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PubMed1992

Cardiomyocytes express albumin binding proteins.

We investigated whether cardiomyocytes express specific albumin binding proteins (ABP) which may function in the dissociation of fatty acids from their non-covalent complexes with albumin. The experiments were performed on rat neonatal cardiomyocytes (freshly isolated and up to 3 days in culture) and on an enriched sarcolemmal fraction isolated from adult rabbit ventricular myocardium. Three types of experiments were conducted: (a) identification of ABP on electroblots of cardiomyocytes and sarcolemmal extracts reacted with [125I]-bovine serum albumin ([125I]Alb); (b) kinetic assays of [125I]Alb interaction with cardiomyocytes (at 37 degrees C), and with a sarcolemmal fraction (at 4 degrees C); (c) affinity isolation of ABP from solubilized radioiodinated sarcolemmal proteins interacted with an albumin-agarose matrix. The investigation showed that: first, two pairs of polypeptides (ABP of M(r) 18 and 31 kDa) in either cardiomyocytes or sarcolemmal fraction reacted on electroblots with [125I]Alb; second, the binding of the latter to cardiomyocytes was saturable and competed by unlabeled albumin: 50 microM albumin reduced by approximately 90% the binding of radiolabeled albumin. The sarcolemmal fraction bound [125I]Alb with a Kd of 3.66 x 10(-7) M. Thirdly, among the sarcolemmal proteins retained by the albumin-agarose matrix (18 and 31 kDa), the most prominent was the lower band (approximately 16 kDa) of the 18 kDa pair of ABP. The observations revealed that albumin interacts with relatively high affinity with specific binding sites on cardiomyocyte sarcolemma. This interaction may be a recognition step for subsequent fatty acid dissociation and translocation.

Albumins↗
PubMed1992

Demonstration of the capacity of nacre to induce bone formation by human osteoblasts maintained in vitro.

Nacre implanted in vivo in bone is osteogenic suggesting that it may possess factor(s) which stimulate bone formation. The present study was undertaken to test the hypothesis that nacre can induce mineralization by human osteoblasts in vitro. Nacre chips were placed on a layer of first passage human osteoblasts. None of the chemical inducers generally required to obtain bone formation in vitro was added to the cultures. Osteoblasts proliferated and were clearly attracted by nacre chips to which they attached. Induction of mineralization appeared preferentially in bundles of osteoblasts surrounding the nacre chips. Three-dimensional nodules were formed by a dense osteoid matrix with cuboidal osteoblasts at the periphery and osteocytic-like cells in the center. These nodules contained foci with features of mineralized structures and bone-like structures, both radiodense to X-ray. Active osteoblasts (e.m.) with abundant rough endoplasmic reticulum, extrusion of collagen fibrils and budding of vesicles were observed. Matrix vesicles induced mineral deposition. Extracellular collagen fibrils appeared cross-banded and electrodense indicating mineralization. These results demonstrate that a complete sequence of bone formation is reproduced when human osteoblasts are cultured in the presence of nacre. This model provides a new approach to study the steps of osteoblastic differentiation and the mechanisms of induction of mineralization.

Animals↗
PubMed2006

Band shapes of the electronic spectra of anisotropic centers in uniaxial crystals recorded in non-polarized light.

The impurity absorption band shape (in UV or visible region) in a uniaxial crystal recorded in non-polarized light has been found to depend on the technique of recording the optical spectrum and the parameters of each component recorded in polarized light. With the optical density increase in the maximum of the impurity absorption band the number of points of inflection can change from two to four. With the impurity concentration increase one can observe the shift of the impurity absorption band maximum. The impurity absorption band calculated as the difference between a total spectrum and host matrix absorption spectrum has one or two maxima.

Absorption↗
PubMed2006

Single site electronic spectroscopy of palladium chlorin in n-octane matrixes at 7K.

The high resolution, single site emission and absorption spectra of palladium chlorin (PdC) in n-octane matrixes at 7K are reported. The emission and Q and Soret band absorption regions were investigated. The vibrational frequencies of the ground and the lowest energy pipi* excited states were determined from luminescence and excitation spectra, respectively. The emission from PdC was entirely phosphorescence. The emission and Qy region spectra of the complex are similar, having intense, narrow origin bands followed by relatively weak but orderly vibrational structure. The Qx region of this metal chlorin does not have a clear origin and exhibits complex vibrational structure which increases in intensity going to higher energy. In the Soret region of PdC there is only a single intense, broad band.

Cold Temperature↗
PubMed1989

Diastrophic dysplasia: evidence against a defect of type II collagen.

A description of an abnormal segment-long-spacing crystallite (SLS) pattern has been reported for type II collagen from patients with diastrophic dysplasia (Stanescu et al., 1982 a), a disorder that is characterized by large collagen fibrils in the cartilage matrix. The abnormal SLS consisted of an altered electron density between bands 42 and 45, which was interpreted as an abnormality in the type II collagen molecule. It was suggested that the type II collagen is abnormal in diastrophic dysplasia. We have examined SLS of type II collagen from two patients with diastrophic dysplasia and found the SLS patterns to be identical with that of control type II SLS in almost all micrographs. In a few micrographs of diastrophic SLS, crystallites exhibiting the pattern reported by Stanescu et al. were seen. However, the abnormally patterned crystallites always consisted of dimers that were overlapped at the COOH ends in such a way that an electron dense band of one crystallite was positioned between bands 42 and 45 of the second crystallite, apparently creating the abnormal pattern. The abnormal SLS pattern seen in these cases of diastrophic dysplasia appears to be the result of overlapping crystallites and may not be the result of an intrinsic abnormality of type II collagen. We have constructed histograms of the collagen fibril diameters in diastrophic cartilage. While they are larger than normal collagen fibrils, this by itself does not indicate an abnormality of type II collagen. We have shown that large fibrils such as these can be obtained from normal type II collagen when the structure of the cartilage is disrupted by extraction with guanidine.(ABSTRACT TRUNCATED AT 250 WORDS)

Bone Diseases, Developmental↗
PubMed1998

Immunological and biochemical evidence for nuclear localization of annexin in peas.

Immunofluorescent localization of annexins using an anti-pea annexin polyclonal antibody (anti-p35) in pea (Pisum sativum) leaf and stem epidermal peels showed staining of the nuclei and the cell periphery. Nuclear staining was also seen in cell teases prepared from pea plumules. The amount of nuclear stain was reduced both by fixation time and by dehydration and organic solvent treatment. Observation with confocal microscopy demonstrated that the anti-p35 stain was diffusely distributed throughout the nuclear structure. Immunoblots of purified nuclei, nuclear envelope matrix, nucleolar, and chromatin fractions showed a cross-reactive protein band of 35 kDa. These data are the first to show annexins localized in plant cell nuclei where they may play a role in nuclear function.

Annexins↗
PubMed2003

Fluorescence characteristics of protonated form of 6-hydroxyquinoline in Nafion film.

Fluorescence characteristics of 6-hydroxyquinoline (6-HQ) have been studied at room temperature in Nafion(R) film by steady state and nano-second time-resolved fluorescence spectroscopy. The fluorescence spectrum exhibits single emission band corresponding to the protonated form of 6-HQ in this matrix. However, the decay fits with two or three exponential functions depending on the emission wavelength monitored. At blue edge of the emission, the decay fits to three-exponential function, whereas at longer wavelengths, the decay fits to bi-exponential function. Two tentative mechanisms have been proposed to explain the experimental data, viz. a closely lying charge transfer state (CT) or an excited state proton transfer (ESPT) process. The photophysical parameters appear to be sensitive to the change in microstructure due to swelling of the membrane by the solvents.

Fluorocarbon Polymers↗
PubMed2000

An interface with a linear quadrupole ion guide for an electrospray-ion trap mass spectrometer system.

A new ion sampling interface for an electrospray ionization 3D ion trap mass spectrometer system is described. The interface uses linear rf quadrupoles as ion guides and ion traps to enhance the performance of the 3D trap. Trapping ions in the linear quadrupoles is demonstrated to improve the duty cycle of the system. Dipolar excitation of ions trapped in a linear quadrupole is used to eject unwanted ions. A resolution of ejection of up to 254 is demonstrated for protonated reserpine ions (m/z 609.3). A composite waveform with a notch in frequency space is used to eject a wide range of matrix ions and to isolate trace analyte ions in a linear quadrupole before ions are injected into the 3D trap. This is useful to overcome space charge problems in the 3D trap caused by excess matrix ions. For trace reserpine in a 500-fold molar excess of poly(propylene glycol) (PPG), it is demonstrated that the resolution and sensitivity of the 3D trap can be increased dramatically with ejection of the excess PPG matrix ions. In comparison to ejection of matrix ions in the 3D trap with a similar broad-band waveform, a 5-fold increase in sensitivity with a 7 times shorter acquisition time was achieved.

Journal Article↗
PubMedDate not supplied

Chemical and biochemical issues related to X-ray crystallography of the ligand-binding domain of estrogen receptor alpha.

Careful attention to technical issues preceded successful crystallography of the ligand-binding domain of estrogen receptor alpha (ERalpha) complexed with CP-336156, a nonsteroidal estrogen agonist/antagonist. An affinity column based on immobilized estradiol was prepared according to the scheme of Greene et al. (Greene, G. L., Nolan, C., Engler, J. P., and Jensen, E. V. (1980) Proc. Natl. Acad. Sci. U.S.A. 77, 5115-5119). It was shown by X-ray crystallography that the major and less polar isomer of the affinity column precursor was 17alpha-((S)-2',3'-epoxyprop-1'-yl)estra-1,3,5(10)-triene-3,17beta-diol. This diastereomer was coupled to Thiopropyl Sepharose, with coupling monitored by observing loss of the phenolic absorption band of estradiol from the reaction supernatant, and gave an affinity matrix containing about 9 micromol of estradiol per milliliter of wet gel. Recombinant ERalpha ligand binding domain was selectively removed from E. coli cell lysate by binding to the column and was partly S-carboxymethylated by treatment with iodoacetic acid while bound to the column as described by previous workers. After being eluted from the column as a complex with drug, the receptor fragment was shown by mass spectrometry to be a mixture of differently modified forms. It was further S-carboxymethylated in solution, after which anion-exchange chromatography was used to isolate protein in which two of the four cysteine residues were S-carboxymethylated. This material, which afforded diffraction-quality crystals, was subjected to digestion with trypsin and peptide mapping analysis by HPLC coupled with mass spectrometry. For this experiment, the two previously unmodified cysteines were alkylated with 4-vinylpyridine to allow definitive identification. It was shown that Cys-417 and Cys-530 were S-carboxymethylated in the crystallized protein, while Cys-381 and Cys-447 remained unmodified. Close attention to such technical issues may be important in structural studies of other nuclear receptors, a very important class of potential drug targets.

Amino Acid Sequence↗
PubMed2004

Uranium complexes formed at hematite surfaces colonized by sulfate-reducing bacteria.

Modeling uranium (U) transport in subsurface environments requires a thorough knowledge of mechanisms likely to restrict its mobility, such as surface complexation, precipitation, and colloid formation. In closed systems, sulfate-reducing bacteria (SRB) such as Desulfovibrio spp. demonstrably affect U immobilization by enzymatic reduction of U(VI) species (primarily the uranyl ion, UO2(2+), and its complexes) to U(IV). However, our understanding of such interactions under chronic U(VI) exposure in dynamic systems is limited. As a first step to understanding such interactions, we performed bioreactor experiments under continuous flow to study the effect of a biofilm of the sulfate-reducing bacterium Desulfovibrio desulfuricans attached to specular hematite (alpha-Fe2O3) surfaces on surface-associated U(VI) complexation, transformation, and mobility. Employing real-time microscopic observation and X-ray photoelectron spectroscopy (XPS), we show that the characteristics of the U(VI) complex(es) formed at the hematite surface are influenced by the composition of the bulk aqueous phase flowing across the surface and bythe presence of surface-associated SRB. The XPS data further suggest higher levels of U associated with hematite surfaces colonized by SRB than with bacteria-free surfaces. Microscopic observations indicate that at least a portion of the U(VI) that accumulates in the presence of the SRB is exterior to the cells, possibly associated with the extracellular biofilm matrix. The U4f7/2 core-region spectrum and U5f2 valence-band spectrum provide preliminary evidence that the SRB-colonized hematite surface accumulates both U(VI) and U(IV) phases, whereas only the U(VI) phase(s) accumulates on uncolonized hematite surfaces. The results suggest that mineral surfaces exposed to a continuously replenished supply of U(VI)-containing aqueous phase will accumulate U phases that may be more representative of those that exist in U-contaminated aquifers than those which accumulate in closed experimental systems. These phases should be considered in models attempting to predict U transport through subsurface environments.

Biological Availability↗
PubMed2006

Simulation protocols for coherent femtosecond vibrational spectra of peptides.

Two algorithms for simulating the response of peptides to sequences of IR pulses are developed and applied to N-methyl acetamide (NMA) and a 17 residue alpha-helical peptide (YKKKH17) in D(2)O. A fluctuating vibrational-exciton Hamiltonian for the amide I mode is constructed from molecular dynamics trajectories. Coupling with the environment is described using a density functional theory electrostatic map. The cumulant expansion of Gaussian fluctuation incorporates motional narrowing due to fast frequency fluctuations and is adequate for NMA and for isotopically labeled bands in large peptides. Real-space truncation of the scattering matrix of the nonlinear exciton equations significantly reduces the computational cost, making it particularly attractive for slow fluctuations in large globular proteins.

Chemistry, Physical↗
PubMed1998

Effects of local administration of osteocalcin on experimental tooth movement.

The purpose of this study was to evaluate the effects of local administration of osteocalcin, a major noncollagenous bone matrix protein, on experimental tooth movement in rats. An orthodontic elastic band was inserted between the upper first and second molars, and the first molar was moved mesially. Purified osteocalcin (0 to 10 micrograms) in 20 microliters of phosphate-buffered saline was injected into the region of the root bifurcation of the first molar daily for 4 days. Tooth movement increased significantly following the injections. Histological studies revealed that the injections markedly stimulated the appearance of osteoclasts on the pressured side of the alveolar bone surface. The results suggest that osteocalcin has an additive effect on the rate of orthodontic tooth movement through the enhancement of osteoclastogenesis on the pressured side.

Alveolar Process↗
PubMed2005

Infrared spectra of NH2NO, NH2NO+, and NNOH+ and of the N2...H2O complex trapped in solid neon.

When a Ne:H2:N2O mixture is co-deposited at 4.3 K with a beam of neon atoms that have been excited in a microwave discharge, NH2NO+ is stabilized in sufficient concentration for detection of five of its vibrational fundamentals. Their assignments are supported by isotopic substitution studies and by the results of unrestricted B3LYP/cc-pVTZ calculations. Electron recombination results in the stabilization of NH2NO, for which the previously reported argon-matrix assignments are confirmed and extended. The OH-stretching fundamental of NNOH+ also is present in the spectrum of the initial sample deposit, but because of proton sharing with the neon matrix is shifted 43.3 cm(-1) from the gas-phase band center. The OD-stretching fundamental of NNOD+ is identified for the first time in the present study. An absorption at 2311.1 cm(-1) is contributed by the NN-stretching vibration of a complex of N2, probably with an ionic species. On prolonged visible and near-ultraviolet irradiation of the deposit, absorptions of the binary N2...H2O complex become increasingly prominent.

Journal Article↗
PubMed1989

Purification of acetyllactosamine-specific tomato lectin by erythroglycan-sepharose affinity chromatography.

Tomato lectin is specific for oligomers of poly-N-acetyllactosamine containing 3 repeating Gal(beta 1-4)GlcNAc (beta 1-3)-disaccharides. As such it is highly useful for purifying oligosaccharides or glycopeptides with poly-N-acetyllactosamine character. We have found the lectin very useful as an affinity reagent for isolating glycoproteins or glycoprotein domains having poly-N-acetyllactosamine glycosylation. Conventional preparation of tomato lectin by ovomucoid-Sepharose affinity chromatography was found to be unsatisfactory due to instability of column and bleeding of ovomucoid into eluents requiring the necessity for additional purification steps following affinity chromatography. We prepared a column of human erythrocyte band 3 carbohydrate glycopeptide (erythroglycan) attached to Sepharose as an affinity matrix. The purification of tomato lectin to homogeneity in one step on this column matrix is described in this report.

Amino Sugars↗
PubMed2004

A putative mechanism for bog patterning.

The surface of bogs commonly shows various spatial vegetation patterning. Typical are "string patterns" consisting of regular densely vegetated bands oriented perpendicular to the slope. Here, we report on regular "maze patterns" on flat ground, consisting of bands densely vegetated by vascular plants in a more sparsely vegetated matrix of nonvascular plant communities. We present a model reproducing these maze and string patterns, describing how nutrient-limited vascular plants are controlled by, and in turn control, both hydrology and solute transport. We propose that the patterns are self-organized and originate from a nutrient accumulation mechanism. In the model, this is caused by the convective transport of nutrients in the groundwater toward areas with higher vascular plant biomass, driven by differences in transpiration rate. In a numerical bifurcation analysis we show how the maze patterns originate from the spatially homogeneous equilibrium and how this is affected by changes in rainfall, nutrient input, and plant properties. Our results confirm earlier model results, showing that redistribution of a limiting resource may lead to fine-scale facilitative and coarse-scale competitive plant interactions in different ecosystems. Self-organization in ecosystems may be a more general phenomenon than previously thought, which can be mechanistically linked to scale-dependent facilitation and competition.

Food↗
PubMed2003

Chondrogenesis of aged human articular cartilage in a scaffold-free bioreactor.

Chondrogenesis of aged human articular chondrocytes was evaluated under controlled in vitro conditions, using a rotating bioreactor vessel. Articular chondrocytes isolated from 10 aged patients (median age, 84 years) were increased in monolayer culture. A single-cell suspension of dedifferentiated chondrocytes was inoculated in a rotating wall vessel, without the use of any scaffold or supporting gel material. After 90 days of cultivation, a three-dimensional cartilage-like tissue was formed, encapsulated by fibrous tissue resembling a perichondrial membrane. Morphological examination revealed differentiated chondrocytes ordered in clusters within a continuous dense cartilaginous matrix demonstrating a strong positive staining with monoclonal antibodies against collagen type II and articular proteoglycan. The surrounding fibrous membrane consisted of fibroblast-like cells, and showed a clear distinction from the cartilaginous areas when stained against collagen type I. Transmission electron microscopy revealed differentiated and highly metabolically active chondrocytes, producing an extracellular matrix consisting of a fine network of randomly distributed cross-banded collagen fibrils. Chondrogenesis of aged human articular chondrocytes can be induced in vitro in a rotating bioreactor vessel using low shear and efficient mass transfer. Moreover, the tissue-engineered constructs may be used for further in vitro studies of differentiation, aging, and regeneration of human articular cartilage.

Aged↗
PubMed2006

Opening up complete photonic bandgaps in three-dimensional photonic crystals consisting of biaxial dielectric spheres.

In this paper, the scattering matrix of sphere with dielectric biaxial anisotropy is obtained exactly within the framework of the extended Mie theory. By incorporating the scattering matrix into the multiple scattering method, we study theoretically the photonic band structure of three dimensional photonic crystals consisting of biaxial dielectric spheres. Our results demonstrate that complete photonic bandgaps can be found in both fcc and sc lattice structures, which are absent in photonic crystals composed of isotropic dielectric spheres. Moreover we have compared our results with those coming from the photonic crystals consisting of the uniaxially birefringent dielectric spheres. It is found that because of the enhancement of the anisotropy, the degeneracy is lifted further, resulting in two neighboring photonic bandgaps, the lower one is complete while the upper one is partial existing only in some special regions of the first Brillouin zone.

Journal Article↗
PubMed2000

Behavior of the cholesteric liquid-crystal fabry-perot cavity in the bragg reflection band

In this Letter, we investigate the behavior of the cholesteric liquid-crystal Fabry-Perot cavity in the spectral range of the Bragg reflection band. We show that in this region the 2x2-Jones-matrix calculation gives a false predication. However, by the use of the 4x4-matrix method, interesting features are revealed in the resonance spectra. The resonance spectra split when lambda approximately &nmacr;P. Our experiments confirm this phenomenon. The experimental results show that the splitting occurs in a steplike fashion. This can be explained by the quantization of the pitch that occurs due to the fixed boundary conditions.

Journal Article↗