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Results for “Spectroscopy, Fourier Transform Infrared”

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PubMedDate not supplied

Formulation and evaluation of Alendronate Sodium gel for the treatment of bone resorptive lesions in Periodontitis.

Alendronate sodium is formulated into gels and evaluated for the treatment of bone resorptive lesions in periodontitis. Carbopol 934P was used for the preparation of gels in three different concentrations. The prepared gel was evaluated for various properties such as preformulation, content uniformity, viscosity, compatibility, sterility, in vitro diffusion, and in vivo studies. The drug and the polymer were found to be compatible and confirmed by Fourier transform infrared spectroscopy. Viscosity of the gels increased with the increase in the polymer concentration. The formulations were found to be sterile. In vitro release study revealed that drug released from the gel follows non-Fickian diffusion followed by first-order release. In vivo studies were carried out for 6 months in patients. The results revealed a significant improvement in the clinical parameters such as gingival index, probing pocket depth, clinical attachment level, and potent inhibitory effect on bone resorption by inhibition of osteoclasts. In addition, there was increase in the new bone formation.

Administration, Buccal↗

PubMed2003

Determination of hydrocarbons using sapphire fibers coated with poly(dimethylsiloxane).

A poly(dimethylsiloxane) (PDMS) coated sapphire fiber has been investigated as a sensor for hydrocarbons (HCs) in the mid-infrared region around 3000 cm(-1). In order to optimize and predict sensor response, the diffusion behavior of the analytes into the PDMS preconcentration medium has been examined. A diffusion model based on Fickian diffusion was used to quantify diffusion. The model incorporated such factors as film thickness, refractive index of the polymer and the fiber core, and principal wavelength at which the analyte absorbs. A range of hydrocarbons, from hexane to pentadecane, was analyzed at 2930 cm(-1) using both fiber-coupled Fourier transform infrared spectroscopy and a modular prototype system. Diffusion coefficients were determined for these compounds and diffusion behavior examined and related to factors such as analyte polarity and molecular size. The diffusion coefficients were found to range from 6.41 x 10(-11) 5 x 10(-12) to 5.25 x 10(-11) +/- 9 x 10(-13) cm2 s(-1) for hexane and pentadecane into a 2.9 microm PDMS film, respectively. The diffusion model was also used to examine the effect of changing system parameters such as film thickness in order to characterize sensor response.

Aluminum Oxide↗

PubMed2001

Organo-clay formulation of acetochlor for reduced movement in soil.

This study aimed to design ecologically acceptable formulations of acetochlor by adsorbing it on montmorillonite exchanged by a small organic cation, phenyltrimethylammonium (PTMA). Adsorption of acetochlor on the clay mineral exchanged with different organic cations and its release from these complexes were determined by GC and modeled by Langmuir equation. Interactions between acetochlor molecules and the exchanged organic cation on the clay surface were studied by Fourier transform infrared spectroscopy. Leaching of acetochlor in soil was determined by a bioassay using a column technique and Setaria viridis as a test plant. The adsorbed amounts of acetochlor on montmorillonite exchanged by PTMA at a loading of 0.5 mmol/g of clay were higher than at a loading up to the cation-exchange capacity, i.e., 0.8 mmol/g, and were higher than obtained by using a clay mineral exchanged by other organic cations. Preloading montmorillonite by PTMA at 0.5 mmol/g yielded maximal shifts of the infrared peaks of the herbicide. The above formulation of acetochlor yielded slow release in water and showed improved weed control in field and greenhouse experiments in comparison with the commercial formulation. The PTMA-clay formulation of acetochlor maintained herbicidal activity in the topsoil and yielded the most significant reduction in herbicide leaching and persistence under field conditions. The application of this formulation can minimize the risk to groundwater and can reduce the applied rates.

Adsorption↗

PubMed2005

Cholesteryl hemisuccinate as a membrane stabilizer in dipalmitoylphosphatidylcholine liposomes containing saikosaponin-d.

In the present study, cholesteryl hemisuccinate (CHEMS) was evaluated for use as a membrane stabilizer in dipalmitoylphosphatidylcholine (DPPC) liposomes. Differential scanning calorimetry (DSC) and a calcein release study showed that CHEMS was more effective than cholesterol (CHOL) in increasing DPPC membrane stability. The findings of Fourier transform infrared spectroscopy (FT-IR) also suggested that CHEMS interacts with DPPC via both hydrogen bonding and electrostatic interaction. More importantly, CHEMS did not interact with saikosaponin-d (SSD), a triterpene saponin from Bupleurum species, unlike CHOL. SSD-containing liposomes with DPPC, CHEMS and DSPE-PEG could greatly decrease the hemolytic activity of SSD. This study demonstrated that CHEMS has more stabilization ability than CHOL since CHEMS may exhibit both hydrogen bond interaction and electrostatic interaction with DPPC membrane while CHOL only has hydrogen bond interaction, resulting in stable and low-hemolytic SSD-liposomes.

1,2-Dipalmitoylphosphatidylcholine↗

PubMed1995

Polymerization of composites using pulsed laser.

The quality of visible-light-cured composites depends on the capability of the light source to properly polymerize the material within a specified exposure time. In this study, the degree of conversion of different composite materials (hybrid and microfilled) of light and dark shades was compared after illumination by a standard curing unit and pulsed laser (lambda=468) respectively. The degree of conversion was measured by Fourier transform infrared spectroscopy. Results obtained by the analysis of the pulsed laser-induced polymerization were significantly higher for all the materials and shades observed. All values of the degree of conversion were lower for dark shades of all types of composites, regardless of the photopolymerization technique used. Besides the surface, better polymerization was recorded also at depths of 1.0, 2.0 and 3.0 mm, respectively. These values varied from 59.7%+/-2.14 to 84.5%+/-0.33 for pulsed laser (including all depths) caused by the saturation effect induced by high power laser pulses and from 42.7%+/-1.48 to 74.7%+/-0.99 for standard polymerization.

Acrylic Resins↗

PubMed1997

Crystal dissolution-controlled release systems. II. Metronidazole release from semicrystalline poly(vinyl alcohol) systems.

Novel semicrystalline, poly(vinyl alcohol) (PVA)-based phase erosion systems were developed. The rate of drug release from these systems is controlled by the rate of crystal dissolution. PVA devices loaded with metronidazole were exposed to temperatures ranging from 90 to 120 C for times of 10-90 min to obtain samples with different degrees of crystallinity. Degrees of crystallinity were measured by differential scanning calorimetry and attenuated total reflectance Fourier transform infrared spectroscopy. In vitro release of metronidazole from such systems into deionized water at 37 degrees C was monitored. The influence of parameters such as polymer molecular weight, annealing time and temperature, and surface pretreatment on the crystal dissolution, and hence the drug release rate, were investigated. Measurements of water-front movements were carried out to study the effect of parameters such as drug solubility on the release rate. The drug release rate was found to be dependent on the crystallization conditions of the samples. Surface pretreatment was found to reduce the burst effect observed during the release.

Antitrichomonal Agents↗

PubMed1997

ATR-FTIR spectroscopic investigation of E. coli transconjugants beta-lactams-resistance phenotype.

Hyphenation of attenuated total reflection Fourier transform infrared spectroscopy and cluster analysis has been used to characterise a susceptible Escherichia coli K12 strain and the transconjugants TEM-1, TEM-2, TEM-3, SHV-2, SHV-3, SHV-4. A good discrimination of the susceptible strain from the transconjugants was obtained. Although a limited success was achieved in the differentiation of SHV and TEM phenotypes in general, results obtained with TEM-2 and SHV-3 were convincing. Spectral differences observed are ascribed to the global effects of the conjugation process, particularly their repercussions in the nucleic acids and carbohydrate absorbing regions, rather than to beta-lactamase point-mutations.

Conjugation, Genetic↗

PubMed2001

A photoacoustic FTIRS study of the chemical modifications of human dentin surfaces: I. Demineralization.

Acids are used to modify the structure and composition of dentin surfaces to improve bonds formed with resins. The purpose of this work is to investigate such chemical modifications using the surface-sensitive technique photoacoustic Fourier transform infrared spectroscopy (PA-FTIRS). Spectra of acid-treated samples (citric, maleic, nitric, and phosphoric at pH = 1.0) were recorded at various time intervals. Analysis of these spectra indicates a gradual increase in sample surface area with treatment time. A decrease of the bands associated with calcium hydroxyapatite (HAP) and carbonate apatite inherent to the mineral phase of dentin are also observed. A comparison of spectra of samples treated for 2 min with each acid also reveals that maleic and phosphoric acids remove more HAP than citric acid. We conclude that citric acid may cause the formation of precipitates at the etching front which inhibit etching.

Acids↗

PubMed2000

Analysis of released products from oxidized ultra-high molecular weight polyethylene incubated with hydrogen peroxide and salt solutions.

The wear of ultra-high molecular weight polyethylene (UHMWPE) implants generates polymeric and metallic particulate, which can be phagocytosed by human macrophages. The generation of these UHMWPE particles has been attributed to wear mechanisms and oxidation of the material. Many cell/particle studies have focused specifically on investigating particles of virgin materials themselves (i.e. virgin UHMWPE), while in fact, there is a strong likelihood that the oxidation processes encountered by the materials will yield particles with very different surface chemistries. Therefore, it is conceivable that chemical changes in the material would lead to altered cellular responses, as measured in the various cell study models. This paper has focused on the characterization of UHMWPE particulates that have been exposed to various conditions simulating processing steps and some of the oxidative and hydrolytic agents related to inflammatory responses. These include gamma-irradiation, thermal treatment and chemical oxidation by H2O2 and saline solutions. Oxidation of the particles was measured using Fourier transform infrared spectroscopy (FTIR). Degradation products were isolated from the incubation solutions using high-performance liquid chromatography (HPLC). UHMWPE particulates underwent extensive oxidation after gamma-irradiation and thermal treatments. There were marked differences following treatments of film samples taken from bar stock and the virgin particle samples. Polymer-related products, containing alkenes, alkanes and hydroxyl groups, were found in the incubation solutions. The study concluded that future work must consider both the particulates' surface chemistry and the possibility of soluble degradation products when assessing UHMWPE/cellular interactions.

Biocompatible Materials↗

PubMed1997

Comparison of recalcitrance to ciprofloxacin and levofloxacin exhibited by Pseudomonas aeruginosa bofilms displaying rapid-transport characteristics.

Attenuated total reflection Fourier transform infrared spectroscopy was used to measure transport of the fluoroquinolones (FQs) ciprofloxacin and levofloxacin into Pseudomonas aeruginosa biofilms. Biofilms were exposed to each FQ at dose levels of 100, 250, and 500 microg/ml for 30 min. A mathematical transport model was used to extract the diffusion coefficient, binding site density, and adsorption and desorption rates for each experiment. Recalcitrance of the biofilms toward each FQ was evaluated by comparison of efficacies with planktonic bacteria. By this criterion, biofilms were found to exhibit more recalcitrance toward levofloxacin than ciprofloxacin under the experimental conditions. These results cannot be explained by the more hindered transport of levofloxacin, implicating the domination of physiological factors.

Anti-Infective Agents↗

PubMed2002

Biomimetic calcium phosphate coatings on Polyactive 1000/70/30.

Precalcification of Polyactive 1000/70/30 with a biomimetic calcium phosphate coating is expected to enhance the bioactivity of this biodegradable polymer for the application as bone filler or scaffold of bone tissue engineering. This study presents a 1-day one-step incubation method to obtain either amorphous or bone-like apatitic calcium phosphate coating on Polyactive 1000/70/30. Either dense plates or three-dimensional porous blocks of the polymer were incubated in a simplified but concentrated simulated body fluid-derived solution at 37 degrees C. By bubbling CO2 gas, a solution was prepared with calcium and phosphate ion concentrations five times of that of regular simulated body fluid. With controlled stirring, the CO2 was released out of the solution and exchanged by air. The pH of the solution increased to induce coating formation. Adjusting stirring rate and CO2/air exchange rate controlled the process kinetics. The reaction kinetics had little influence on the crystallographic structure of the final coating mineral for a given solution composition as shown by Fourier transform infrared spectroscopy and X-ray diffraction. However, the interface structure between the coating and substrate was kinetics-dependent. A fast precipitation condition resulted in a uniform but superficial calcification pattern at the surface of polymer. A slow process by selecting either a slow stirring or a slow CO2/air exchange, on the contrary, induced a localized but deep inside calcification pattern. A tensile test showed no statistically significant difference in the mechanical properties among uncoated and coated polymers. The cracking behavior of coatings from different kinetics, however, exhibited different manners, as can be attributed to different interface structures and interfacial strengths.

Bone Substitutes↗

PubMed2001

Fourier-transform infrared spectroscopic study of Ca2+-binding to osteocalcin.

Osteocalcin, the gamma-carboxyglutamic acid-containing protein, which is the most abundant noncollagenous protein of bone and dentin, is considered to play roles in bone formation and remodeling. It is unclear how the gamma-carboxyglutamic acid side-chains in osteocalcin coordinate to Ca2+, since the X-ray structure of osteocalcin is not available. Interactions between Ca2+ and the gamma-carboxyglutamic acid side-chains in osteocalcin were investigated by Fourier-transform infrared spectroscopy. In the region of the antisymmetric stretches, the loss of intensity at 1574 cm(-1) and gain of intensity at 1600 cm(-1) were observed due to Ca2+-binding to osteocalcin. The spectral changes indicate that the gamma-carboxyglutamic acid side-chains in osteocalcin coordinate to Ca- in the malonate chelation mode, where a Ca2+ interacts with two oxygen atoms, one from each of the two COO- groups of a single gamma-carboxyglutamic acid residue. Addition of Ca2+ does not cause any spectral change in the spectra of decarboxylated osteocalcin since the gamma-carboxyglutamic acid residues are converted to the glutamic acid residues by chemical modification.

Animals↗

PubMed1991

Water diffusion in a basaltic melt.

Water is the most abundant volatile component in terrestrial basalts and is a significant constituent of the gases that escape from basaltic magmas. Knowledge of the diffusivity of water (and other volatiles) in basaltic melts is important for understanding the degassing of basaltic magma and for assessing the fractionation of volatiles during degassing. We report here measurements of water diffusivity in a basaltic liquid. The water concentration profiles through the samples, determined by Fourier-transform infrared spectroscopy, cannot be modelled adequately on the basis of a constant water diffusivity, but instead can be fitted by assuming that only molecular H2O is diffusing and that there is a local equilibrium between H2O molecules and OH groups. The concentration-dependent total water diffusivities in the basaltic melt at 1,300-1,500 degrees C are 30-50 times as large as those in rhyolitic melts, and are greater than the total CO2 diffusivity in basaltic melts, contrary to previous expectations. These results suggest that diffusive fractionation would increase the ratio of water to carbon dioxide in growing bubbles relative to equilibrium partitioning, and decrease the ratio in interface melts near an advancing anhydrous phenocryst.

Carbon Dioxide↗

PubMed1996

A mixed helix-beta-sheet model of the transmembrane region of the nicotinic acetylcholine receptor.

We have modelled the transmembrane region of the alpha 7 nicotinic acetylcholine receptor as a mixed alpha-helical/beta-sheet structure. The model was mainly based on the crystal structure of a pore-forming toxin, heat-labile enterotoxin. This is a pentameric protein having a central pore or channel composed of five alpha-helices, one from each of the 5 B subunits that form this pentamer. The remainder of this structure is beta-sheet, loops and a short alpha-helix, not included in the model. The model uses this channel as a template to build the transmembrane region, from M1 to the middle of M3. The remainder of M3 and M4 were built de novo as alpha-helices. Great consideration was given to labelling data available for the transmembrane region. In general terms, the shape of the model agrees very well with that obtained independently by electron microscopic analysis and the secondary structure predicted by the model is in accord with that estimated independently by Fourier transform infrared spectroscopy. The M2 helical region of the model is only slightly kinked, contrary to what is inferred from electron microscopic analysis, but has the same overall shape and form. On the membrane face of the model, the presence of deep pockets may provide the structural basis for the distinction between annular and non-annular lipid binding sites. Also, the transmembrane region is clearly asymmetric in the direction perpendicular to the membrane, and this may have strong influence on the surrounding lipid composition of each leaflet of the cytoplasmic membrane.

Amino Acid Sequence↗

PubMed1998

Heat-induced conformational changes of patatin, the major potato tuber protein.

This paper presents a first structural characterization of isolated patatin, the major potato tuber protein, at ambient and elevated temperatures. Isolated patatin at room temperature is a highly structured molecule at both secondary and tertiary levels. It is estimated from far-ultraviolet circular dichroism data that about 33% of the residues adopts an alpha-helical and 46% a beta-stranded structure. Patatin is thermally destabilized at temperatures exceeding 28 degrees C, as was indicated by near-ultraviolet circular dichroism. It was shown that parts of the alpha-helical contributions unfold in the 45-55 degrees C region, whereas the beta-stranded parts unfold more gradually at temperatures of 50-90 degrees C. This was confirmed with Fourier-transform infrared spectroscopy. Differential scanning calorimetry indicated a cooperative transition between 50-60 degrees C, most likely reflecting the unfolding of alpha-helical parts of the molecule. Furthermore, fluorescence spectroscopy confirmed a global unfolding of the protein between 45-55 degrees C. The observed unfolding of the protein coincides with the inactivation of the patatin enzyme activity and with the precipitation as occurs in the potato fruit juice upon heating. At high temperatures, patatin still contains some helical and stranded structures. Upon cooling the protein partly refolds, it was observed that mainly alpha-helical structures were formed.

Butyrates↗

PubMed2002

Biotransformation of explosive-grade nitrocellulose under denitrifying and sulfidogenic conditions.

Waste nitrocellulose (NC) is regulated as a hazardous material. The objective of this study was to determine if NC exposed to denitrifying and sulfidogenic conditions would undergo sufficient removal of the nitro groups to yield a material that is no longer explosive. Enrichment cultures were established with methanol as the electron donor for nitrate-reducing conditions and lactate for sulfate-reducing conditions. NC was added to the cultures at 10 g/l. A statistically significant decrease in the nitrogen (N) content of NC occurred in both enrichment cultures, from approximately 13.1-13.2% in virgin NC to 12.2-12.4%. This was accompanied by an increase in nitrogen gas formation. The presence of a primary substrate (methanol and lactate) was necessary to affect this change; NC itself did not serve as an electron donor. In cultures that were carrying out denitrification but were then depleted of nitrate, with methanol still present, a slightly greater removal of nitro groups from NC occurred along with additional formation of nitrogen gas. NC did not have an inhibitory affect on the denitrification process but it did significantly slow the rate of lactate consumption and sulfate reduction. Fourier Transform Infrared Spectroscopy (FTIR) results indicated that NC exposed to denitrifying conditions was enriched in hydroxyl groups, consistent with removal of some of the nitro groups by hydrolysis of the nitrate esters. NC exposed to nitrate- and sulfate-reducing conditions and virgin NC were also compared based on their explosive properties using a small-scale burning test. The biologically treated NC exhibited somewhat less reactivity, but was still rated as explosive. The decrease in%N, increase in N2, and FTIR results demonstrated that NC does undergo biotransformation in the presence of nitrate- and sulfate-reducing enrichment cultures, but the extent of denitration does not appear to be adequate to yield a nonhazardous product.

Biotransformation↗

PubMed1993

Spectroscopic characterization of mutants supports the assignment of histidine-419 as the axial ligand of heme o in the binuclear center of the cytochrome bo ubiquinol oxidase from Escherichia coli.

The bo-type ubiquinol oxidase of Escherichia coli is a member of the superfamily of heme-copper oxidases which also includes the aa3-type cytochrome c oxidases. The oxygen-binding binuclear center of cytochrome bo is located in subunit I and consists of a heme (heme o; heme a3 in the aa3-type oxidases) and a copper (Cu(B)). Previous spectroscopic studies have shown that heme o is bound to the protein via a single histidine residue. Site-directed mutagenesis of conserved histidine residues in subunit I has identified two residues (H284 and H419) which are candidates for the ligand of heme o, while spectroscopic studies of mutants at H284 definitively demonstrated that this residue cannot be the axial ligand. Consequently, the single remaining conserved histidine in subunit I (H419) was assigned as the ligand for the heme of the binuclear center. In this paper, this assignment is tested by characterization of additional mutants in which the putative heme o axial ligand, H419, is replaced by other amino acids. All mutations at H419 result in the loss of enzyme activity. Analyses via UV-visible and Fourier transform infrared spectroscopies reveal that substantial perturbation has occurred at the binuclear center as a result of the amino acid substitutions. In contrast with the wild-type enzyme, the mutant enzymes bind very little carbon monoxide. Three other amino acid residues which are potential ligands for heme o are shown tob e nonessential for enzyme activity. Mutations in these residues do not perturb the UV-visible or FTIR spectroscopic characteristics of the enzyme.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗

PubMed2005

Characterization of inclusion complexation between fenoxaprop-p-ethyl and cyclodextrin.

Cyclodextrins (CDs) derived from natural starches are capable of forming inclusion complexes with a variety of organic compounds. This work evaluated the complexation role of CDs toward fenoxaprop-p-ethyl (FE) in an attempt to assess their potential as new formulation additives for more efficient FE delivery and better environmental approaches. beta-CD and its two derivatives, randomly methylated beta-CD (RAMEB) and 2-hydroxypropyl beta-CD (HP-beta-CD), were tested. The solubility of FE was enhanced in the presence of the CDs due to the formation of inclusion complexes, with RAMEB being >6 times more effective than the other two. The complexation was confirmed by differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD), where the FE melting peaks in DSC, the FTIR bands, and the XRD peaks were generally weakened. Within the tested time up to 60 min, the dissolution of the FE-CD complexes resulted in higher FE concentrations than did that of FE by itself. The dissolution of the FE-RAMEB complex was much faster than other complexes and FE alone. These results indicate that RAMEB was a better inclusion complexation agent for FE in terms of both solubility enhancement and dissolution rate. RAMEB may thus be used to improve FE delivery and to mobilize FE in soil for bioremediation.

Calorimetry, Differential Scanning↗