The Experts below are selected from a list of 267 Experts worldwide ranked by ideXlab platform

Steven M. Cramer - One of the best experts on this subject based on the ideXlab platform.

  • Selective Displacement Chromatography in multimodal cation exchange systems
    Journal of chromatography. A, 2011
    Co-Authors: Rahul D. Sheth, Christopher J. Morrison, Steven M. Cramer
    Abstract:

    A library of displacer analogues with varying degrees of electrostatic, hydrophobic and hydrogen bonding moieties was evaluated for their ability to enhance the selectivity of multimodal (MM) Chromatography under high loading conditions. The library was screened for Displacement of model proteins using a robotic liquid handling system and selective batch separations were achieved for proteins that were inseparable with linear gradient Chromatography. Trends in protein Displacement were identified and displacers with higher hydrophobicity and net charge exhibited improved protein Displacements. Proteins that interacted with the resins primarily via electrostatic interactions were more readily displaced than those that possessed a significant hydrophobic contribution to their binding. In addition, multimodal displacers were found to be more selective than single mode electrostatic displacers. Column Chromatography studies were also carried out and baseline separations were achieved for model protein pairs using selective Displacement. Finally, operation of these columns in the desorption mode resulted in baseline separation of model proteins which were not separable by selective Displacement Chromatography. This study indicates that the inherent selectivity of MM resins can be augmented by the selectivity of the displacer under non-linear competitive binding conditions, creating new opportunities for protein separations not possible using traditional gradient operations.

  • Detection of Trace Proteins in Multicomponent Mixtures Using Displacement Chromatography
    Analytical chemistry, 2011
    Co-Authors: Steven T. Evans, Melissa A. Holstein, Steven M. Cramer
    Abstract:

    Model protein feed mixtures containing three abundant and seven trace proteins at various concentrations were identified and employed in a series of Displacement experiments. Reversed-phase liquid Chromatography (RPLC) and matrix assisted laser desorption ionization-time-of-flight (MALDI-TOF) mass spectrometry were used to evaluate the compositions of both the feed mixtures and effluent fractions from the Displacement experiments. The results demonstrated that trace proteins were focused at the boundaries between the abundant solutes where they were enriched and concentrated. For many of the multicomponent feed mixtures, mass spectrometry analyses of the Displacement column effluent fractions resulted in the identification of trace proteins that were not detectable in the feed. In addition, the use of minimal or no salt in the carrier solutions enabled the analysis of Displacement fractions by direct infusion mass spectrometry. These results are significant in that they indicate that while the presence of abundant proteins can often be problematic for the detection of trace components, Displacement Chromatography may be able to employ these abundant proteins to focus trace proteins in the Displacement train, thus facilitating detection.

  • Synthesis and characterization of fluorescent displacers for online monitoring of Displacement Chromatography.
    Journal of the American Chemical Society, 2008
    Co-Authors: Christopher J. Morrison, Steven M. Cramer, Sun Kyu Park, Chester K. Simocko, Scott A. Mccallum, James A. Moore
    Abstract:

    One of the major impediments to the implementation of Displacement Chromatography for the purification of biomolecules is the need to collect fractions from the column effluent for time-consuming offline analysis. The ability to employ direct online monitoring of Displacement Chromatography would have significant implications for applications ranging from analytical to preparative bioseparations. To this end, a set of novel fluorescent displacers were rationally designed using known chemically selective displacers as a template. Fluorescent cores were functionalized with different charge moieties, creating a homologous library of displacers. These compounds were then tested on two protein pairs, α-chymotrypsinogen A/ribonuclease A and cytochrome c/lysozyme, using batch and column Displacement experiments. Of the synthesized displacers, two were found to be highly selective while one was determined to be a high-affinity displacer. Column Displacements using one of the selective displacers yielded complete ...

  • Displacer concentration effects in Displacement Chromatography: Implications for trace solute detection
    Journal of chromatography. A, 2008
    Co-Authors: Steven T. Evans, Alexander S. Freed, Steven M. Cramer
    Abstract:

    Abstract In this paper, the utility of ion-exchange Displacement Chromatography for the concentration and enrichment of trace proteins is examined. Separations with varying displacer concentrations (1–25 mM neomycin sulfate) indicate that higher concentrations result in elevated protein concentrations, at the price of reduced yields. The results demonstrate that Displacement Chromatography carried out at relatively low displacer concentrations (2.5 mM) can produce significant concentration (8.5-fold) and enrichment (18-fold) of trace proteins present in the feed. Parametric simulations using the steric mass action model are carried out to investigate the concentration effects and enrichment factors observed over a wide range of feed, displacer and buffer counter-ion concentrations, and solute separation factors. The simulations confirm that trace components can be readily concentrated and enriched by Displacement Chromatography and that these effects will be more pronounced as the separation factor between trace and abundant components is increased. The results presented in this paper indicate the potential of Displacement Chromatography for improved separations where trace enrichment is critical such as proteomic applications.

  • 9 Bioseparations by Displacement Chromatography
    Separation Science and Technology, 2007
    Co-Authors: Steven M. Cramer
    Abstract:

    Publisher Summary This chapter summarizes the recent developments in Displacement Chromatography field and to place in perspective the role that Displacement Chromatography could play in preparative bioseparations in the years to come. Displacement Chromatography is an efficient mode of preparative Chromatography. Operationally, Displacement Chromatography is performed in a manner similar to step-gradient Chromatography in which the column is subjected to sequential step changes in the inlet conditions. The Displacement mode of Chromatography takes advantage of the thermodynamic characteristics of the chromatographic system to overcome many of the shortcomings of preparative elution Chromatography. Recent advances in the field have included the advent of low molecular weight displacers, a focus on the design of high-affinity displacer molecules, the extension of Displacement Chromatography to systems other than ion exchange and the application of Displacement Chromatography to several challenging problems from the biotechnology industry.

Georges Guiochon - One of the best experts on this subject based on the ideXlab platform.

  • Shock layer thickness and optimum linear velocity in Displacement Chromatography
    Journal of Chromatography A, 1994
    Co-Authors: Jie Zhu, Georges Guiochon
    Abstract:

    The width of the mixed zones between two successive bands in the isotachic train represents the loss in recovery yield achieved in Displacement Chromatography. Intuitively, this width depends on the mobile phase flow velocity, but no systematic study of this effect has yet been performed. On the other hand, constant pattern behavior and the theory of shock layer are well known in chemical engineering. Using this approach, and assuming competitive Langmuir isotherm behavior, an analytical equation is derived which relates the shock layer thickness (SLT) in Displacement Chromatography and the column design and operating parameters. Using this equation, it is possible to investigate the dependence of the SLT between two consecutive bands in the isotachic train on the mobile phase velocity, the concentration and the retention factor of the displacer and the separation factor of the two components. In Displacement Chromatography, the optimum mobile phase linear velocity (uopts) for minimum shock layer thickness, or maximum recovery yield depends not only on the coefficients of axial dispersion and mass transfer resistance of the two components, as does the optimum mobile phase velocity (uoptL) in linear Chromatography, but also on the retention factor and the concentration of the displacer. The results of the study of this analytical equation are in excellent agreement with those of numerical calculations.

  • Comparison of maximum production rates and optimum operating/design parameters in overloaded elution and Displacement Chromatography.
    Biotechnology and bioengineering, 1993
    Co-Authors: Attila Felinger, Georges Guiochon
    Abstract:

    The results of a study of the optimization of the experimental conditions for maximum production rate in overloaded elution and Displacement Chromatography are discussed. This study is based on the use of the equilibrium-dispersive model of Chromatography and the competitive Langmuir isotherms to calculate individual band profiles in the elution and Displacement modes, and of a simplex algorithm to optimize the production rate. The operating parameters (sample size, mobile phase velocity, and the displacer concentration in the Displacement model) and the column design parameters (column length and average particle diameter) are optimized simultaneously. Binary mixtures having relative concentrations 3:1 and 1:3, and separation factors of 1.2 to 1.8 are investigated. One of our major results is that, in both modes of Chromatography, the maximum production rate is achieved at very low values of the retention factors, k′, much lower than those used in current practice. In all cases, unless k′ exceeds greatly that optimum value, the production rate is higher in overloaded elution than in Displacement Chromatography. This is particularly true for the extraction of a minor component, which is eluted second. © 1993 John Wiley & Sons, Inc.

  • comparison of maximum production rates and optimum operating design parameters in overloaded elution and Displacement Chromatography
    Biotechnology and Bioengineering, 1993
    Co-Authors: Attila Felinger, Georges Guiochon
    Abstract:

    The results of a study of the optimization of the experimental conditions for maximum production rate in overloaded elution and Displacement Chromatography are discussed. This study is based on the use of the equilibrium-dispersive model of Chromatography and the competitive Langmuir isotherms to calculate individual band profiles in the elution and Displacement modes, and of a simplex algorithm to optimize the production rate. The operating parameters (sample size, mobile phase velocity, and the displacer concentration in the Displacement model) and the column design parameters (column length and average particle diameter) are optimized simultaneously. Binary mixtures having relative concentrations 3:1 and 1:3, and separation factors of 1.2 to 1.8 are investigated. One of our major results is that, in both modes of Chromatography, the maximum production rate is achieved at very low values of the retention factors, k′, much lower than those used in current practice. In all cases, unless k′ exceeds greatly that optimum value, the production rate is higher in overloaded elution than in Displacement Chromatography. This is particularly true for the extraction of a minor component, which is eluted second. © 1993 John Wiley & Sons, Inc.

  • Effect of the intersection of the individual isotherms in Displacement Chromatography
    Journal of Chromatography A, 1991
    Co-Authors: Sadroddin Golshan-shirazi, M. Zoubair. El Fallah, Georges Guiochon
    Abstract:

    Abstract Neither the existence of an intersection between the two single-component isotherms drawn on the same graph, nor the fact that the column saturation capacity for the more retained component is lower than that of the lesser retained component, have any major consequence on the chromatographic behavior of elution bands or on the formation of the isotachich train, as long as the equilibrium isotherms of the two components are properly described by the competitive Langmuir model. Significant deviation from this model could make impossible the formation of an isotachic train in Displacement Chromatography, but definitive experimental proof of the existence of this effect is lacking.

C Patrick Mcatee - One of the best experts on this subject based on the ideXlab platform.

  • Current Protocols in Protein Science - Isolation of Monoclonal Antibody Charge Variants by Displacement Chromatography
    Current Protocols in Protein Science, 2012
    Co-Authors: C Patrick Mcatee, Jacob Hornbuckle
    Abstract:

    This unit discusses the important parameters in designing and optimizing a separation of monoclonal antibody (mAb) charge variants from process streams by ion-exchange Displacement Chromatography, including sample preparation and selection of matrix, column, and appropriate buffer. A protocol is provided for determination of optimal column binding and Displacement conditions, including cleaning and regeneration of the Displacement columns. Curr. Protoc. Protein Sci. 69:8.10.1-8.10.13. © 2012 by John Wiley & Sons, Inc. Keywords: Displacement Chromatography; ion-exchange Chromatography; monoclonal antibodies; charge variants; immunogenicity; quality by design

  • Isolation of monoclonal antibody charge variants by Displacement Chromatography.
    Current protocols in protein science, 2012
    Co-Authors: C Patrick Mcatee, Jacob Hornbuckle
    Abstract:

    This unit discusses the important parameters in designing and optimizing a separation of monoclonal antibody (mAb) charge variants from process streams by ion-exchange Displacement Chromatography, including sample preparation and selection of matrix, column, and appropriate buffer. A protocol is provided for determination of optimal column binding and Displacement conditions, including cleaning and regeneration of the Displacement columns.

  • Displacement Chromatography of proteins.
    Current protocols in protein science, 2010
    Co-Authors: C Patrick Mcatee
    Abstract:

    This unit discusses the important parameters in designing and optimizing a separation by ion-exchange Displacement Chromatography, including preparing the sample and choosing a matrix, column, and buffer. Protocols are provided for testing a column, determining binding and elution conditions, displacing the sample, and cleaning, regenerating, and storing of Displacement columns.

  • Current Protocols in Protein Science - Displacement Chromatography of Proteins
    Current Protocols in Protein Science, 2010
    Co-Authors: C Patrick Mcatee
    Abstract:

    This unit discusses the important parameters in designing and optimizing a separation by ion-exchange Displacement Chromatography, including preparing the sample and choosing a matrix, column, and buffer. Protocols are provided for testing a column, determining binding and elution conditions, displacing the sample, and cleaning, regenerating, and storing of Displacement columns. Curr. Protoc. Protein Sci. 59:8.9.1-8.9.14. © 2010 by John Wiley & Sons, Inc. Keywords: Displacement; HPLC; ion-exchange Chromatography

Venkatesh Natarajan - One of the best experts on this subject based on the ideXlab platform.

  • Modeling shock layers in ion‐exchange Displacement Chromatography
    AIChE Journal, 1999
    Co-Authors: Venkatesh Natarajan, Steven M. Cramer
    Abstract:

    In ideal Displacement Chromatography (systems with infinite mass-transfer kinetics), various solutes are separated by sharp discontinuities. In real systems, however, the shocks are eroded into shock layers because of the finite rates of mass transfer. The thickness of these shock layers, which can reduce the yields achievable in these systems, depend on the flow rate, particle diameter and the “difficulty” of these separations. The steric mass action formalism of ion-exchange Chromatography was used in concert with a solid film linear driving force model to describe the effects of flow rate, particle diameter, and the degree of difficulty of the separation on ion-exchange Displacement systems. Simple pulse techniques are employed to estimate the thermodynamic and mass-transfer parameters. The simulations are then compared to experimental results over a range of conditions. The results demonstrate that this relatively simple modeling approach can be employed to describe the behavior of these nonideal Displacement systems.

  • modeling shock layers in ion exchange Displacement Chromatography
    Aiche Journal, 1999
    Co-Authors: Venkatesh Natarajan, Steven M. Cramer
    Abstract:

    In ideal Displacement Chromatography (systems with infinite mass-transfer kinetics), various solutes are separated by sharp discontinuities. In real systems, however, the shocks are eroded into shock layers because of the finite rates of mass transfer. The thickness of these shock layers, which can reduce the yields achievable in these systems, depend on the flow rate, particle diameter and the “difficulty” of these separations. The steric mass action formalism of ion-exchange Chromatography was used in concert with a solid film linear driving force model to describe the effects of flow rate, particle diameter, and the degree of difficulty of the separation on ion-exchange Displacement systems. Simple pulse techniques are employed to estimate the thermodynamic and mass-transfer parameters. The simulations are then compared to experimental results over a range of conditions. The results demonstrate that this relatively simple modeling approach can be employed to describe the behavior of these nonideal Displacement systems.

Jacob Hornbuckle - One of the best experts on this subject based on the ideXlab platform.

  • Isolation of monoclonal antibody charge variants by Displacement Chromatography.
    Current protocols in protein science, 2012
    Co-Authors: C Patrick Mcatee, Jacob Hornbuckle
    Abstract:

    This unit discusses the important parameters in designing and optimizing a separation of monoclonal antibody (mAb) charge variants from process streams by ion-exchange Displacement Chromatography, including sample preparation and selection of matrix, column, and appropriate buffer. A protocol is provided for determination of optimal column binding and Displacement conditions, including cleaning and regeneration of the Displacement columns.

  • Current Protocols in Protein Science - Isolation of Monoclonal Antibody Charge Variants by Displacement Chromatography
    Current Protocols in Protein Science, 2012
    Co-Authors: C Patrick Mcatee, Jacob Hornbuckle
    Abstract:

    This unit discusses the important parameters in designing and optimizing a separation of monoclonal antibody (mAb) charge variants from process streams by ion-exchange Displacement Chromatography, including sample preparation and selection of matrix, column, and appropriate buffer. A protocol is provided for determination of optimal column binding and Displacement conditions, including cleaning and regeneration of the Displacement columns. Curr. Protoc. Protein Sci. 69:8.10.1-8.10.13. © 2012 by John Wiley & Sons, Inc. Keywords: Displacement Chromatography; ion-exchange Chromatography; monoclonal antibodies; charge variants; immunogenicity; quality by design