Degree Of Hydroxylation Research Articles

Regional differences in biochemical, biomechanical and histomorphological characteristics of the equine suspensory ligament

Desmopathies of the suspensory ligament are relatively frequent and vary in prevalence over different anatomical regions. This variation may be because of regional differences in tissue characteristics. To characterise different regions of healthy forelimb suspensory ligaments (SLs) by means of biochemical, biomechanical and histomorphological techniques. There is substantial topographical heterogeneity in the SL with respect to structural, compositional and functional characteristics. SLs were harvested from 38 limbs and used for biochemical (n = 20), biomechanical (n = 14) and histomorphological (n = 4) evaluation. Sulphated glycosaminoglycan (S-GAG), DNA and collagen content, degree of lysyl hydroxylation and numbers of enzymatic and nonenzymatic cross-links were determined in 7 regions of the SL: lateral and medial part of the origin (OM, OL), mid-body (MB), axial and abaxial parts of the lateral and medial branches (ILAX, ILAB, IMAX and IMAB, respectively). Passive resistance to tensile loading was measured in 5 regions of the SL (all except OL and OM). DNA content was lower in OL and OM than in all other parts. GAG content was also lower in OL and OM and highest in ILAB and IMAB. Collagen content was lower in OL/OM and highest in ILAX/IMAX. Pentosidine levels were highest in OL and significantly lower in the lateral insertion (ILAX/ILAB). There were no differences in hydroxylysylpyridinoline (HP) cross-links or lysyl hydroxylation. Stiffness (P<0.01) and modulus of elasticity (P<0.01) were substantially higher in the MB region than in all other regions except for IMAB. Strain at failure was lower in the MB region (P<0.0001), resulting in a comparable force at rupture as in the other regions. Matrix composition differs to a relatively limited extent between different regions of the SL. The mid-body of the ligament is stiffer than the branches, which have similar properties and relevance and mechanical differences between mid-body and branches/origin may explain some use-related differences in the prevalence of lesions.

Simulating Fasted Human Intestinal Fluids: Understanding the Roles of Lecithin and Bile Acids

The purpose of this work is to evaluate the roles of lecithin and bile salts in a new generation of fasted simulated small intestinal fluid (FaSSIF-II), thus enhancing the closer mimic of simulated fluids to the real human intestinal fluids (HIF) in drug discovery and drug product development. To assess the effects of lecithin in FaSSIF-II, solubility studies were conducted at 37 °C using four media including first generation simulated intestinal fluid (FaSSIF-I), FaSSIF-II, phosphate pH 6.5 buffer, and HIF. A total of 24 model compounds representing a wide range of biopharmaceutic properties were included. The drug solubility values measured in the FaSSIF-II were compared with those in FaSSIF-I, pH 6.5 buffer and HIF. To assess the effects of bile acids, solubility was measured for 4 compounds in the FaSSIF-I containing five different bile acids of various concentrations. The lecithin concentration in the FaSSIF-II is lowered from 0.75 mM to 0.2 mM. The results suggested that the FaSSIF-II is a better medium to reflect HIF, compared with pH 6.5 phosphate buffer and FaSSIF-I. Solubility of neutral compounds including atovaquone, carbamazepine, cyclosporine, danazol, diethylstilbestrol, felodipine, griseofulvin and probucol in FaSSIF-II showed improvement in predicting the in vivo solubility. The relative standard deviation (SD) of solubility measurement in FaSSIF-II is comparable with FaSSIF-I. For the acidic and basic tested compounds, the FaSSIF-II performs similarly to the FaSSIF-I. Experimental results showed that the level of bile salts typically is less than 5 mM under fasted state. Among the five studied bile acids, the conjugation (glycine or taurine) has no impact on the drug solubilization, while there may be a minimal effect of the degree of hydroxylation of the steroid ring system on solubilization. The lecithin concentration of 0.2 mM in FaSSIF-II has been demonstrated to closely represent HIF, for both neutral and ionizable compounds. In the composition of simulated intestinal fluids, the structure of bile acids has minimal effect, providing the flexibility of choosing one bile salt to represent complex in vivo bile acids.

Heterogeneities in Fullerene Nanoparticle Aggregates Affecting Reactivity, Bioactivity, and Transport

Properties of nanomaterial suspensions are typically summarized by average values for the purposes of characterizing these materials and interpreting experimental results. We show in this work that the heterogeneity in aqueous suspensions of fullerene C(60) aggregates (nC(60)) must be taken into account for the purposes of predicting nanomaterial transport, exposure, and biological activity. The production of reactive oxygen species (ROS), microbial inactivation, and the mobility of the aggregates of the nC(60) in a silicate porous medium all increased as suspensions were fractionated to enrich with smaller aggregates by progressive membrane filtration. These size-dependent differences are attributed to an increasing degree of hydroxylation of nC(60) aggregates with decreasing size. As the quantity and influence of these more reactive fractions may increase with time, experiments evaluating fullerene transport and toxicity end points must take into account the evolution and heterogeneity of fullerene suspensions.

La0.8Sr0.2Ga0.8Fe0.2O3−δ: Influence of the preparation procedure on reactivity toward methanol and ethanol

In this paper a strontium- and iron-doped lanthanum gallate (La0.8Sr0.2Ga0.8Fe0.2O3—LSGF) is prepared by Pechini process and polyacrylamide gel method. The powders are characterized by means of X-ray Diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), Diffuse Reflectance Infrared Fourier Transform spectroscopy (DRIFT), Thermal Programmed Desorption (TPD), Thermal Programmed Reduction (TPR), BET specific surface area, UV–Vis and Mössbauer Spectroscopy (MS). The activity toward methanol and ethanol is investigated by Infrared (IR) spectroscopy and Quadrupolar Mass Spectrometry (QMS) under several conditions. XRD outcomes reveal the formation of the desired perovskite phase at 900°C, however, small amounts of secondary phases are also present. LSGF synthesized by Pechini process is characterized by a lower amount of secondary phases. On the other hand, LSGF from polyacrylamide gel method has a higher specific surface area. XPS data show that the two samples differ for surface cations segregation, hydroxylation degree and carbonate contamination. These results are also confirmed by DRIFT and TPD measurements. MS and TPR analyses reveal the presence of a small amount of Fe(IV), which is reduced to Fe(III) with H2 (5% in Ar) at about 450°C and with CH3OH vapours at 200°C. Catalytic tests prove that methanol is mainly decomposed into H2 and CO at 400°C, but small amounts of CO2 are also detected. Ethanol undergoes essentially dehydrogenation thus forming acetaldehyde and H2. In oxidizing conditions, both alcohols are oxidized to CO2 and H2O at 400°C, nevertheless, partially oxidized products are also observed. Acetaldehyde is an important product in ethanol oxidation. Under steam reforming conditions, methanol and ethanol give H2, CO and CO2, but acetaldehyde is also observed in ethanol steam reforming. The presence of acetaldehyde, when dealing with ethanol, suggests a difficult C–C bond break. Both the LSGF samples undergo poisoning during the reactions.

The effect of water on particle size, porosity and the rate of drug release from implanted titania reservoirs

The implantation of controlled drug release devices represents a new strategy in the treatment of neurodegenerative disorders. Sol-gel titania implants filled with valproic acid, have been used for this purpose to treat induced epilepsy in rats. The kinetics of the drug release depend on: (a) porosity, (b) chemical interactions between valproic acid and surface hydroxyl groups of titania, (c) particle size, and (d) particle size agglomerates. The concentration of water used in the hydrolysis reaction is an important variable in the degree of porosity, hydroxylation, and structural defects of the nanostructured titanium oxide reservoir. The titanium n-butoxide/water ratio was systematically varied during the sol-gel synthesis, while maintaining the amount of valproic acid constant. Characterization studies were performed using DTA-TGA, FTIR, Raman, TEM, SEM, BET, and in vitro release kinetic measurements. The particle agglomerate size and porosity were found to depend on the amount of water used in the sol-gel reaction.

Non‐destructive investigation of fibronectin adsorption on titanium surfaces using PM‐RAIRS: effect of surface hydroxylation

AbstractPolarisation‐modulation reflection‐absorption infrared spectroscopy (PM‐RAIRS) is a useful non‐destructive technique to study semi‐quantitatively the adsorption of proteins on metal surfaces. In this work, we employed PM‐RAIRS to study the effect of the degree of hydroxylation of the surface of titanium metal sheets, obtained by specific acidic or basic treatments, on the adsorption of fibronectin, a model plasma adhesion protein. Our results seem to indicate that the degree of hydroxylation does not influence significantly the adhesion properties of fibronectin, which is one of the main steps in titanium osseointegration process. Copyright © 2010 John Wiley &amp; Sons, Ltd.

Enhanced Stability of Gold Clusters Supported on Hydroxylated MgO(001) Surfaces

The influence of surface hydroxylation on nucleation and sintering of gold nanoparticles was studied by comparison of Au deposition and thermal sintering on ideally terminated MgO(001) and hydroxylated MgO thin films, respectively. A combination of different spectroscopic techniques (TDS, XPS, IRAS) allows to establish a correlation between the degree of surface hydroxylation and the stability of gold atoms and clusters. Hydroxyl groups destabilize gold atoms on the MgO surface at 90 K; however, they enhance the stability of small gold clusters toward sintering at higher temperature.

Selectivity problem of metal oxide based sensors in the presence of water vapors

We report our recent results on comparative analysis of sensing properties for two-component nanodispersed oxide systems: SnO2–MetOx (Met=Ti, Zr, Hf, Y and La) and SnO2-noble metals (Pt, Pd, Rh). The sensor signals towards 20 ppm H2 as a function of temperature (50–550∘C) and ambient humidity (0, 20, 50 and 80% RH at 25∘C) were compared in the light of surface hydroxylation degree, estimated by FTIR and TGA. Poor selectivity of SnO2 doped with noble metals was found and explained by interaction of H2 and H2O with the same surface species (most probably surface oxygen). Rather good selectivity of blank SnO2 and SnO2–MetOx (especially doped with IVB elements) seems to be related with H2 interaction with surface hydroxyls, which are supposed to be inactive for direct water chemisorption.

Grafting of a hydroxylated poly(ether ether ketone) to the surface of single-walled carbon nanotubes

A hydroxylated poly(ether ether ketone) (HPEEK) derivative has been covalently grafted onto the surface of acid-treated single-walled carbon nanotubes (SWCNTs) following two different esterification approaches. The hydroxylation degree of the HPEEK and the extent of the grafting reactions were determined by thermogravimetric analysis. Microscopic observations revealed an increase in the bundle diameter of the SWCNTs and the heterogeneous composition of the synthesized samples. Infrared, nuclear magnetic resonance and X-ray photoelectron spectra corroborated the grafting success, showing the appearance of signals associated with the ester group. The polymer-grafted SWCNTs display higher decomposition temperatures and a wider range of thermal degradation than the HPEEK. The esterification decreases the crystallization and melting temperature as well as the crystallinity of the HPEEK. The semicrystalline nature of the grafted samples was confirmed by X-ray diffraction analysis, which reveals a diminution in the crystal size of the polymer. Dynamic mechanical studies show an exceptional increase in the storage modulus and glass transition temperature of the polymer by the attachment to the SWCNTs. Slightly better thermal and mechanical properties are observed for the sample with the higher esterification degree. The HPEEK-grafted SWCNTs can be used as fillers to prepare PEEK nanocomposites with enhanced performance.

Carboxymethylated-κ-casein: A convenient tool for the identification of polyphenolic inhibitors of amyloid fibril formation

Reduced and carboxymethylated-κ-casein (RCM-κ-CN) is a milk-derived amyloidogenic protein that readily undergoes nucleation-dependent aggregation and amyloid fibril formation via a similar pathway to disease-specific amyloidogenic peptides like amyloid beta (Aβ), which is associated with Alzheimer’s disease. In this study, a series of flavonoids, many known to be inhibitors of Aβ fibril formation, were screened for their ability to inhibit RCM-κ-CN fibrilisation, and the results were compared with literature data on Aβ inhibition. Flavonoids that had a high degree of hydroxylation and molecular planarity gave good inhibition of RCM-κ-CN fibril formation. IC 50 values were between 10- and 200-fold higher with RCM-κ-CN than literature results for Aβ fibril inhibition, however, with few exceptions, they showed a similar trend in potency. The convenience and reproducibility of the RCM-κ-CN assay make it an economic alternative first screen for Aβ inhibitory activity, especially for use with large compound libraries.

Dynamic Behavior of Interfacial Water at the Silica Surface

Molecular dynamics simulations were employed to study the dynamic properties of water at the silica−liquid interface at ambient temperature. Three different degrees of hydroxylation of a crystalline silica surface were used. To assess the water dynamic properties we calculated the residence probability and in-plane mean-square displacement as a function of distance from the surface. The data indicate that water molecules at the fully hydroxylated surface remain longer, on average, in the interfacial region than in the other cases. By assessing the dynamics of molecular dipole moment and hydrogen−hydrogen vector an anisotropic reorientation was discovered for interfacial water in contact with any of the surfaces considered. However, the features of the anisotropic reorientation observed for water molecules depend strongly on the relative orientation of interfacial water molecules and their interactions with surface hydroxyl groups. On the partially hydroxylated surface, where water molecules with hydrogen-...

CHARACTERIZATION AND COMPARISON OF COLLAGENS EXTRACTED FROM THE DIGESTIVE TRACT AND SKIN OF A JAPANESE AMBERJACK SERIOLA QUINQUERADIATA

ABSTRACT Collagen was extracted from the digestive tract and skin of a Japanese amberjack (Seriola quinqueradiata) by acid extraction and limited pepsin digestion. The amounts of collagen solubilized from the digestive tract were smaller than those from the skin. Based on the solubility in NaCl solution, electrophoretic and peptide map patterns, and amino acid composition, the main digestive tract collagen was identified as type I, having characteristics different from those of the body wall collagen in cyclostome intestine. Further, the degree of hydroxylation of prolyl and lysyl residues in the type I collagen of the digestive tract is significantly higher than that of the skin. Collagen preparations from the digestive tract have a higher ratio of type V collagen than those from the skin. Hence, the digestive tract collagen differs from that in the skin in the degree or property of intermolecular crosslinking, posttranslational modification, and molecular species composition. PRACTICAL APPLICATIONS Partial hydrolyzate of gelatin, in other word collagen peptide, has gained popularity as a food ingredient, as it has been suggested to have health benefits, such as improvement of skin and joint conditions. Recently, attention toward collagen derived from marine origin such as fish skin increased because of the outbreak of bovine spongiform encephalopathy. Large amounts of the digestive tract, stomach, intestine and adhesion tissues are generated by fishery industries and most of them are by-products of low value. Although these organs are also rich in collagen, the collagen in fish digestive tract has not been characterized. The present study demonstrates that the collagen in digestive tract differs from the skin collagen in the solubility, posttranslational modification and molecular species composition. These facts suggest that modified collagen peptides might be obtained from the digestive tract.

Synthesis and Characterization of Poly(ether ether ketone) Derivatives Obtained by Carbonyl Reduction

Hydroxylated poly(ether ether ketone) (PEEK-OH) samples, with different degrees of functionalization, have been synthesized by selective carbonyl reduction. The ATR-FTIR and NMR spectra corroborated the reduction success, showing a decrease in the intensity of the peaks related to the ketone group and simultaneously the appearance of new signals associated with the hydroxyl group. TGA curves indicated a reduction in thermal stability with increasing hydroxylation degree (HD), attributed to changes in the spatial organization of the molecules and a less intense resonance effect. DSC experiments showed a progressive diminution in the crystallization and melting temperatures as the number of hydroxyl groups increased due to the restrictions on polymer chain diffusion imposed by the strong hydrogen bonds. Furthermore, the level of crystallinity of the derivatives drastically decreased upon increasing HD, as evidenced from the X-ray diffraction spectra. The random distribution of this functional group inhibits the molecular packing, leading to the formation of smaller and less perfect crystals. DMA studies revealed a decrease in both storage and loss moduli as the extent of modification increased. However, the presence of the hydroxyl group caused a significant improvement in the glass transition temperatures of the polymers, particularly at higher degree of functionalization, where the increment was close to 40 °C. Such enhancement is attributed to a decrease in mobility and flexibility induced by the strong intermolecular interactions between the chains.

Friction between α-Al 2O 3(0 0 0 1) surfaces and the effects of surface hydroxylation

Molecular dynamics simulations were performed to study the friction between hydroxylated α-Al 2O 3(0 0 0 1) surfaces at the temperature of 300 K. Effects of the degree of surface hydroxylation and sliding velocity have been discussed. Results indicate that the friction coefficient decreases with increased degrees of hydroxylation. For all degrees of surface hydroxylation, the friction law crosses over from thermal activation to viscous damping at sliding velocity of 80 m/s.

Pathways of advanced oxidation of phenol by Fenton's reagent—Identification of oxidative coupling intermediates by extractive acetylation

Homogeneous Fenton reaction (H 2O 2/Fe 2+ system) using significantly substoichiometric concentrations of H 2O 2 oxidant to oxidize phenol was characterized focusing on the formation of stable aromatic intermediates. Beyond the most abundant benzenediols, the pattern of aromatic intermediates was chiefly characterized by hydroxylated biphenyls and diphenyl ethers with different degrees of hydroxylation. Hydroxylated dibenzofurans (DBF), p,p′-dioxins, as well as highly condensed aromatic intermediates including polyols of polycyclic aromatic hydrocarbons (PAHs), could also be detected, but in lower concentrations. The formation of aromatic intermediates could be predicted on the basis of oxidative coupling reactions of resonance-stabilized radicals generated by the attack of the highly reactive hydroxyl radicals (OH*) on phenol. GC/MS identification of oxidative coupling intermediates was performed after derivatization of the solvent extracts. Derivatization reactions included silylation to give TMS (trimethylsilyl) ethers, as well as single-step extractive acetylation using acetic anhydride in alkaline aqueous solutions (pH 10.5) to give acetates. Solvent extraction of aqueous solutions, a prerequisite to generate TMS ethers, caused strong discrimination of polyols due to their low distribution coefficients in non-polar solvents. This discrimination could be overcome by extracting the in-situ formed acetates of the intermediates. Extractive acetylation allowed the detection of tri-, tetra-, and penta-hydroxylated aromatic intermediates generated by Fenton oxidation processes, which have been overlooked upto now. Thus, extractive acetylation to detect stable aromatic intermediates covering a wide range of hydroxylation degrees can foster the understanding, monitoring, and management of advanced oxidation processes, especially in the field of wastewater treatment.

Hydration Structure on Crystalline Silica Substrates

The structure of interfacial water at the silica solid surfaces was investigated using molecular dynamics simulations. Different degrees of surface hydroxylation were employed to assess the effect of the surface chemistry on the structure of interfacial water. Density profiles, in-plane radial distribution functions, in-plane density distribution, and hydrogen-bond profiles were calculated. Our results show that the surface hydroxylation affects the structure, orientation, and hydrogen-bond network of interfacial water molecules. Data analysis suggests that the degree of hydroxylation controls the amount of water molecules in the first interfacial layer as well as the distance between the first adsorbed layer and the substrate. Well-organized and uniform structures of interfacial water appear on the homogeneously hydroxylated surface, while a heterogeneous interfacial structure, characterized by extensive water-water hydrogen bonds, forms on the partially hydroxylated surface. We demonstrate that both the local surface chemistry and water-water hydrogen bonds are the dominant factors that determine the structural properties of interfacial water.

Colour, pH stability and antioxidant activity of anthocyanin rutinosides isolated from tamarillo fruit (Solanum betaceum Cav.)

Abstract Changes in colour and stability of anthocyanins have been evaluated over pH range 2.0–8.7. The study was made on crude extract (XAD-7 Amberlite-retained fraction) as well as on the following pure pigments isolated from tamarillo fruit ( Solanum betaceum Cav.): delphinidin 3- O -(6″- O -α-rhamnopyranosyl-β-glucopyranosyl)-3′- O -β-glucopyranoside, delphinidin 3- O -(6″- O -α-rhamnopyranosyl)-β-glucopyranoside, cyanidin 3- O -(6″- O -α-rhamnopyranosyl)-β-glucopyranoside and pelargonidin 3- O -(6″- O -α-rhamnopyranosyl)-β-glucopyranoside. The relationships between the colour and the hydroxylation degree of the B ring and the pH have been studied for the first time on rutinosides. The peel extract showed much more colour stability than the jelly extract at all the pH values studied. The replacement of the 3′-OH with a glycosyl group increased the stability of the colour to pH changes, although this substitution yields a less colourful (higher L ∗ and lower C ab ∗ ) compound (Dp 3-rut-3′-glc), having both hypsochromic and hypochromic shifts relative to the non-glycosylated molecule (Dp 3-rut). Moreover, the influence of the hydroxylation degree of the B ring on the quality and stability of colour, as well as on the antioxidant activity, was determined.

Biomineralization process of calcium phosphate: Modulation of the poly-amino acid with different hydroxyl/carboxyl ratios

Organic species are thought to exert an important effect on the formation of the mineral materials by their electrostatic attraction with the cations of minerals. In this work, a series of polyaspartic acids with different hydroxylation degrees (PAsp- x%OH) have been used as crystal growth modifiers to direct the synthesis of calcium phosphate. The change of x in the PAsp- x%OH can precisely adjust its electrostatic interaction with calcium ions and, thereby, modulate the formation process and property of calcium phosphate, such as morphology, crystallinity, organic component content and calcium-to-phosphate ratio. Two competitive reactions are suggested in this system, that is, the combination of calcium ions to PAsp- x%OH and the precipitation of calcium hydrogen phosphate dihydrate. The trends of these two reactions are determined by variation of x in the PAsp- x%OH: lower value of x tends to involve the former, while the higher tends to latter. It has been found that the mineralization process involving PAsp-15%OH displayed a special point to counterbalance the two competitive reactions, leading to the longest induction time. These findings indicate that how an organic species controls the morphology and the formation dynamics of inorganic crystals in biomineralization by the slight modification of its molecular structure.

Structure, stability, depolarized light scattering, and vibrational spectra of fullerenols from all-electron density-functional-theory calculations

We have investigated the stability, electronic properties, Rayleigh (elastic), and Raman (inelastic) depolarization ratios, infrared and Raman absorption vibrational spectra of fullerenols $[{\mathrm{C}}_{60}{(\mathrm{O}\mathrm{H})}_{n}]$ with different degrees of hydroxylation by using all-electron density-functional-theory (DFT) methods. Stable arrangements of these molecules were found by means of full geometry optimizations using Becke's three-parameter exchange functional with the Lee, Yang, and Parr correlation functional. This DFT level has been combined with the $6\text{\ensuremath{-}}31\mathrm{G}(d,p)$ Gaussian-type basis set, as a compromise between accuracy and capability to treat highly hydroxylated fullerenes, e.g., ${\mathrm{C}}_{60}{(\mathrm{O}\mathrm{H})}_{36}$. Thus, the molecular properties of fullerenols were systematically analyzed for structures with $n=1$, 2, 3, 4, 8, 10, 16, 18, 24, 32, and 36. From the electronic structure analysis of these molecules, we have evidenced an important effect related to the weak chemical reactivity of a possible ${\mathrm{C}}_{60}{(\mathrm{O}\mathrm{H})}_{24}$ isomer. To investigate Raman scattering and the vibrational spectra of the different fullerenols, frequency calculations are carried out within the harmonic approximation. In this case a systematic study is only performed for $n=1\char21{}4$, 8, 10, 16, 18, and 24. Our results give good agreements with the expected changes in the spectral absorptions due to the hydroxylation of fullerenes.

Wettability conversion of colloidal TiO2 nanocrystal thin films with UV-switchable hydrophilicity

Under pulsed laser UV irradiation, thin-film coatings made of close-packed TiO2 nanorods individually coated with surfactants can exhibit a temporary increase in their degree of surface hydroxylation without any apparent photocatalytic removal of the capping molecules. This mechanism provides a basis for achieving light-driven conversion from a highly hydrophobic to a highly hydrophilic, metastable state, followed by extremely slow recovery of the original conditions under dark ambient environment. A deeper insight into the wetting dynamics is gained by time-dependent water contact-angle and infrared spectroscopy monitoring of the film properties under different post-UV storage conditions. Our study reveals that, for reversible switchability between extreme wettability excursions and long-term repeatability of such changes to be achieved, specific modifications in the polar and nonpolar components of the TiO2 films need to be guaranteed along with preservation of the original geometric arrangement of the nanocrystal building blocks. The application of moderate vacuum is found to be an effective method for accelerating the post-UV hydrophilic-to-hydrophobic conversion, thereby enabling fast and cyclic hydrophilization/hydrophobicization alternation without any detrimental signs of significant fatigue.