In situ characterization of the illuminated silicon-electrolyte interface by Fourier-transform infrared spectroscopy.
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Journal Article↗
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Results for “Spectroscopy, Fourier Transform Infrared”
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Light induced intramolecular processes of bacteriorhodopsin monitored by time resolved FTIR (Fourier transform infrared) spectroscopy.
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Bacteriorhodopsins↗
Structural studies of phosvitin in solution and in the solid state.
Phosvitin, a highly phosphorylated glycoprotein, represents the major fraction of hen egg yolk phosphoproteins. Circular dichroism, Fourier transform infrared spectroscopy, and Fourier transform infrared photoacoustic and fluorescence spectroscopic methods were employed to determine the secondary structure of the protein in both the solid and solution phases. This was supplemented by a Chou-Fasman type of predictive algorithm for the first 25 residues at the N terminus of the dephosphorylated protein. A three-compartment model consisting of alpha-helical, beta-sheet, and beta-turn components with beta-turns occurring at the interface between alpha-helical and beta-sheet regions in the proximity of O-phosphoserine residues is suggested from the combined analyses. Beta-sheets appear to be the dominant secondary structural component in phosvitin in the solid and solution phases. The suggested model bears many similarities to other phosphoproteins reported in the literature. The secondary structure of phosvitin is observed to be sensitive to environmental factors as previously reported although the present studies differ in some respects from earlier results. Preliminary results suggest that Ca2+ ions trigger a decrease in beta-sheet structure at pH 2.
Amino Acid Sequence↗
Effect of the esters of gallic acid on model and human blood platelet membranes studied by Fourier transform infrared spectroscopy.
Gallic acid is one of the components of Chinese herbal drug Radix paeoniae used for promoting blood circulation to remove blood stasis. This paper studied the effects of gallic acid and its esters (e.g. ethyl, propyl, isobutyl and butyl gallate) on model and human blood platelet membranes by FTIR which was used for monitoring the physical state of the acyl chain, interfacial and head group region of the membrane lipid bilayer. From the experimental results it can be seen that the gallic acid and its esters have the modifying function on the pure and cholesterol-containing DPPC model membranes, and have the quantity-effective and structural-effective relationships. In addition, it is discovered that these esters have the modifying effect on the structure of human blood platelet membrane and can reverse the effect of ADP. That the effect of the esters of gallic acid counteracts the effect of cholesterol and ADP on human blood platelet perhaps provides a new explanation of the mechanism of Chinese herbal drugs used for promoting blood circulation to remove blood stasis.
1,2-Dipalmitoylphosphatidylcholine↗
Determination of diffusion coefficients of sodium p-aminosalicylate in sheep nasal mucosae and dialysis membranes by Fourier transform infrared horizontal attenuated total reflectance spectroscopy.
Fourier transform infrared horizontal attentuated total reflectance (FT-IR-H-ATR) spectroscopy was employed to determine the diffusion coefficients of sodium p-aminosalicylate (PAS) in sheep nasal mucosae and dialysis membranes. The system configuration, which comprises a closed system with an aqueous layer and a membrane layer, represents diffusion from a solution of limited volume. Data analysis involved fitting a truncated (seven term) Fourier series to the total mass transport into the membrane as a function of time. Comparison of diffusion coefficients of PAS in dialysis membranes obtained by this technique to those obtained by a standard steady-state permeation method showed excellent agreement. Apparent diffusion coefficients were approximately 4.33 (+/- 0.38) x 10(-7) and approximately 9.62 (+/- 5.30) x 10(-7) cm2/s for dialysis membranes and sheep nasal mucosae, respectively. These values are substantially smaller than the diffusion coefficient of PAS in aqueous solution, indicating that the rate-limiting step was diffusion in the membrane. The effect of purified gastric mucin solution (concentration up to approximately 6% w/v) on the apparent diffusion coefficient of PAS in the membranes was also investigated. The results showed no statistically significant change in the apparent diffusion coefficient in the presence of mucin for either sheep nasal mucosae or dialysis membranes. Although it was reported that mucin in solution retards the diffusion of PAS as compared to buffer alone, the mass transport within the membrane was the rate-limiting step for this hydrophilic compound.
Aminosalicylic Acid↗
Structure and thermal denaturation of crystalline and noncrystalline cytochrome oxidase as studied by infrared spectroscopy.
Fourier-transform infrared spectroscopy has been applied to the study of lipid vesicle-supported two-dimensional crystals and noncrystalline preparations of beef heart cytochrome oxidase. At room temperature, no conformational differences are seen between the noncrystalline and crystalline proteins, whose conformation is shown to consist of ca. 40% alpha-helix, 20% extended structures (including beta-sheet), 17% beta-turns, and 22% open loops plus nonstructured conformations. A novel infrared approach that combines quantitative spectral band decomposition with the study of the thermal behavior of each component has been applied. The procedure allows the independent examination of temperature-induced changes in individual structural elements (alpha-helix, beta-sheet, beta-turns, and unordered). All these reflect, upon heating the protein from 20 to 80 degrees C, a major irreversible thermal event centred at 55-60 degrees C, leading to a molecular state devoid of enzyme activity but with a defined secondary structure; in addition, when the band position, percent area (integrated intensity), and bandwidth of the various amide I components are separately plotted versus temperature, each component is seen to behave in a characteristic way. Thermal denaturation in D2O buffer shows a decrease in nonstructured conformations and an increase in beta-turns without major changes in the proportion of alpha-helix. Temperature-induced changes are not the same in amorphous and crystalline structures, the latter being in general more stable toward the thermal challenge. The above data extend and confirm previous structural studies on cytochrome oxidase using cryo-electron microscopy.
Animals↗
The secondary structure of the inhibited mitochondrial ADP/ATP transporter from yeast analyzed by FTIR spectroscopy.
Fourier transform infrared spectroscopy has been applied to the study of the carboxyatractyloside-inhibited mitochondrial ADP/ATP transporter from the yeast Saccharomyces cerevisiae, either solubilized in dodecyl maltoside or reconstituted in phosphatidylcholine liposomes. Its secondary structure has been estimated by means of Fourier self-deconvolution followed by curve fit. A Voigt function was used to fit the components of the deconvoluted spectrum, aiming to account for any distortions introduced by deconvolution. For any of the states analyzed, reconstituted or solubilized, in solution or in dry films, 60-70% of the amino acids are found to adopt alpha-helix plus unordered structures, coherent with the six transmembrane spanning helix model. Moreover, the problem of structure preservation on drying was addressed, and several observations pointed to a maintenance of the protein structure in dry films. Comparison of reconstituted and solubilized samples indicated the presence of both lipid-induced changes in the protein (decrease of the beta-sheets and increase of unordered structures) and protein-induced changes in the lipids (strong hydrogen bonding of lipid C=O groups). To obtain a better discrimination of alpha-helix and unordered structure contributions for the reconstituted form, H/D exchange experiments were performed. Between 35% and 45% of the amino acids were finally assigned to alpha-helix structures, compatible with the existence of five or six transmembrane spanning helices in the transporter. The level of H/D exchange was determined after 15 h of exposure to D(2)O vapor to be 85%, reflecting a high accessibility of the amide hydrogens even for the carboxyatractyloside-inhibited state.
Amides↗
Detection of hazelnut oil adulteration using FT-IR spectroscopy.
Fourier transform infrared spectroscopy (FT-IR) was used to detect the adulteration of hazelnut oil with different types of oils and to detect the adulteration of extra-virgin olive oil with hazelnut oil. Spectra of hazelnut oil, seven other types of oils, extra-virgin olive oil, and the adulterated oils were collected with a FT-IR equipped with a ZnSe-ATR accessory and a MCTA detector. Discriminant analysis and partial least-squares analysis were used to analyze the data. Classification of hazelnut oil, olive oil, and the other types of oils was achieved successfully with FT-IR. The detection level for sunflower oil adulteration of hazelnut oil was 2%, and the correlation coefficient for the PLS model was 0.99. Adulteration of virgin olive oil with hazelnut oil could be detected only at levels of 25% and higher.
Food Contamination↗
The conformational analysis of peptides using Fourier transform IR spectroscopy.
Fourier transform infrared spectroscopy (FTIR) can be used for conformational analysis of peptides in a wide range of environments. Measurements can be performed in aqueous solution, organic solvents, detergent micelles as well as in phospholipid membranes. Information on the secondary structure of peptides can be derived from the analysis of the strong amide I band. Orientation of secondary structural elements within a lipid bilayer matrix can be determined by means of polarized attenuated total reflectance-FTIR spectroscopy. Hydrogen-deuterium exchange can be monitored by the analysis of the amide II band. This review gives some example of peptide systems studied by FTIR spectroscopy. Studies on alamethicin and alpha-aminoisobutyric acid containing peptides have shown that FTIR spectroscopy is a sensitive tool for identifying 3(10)-helical structures. Changes in the structure of the magainins upon interaction with charged lipids were detected using FTIR spectroscopy. Tachyplesin is an example of a beta-sheet containing membrane active peptide. Polarized ir spectroscopy reveals that the antiparallel beta-sheet structures of tachyplesin are oriented parallel to the membrane surface. Synthesis of peptides corresponding to functionally/structurally important regions of large proteins is becoming increasingly popular. FTIR spectroscopy has been used to analyze the structure of synthetic peptides corresponding to the ion-selective pore of the voltage-gated potassium channel. In biomembrane systems these peptides adopt a highly helical structure. Under conditions, where these peptides are aggregated the presence of some intermolecular beta-sheet structure can also be detected.
Alamethicin↗
The qualitative and quantitative analysis of chlorpropamide polymorphic mixtures by near-infrared Fourier transform Raman spectroscopy.
We analyzed binary mixtures of polymorphs A and B of chlorpropamide ((1-[4-chlorobenzenesulphonyl]-3-propyl urea)) by near-infrared Fourier transform Raman spectroscopy (FTRS). The individual polymorphs were prepared and characterized by differential scanning calorimetry (DSC), Fourier transform infrared (FT-IR) microscopy, and physical appearance. The FTR spectra of the two polymorphs showed distinct differences which result from "crystal splitting" effects. A series of 13 different mixtures of polymorph A and B was prepared by geometric mixing and their FTR spectra statistically analysed by factor analysis programming. Predictions of the A/B polymorphic composition of mixtures were made and compared with the theoretical values. The results demonstrate that FTRS combined with factor analysis programming may be successfully applied to the in situ monitoring of the A/B polymorphic nature of a chlorpropamide sample.
Calorimetry, Differential Scanning↗
Authentication of the botanical origin of honey by near-infrared spectroscopy.
Fourier transform near-infrared spectroscopy (FT-NIR) was evaluated for the authentication of eight unifloral and polyfloral honey types (n = 364 samples) previously classified using traditional methods such as chemical, pollen, and sensory analysis. Chemometric evaluation of the spectra was carried out by applying principal component analysis and linear discriminant analysis. The corresponding error rates were calculated according to Bayes' theorem. NIR spectroscopy enabled a reliable discrimination of acacia, chestnut, and fir honeydew honey from the other unifloral and polyfloral honey types studied. The error rates ranged from <0.1 to 6.3% depending on the honey type. NIR proved also to be useful for the classification of blossom and honeydew honeys. The results demonstrate that near-infrared spectrometry is a valuable, rapid, and nondestructive tool for the authentication of the above-mentioned honeys, but not for all varieties studied.
Discriminant Analysis↗
Electrospinning of chitosan solutions in acetic acid with poly(ethylene oxide).
Electrospinning of chitosan solutions with poly(ethylene oxide) (PEO) in an aqueous solution of 2 wt% acetic acid was studied. The properties of the chitosan/PEO solutions, including conductivity, surface tension and viscosity, were measured. Morphology of the electrospun chitosan/PEO was observed by using scanning electron micrographs. Results showed that the ultrafine fibers could be generated after addition of PEO in 2:1 or 1:1 mass ratios of chitosan to PEO from 4-6 wt% chitosan/PEO solutions at 15 kV voltage, 20 cm capillary-collector distance and flow rate 0.1 ml/h. During electrospinning of the chitosan/PEO solutions, ultrafine fibers with diameters from 80 nm to 180 nm were obtained, while microfibers with visually thicker diameters could be formed as well. Results of X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy and differential scanning calorimeter exhibited the larger electrospun microfibers were almost entirely made from PEO, while the electrospun ultrafine fibers mainly contained chitosan.
Acetic Acid↗
Polyaniline/Au composite hollow spheres: synthesis, characterization, and application to the detection of dopamine.
Polyaniline (PANI)/Au composite hollow spheres were successfully synthesized using polystyrene/sulfonated polystyrene core/shell gel particle templates. The PANI shell thickness and the number of Au nanoparticles decorating the PANI could be controlled effectively by adjusting the experimental conditions. The morphology, composition, and optical properties of the resulting products were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, thermogravimetric analysis, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and ultraviolet-visible absorption spectra. It was found that the electrical conductivity of the PANI/Au composite hollow spheres was more than 3 times higher than that of the pure PANI hollow spheres. Furthermore, PANI/Au composites were immobilized on the surface of a glassy carbon electrode (GCE) and applied to construct a sensor. The obtained PANI/Au-modified GCEs showed one pair of redox peaks and high catalytic activity for the oxidation of dopamine. The possible formation mechanism of the PANI/Au composite hollow spheres was also discussed.
Aniline Compounds↗
Fluorescent chelates for monitoring metal binding with macromolecules.
Metals and radionuclides are usually coupled with proteins together with suitable ligands for therapeutic, tumor-imaging, pharmaceuticals, and biocompatibility applications. Several ligands that can strongly coordinate a given nuclide in a specific valency are already known. However, the demand for bifunctionality has limited the applications of these ligands. We hereby report the molecular design of a receptor system based on the linkage of protein to monoazo ligands. By use of basic coordination chemistry, 4-(3-quinolinoazo)hydroxybenzoic acid (QABA) and derivatives were successfully conjugated to ovalbumin, bovine serum albumin, and alkaline phosphatase at a site that was distinct from the metal binding site. The presence of carboxylic acid linkage in the QABA served as a convenient bridge for protein conjugation and may allow the generic application of these ligands for bioconjugate synthesis while ensuring a high in vivo stability. The ligand-protein conjugates were characterized using UV-vis spectroscopy, Fourier transform infrared spectroscopy, thin layer chromatography, NMR, and surface-enhanced laser desorption ionization time-of-flight mass spectrometry. The conjugate was tested for the ability to recognize nonradioactive Ga(3+) at a physiological pH, and a binding constant of 1 x 10(20) was recorded. Also, the in vitro testing results indicated that the fluorescent conjugates exhibited significant selectivity for gallium compared to Pb(2+), Hg(2+), Zn(2+), Cu(2+), Fe(3+), and Co(2+) while no responses were obtained for alkaline and alkaline earth metals. These attributes could allow these conjugates to be used as a model for imaging sensors and for metal detection.
Calibration↗
Biochemical and biophysical changes induced by fungicide sodium diethyl dithiocarbamate (SDD), in phytocystatin purified from Phaseolus mungo (Urd): a commonly used Indian legume.
Phytocystatins are the plant thiol protease inhibitors involved in several reaction mechanisms of the plant system like regulation of proteolytic activity and storage of proteins. Biochemical and biophysical changes induced by fungicide SDD in phytocystatin purified from Phaseolus mungo have been investigated in terms of mass spectroscopy, Fourier transform infrared spectroscopy, and fluorescence spectroscopy, at pH 7.0, with varying fungicide concentrations (1-9 mM) and a time of incubation ranging from 2 to 8 h at 37 degrees C, with a fixed cystatin concentration (1.5 mM). Reactive oxygen species responsible for inhibitor damage were also investigated, and thiourea was found to scavenge the free radicals generated by SDD. FTIR analysis indicates a significant conformational transition from alpha-helix to beta-sheet structure; quenching of fluorescence is evident by fluorescence spectroscopy. The activity assay showed a decrease in inhibitory activity, as well as a fragmentation of the inhibitor was observed in electrophoresis. Results obtained implicate that exposure of phytocystatins to SDD involves physicochemical changes in cystatins leading to damage and a decrease in the activity of the inhibitor.
Chemical Phenomena↗
Structural, kinetic and cytotoxicity aspects of 12-28 beta-amyloid protein fragment: a reappraisal.
A chemical, structural and biological study on the beta-amyloid peptide beta12-28 is reported which was carried out in order to assess the feasibility using this peptide fragment as a model of the natural beta-amyloid protein. The aggregation properties of beta12-28 have been investigated by pulse field-gradient NMR spectroscopy, Fourier transform infrared spectroscopy and transmission electron microscopy. The results obtained suggest that beta12-28 behaviour is comparable to that of the natural beta-amyloid protein although kinetically slower. Translational diffusion coefficients obtained by NMR on an aged beta12-28 solution suggest that the soluble peptide fraction is composed of oligomeric intermediates adopting an extended ellipsoidal assembly rather than a spherical one. The beta12-28 peptide proved to be cytotoxic in PC12 cell cultures as monitored by the MTT assay, although a lack of reproducibility was observed in the dose-response experiments.
Amino Acid Sequence↗
Plasma synthesis of carbon magnetic nanoparticles and immobilization of doxorubicin for targeted drug delivery.
Using dense medium plasma technology, carbon magnetic nanoparticles (CMNP) were synthesized at room temperature and atmospheric pressure. Based on results from X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy and scanning electron microscopy, we conclude that these nanoparticles are composed of spherical particles, 40-50 nm in diameter, with iron/iron oxide particles dispersed in a carbon-based host-structure. Thermal gravimetry/differential thermal gravimetry analysis shows these nanoparticles are stable to temperatures as high as 600 degrees C. The synthesized CMNP were treated by argon-plasma, aminated with ethylene diamine and subsequently activated by generating aldehyde groups on them. Free doxorubicin (DOX) molecules were then immobilized onto the surfaces of activated CMNP particles to form CMNP-DOX conjugates. The corresponding loading efficiency was determined. The in vitro antiproliferative activity of immobilized doxorubicin in the conjugates was demonstrated in tumor cell cytotoxicity assays. It is suggested that this CMNP-DOX system can be used for targeted drug-delivery systems.
Animals↗
Characterization and dissolution behavior of sputtered calcium phosphate coatings after different postdeposition heat treatment temperatures.
There is a lack of correlation between specific properties of hydroxyapatite coating surfaces, osseointegration processes, and implant success. The aim of this study was to evaluate the relationship between well-characterized structural and chemical properties of radio-frequency sputtered calcium phosphate (CaP) coatings and their dissolution behavior. Sputtered CaP coatings were evaluated as-sputtered (non-heat treated) or after 1 hour of postsputter heat treatments at 400 degrees C or 600 degrees C. All coatings were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and contact angle measurement. The dissolution behavior of CaP coatings in the presence and absence of proteins was also investigated. It was observed from this study that as-sputtered CaP coatings were amorphous. The 400 degrees C heat-treated CaP coatings exhibited low crystallinity (1.9% +/- 0.4%), whereas the 600 degrees C heat-treated CaP coatings were highly crystalline (67.0% +/- 2.4%). The increase of Ca/P ratio, PO4/HPO4 ratio, and the number of PO4 peaks were observed to be consistent with the increase in heating temperature and the degrees of coating crystallinity. Phosphorus ions released from CaP coatings decreased with the increase of crystallinity of CaP coatings. In addition, immersion of CaP coatings in media containing proteins resulted in an increase in P ions released as compared with coatings immersed in media without proteins. It was concluded that the degree of CaP coating crystallinity can be controlled by varying the postdeposition heat-treatment temperature. It was also concluded that, aside from coating crystallinity, dissolution and reprecipitation of the coatings can be controlled by knowing the presence of proteins in the media and PO4/HPO4 ratio within the coatings.
Calcium Phosphates↗