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Results for “Spectroscopy, Fourier Transform Infrared”

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PubMed2002

Synthesis, surface properties and performance of thiosulphate-substituted plasticized poly(vinyl chloride).

Plasticized poly(vinyl chloride) (PVC) was surface modified by nucleophilic substitution of the chlorine atoms of PVC by thiosulphate in aqueous media in the presence of a phase-transfer catalyst. The properties of the modified surface were evaluated by contact angle measurements, attenuated total reflection Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and scanning electron microscopy. Migration of the plasticizer di-(2-ethylhexyl) phthalate from control as well as modified PVC was examined in hexane, in cottonseed oil and in poly(ethylene glycol)-400 (PEG-400). While the modified PVC was found to be highly migration resistant in hexane, cottonseed oil and PEG-400 extracted the plasticizer. The modified PVC was found to cause haemolysis and was cytotoxic. A possible explanation for the difference in performance of the modified material in different extraction media and its toxicity is presented from a mechanistic view of the substitution process.

Animals↗

PubMed2000

Bioactive glass serves as a substrate for maintenance of phenotype of nucleus pulposus cells of the intervertebral disc.

The objective of the study was to investigate the capability of bioactive glass 45S5 to serve as a substrate for nucleus pulposus cells in vitro. Nucleus pulposus cells were isolated from adult rabbit discs and seeded onto bioactive glass. At selected time intervals, the cells and glass were evaluated. We found that the cells rapidly attached to the substrate, colonizing it within 12 h. By 21 days, they had formed a lawn of cells over the glass substrate. DNA measurements showed a progressive increase in cell number with time. The phenotype was maintained; the cells expressed aggrecan, and collagen type II and I, but were negative for collagen type X. CD44, a cell-surface glycoprotein that binds hyaluronate, was also expressed by these cells. Electron dispersive X-ray analysis and Fourier transform infrared spectroscopy revealed calcium phosphate-rich layer formation on the substrate surface. The results of this study suggest that nucleus pulposus cell proliferation may be an anchorage dependent event, and that the cells use the calcium phosphate-rich layer to facilitate cell adhesion, and subsequent proliferation. These findings point to the importance of the conditioned bioactive glass as a substrate for nucleus pulposus cells.

Aggrecans↗

PubMed2000

Androctonin, a hydrophilic disulphide-bridged non-haemolytic anti-microbial peptide: a plausible mode of action.

Androctonin is a 25-residue non-haemolytic anti-microbial peptide isolated from the scorpion Androctonus australis and contains two disulphide bridges. Androctonin is different from known native anti-microbial peptides, being a relatively hydrophilic and non-amphipathic molecule. This raises the possibility that the target of androctonin might not be the bacterial membrane, shown to be a target for most amphipathic lytic peptides. To shed light on its mode of action on bacteria and its non-haemolytic activity, we synthesized androctonin, its fluorescent derivatives and its all-D-amino acid enantiomer. The enantiomer preserved high activity, suggesting a lipid-peptide interaction between androctonin and bacterial membranes. In Gram-positive and (at higher concentrations) Gram-negative bacteria, androctonin induced an immediate perturbation of the permeability properties of the cytoplasmic membrane of the bacterial energetic state, concomitant with perturbation of the morphology of the cell envelope as revealed by electron microscopy. Androctonin binds only to negatively charged lipid vesicles and induces the leakage of markers at high concentrations and with a slow kinetics, in contrast with amphipathic alpha-helical anti-microbial peptides that bind and permeate negatively charged vesicles, and to a smaller extent also zwitterionic ones. This might explain the selective lytic activity of androctonin towards bacteria but not red blood cells. Polarized attenuated total reflection-Fourier transform infrared spectroscopy revealed that androctonin adopts a beta-sheet structure in membranes and did not affect the lipid acyl chain order, which supports a detergent-like effect. The small size of androctonin, its hydrophilic character and its physicochemical properties are favourable features for its potential application as a replacement for commercially available antibiotics to which bacteria have developed resistance.

Adenosine Triphosphate↗

PubMed2005

Synthesis of a poly(L-lysine)-calcium phosphate hybrid on titanium surfaces for enhanced bioactivity.

Titanium has been a successful implant material owing to its excellent strength to weight ratio, toughness, and bioinert oxide surface. Significant progress has been made on the improvement of titanium's bioactivity by coating its oxide surface with calcium phosphates and bioactive molecules. Here, we report on the coating of titanium with a poly(L-lysine)-calcium phosphate hybrid material with a nanoscale texture. This hybrid coating was grown by first nucleating seed crystals of calcium phosphate, directly on the Ti surface and then exposing this surface to solutions containing Ca(2+), PO(4)(3-), and poly(L-lysine). The resultant hybrid coating was characterized by electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric analysis, X-ray photoelectron spectroscopy, and elemental analysis. This material contained 14% by weight poly(L-lysine), and this organic component decreased greatly the dimensions of the surface features, thus enhancing surface area relative to the inorganic control. The highly textured hybrid material was more susceptible than the control to acidic and enzymatic degradation. The amino acid cysteine was covalently linked to the hybrid material, demonstrating the potential of this coating for further functionalization. These hybrid coatings may prove useful in enhancing the bioactivity of titanium.

Calcium Chloride↗

PubMed2006

The mechanism of kinetic inhibition of Cu(II)-induced oxidation of low density lipoprotein by lanthanide ions.

Oral administration of lanthanum chloride (LaCl(3)) was reported to inhibit atherosclerosis in experimental animals, but the mechanism was not clear. In the present work, the effects of La(III) and other lanthanide ions (Ln(III)) on Cu(II)-induced oxidation of isolated low-density lipoprotein (LDL) and the related mechanism were investigated. By monitoring the formation of conjugated dienes (CD), low concentrations of La(III), Gd(III) and Y(III) were found to inhibit Cu(II)-induced LDL oxidation kinetically, as characterized by the prolongation of the lag time, the decrease of the maximal accumulation of CD, and the maximal rate of CD accumulation. Using 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) and alpha-(4-pyridyl-1-oxide)-N-tert-butylnitrone (4-POBN) as spin trapping agents, the electron spin resonance (ESR) results showed that La(III) and Gd(III) at low concentrations significantly decreased the level of free radicals, including alkoxyl radical (LO*), alkyl radical (L*), and a transient radical, alkylperoxyl radical (LOO*), generated during LDL oxidation induced by Cu(II). In addition, Fourier-transform infrared spectroscopy (FT-IR) study revealed that La(III) might cause the conformational change and the less aggregation of apolipoprotein B-100 (apoB) in LDL, as demonstrated by the decreasing contents of alpha-helix, intermolecular beta-sheet, unordered structure and beta-turns, and the increasing contents of intramolecular beta-sheet and beta-strands. The inhibitory effect of Ln(III) on Cu(II)-induced LDL oxidation was discussed on the basis of the decreased free radical level and the second structural changes of apoB in LDL.

Apolipoprotein B-100↗

PubMed2000

[Study on the formation mechanism of soluble complexes containing bovine serum albumin and calcium hydroxyapatite and calcium carbonate].

Fourier transform infrared spectroscopy was used to study the composition and microstructure of soluble complexes produced by different initial mole ratios of bovine serum albumin(BSA) and calcium hydroxyapatite [Ca10(OH)2(PO4)6] and calcium carbonate (CaCO3) in aqueous solution. The band shifts and intensity variations suggested that calcium complexes with multiple ligands such as BSA, apatite, carbonate as well as the hydrogen bond network formed in titled system. The interactions increased the solubility of Ca10 (OH)2(PO4)6 and CaCO3 and the composition of soluble complexes is nonstoichiometric. The results provided an ideal model to investigated biomineralization process.

Calcium Carbonate↗

PubMed2003

Identification of polyhydroxyalkanoate (PHA)-producing Bacillus spp. using the polymerase chain reaction (PCR).

AIMS: The aim of the work was to develop efficient method to identify polyhydroxyalkanoate (PHA)-producing species of Bacillus from numerous soil isolates of bacteria. Identification of the isolates and characterization of the PHA produced by strains positive on the polymerase chain reaction (PCR) was envisaged. METHODS AND RESULTS: Different bacteria isolated from soil were screened by PCR using two sets of primers designed for Bacillus megaterium. Amongst 23 isolates examined, the DNA of 12 isolates reacted positively with the primers giving amplicons identical in size to that obtained from B. megaterium. The isolates which were identified as strains of B. sphaericus, B. circulans, B. brevis and B. licheniformis, produced 11- 41% of PHA in biomass, in sucrose-containing medium, over a growth period of 24-72 h. The nature of the PHA thus produced was analyzed by Fourier transform infrared spectroscopy, gas chromatography and by nuclear magnetic resonance (NMR) and found to contain polyhydroxy butyrate and polyhydroxyvalerate. CONCLUSIONS: The results indicate that most of our isolates from different species contained the B. megaterium type of PHA synthase. Bacillus licheniformis appeared to belong to another group as it did not react with both sets of primers. SIGNIFICANCE AND IMPACT OF THE STUDY: This study shows the universality of the B. megaterium type of PHA synthase in soil isolates of Bacillus. Some variations were also found.

Acyltransferases↗

PubMed2005

Effect of progesterone on DPPC membrane: evidence for lateral phase separation and inverse action in lipid dynamics.

Interactions of progesterone with zwitterionic dipalmitoyl phosphatidylcholine (DPPC) multilamellar liposomes were investigated as a function of temperature and progesterone concentration by using three non-invasive techniques namely Fourier transform infrared spectroscopy, turbidity at 440 nm, and differential scanning calorimetry. The results reveal that progesterone changes the physical properties of DPPC bilayers by decreasing the main phase-transition temperature, abolishing the pre-transition, broadening the phase-transition profile, disordering the system both in gel and liquid crystalline phase, increasing the dynamics at low concentrations whereas stabilizing the membrane at high concentrations, and inducing phase separation. Progesterone does not change the hydration of the CO groups, while it strengthens the hydrogen bonding between the PO2- groups of lipids and the water molecules around.

1,2-Dipalmitoylphosphatidylcholine↗

PubMed2004

Amyloid fibril formation by a partially structured intermediate state of alpha-chymotrypsin.

Here we investigated the effects of 2,2,2-trifluoroethanol (TFE) on the structure of alpha-chymotrypsin. The protein aggregates maximally in 35% (v/v) TFE. Congo red and thioflavin-T binding experiments suggest that the aggregates induced by TFE have amyloid-like properties, and transmission electron microscopy data show that these aggregates have a fibrilar morphology. Fluorescence, circular dichroism, anilino-8-napthalene sulfonate binding, and Fourier-transformed infrared spectroscopy data suggest that formation of a partially structured intermediate state precedes the onset of the aggregation process. The native beta-barrel structure of alpha-chymotrypsin appears to be disrupted in the partially structured intermediate state in favour of a non-native extended beta-sheet conformation with exposed hydrophobic surfaces. The protein becomes "sticky" under these conditions and aggregates into amyloid-like structures. The data support the hypothesis that amyloid formation involves the ordered self-assembly of partially folded species that are critical soluble precursors of fibrilar aggregates.

Amyloid↗

PubMed1997

Effect of added carbohydrates on membrane phase behavior and survival of dried Lactobacillus plantarum.

The relation between the protective effect of externally added carbohydrates on Lactobacillus plantarum cells during air-drying and the phase behavior of cell membranes was studied. The residual activity after drying could be improved from 44% in the control to 79 and 66% after the addition of sorbitol and maltose, respectively, whereas trehalose addition resulted in a residual activity of 30%. Membrane phase transition temperatures (Tm) were determined in intact hydrated and dry cells, using Fourier transform infrared spectroscopy. The Tm of hydrated cells was 4 degrees C, increasing to only 20 degrees C after drying. Because endogenous soluble sugars were absent, this phase behavior is attributed to the structure of the predominant phospholipids, PG and lysyl-PG. The restricted increase of Tm is held responsible for the survival of part of the cells. The added maltose, trehalose, and sorbitol did not influence Tm in vivo. We suggest that the effective carbohydrates act through their free radical scavenging activity and not by direct interaction with the polar lipid headgroups.

Carbohydrates↗

PubMed2006

Preliminary studies of the physical stability of a glucagon-like peptide-1 derivate in the presence of metal ions.

The physical stability and the secondary structure of a glucagon-like peptide-1 derivative were investigated in the presence of the metal ions Al(3+), Zn(2+), Mg(2+), and K(+), known as possible leachables from container-closure systems. Metal ions were investigated in concentrations of 0-50 ppm. Test solutions of the peptide were exposed to elevated temperature (25 degrees C) and rotation (37 degrees C) for up to 4 weeks. The samples were examined by nephelometry, thioflavine T fluorescence, and Fourier-transform infrared spectroscopy. Readily prepared test solutions were examined by tryptophan fluorescence. The stability profiles were unchanged after addition of Mg(2+) and K(+) in 0-50 ppm concentrations. However, a concentration-dependent increase in thioflavine intensities was observed after addition of Al(3+) and Zn(2+). The destabilising effect of Al(3+) and Zn(2+) was furthermore confirmed by FTIR as the secondary structure of the peptide changed from predominantly alpha-helix to a higher beta-sheet content. Additionally Al(3+) changed the secondary structure of the peptide using Trp fluorescence.

Aluminum↗

PubMed2005

Thermal stability of outer membrane protein porin from Paracoccus denitrificans: FT-IR as a spectroscopic tool to study lipid-protein interaction.

Lipid protein interactions play a key role in the stability and function of various membrane proteins. Earlier we have reported the extreme thermal stability of porin from Paracoccus denitrificans reconstituted into liposomes. Here, we used Fourier transform infrared spectroscopy for a label free analysis of the global secondary structural changes and local changes in the tyrosine microenvironment. Our results show that a mixed lipid system (non-uniform bilayer) optimizes the thermal stability of porin as compared to the porin in pure lipids (uniform bilayer) or detergent micelles. This is in line with the fact that the bacterial outer membrane is a dynamic system made up of lipids of varying chain lengths, head groups and the barrel wall height contacting the membrane is uneven.

Cloning, Molecular↗

PubMedDate not supplied

Nanoscale structure of poly(ethylene glycol) hybrid block copolymers containing amphiphilic beta-strand peptide sequences.

This paper discusses the solid state and melt nanoscale structure of a series of novel poly(ethylene glycol) (PEG) hybrid di- and triblock copolymers, which contain amphiphilic beta-strand peptide sequences. The block copolymers have been prepared via solid-phase synthesis, affording perfectly monodisperse peptide segments with a precisely defined alpha-amino acid sequence. Attenuated total reflection Fourier transform infrared spectroscopy and X-ray scattering experiments indicate that the self-assembly properties of the peptide sequences are retained upon conjugation to PEG and mediate the formation of an ordered superstructure consisting of alternating PEG layers and peptide domains with an highly organized antiparallel beta-sheet structure. The results suggest that combination of biological structural motifs with synthetic polymers may be a versatile strategy for the development of novel self-assembled materials with complex internal structures and the potential to interface with biology.

Amino Acid Sequence↗

PubMed1995

Biocompatibility of polysulfone I. Surface modifications and characterizations.

Surface treatments by nonionic surfactant (Brij) coating and air-plasma glow discharge treatment onto polysulfone have been investigated to improve its surface properties. Surface treated samples were characterized by measurement of contact angle by a goniometer, Fourier transform infrared spectroscopy in the attenuated total reflectance mode (FTIR-ATR), and electron spectroscopy for chemical analysis (ESCA). The contact angles of the nonionic surfactant coated films decreased from 66.6 +/- 2.1 degrees to nearly 0 degrees due to hydrophilic polyethylene oxide (PEO) chain segment of the nonionic surfactant, and those of air-plasma treated films also decreased from 66.6 degrees to about 22 degrees with a treatment time of less than 5 s. ESCA analysis of air-plasma treated films indicates the incorporation of oxygen molecules onto polysulfone surface lowers the water contact angle. These modified techniques can be used to prevent platelet adhesion onto polysulfone surfaces.

Adsorption↗

PubMed2006

Controlled delivery of recombinant hirudin based on thermo-sensitive Pluronic F127 hydrogel for subcutaneous administration: In vitro and in vivo characterization.

Here we investigated thermo-sensitive Pluronic(R) F127 (PF127) hydrogel for the controlled release of peptide and protein drugs after subcutaneous injection, using an antithrombotic polypeptide, recombinant hirudin variant-2 (rHV2), as the model drug. The in vitro release experiment performed with a membrane-less model at 37 degrees C showed that the release of antithrombotic activity of rHV2 from PF127 gel followed zero-order kinetics and correlated well with the weight percentage of PF127 dissolved, indicating a dissolution-controlled release mechanism. The in vivo result obtained after subcutaneous injection of rHV2-loaded PF127 gel in normal rats demonstrated that PF127 gel improved the bioavailability, prolonged the antithrombotic effect of rHV2, and induced detectable plasma rHV2 concentration for a longer time in comparison with rHV2 aqueous solution. Differential scanning calorimetry, dynamic light scattering and Fourier transform infrared spectroscopy provided evidence of the interaction between PF127 and rHV2, but such interaction was unlikely to interfere the feasibility of this drug delivery system. Our current in vitro and in vivo study suggested that PF127 gel may be useful as an injectable delivery vehicle for peptides and proteins with short half-lives to prolong their therapeutic effect, increase their bioavailability and improve the clinic outcome.

Animals↗

PubMed2004

LC-MS/MS and FT-IR analyses of stones from a patient with Crohn's disease: a case report.

This report describes the unusual case of a patient affected by Crohn's disease suffering from intestinal obstruction with recurrent occlusive symptoms not due to the intestinal disease, but to the presence of two calcified foreign bodies in the pelvis. The stones were surgically removed and analysed by reverse-phase liquid chromatography coupled to UV diode array detection and mass spectrometry (LC-UV-DAD-MS/MS), Chromatoprobe-MS/MS and by Fourier-transform-infrared spectroscopy (FT-IR) techniques. The combined mass spectrometric approaches allowed unequivocally to identify 5-aminosalicylic acid (5-ASA) in stone 1, and to demonstrate that its formation was due to an unmodified 5-ASA tablet, a formulation that must undergo complete dissolution in the small bowel. The second stone was constituted by a solid layer (no solvent-extractable material) identified by FT-IR as a polystyrene fragment. This indicates that accidental ingestion of a plastic material, followed by its calcification, was responsible for its formation.

Adult↗

PubMed2006

Polymorphism, pseudopolymorphism, and amorphism of peracetylated alpha-, beta-, and gamma-cyclodextrins.

Polymorphism, pseudopolymorphism, and amorphism of hexakis(2,3,6-tri-O-acetyl)-alpha-cyclodextrin (TAalphaCyD), heptakis(2,3,6-tri-O-acetyl)-beta-cyclodextrin (TAbetaCyD), and octakis(2,3,6-tri-O-acetyl)-gamma-cyclodextrin (TAgammaCyD) were investigated using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), powder X-ray diffractometry (XRPD), Fourier transform infrared spectroscopy (FTIR) and optical microscopy. An anhydrous and a bi-hydrate crystalline forms of TAalphaCyD, two monotropic anhydrous polymorphs and three pseudopolymorphs (i.e. methanolate, hydrate, and isopropanolate-hydrate) of TAbetaCyD, as well as two monotropic anhydrous polymorphs and isostructural pseudopolymorphs (e.g. hydrate and isopropanolate-hydrate) of TAgammaCyD were isolated and characterized. The amorphous forms of each TACyD were also obtained. Thermal data for desolvation of TAalphaCyD.2H2O and TAbetaCyD.CH3OH were reconciled with their crystal packing features. Melting temperatures and enthalpies of the crystalline forms of each TACyD can be referred to for possible solid-state interactions with drugs.

Calorimetry, Differential Scanning↗

PubMed1999

Surface modification of A12O3 bioceramic by NH2+ ion implantation.

Ion implantation technique was applied to graft the -NH2 amidogen radicals onto the surface of Al2O3 bioceramic. Fourier transform infrared spectroscopy (FTIR) was used to confirm the presence of the implanted radicals on the Al2O3 ceramic surface. It was found that the amount of grafted amidogen radicals was proportional to the dosage of NH2+ ions used during the ion implantation. Furthermore, when implantation energy of 100 keV was used, maximum amount of -NH2 radicals would be grafted on the Al2O3 ceramic surface. The biocompatibility of the implanted Al2O3 ceramic was also investigated, and the results indicate that the implanted surface has better biocompatibility with animal bone tissue than the plain ceramic surface.

Aluminum Oxide↗