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Results for “Spectroscopy, Fourier Transform Infrared”

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Poly(vinylbenzyl chloride) microsphere synthesis and their chemical modifications.

Vinylbenzyl chloride (VBC) was dispersion polymerized to give monodisperse microspheres in the presence of poly(vinylpyrrolidone) (PVP) as a steric stabilizer. The effect of PVP concentration on the size and on microsphere stability during the polymerization process was investigated. Microsphere size was examined when co-stabilizer molecules were employed with PVP during the polymerization reaction. The built-in reactive chloromethyl groups of the microspheres were the sites of the nucleophilic reaction of two amino-group model molecules, glucosamine (G), a hexosamine implicated in processes of molecular recognition, and also bovine serum albumin (BSA). Elemental analyses and Fourier transform infrared spectroscopy (FTIR) spectra showed that poly(vinylpyrrolidone) was associated with the microsphere network. Elemental analyses, attenuated total reflection infrared spectroscopy (ATR-FTIR), and zeta potential measurements confirmed G and BSA links at the microsphere surface.

Capsules↗

PubMed2002

Anaerobic electrochemical corrosion of mild steel in the presence of extracellular polymeric substances produced by a culture enriched in sulfate-reducing bacteria.

The corrosion of mild steel in a seawater medium containing extracellular polymeric substances (EPS) produced by sulfate-reducing bacteria (SRB) was studied by electrochemical experiments and atomic force microscopy (AFM). Under anaerobic conditions, the corrosion of mild steel increased up to 5-fold in the presence of a 1% (w/w) EPS solution but in the absence of SRB. The enhanced corrosion is mainly due to the oxidizing power of EPS with a reduction potential of E1/2 at -0.54 V (saturated calomel electrode), which is 0.4 V above that of hydrogen reduction. The electrochemical reduction of EPS provides a couple to iron oxidation, as demonstrated by H-shaped cell experiments in which the steel sample and EPS are not in physical contact but are ionically connected via the solution and electronically connected through an external wire. Fourier transformation infrared spectroscopy and X-ray photoelectron spectroscopy showed that EPS derived from SRB are comprised of 60% proteins, 37% polysaccharides, and 3% hydrocarbons. The XPS results showed that, upon corrosion, polysaccharide components were mostly converted to hydrocarbons.

Biofilms↗

PubMed2000

Trehalose expression confers desiccation tolerance on human cells.

Many organisms that withstand desiccation express the disaccharide trehalose. We have now expressed the otsA and otsB genes of Escherichia coli, which encode trehalose biosynthetic enzymes, in human primary fibroblasts using a recombinant adenovirus vector. Infected cells produced increased amounts of trehalose with increasing multiplicity of infection (MOI). Human primary fibroblasts expressing trehalose could be maintained in the dry state for up to five days. Fourier transform infrared spectroscopy indicated that dry, but viable, human cells contained no detectable water. This study shows that mammalian cells can be engineered to retain viability in the absence of water.

Bacterial Proteins↗

PubMed2000

Novel beta-emitting poly(ethylene terephthalate) surface modification.

Restenosis after percutaneous interventions in coronary and peripheral arteries leads to repeat procedures and surgery in a significant number of patients. We have previously demonstrated that irradiation of an arterial site using an endovascular source (brachytherapy) is highly effective in preventing the restenotic process. To this end, a novel beta radiation delivery system was developed, based on the adsorption of (32)P (o-phosphoric acid) by pH-sensitive chitosan hydrogel on a poly(ethylene terephthalate) (PET) balloon surface. The PET balloon surface was treated with oxygen plasma and coated with chitosan hydrogel. Covalent bonds, ionic bonds, and hydrogen bonds all contribute to the adhesion between chitosan hydrogel and PET. In the aqueous phosphoric acid (PA) solution, the -NH(2) groups of chitosan were protonated by PA and the adsorption of PA occurred at the same time. The effect of PA concentration and temperature on adsorption efficiency and kinetics were studied. More than 70% PA was adsorbed on the sample surface in 0.2 mM PA solution. The surface of samples was also investigated by attenuated total reflection-Fourier transform infrared spectroscopy and scanning electron microscopy. PET surface may be modified to carry high activity beta emitters; such materials may be useful in a therapeutic setting

Adsorption↗

PubMed2006

Electrophoretic ink using urea-formaldehyde microspheres.

A kind of electronic ink, which is supported on indium-tin-oxide (ITO) glass before polymerization, is prepared using urea and formaldehyde resin as wall materials, in which TiO(2) modified with PMMA are dispersed in tetrachloroethylene (TCE) using a mixture of oil blue dyes and charge control additive (span80). Rotary viscometer, Fourier transform infrared spectroscopy (FT-IR) and optical microscopy are used to characterize the particles, respectively. The electrophoretic mobility of the microcapsules to electric field is also investigated with two parallel electrodes.

Capsules↗

PubMed2002

Layer-by-layer nanostructured hybrid films of polyaniline and vanadium oxide.

Supramolecular structures of polyaniline (PANI) and vanadium oxide (V2O5) have been assembled via the electrostatic layer-by-layer (ELBL) technique. Strong ionic interactions and H-bonding impart unique features to the ELBL films, which are distinct from cast films obtained with the same materials. The interactions were manifested in UV-vis and Fourier transform infrared spectroscopy data. They are enhanced by the intimate contact between the components, as the films are molecularly thin, with 25 A per PANI/V2O5 bilayer.

Aniline Compounds↗

PubMed1998

Human oral mucosa studies with varying blood glucose concentration by non-invasive ATR-FT-IR-spectroscopy.

During the last few years infrared spectrometry has been investigated as a non-invasive clinical tool for improved understanding of in-vivo processes. Oral mucosa has been suggested as an especially suited subject for drug delivery and in vivo monitoring of endogenous body metabolites due to histological and physicochemical reasons. The attenuated total reflection (ATR) technique was used to characterize the outmost epidermal layer of human oral mucosa by means of Fourier-transform infrared spectroscopy. The penetration depth of the probing radiation in the mid-infrared fingerprint region, using a ZnSe-crystal for the horizontal ATR accessory, is in the order of a few micrometers so that microlayer information can be obtained by such a technique. Spectra of outer human lip and saliva components are presented for comparison. For several test persons, lip spectra were recorded during oral glucose tolerance tests. The individually varying blood glucose concentration was followed by means of frequent blood testing. Variability of the outmost microlayer has been studied using factor analysis of the ATR inner-lip spectra. There is no clear evidence that blood glucose concentration can be followed by ATR-spectroscopy of oral mucosa. Non-invasive spectroscopic methods exploiting trace signals require special attention paid to the variability due to person-to-person differences and changes in physiological conditions.

Blood Glucose↗

PubMed2005

Effect of copper on the adsorption of p-nitrophenol onto soils.

The effect of copper on adsorption of p-nitrophenol on two typical Chinese soils was investigated using a batch-equilibration method. Adsorption experiments were carried out when both copper and p-nitrophenol were adsorbed simultaneously, and when copper was previously adsorbed on soils. It was observed that adsorption of p-nitrophenol decreased with increasing copper concentrations thereby indicating a competition between copper and p-nitrophenol for occupying the adsorption sites on soils. Moisture increased the hydrated sphere and the acidity of water surrounding the cation, which further reduced the adsorption of p-nitrophenol. Fourier transform infrared spectroscopy study provided the direct evidence for the coordination of p-nitrophenol sorbed by soils with metal cation in n-hexane system. It was observed that the perturbations included a red shift of the nu(asym) (NO) band, a concomitant blue-shift of the nu(sym) (NO) band and a blue-shift of C-N band when compared with the infrared spectra obtained from water solution.

Adsorption↗

PubMed2003

Preparation of porous hydroxyapatite scaffolds by combination of the gel-casting and polymer sponge methods.

A new technique of combining the gel-casting and polymer sponge methods is introduced in this study to prepare macroporous hydroxyapatite scaffolds, which provides a better control over the microstructures of scaffolds and enhances their mechanical properties. With this technique, we were able to produce scaffolds with mechanical and structural properties that cannot be attained by either the polymer sponge or gel-casting method. The scaffolds prepared have an open, uniform and interconnected porous structure with a pore size of 200-400 microm. A compressive yield strength of approximately 5 MPa equivalent to that of cancellous bone and a compressive modulus of approximately 8 GPa similar to that of cortical bone were achieved. The pore morphology, size, and distribution of the scaffolds were characterized using a scanning electron microscope. X-ray diffraction and Fourier transform infrared spectroscopy were used to determine the crystal structure and chemical composition of scaffolds, respectively. Scaffolds with desired porosity, pore size, and geometry can be prepared by using polymer sponges of appropriate structures.

Biocompatible Materials↗

PubMed1996

Light initiation of dental resins: dynamics of the polymerization.

Literature has shown that slowing down the curing rate of light-initiated resin composites by lowering the light intensity of the light source improved the integrity of the adhesive composite-cavity interface as a result of a more gradual contraction stress development. This study investigated how the curing rate could be controlled by varying the concentrations of the photoinitiator components in BisGMA-TEGDMA resin. Conversions and curing rates were evaluated by linear contraction experiments and Fourier transform infrared spectroscopy. Curing rates could be moderated significantly be reducing the concentrations of both photoinitiator and reducing agent without affecting the conversion, provided that the light exposure with a standard dental light curing unit lasts for 60 s.

Light↗

PubMed1998

Use of a photoactivatable lipid to probe the topology of PA63 of Bacillus anthracis in lipid membranes.

The protective antigen of Bacillus anthracis is a key protein that promotes the translocation of the enzymatic moieties of the two toxins of B. anthracis into the cell cytoplasm. The membrane topology of the active form of the protective antigen (PA63) was investigated by proteolysis of PA63 inserted into liposomes containing a photoactivatable, radioactive lipid, and characterization of the N-terminal moiety of the deeply-inserted (and therefore radiolabeled) peptides. A single sequence starting at residue Ala258 was identified. Fourier-transform infrared spectroscopy showed that the protected peptide was mainly adopting a beta-sheet structure whose orientation was compatible with a transmembrane organization.

Antigens, Bacterial↗

PubMed2002

[Remote sensing FTIR and computed tomography for air pollution].

Gas concentration mapping with computed tomography-remote sensing fourier transform infrared spectroscopy demonstrates that this system and reconstruction method can be directly applied in many environmental and industrial settings. This development of reconstruction algorithm can greatly broaden the application of CT to obtain rapid reconstruction of ambient air pollution data.

Air Pollutants↗

PubMed2005

Formation of phenytoin nanoparticles using rapid expansion of supercritical solution with solid cosolvent (RESS-SC) process.

Nanoparticles are of significant importance in drug delivery. Rapid expansion of supercritical solution (RESS) process can produce pure and high-quality drug particles. However, due to extremely low solubility of polar drugs in supercritical CO(2) (sc CO(2)), RESS has limited commercial applicability. To overcome this major limitation, a modified process rapid expansion of supercritical solution with solid cosolvent (RESS-SC) is proposed which uses a solid cosolvent. Here, the new process is tested for phenytoin drug using menthol solid cosolvent. Phenytoin solubility in pure sc CO(2) is only 3 micromol/mol but when menthol solid cosolvent is used the solubility is enhanced to 1,302 micromol/mol, at 196 bar and 45 degrees C. This 400-fold increase in the solubility can be attributed to the interaction between phenytoin and menthol. Particle agglomeration in expansion zone is another major issue with conventional RESS process. In proposed RESS-SC process solid cosolvent hinders the particle growth resulting in the formation of small nanoparticles. For example, the average particle size of phenytoin in conventional RESS process is 200 nm whereas, with RESS-SC process, the average particle size is 120 nm, at 96 bar and 45 degrees C. Similarly at 196 bar and 45 degrees C, 105 nm average particles were obtained by RESS and 75 nm average particles were obtained in RESS-SC process. The particles obtained were characterized by Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), dynamic light scattering (DLS) and differential scanning calorimetery (DSC) analyses. Phenytoin nanoparticle production rate in RESS-SC is about 400-fold more in comparison to that in RESS process.

Anticonvulsants↗

PubMed1999

Interfacial binding of cutinase rather than its catalytic activity determines the steady state interfacial tension during oil drop lipid hydrolysis.

Hydrolysis of triglycerides by cutinase from Fusarium solani pisi causes in oil drop tensiometer experiments a decrease of the interfacial tension. A series of cutinase variants with amino acid substitutions at its molecular surface yielded different values of the steady state interfacial tension. This tension value poorly correlated with the specific activity as such nor with the total activity (defined as the specific activity multiplied by the amount of enzyme bound) of the cutinase variants. Moreover, it appeared that at activity levels above 15% of that of wild type cutinase the contribution of hydrolysis to the decrease of the tension is saturating. A clear positive correlation was found between the interfacial tension plateau value and the interfacial binding of cutinase, as determined with attenuated total reflection Fourier transformed infrared spectroscopy (ATR-FTIR). These results indicate that the interfacial steady state level is not determined by the rate of hydrolysis, but mainly by the interfacial binding of cutinase.

Carboxylic Ester Hydrolases↗

PubMed2005

"De novo" design of peptides with specific lipid-binding properties.

In this study, we describe an in silico method to design peptides that can be made of non-natural amino acids and elicit specific membrane-interacting properties. The originality of the method holds in the capacities developed to design peptides from any non-natural amino acids as easily as from natural ones, and to test the structure stability by an angular dynamics rather than the currently-used molecular dynamics. The goal of this study was to design a non-natural tilted peptide. Tilted peptides are short protein fragments able to destabilize lipid membranes and characterized by an asymmetric distribution of hydrophobic residues along their helix structure axis. The method is based on the random generation of peptides and their selection on three main criteria: mean hydrophobicity and the presence of at least one polar residue; tilted insertion at the level of the acyl chains of lipids of a membrane; and conformational stability in that hydrophobic phase. From 10,000,000 randomly-generated peptides, four met all the criteria. One was synthesized and tested for its lipid-destabilizing properties. Biophysical assays showed that the "de novo" peptide made of non-natural amino acids is helical either in solution or into lipids as tested by Fourier transform infrared spectroscopy and is able to induce liposome fusion. These results are in agreement with the calculations and validate the theoretical approach.

Animals↗

PubMed2004

A direct route toward assembly of nanoparticle-carbon nanotube composite materials.

The preparation of nanocomposite materials from carbon nanotubes (CNTs) and metal or metal oxide nanoparticles has important implications to the development of advanced catalytic and sensory materials. This paper reports findings of an investigation of the preparation of nanoparticle-coated carbon nanotube composite materials. Our approach involves molecularly mediated assembly of monolayer-capped nanoparticles on multiwalled CNTs via a combination of hydrophobic and hydrogen-bonding interactions between the capping/mediating shell and the CNT surface. The advantage of this route is that it does not require tedious surface modification of CNTs. We have demonstrated its simplicity and effectiveness for assembling alkanethiolate-capped gold nanoparticles of 2-5 nm core sizes onto CNTs with controllable coverage and spatially isolated character. The loading and distribution of the nanoparticles on CNTs depend on the relative concentrations of gold nanoparticles, CNTs, and mediating or linking agents. The composite nanomaterials can be dispersed in organic solvent, and the capping/linking shells can be removed by thermal treatment to produce controllable nanocrystals on the CNT surfaces. The nanocomposite materials are characterized using transmission electron microscopy and Fourier transform infrared spectroscopy techniques. The results will be discussed in terms of developing advanced catalytic and sensory nanomaterials.

Gold↗

PubMed2004

Synthesis of metal-carbonyl-dendrimer-antibody immunoconjugates: towards a new format for carbonyl metallo immunoassay.

We report the preparation of metal-carbonyl-dendrimer-antibody conjugates. These metal-carbonyl-multilabeled antibodies are designed to be used in a new solid-phase-format carbonyl metallo immunoassay (CMIA). A fourth-generation polyamidoamine dendrimer was labeled with 10-25 (eta5-cyclopentadienyl)iron dicarbonyl (eta1-N-succinimidyl) entities. An antibody was chemically modified at its carbohydrate chains by a site-directed process used to preserve the antigen-antibody binding site. The antibody was then coupled with the dendrimer labeled with 10 metal carbonyl groups. An average of 1.4 labeled dendrimers were grafted per antibody molecule. These metal-carbonyl-dendrimer-antibody conjugates were used as new universal detection reagents that recognize their specific antigens. The antigens were spotted onto nitrocellulose membranes and detected by using the conjugates in combination with Fourier transform infrared spectroscopy. A detection level in the range 5-200 pmol per membrane was achieved. This approach opens the way to a new CMIA format.

Animals↗

PubMed2004

Surface modified ormosil nanoparticles.

Organically modified silanes (ORMOSIL) such as vinyl triethoxysilane readily aggregate in the aqueous cores of reverse micelles where the triethoxysilane moieties are hydrolyzed to form a hydrated silica network and the vinyl groups protruded out from the surface of the nanoparticles toward the hydrophobic side of the micellar interface. These particles are spherical and the size distribution of the particles is relatively narrow, with an average diameter of 87 nm. Surface vinyl silica nanoparticles so formed have been oxidized to surface carboxylic silica nanoparticles, followed by chemical conjugation with polyethyleneglycol amine (PEG amine) through the ethyl-3-(3-dimethylaminopropyl) (EDCI) carbodiimide reaction. The characteristic surface groups have been identified by Fourier transform infrared spectroscopy, while the size and the morphology of the particles have been studied by dynamic light scattering and transmission electron microscopy. It has been found that about 80-85% of the carboxylic groups are PEGylated during the EDCI reaction.

Micelles↗