening generally resulted that inhibition of these enzymes requires free hydroxyl groups at the flavone molecule. Flavone and methoxylated compounds (sinensetin) were without effects. Flavonoids with free hydroxyl functions in position 3',4' and 5,7 inhibited the activity of NEP (quercetin, luteolin, fisetin), with myricetin (IC50 = 42 microM) as strongest inhibitor. Inhibition of ACE and APN did not depend on this class of compounds and substitution pattern. E.g. 3,4-dihydroxyphenylacetic acid and 4-methylcatechol (urinary metabolites of flavonoids) also inhibited both APN and ACE activity, but not NEP activity. The results demonstrate that some of the pharmacological activities of flavonoids might be related to the inhibition of metallopeptidases responsible for the splitting of regulatory neuropeptides.

Elastohydrodynamic (EHD) traction properties of seed oils

USDA-ARS?s Scientific Manuscript database

The elastohydrodynamic traction coefficient (tc) properties of nine seed oils of varying chemical structures, PAO and hexadecane, were investigated using a ball-on disk traction apparatus. The seed oils were: castor oil, a triglyceride with hydroxyl functional group; jojoba, a monoglyceride; and sev...

Phenylpropanoid esters of lesquerella and castor oil

USDA-ARS?s Scientific Manuscript database

Lesquerella (LO) and castor oil (CO) were esterified at the secondary hydroxyl groups of their 14-hydroxyeicos-cis-11-enoic fatty acids and 12-hydroxyoctadec-cis-9-enoic fatty acids, respectively, with 4-acetoxy-3-methoxycinnamic acid (acetoxyferulic acid). The unconventional esterifications were co...

Effects of hydroxylated benzaldehyde derivatives on radiation-induced reactions involving various organic radicals

NASA Astrophysics Data System (ADS)

Ksendzova, G. A.; Samovich, S. N.; Sorokin, V. L.; Shadyro, O. I.

2018-05-01

In the present paper, the effects of hydroxylated benzaldehyde derivatives and gossypol - the known natural occurring compound - on formation of decomposition products resulting from radiolysis of ethanol and hexane in deaerated and oxygenated solutions were studied. The obtained data enabled the authors to make conclusions about the effects produced by the structure of the compounds under study on their reactivity towards oxygen- and carbon-centered radicals. It has been found that 2,3-dihydroxybenzaldehyde, 4,6-di-tert-butyl-2,3-dihydroxybenzaldehyde and 4,6-di-tert-butyl-3-(1,3-dioxane-2-yl)-1,2-dihydroxybenzene are not inferior in efficiency to butylated hydroxytoluene - the industrial antioxidant - as regards suppression of the radiation-induced oxidation processes occurring in hexane. The derivatives of hydroxylated benzaldehydes were shown to have a significant influence on radiation-induced reactions involving α-hydroxyalkyl radicals.

Unusual spin-trap chemistry for the reaction of hydroxyl radical with the carcinogen N-nitrosodimethylamine

NASA Astrophysics Data System (ADS)

Wink, David A.; Desrosiers, Marc F.

The reaction of the potent carcinogen N-nitrosodimethylamine (NDMA) with hydroxyl radical generated via radiolysis was studied using EPR techniques. Attempts to spin trap NDMA radical intermediates with 3,5-dibromo-4-nitrosobenzene sulfonate (DBNBS) produced only unusual DBNBS radicals. One of these radicals was shown to be generated by both reaction of DBNBS with nitric oxide, and direct oxidation of DBNBS with an inorganic oxidant ( .Br -2). Another DBNBS radical was identified as a sulfite spin adduct resulting from the degradation of DBNBS by a NDMA reactive intermediate. In the absence of DBNBS, hydroxyl radical reaction with NDMA gave the dimethylnitroxide radical. Unexpectedly, addition of DBNBS to a solution containing dimethylnitroxide produced an EPR spectrum nearly identical to that of NDMA solutions with DBNBS added before radiolysis. A proposed mechanism accounting for these observations is presented.

Prolyl hydroxylation in elastin is not random.

PubMed

Schmelzer, Christian E H; Nagel, Marcus B M; Dziomba, Szymon; Merkher, Yulia; Sivan, Sarit S; Heinz, Andrea

2016-10-01

This study aimed to investigate the prolyl and lysine hydroxylation in elastin from different species and tissues. Enzymatic digests of elastin samples from human, cattle, pig and chicken were analyzed using mass spectrometry and bioinformatics tools. It was confirmed at the protein level that elastin does not contain hydroxylated lysine residues regardless of the species. In contrast, prolyl hydroxylation sites were identified in all elastin samples. Moreover, the analysis of the residues adjacent to prolines allowed the determination of the substrate site preferences of prolyl 4-hydroxylase. It was found that elastins from all analyzed species contain hydroxyproline and that at least 20%-24% of all proline residues were partially hydroxylated. Determination of the hydroxylation degrees of specific proline residues revealed that prolyl hydroxylation depends on both the species and the tissue, however, is independent of age. The fact that the highest hydroxylation degrees of proline residues were found for elastin from the intervertebral disc and knowledge of elastin arrangement in this tissue suggest that hydroxylation plays a biomechanical role. Interestingly, a proline-rich domain of tropoelastin (domain 24), which contains several repeats of bioactive motifs, does not show any hydroxyproline residues in the mammals studied. The results show that prolyl hydroxylation is not a coincidental feature and may contribute to the adaptation of the properties of elastin to meet the functional requirements of different tissues. The study for the first time shows that prolyl hydroxylation is highly regulated in elastin. Copyright © 2016 Elsevier B.V. All rights reserved.

Structure-based Mechanism of CMP-2-keto-3-deoxymanno-octulonic Acid Synthetase

PubMed Central

Heyes, Derren J.; Levy, Colin; Lafite, Pierre; Roberts, Ian S.; Goldrick, Marie; Stachulski, Andrew V.; Rossington, Steven B.; Stanford, Deborah; Rigby, Stephen E. J.; Scrutton, Nigel S.; Leys, David

2009-01-01

The enzyme CMP-Kdo synthetase (KdsB) catalyzes the addition of 2-keto-3-deoxymanno-octulonic acid (Kdo) to CTP to form CMP-Kdo, a key reaction in the biosynthesis of lipopolysaccharide. The reaction catalyzed by KdsB and the related CMP-acylneuraminate synthase is unique among the sugar-activating enzymes in that the respective sugars are directly coupled to a cytosine monophosphate. Using inhibition studies, in combination with isothermal calorimetry, we show the substrate analogue 2β-deoxy-Kdo to be a potent competitive inhibitor. The ligand-free Escherichia coli KdsB and ternary complex KdsB-CTP-2β-deoxy-Kdo crystal structures reveal that Kdo binding leads to active site closure and repositioning of the CTP phosphates and associated Mg2+ ion (Mg-B). Both ligands occupy conformations compatible with an Sn2-type attack on the α-phosphate by the Kdo 2-hydroxyl group. Based on strong similarity with DNA/RNA polymerases, both in terms of overall chemistry catalyzed as well as active site configuration, we postulate a second Mg2+ ion (Mg-A) is bound by the catalytically competent KdsB-CTP-Kdo ternary complex. Modeling of this complex reveals the Mg-A coordinated to the conserved Asp100 and Asp235 in addition to the CTP α-phosphate and both the Kdo carboxylic and 2-hydroxyl groups. EPR measurements on the Mn2+-substituted ternary complex support this model. We propose the KdsB/CNS sugar-activating enzymes catalyze the formation of activated sugars, such as the abundant CMP-5-N-acetylneuraminic acid, by recruitment of two Mg2+ to the active site. Although each metal ion assists in correct positioning of the substrates and activation of the α-phosphate, Mg-A is responsible for activation of the sugar-hydroxyl group. PMID:19815542

A novel biocatalytic approach to acetylation of 1-β-D-arabinofuranosylcytosine by Aspergillus oryzae whole cell in organic solvents.

PubMed

Li, Xiao-Feng; Zhu, Zhen; Zhao, Guang-Lei; Yu, Yi-Gang; Lai, Fu-Rao; Wu, Hui

2012-01-01

Biocatalytic acylation of 1-β-D-arabinofuranosylcytosine (ara-C) was developed using whole cell of Aspergillus oryzae as a novel catalyst. (13)C nuclear magnetic resonance (NMR) analysis indicated that the whole-cell biocatalyst had more specific activity toward the 3'-hydroxyl group than 5'-hydroxyl group among the available hydroxyl groups in sugar moiety of ara-C. Except for glucose and maltose, 11 carbon sources supplemented to basal media, including Spans, Tweens, olive oil and oleic acid, exhibited notable enhancement effects on both the cell growth and the acylation reactions. It was suggested that the carbon sources containing controlled-release oleic acid were the important substrates for the production of fungal cell-bound lipase with specific activity, partially due to a gradual induction effect of their released oleic acid on the cell-bound lipase production. Despite the low initial reaction rate and substrate conversion, the addition of 2.0 g/l Span 80 resulted in a higher 3'-regioselectivity of the cells than 81%. By using Tween 85 at its optimum concentration of 5.0 g/l, however, the highest initial rates (3.2 mmol/l h) and substrate conversion (76%) of the whole-cell catalyzed acylation of ara-C can be achieved. It was also found that the 3'-regioselectivity of the cells showed observable increase by extending the culture time. And the activity of cell-bound lipase drastically increased in the early stage of cell growth and then declined in the late culture stage, whatever the culture media used. Our results thus indicated that A. oryzae whole cell was a promising green tool for biosynthesis of nucleoside esters with potential bioactivities.

Reactivity of hydropersulfides toward the hydroxyl radical unraveled: disulfide bond cleavage, hydrogen atom transfer, and proton-coupled electron transfer.

PubMed

Anglada, Josep M; Crehuet, Ramon; Adhikari, Sarju; Francisco, Joseph S; Xia, Yu

2018-02-14

Hydropersulfides (RSSH) are highly reactive as nucleophiles and hydrogen atom transfer reagents. These chemical properties are believed to be key for them to act as antioxidants in cells. The reaction involving the radical species and the disulfide bond (S-S) in RSSH, a known redox-active group, however, has been scarcely studied, resulting in an incomplete understanding of the chemical nature of RSSH. We have performed a high-level theoretical investigation on the reactions of the hydroxyl radical (˙OH) toward a set of RSSH (R = -H, -CH 3 , -NH 2 , -C(O)OH, -CN, and -NO 2 ). The results show that S-S cleavage and H-atom abstraction are the two competing channels. The electron inductive effect of R induces selective ˙OH substitution at one sulfur atom upon S-S cleavage, forming RSOH and ˙SH for the electron donating groups (EDGs), whereas producing HSOH and ˙SR for the electron withdrawing groups (EWGs). The H-Atom abstraction by ˙OH follows a classical hydrogen atom transfer (hat) mechanism, producing RSS˙ and H 2 O. Surprisingly, a proton-coupled electron transfer (pcet) process also occurs for R being an EDG. Although for RSSH having EWGs hat is the leading channel, S-S cleavage can be competitive or even dominant for the EDGs. The overall reactivity of RSSH toward ˙OH attack is greatly enhanced with the presence of an EDG, with CH 3 SSH being the most reactive species found in this study (overall rate constant: 4.55 × 10 12 M -1 s -1 ). Our results highlight the complexity in RSSH reaction chemistry, the extent of which is closely modulated by the inductive effect of the substituents in the case of the oxidation by hydroxyl radicals.

Functional characterization of O-methyltransferases used to catalyse site-specific methylation in the post-tailoring steps of pradimicin biosynthesis.

PubMed

Han, J W; Ng, B G; Sohng, J K; Yoon, Y J; Choi, G J; Kim, B S

2018-01-01

To identify the roles of the two O-methyltransferase homologous genes pdmF and pdmT in the pradimicin biosynthetic gene cluster of Actinomadura hibisca P157-2. Pradimicins are pentangular polyphenol antibiotics synthesized by bacterial type II polyketide synthases (PKSs) and tailoring enzymes. Pradimicins are naturally derivatized by combinatorial O-methylation at two positions (i.e., 7-OH and 11-OH) of the benzo[α]naphthacenequinone structure. PdmF and PdmT null mutants (PFKO and PTKO) were generated. PFKO produced the 11-O-demethyl shunt metabolites 11-O-demethylpradimicinone II (1), 11-O-demethyl-7-methoxypradimicinone II (2), 11-O-demethylpradimicinone I (3) and 11-O-demethylpradimicin A (4), while PTKO generated the 7-O-demethyl derivatives pradimicinone II (5) and 7-hydroxypradimicin A (6). Pradimicinones 1, 2, 3, and 5 were fed to a heterologous host Escherichia coli harbouring expression plasmid pET-22b::pdmF or pET-28a::pdmT. PdmF catalysed 11-O-methylation of pradimicinones 1, 2, and 3 regardless of O-methylation at the C-7 position, while PdmT was unable to catalyse 7-O-methylation when the C-11 hydroxyl group was methylated (5). PdmF and PdmT were involved in 11-O- and 7-O-methylations of the benzo[α]naphthacenequinone moiety of pradimicin, respectively. Methylation of the C-7 hydroxyl group precedes methylation of the C-11 hydroxyl group in pradimicin biosynthesis. This is the first reported demonstration of the functions of PdmF and PdmT for regiospecific O-methylation, which contributes to better understanding of the post-PKS modifications in pradimicin biosynthesis as well as to rational engineering of the pradimicin biosynthetic machinery. © 2017 The Society for Applied Microbiology.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chenna, A.; Singer, B.

Benzene is a carcinogen in rodents and a cause of bone marrow toxicity and leukemia in humans. p-Benzoquinone (p-BQ) is one of the stable metabolites of benzene, as well as of a number of drugs and other chemicals. 2{prime}-Deoxycytidine (dC) and 2{prime}-deoxyadenosine (dA) were allowed to react with p-BQ in aqueous solution at pH 7.4 and 4.5. The yields were considerably higher at pH 4.5 than at pH 7.4 and 4.5. The yields were considerably higher at pH 4.5 than at pH 7.4, as indicated by HPLC analysis. The desired products were isolated by column chromatography on silica gel ormore » cellulose. Identification was done by FAB-MS, {sup 1}H NMR, and UV spectroscopy. The reaction of p-BQ with dC and dA at pH 4.5 produced the exocyclic compounds 3-hydroxy-1,N{sup 4}-benzetheno-2{prime}-deoxycytidine (p-BA-dC), and 9-hydroxy-1,N{sup 6}-benzetheno-2{prime}-deoxyadenosine (p-BQ-dA), respectively, in a large scale and high yield. These adducts have been previously made in a microgram scale as the 3{prime}-phosphate for {sup 32}P-postlabeling studies of their incidence in DNA. The p-BQ-dC and p-BQ-dA adducts have, in addition to the two hydroxyl groups of deoxyribose, one newly formed hydroxyl group a the C-3 or C-9 of the exocyclic base of each product respectively. Incorporation of these adducts into oligonucleotides as the phosphoramidite requires the protection of ll three hydroxyl groups in these compounds. The mass spectroscopic analysis of the DNA oligomers was confirmed by electrospray MS. These oligomers are now under investigation for their biochemical properties. 41 refs., 4 figs.« less

Aqueous-phase oxidation of green leaf volatiles by hydroxyl radical as a source of SOA: Product identification from methyl jasmonate and methyl salicylate oxidation

NASA Astrophysics Data System (ADS)

Hansel, Amie K.; Ehrenhauser, Franz S.; Richards-Henderson, Nicole K.; Anastasio, Cort; Valsaraj, Kalliat T.

2015-02-01

Green leaf volatiles (GLVs) are a group of biogenic volatile organic compounds (BVOCs) released into the atmosphere by vegetation. BVOCs produce secondary organic aerosol (SOA) via gas-phase reactions, but little is known of their aqueous-phase oxidation as a source of SOA. GLVs can partition into atmospheric water phases, e.g., fog, mist, dew or rain, and be oxidized by hydroxyl radicals (˙OH). These reactions in the liquid phase also lead to products that have higher molecular weights, increased polarity, and lower vapor pressures, ultimately forming SOA after evaporation of the droplet. To examine this process, we investigated the aqueous, ˙OH-mediated oxidation of methyl jasmonate (MeJa) and methyl salicylate (MeSa), two GLVs that produce aqueous-phase SOA. High performance liquid chromatography/electrospray ionization mass spectrometry (HPLC-ESI-MS) was used to monitor product formation. The oxidation products identified exhibit higher molecular mass than their parent GLV due to either dimerization or the addition of oxygen and hydroxyl functional groups. The proposed structures of potential products are based on mechanistic considerations combined with the HPLC/ESI-MS data. Based on the structures, the vapor pressure and the Henry's law constant were estimated with multiple methods (SPARC, SIMPOL, MPBPVP, Bond and Group Estimations). The estimated vapor pressures of the products identified are significantly (up to 7 orders of magnitude) lower than those of the associated parent compounds, and therefore, the GLV oxidation products may remain as SOA after evaporation of the water droplet. The contribution of the identified oxidation products to SOA formation is estimated based on measured HPLC-ESI/MS responses relative to previous aqueous SOA mass yield measurements.

Transport of steroid 3-sulfates and steroid 17-sulfates by the sodium-dependent organic anion transporter SOAT (SLC10A6).

PubMed

Grosser, Gary; Bennien, Josefine; Sánchez-Guijo, Alberto; Bakhaus, Katharina; Döring, Barbara; Hartmann, Michaela; Wudy, Stefan A; Geyer, Joachim

2018-05-01

The sodium-dependent organic anion transporter SOAT/Soat shows highly specific transport activity for sulfated steroids. SOAT substrates identified so far include dehydroepiandrosterone sulfate, 16α-hydroxydehydroepiandrosterone sulfate, estrone-3-sulfate, pregnenolone sulfate, 17β-estradiol-3-sulfate, and androstenediol sulfate. Apart from these compounds, many other sulfated steroids occur in mammals. Therefore, we aimed to expand the substrate spectrum of SOAT and analyzed the SOAT-mediated transport of eight different sulfated steroids by combining in vitro transport experiments in SOAT-transfected HEK293 cells with LC-MS/MS analytics of cell lysates. In addition, we aimed to better understand the structural requirements for SOAT substrates and so selected structural pairs varying only at specific positions: 3α/3β-sulfate, 17α/17β-sulfate, mono-sulfate/di-sulfate, and 17α-hydroxylation. We found significant and sodium-dependent SOAT-mediated transport of 17α-hydroxypregnenolone sulfate, 17β-estradiol-17-sulfate, androsterone sulfate, epiandrosterone sulfate, testosterone sulfate, epitestosterone sulfate, and 5α-dihydrotestosterone sulfate. However, 17β-estradiol-3,17-disulfate was not transported by SOAT. SOAT substrates from the group of sulfated steroids are characterized by a planar and lipophilic steroid backbone in trans-trans-trans conformation of the rings and a negatively charged mono-sulfate group at positions 3' or 17' with flexibility for α- or β- orientation. Furthermore, 5α-reduction, 16α-hydroxylation, and 17α-hydroxylation are acceptable for SOAT substrate recognition, whereas addition of a second negatively charged sulfate group seems to abolish substrate binding to SOAT, and so 17β-estradiol-3,17-disulfate is not transported by SOAT. Copyright © 2017 Elsevier Ltd. All rights reserved.

Hydrogen peroxide-induced reduction of delayed rectifier potassium current in hippocampal neurons involves oxidation of sulfhydryl groups.

PubMed

Hasan, Sonia M K; Redzic, Zoran B; Alshuaib, Waleed B

2013-07-03

This study examined the effect of H2O2 on the delayed rectifier potassium current (IKDR) in isolated hippocampal neurons. Whole-cell voltage-clamp experiments were performed on freshly dissociated hippocampal CA1 neurons of SD rats before and after treatment with H2O2. To reveal the mechanism behind H2O2-induced changes in IKDR, cells were treated with different oxidizing and reducing agents. External application of membrane permeable H2O2 reduced the amplitude and voltage-dependence of IKDR in a concentration dependent manner. Desferoxamine (DFO), an iron-chelator that prevents hydroxyl radical (OH) generation, prevented H2O2-induced reduction in IKDR. Application of the sulfhydryl-oxidizing agent 5,5 dithio-bis-nitrobenzoic acid (DTNB) mimicked the effect of H2O2. Sulfhydryl-reducing agents dithiothreitol (DTT) and glutathione (GSH) alone did not affect IKDR; however, DTT and GSH reversed and prevented the H2O2-induced inhibition of IKDR, respectively. Membrane impermeable agents GSH and DTNB showed effects only when added intracellularly identifying intracellular sulfhydryl groups as potential targets for hydroxyl-mediated oxidation. However, the inhibitory effects of DTNB and H2O2 at the positive test potentials were completely and partially abolished by DTT, respectively, suggesting an additional mechanism of action for H2O2, that is not shared by DTNB. In summary, this study provides evidence for the redox modulation of IKDR, identifies hydroxyl radical as an intermediate oxidant responsible for the H2O2-induced decrease in current amplitude and identifies intracellular sulfhydryl groups as an oxidative target. Copyright © 2013 Elsevier B.V. All rights reserved.

Production of high molecular weight polylactic acid

DOEpatents

Bonsignore, Patrick V.

1995-01-01

A degradable high molecular weight poly(lactic acid). A poly(lactic acid) has a terminal end group of one of carboxyl or hydroxyl groups with low molecular weight poly(lactic acid) units coupled with linking agents of di-isocyanates, bis-epoxides, bis-oxazolines and bis-ortho esters. The resulting high molecular weight poly(lactic acid) can be used for applications taking advantage of the improved physical properties.

Monkey liver cytochrome P450 2C19 is involved in R- and S-warfarin 7-hydroxylation.

PubMed

Hosoi, Yoshio; Uno, Yasuhiro; Murayama, Norie; Fujino, Hideki; Shukuya, Mitsunori; Iwasaki, Kazuhide; Shimizu, Makiko; Utoh, Masahiro; Yamazaki, Hiroshi

2012-12-15

Cynomolgus monkeys are widely used as primate models in preclinical studies. However, some differences are occasionally seen between monkeys and humans in the activities of cytochrome P450 enzymes. R- and S-warfarin are model substrates for stereoselective oxidation in humans. In this current research, the activities of monkey liver microsomes and 14 recombinantly expressed monkey cytochrome P450 enzymes were analyzed with respect to R- and S-warfarin 6- and 7-hydroxylation. Monkey liver microsomes efficiently mediated both R- and S-warfarin 7-hydroxylation, in contrast to human liver microsomes, which preferentially catalyzed S-warfarin 7-hydroxylation. R-Warfarin 7-hydroxylation activities in monkey liver microsomes were not inhibited by α-naphthoflavone or ketoconazole, and were roughly correlated with P450 2C19 levels and flurbiprofen 4-hydroxylation activities in microsomes from 20 monkey livers. In contrast, S-warfarin 7-hydroxylation activities were not correlated with the four marker drug oxidation activities used. Among the 14 recombinantly expressed monkey P450 enzymes tested, P450 2C19 had the highest activities for R- and S-warfarin 7-hydroxylations. Monkey P450 3A4 and 3A5 slowly mediated R- and S-warfarin 6-hydroxylations. Kinetic analysis revealed that monkey P450 2C19 had high V(max) and low K(m) values for R-warfarin 7-hydroxylation, comparable to those for monkey liver microsomes. Monkey P450 2C19 also mediated S-warfarin 7-hydroxylation with V(max) and V(max)/K(m) values comparable to those for recombinant human P450 2C9. R-warfarin could dock favorably into monkey P450 2C19 modeled. These results collectively suggest high activities for monkey liver P450 2C19 toward R- and S-warfarin 6- and 7-hydroxylation in contrast to the saturation kinetics of human P450 2C9-mediated S-warfarin 7-hydroxylation. Copyright © 2012 Elsevier Inc. All rights reserved.

Synthesis and crystal structure of the solid solution Co3(SeO3)3-x(PO3OH)x(H2O) involving crystallographic split positions of Se4+ and P5+.

PubMed

Zimmermann, Iwan; Johnsson, Mats

2013-10-21

Three new cobalt selenite hydroxo-phosphates laying in the solid solution Co3(SeO3)3-x(PO3OH)x(H2O), with x = 0.8, x = 1.0, and x = 1.2 are reported. Single crystals were obtained by hydrothermal synthesis and the crystal structure was determined by single crystal X-ray diffraction. The structure can be described as a 3D framework having selenite and hydroxo-phosphate groups protruding into channels in the crystal structure. Se(4+) and P(5+) share a split position in the structure so that either SeO3 groups having a stereochemically active lone pair or tetrahedrally coordinated PO3OH groups are present. The OH-group is thus only present when the split position is occupied by P(5+). The crystal water is coordinated to a cobalt atom and TG and IR measurements show that the water and hydroxyl groups leave the structure at unusually high temperatures (>450 °C). Magnetic susceptibility measurements show antiferromagnetic coupling below 16 K and a magnetic moment of 4.02(3) μB per Co atom was observed.

The effect of adenosine A(2A) receptor antagonists on hydroxyl radical, dopamine, and glutamate in the striatum of rats with altered function of VMAT2.

PubMed

Gołembiowska, Krystyna; Dziubina, Anna

2012-08-01

It has been shown that a decreased vesicular monoamine transporter (VMAT2) function and the disruption of dopamine (DA) storage is an early contributor to oxidative damage of dopamine neurons in Parkinson's disease (PD). In our previous study, we demonstrated that adenosine A(2A) receptor antagonists suppressed oxidative stress in 6-hydroxydopamine-treated rats suggesting that this effect may account for neuroprotective properties of drugs. In the present study, rats were injected with reserpine (10 mg/kg sc) and 18 h later the effect of the adenosine A(2A) receptor antagonists 8-(3-chlorostyryl)caffeine (CSC) and 4-(2-[7-amino-2-(2-furyl)[1,2,4]triazolo[2,3-a][1,3,5]triazin-5-ylamino]ethyl)phenol (ZM 241385) on extracellular DA, glutamate and hydroxyl radical formation was studied in the rat striatum using in vivo microdialysis. By disrupting VMAT2 function, reserpine depleted DA stores, and increased glutamate and hydroxyl radical levels in the rat striatum. CSC (1 mg/kg) but not ZM 241385 (3 mg/kg) increased extracellular DA level and production of hydroxyl radical in reserpinised rats. Both antagonists decreased the reserpine-induced increase in extracellular glutamate. L-3,4-Dihydroxyphenylalanine (L-DOPA) (25 mg/kg) significantly enhanced extracellular DA, had no effect on reserpine-induced hydroxyl radical production and decreased extracellular glutamate concentration. CSC but not ZM 241385 given jointly with L-DOPA increased the effect of L-DOPA on extracellular DA and augmented the reserpine-induced hydroxyl radical production. CSC and ZM 241385 did not influence extracellular glutamate level, which was decreased by L-DOPA. It seems that by decreasing the MAO-dependent DA metabolism rate, CSC raised cytosolic DA and by DA autoxidation, it induced hydroxyl radical overproduction. Thus, the methylxanthine A(2A) receptor antagonists bearing properties of MAO-B inhibitor, like CSC, may cause a risk of oxidative stress resulting from dysfunctional DA storage mechanism in early PD.

Proteomic analysis reveals diverse proline hydroxylation-mediated oxygen-sensing cellular pathways in cancer cells

PubMed Central

Liu, Bing; Gao, Yankun; Ruan, Hai-Bin; Chen, Yue

2016-01-01

Proline hydroxylation is a critical cellular mechanism regulating oxygen-response pathways in tumor initiation and progression. Yet, its substrate diversity and functions remain largely unknown. Here, we report a system-wide analysis to characterize proline hydroxylation substrates in cancer cells using an immunoaffinity-purification assisted proteomics strategy. We identified 562 sites from 272 proteins in HeLa cells. Bioinformatic analysis revealed that proline hydroxylation substrates are significantly enriched with mRNA processing and stress-response cellular pathways with canonical and diverse flanking sequence motifs. Structural analysis indicates a significant enrichment of proline hydroxylation participating in the secondary structure of substrate proteins. Our study identified and validated Brd4, a key transcription factor, as a novel proline hydroxylation substrate. Functional analysis showed that the inhibition of proline hydroxylation pathway significantly reduced the proline hydroxylation abundance on Brd4 and affected Brd4-mediated transcriptional activity as well as cell proliferation in AML leukemia cells. Taken together, our study identified a broad regulatory role of proline hydroxylation in cellular oxygen-sensing pathways and revealed potentially new targets that dynamically respond to hypoxia microenvironment in tumor cells. PMID:27764789

Mesoporous silica film from a solution containing a surfactant and methods of making same

DOEpatents

Liu, Jun [West Richland, WA; Domansky, Karel [Cambridge, MA; Li, Xiaohong [Richland, WA; Fryxell, Glen E [Kennewick, WA; Baskaran, Suresh [Kennewick, WA; Kohler, Nathan J [Richland, WA; Thevuthasan, Suntharampillai [Kennewick, WA; Coyle, Christopher A [Richland, WA; Birnbaum, Jerome C [Richland, WA

2001-12-11

The present invention is a mesoporous silica film having a low dielectric constant and method of making having the steps of combining a surfactant in a silica precursor solution, spin-coating a film from this solution mixture, forming a partially hydroxylated mesoporous film, and dehydroxylating the hydroxylated film to obtain the mesoporous film. It is advantageous that the small polyoxyethylene ether surfactants used in spin-coated films as described in the present invention will result in fine pores smaller on average than about 20 nm. The resulting mesoporous film has a dielectric constant less than 3, which is stable in moist air with a specific humidity. The present invention provides a method for superior control of film thickness and thickness uniformity over a coated wafer, and films with low dielectric constant.

The Synthesis of Methyl Salicylate: Amine Diazotization.

ERIC Educational Resources Information Center

Zanger, Murray; McKee, James R.

1988-01-01

Notes that this experiment takes safety and noncarcinogenic reactants into account. Demonstrates the use of diazonium salts for the replacement of an aromatic amine group by a phenolic hydroxyl. Involves two pleasant-smelling organic compounds, methyl anthranilate (grape) and methyl salicylate (oil of wintergreen). (MVL)

A NEW NON-AMBIGUOUS ANALYTICAL TECHNIQUE FOR THE IDENTIFICATION OF AEROSOL OXYGENATED COMPOUNDS

EPA Science Inventory

The most important organic products identified in the particle phase from field samples and from smog chamber experiments are polar oxygenated compounds containing one, two, three or more oxygenated functional groups (e.g. hydroxyl, carboxylic acid, ketone). Current procedures ...

A Gas-Liquid Chromatographic Examination of Stilbene Derivatives

Treesearch

Richard W. Hemingway; W. E. Hillis; K Burerton

1970-01-01

Trimethylsilyl ether derivatives of twenty hydroxystilbenes were separated by gas-liquid chromatography on Apiezon-L, OV-1, OV-17, and SE-54. Relative retention times were highly dependent upon the degree of hydroxylation and methoxylation, the positions of these groups and on cis-trans...

Investigation of the degradation of cresols in the treatments with ozone

EPA Science Inventory

The reaction between ozone and the three cresol isomers was investigated in pure water. Cresols were selected as model substrates representing an important component of humic material. Cresols carry both a hydroxyl and a methyl group, each theoretically increasing the reactivity ...

Low-energy collisionally activated dissociation of pentose-borate complexes

NASA Astrophysics Data System (ADS)

Pepi, Federico; Garzoli, Stefania; Tata, Alessandra; Giacomello, Pierluigi

2010-01-01

Pentose-borate 1:1 complexes were generated in the ESI source of a triple quadrupole and ion trap mass spectrometer by electrospray ionization of Na2B4O7 and pentose (arabinose, lyxose, ribose, xylose) 2:1 solution in CH3CN/H2O. The study of their low-energy collisionally activated dissociation (CAD) demonstrated that ribose and lyxose are preferentially complexed at the C2-C3 cis-diol function whereas arabinose and xylose are esterified at the C1-C2 hydroxyl groups. No evidence was found of the stronger affinity for ribose to borate. The ribose probiotic rule can be explained by considering its peculiar capability, among the investigated pentoses, to almost totally complex the borate anion at the C2-C3 hydroxyl group, thus enabling the subsequent stages of nucleotide assembly, such as phosphorylation and linkage to the nucleobases. Finally, the differences observed in the pentose-borate complex CAD spectra can be used for the mass spectrometric discrimination of isomeric pentoses in complex mixtures.

Understanding Defect-Stabilized Noncovalent Functionalization of Graphene

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhou, Hua; Uysal, Ahmet; Anjos, Daniela M.

2015-09-01

The noncovalent functionalization of graphene by small molecule aromatic adsorbates, phenanthrenequinone (PQ), is investigated systematically by combining electrochemical characterization, high-resolution interfacial X-ray scattering, and ab initio density functional theory calculations. The findings in this study reveal that while PQ deposited on pristine graphene is unstable to electrochemical cycling, the prior introduction of defects and oxygen functionality (hydroxyl and epoxide groups) to the basal plane by exposure to atomic radicals (i.e., oxygen plasma) effectively stabilizes its noncovalent functionalization by PQ adsorption. The structure of adsorbed PQ molecules resembles the graphene layer stacking and is further stabilized by hydrogen bonding with terminalmore » hydroxyl groups that form at defect sites within the graphene basal plane. The stabilized PQ/graphene interface demonstrates persistent redox activity associated with proton-coupled-electron-transfer reactions. The resultant PQ adsorbed structure is essentially independent of electrochemical potentials. These results highlight a facile approach to enhance functionalities of the otherwise chemically inert graphene using noncovalent interactions.« less

Heterophase-structured nanocrystals as superior supports for Ru-based catalysts in selective hydrogenation of benzene

PubMed Central

Peng, Zhikun; Liu, Xu; Li, Shuaihui; Li, Zhongjun; Li, Baojun; Liu, Zhongyi; Liu, Shouchang

2017-01-01

ZrO2 heterophase structure nanocrystals (HSNCs) were synthesized with tunable ratios of monoclinic ZrO2 (m-ZrO2) to tetragonal ZrO2 (t-ZrO2). The phase mole ratio of m-ZrO2 versus t-ZrO2 in ZrO2 HSNCs was tuned from 40% to 100%. The concentration of the surface hydroxyl groups on m-ZrO2 is higher than that on t-ZrO2. ZrO2 HSNCs have different surface hydroxyl groups on two crystalline phases. This creates more intimate synergistic effects than their single-phase counterparts. The ZrO2 HSNCs were used as effective supports to fabricate heterophase-structured Ru/ZrO2 catalysts for benzene-selective hydrogenation. The excellent catalytic performance including high activity and selectivity is attributed to the heterogeneous strong/weak hydrophilic interface and water layer formed at the m-ZrO2/t-ZrO2 catalyst junction. PMID:28057914

Understanding Defect-Stabilized Noncovalent Functionalization of Graphene

DOE PAGES

Zhou, Hua; Uysal, Ahmet; Anjos, Daniela M.; ...

2015-09-01

For the noncovalent functionalization of graphene by small molecule aromatic adsorbates, phenanthrenequinone (PQ), is investigated systematically by combining electrochemical characterization, high-resolution interfacial X-ray scattering, and ab initio density functional theory calculations. The fi ndings in this study reveal that while PQ deposited on pristine graphene is unstable to electrochemical cycling, the prior introduction of defects and oxygen functionality (hydroxyl and epoxide groups) to the basal plane by exposure to atomic radicals (i.e., oxygen plasma) effectively stabilizes its noncovalent functionalization by PQ adsorption. Moreover, the structure of adsorbed PQ molecules resembles the graphene layer stacking and is further stabilized by hydrogenmore » bonding with terminal hydroxyl groups that form at defect sites within the graphene basal plane. The stabilized PQ/graphene interface demonstrates persistent redox activity associated with proton-coupled-electron-transfer reactions. The resultant PQ adsorbed structure is essentially independent of electrochemical potentials. Finally, these results highlight a facile approach to enhance functionalities of the otherwise chemically inert graphene using noncovalent interactions.« less

A synthetic chalcone as a potent inducer of glutathione biosynthesis.

PubMed

Kachadourian, Remy; Day, Brian J; Pugazhenti, Subbiah; Franklin, Christopher C; Genoux-Bastide, Estelle; Mahaffey, Gregory; Gauthier, Charlotte; Di Pietro, Attilio; Boumendjel, Ahcène

2012-02-09

Chalcones continue to attract considerable interest due to their anti-inflammatory and antiangiogenic properties. We recently reported the ability of 2',5'-dihydroxychalcone (2',5'-DHC) to induce both breast cancer resistance protein-mediated export of glutathione (GSH) and c-Jun N-terminal kinase-mediated increased intracellular GSH levels. Herein, we report a structure-activity relationship study of a series of 30 synthetic chalcone derivatives with hydroxyl, methoxyl, and halogen (F and Cl) substituents and their ability to increase intracellular GSH levels. This effect was drastically improved with one or two electrowithdrawing groups on phenyl ring B and up to three methoxyl and/or hydroxyl groups on phenyl ring A. The optimal structure, 2-chloro-4',6'-dimethoxy-2'-hydroxychalcone, induced both a potent NF-E2-related factor 2-mediated transcriptional response and an increased formation of glutamate cysteine ligase holoenzyme, as shown using a human breast cancer cell line stably expressing a luciferase reporter gene driven by antioxidant response elements.

A Synthetic Chalcone as a Potent Inducer of Glutathione Biosynthesis

PubMed Central

Kachadourian, Remy; Day, Brian J.; Pugazhenti, Subbiah; Franklin, Christopher C.; Genoux-Bastide, Estelle; Mahaffey, Gregory; Gauthier, Charlotte; Di Pietro, Attilio; Boumendjel, Ahcène

2014-01-01

Chalcones continue to attract considerable interest due to their anti-inflammatory and antiangiogenic properties. We recently reported the ability of 2′,5′-dihydroxychalcone (2′,5′-DHC) to induce both breast cancer resistance protein-mediated export of glutathione (GSH) and c-Jun N-terminal kinase-mediated increased intracellular GSH levels. Herein, we report a structure–activity relationship study of a series of 30 synthetic chalcone derivatives with hydroxyl, methoxyl, and halogen (F and Cl) substituents and their ability to increase intracellular GSH levels. This effect was drastically improved with one or two electrowithdrawing groups on phenyl ring B and up to three methoxyl and/or hydroxyl groups on phenyl ring A. The optimal structure, 2-chloro-4′,6′-dimethoxy-2′-hydroxychalcone, induced both a potent NF-E2-related factor 2-mediated transcriptional response and an increased formation of glutamate cysteine ligase holoenzyme, as shown using a human breast cancer cell line stably expressing a luciferase reporter gene driven by antioxidant response elements. PMID:22239485

Evolution of novel O-methyltransferases from the Vanilla planifolia caffeic acid O-methyltransferase.

PubMed

Li, Huaijun Michael; Rotter, David; Hartman, Thomas G; Pak, Fulya E; Havkin-Frenkel, Daphna; Belanger, Faith C

2006-06-01

The biosynthesis of many plant secondary compounds involves the methylation of one or more hydroxyl groups, catalyzed by O-methyltransferases (OMTs). Here, we report the characterization of two OMTs, Van OMT-2 and Van OMT-3, from the orchid Vanilla planifolia Andrews. These enzymes catalyze the methylation of a single outer hydroxyl group in substrates possessing a 1,2,3-trihydroxybenzene moiety, such as methyl gallate and myricetin. This is a substrate requirement not previously reported for any OMTs. Based on sequence analysis these enzymes are most similar to caffeic acid O-methyltransferases (COMTs), but they have negligible activity with typical COMT substrates. Seven of 12 conserved substrate-binding residues in COMTs are altered in Van OMT-2 and Van OMT-3. Phylogenetic analysis of the sequences suggests that Van OMT-2 and Van OMT-3 evolved from the V. planifolia COMT. These V. planifolia OMTs are new instances of COMT-like enzymes with novel substrate preferences.

Comparative study of wet and dry torrefaction of corn stalk and the effect on biomass pyrolysis polygeneration.

PubMed

Wang, Xianhua; Wu, Jing; Chen, Yingquan; Pattiya, Adisak; Yang, Haiping; Chen, Hanping

2018-06-01

Wet torrefaction (WT) possesses some advantages over dry torrefaction (DT). In this study, a comparative analysis of torrefied corn stalk from WT and DT was conducted along with an investigation of their pyrolysis properties under optimal conditions for biomass pyrolysis polygeneration. Compared with DT, WT removed 98% of the ash and retained twice the amount of hydrogen. The impacts of DT and WT on the biomass macromolecular structure was also found to be different using two-dimensional perturbation correlation infrared spectroscopy (2D-PCIS). WT preserved the active hydroxyl groups and rearranged the macromolecule structure to allow cellulose to be more ordered, while DT removed these active hydroxyl groups and formed inter-crosslinking structures in macromolecules. Correspondingly, the bio-char yield after WT was lower than DT but the bio-char quality was upgraded due to high ash removal. Furthermore, higher bio-oil yield, higher sugar content, and higher H 2 generation, were obtained after WT. Copyright © 2018 Elsevier Ltd. All rights reserved.