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Results for “Spectroscopy, Fourier Transform Infrared”

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PubMed1993

Identity of the axial ligand of the high-spin heme in cytochrome oxidase: spectroscopic characterization of mutants in the bo-type oxidase of Escherichia coli and the aa3-type oxidase of Rhodobacter sphaeroides.

Prokaryotic and eukaryotic cytochrome c oxidases and several bacterial ubiquinol oxidases compose a superfamily of heme-copper oxidases. These enzymes are terminal components of aerobic respiratory chains, the principal energy-generating systems of aerobic organisms. Two such heme-copper oxidases are the aa3-type cytochrome c oxidase of Rhodobacter sphaeroides and the bo-type ubiquinol oxidase of Escherichia coli. These enzymes catalyze the reduction of oxygen to water at a heme-copper binuclear center. Energy conservation is accomplished by coupling electron transfer through the metals of the oxidases to proton translocation across the cellular membrane. The Rb. sphaeroides and E. coli enzymes have previously been utilized in site-directed mutagenesis studies which identified two histidines which bind the low-spin heme (heme a), as well as additional histidine residues which are probable ligands for copper (CuB). However, the histidine that binds the heme of the binuclear center (heme a3) could not be unequivocally identified between two residues (His284 and His419). Additional characterization by Fourier transform infrared spectroscopy of the CO-bound forms of the E. coli enzyme in which His284 is replaced by glycine or leucine demonstrates that these mutations cause only subtle changes to CO bound to the heme of the binuclear center. Resonance Raman spectroscopy of the Rb. sphaeroides enzyme in which His284 is replaced by alanine shows that the iron-histidine stretching mode of heme a3 is maintained, in contrast with the loss of this mode in mutants at His419. These results demonstrate that His284 is not the heme a3 ligand.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗

PubMed2004

Unilamellar vesicles as potential capreomycin sulfate carriers: preparation and physicochemical characterization.

The aim of this work was to evaluate unilamellar liposomes as new potential capreomycin sulfate (CS) delivery systems for future pulmonary targeting by aerosol administration. Dipalmitoylphosphatidylcholine, hydrogenated phosphatidylcholine, and distearoylphosphatidylcholine were used for liposome preparation. Peptide-membrane interaction was investigated by differential scanning calorimetry (DSC) and attenuated total internal reflection Fourier-transform infrared spectroscopy (ATIR-FTIR). Peptide entrapment, size, and morphology were evaluated by UV spectrophotometry, photocorrelation spectroscopy, and transmission electron microscopy, respectively. Interaction between CS and the outer region of the bilayer was revealed by DSC and ATIR-FTIR. DSPC liposomes showed enhanced interdigitation when the CS molar fraction was increased. Formation of a second phase on the bilayer surface was observed. From kinetic and permeability studies, CS loaded DSPC liposomes resulted more stable if compared to DPPC and HPC over the period of time investigated. The amount of entrapped peptide oscillated between 10% and 13%. Vesicles showed a narrow size distribution, from 138 to 166 nm, and a good morphology. These systems, in particular DSPC liposomes, could represent promising carriers for this peptide.

Anti-Bacterial Agents↗

PubMed1996

Improved bonding strength of polyethylene/polymethylmetacrylate bone cement--a preliminary study.

The adhesion of polymethylmetacrylate (PMMA) bone cement and low density polyethylene (LDPE) substrate by means of corona discharge treatment are presented. The surfaces were characterized by water contact angle goniometer, Fourier-transform infrared spectroscopy in the attenuated total reflectance mode (FTIR-ATR), electron spectroscopy for chemical analysis (ESCA), and scanning electron microscopy (SEM) for surface morphology. The bonding strength between bone cement and LDPE with varying intensity of corona treatment was evaluated by a 180 degrees peel test. The water contact angles decreased with increasing treatment intensity from 95.0 +/- 1.8 to around 43.5 degrees. It was observed that the oxygen containing groups as hydroxyl, ether, carboxylic acid, ester, ketone or aldehyde groups were introduced on the LDPE surfaces by corona treatment. The peel strength steeply increased from 0 to 1.75 kgf/cm with increasing the intensity of corona treatment. The improved adhesion of bone cement onto LDPE substrate may be due to only secondary force such as hydrogen bonding between PMMA bone cement and hydrophilized LDPE substrate.

Adhesiveness↗

PubMed2000

Mechanisms of action of rabbit CAP18 on monolayers and liposomes made from endotoxins or phospholipids.

We have investigated the mechanism of action of the cationic antimicrobial protein (18 kDa) CAP18 on liposomes and monolayers made from phospholipids and enterobacterial lipopolysaccharides (LPS). CAP18 intercalates into lipid matrices composed of LPS from sensitive strains, weaker into those made of LPS from a resistant strain (Proteus mirabilis strain R45) or negatively charged phospholipids, but not into those composed of neutral phosphatidylcholine. From the combination of data obtained with fluorescence resonance energy transfer and Fourier-transform infrared spectroscopy and film balance measurements, it can be concluded that structural differences in the LPS determine the depth of intercalation of CAP18 into the respective lipid matrices. Thus, we identified the L-Arap4N linked to the first Kdo of the LPS of P. mirabilis strain R45 to be responsible for the CAP18 resistance of this strain. These data provide insight into CAP18-mediated effects on the integrity of the outer membrane of Gram-negative bacteria and led to an improved model for rabbit CAP18 membrane interaction.

Animals↗

PubMedDate not supplied

An ultrastructural, microanalytical, and spectroscopic study of bone from a transgenic mouse with a COL1.A1 pro-alpha-1 mutation.

A line of transgenic mice have been investigated that expressed moderate levels of an internally deleted human gene for the pro alpha (I) chain of type I procollagen. These mice expressed the gene at approximately 50% that of the endogenous gene. The gene construct was modeled after a sporadic in-frame deletion of the human gene that produced a lethal variant of osteogenesis imperfecta by causing biosynthesis of shortened pro alpha (I) chains. Periera et al. (1993) reported extensive fracturing in these mice with femurs that were shorter in length and bone that had decreased ash weight, mineral, and collagen content. These workers demonstrated an increased brittleness in bone using biomechanical measurements. The functional consequences of these mutant genes were examined in both transgenic and in normal littermate mice to determine if a valid model at the ultrastructural and analytical level had been produced for OI. X-ray microanalysis of bone mineral demonstrated a significantly lower calcium-to-phosphorus (Ca/P) molar ratio in transgenic mouse bone than in normal littermates; this was a feature of human OI bone. Fourier transform infrared spectroscopy confirmed that the mineral present was apatitic in nature despite the lower Ca/P molar ratio. Alizarin red skeletal staining showed the presence of multiple fracture calluses on the ribs and on the long bones of some of the transgenic mice, this was not seen on normal littermates. No light microscopic differences were observed between normal and transgenic mice; however, many ultrastructural correlates with human OI were observed in the transmission electron microscope. Anomalous fibrils associated with type I collagen, and an amorphous calcified material was observed lining the cartilage, extending beyond the lamina limitans in young transgenic mice.

Aging↗

PubMed2005

Functional antibody immobilization on 3-dimensional polymeric surfaces generated by reactive ion etching.

Reactive ion etching (RIE) was used to pattern antibodies onto the surfaces of polymer substrates. A low pressure, inductively coupled oxygen plasma was used to anisotropically etch 25-30 mum deep features into poly(methyl methacrylate) (PMMA), Zeonex, and polycarbonate (PC). Scanning electron microscopy and contact angle measurements show that the resulting surfaces exhibit significant microroughness and enhanced hydrophilicity. Fourier transform infrared spectroscopy suggests that, in addition to enhanced surface area, chemical modifications may contribute to antibody immobilization. Polyclonal antibodies preferentially bind to the etched areas in RIE-patterned PMMA and Zeonex substrates but localize in unetched regions of RIE-patterned PC surfaces. Simple immunoassays were performed to demonstrate a potential application for RIE-modified polymer surfaces. Antibodies specific for the capture of fluorescently labeled cholera toxin, S. aureus enterotoxin B, and B. anthracis protective antigen were immobilized onto etched PMMA surfaces and shown to specifically capture their labeled antigen from solution. This work demonstrates a potentially useful fabrication methodology for constructing antibody microarrays on plastic substrates.

Antibodies↗

PubMed2002

Investigations into the mechanisms used by the C-terminal anchors of Escherichia coli penicillin-binding proteins 4, 5, 6 and 6b for membrane interaction.

Escherichia coli low molecular mass penicillin-binding proteins (PBPs) include PBP4, PBP5, PBP6 and PBP6b. Evidence suggests that these proteins interact with the inner membrane via C-terminal amphiphilic alpha-helices. Nonetheless, the membrane interactive mechanisms utilized by the C-terminal anchors of PBP4 and PBP6b show differences to those utilized by PBP5 and PBP6. Here, hydrophobic moment-based analyses have predicted that, in contrast to the PBP4 and PBP6b C-termini, those of PBP5 and PBP6 are candidates to form oblique orientated alpha-helices. Consistent with these predictions, Fourier transform infrared spectroscopy (FTIR) has shown that peptide homologs of the PBP4 and PBP5 C-terminal regions, P4 and P5, respectively, both possessed the ability to adopt alpha-helical structure in the presence of lipid. However, whereas P4 appeared to show a preference for interaction with the surface regions of dimyristoylglycerophosphoethanolamine and dimyristoylglycerophosphoglycerol membranes, P5 appeared to show deep penetration of both these latter membranes and dimyristoylglycerophosphocholine membranes. Based on these results, we have suggested that in contrast to the membrane anchoring of the PBP4 and PBP6b C-terminal alpha-helices, the PBP5 and PBP6 C-terminal alpha-helices may possess hydrophobicity gradients and penetrate membranes in an oblique orientation.

Amino Acid Sequence↗

PubMed2003

Binding of pediocin PA-1 with anionic lipid induces model membrane destabilization.

To obtain molecular insights into the action mode of antimicrobial activity of pediocin PA-1, the interactions between this bacteriocin and dimyristoylphosphatidylcholine (DMPC) or dimyristoylphosphatidylglycerol (DMPG) model membranes have been investigated in D(2)O at pD 6 by Fourier transform infrared spectroscopy. The interactions were monitored with respect to alteration of the secondary structure of pediocin, as registered by the amide I' band, and phospholipid conformation, as revealed by the methylene nu(s)(CH(2)) and carbonyl nu(C;O) stretching vibrations. The results show that no interaction between pediocin and DMPC occurs. By contrast, pediocin undergoes a structural reorganization in the presence of DMPG. Upon heating, pediocin self-aggregates, which is not observed for this pD in aqueous solution. The gel-to-crystalline phase transition of DMPG shifts to higher temperatures with a concomitant dehydration of the interfacial region. Our results indicate that pediocin is an extrinsic peptide and that its action mechanism may lie in a destabilization of the cell membrane.

Anti-Bacterial Agents↗

PubMed2005

Synthesis and hybridization studies of DNA on functionalized polypropylene surfaces.

Polypropylene (PP) slice was treated with plasma in a mixture of nitrogen and hydrogen (1:2 V/V). Attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS) demonstrated the successful grafting of amino groups. The as-treated slices were successively applied to the in-situ synthesis of oligonucleotides and an average coupling yield of more than 98% was achieved. The hybridization signals were recorded with fluorescent analysis system. The complementary and mismatched sequences were distinguished clearly, and the ratio of fluorescence intensity values (arbitrary units) for perfect match:single base mismatch:two bases mismatch:three bases mismatch is 108.6: 62.9: 22.4: 5.5. The results implied the plasmamodified PP surface was extremely stable, performed well in DNA hybridization assays, and could service as a good substrate for high-density oligonucleotide array synthesis, especially in a multistep molecular stamping method to fabricate DNA microarrays in-situ on a large scale.

DNA Probes↗

PubMed2006

Composition of calcifications in children with juvenile dermatomyositis: association with chronic cutaneous inflammation.

OBJECTIVE: Calcific deposits develop in 20-40% of children with juvenile dermatomyositis (juvenile DM), contributing to disease morbidity and mortality. This study was undertaken to define the structure and composition of these deposits and to characterize their association with chronic inflammation. METHODS: We examined calcific deposits from 5 children with juvenile DM (2 boys and 3 girls). The crystal structure and mineral content of the deposits was analyzed by x-ray diffraction, Fourier transform infrared spectroscopy, and imaging. The protein content of the deposits, following solubilization, was assayed by Western blotting. RESULTS: All 5 children had both a young age at disease onset (mean +/- SD 3.3 +/- 1.9 years) and, despite therapy, persistent cutaneous inflammation (mean +/- SD duration 81.3 +/- 58.7 months). The bone proteins, osteopontin, osteonectin, and bone sialoprotein, were identified in the protein extracts; the only mineral detected was hydroxyapatite, but the tissue was distinct from bone, with an extremely high mineral content and an irregular distribution of mineral. CONCLUSION: These results indicate that chronic cutaneous inflammation may contribute to the formation of hydroxyapatite-containing pathologic calcifications in children with juvenile DM.

Adolescent↗

PubMed1999

Recombinant rat fibroblast growth factor-16: structure and biological activity.

Fibroblast growth factor-16 (FGF-16) is the most recent member of the FGF family to be cloned. Since the biologic activity of rat FGF-16 (rFGF-16) was unknown, and this protein has no apparent signal sequence, we transformed its entire cDNA into Escherichia coli for high-level expression and further characterization of this novel protein. An attempt was made to purify the expressed protein from the supernatant of mechanically lysed cells using sequential cation-exchange chromatography. This resulted in a gradual loss of the protein as precipitate throughout the purification process. In addition to precipitation during purification, sodium dodecyl sulfate polyacrylamide gel electrophoresis revealed that the partially purified materials showed a cluster of protein bands around 20k to 29k. Sequence analysis of the major bands indicated that two N-terminal truncations had occurred, during E. coli fermentation, purification, or both. The largest truncation resulted in the removal of the 34 N-terminal amino acids, including the initiation codon methionine. We cloned d34 rFGF-16, expressed the gene in E. coli, and developed a purification process for this form. Even with this truncated form, precipitation was a problem. We were largely able to overcome this problem, however, by including EDTA throughout the purification process. We have characterized the structure of purified d34 rFGF-16 extensively using circular dichroism, Fourier transform infrared spectroscopy, and sedimentation velocity analysis. These studies revealed that the protein has a distinct tertiary structure, consists primarily of beta-strands, has a weak tendency to self-associate, and is fairly extended. We then performed biologic assays which showed that d34 rFGF-16 induces oligodendrocyte proliferation in vitro, and induces hepatocellular proliferation and increased liver weight in vivo. In summary, FGF-16, a novel FGF family member, has both unique structural and biological properties.

3T3 Cells↗

PubMed1998

Photoactivation of rhodopsin causes an increased hydrogen-deuterium exchange of buried peptide groups.

A key step in visual transduction is the light-induced conformational changes of rhodopsin that lead to binding and activation of the G-protein transducin. In order to explore the nature of these conformational changes, time-resolved Fourier transform infrared spectroscopy was used to measure the kinetics of hydrogen/deuterium exchange in rhodopsin upon photoexcitation. The extent of hydrogen/deuterium exchange of backbone peptide groups can be monitored by measuring the integrated intensity of the amide II and amide II' bands. When rhodopsin films are exposed to D2O in the dark for long periods, the amide II band retains at least 60% of its integrated intensity, reflecting a core of backbone peptide groups that are resistant to H/D exchange. Upon photoactivation, rhodopsin in the presence of D2O exhibits a new phase of H/D exchange which at 10 degrees C consists of fast (time constant approximately 30 min) and slow (approximately 11 h) components. These results indicate that photoactivation causes buried portions of the rhodopsin backbone structure to become more accessible.

Animals↗

PubMed2005

Design principles of chemical penetration enhancers for transdermal drug delivery.

Chemical penetration enhancers (CPEs) are present in a large number of transdermal, dermatological, and cosmetic products to aid dermal absorption of curatives and aesthetics. This wide spectrum of use is based on only a handful of molecules, the majority of which belong to three to four typical chemical functionalities, sporadically introduced as CPEs in the last 50 years. Using >100 CPEs representing several chemical functionalities, we report on the fundamental mechanisms that determine the barrier disruption potential of CPEs and skin safety in their presence. Fourier transform infrared spectroscopy studies revealed that regardless of their chemical make-up, CPEs perturb the skin barrier via extraction or fluidization of lipid bilayers. Irritation response of CPEs, on the other hand, correlated with the denaturation of stratum corneum proteins, making it feasible to use protein conformation changes to map CPE safety in vitro. Most interestingly, the understanding of underlying molecular forces responsible for CPE safety and potency reveals inherent constraints that limit CPE performance. Reengineering this knowledge back into molecular structure, we designed >300 potential CPEs. These molecules were screened in silico and subsequently tested in vitro for molecular delivery. These molecules significantly broaden the repertoire of CPEs that can aid the design of optimized transdermal, dermatological, and cosmetic formulations in the future.

Administration, Cutaneous↗

PubMed2004

A novel crosslinkable polymer as drug-loaded coating for biomedical device.

A novel copolymer has been synthesized by the radical polymerization of poly (ethylene oxide) methacrylate, stearyl methacrylate, hydroxypropyl methacrylate and trimethoxysilylpropyl methacrylate. The polymer was characterized by Fourier transform infrared spectroscopy, proton nuclear magnetic resonance (1H-NMR) spectroscopy and gel permeation chromatography. The crosslinkable coating was prepared by dip-coating 5mg/ml solution in tetrahydrofuran onto glass substrate. A stable crosslinked coating was obtained after curing the coating at 70 degrees C for 9 h. Contact angle results indicated the possible reorganization of the surface amphiphilic molecule which interpreted the excellent biocompatibility revealed by the results of the platelet adhesion and plasma recalcification time. Rhodamine S and Cibacron Blue were used as model drugs to prepare drug-containing coating at the same conditions. Drug-releasing curves indicated that the mechanism of the release is approximately Fickian release.

Blood Coagulation↗

PubMed2003

Remineralization of demineralized albumin-calcium phosphate coatings.

Calcium phosphate and bovine serum albumin were coprecipitated (under physiological conditions of temperature and pH) upon the surfaces of titanium-alloy samples, which thereby became coated with a dense, proteinaceous mineral layer 30-50 microm in thickness. Dissolution of the inorganic phase by treatment with acidic saline yielded a self-supporting protein scaffold, 7-10 microm in thickness. Energy-dispersive X-ray analysis and Fourier-transform infrared spectroscopy confirmed the absence of inorganic components from the demineralized albumin scaffolds. When titanium-alloy samples bearing these demineralized protein scaffolds were immersed in a supersaturated solution of calcium phosphate (again at physiological temperature and pH), they remineralized. These redux albumin-calcium phosphate layers corresponded in thickness to the original coatings. When titanium-alloy discs bearing the demineralized protein scaffolds were implanted ectopically (subcutaneously) in mice, they, too, remineralized. No uniform mineral layer was deposited upon the surfaces of naked titanium-alloy implants. To the best of our knowledge, this is the first demonstration of remineralization within the interstices of a noncollagenous protein scaffold, either in vitro or in vivo.

Alloys↗

PubMed2006

Evaluation of the application of attenuated total reflectance-Fourier transform infrared spectrometry (ATR-FTIR) and chemometrics to the determination of nutritional parameters of yogurt samples.

A critical evaluation of the application of attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) and partial least squares (PLS) to the determination of several nutritional parameters, such as the energetic value and the carbohydrate, protein and calcium contents, in commercially available yogurt samples was carried out. To this end, a highly heterogeneous population of 48 samples covering a wide range of yogurts obtained from the Spanish market was used. After correcting the spectra, hierarchical cluster analysis was performed in order to select a representative calibration set and the corresponding validation sample set. Different PLS models and several spectral windows were tested in order to evaluate their prediction capabilities for the validation set. For all nutritional parameters, with the exception of fat content, the procedure developed here provided good precision; the values obtained complied with the statutory values declared by the US FDA.

Calcium↗

PubMed1996

Preparation, characterization, and in vivo evaluation of an oil suspension of a bovine growth hormone releasing factor analog.

Pharmacia & Upjohn Inc. has discovered a superior bovine growth hormone releasing factor analog, [IIe2,Ser8,28,Ala15,Leu27,Hse30] bGRF (1-30)-NH-ethyl, acetate salt (U-90699F), for enhancement of animal growth. This report delineates the preparation, characterization, and in vivo evaluation of a U-90699F oil suspension. The oil suspension formulation was selected because of its simplicity, inexpensiveness, and ability to produce sustained U-90699F release. 40% U-90699F monomers were incorporated into Miglyol oil with acceptable injectability. Both reversed-phase-high-pressure liquid chromatography (RP-HPLC) and Fourier transform infrared spectroscopy (FTIR) were utilized to evaluate its chemical and structural stability. This suspension formulation demonstrated no significant changes in concentration as determined by RP-HPLC for 10 weeks at both 25 and 39 degrees C. The U-90699F dispersed in oil also showed no signs of structural conversion from alpha-helix to beta-sheet as monitored by FTIR. However, there was an increase in alpha-helix/disordered coil structure after initial drug incorporation. The suspension was subcutaneously administered to Holstein steers. Areas under the serum somatotropin concentration curve were used to determine the duration of action. It was found that the suspension was able to effectively elevate serum somatotropin for at least 14 days.

Animals↗

PubMed2004

Preparation and in vitro bioactivity of zinc containing sol-gel-derived bioglass materials.

Bioactive glass material of the type CaO--P(2)O(5)--SiO(2)--ZnO was obtained by the sol-gel processing method. This material was produced both in powder and in disks form by compression of the powder. The obtained material was characterized by X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and surface electron micrograph (SEM). The bioactivity was examined in vitro with respect to the ability of hydroxyapatite layer to form on the surface as a result of contact with simulated body fluid (SBF). The XRD and FTIR studies were conducted before and after contact of the material with SBF. The gel-derived materials were amorphous as shown by XRD, but were able to crystallize calcium phosphates on their surfaces when exposed to SBF. We also examined the alkaline phosphatase (AP) activity of osteoblasts, using human fetal osteoblastic cells (hFOB 1.19) cultured on the zinc bioglass, and compared it with the polystyrene plates. The bone cells consistently expressed higher AP activity in the zinc bioglass materials compared with the polystyrene plates, which indicates the zinc containing composition stimulates bone cells production of AP.

Bone Substitutes↗