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PubMed2005

Density-matrix renormalization group study of pairing when electron-electron and electron-phonon interactions coexist: effect of the electronic band structure.

The density-matrix renormalization group is used to study the pairing when both electron-electron and electron-phonon interactions are strong in the Holstein-Hubbard model at half filling in a region intermediate between the adiabatic (Migdal's) and antiadiabatic limits. We have found (i) the pairing correlation obtained for a one-dimensional system is nearly degenerate with the charge density-wave correlation in a region where the phonon-induced attraction is comparable with the electron-electron repulsion, but (ii) pairing becomes dominant when we destroy the electron-hole symmetry in a trestle lattice. This provides an instance in which pairing can arise, in a lattice-structure dependent manner, from coexisting electron-electron and electron-phonon interactions.

Journal Article↗
PubMed1995

Visualisation of subchondral erosion in rat monoarticular arthritis by magnetic resonance imaging.

High-resolution magnetic resonance imaging (MRI) was used to investigate antigen-induced monoarticular arthritis (AIMA) in the rat. In sagittal, spin-echo images of the knee, characteristic parallel bands, in the order dark-light-dark, were consistently observed 5-8 days after arthritis induction; the bands ran concentric with, and just beneath, the femoral and tibial articular surfaces. Concurrent radiology, histology and MRI (chemical shift-selective imaging and contrast enhancement with magnetisation transfer and gadolinium) established that the phenomenon reflected subchondral erosion, not artefact. The outer hypointense band corresponded to calcified cartilage underlying the articular surface. The central hyperintense band reflected inflammatory matrix displacing normal haematopoietic tissue immediately subchondrally; here, trabecular bone had mostly disappeared, but adjacent articular cartilage, although under attack and lacking proteoglycan, appeared structurally normal. The inner hypointense band reflected deeper, truncated trabeculae within inflammatory matrix, layered with pallisading osteoblast-like cells. This study exemplifies the power of MRI for revealing localised joint pathology non-invasively, and shows that rat AIMA shares many pathological features with arthritis in human beings.

Animals↗
PubMed2006

Effective band gap of Si nanocrystals embedded in SiO2 matrix.

Using a formulation of the Hartree-Fock formalism with the potential morphing method in the effective mass approximation, we calculate the effective band gap of Si nanocrystals embedded in SiO2 matrix without the existence of polysilane, as a function of their diameter in the size range 1-3.5 nm. Our results are in better agreement with the experimental data, in comparison with other existing theoretical data. For diameter smaller than 2 nm our results have the same tendency with the existing theoretical results, e.g., the discrepancy between theory and experiment seems to be essential.

Crystallization↗
PubMed1980

[Fractionation and biosynthesis of rat liver and Zajdela hepatoma nuclear matrix proteins].

A comparative study of the nuclear matrix proteins of rat liver and Zajdela hepatoma cells was performed. The polyacrylamide SDS electrophoretic profile of the hepatoma nuclear matrix proteins differed from those of the liver by the presence of high molecular weight (over 135 KD) bands. Four nuclear matrix fractions were isolated by a subsequent treatment of the preparation with an aqueous solution of EDTA and 0,025 N sodium hydroxide. The bulk of the nuclear matrix proteins of both liver and hepatoma were alkali-soluble. The percentage of the alkali-insoluble residue and of the water-soluble fraction in the Zajdela hepatoma nuclear matrix was 3.5 and 1.7 times that of the liver, respectively. In the course of 60 min incubation of the liver mince or Zajdela hepatoma cells with 14C-Chlorella protein hydrolyzate in vitro the nuclear matrix proteins incorporated by 10-20% more label than did the total nuclear protein, the specific activity of the alkali-insoluble residue being twice higher that of the whole nuclear matrix protein. After 15 min of incubation the label was rather evenly spread along the gel, containing labelled protein bands separated according to their molecular weight. However, after 30 min and especially 60 min of incubation the label markedly prevailed in the high molecular weight proteins.

Animals↗
PubMed1997

Determination of glucose in a biological matrix by multivariate analysis of multiple band-pass-filtered Fourier transform near-infrared interferograms.

A multivariate calibration method is described in which Fourier transform near-infrared interferogram data are used to determine clinically relevant levels of glucose in an aqueous matrix of bovine serum albumin (BSA) and triacetin. BSA and triacetin are used to model the protein and triglycerides in blood, respectively, and are present in levels spanning the normal human physiological range. A full factorial experimental design is constructed for the data collection, with glucose at 10 levels, BSA at 4 levels, and triacetin at 4 levels. Gaussian-shaped band-pass digital filters are applied to the interferogram data to extract frequencies associated with an absorption band of interest. Separate filters of various widths are positioned on the glucose band at 4400 cm-1, the BSA band at 4606 cm-1, and the triacetin band at 4446 cm-1. Each filter is applied to the raw interferogram, producing one, two, or three filtered interferograms, depending on the number of filters used. Segments of these filtered interferograms are used together in a partial least-squares regression analysis to build glucose calibration models. The optimal calibration model is realized by use of separate segments of interferograms filtered with three filters centered on the glucose, BSA, and triacetin bands. Over the physiological range of 1-20 mM glucose, this 17-term model exhibits values of R2, standard error of calibration, and standard error of prediction of 98.85%, 0.631 mM, and 0.677 mM, respectively. These results are comparable to those obtained in a conventional analysis of spectral data. The interferogram-based method operates without the use of a separate background measurement and employs only a short section of the interferogram.

Animals↗
PubMed1988

Mineralization of adult mouse bone marrow in vitro.

Murine adult bone marrow exhibits mineralizing capacity in vitro as is demonstrated by the new in vitro assay we report here. In less than 2 weeks after the onset of the cultures, mineralization is obtained in more than 80% of the marrow cultures. Moreover, morphological studies reveal that during incubation phenotypic changes related to osteogenic differentiation occur at the extracellular matrix as well within cell populations. Well banded collagen is synthesized. Matrix vesicles and needles of hydroxy-apatite crystals are observed via transmission electron microscopy. Osteoblast-like cells are present with membrane-associated alkaline phosphatase activity. The mineralization is specific for cultured bone marrow and is not observed in cultured spleen fragments as is shown via 85Sr uptake, calcein uptake and histomorphology. No inducing agent is added to the tissue culture medium except for 10% fetal calf serum, beta-glycerophosphate (10(-2) M) and ascorbic acid. However, the prerequisite for obtaining mineralization is the three-dimensional structure of the marrow in culture. The in vitro organ culture we developed may provide the opportunity to identify which marrow cells have osteogenic potential and to investigate the mechanisms triggering differentiation towards osteogenesis.

Animals↗
PubMed1985

Affinity of hemoglobin for the cytoplasmic fragment of human erythrocyte membrane band 3. Equilibrium measurements at physiological pH using matrix-bound proteins: the effects of ionic strength, deoxygenation and of 2,3-diphosphoglycerate.

The cytoplasmic fragment of band 3 protein isolated from the human erythrocyte membrane was linked to a CNBr-activated Sepharose matrix in an attempt to measure, in batch experiments, its equilibrium binding constant with oxy- and deoxyhemoglobin at physiological pH and ionic strength values and in the presence or the absence of 2,3-diphosphoglycerate. All the experiments were done at pH 7.2, and equilibrium constants were computed on the basis of one hemoglobin tetramer bound per monomer of fragment. In 10 mM-phosphate buffer, a dissociation constant KD = 2 X 10(-4)M was measured for oxyhemoglobin and was shown to increase to 8 X 10(-4)M in the presence of 50 mM-NaCl. Association could not be demonstrated at higher salt concentrations. Diphosphoglycerate-stripped deoxyhemoglobin was shown to associate more strongly with the cytoplasmic fragment of band 3. In 10 mM-bis-Tris (pH 7.2) and in the presence of 120 mM-NaCl, a dissociation constant KD = 4 X 10(-4)M was measured. Upon addition of increasing amounts of 2,3-diphosphoglycerate, the complex formed between deoxyhemoglobin and the cytoplasmic fragment of band 3 was dissociated. On the reasonable assumption that the hemoglobin binding site present on band 3 fragment was not modified upon linking the protein to the Sepharose matrix, the results indicated that diphosphoglycerate-stripped deoxyhemoglobin or partially liganded hemoglobin tetramers in the T state could bind band 3 inside the intact human red blood cell.

2,3-Diphosphoglycerate↗
PubMed2002

Ultrastructural localization of type VI collagen in normal adult and osteoarthritic human articular cartilage.

OBJECTIVE: Type VI collagen is a major component of the pericellular matrix compartment in articular cartilage and shows severe alterations in osteoarthritic cartilage degeneration. In this study, we analysed the exact localization of type VI collagen in its relationship to the chondrocyte and the (inter)territorial cartilage matrix. Additionally, we were interested in its ultrastructural appearance in normal and osteoarthritic cartilage. DESIGN: Distribution and molecular appearance was investigated by conventional immunostaining, by multilabeling confocal scanning microscopy, conventional transmission, and immunoelectron microscopy. RESULTS: Our analysis confirmed the pericellular concentration of type VI collagen in normal and degenerated cartilage. Type VI collagen formed an interface in between the cell surface and the type II collagen network. The type VI collagen and the type II collagen networks appeared to have a slight physical overlap in both normal and diseased cartilage. Additionally, some epitope staining was observed in the cell-associated interterritorial cartilage matrix, which did not appear to have an immediate relation to the type II collagen fibrillar network as evaluated by immunoelectron microscopy. In osteoarthritic cartilage, significant differences were found compared with normal articular cartilage: the overall dimension of the lacunar volume increased, and a significantly increased type VI collagen epitope staining was observed in the interterritorial cartilage matrix. Also, the banded isoform of type VI collagen was found around many chondrocytes. CONCLUSIONS: Our study confirms the close association of type VI collagen with both, the chondrocyte cell surface and the territorial cartilage matrix. They show severe alterations in type VI collagen distribution and appearance in osteoarthritic cartilage. Our immunohistochemical and ultrastructural data are compatible with two ways of degradation of type VI collagen in osteoarthritic cartilage: (1) the pathologically increased physiological molecular degradation leading to the complete loss of type VI collagen filaments from the pericellular chondrocyte matrix and (2) the transformation of the fine filaments to the band-like form of type VI collagen. Both might implicate a significant loss of function of the pericellular microenvironment in osteoarthritic cartilage.

Adult↗
PubMed2006

Infrared absorption spectra of matrix-isolated cis, cis-HOONO and its ab initio CCSD(T) anharmonic vibrational bands.

The infrared absorption spectra of matrix-isolated cis, cis-peroxynitrous acid (HOONO and DOONO) in argon have been observed. Six of the nine fundamental vibrational modes for cis, cis-HOONO have been assigned definitively, and one tentatively. Coupled-cluster, ab initio anharmonic force field calculations were used to help guide some of the assignments. The experimental matrix frequencies (cm(-1)) for cis, cis-HOONO are (a' modes) nu1 = 3303+/-1, nu2 = 1600.6+/-0.6, nu3 = 1392+/-1, nu4 = 922.8+/-0.5, nu5 = 789.7+/-0.4, nu6 = 617+/-1; and (a" mode) nu8 = 462+/-1. The fundamentals for the deuterated isotopomer, cis, cis-DOONO, are (a' modes) nu1 = 2447.2+/-0.6, nu2 = 1595.7+/-0.7, nu3 = 1089.1+/-0.4, nu4 = 888.1+/-0.4, nu5 = 786.6+/-0.5, nu6 = 613.9+/-0.9; and (a" mode) nu8 = 456.5+/-0.5.

Journal Article↗
PubMed1978

Improved technique for developing creatine kinase isoenzyme bands by using a substrate in gelatin matrix.

We describe a simple technique for reacting CK isoenzymes with a substrate in gelatin to make them visible after they have been separated by cellulose acetate electrophoresis. The electrophoresed strip requires only 5 min of contact with the substrate in gelatin and about 12 min of drying in an oven at 55 degrees C. The developed isoenzyme bands are discrete, intense, and rectangular in shape. The technique has a sensitivity of 2 to 5 U/liter, and results for isoenzyme MB can be reported about 30 min from the time a specimen is received.

Creatine Kinase↗
PubMed1981

Localization of protein kinase activity and phosphoproteins in mitoplasts from rat liver.

Rat liver mitoplasts (inner mitochondrial membrane and matrix) contain protein kinase activity. This activity increases twofold on addition of Triton X-100. The activity observed in absence of Triton X-100 is probably exposed on the outer surface of mitoplasts, since it is sensitive to trypsin treatment. Most of the remaining protein kinase is bound to the membrane fraction, presumably on the inside of (or else hidden in) the inner mitochondrial membrane. Only a small part of the kinase activity is found in the mitochondrial matrix. A phosphoprotein band, partly resolved into a doublet, was observed on electrophoresis in SDS-polyacrylamide gels after endogeneous phosphorylation of mitoplasts, inner mitochondrial membrane or matrix. When isolated fractions are phosphorylated approximately 75% of the phosphoprotein is found in the matrix, and the remainder in the inner membrane. The phosphorylation of the doublet is inhibited by inhibitors to pyruvate dehydrogenase kinase, suggesting that it represents the phosphorylated subunit of pyruvate dehydrogenase.

Animals↗
PubMed1981

Comparison of cartilage structural glycoproteins with matrix proteins and fibronectin.

After extraction of proteoglycans and soluble matrix proteins from canine puppy rib cartilage, with 4 M guanidine . HCl, the insoluble collagen-containing residue has been shown to contain two collagenase-resistant structural glycoproteins, A and G. The characteristic subunits of these insoluble structural glycoproteins have been identified by solubilizing them with 50 mM dithiothreitol (DTT) in 1% sodium dodecyl sulfate (SDS) and 8 M urea and comparing the SDS disc gel patterns with those of more readily soluble matrix proteins. Three subunit bands which did not occur in gels from the soluble matrix proteins were found in the solubilized material from both the collagen-containing residue and the structural glycoproteins. One band, of about 87 000 daltons, was found equally in both A and G glycoproteins. The other two bands formed a closely spaced doublet, of about 30 000 and 27 500 daltons, of which the lower band is present in higher concentration in G. Although none of these SDS gel bands corresponds with the 220 000 dalton band produced by pure fibronectin under the same conditions, a fraction of the solubilized glycoprotein material resembles fibronectin in showing an affinity for collagen, fibrinogen, heparin, and an antibody to plasma fibronectin. Crude fibronectin from human plasma contains minor components (including one of about 87 000 daltons) which show partial identify in immunodiffusion reactions with components of the solubilized cartilage structural glycoproteins. Solubilized A gave a stronger reaction with anti-plasma fibronectin than did G and the soluble matrix proteins have no reaction. It is possible either that the intercellular structural glycoproteins are formed by selection of some of the partial cleavage products of fibronectin which occur in connective tissues as well as in plasma, or that cleavage products of tissue structural glycoproteins occur in plasma which cross-react with anti-plasma fibronectin.

Animals↗
PubMed1996

Structure-function correlations in the human medial rectus extraocular muscle pulleys.

PURPOSE: Fibroelastic pulleys function like the trochlea to fix the position and pulling direction of the recti extraocular muscles within the orbit. This study characterized the fine structure of the human medial rectus muscle pulley. METHODS: Human medial rectus muscle pulley tissue was dissected at autopsy, immersed in aldehyde fixative solution, and processed for and examined with light and electron microscopy. RESULTS: Pulley structure were located within posterior Tenon's fascia, closely surrounding the medial rectus muscle. Pulleys were comprised of a dense collagen matrix with alternating bands of collagen fibers precisely arranged at right angles to one another. This three-dimensional organization most likely confers high tensile strength to the pulley. Elastin fibrils were interspersed in the collagen matrix. Fibroblasts and mast cells were scattered throughout the relatively acellular and avascular collagen latticework. Connective tissue and smooth muscle bundles suspended the pulley from the periorbita. Smooth muscle was distributed in small, discrete bundles attached deeply into the dense pulley tissue. CONCLUSIONS: Fine structural observations confirm the existence and substantial structure of a pulley system in association with the medial rectus extraocular muscle. The presence of pulleys must be considered in models of the oculomotor plant. The cytoarchitecture and placement of pulleys suggest that they are internally rigid structures and are consistent with the idea that they determine functional origins for the extraocular muscles. However, the nature of the connective tissue-smooth muscle struts suspending the pulley system to the orbit supports the notion that the pulley position, and thus the vector force of the eye muscles, may be adjustable.

Biomechanical Phenomena↗
PubMedDate not supplied

Electron microscopical study in multiple epiphyseal dysplasia type II.

An electron microscopic examination of articular cartilage of two cases with multiple epiphyseal dysplasia type II was performed. The cartilage had a normal cell distribution and no signs of gross degeneration were found. Chondrocytes showed normal ultrastructural characteristics without dilation of the rough endoplasmic reticulum. The matrix contained normal banded collagen fibrils, proteoglycans, and aggregated fibrils.

Adolescent↗
PubMed2004

Matrix-assisted laser desorption/ionization-time of flight-mass spectrometry of lipopolysaccharide species separated by slab-polyacrylamide gel electrophoresis: high-resolution separation and molecular weight determination of lipooligosaccharides from Vibrio fischeri strain HMK.

We recently demonstrated that the combined use of lipopolysaccharide (LPS) reverse staining and high-efficiency passive elution techniques can be successfully used as a suitable interface between LPS slab-gel separation and electrospray ionization-mass spectrometry (ESI-MS) of LPS-derived oligosaccharides. Here, we extend our micropurification strategy for the analysis of O-deacylated LPS forms from Vibrio fischeri HMK after recovery from single reverse-stained LPS bands using matrix-assisted laser desorption/ionization-time of flight-mass spectrometry (MALDI-TOF-MS). The quantities (30-40 microg) obtained from the two gel-resolved LPS bands were sufficient to allow MALDI-TOF-MS detection of O-deacylated LPS glycoforms at m/z 3767.1, 3890.1 for the high-molecular-weight or at m/z 2522.5, 2645.4, 2725.7, and 2848.7 for the low-molecular-weight LPS band. These LPS band heterogeneities resulted not only from variations in the oligosaccharide region of the LPS but also from two phosphorylation states of the lipid A (diphosphoryl and diphosphoryl plus a single phosphoethanolamine substitution). On the other hand, MALDI-TOF mass spectra of the separated LPS bands displayed reduced heterogeneity and increased signal-to-noise ratios as compared to spectra of the unpurified LPS. Furthermore, micropurification of LPS bands prior MALDI-TOF-MS led to a higher sensitivity of detection of less abundant low-molecular-weight LPS glycoforms. Taken together, this and our previous study on gel-micropurified LPS using ESI definitively show how one can unambiguously determine the different molecular species contained within each gel-separated LPS band, their relative abundance and oligosaccharide sequences.

Aliivibrio fischeri↗
PubMed1984

The secretory contents of Paramecium tetraurelia trichocysts: ultrastructural--cytochemical characterization.

The secretory contents ("matrix") of Paramecium tetraurelia trichocysts expand by a factor of 4.5 when they undergo a Ca2+-mediated decondensation in the course of exocytosis. This is paralleled by a concomitant increase in the interval of the periodic banding of the matrix from 12 nm to 45-51 nm, which becomes visible with different electron stains for proteins and negatively charged groups. Recent reports of actin in secretory contents led us to investigate its redistribution and artifactual adsorption to the trichocyst contents upon their expansion. To visualize this effect we used peroxidase-labeled F(ab) fragments from an IgG directed against Paramecium actin, a DNAase I-gold complex, and the induction of F-actin polymerization. The trichocysts were analyzed in situ as well as after isolation by density-gradient centrifugation. Additionally, in response to current reports in the literature, we reanalyzed trichocyst contents for any possible presence of calmodulin. We applied three independent in situ methods for this: autofluorescence after trifluoperazine affinity labeling, calmodulin-fluorescence affinity labeling, and an electron microscopic immunocytochemical method. All three methods failed to reveal any significant labeling of structurally intact trichocysts in situ, although we also showed that discharged trichocysts avidly adsorb calmodulin from the culture medium. From the present data we conclude that the decondensation of trichocysts during exocytosis is mediated by a sudden conformational rearrangement of secretory proteins in the trichocyst contents, without the involvement of any other regulatory or contractile proteins, which occur only in the cytoplasm. Trichocyst contents are not significantly--if at all--glycosylated.

Actins↗
PubMed2003

Macromolecular specificity of collagen fibrillogenesis: fibrils of collagens I and XI contain a heterotypic alloyed core and a collagen I sheath.

Suprastructures of the extracellular matrix, such as banded collagen fibrils, microfibrils, filaments, or networks, are composites comprising more than one type of macromolecule. The suprastructural diversity reflects tissue-specific requirements and is achieved by formation of macromolecular composites that often share their main molecular components alloyed with minor components. Both, the mechanisms of formation and the final macromolecular organizations depend on the identity of the components and their quantitative contribution. Collagen I is the predominant matrix constituent in many tissues and aggregates with other collagens and/or fibril-associated macromolecules into distinct types of banded fibrils. Here, we studied co-assembly of collagens I and XI, which co-exist in fibrils of several normal and pathologically altered tissues, including fibrous cartilage and bone, or osteoarthritic joints. Immediately upon initiation of fibrillogenesis, the proteins co-assembled into alloy-like stubby aggregates that represented efficient nucleation sites for the formation of composite fibrils. Propagation of fibrillogenesis occurred by exclusive accretion of collagen I to yield composite fibrils of highly variable diameters. Therefore, collagen I/XI fibrils strikingly differed from the homogeneous fibrillar alloy generated by collagens II and XI, although the constituent polypeptides of collagens I and II are highly homologous. Thus, the mode of aggregation of collagens into vastly diverse fibrillar composites is finely tuned by subtle differences in molecular structures through formation of macromolecular alloys.

Animals↗
PubMed2000

Theoretical study of the force field and vibrational assignments of thioacetamide and its deuterated analogues.

The harmonic force field of thioacetamide has been obtained by Hartree-Fock level ab initio calculations using the 4-31G(d) basis set. The force constants have been scaled to reproduce the infrared fundamental bands of argon matrix isolated CH3CSNH2 and CD3CSNH2. Normal coordinate calculations based on the scaled force field suggested the co-presence of cis-CH3CSNHD and trans-CH3CSNHD in the infrared spectrum measured for CH3CSND2. The prediction of the fundamental bands was made for CD3CSND2, cis-CD3CSNHD and trans-CD3CSNHD.

Deuterium↗