Glycans: bioactive signals decoded by lectins

2008 ◽  
Vol 36 (6) ◽  
pp. 1491-1496 ◽  
Author(s):  
Hans-Joachim Gabius
Keyword(s):  
Growth Regulation ◽  
Lectin Binding ◽  
Code Word ◽  
Model Systems ◽  
Structural Factors ◽  
Sugar Code ◽  
Functional Perspective ◽  
Sugar Signal ◽  
Third Dimension ◽  
Biochemical Signals

The glycan part of cellular glycoconjugates affords a versatile means to build biochemical signals. These oligosaccharides have an exceptional talent in this respect. They surpass any other class of biomolecule in coding capacity within an oligomer (code word). Four structural factors account for this property: the potential for variability of linkage points, anomeric position and ring size as well as the aptitude for branching (first and second dimensions of the sugar code). Specific intermolecular recognition is favoured by abundant potential for hydrogen/co-ordination bonds and for C–H/π-interactions. Fittingly, an array of protein folds has developed in evolution with the ability to select certain glycans from the natural diversity. The thermodynamics of this reaction profits from the occurrence of these ligands in only a few energetically favoured conformers, comparing favourably with highly flexible peptides (third dimension of the sugar code). Sequence, shape and local aspects of glycan presentation (e.g. multivalency) are key factors to regulate the avidity of lectin binding. At the level of cells, distinct glycan determinants, a result of enzymatic synthesis and dynamic remodelling, are being defined as biomarkers. Their presence gains a functional perspective by co-regulation of the cognate lectin as effector, for example in growth regulation. The way to tie sugar signal and lectin together is illustrated herein for two tumour model systems. In this sense, orchestration of glycan and lectin expression is an efficient means, with far-reaching relevance, to exploit the coding potential of oligosaccharides physiologically and medically.

scholarly journals An Attempt to Develop a New Fire-Resistant Hydraulic Fluid Based on Water-in-Oil Microemulsions

1994 ◽  
Vol 2 (2) ◽  
pp. 83-104
Author(s):  
N. Garti ◽  
A. Aserin ◽  
S. Ezrahi
Keyword(s):  
Phase Diagrams ◽  
High Water ◽  
Model Systems ◽  
High Water Content ◽  
Hydraulic Fluid ◽  
Structural Factors ◽  
Scanning Calorimetry ◽  
Hydraulic Fluids ◽  
Nmr Methods ◽  
Water Solubilization

The strategy for the development of microemulsion-based fire-resistant hydraulic fluids has been expounded. Phase diagrams were constructed for mixtures of water, oil, and nonionic surfactants with and without cosurfactants. From these phase diagrams, the boundaries of the monophasic area were outlined. After the major components had thus been determined, several preliminary formulations were developed by incorporating suitable additives into the oleic ingredient of the hydraulic fluid. These carefully chosen additives considerably improve the performance of the hydraulic fluid. The resulting microemulsion-based compositions complied with most of the requirements set for fire-resistant hydraulic fluids. Model systems pertinent to such formulations were utilized in order to investigate structural factors, which induce enhanced water solubilization. The role played by alcohols in this context was elucidated in terms of an empirical equation. Sophisticated scattering and NMR methods have demonstrated the variations in the microstructure of a high water content model system. Sub-zero differential scanning calorimetry (DSC) techniques have revealed the existence of two types of water (free and bound) and determined their relative concentrations.

Macromolecular assemblies of complex polysaccharides with galectin-3 and their synergistic effects on function

2017 ◽  
Vol 474 (22) ◽  
pp. 3849-3868 ◽  
Author(s):  
Tao Zhang ◽  
Michelle C. Miller ◽  
Yi Zheng ◽  
Zhongyu Zhang ◽  
Huiting Xue ◽  
...  
Keyword(s):  
Quantum Coherence ◽  
Synergistic Effects ◽  
Lectin Binding ◽  
Model Systems ◽  
Nmr Studies ◽  
Macromolecular Assemblies ◽  
T Cell Apoptosis ◽  
Large Size ◽  
Kd Values ◽  
Galectin 3

Although pectin-derived polysaccharides can antagonize galectin function in various pathological disorders, the nature of their binding interactions needs to be better defined for developing them as drugs. Moreover, given their relatively large size and complexity, pectin-derived polysaccharides are also useful as model systems to assess inter-polysaccharide and protein–polysaccharide interactions. Here, we investigated interactions between galectin-3 (Gal-3) and pectin-derived polysaccharides: a rhamnogalacturonan (RG) and two homogalacturonans (HGs). BioLayer Interferometry and fluorescence-linked immunosorbent assays indicate that these polysaccharides bind Gal-3 with macroscopic or apparent KD values of 49 nM, 46 µM, and 138 µM, respectively. 15N-1H heteronuclear single quantum coherence (HSQC) NMR studies reveal that these polysaccharides interact primarily with the F-face of the Gal-3 carbohydrate recognition domain. Even though their binding to Gal-3 does not inhibit Gal-3-mediated T-cell apoptosis and only weakly attenuates hemagglutination, their combination in specific proportions increases activity synergistically along with avidity for Gal-3. This suggests that RG and HG polysaccharides act in concert, a proposal supported by polysaccharide particle size measurements and 13C-1H HSQC data. Our model has HG interacting with RG to promote increased avidity of RG for Gal-3, likely by exposing additional lectin-binding sites on the RG. Overall, the present study contributes to our understanding of how complex HG and RG polysaccharides interact with Gal-3.

scholarly journals Membrane glycoproteins of the nerve growth cone: diversity and growth regulation of oligosaccharides.

1986 ◽  
Vol 103 (4) ◽  
pp. 1369-1382 ◽  
Author(s):  
L M Greenberger ◽  
K H Pfenninger
Keyword(s):  
Sialic Acid ◽  
Growth Cone ◽  
Wheat Germ Agglutinin ◽  
Wheat Germ ◽  
Growth Regulation ◽  
Binding Proteins ◽  
Ricinus Communis ◽  
Lectin Binding ◽  
Adult Brain ◽  
Two Dimensional

A subcellular fraction prepared from fetal rat brain and enriched in growth cone membranes is analyzed for its lectin-binding proteins. Growth-associated glycoproteins are identified by comparing the growth cone glycoproteins with those of synaptosomes. Protein was resolved in one- or two-dimensional gels, electroblotted, and blots probed with radioiodinated concanavalin A, wheat germ agglutinin, and Ricinus communis agglutinins I and II. In one-dimensional gels, each lectin recognizes approximately 20 polypeptides (with substantial overlap) most of which migrate diffusely and have relatively high molecular masses (range 30-200 kD). The seven major Coomassie-staining proteins of the membrane fraction (34-52 kD) are not the major lectin-binding proteins. In two-dimensional gels, the lectin-binding proteins are either streaked across the pH gradient or exist as multiple spots, indicating broad charge heterogeneity. Seven wheat germ agglutinin- and Ricinus communis agglutinin II-binding glycoproteins are present in greater abundance in growth cone fractions compared with synaptosomes. Most notably, an acidic, sialic acid-rich protein (27-30 kD, pI 4.0; termed gp27-30) is most abundant at postnatal day 4, but absent from adult brain. The protein's very acidic isoelectric point is due, at least in part, to its high sialic acid content. Growth regulation of specific protein-linked oligosaccharides suggests that they play a special role in growth cone function. In addition, the great diversity of growth cone glycoproteins from whole brain suggests glycoprotein heterogeneity among growth cones from different neuron types.

scholarly journals Between Self-Regulation and Participatory Monitoring: Comparing Digital News Media Accountability Practices in Spain

2020 ◽  
Vol 8 (2) ◽  
pp. 112-123 ◽  
Author(s):  
Pedro-Luis Pérez-Díaz ◽  
Rocío Zamora Medina ◽  
Enrique Arroyas Langa
Keyword(s):  
News Media ◽  
Self Regulation ◽  
Regulatory System ◽  
Online News ◽  
Structural Factors ◽  
The Public ◽  
Staff Members ◽  
Functional Perspective ◽  
Complex Process ◽  
Accountability Practices

In recent years, the accountability practices of digital journalism have gone from constituting an intimate and self-regulatory system of journalistic culture to a complex process that is increasingly external and open to the public (Fengler, Eberwein, Mazzoleni, Porlezza, &amp; Russ-Mohl, 2014; Suárez-Villegas, Rodríguez-Martínez, Mauri-Ríos, &amp; López-Meri, 2017). In this context, values and goals may remain diverse, arguably linked to idiosyncratic elements which often open a gap between traditional and more contemporary newsroom models. Following a qualitative approach, this study examines online media accountability instruments from a functional perspective, dividing its influence in three temporal phases of news production (Heikkilä et al., 2012). In this way, instruments that hold journalists responsible for their work are explored in four leading online news media from Spain: two digital native outlets (<em>Eldiario.es</em> and <em>ElConfidencial.com</em>) and two legacy outlets (<em>ElPais.com</em> and <em>ElMundo.es</em>). In addition to this observation, in-depth interviews are conducted with staff members in charge of audience management to explore the inner routines and protocols that determine the efficacy of such aspirations.<strong> </strong>Our work reveals the preponderant role of instruments focused on the actor and production transparency that the studied media implement to fulfill their responsibility, especially when compared with the weakened self-regulation instruments. The answers of the interviewees stress the difficulties they face in managing participatory forms of accountability and disclose tensions between different strategies, as well as other structural factors that are discussed as essential for the consolidation of these deontological initiatives.

Instrumentation For Quantitative Microscopy

1977 ◽  
Vol 35 ◽  
pp. 206-209
Author(s):  
B. Ralph ◽  
A.R. Jones
Keyword(s):  
Volume Fraction ◽  
Three Dimensional ◽  
Two Dimensional ◽  
Automatic Data ◽  
Phase Volume Fraction ◽  
Statistical Confidence ◽  
Resultant Data ◽  
Automatic Data Collection ◽  
Third Dimension ◽  
Evolution Of Microstructure

In all fields of microscopy there is an increasing interest in the quantification of microstructure. This interest may stem from a desire to establish quality control parameters or may have a more fundamental requirement involving the derivation of parameters which partially or completely define the three dimensional nature of the microstructure. This latter categorey of study may arise from an interest in the evolution of microstructure or from a desire to generate detailed property/microstructure relationships. In the more fundamental studies some convolution of two-dimensional data into the third dimension (stereological analysis) will be necessary.In some cases the two-dimensional data may be acquired relatively easily without recourse to automatic data collection and further, it may prove possible to perform the data reduction and analysis relatively easily. In such cases the only recourse to machines may well be in establishing the statistical confidence of the resultant data. Such relatively straightforward studies tend to result from acquiring data on the whole assemblage of features making up the microstructure. In this field data mode, when parameters such as phase volume fraction, mean size etc. are sought, the main case for resorting to automation is in order to perform repetitive analyses since each analysis is relatively easily performed.

Lectin Binding to Human Breast Tumor Cells

1976 ◽  
Vol 34 ◽  
pp. 34-35
Author(s):  
Robert E. Nordquist ◽  
J. Hill Anglin ◽  
Michael P. Lerner
Keyword(s):  
Carcinoma Cell ◽  
Ricinus Communis ◽  
Lectin Binding ◽  
Low Frequency ◽  
Breast Carcinoma Cell Line ◽  
Human Breast ◽  
Human Breast Tumor ◽  
Duct Carcinoma ◽  
Specific Antigens ◽  
Ricin Agglutinin

A human breast carcinoma cell line (BOT-2) was derived from an infiltrating duct carcinoma (1). These cells were shown to have antigens that selectively bound antibodies from breast cancer patient sera (2). Furthermore, these tumor specific antigens could be removed from the living cells by low frequency sonication and have been partially characterized (3). These proteins have been shown to be around 100,000 MW and contain approximately 6% hexose and hexosamines. However, only the hexosamines appear to be available for lectin binding. This study was designed to use Concanavalin A (Con A) and Ricinus Communis (Ricin) agglutinin for the topagraphical localization of D-mannopyranosyl or glucopyranosyl and D-galactopyranosyl or DN- acetyl glactopyranosyl configurations on BOT-2 cell surfaces.

Lectin Binding Studies on RNA Tumor Virus-Infected Cells

1975 ◽  
Vol 33 ◽  
pp. 326-327
Author(s):  
D. C. Hixson
Keyword(s):  
Binding Sites ◽  
Lectin Binding ◽  
Culture Conditions ◽  
3T3 Cells ◽  
Binding Studies ◽  
Con A ◽  
Microscopic Studies ◽  
Tumor Virus ◽  
Infected Cells ◽  
Cell Culture Conditions

The abilities of plant lectins to preferentially agglutinate malignant cells and to bind to specific monosaccharide or oligosaccharide sequences of glycoproteins and glycolipids make them a new and important biochemical probe for investigating alterations in plasma membrane structure which may result from malignant transformation. Electron and light microscopic studies have demonstrated clustered binding sites on surfaces of SV40-infected or tryp- sinized 3T3 cells when labeled with concanavalin A (con A). No clustering of con A binding sites was observed in normal 3T3 cells. It has been proposed that topological rearrangement of lectin binding sites into clusters enables con A to agglutinate SV40-infected or trypsinized 3T3 cells (1). However, observations by other investigators have not been consistent with this proposal (2) perhaps due to differences in reagents used, cell culture conditions, or labeling techniques. The present work was undertaken to study the lectin binding properties of normal and RNA tumor virus-infected cells and their associated viruses using lectins and ferritin-conjugated lectins of five different specificities.

Nuclear coiled bodies and the nucleolus

1994 ◽  
Vol 52 ◽  
pp. 20-21
Author(s):  
K. Brasch ◽  
J. Williams ◽  
D. Gallo ◽  
T. Lee ◽  
R. L. Ochs
Keyword(s):  
Mouse Liver ◽  
Nuclear Body ◽  
Nuclear Bodies ◽  
Model Systems ◽  
Coiled Body ◽  
Rrna Processing ◽  
Malignant Cells ◽  
Sm Proteins ◽  
Coiled Bodies ◽  
Unique Protein

Though first described in 1903 by Ramon-y-Cajal as silver-staining “accessory bodies” to nucleoli, nuclear bodies were subsequently rediscovered by electron microscopy about 30 years ago. Nuclear bodies are ubiquitous, but seem most abundant in hyperactive and malignant cells. The best studied type of nuclear body is the coiled body (CB), so termed due to characteristic morphology and content of a unique protein, p80-coilin (Fig.1). While no specific functions have as yet been assigned to CBs, they contain spliceosome snRNAs and proteins, and also the nucleolar protein fibrillarin. In addition, there is mounting evidence that CBs arise from or are generated near the nucleolus and then migrate into the nucleoplasm. This suggests that as yet undefined links may exist, between nucleolar pre-rRNA processing events and the spliceosome-associated Sm proteins in CBs.We are examining CB and nucleolar changes in three diverse model systems: (1) estrogen stimulated chick liver, (2) normal and neoplastic cells, and (3) polyploid mouse liver.

Microtubule Dynamics and Organelle Transport in Reticulomyxa

1990 ◽  
Vol 48 (3) ◽  
pp. 194-195
Author(s):  
Yih-Tai Chen ◽  
Ursula Euteneuer ◽  
Ken B. Johnson ◽  
Michael P. Koonce ◽  
Manfred Schliwa
Keyword(s):  
Plasma Membrane ◽  
Light Microscopy ◽  
Cytoplasmic Dynein ◽  
Living Cells ◽  
Microtubule Dynamics ◽  
Model Systems ◽  
Organelle Transport ◽  
Biochemical Characteristics ◽  
Dependent Transport

The application of video techniques to light microscopy and the development of motility assays in reactivated or reconstituted model systems rapidly advanced our understanding of the mechanism of organelle transport and microtubule dynamics in living cells. Two microtubule-based motors have been identified that are good candidates for motors that drive organelle transport: kinesin, a plus end-directed motor, and cytoplasmic dynein, which is minus end-directed. However, the evidence that they do in fact function as organelle motors is still indirect.We are studying microtubule-dependent transport and dynamics in the giant amoeba, Reticulomyxa. This cell extends filamentous strands backed by an extensive array of microtubules along which organelles move bidirectionally at up to 20 μm/sec (Fig. 1). Following removal of the plasma membrane with a mild detergent, organelle transport can be reactivated by the addition of ATP (1). The physiological, pharmacological and biochemical characteristics show the motor to be a cytoplasmic form of dynein (2).

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