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Results for “Spectroscopy, Fourier Transform Infrared”

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PubMed1999

Secondary structure of sea anemone cytolysins in soluble and membrane bound form by infrared spectroscopy.

Attenuated total reflection (ATR) Fourier transform infrared spectroscopy (FTIR) was used to investigate the secondary structure of two pore-forming cytolysins from the sea anemone Stichodactyla helianthus and their interaction with lipid membranes. Frequency component analysis of the amide I' band indicated that these peptides are composed predominantly of beta structure, comprising 44-50% beta-sheet, 18-20% beta-turn, 12-15% alpha-helix, and 19-22% random coil. Upon interaction with lipid membranes a slight increase in the alpha-helical and beta-sheet structures was observed with a concomitant decrease of the unordered structure. Polarisation experiments indicated that both toxins had some disordering effect on the lipid layers. The dichroic ratio of the alpha-helical component of the membrane-bound toxin was 3.0-3.3, indicating that this element was oriented with an angle of 38 degrees-42 degrees with respect to the normal to the plane of the crystal surface, thus resulting almost parallel to the mean direction of the lipid chains.

Animals↗

PubMed2000

Transient non-native secondary structures during the refolding of alpha-lactalbumin detected by infrared spectroscopy.

Stopped-flow Fourier-transform infrared spectroscopy (SF-FTIR) was used to identify native as well as non-native secondary structures during the refolding of the calcium-binding protein alpha-lactalbumin. Infrared absorbance spectra were recorded in real time after a pH jump induced refolding of the protein. In the presence of calcium, the refolding is fast with concerted appearance of secondary structures; in its absence, folding is much slower and intricate, with transient formation and disappearance of non-native beta-sheet. The possibility of detecting native as well as non-native structures at the same time is especially valuable in providing insight into the complexity of the refolding process of a protein.

Animals↗

PubMed2002

Carbonate apatite coating on titanium induced rapidly by precalcification.

Chemical treatments have been thought to be promised methods for improving bioactivity of titanium. In this work, the effect of precalcification with boiling saturated Ca(OH)2 solution on bioactivation of titanium was investigated. After precalcification and soaking in supersaturated Ca-P solution (SCP), calcium phosphate rapidly precipitated onto the surfaces of titanium, and after only three days an uniform apatite layer was found up to thickness of a few micrometers. The observation using scanning electron microscopy (SEM) showed that the coating was composed of a number of small crystal grains. The investigation by X-ray energy dispersion spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) indicated that the coating was Ca-deficient carbonate apatite. Based on the analyses for the surfaces and SCP, a mechanism of precipitation of apatite was proposed in thermal dynamics and kinetics.

Apatites↗

PubMed1997

Phagocytosis of chemically modified carbon materials.

An oxidizing treatment of carbon fibres in boiling nitric acid leads to significant changes in the chemical state of their surface. As a result of the chemical treatment on a hydrophobic carbon surface, hydrophilic domains are formed and phenolic, carbonyl and carboxyl groups appear. In this work the intensity of phagocytosis of carbon fibres obtained by carbonization of polyacrylonitrile was studied both for HNO3 etched and non-etched fibres. Part of the powdered material studied was placed in plasma before it was contacted with cells. To study the material, which was first placed in plasma and then contacted with cells, X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy were used. It was found that the powders made from the etched fibres are phagocytized more intensively. It was also found that the absorption of plasma proteins enhances the phagocytosis only for the fibres oxidized in HNO3 and has no influence in the case of powders obtained from non-etched fibres.

Animals↗

PubMed2004

[Study on the rapid and nondestructive identification of TCM formula particles by FTIR].

Formula particles made by Traditional Chinese Medicines (TCM) were studied systematically via Fourier Transform Infrared Spectroscopy (FTIR) in this paper. The products quality of different pharmaceutical factories (Guangdong Yifang, Jiangyin Tianjiang, Sanjiu Yiyao, Hongkong Purapharm) could be revealed directly in the FTIR spectra. Also the spectra of different batch numbers (same factory), particles before and after processing, and particles with different processing methods were studied. It is proved that FTIR is an effective, fast and advanced method to evaluate the production qualities.

Drugs, Chinese Herbal↗

PubMed2005

Identification of a Cd2+- and Zn2+-binding site in cytochrome c using FTIR coupled to an ATR microdialysis setup and NMR spectroscopy.

Fourier transform infrared (FTIR) difference spectroscopy allows the study of molecular changes occurring at active sites in proteins with high sensitivity. Reactions are triggered by light, potential, or temperature steps and more recently by the diffusion of buffers containing effectors above membrane proteins deposited as films on ATR crystals. We have adapted a microdialysis system to an ATR, to study metal sites in soluble proteins. In this study, we identified a Cd(2+)- or Zn(2+)-binding site in cytochrome c with dissociation constants of 17 and 42 microM, respectively, which affects the oxidation rate of ferrocytochrome c by hydrogen peroxide. Using the microdialysis ATR-FTIR setup, we determined that a histidine and the carboxylate group of a glutamate are involved in Zn(2+) binding. The implication of His 33 and Glu 104 in the binding site was deduced from the comparison of FTIR data recorded with horse heart and the variant tuna cytochrome c lacking these two amino acids. A two-dimensional NMR analysis of the Zn(2+)-binding site in horse heart cytochrome c confirmed that His 33 and residues close to the C terminus are sensitive to Zn(2+) binding. This study demonstrates that the microdialysis ATR-FTIR setup is promising for the analysis of metal sites in proteins. From H(2)O/(2)H(2)O exchange experiments, we concluded that the impact of Zn(2+) and Cd(2+) binding on the oxidation kinetics of ferrocytochrome c by H(2)O(2) is associated to the perturbation of a hydrogen-bonding network involving His 33 that is sensitive to the redox state of cytochrome c.

Animals↗

PubMed2004

Hydration dependence of backbone and side chain polylysine dynamics: a 13C solid-state NMR and IR spectroscopy study.

The molecular dynamics of solid poly-L-lysine has been studied by the following natural abundance (13)C-NMR relaxation methods: measurements of the relaxation times T(1) at two resonance frequencies, off-resonance T(1rho) at two spin-lock frequencies, and proton-decoupled T(1rho). Experiments were performed at different temperatures and hydration levels (up to 17% H(2)O by weight). The natural abundance (13)C-CPMAS spectrum of polylysine provides spectral resolution of all types of backbone and side chain carbons and thus, dynamic parameters could be determined separately for each of them. At the same time, the conformational properties of polylysine were investigated by Fourier transform infrared spectroscopy. The data obtained from the different NMR experiments were simultaneously analyzed using the correlation function formalism and model-free approach. The results indicate that in dry polylysine both backbone and side chains take part in two low amplitude motions with correlation times of the order of 10(-4) s and 10(-9) s. Upon hydration, the dynamic parameters of the backbone remain almost constant except for the amplitude of the slower process that increases moderately. The side chain dynamics reveals a much stronger hydration response: the amplitudes of both slow and fast motions increase significantly and the correlation time of the slow motion shortens by about five orders of magnitude, and at hydration levels of more than 10% H(2)O fast and slow side chain motions are experimentally indistinguishable. These changes in the molecular dynamics cannot be ascribed to any hydration-dependent conformational transitions of polylysine because IR spectra reveal almost no hydration dependence in either backbone or side chain absorption domains. The physical nature of the fast and slow motions, their correlation time distributions, and hydration dependence of microdynamic parameters are discussed.

Magnetic Resonance Spectroscopy↗

PubMed1994

Structures and stereochemistry of the very long alpha, omega-bifunctional alkyl species in the membrane of Sarcina ventriculi indicate that they are formed by tail-to-tail coupling of normal fatty acids.

In a previous study, we demonstrated that Sarcina ventriculi is capable of adjusting to alterations in environmental conditions (such as increase in temperature, lowering of pH, or addition of exogenous organic solvents) by the synthesis of a family of alpha, omega-dicarboxylic acids ranging from 28 to 36 carbons long (Jung, S., et al. 1993. J. Biol. Chem. 268: 2828-2835). The chain lengths and relative abundance of the very long dicarboxylic acids found in S. ventriculi suggest that they may be formed after the perturbation by the (enzymatic) tail-to-tail combinations of existing regular monofunctional fatty acids and not completely de novo by direct 2-carbon addition of acetyl coenzyme A (CoA). If this were true, knowing the structures of the regular fatty acids, we can predict those of the very long chain bifunctional acids. In this work we present definitive chemical results that strongly support this mechanism. This was done by analyzing the structures and stereochemistry of the very long bifunctional species in the light of those of the regular monofunctional species. The exact structures of membrane fatty acid methyl ester derivatives components were determined by various spectroscopic and chemical methods including gas chromatographic (GC) analysis, gas chromatography-mass spectrometry (GC-MS), 1H and 13C nuclear magnetic resonance (NMR) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, polarimetry, and reductive ozonolysis. This yielded precise structural and stereochemical information on the position of substitution of the acyl chain by methyl groups, position and configuration of double bonds, and optical activity. These results, coupled with the absence of intermediate length acyl species, indicated that the very long alkyl species (without exception) can be formed by tail-to-tail joining of existing fatty acids. The ideas of a dynamically regulated catalytic system is proposed.

Cell Membrane↗

PubMed2002

Characterization of sorption sites on Pilayella littoralis and metal binding assessment using 113Cd and 27Al nuclear magnetic resonance.

Metal interactions with the cellular structures of the marine alga Pilayella littoralis have been investigated to better understand how biomaterials sorb dissolved metals. Algae metal binding capacity at pH 5.0 was 2000, 850, 430, and 560 micromol g(-1) of dried material for Al(III), Cu(II), Cd(II), and Co(II), respectively. Binding site characterization was assessed by 1H and 13C nuclear magnetic resonance spectroscopy. Also, Fourier Transform Infrared spectroscopy (FTIR) provided some information about the types of functional groups that appear to be present in the algal material. The results suggested the presence of carboxylate, ether, amino, and hydroxyl groups. Investigation of metal competition for the alga binding sites was performed using 27Al and 113Cd NMR spectroscopy, which proved to be a valuable technique for Al and Cd sorption assessment. Aluminum and Cu were efficiently sorbed by the alga sites, and the binding affinity order of these metals was Al(III) > Cu(II) > Cd(II) > Co(II).

Adsorption↗

PubMed2003

Conformational study of linear and cyclic peptides corresponding to the 276-284 epitope region of HSV gD-1.

The results of conformational analysis of linear and cyclic peptides from the 276SALLEDPVG(284) sequence of glycoprotein D of Herpes simplex virus are presented. The epitope peptides were synthesized by SPPS and on resin cyclization was applied for preparation of cyclic compounds. Circular dichroism spectroscopy, Fourier-transform infrared spectroscopy and nuclear magnetic resonance (NMR) were used to determine of the solution structure of both linear and cyclic peptides. The results indicated that the cyclopeptides containing the core of the epitope (DPVG) as a part of the cycle have more stable beta-turn structure than the linear peptides or the cyclic analogues, where the core motif is not a part of the cycle. NMR study of H-SALLc(EDPVGK)-NH(2) confirm presence of a type I beta-turn structure which includes the DPVG epitope core.

Circular Dichroism↗

PubMed2002

Effects of Si speciation on the in vitro bioactivity of glasses.

The surface reactivity of glasses belonging to the (mol%) 31SiO2-11P2O5-(58-x)CaO-xMgO series, with x ranging from 0 to 32, was studied in Kokubo's simulated body fluid (SBF). Scanning electron microscopy, inductively coupled plasma spectroscopy and Fourier transform infrared spectroscopy were used to characterise the glass surface and the SBF compositional changes. All glasses develop surface layers rich in silica and calcium phosphate. An increasing surface activity with increasing MgO/CaO ratio was observed. In a previous investigation using magic-angle spinning nuclear magnetic resonance it was found that there is an increasing abundance of Q0 species in the glass structure with increasing MgO content. The present work shows that, when immersed in SBF, Q0-rich glasses are easily leached to form a silica gel layer. It is concluded that MgO in the glass indirectly improves the early stages of mineralisation by favouring Q0 speciation. This mechanism plays an important role in glass bioactivity.

Glass↗

PubMed2004

Removal of trivalent and hexavalent chromium with aminated polyacrylonitrile fibers: performance and mechanisms.

Aminated polyacrylonitrile fibers (APANFs) were prepared and used as an adsorbent in a series of batch adsorption experiments for the removal of Cr(III) and Cr(VI) species from aqueous solutions of different pH values. The results show that significant amounts of Cr(III) or Cr(VI) species can be adsorbed by the APANFs, although the adsorption performances was greatly dependent upon the solution pH values. In general, the amounts of adsorption for Cr(III) species increased whereas that for Cr(VI) decreased with the increase of the solution pH values, which suggests that different adsorption mechanisms dominated the removal of Cr(III) or Cr(VI) species on the APANFs. X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy revealed that the adsorption of Cr(III) species on the APANFs was largely attributed to the formation of surface complexes between the nitrogen atoms on the APANFs and the Cr(III) species adsorbed, but the adsorption of Cr(VI) species on the APANFs was more likely effected through the formation of hydrogen bonds at high solution pH values or through both electrostatic attraction and surface complexation at low solution pH values. It was found that the Cr(VI)-adsorbed APANFs can be effectively regenerated in a basic solution and be reused almost without any loss of the adsorption capacity, while the Cr(III)-adsorbed APANFs needed to be regenerated in an acidic solution and the regeneration appeared to be less effective.

Acrylic Resins↗

PubMed2004

Binding of isofraxidin to bovine serum albumin.

The binding of isofraxidin to bovine serum albumin (BSA) was studied under physiological conditions with BSA concentration of 1.5 x 10(-6) mol x L(-1) and drug concentration in the range of 1.67 x 10(-6) mol x L(-1) to 2.0 x 10(-5) mol x L(-1). Fluorescence quenching spectra in combination with uv absorption spectroscopy, Fourier transform infrared (FTIR) spectroscopy, and CD spectroscopy was used to determine the drug-binding mode, binding constant, and the protein structure changes in the presence of isofraxidin in aqueous solution. The linearity of Scatchard plot indicates that isofraxidin binds to a single class of binding sites on BSA and the values given for the binding constants agree very closely with those obtained by the modified Stern-Volmer equation. The thermodynamic parameters, enthalpy change (DeltaH) and entropy change (DeltaS), were calculated to be -17.63 kJ x mol(-1) and 51.38 J x mol(-1) x K(-1) according to the van't Hoff equation, which indicated that hydrophobic interaction played a main role in the binding of isofraxidin to BSA.

Animals↗

PubMed2002

The Saccharomyces cerevisiae nucleoporin Nup2p is a natively unfolded protein.

Little is known about the structure of the individual nucleoporins that form eukaryotic nuclear pore complexes (NPCs). We report here in vitro physical and structural characterizations of a full-length nucleoporin, the Saccharomyces cerevisiae protein Nup2p. Analyses of the Nup2p structure by far-UV circular dichroism (CD) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, protease sensitivity, gel filtration, and sedimentation velocity experiments indicate that Nup2p is a "natively unfolded protein," belonging to a class of proteins that exhibit little secondary structure, high flexibility, and low compactness. Nup2p possesses a very large Stokes radius (79 A) in gel filtration columns, sediments slowly in sucrose gradients as a 2.9 S particle, and is highly sensitive to proteolytic digestion by proteinase K; these characteristics suggest a structure of low compactness and high flexibility. Spectral analyses (CD and FTIR spectroscopy) provide additional evidence that Nup2p contains extensive regions of structural disorder with comparatively small contributions of ordered secondary structure. We address the possible significance of natively unfolded nucleoporins in the mechanics of nucleocytoplasmic trafficking across NPCs.

Blotting, Western↗

PubMed2006

The interaction between N-n-undecyl-N'-(sodium p-aminobenzenesulfonate) thiourea and serum albumin studied using various spectroscopies and the molecular modeling method.

The preparation and characteristics of N-n-undecyl-N'-(sodium-p-aminobenzenesulfonate) thiourea (UPT), a new water-soluble reagent with a saturated fatty hydrocarbon group, were described. The interactions of UPT with bovine serum albumin (BSA) and human serum albumin (HSA) were studied using fluorescence spectroscopy in combination with ultraviolet (UV) absorption spectroscopy, circular dichroism (CD) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, and the molecular modeling method. UPT exhibited a strong ability to quench the intrinsic fluorescence of both BSA and HSA through a static quenching procedure. The binding constants of UPT and BSA or HSA were determined at different temperatures based on the relevant fluorescence data. The binding sites were obtained and the acting force was suggested to be mainly hydrophobic interaction, which was consistent with the result of the molecular modeling study, and there were also a number of hydrogen bonds between UPT and HSA. The results of determination of the proteins in bovine serum or human serum by this method were very close to those obtained by using Coomassie Brilliant Blue G-250 colorimetry. A practical method was proposed for the determination of UPT in bovine serum or human serum samples with satisfactory results.

Animals↗

PubMed1998

FT-Raman, FT-IR spectroscopy and PIXE analysis applied to gallstones specimens.

Fourier transform Raman (FT-Raman) spectroscopy and Fourier transform infrared spectroscopy (FT-IR) were used as the main analytical techniques for the determination of human gallstone structural composition. These techniques provide rapid, qualitative and quantitative information about stone structure. The gallstones were obtained from. 40 patients during both surgical operations and laparoscopy. The results of FT-Raman and FT-IR analysis allowed to distinguish of four main groups of gallstones according their cholesterol and bilirubinate salt content. Our studies were extended to trace element analysis by means of proton induced X-ray emission (PIXE). On 14 elements detected, six elements Ca, Mn, Fe, Cu, Zn and Br were chosen for quantitative analysis. The concentration levels of these elements varied depending the chemical structure of the gallstones. The relationship between Ca and Cu appears to be of particular significance. In this paper a correlation between stone structure and trace element concentrations is presented.

Adult↗

PubMed2000

Effect of protein on the dissolution of HA coatings.

The dissolution behavior of hydroxyapatite (HA) in the presence and absence of protein needs to be investigated in order to fully understand the initial cellular response to HA surfaces. In this study, HA coatings were characterized using X-ray diffraction, X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy (FTIR) prior to protein study. Fibronectin and albumin adsorption study were also performed. Calcium and phosphorus released in the presence and absence of albumin were measured. pH of the solution was measured daily. From the materials characterization, it was observed that the coatings exhibit a HA-type structure, with traces of sodium on the surface. FTIR indicated the possible presence of carbonates on the coatings. From the adsorption study, the amount of albumin adsorbed (0.052+/-0.005 microg/mm2) was statistically higher than the amount of fibronectin adsorbed on HA surfaces (0.035+/-0.002 microg/mm2). Flame atomic absorption indicated a significantly higher calcium ions released initially for HA coatings incubated with proteins as compared to coatings in the absence of proteins. However, after 7 days incubation, no significant difference in calcium ions release was observed between the HA coatings in the presence and absence of proteins. Phosphorus dissolution on HA coatings was not significantly affected by the presence of proteins. Thus, it was suggested from this study that the initial dissolution properties of calcium ions from HA coatings was dependent on the media.

Albumins↗

PubMed1994

A new family of very long chain alpha,omega-dicarboxylic acids is a major structural fatty acyl component of the membrane lipids of Thermoanaerobacter ethanolicus 39E.

A new family of alpha,omega-dicarboxylic, very long chain fatty acids was isolated and characterized from the lipids of thermophilic anaerobic eubacterium, Thermoanaerobacter ethanolicus 39E. After the isolation of the membrane, the fatty acyl components were converted to methyl esters by acid-catalyzed methanolysis. The esterified fatty acyl components were purified by a variety of chromatographic techniques and analyzed by gas chromatography (GC) and GC-mass spectrometry (MS). One of the isolated, esterified alpha,omega-dicarboxylic, very long chain fatty acids was characterized by mass spectrometry, 1H and 13C NMR spectroscopy and Fourier transform infrared spectroscopy. NMR experiments used included double quantum filtered correlated spectroscopy (DQF-COSY) to establish spin connectivities and polarization transfer (DEPT) to measure the multiplicity of carbon signals split by protons. Based on these results, the structures of the other components could be deduced from their mass spectra. The new family of very long chain fatty acid methyl esters are alpha,omega-13,16-dimethylheptacosanedioate dimethyl ester (C29), alpha,omega-13,16-dimethyloctacosanedioate dimethyl ester (C30), alpha,omega-13,16-dimethylnonacosanedioate dimethyl ester (C31), and alpha,omega-13,16-dimethyltriacotanedioate dimethyl ester (C32). This family of fatty acids make up about 40% of fatty acyl components of the membrane of Thermoanaerobacter ethanolicus 39E. Almost all (> 90%) of the very long chain, alpha,omega-dicarboxylic fatty acid was alpha,omega-13,16-dimethyloctacosanedioic acid. A careful analysis of the structures of the alpha,omega-dicarboxylic acid strongly implies that the synthetic mechanism for formation is by tail-to-tail (omega)coupling of regular iso-branched fatty acids across opposite sides of the membrane.

Bacteria, Anaerobic↗