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Berlin Brandenburg

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  • 1
    Language: English
    In: The Journal of biological chemistry, 28 August 2015, Vol.290(35), pp.21473-85
    Description: Glycoprotein C (gC) mediates the attachment of HSV-1 to susceptible host cells by interacting with glycosaminoglycans (GAGs) on the cell surface. gC contains a mucin-like region located near the GAG-binding site, which may affect the binding activity. Here, we address this issue by studying a HSV-1 mutant lacking the mucin-like domain in gC and the corresponding purified mutant protein (gCΔmuc) in cell culture and GAG-binding assays, respectively. The mutant virus exhibited two functional alterations as compared with native HSV-1 (i.e. decreased sensitivity to GAG-based inhibitors of virus attachment to cells and reduced release of viral particles from the surface of infected cells). Kinetic and equilibrium binding characteristics of purified gC were assessed using surface plasmon resonance-based sensing together with a surface platform consisting of end-on immobilized GAGs. Both native gC and gCΔmuc bound via the expected binding region to chondroitin sulfate and sulfated hyaluronan but not to the non-sulfated hyaluronan, confirming binding specificity. In contrast to native gC, gCΔmuc exhibited a decreased affinity for GAGs and a slower dissociation, indicating that once formed, the gCΔmuc-GAG complex is more stable. It was also found that a larger number of gCΔmuc bound to a single GAG chain, compared with native gC. Taken together, our data suggest that the mucin-like region of HSV-1 gC is involved in the modulation of the GAG-binding activity, a feature of importance both for unrestricted virus entry into the cells and release of newly produced viral particles from infected cells.
    Keywords: Carbohydrate-Binding Protein ; Glycoprotein ; Glycosaminoglycan ; Glycosylation ; Herpesvirus ; Mucin-Like Region ; Surface Plasmon Resonance (SPR) ; Glycosaminoglycans -- Metabolism ; Herpesvirus 1, Human -- Physiology ; Mucins -- Metabolism ; Viral Envelope Proteins -- Chemistry
    E-ISSN: 1083-351X
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  • 2
    In: Social Forces, 2014, Vol.92(4), pp.1513-1544
    Description: Student engagement with school symbolizes efforts toward learning and is one of the strongest predictors of academic success. However, returns to engagement vary across racial and ethnic groups. Scholars have established that human agency is constrained by organizational environments, but they have not adequately assessed whether the advantages associated with engagement and the disadvantages associated with disengagement accrue evenly to groups of students depending on the educational environment. Using ECLS-K data, we examine how one aspect of schools’ organizational culture–Collective Pedagogical Teacher Culture–moderates the relationship between engagement and mathematics achievement for students of different racial/ethnic groups in elementary school. Our study suggests that exhibiting the attributes that are valued in American society, i.e., academic engagement or, more abstractly, a strong ethic toward working academically, is not sufficient for the mathematics achievement of many students—especially minority youth. Students must study in environments that nourish and capitalize upon those attributes so that diverse students can enhance their academic trajectories. Teachers are critical for student learning, and when teachers perceive the presence of Collective Pedagogical Teacher Cultures, returns to student engagement are higher.
    Keywords: Academic Achievement -- United States ; Teacher-Student Relationships -- United States ; Mathematics -- Study And Teaching -- United States
    ISSN: 0037-7732
    E-ISSN: 1534-7605
    Source: Project MUSE
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  • 3
    Language: English
    In: Polymer, 12 October 2016, Vol.102, pp.342-349
    Description: We present a new AFM based methodology to detect specific interactions at cell surfaces. The central idea of this approach is to mimic ligand and receptor mediated physiological adhesion events at cell surfaces. Such adhesion events usually occur between mechanically compliant and hydrated surfaces. Consequently, we synthesized soft, ligand functionalized hydrogel particles and used them as colloidal AFM probes (soft colloidal probes, SCPs). As a proof-of-principle ligand/receptor system we studied the interaction between hyaluronic acid (HA) ligands and CD44 cell receptors. HA/CD44 interactions are involved in manifold signaling processes, in wound healing and tumor progression. Besides a detailed analysis of HA functionalized polyethylene glycol based SCPs, we show that these SCPs selectively bind to cells with CD44 receptors at their surface by means of AFM adhesion measurements. All negative controls showed strongly reduced adhesion forces demonstrating the feasibility of the method. Furthermore we analyzed the time dependence of CD44 and HA adhesion which indicated a rather fast development of the ligand/receptor interaction. Maximum adhesion was reached at about 10 s after contact providing further indication that HA/CD44 interactions can mediate early stages of cell adhesion. Overall this work shows that the specific adhesive interactions of cells can be analyzed close to the biological context by using hydrogel based colloidal AFM probes.
    Keywords: Cell Adhesion ; Adhesion Force ; Peg ; Biomimetic ; Hyaluronan ; Colloidal Probe ; Contact Phenomena ; Engineering ; Chemistry
    ISSN: 0032-3861
    E-ISSN: 1873-2291
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  • 4
    Language: English
    In: Journal of Colloid And Interface Science, 15 January 2013, Vol.390(1), pp.258-266
    Description: ► Two strategies to immobilize chondroitin sulfate to lipid membranes are described. ► The subsequent interaction with the growth factor BMP-2 is monitored. ► The immobilization strategy affected the interaction with BMP-2 significantly. Glycosaminoglycans (GAGs) in the extracellular matrix (ECM) have multiple functions in tissues including providing support, mediating cell division and differentiation, and taking part in important interactions with proteins, e.g. growth factors. Studying GAG related interactions is inherently difficult and requires suitable interaction platforms. We show two strategies to covalently couple the GAG chondroitin sulfate (CS) to supported lipid bilayers (SLBs), either by (a) activating carboxy-functionalized phospholipids in the lipid bilayer, followed by the addition of hydrazide-functionalized CS, or by (b) activating naturally occurring carboxyl groups on CS prior to addition to an amino-functionalized SLB. Bilayer formation and subsequent immobilization was followed in real-time using the Quartz Crystal Microbalance with Dissipation monitoring, a technique that provides unique information when studying highly hydrated molecular films. The two strategies yielded thin CS films (in the nanometer range) with similar viscoelastic properties. Fluidity of the lipid bilayer was retained when CS was coupled. The application of the CS interaction platform was exemplified for type I collagen and the bone inducing growth factor bone morphogenetic protein-2 (BMP-2). The addition of collagen to immoblized CS resulted in soft layers whereas layers formed by addition of BMP-2 were denser, independent on the immobilization strategy used.
    Keywords: Supported Lipid Bilayer ; Chondroitin Sulfate ; Bone Morphogenetic Protein-2 (Bmp-2) ; Quartz Crystal Microbalance With Dissipation Monitoring (Qcm-D) ; Engineering ; Chemistry
    ISSN: 0021-9797
    E-ISSN: 1095-7103
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  • 5
    Language: English
    In: Biomaterials, December 2012, Vol.33(35), pp.8975-8985
    Description: , bone formation is a complex, tightly regulated process, influenced by multiple biochemical and physical factors. To develop a vital bone tissue engineering construct, all of these individual components have to be considered and integrated to gain an -like stimulation of target cells. The purpose of the present studies was to investigate the synergistic role of defined biochemical and physical microenvironments with respect to osteogenic differentiation of human mesenchymal stem cells (MSCs). Biochemical microenvironments have been designed using artificial extracellular matrices (aECMs), containing collagen I (coll) and glycosaminoglycans (GAGs) like chondroitin sulfate (CS), or a high-sulfated hyaluronan derivative (sHya), formulated as coatings on three-dimensional poly(caprolactone- -lactide) (PCL) scaffolds. As part of the physical microenvironment, cells were exposed to pulsed electric fields via transformer-like coupling (TC). Results showed that aECM containing sHya enhanced osteogenic differentiation represented by increases in ALP activity and gene-expression (RT-qPCR) of several bone-related proteins (RUNX-2, ALP, OPN). Electric field stimulation alone did not influence cell proliferation, but osteogenic differentiation was enhanced if osteogenic supplements were provided, showing synergistic effects by the combination of sHya and electric fields. These results will improve the understanding of bone regeneration processes and support the development of effective tissue engineered bone constructs.
    Keywords: Bone Tissue Engineering ; Human Mesenchymal Stem Cells (Mscs) ; Extracellular Matrices (Ecms) ; Glycosaminoglycans (Gags) ; Electrical Stimulation ; Transformer-Like Coupling (TC) ; Medicine ; Engineering
    ISSN: 0142-9612
    E-ISSN: 1878-5905
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  • 6
    Language: English
    In: Biomaterials, 2011, Vol.32(34), pp.8938-8946
    Description: The application of native extracellular matrix (ECM) components is a promising approach for biomaterial design. Here, we investigated artificial ECM (aECM) consisting of collagen I (coll) and the glycosaminoglycans (GAGs) hyaluronan (HA) or chondroitin sulfate (CS). Additionally, GAGs were chemically modified by the introduction of sulfate groups to obtain low-sulfated and high-sulfated GAG derivatives. Sulfate groups are expected to bind and concentrate growth factors and improve their bioactivity. In this study we analyzed the effect of aECM on initial adhesion, proliferation, ECM synthesis and differentiation of human dermal fibroblasts (dFb) within 8–48 h. We show that initial adhesion and cell proliferation of dFb progressively increased in a sulfate dependent manner. In contrast, synthesis of ECM components coll and HA was decreased on high-sulfated aECM coll/HA3.0 and coll/CS3.1. Furthermore, the matrix metallo-proteinase-1 (MMP-1) was down-regulated on coll/HA3.0 and coll/CS3.1 on mRNA and protein level. The fibroblast differentiation marker α-smooth muscle actin (αSMA) is not affected by aECM on mRNA level. Artificial ECM consisting of coll and high-sulfated GAGs proves to be a suitable biomaterial for dFb adhesion and proliferation that induces a “proliferative phenotype” of dFb found in the early stages of cutaneous wound healing.
    Keywords: Wound Healing ; Collagen I ; Sulfated Glycosaminoglycan ; Hyaluronan ; Chondroitin Sulfate ; Human Dermal Fibroblasts ; Medicine ; Engineering
    ISSN: 0142-9612
    E-ISSN: 1878-5905
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  • 7
    Language: English
    In: Biophysical Journal, 19 September 2017, Vol.113(6), pp.1223-1234
    Description: Many viruses, including herpes simplex (HSV), are recruited to their host cells via interaction between their envelope glycoproteins and cell-surface glycosaminoglycans (GAGs). This initial attachment is of a multivalent nature, i.e., it requires the establishment of multiple bonds between amino acids of viral glycoproteins and sulfated saccharides on the GAG chain. To gain understanding of how this binding process is modulated, we performed binding kinetics and mobility studies using end-grafted GAG chains that mimic the end attachment of these chains to proteoglycans. Total internal reflection fluorescence microscopy was used to probe binding and release, as well as the diffusion of single HSV-1 particles. To verify the hypothesis that the degree of sulfation, but also the arrangement of sulfate groups along the GAG chain, plays a key role in HSV binding, we tested two native GAGs (chondroitin sulfate and heparan sulfate) and compared our results to chemically sulfated hyaluronan. HSV-1 recognized all sulfated GAGs, but not the nonsulfated hyaluronan, indicating that binding is specific to the presence of sulfate groups. Furthermore we observed that a notable fraction of GAG-bound virions exhibit lateral mobility, although the multivalent binding to the immobilized GAG brushes ensures firm virus attachment to the interface. Diffusion was faster on the two native GAGs, one of which, chondroitin sulfate, was also characterized by the highest association rate per GAG chain. This highlights the complexity of multivalent virus-GAG interactions and suggests that the spatial arrangement of sulfates along native GAG chains may play a role in modulating the characteristics of the HSV-GAG interaction. Altogether, these results, obtained with a minimal and well-controlled model of the cell membrane, provide, to our knowledge, new insights into the dynamics of the HSV-GAG interaction.
    Keywords: Biology
    ISSN: 0006-3495
    E-ISSN: 1542-0086
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  • 8
    Language: English
    In: Biomacromolecules, 13 March 2017, Vol.18(3), pp.683-694
    Description: Biomimetic hydrogels are advanced biomaterials that have been developed following different synthetic routes. Covalent postfabrication functionalization is a promising strategy to achieve efficient matrix modification decoupled of general material properties. To this end, dual-functional macromers were synthesized by free radical polymerization of maleic anhydride with diacetone acrylamide (N-(1,1-dimethyl-3-oxobutyl)acrylamide) and pentaerythritol diacrylate monostearate. Amphiphilic oligomers (M 40%). Efficient hydrazide/hydrazine immobilization depending on solution pH, hydrogel ketone content as well as ligand concentration for bioconjugation was shown and reversibility of hydrazone formation was indicated by physiologically relevant hydrazide release over 7 days. Proof-of-concept experiments with hydrazido-functionalized hyaluronan demonstrated potential for covalent aECM immobilization. The presented dual-functional macromers have perspective as reactive hydrogel building blocks for various biomedical applications.
    Keywords: Biocompatible Materials -- Chemistry ; Hydrogels -- Chemistry ; Maleic Anhydrides -- Chemistry
    ISSN: 15257797
    E-ISSN: 1526-4602
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  • 9
    Language: English
    In: Biomacromolecules, 11 August 2014, Vol.15(8), pp.3083-92
    Description: Sulfated glycosaminoglycans (GAGs) can direct cellular processes by interacting with proteins of the extracellular matrix (ECM). In this study we characterize the interaction profiles of chemically sulfated hyaluronan (HA) and chondroitin sulfate (CS) derivatives with bone morphogenetic protein-2 (BMP-2) and investigate their relevance for complex formation with the receptor BMPR-IA. These goals were addressed by surface plasmon resonance (SPR) and ELISA in combination with molecular modeling and dynamics simulation. We found not only the interaction of BMP-2 with GAGs to be dependent on the type and sulfation of GAGs but also BMP-2/GAG/BMPR-IA complex formation. The conformational plasticity of the BMP-2 N-termini plays a key role in the structural and thermodynamic characteristics of the BMP-2/GAG/BMPR-IA system. Hence we propose a model that provides direct insights into the importance of the structural and dynamical properties of the BMP-2/BMPR-IA system for its regulation by sulfated GAGs, in which structural asymmetry plays a key role.
    Keywords: Bone Morphogenetic Protein 2 -- Chemistry ; Bone Morphogenetic Protein Receptors, Type I -- Chemistry ; Glycosaminoglycans -- Chemistry
    ISSN: 15257797
    E-ISSN: 1526-4602
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  • 10
    Language: English
    In: Biomaterials, November 2012, Vol.33(33), pp.8418-8429
    Description: To meet the growing need for bone replacement of our aging population, development of new adaptive biomaterials is essential. Collagen and glycosaminoglycans (GAGs) such as hyaluronan (HA) and chondroitin sulfate (CS) are major components of the extracellular matrix (ECM) in bone. We manufactured native and sulfate-modified GAG matrices, evaluated how these components modulate different functions of osteoclasts, the cells that resorb bone, and analyzed the underlying mechanisms. GAGs were tested for their effects on osteoclast adhesion, viability, differentiation, morphology, and resorption as well as proteome alterations using murine RAW264.7 cells and primary human osteoclasts. Native and sulfated GAGs were stable and largely non-cytotoxic. Sulfation of GAGs led to a significant inhibition of osteoclast differentiation and resorption, which was largely dependent on the degree of sulfation of GAGs rather than the monosaccharide composition. Sulfation significantly reduced resorptive function by 14% (CS) and 43% (HA). Highly sulfated GAGs dose-dependently suppressed osteoclast differentiation, osteoclast-specific expression of TRAP, cathepsin K, SWAP-70, and OSCAR by 63–95%, and inhibited proteins involved in cytoskeletal rearrangement. In conclusion, highly sulfated GAGs significantly inhibit various functions of bone-resorbing osteoclasts. Whether these properties locally contribute to improved fracture or bone defect healing needs to be validated .
    Keywords: Extracellular Matrix (Ecm) ; Chondroitin Sulfate ; Hyaluronan ; Osteoclast ; Sulfated Glycosaminoglycans ; Quantitative Proteomics ; Medicine ; Engineering
    ISSN: 0142-9612
    E-ISSN: 1878-5905
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