The Experts below are selected from a list of 165 Experts worldwide ranked by ideXlab platform
Dmitri Graifer - One of the best experts on this subject based on the ideXlab platform.
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Influence of systematic error on the shape of the Scatchard Plot of tRNAPhe binding to eukaryotic ribosomes.
Biochemical Journal, 1997Co-Authors: Sergei A. Nekhai, Vladimir E. Beletzkij, Dmitri GraiferAbstract:Scatchard Plots of tRNAPhe binding to poly(U)-programmed human 80 S ribosomes can be curved, either concave upwards or concave downwards, depending on the experimental conditions. The influence of a systematic error on the shape of the Scatchard Plots has been analysed in a model experiment where the binding proceeds at two independent sites. The Scatchard Plot for this binding model has a concave-upwards shape. When the concentration of the ribosomes is kept constant, a small systematic error in tRNA concentration changes this Scatchard Plot markedly to a concave-downwards Plot as though a co-operative interaction occurred. In contrast, when the tRNA concentration exceeds the ribosomal concentration and their concentration ratio is constant, the Scatchard Plot is stable with respect to the systematic error. We suggest the latter type of experiment to be more appropriate. The results also imply a non-co-operative interaction of tRNAPhe with the 80 S ribosome.
Sergei A. Nekhai - One of the best experts on this subject based on the ideXlab platform.
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Influence of systematic error on the shape of the Scatchard Plot of tRNAPhe binding to eukaryotic ribosomes.
Biochemical Journal, 1997Co-Authors: Sergei A. Nekhai, Vladimir E. Beletzkij, Dmitri GraiferAbstract:Scatchard Plots of tRNAPhe binding to poly(U)-programmed human 80 S ribosomes can be curved, either concave upwards or concave downwards, depending on the experimental conditions. The influence of a systematic error on the shape of the Scatchard Plots has been analysed in a model experiment where the binding proceeds at two independent sites. The Scatchard Plot for this binding model has a concave-upwards shape. When the concentration of the ribosomes is kept constant, a small systematic error in tRNA concentration changes this Scatchard Plot markedly to a concave-downwards Plot as though a co-operative interaction occurred. In contrast, when the tRNA concentration exceeds the ribosomal concentration and their concentration ratio is constant, the Scatchard Plot is stable with respect to the systematic error. We suggest the latter type of experiment to be more appropriate. The results also imply a non-co-operative interaction of tRNAPhe with the 80 S ribosome.
Vladimir E. Beletzkij - One of the best experts on this subject based on the ideXlab platform.
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Influence of systematic error on the shape of the Scatchard Plot of tRNAPhe binding to eukaryotic ribosomes.
Biochemical Journal, 1997Co-Authors: Sergei A. Nekhai, Vladimir E. Beletzkij, Dmitri GraiferAbstract:Scatchard Plots of tRNAPhe binding to poly(U)-programmed human 80 S ribosomes can be curved, either concave upwards or concave downwards, depending on the experimental conditions. The influence of a systematic error on the shape of the Scatchard Plots has been analysed in a model experiment where the binding proceeds at two independent sites. The Scatchard Plot for this binding model has a concave-upwards shape. When the concentration of the ribosomes is kept constant, a small systematic error in tRNA concentration changes this Scatchard Plot markedly to a concave-downwards Plot as though a co-operative interaction occurred. In contrast, when the tRNA concentration exceeds the ribosomal concentration and their concentration ratio is constant, the Scatchard Plot is stable with respect to the systematic error. We suggest the latter type of experiment to be more appropriate. The results also imply a non-co-operative interaction of tRNAPhe with the 80 S ribosome.
Byron Goldstein - One of the best experts on this subject based on the ideXlab platform.
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Interpretation of Scatchard Plots for aggregating receptor systems.
Mathematical biosciences, 1992Co-Authors: Carla Wofsy, Byron GoldsteinAbstract:Abstract Aggregation of cell surface receptors, with each other or with other membrane proteins, occurs in a variety of experimental systems. The list of systems where receptor aggregation appears to be important in understanding ligand binding and cellular responses is growing rapidly. In this paper we explore the interpretation of equilibrium binding data for aggregating receptor systems. The Scatchard Plot is a widely used tool for analyzing equilibrium binding data. The shape of the Scatchard Plot is often interpreted in terms of multiple noninteracting receptor populations. Such an analysis does not provide a framework for investigating the role of receptor aggregation and will be misleading if there is a relation between receptor aggregation and ligand binding. We present a general model for the equilibrium binding of a ligand with any number of aggregating receptor populations and derive theoretical expressions for observable Scatchard Plot features. These can be used to test particular models and estimate model parameters. We develop particular models and apply the general results in the cases of six aggregating receptor systems where ligand binding and receptor aggregation are related: cross-linking of monovalent cell surface proteins by monoclonal antibodies, cross-linking of cell surface antibodies by bivalent ligand, antibody-induced co-cross-linking of cell surface antibodies and Fcγ receptors, ligand-enhanced aggregation of identical epidermal growth factor receptors, aggregation of heterologous receptors for interleukin 2 to form a high-affinity receptor, and association of receptors, including those for interleukins 5 and 6, with nonbinding accessory proteins that influence receptor affinity or effector function.
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Evidence for p55-p75 heterodimers in the absence of IL-2 from Scatchard Plot analysis.
International immunology, 1992Co-Authors: Byron Goldstein, David J. Jones, Ioannis G. Kevrekidis, Alan S. PerelsonAbstract:The high affinity receptor for IL-2 is composed of at least two chains, a p55 chain that binds IL-2 with low affinity and a p75 chain that binds with intermediate affinity. Two molecular mechanisms have been proposed for the formation of the high affinity receptor-ligand complex: The affinity conversion model proposes that the high affinity receptor is formed via stepwise binding in which IL-2 first binds to the p55 chain and the resulting complex then associates with the p75 chain to form a high affinity ternary complex. In the performed heterodimer model the p55 and p75 chains form a non-covalently linked high affinity heterodimer in the absence of IL-2. We show that these two models can be distinguished on the basis of equilibrium binding experiments using cell lines expressing different numbers of p55 chains. To make this distinction we develop a general model for the interaction of IL-2 with its various receptors. We than analyze the case in which heterodimers exist in the absence of IL-2 and the case in which no preformed heterodimers exist. For both cases we predict the shape of equilibrium Scatchard Plots. We then show that published IL-2 binding studies are consistent with a model in which a large concentration of preformed heterodimers is present on the cell surface and inconsistent with a model in which preformed heterodimers are absent from the cell surface. The models that we develop should have general applicability to the entire class of receptor systems in which low and intermediate affinity chains interact to constitute a high affinity receptor.
Alan S. Perelson - One of the best experts on this subject based on the ideXlab platform.
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Evidence for p55-p75 heterodimers in the absence of IL-2 from Scatchard Plot analysis.
International immunology, 1992Co-Authors: Byron Goldstein, David J. Jones, Ioannis G. Kevrekidis, Alan S. PerelsonAbstract:The high affinity receptor for IL-2 is composed of at least two chains, a p55 chain that binds IL-2 with low affinity and a p75 chain that binds with intermediate affinity. Two molecular mechanisms have been proposed for the formation of the high affinity receptor-ligand complex: The affinity conversion model proposes that the high affinity receptor is formed via stepwise binding in which IL-2 first binds to the p55 chain and the resulting complex then associates with the p75 chain to form a high affinity ternary complex. In the performed heterodimer model the p55 and p75 chains form a non-covalently linked high affinity heterodimer in the absence of IL-2. We show that these two models can be distinguished on the basis of equilibrium binding experiments using cell lines expressing different numbers of p55 chains. To make this distinction we develop a general model for the interaction of IL-2 with its various receptors. We than analyze the case in which heterodimers exist in the absence of IL-2 and the case in which no preformed heterodimers exist. For both cases we predict the shape of equilibrium Scatchard Plots. We then show that published IL-2 binding studies are consistent with a model in which a large concentration of preformed heterodimers is present on the cell surface and inconsistent with a model in which preformed heterodimers are absent from the cell surface. The models that we develop should have general applicability to the entire class of receptor systems in which low and intermediate affinity chains interact to constitute a high affinity receptor.
