SEARCH · PubMed Health

Results for “Spectroscopy, Fourier Transform Infrared”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,117 records · Page 62Linked to original sources

PubMed2003

Influence of an optically thick water layer on the bond-strength of composite resin to dental enamel after IR laser ablation.

BACKGROUND AND OBJECTIVES: Several studies of hard tissue ablation with Er:YAG lasers have shown that the addition of an optically thick water layer ( approximately 1 mm) added to the surface of dental enamel before each incident laser pulse, profoundly influences the rate and efficiency of ablation and the resulting surface morphology. The objective of this study was the determination of laser parameters which result in clinically useful bond strengths without the need for phosphoric acid etching. The hypothesis to be tested was that laser irradiation through a relatively thick layer of water would result in a surface to which composite could be bonded with bond strength similar to surfaces etched with phosphoric acid. This hypothesis is predicated on the assumption that the water prevents the formation of non-apatite calcium phosphate phases on the enamel surface. MATERIALS AND METHODS: In this study, a calibrated syringe pump and a motion control system were used to uniformly treat flat enamel surfaces using free-running Er:YAG laser pulses with and without water, and 9.6 mum CO(2) laser pulses on a dry surface for comparison. The rate of water delivery that resulted in the most efficient ablation was determined by profiling the resulting laser incisions using optical coherence tomography. In addition, enamel surfaces of 5 x 5 mm(2) were uniformly treated and the resulting surface morphology was examined using synchrotron radiation-fourier transform infrared spectroscopy (SR-FTIR), and optical and electron microscopy. The influence of the modified surface morphology on the adhesion of composite resin was investigated. RESULTS: The shear-bond strength of composite bonded to enamel surfaces irradiated at intensities clinically relevant for caries removal approached values measured for conventional acid etching when the water delivery rate was optimized. CONCLUSIONS: This study demonstrates that composite restorative materials can be directly bonded to laser prepared surfaces without the necessity of further surface preparation and acid etching and that the addition of a thick water layer ( approximately 1 mm) prevents the formation of undesirable CaP phases that compromise adhesion to restorative materials. 2003.

Animals↗

PubMed2006

Selected morphological and functional properties of extruded acetylated starch-cellulose foams.

Starch acetates with degrees of substitution (DS) of 1.68 and 2.3 were extruded with 10%, 20% and 30% (w/w) cellulose and 20% (w/w) ethanol in a twin screw extruder at 150, 160 and 170 degrees C barrel temperatures and 170, 200 and 230 rpm screw speeds. X-ray diffractogram (XRD), differential scanning calormetry (DSC) and Fourier transform infrared spectroscopy (FTIR) were used to analyze the morphological properties of extruded foams. A central composite response surface design was applied to analyze the effects of starch type, cellulose content, barrel temperature and screw speed on specific mechanical energy requirement of extruding foams and the radial expansion ratio and compressibility of the extruded foams. XRD showed losses of DS starch and cellulose crystallinity and the formation of new complexes. FTIR spectra revealed that functional groups and chemical bonds were maintained after extrusion. Melting temperatures changed significantly when higher DS starch acetate was used. Cellulose content, barrel temperature and screw speed showed significant effects on thermal, physical and mechanical properties of extruded foams and the specific mechanical energy requirement.

Acetylation↗

PubMed2000

Folding of green fluorescent protein and the cycle3 mutant.

Although the correct folding of green fluorescent protein (GFP) is required for formation of the chromophore, it is known that wild-type GFP cannot mature efficiently in vivo in Escherichia coli at 37 degrees C or higher temperatures that the jellyfish in the Pacific Northwest have never experienced. Recently, by random mutagenesis by the polymerase chain reaction (PCR) method, a mutant called Cycle3 was constructed. This mutant had three mutations, F99S, M153T, and V163A, on or near the surface of the GFP molecule and was able to mature correctly even at 37 degrees C [Crameri et al. (1996) Nat. Biotechnol. 143, 315-319]. In the present study, we investigated the differences in their folding behavior in vitro. We observed the folding and unfolding reactions of both wild-type GFP and the Cycle3 mutant by using green fluorescence as an indicator of the formation of the native structure and examining hydrogen-exchange reactions by Fourier transform infrared spectroscopy. Both proteins showed unusually slow refolding and unfolding rates, and their refolding rates were almost identical under the native state at 25 and at 35 degrees C. On the other hand, aggregation studies in vitro showed that wild-type GFP had a strong tendency to aggregate, while the Cycle3 mutant did not. These results indicated that the ability to mature efficiently in vivo at 37 degrees C was not due to the improved folding and that reduced hydrophobicity on the surface of the Cycle3 mutant was a more critical factor for efficient maturation in vivo.

Animals↗

PubMed2005

The physicochemical characteristics of freeze-dried scutellarin-cyclodextrin tetracomponent complexes.

In an effort to improve the solubility of the insoluble drug scutellarin, a novel complexation of scutellarin with beta-cyclodextrin (beta-CD) was studied. Tetracomponent freeze-dried complex was prepared with scutellarin, beta-CD, Hydroxypropyl Methylcellulose (HPMC), and triethanolamine. To confirm complex formation, complex was characterized by Fourier transform infrared spectroscopy (FT-IR), powder X-ray diffraction, and differential scanning calorimetry (DSC). Phase-solubility analysis suggested the soluble complexes having 1:1 stoichiometry. The beta-CD solubilization of scutellarin could be improved significantly by combining water-soluble polymer and pH adjuster. Comparing the binary, ternary solid systems with tetrary systems, tetracomponent freeze-dried complex showed the best effect of solubilization. A maximal solubility of scutellarin (23.65 mg/ml) was achieved with tetracomponent freeze-dried complex, up to 148-fold increase over scutellarin solubility in water, and the solubility of scutellarin is 15.35 microg/ml (up to 6-fold) in simulated gastric fluid.

Apigenin↗

PubMed1995

[Analysis of deposits in calcific periarthritis].

Analysis was conducted on calcific deposits from 5 patients with calcific periarthritis. These calcific deposits were dried, immersed in hydrazine, or heated to 1000 degrees C for 1 hour, to prepare 3 kinds of samples. The samples were classified as dried samples, hydrazine-deproteinated samples, or as heated samples. All samples were analyzed by X-ray diffraction (XRD). Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy (Raman), and by electron probe microanalysis (EPMA). Although the XRD patterns of the dried samples and of the deproteinated samples were similar to that of hydroxyapatite (HAp), it was still unclear whether or not the calcific deposits were HAp. FTIR then revealed that the dried samples contained carbonate. Raman showed that the dried samples and the deproteinated samples do not have an OH-group. The dried samples were then heated to 1000 degrees C for one hour and analyzed by all 4 methods. The heated samples were found to be HAp. From these results, the calcific deposits from the 5 patients with calcific periarthritis were found to be carbonate apatite: Ca10-x-y/2 (PO4)6-x (CO3) x (OH) 2-y (CO3)y/2.nH2O.

Apatites↗

PubMed1994

FT-IR measurement of mercaptoundecahydrododecaborate in human plasma.

A simple and rapid method for the quantitative measurement of mercaptoundecahydrododecarborate (BSH), (which presently is one of the most useful agents for Boron Neutron Capture Therapy) in human plasma was developed by using Fourier transform infrared spectroscopy. Different spacer thicknesses of the liquid sampling cell were examined and the optimal results were obtained by the 0.05 mm spacer. The subtraction of water absorbance from sample spectra resolved a B-H band at 2493 cm-1. The quantitative measurement of BSH was carried out by integration of the B-H band in the wavenumber range of 2534-2440 cm-1. However, at the lower BSH concentration range, a visual inspection of the spectrum to determine the wavenumber range was necessary so as to avoid any negative areas to be integrated. The lower limit of detection of BSH in aqueous solution and human plasma was 5 micrograms ml-1 (about 2.5 ppm of boron).

Borohydrides↗

PubMed2003

[The effect of crystallization of calcium carbonate on the secondary structure of pepsin].

The effect of crystallization of calcium carbonate on the secondary structure of pepsin was studied by Fourier transform infrared spectroscopy, derivative, deconvolution and curve-fitting techniques in this paper. The result shows that the pure protein is composed of 24.38% alpha-helices, 29.91% beta-sheets, 39.22% beta-turns and 6.49% random structures, and the pepsin in the CaCO3/pepsin solution is composed of 2.09% alpha-helices, 93.304% beta-sheets, 4.60% beta-turns and 0.006% random structures. From these data we can see that the alpha-helices decrease and the beta-turns increase with the formation of the crystal of calcium carbonate. The essence of these changes is discussed in the paper.

Calcium Carbonate↗

PubMed1998

Analysis of in vitro reaction layers formed on Bioglass using thin-film X-ray diffraction and ATR-FTIR microspectroscopy.

Fourier transform infrared spectroscopy and thin-film X-ray diffraction (TF-XRD) techniques were used to analyze the inorganic carbonate apatite (CA) layer developed on a bioactive glass (45S5 type Bioglass) in an in vitro environment. The C-O and P-O vibrational modes appeared on the bioactive glass surface following immersion in the simulated body fluid solution. Initially, the C-O and P-O peaks increased with immersion time as crystallization of CA phase progressed. The TF-XRD confirmed that the deposited layer was apatite, crystallographically. Furthermore, evidence of preferred orientation in the 001 direction was seen, indicated by very strong 002 reflection. With time, the crystal growth became more random and the intensity of the 002 reflection decreased.

Biocompatible Materials↗

PubMed2005

High hydrostatic pressure dissociates early aggregates of TTR105-115, but not the mature amyloid fibrils.

A range of disorders such as Alzheimer's disease and type II diabetes have been linked to protein misfolding and aggregation. Transthyretin is an amyloidogenic protein which is involved in familial amyloid polyneuropathy, the most common form of systemic amyloid disease. A peptide fragment of this protein, TTR105-115, has been shown to form well-defined amyloid fibrils in vitro. In this study, the stability of amyloid fibrils towards high hydrostatic pressure has been investigated by Fourier transform infrared spectroscopy. Information on the morphology of the species exposed to high hydrostatic pressure was obtained by atomic force microscopy. The species formed early in the aggregation process were found to be dissociated by relatively low hydrostatic pressure (220 MPa), whereas mature fibrils are pressure insensitive up to 1.3 GPa. The pressure stability of the mature fibrils is consistent with a fibril structure in which there is an extensive hydrogen bond network in a tightly packed environment from which water is excluded. The fact that early aggregates can be dissociated by low pressure suggests, however, that hydrophobic and electrostatic interactions are the dominant factors stabilizing the species formed in the early stages of fibril formation.

Amyloid↗

PubMed2006

Fourier transform infrared spectra of transition metal ion-containing polyanilines synthesized in different reaction conditions.

Fourier transform infrared spectroscopy has been employed to investigate the detailed chain structure changes during the chemical oxidative polymerisation of aniline in different reaction conditions including different polarity reaction medium, reaction temperature, reactants molar ratio and in the presence of different transition metal ions such as Fe2+, Co2+, Ni2+ and Cu2+. The results show that stronger polarity reaction medium and lower reaction temperature were beneficial to obtain 1,4-para-disubstituted linear chain structure polyaniline with higher electrical conductivity. The higher oxidation degree polyaniline contained more linear chain structure than that in lower oxidation degree. Polyanilines containing Fe2+ and Cu2+ had more linear chain structure than that containing Co2+ and Ni2+. These observations were in accordance with experimental measurements of electrical conductivity.

Aniline Compounds↗

PubMed2000

Treatment of tooth fracture by medium energy CO2 laser and DP-bioactive glass paste: compositional, structural, and phase changes of DP-bioglass paste after irradiation by CO2 laser.

Nowadays, fractured teeth are difficult to treat effectively. Currently, root fractures are usually treated by root amputation, hemisection or tooth extraction. If the fusion of tooth fracture by laser were possible, it would offer a different therapy to repair fracture teeth. We tried to use a developed DP-bioactive glass paste to fuse or bridge the tooth crack line by a medium energy continuous-wave CO2 laser. The study is divided into three parts: (1) The compositional and structure changes in tooth enamel and dentin after laser treatment; (2) The phase transformation and recrystallization of DP-bioactive paste during exposure to the CO2 laser; (3) The thermal interactions and bridge mechanism between DP-bioactive glass paste and enamel/dentin when they are subjected to CO2 laser. The present report will focus on the second part that will examine the changes of laser-exposed DP-bioactive glass paste by means of X-ray diffractometer (XRD), Fourier transforming infrared spectroscopy (FTIR), differential thermal analysis/thermogravimetric analysis (DTA/TGA), and scanning electron microscopy (SEM). From the study, we could find that the temperature increase due to laser irradiation is greater than 900 degrees C and that the DP-bioactive glass paste could be melted in a short period of time after irradiation. In the study, we successfully developed a DP-bioactive glass paste which could form a melting glass within seconds after exposure to a medium energy density continuous-wave CO2 laser. The paste will be used in the near future to bridge the enamel or dentin surface crack by the continuous-wave CO2 laser.

Carbon Dioxide↗

PubMed1999

Usefulness of the frequency data of the fourier transform infrared spectra to evaluate the degree of oxidation of edible oils.

The oxidation process of 13 edible oil samples with different proportions of oleic, linoleic, and linolenic acyl groups has been studied using Fourier transform infrared spectroscopy. The oxidation experiments were carried out by heating the samples in a convection oven at 70 degrees C. Duplicate spectra were recorded from a film of pure oil between two disks of KBr for each sample every day during the course of the oxidation, and frequency data of each band of the spectrum were collected automatically. Changes in the values of the frequency of most of the bands of the spectra were observed. The shiftings of the frequency value of specific bands allowed one to distinguish between the different stages of the oxidation process and to establish the oxidation degree of each oil sample. This methodology could be useful to evaluate the oxidative stability of edible oils in a simple, fast, and accurate way.

Oxidation-Reduction↗

PubMed2001

Effects of Fe(III) binding to the nucleotide-independent site of F1-ATPase: enzyme thermostability and response to activating anions.

Mitochondrial F1-ATPase was induced in different conformations by binding of specific ligands, such as nucleotides. Then, Fourier transform infrared spectroscopy (FT-IR) and kinetic analyses were run to evaluate the structural and functional effects of Fe(III) binding to the nucleotide-independent site. Binding of one equivalent of Fe(III) induced a localised stabilising effect on the F1-ATPase structure destabilised by a high concentration of NaCl, through rearrangements of the ionic network essential for the maintenance of enzyme tertiary and/or quaternary structure. Concomitantly, a lower response of ATPase activity to activating anions was observed. Both FT-IR and kinetic data were in accordance with the hypothesis of the Fe(III) site location near one of the catalytic sites, i.e. at the alpha/beta subunit interface.

Anions↗

PubMed2003

Mechanism of strength increase for a hydrothermal porcelain.

OBJECTIVES: The objectives of this study were to verify the formation of a hydrolyzed surface layer on Duceram LFC, to determine the effects of such a layer on mechanical material properties, and to identify a specific mechanism responsible for any strength increase observed. METHODS: Specimens were fabricated from dentin porcelain by a vibration blotting technique and were prepared to have either blunt or sharp surface flaws. Half of the specimens underwent accelerated aging. Specimens were fractured in three-point flexure to measure their strength, and fractographic analysis was used to determine fracture toughness and residual surface stress. Surface hardness and elastic modulus were measured using a microindentation method. Porcelain surface topography was examined using atomic force microscopy, and Fourier transform infrared spectroscopy was used to determine the composition of the surface layer. RESULTS: The aging treatment modified the porcelain surface topography but did not create a layer with increased hydroxyl ion content. Porcelain strength increased upon aging, and the increase was proportional to initial flaw severity. The apparent fracture toughness of sharp flaw specimens increased to match that for specimens containing blunt flaws upon aging. Surface hardness and elastic modulus decreased upon aging. SIGNIFICANCE: Previous studies on the strength increase of hydrothermal porcelain were contradictory because a variety of specimen preparation procedures were used. This study resolves the apparent contradiction by determining the effect of specimen preparation on material strength.

Analysis of Variance↗

PubMed2004

Inhibition of HIV-1 envelope glycoprotein-mediated cell fusion by a DL-amino acid-containing fusion peptide: possible recognition of the fusion complex.

The N-terminal fusion peptide (FP) of human immunodeficiency virus-1 (HIV-1) is a potent inhibitor of cell-cell fusion, possibly because of its ability to recognize the corresponding segments inside the fusion complex within the membrane. Here we show that a fusion peptide in which the highly conserved Ile(4), Phe(8), Phe(11), and Ala(14) were replaced by their d-enantiomers (IFFA) is a potent inhibitor of cell-cell fusion. Fourier transform infrared spectroscopy confirmed that despite these drastic modifications, the peptide preserved most of its structure within the membrane. Fluorescence energy transfer studies demonstrated that the diastereomeric peptide interacted with the wild type FP, suggesting this segment as the target site for inhibition of membrane fusion. This is further supported by the similar localization of the wild type and IFFA FPs to microdomains in T cells and the preferred partitioning into ordered regions within sphingomyelin/phosphatidyl-choline/cholesterol giant vesicles. These studies provide insight into the mechanism of molecular recognition within the membrane milieu and may serve in designing novel HIV entry inhibitors.

Amino Acids↗

PubMed2004

Interaction with transducin depletes metarhodopsin III: a regulated retinal storage in visual signal transduction?

In the phototransduction pathway of rhodopsin, the metarhodopsin (Meta) III retinal storage form arises from the active G-protein binding Meta II by a slow spontaneous reaction through the Meta I precursor or by light absorption and photoisomerization, respectively. Meta III is a side product of the Meta II decay path and holds its retinal in the original binding site, with the Schiff base bond to the apoprotein reprotonated as in the dark ground state. It thus keeps the retinal away from the regeneration pathway in which the photolyzed all-trans-retinal is released. This study was motivated by our recent observation that Meta III remains stable for hours in membranes devoid of regulatory proteins, whereas it decays much more rapidly in situ. We have now explored the possibility of regulated formation and decay of Meta III, using intrinsic opsin tryptophan fluorescence and UV-visible and Fourier transform infrared spectroscopy. We find that a rapid return of Meta III into the regeneration pathway is triggered by the G-protein transducin (G(t)). Depletion of the retinal storage is initiated by a novel direct bimolecular interaction of G(t) with Meta III, which was previously considered inactive. G(t) thereby induces the transition of Meta III into Meta II, so that the retinylidene bond to the apoprotein can be hydrolyzed, and the retinal can participate again in the normal retinoid cycle. Beyond the potential significance for retinoid metabolism, this may provide the first example of a G-protein-catalyzed conversion of a receptor.

Animals↗

PubMed2004

[Comparison on ingredients between cultured cell and cultivated Saffron pistils].

OBJECTIVE: To compare the differences of active ingredients between tissue cultured cells and cultivated saffron pistils. METHOD: The experiment was carried out by the Fourier transform infrared spectroscopy (FTIR) spectra and high performance liquid chromatography (HPLC). RESULT: The data indicated that the species and contents active ingredients in saffron pistils from different places were different. The species of active ingredients in tissue cultured cells are less than those in cultivated saffron pistils. However, the quantity of crocin A, which showed good anticancer effect, is 2-3 times more than that in cultivated saffron pistils. CONCLUSION: The active ingredients of the tissue cultured cells are similar to those of saffron pistils, but their contents are different. Therefore, the tissue cultured cells can only be the part-substitutes of cultivated saffron pistils.

Carotenoids↗

PubMed2000

Conformational and orientation studies of artificial ion channels incorporated into lipid bilayers.

The conformational and orientation studies in lipid bilayers of 21 amino acid peptides bearing six crown ethers are reported. The compounds were designed to form artificial ion channels by stacking the crown rings, and were shown to be functional in bilayer membranes. We used Fourier transform infrared spectroscopy and CD spectropolarimetry to study the conformation of the peptides in solution and in lipid bilayers. These studies revealed that hexacrown peptides retain their alpha-helical conformation when incorporated in a lipid bilayer environment. Attenuated total reflectance spectroscopy was used to investigate the orientation of the peptides in a lipid bilayer. Results demonstrated that the peptides are not oriented at a fixed angle in membrane, but rather are in incorporation equilibrium between an active state parallel to the lipid chain and an inactive state adsorbed at the surface of the bilayer. From these results, we propose a model for the channel activity and the gating mechanism of these hexacrown peptides in bilayer membranes.

Animals↗