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PubMed2005

Biochemical and biophysical changes induced by fungicide sodium diethyl dithiocarbamate (SDD), in phytocystatin purified from Phaseolus mungo (Urd): a commonly used Indian legume.

Phytocystatins are the plant thiol protease inhibitors involved in several reaction mechanisms of the plant system like regulation of proteolytic activity and storage of proteins. Biochemical and biophysical changes induced by fungicide SDD in phytocystatin purified from Phaseolus mungo have been investigated in terms of mass spectroscopy, Fourier transform infrared spectroscopy, and fluorescence spectroscopy, at pH 7.0, with varying fungicide concentrations (1-9 mM) and a time of incubation ranging from 2 to 8 h at 37 degrees C, with a fixed cystatin concentration (1.5 mM). Reactive oxygen species responsible for inhibitor damage were also investigated, and thiourea was found to scavenge the free radicals generated by SDD. FTIR analysis indicates a significant conformational transition from alpha-helix to beta-sheet structure; quenching of fluorescence is evident by fluorescence spectroscopy. The activity assay showed a decrease in inhibitory activity, as well as a fragmentation of the inhibitor was observed in electrophoresis. Results obtained implicate that exposure of phytocystatins to SDD involves physicochemical changes in cystatins leading to damage and a decrease in the activity of the inhibitor.

Chemical Phenomena↗

PubMed2002

Structural, kinetic and cytotoxicity aspects of 12-28 beta-amyloid protein fragment: a reappraisal.

A chemical, structural and biological study on the beta-amyloid peptide beta12-28 is reported which was carried out in order to assess the feasibility using this peptide fragment as a model of the natural beta-amyloid protein. The aggregation properties of beta12-28 have been investigated by pulse field-gradient NMR spectroscopy, Fourier transform infrared spectroscopy and transmission electron microscopy. The results obtained suggest that beta12-28 behaviour is comparable to that of the natural beta-amyloid protein although kinetically slower. Translational diffusion coefficients obtained by NMR on an aged beta12-28 solution suggest that the soluble peptide fraction is composed of oligomeric intermediates adopting an extended ellipsoidal assembly rather than a spherical one. The beta12-28 peptide proved to be cytotoxic in PC12 cell cultures as monitored by the MTT assay, although a lack of reproducibility was observed in the dose-response experiments.

Amino Acid Sequence↗

PubMed2004

Plasma synthesis of carbon magnetic nanoparticles and immobilization of doxorubicin for targeted drug delivery.

Using dense medium plasma technology, carbon magnetic nanoparticles (CMNP) were synthesized at room temperature and atmospheric pressure. Based on results from X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy and scanning electron microscopy, we conclude that these nanoparticles are composed of spherical particles, 40-50 nm in diameter, with iron/iron oxide particles dispersed in a carbon-based host-structure. Thermal gravimetry/differential thermal gravimetry analysis shows these nanoparticles are stable to temperatures as high as 600 degrees C. The synthesized CMNP were treated by argon-plasma, aminated with ethylene diamine and subsequently activated by generating aldehyde groups on them. Free doxorubicin (DOX) molecules were then immobilized onto the surfaces of activated CMNP particles to form CMNP-DOX conjugates. The corresponding loading efficiency was determined. The in vitro antiproliferative activity of immobilized doxorubicin in the conjugates was demonstrated in tumor cell cytotoxicity assays. It is suggested that this CMNP-DOX system can be used for targeted drug-delivery systems.

Animals↗

PubMed2003

Characterization and dissolution behavior of sputtered calcium phosphate coatings after different postdeposition heat treatment temperatures.

There is a lack of correlation between specific properties of hydroxyapatite coating surfaces, osseointegration processes, and implant success. The aim of this study was to evaluate the relationship between well-characterized structural and chemical properties of radio-frequency sputtered calcium phosphate (CaP) coatings and their dissolution behavior. Sputtered CaP coatings were evaluated as-sputtered (non-heat treated) or after 1 hour of postsputter heat treatments at 400 degrees C or 600 degrees C. All coatings were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and contact angle measurement. The dissolution behavior of CaP coatings in the presence and absence of proteins was also investigated. It was observed from this study that as-sputtered CaP coatings were amorphous. The 400 degrees C heat-treated CaP coatings exhibited low crystallinity (1.9% +/- 0.4%), whereas the 600 degrees C heat-treated CaP coatings were highly crystalline (67.0% +/- 2.4%). The increase of Ca/P ratio, PO4/HPO4 ratio, and the number of PO4 peaks were observed to be consistent with the increase in heating temperature and the degrees of coating crystallinity. Phosphorus ions released from CaP coatings decreased with the increase of crystallinity of CaP coatings. In addition, immersion of CaP coatings in media containing proteins resulted in an increase in P ions released as compared with coatings immersed in media without proteins. It was concluded that the degree of CaP coating crystallinity can be controlled by varying the postdeposition heat-treatment temperature. It was also concluded that, aside from coating crystallinity, dissolution and reprecipitation of the coatings can be controlled by knowing the presence of proteins in the media and PO4/HPO4 ratio within the coatings.

Calcium Phosphates↗

PubMed2006

Binding analysis of glycyrrhetinic acid to human serum albumin: fluorescence spectroscopy, FTIR, and molecular modeling.

Fluorescence spectroscopy, Fourier transform infrared spectroscopy (FTIR), and molecular modeling methods were employed to analyze the binding of glycyrrhetinic acid (GEA) to human serum albumin (HSA) under physiological conditions with GEA concentrations from 4.0x10(-6) to 4.5x10(-5) mol L(-1). The binding of GEA to HSA was via two types of sites: the numbers of binding site for the first type was near 0.45 and for the second type it was approximately 0.75. The binding constants of the second type binding site were lower than those of the first type binding site at corresponding temperatures, the results suggesting that the first type of binding site had high affinity and the second binding site involved other sites with lower binding affinity and selectivity. The fluorescence titration results indicated that GEA quenched the fluorescence intensity of HSA through static mechanism. The FTIR spectra evidence showed that the protein secondary structure changed with reduction of alpha-helices about 26.2% at the drug to protein molar ratio of 3. Thermodynamic analysis showed that hydrogen bonds were the mainly binding force in the first type of binding site, and hydrophobic interactions might play a main role in the second type of binding site. Furthermore, the study of computational modeling indicated that GEA could bind to the site I of HSA and hydrophobic interaction was the major acting force for the second type of binding site, which was in agreement with the thermodynamic analysis.

Glycyrrhetinic Acid↗

PubMed2006

Novel photoinduced grafting-chemical reaction sequence for the construction of a glycosylation surface.

Carbohydrates play a major role in many recognition events, such as blood coagulation, immune response, fertilization, cell growth, embryogenesis, and cellular signal transfer, which are essential for the survival of living entities. Synthetic carbohydrate-based polymers, so-called glycopolymers, are emerging as important well-defined tools for investigating carbohydrate-based biological processes and for simulating various functions of carbohydrates. In this work, we present a facile strategy for the formation of glycopolymer tethered on polypropylene microporous membrane surface. Acrylamide was grafted onto the polypropylene microporous membrane surface by photoinduced graft polymerization in the presence of benzophenone. The amide groups of grafted poly(acrylamide) were then transformed to primary amine groups by the Hofmann rearrangement reaction. Quantificational evaluation of the rearrangement reaction was carried out by ninhydrin method and mass weighting. Sugar moieties were coupled with the grafted functional layer to form glycopolymer by the reaction between primary amine groups and carbohydrate lactones. The grafting of acrylamide, the conversion of amide groups to amine groups, and the coupling of sugar moieties were confirmed by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy combined with surface morphology observation by scanning electron microscopy.

Carbohydrates↗

PubMed2006

Preparation, characterization and microhardness study of semi interpenetrating polymer networks of polyvinyl alcohol and crosslinked polyacrylamide.

Semi-IPNs based on polyvinyl alcohol (PVA) and crosslinked polyacrylamide (PAM) were prepared and characterized. Various compositions of semi-interpenetrating polymer networks (semi-IPNs) were prepared by varying concentrations of PVA, acrylamide (AM) and crosslinker N,N'-methylene bis acrylamide (MBA) in the feed mixtures and polymerized using a suitable redox system comprising of potassium persulphate and metabisulphite. The prepared semi-IPNs were characterized by fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and X-ray diffraction (XRD) methods. The prepared semi-IPNs were also investigated for microhardness measurements.

Acrylamides↗

PubMed1998

Lipophosphoglycan of Leishmania donovani inhibits lipid vesicle fusion induced by the N-terminal extremity of viral fusogenic simian immunodeficiency virus protein.

Lipophosphoglycan (LPG), the major glycoconjugate of Leishmania parasites, was recently shown to be a potent inhibitor of viral infection. The mechanism by which this natural membrane amphiphile compound inhibits membrane fusion was investigated in this study using a simple model membrane system and a synthetic peptide corresponding to the fusion peptide of simian immunodeficiency virus (SIV). At low concentration (< 10 microM), LPG inhibits SIV-induced lipid mixing of large unilamellar vesicles composed of an equimolar mixture of egg phosphatidylcholine and egg phosphatidylethanolamine. Importantly, this inhibition was observed regardless of which LPG was inserted in the inner monolayer, the outer monolayer or both sides of the membrane, suggesting that the inner monolayer plays a determining role in membrane fusion. Fourier transform infrared spectroscopy revealed that LPG induced a conformational change of SIV fusion peptide without affecting its capacity to interact with the lipid membrane. This structural change was shown not to depend on the LPG localization and was observed even when LPG was exclusively associated to the inner lipid membrane.

Animals↗

PubMed1994

Membrane interaction and conformational properties of the putative fusion peptide of PH-30, a protein active in sperm-egg fusion.

A peptide representing the putative fusion domain of PH-30, a sperm surface protein involved in sperm-egg fusion, was synthesized, and its interaction with model lipid membranes was characterized by biophysical methods. While the peptide binds to the vesicles composed of both neutral and acidic lipids, the apparent affinity is significantly higher for the latter lipid class. The intervesicular lipid mixing assay suggests that the synthetic peptide is able to induce fusion of large unilamellar vesicles. Circular dichroism and Fourier-transform infrared spectroscopy show that while in an aqueous buffer the peptide exists in an essentially unordered conformation, binding to the membranes results in a conformational transition to a beta-structure. These data indicate that the fragment identified on the alpha-subunit of PH-30 as a putative fusion peptide is indeed a good candidate for this role. However, in contrast to what has been proposed for some viral fusion peptides, the PH-30 fusion domain is highly unlikely to act as an insertional "sided" helix.

ADAM Proteins↗

PubMed2004

Hydrogen bonding interactions between indole and benzenoid-pi-bases.

The NH-pi interactions of indole with benzene, naphthalene, phenanthrene, toluene, m-xylene, and mesitilene, in carbon tetrachloride solutions, have been studied by Fourier transform infrared spectroscopy. The experiments, carried out on the NH stretching band of indole, prove the formation of 1:1 complexes in which the NH bond of indole is engaged. The NH frequency shifts are independent of the number of rings in the base, but they progressively increase as the electron density is enhanced by methylation. The association constants increase with the increase of both, the number of rings and the methyl groups on the base. At higher base concentrations, further shifts on the free NH and associated bands indicate the formation of 1:2 complexes, which suggest hybride NH-pi and van der Waals interactions between one indole ring and two benzene acceptor molecules.

Benzene↗

PubMed2004

The assignment of the different infrared continuum absorbance changes observed in the 3000-1800-cm(-1) region during the bacteriorhodopsin photocycle.

The bleach continuum in the 1900-1800-cm(-1) region was reported during the photocycle of bacteriorhodopsin (bR) and was assigned to the dissociation of a polarizable proton chain during the proton release step. More recently, a broad band pass filter was used and additional infrared continua have been reported: a bleach at >2700 cm(-1), a bleach in the 2500-2150-cm(-1) region, and an absorptive behavior in the 2100-1800-cm(-1) region. To fully understand the importance of the hydrogen-bonded chains in the mechanism of the proton transport in bR, a detailed study is carried out here. Comparisons are made between the time-resolved Fourier transform infrared spectroscopy experiments on wild-type bR and its E204Q mutant (which has no early proton release), and between the changes in the continua observed in thermally or photothermally heated water (using visible light-absorbing dye) and those observed during the photocycle. The results strongly suggest that, except for the weak bleach in the 1900-1800-cm(-1) region and >2500 cm(-1), there are other infrared continua observed during the bR photocycle, which are inseparable from the changes in the absorption of the solvent water molecules that are photothermally excited via the nonradiative relaxation of the photoexcited retinal chromophore. A possible structure of the hydrogen-bonded system, giving rise to the observed bleach in the 1900-1800-cm(-1) region and the role of the polarizable proton in the proton transport is discussed.

Bacteriorhodopsins↗

PubMedDate not supplied

Study of vibrational spectra of polyaniline doped with sulfuric acid and phosphoric acid.

Vibrational spectra of insulator emeraldine base (EB) form of polyaniline and electrical conductive sulfuric acid- and phosphoric acid-doped emeraldine salts (ES) were studied in the region of 4000-400 cm(-1) at ambient temperature by Fourier transform infrared spectroscopy. Infrared transmittance spectra of EB and ES were investigated to understand the bonding behavior of different organic and inorganic groups present in the polymeric chains and their structural variations on protonation by sulfate or phosphate ion inclusion in the polymer salt network. These studies revealed the para-coupling of deformed disubstituted benzenoid (B) and quinoid (Q) rings with ends capped predominantly by (B4Q1) units. The deformation of B and Q rings was confirmed by the appearance of many weak bands, very weak bands, and satellite structures in strong transmittance peaks of polymeric chain-constituting groups. Protonation takes place at the nitrogen sites of Q rings and forms semiquinone radical ions in ES. The vibrational bands pertaining to B rings, Q rings, B4Q1 units, semiquinone segment, sulfate ions, and phosphate ions were observed and assigned from these measurements. The shift in peak position of some bands with gain or loss in intensity and appearance of some new bands were observed in sulfuric acid- and phosphoric acid-doped ES spectra. These variations are attributed to the formation of new structural groups in ES on protonation and a change in crystalline field by sulfate and phosphate ion doping for crosslinking the polymeric chains.

Aniline Compounds↗

PubMed2005

Miscibility and hydrogen-bonding interactions in biodegradable polymer blends of poly(3-hydroxybutyrate) and a partially hydrolyzed poly(vinyl alcohol).

Miscibility and hydrogen-bonding interactions, as well as the morphological properties, of biodegradable polymer blends of poly(3-hydroxybutyrate) (PHB) and a 80% hydrolyzed poly(vinyl alcohol) (PVA80) were studied using Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC). It was found that PHB is miscible with PVA80 in the amorphous phase over the whole composition range. PVA80 or PHB assumes the amorphous state when its content in the blend is lower than 30 or 20 wt %, respectively. Due to the heavy overlapping of C=O stretching bands from both PVA80 and PHB and the nonmeasurable peak shift in the OH stretching band region, hydrogen-bonding interactions between the OH group of PVA80 and the C=O group of PHB were not detectable at room temperature, but were observed at a higher temperature of 180 degrees C. This is because hydrogen-bonding interactions are promoted above the melting points of these two crystalline polymers, by increasing the mixing entropy and reducing the Deltachi effect. Blending PHB with PVA80 does not have a significant effect on the OH groups of PVA80 that are hydrogen bonded with each other. Instead, the C=O groups of PHB dispossess some of the OH groups that are hydrogen bonded to the C=O groups of PVA80, which gives rise to the miscibility between PVA80 and PHB in the amorphous phase.

Biodegradation, Environmental↗

PubMed2005

Matrix isolation FTIR spectroscopic and theoretical study of dimethyl sulfite.

The preferred conformations of dimethyl sulfite and their vibrational spectra were studied by matrix-isolation Fourier transform infrared spectroscopy and theoretical methods (density functional theory (DFT) and Moller-Plesset (MP2), with basis sets of different sizes, including the quadruple-zeta, aug-cc-pVQZ basis). Five minima were found at these levels of theory. At the MP2/6-31++G(d,p) and DFT/B3LYP/aug-cc-pVQPZ levels, the GG conformer (where the O-S-O-C dihedral angles are 73.2 and 70.8 degrees ) resulted in the conformational ground state. At the highest level of theory used, the GT conformer (O-S-O-C = +68.5 and -173.2 degrees ) is 0.83 kJ mol(-1) higher in energy than the GG form, while conformer GG' (O-S-O-C = +85.7 and -85.7 degrees ) has a relative energy of 1.18 kJ mol(-1). The remaining two conformers (G'T and TT) are high-energy forms and not experimentally relevant. In consonance with the theoretical predictions, conformer GG was found to be the most stable conformer in the gaseous phase as well as in the low-temperature matrices. Annealing of the argon matrices first promotes the GG'-->GT isomerization, which is followed by conversion of GT into the most stable conformer. There is no evidence of occurrence of GG'-->GG direct conversion in the low-temperature matrices. On the other hand, during deposition of the xenon matrices conformer GG' totally converts to conformer GT. Two observations demonstrated this fact: no evidence of bands corresponding to GG' were observed in xenon matrices and the GG/GT intensity ratio became similar to the GG/(GT + GG') intensity ratio observed in argon matrices. All these results could be explained by taking into account the relative values of the theoretically predicted energy barriers for the different isomerization processes: GG'-->GT, 1.90 kJ mol(-1); GT-->GG, 9.64 kJ mol(-1); and GG'-->GG, 19.46 kJ mol(-1).

Argon↗

PubMed1999

Enhanced growth of human vascular endothelial cells on negative ion (Ag-)-implanted hydrophobic surfaces.

Silver negative ions (Ag-) were implanted to an insulator, polystyrene, in a relatively low ion energy ranging from 5 to 30 keV, and in a dose ranging from 10(14) to 6 x 10(16) ions. cm-2. Surfaces of Ag--implanted polystyrene were studied by means of secondary ion mass spectrometry, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and micro-Raman spectroscopy, and contact angle measurement. As a result of Ag- implantation, the polystyrene surfaces underwent degradation, thereby becoming more hydrophilic with increasing dose and ion energy except an ion energy of 30 keV. The Ag- implantation in polystyrene led to enhanced growth of human vascular endothelial cells, which grew to more extent with increased hydrophilicity of Ag--implanted surfaces except an ion energy of 30 keV. Polystyrene surfaces on which Ag- were implanted up to an ion energy of 30 keV caused the same hydrophobic level as polystyrene surface itself. Nevertheless, the Ag--implanted polystyrene showed relatively good biocompatibility different from polystyrene. Such an improvement in cell adhesion may be related to the formation of a graphite-like structure on polystyrene surfaces by a Ag--implanted process. Moreover, upon plating in a high cell density, human vascular endothelial cells survived even on the polystyrene region of Ag--implanted polystyrene for longer than 1.5 months, while the cells did not grow on untreated polystyrene in the same culture conditions.

Biocompatible Materials↗

PubMed2002

Amphiphilic beta-cyclodextrins modified on the primary face: synthesis, characterization, and evaluation of their potential as novel excipients in the preparation of nanocapsules.

The purpose of this study was to synthesize and characterize amphiphilic beta-cyclodextrins modified on the primary face with substituents of varying chain lengths (C6 and C14) and bond types (ester or amide). We also aimed to evaluate the potentiality of the new amphiphilic beta-cyclodextrins as excipients for the preparation and optimization of nanocapsules without using surface-active agents. Amphiphilic beta-cyclodextrin derivatives were characterized by (1)H-nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, mass spectroscopy, differential scanning calorimetry, and elemental analysis. Nanocapsules prepared by nanoprecipitation were characterized by particle size and zeta potential determination and freeze fracture followed by transmission electron microscopy. The appropriate amphiphilic beta-cyclodextrin and its optimum concentration to be used were determined. Formation and characteristics of the nanocapsules were highly dependent on the structural properties of the modified cyclodextrin, its behavior in the oil-water interface and the viscosity and miscibility of the organic solvent with water. Physical stability after 5-month storage was also evaluated. The results indicated that derivatives with 6C aliphatic chains on the primary face proved to be the most efficient among the amphiphilic beta-CDs in this study. They avoid the use of surfactants in parenteral formulations of nanocapsules.

Capsules↗

PubMed2002

Plasma polymerization of aniline on different surface functionalized substrates.

The plasma polymerization of aniline on different surface functionlized low-density polyethylene (LDPE) substrates was investigated, and the resulting polymer was characterized by X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscopy, and atomic force microscopy. The results showed that the structure of plasma-polymerized polyaniline was rather different from polyaniline synthesized by conventional chemical and electrochemical methods. This difference may be due to extensive coupling reactions and cross-linking reactions during the plasma polymerization process. The use of acrylic acid graft copolymerized LDPE substrate significantly enhanced the adhesion of the polyaniline to the substrate over that observed with pristine LDPE. The plasma polymerized polyaniline can be rendered electrically conductive if the polymerization is carried out on a polystyrenesulfonic acid-coated LDPE substrate. Conductivity can also be induced by acid protonation of the polyaniline by HClO(4). The reaction of the plasma-polymerized polyaniline with viologen grafted on the substrate under UV irradiation and with AuCl(3) and Pd(NO(3))(2) in acid solutions was also investigated.

Journal Article↗

PubMed2005

Order and disorder in alkyl stationary phases.

Covalently modified surfaces represent a unique state of matter that is not well described by liquid or solid phase models. The chemical bond in tethered alkanes imparts order to the surface in the form of anisotropic properties that are evident in chromatographic and spectroscopic studies. An understanding of the structure, conformation, and organization of alkyl-modified surfaces is requisite to the design of improved materials and the optimal utilization of existing materials. In recent years, the study of alkyl-modified surfaces has benefited from advances in modern analytical instrumentation. Aspects of alkyl chain conformation and motion have been investigated through the use of nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, fluorescence spectroscopy, and neutron scattering studies. Chromatography provides complementary evidence of alkyl chain organization through interactions with solute probes. Computational simulations offer insights into the structure of covalently modified surfaces that may not be apparent through empirical observation. This manuscript reviews progress achieved in the study of the architecture of alkyl-modified surfaces.

Journal Article↗