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Yüce M, Sert F, Torabfam M, Parlar A, Gürel B, Çakır N, Dağlıkoca DE, Khan MA, Çapan Y. Fractionated charge variants of biosimilars: A review of separation methods, structural and functional analysis. Anal Chim Acta 2021; 1152:238189. [PMID: 33648647 DOI: 10.1016/j.aca.2020.12.064] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2020] [Revised: 12/28/2020] [Accepted: 12/29/2020] [Indexed: 12/21/2022]
Abstract
The similarity between originator and biosimilar monoclonal antibody candidates are rigorously assessed based on primary, secondary, tertiary, quaternary structures, and biological functions. Minor differences in such parameters may alter target-binding, potency, efficacy, or half-life of the molecule. The charge heterogeneity analysis is a prerequisite for all biotherapeutics. Monoclonal antibodies are prone to enzymatic or non-enzymatic structural modifications during or after the production processes, leading to the formation of fragments or aggregates, various glycoforms, oxidized, deamidated, and other degraded residues, reduced Fab region binding activity or altered FcR binding activity. Therefore, the charge variant profiles of the monoclonal antibodies must be regularly and thoroughly evaluated. Comparative structural and functional analysis of physically separated or fractioned charged variants of monoclonal antibodies has gained significant attention in the last few years. The fraction-based charge variant analysis has proved very useful for the biosimilar candidates comprising of unexpected charge isoforms. In this report, the key methods for the physical separation of monoclonal antibody charge variants, structural and functional analyses by liquid chromatography-mass spectrometry, and surface plasmon resonance techniques were reviewed.
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Affiliation(s)
- Meral Yüce
- Sabanci University, SUNUM Nanotechnology Research and Application Center, 34956, Istanbul, Turkey.
| | - Fatma Sert
- Sabanci University, Faculty of Engineering and Natural Sciences, 34956, Istanbul, Turkey; ILKO ARGEM Biotechnology R&D Center, 34906, Pendik, Istanbul, Turkey
| | - Milad Torabfam
- Sabanci University, Faculty of Engineering and Natural Sciences, 34956, Istanbul, Turkey
| | - Ayhan Parlar
- Sabanci University, Faculty of Engineering and Natural Sciences, 34956, Istanbul, Turkey
| | - Büşra Gürel
- Sabanci University, SUNUM Nanotechnology Research and Application Center, 34956, Istanbul, Turkey
| | - Nilüfer Çakır
- Sabanci University, Faculty of Engineering and Natural Sciences, 34956, Istanbul, Turkey; ILKO ARGEM Biotechnology R&D Center, 34906, Pendik, Istanbul, Turkey
| | - Duygu E Dağlıkoca
- ILKO ARGEM Biotechnology R&D Center, 34906, Pendik, Istanbul, Turkey
| | - Mansoor A Khan
- Texas A&M Health Sciences Centre, Irma Lerma Rangel College of Pharmacy, TX, 77843, USA
| | - Yılmaz Çapan
- ILKO ARGEM Biotechnology R&D Center, 34906, Pendik, Istanbul, Turkey; Hacettepe University, Faculty of Pharmacy, 06100, Ankara, Turkey.
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2
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He YC, Kong FZ, Fan LY, Wu JY, Liu XP, Li J, Sun Y, Zhang Q, Yang Y, Wu XJ, Xiao H, Cao CX. Preparation of intact mitochondria using free-flow isoelectric focusing with post-pH gradient sample injection for morphological, functional and proteomics studies. Anal Chim Acta 2017; 982:200-208. [DOI: 10.1016/j.aca.2017.06.007] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2016] [Revised: 06/10/2017] [Accepted: 06/13/2017] [Indexed: 12/31/2022]
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3
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Righetti PG. Obituary. Electrophoresis 2013. [DOI: 10.1002/elps.201370044] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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4
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Moritz RL, Skandarajah AR, Ji H, Simpson RJ. Proteomic analysis of colorectal cancer: prefractionation strategies using two-dimensional free-flow electrophoresis. Comp Funct Genomics 2010; 6:236-43. [PMID: 18629191 PMCID: PMC2447484 DOI: 10.1002/cfg.477] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2005] [Revised: 03/16/2005] [Accepted: 03/17/2005] [Indexed: 01/21/2023] Open
Abstract
This review deals with the application of a new prefractionation tool, free-flow
electrophoresis (FFE), for proteomic analysis of colorectal cancer (CRC). CRC is a
leading cause of cancer death in the Western world. Early detection is the single most
important factor influencing outcome of CRC patients. If identified while the disease
is still localized, CRC is treatable. To improve outcomes for CRC patients there
is a pressing need to identify biomarkers for early detection (diagnostic markers),
prognosis (prognostic indicators), tumour responses (predictive markers) and disease
recurrence (monitoring markers). Despite recent advances in the use of genomic
analysis for risk assessment, in the area of biomarker identification genomic methods
alone have yet to produce reliable candidate markers for CRC. For this reason,
attention is being directed towards proteomics as a complementary analytical tool
for biomarker identification. Here we describe a proteomics separation tool, which
uses a combination of continuous FFE, a liquid-based isoelectric focusing technique, in
the first dimension, followed by rapid reversed-phase HPLC (1–6 min/analysis) in the
second dimension. We have optimized imaging software to present the FFE/RP-HPLC
data in a virtual 2D gel-like format. The advantage of this liquid based fractionation
system over traditional gel-based fractionation systems is the ability to fractionate
large quantity protein samples. Unlike 2D gels, the method is applicable to both
high-Mr proteins and small peptides, which are difficult to separate, and in the case
of peptides, are not retained in standard 2D gels.
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Affiliation(s)
- Robert L Moritz
- Joint Proteomics Laboratory Ludwig Institute for Cancer Research (Melbourne Branch), The Walter and Eliza Hall Institute of Medical Research, Royal Melbourne Hospital, Parkville, Victoria 3050, Australia
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Meert CD, Brady LJ, Guo A, Balland A. Characterization of Antibody Charge Heterogeneity Resolved by Preparative Immobilized pH Gradients. Anal Chem 2010; 82:3510-8. [PMID: 20364842 DOI: 10.1021/ac902408r] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Affiliation(s)
- Charlie D. Meert
- Amgen Inc., Analytical and Formulation Sciences, 1201 Amgen Court West, Seattle, Washington 98119
| | - Lowell J. Brady
- Amgen Inc., Analytical and Formulation Sciences, 1201 Amgen Court West, Seattle, Washington 98119
| | - Amy Guo
- Amgen Inc., Analytical and Formulation Sciences, 1201 Amgen Court West, Seattle, Washington 98119
| | - Alain Balland
- Amgen Inc., Analytical and Formulation Sciences, 1201 Amgen Court West, Seattle, Washington 98119
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Varenne A, Descroix S. Recent strategies to improve resolution in capillary electrophoresis—A review. Anal Chim Acta 2008. [DOI: 10.1016/j.aca.2008.08.039] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
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8
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Suratman A, Wätzig H. Long-term precision in capillary isoelectric focusing for protein analysis. J Sep Sci 2008; 31:1834-40. [DOI: 10.1002/jssc.200700678] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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9
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Lalwani S, Tutu E, Vigh G. Isoelectric buffers, part 3: Determination of pKa and pI values of diamino sulfate carrier ampholytes by indirect UV-detection capillary electrophoresis. Electrophoresis 2005; 26:2503-10. [PMID: 15937983 DOI: 10.1002/elps.200500002] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Ampholytes with close pK(a) values (i.e., good carrier ampholytes (CAs)) are needed as buffers in pH-biased isoelectric trapping (IET) separations. The syntheses of two families of such good CAs were reported recently. Members of the family of diamino sulfate ampholytes (first series) had pI values in the 5.7 < pI < 9.0 range. Members of the family of quaternary ammonium dicarboxylic acid ampholytes (second series) had pI values in the pI < 4.3 range. To further characterize the diamino sulfate ampholytes, their effective mobilities were measured by indirect UV-absorbance detection capillary electrophoresis in a series of background electrolytes (BGEs) with different pH values. The pK(a) and limiting ionic mobility values of the CAs were obtained by fitting these mobility values, as a function of the pH and the ionic strength of the BGEs, to the theoretical mobility expression. These diamino sulfates complete the list of CAs suitable for IET separations.
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Affiliation(s)
- Sanjiv Lalwani
- Department of Chemistry, Texas A&M University, College Station, TX 77842-3012, USA
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10
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Lalwani S, Tutu E, Vigh G. Synthesis and characterization of quaternary ammonium dicarboxylic acid isoelectric buffers and their use in pH-biased isoelectric trapping separations. Electrophoresis 2005; 26:2047-55. [PMID: 15818576 DOI: 10.1002/elps.200410363] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Two approaches are described in this paper for the synthesis of isoelectric buffers that have pI values in the 1.5 < pI < 4.3 range. The first synthesis relies on the alkylation of existing aminodicarboxylic acids and recovery of the ampholyte as an inner salt. The second synthesis method forms low-pI ampholytes by reacting a secondary amine with two equivalents of an alkylester of a haloalkanecarboxylic acid, followed by hydrolysis of the intermediate in an alkaline solution and recovery of the ampholyte as an inner salt. The new ampholytes have been analytically characterized by capillary electrophoresis, high-resolution electrospray ionization-mass spectrometry, one- and two-dimensional nuclear magnetic resonance (NMR) spectroscopy, and X-ray crystallography. The isoionic solutions of the new ampholytes have high buffering capacity and conductivity, making them good pH biasers in the receiving stream in preparative-scale pH-biased isoelectric trapping separations.
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Affiliation(s)
- Sanjiv Lalwani
- Department of Chemistry, Texas A&M University, College Station, TX, USA
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11
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Rodemann T, Johns C, Yang WS, Haddad PR, Macka M. Isoelectric Buffers for Capillary Electrophoresis. 2. Bismorpholine Derivative of a Carboxylic Acid as a Low Molecular Weight Isoelectric Buffer. Anal Chem 2004; 77:120-5. [PMID: 15623286 DOI: 10.1021/ac049237u] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A new compound class of synthetic isoelectric buffers is introduced, designed as a small molecule with one fully or prevailingly dissociated acidic group (such as sulfonic or carboxylic) and two partly pronated (buffering) basic amino groups attached onto a hydrophilic UV-transparent backbone. As an example, a new isoelectric compound 2,2-bis(4-morpholinylmethyl)propanoic acid (BMMPA) was synthesized by attaching two morpholine groups onto a molecule of pivalic acid. It was characterized as having an isoelectric point pI = 6.5 and exhibiting satisfactory buffering capacity at the pI. Solutions of BMMPA are transparent down to the low-UV spectral region, thus making it a potentially suitable buffer for a number of separation methods. Its use in capillary electrophoresis was demonstrated in a separation system for indirect photometric detection of anions based on an electrolyte with the anionic dye Orange G as the indirect detection probe and using BMMPA as a buffer. The use of an isoelectric buffering compound brings the advantages of a buffered electrolyte without the concomitant introduction of co-ions that would be detrimental to the indirect detection process. Submicromole per liter limits of detection for a number of inorganic and small organic ions were achieved. Optimal structural properties of the isoelectric buffer with respect to its buffering properties are discussed.
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Affiliation(s)
- Thomas Rodemann
- School of Chemistry, and Australian Centre for Research on Separation Science (ACROSS), School of Chemistry, University of Tasmania, Private Bag 75, Hobart 7001, Tasmania, Australia
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12
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Moritz RL, Ji H, Schütz F, Connolly LM, Kapp EA, Speed TP, Simpson RJ. A Proteome Strategy for Fractionating Proteins and Peptides Using Continuous Free-Flow Electrophoresis Coupled Off-Line to Reversed-Phase High-Performance Liquid Chromatography. Anal Chem 2004; 76:4811-24. [PMID: 15307793 DOI: 10.1021/ac049717l] [Citation(s) in RCA: 99] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Extensive prefractionation is now considered to be a necessary prerequisite for the comprehensive analysis of complex proteomes where the dynamic range of protein abundances can vary from approximately 10(6) for cells to approximately 10(10) for tissues such as blood. Here, we describe a high-resolution 2D protein separation system that uses a continuous free-flow electrophoresis (FFE) device to fractionate complex protein mixtures by solution-phase isoelectric focusing (IEF) into 96 well-defined pools, each separated by approximately 0.02-0.10 pH unit depending on the gradient created, followed by rapid (approximately 6 min per analysis) reversed-phase high-performance liquid chromatography (RP-HPLC) of each FFE pool. Fractionated proteins are readily visualized in a virtual 2D format using software that plots protein loci, pI in the first dimension and relative hydrophobicity (i.e., RP-HPLC retention time) in the second dimension. By coupling a diode-array detector in line with a multiwavelength fluorescence detector, separated proteins can be monitored in the RP-HPLC eluent by both UV absorbance and intrinsic fluorescence simultaneously from a single experiment. Triplicate analyses of standard proteins using a pH 3-10 gradient conducted over a 3-day period revealed a high system reproducibility with a SD of 0.57 (0.05 pH unit) within the FFE pools and 0.003 (0.18 s) for protein retention times in the second-dimension RP-HPLC step. In addition, we demonstrate that the FFE-IEF/RP-HPLC separation strategy can also be applied to complex mixtures of low molecular weight compounds such as peptides. With the facile ability to measure the pH of the isoelectric focused pools, peptide pI values can be estimated and used to qualify peptide identifications made using either MS/MS sequencing approaches or pI discriminated peptide mass fingerprinting. The calculated peak capacity of this 2D liquid-based FFE-IEF/RP-HPLC system is 6720.
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Affiliation(s)
- Robert L Moritz
- Joint ProteomicS Laboratory, Ludwig Institute for Cancer Research, Parkville, 3050, Victoria, Australia
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13
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Ogle D, Ho A, Gibson T, Rylatt D, Shave E, Lim P, Vigh G. Preparative-scale isoelectric trapping separations using a modified Gradiflow unit. J Chromatogr A 2002; 979:155-61. [PMID: 12498244 DOI: 10.1016/s0021-9673(02)01601-1] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The Gradiflow BF200 preparative electrophoretic unit (Gradipore), which has been developed for size-based and charge-sign-based protein separations and in which the hydraulic flow path of the recirculating sample stream in the separation cartridge is orthogonal to the electric field, has been modified to carry out binary protein separations using the principles of isoelectric trapping. The disposable separation cartridge contained three isoelectric membranes which, along with the cartridge holder, formed the anode and cathode compartments and the anodic and cathodic separation compartments. The utility of the modified instrument was demonstrated by effecting a binary separation of chicken egg white across an isoelectric point 5.5 isoelectric membrane. The desalting and subsequent binary separation steps proved to be remarkably rapid, due to the favorable combination of short electrophoretic path, high electric field strength and large effective isoelectric membrane surface area.
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Affiliation(s)
- David Ogle
- Gradipore, French's Forest, NSW 2086, Australia
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14
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Kim SH, Otani R, Shirai W, Shibasaki-Kitakawa N, Kitakawa A, Yonemoto T. Bioseparation Engineering. Mathematical Modeling of Continuous Separation Process of Proteins using Partial Recycling Free-Flow Isoelectric Focusing with Feed Supply and Product Withdrawal. KAGAKU KOGAKU RONBUN 2001. [DOI: 10.1252/kakoronbunshu.27.174] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
| | - Ritsuko Otani
- Department of Chemical Engineering, Tohoku University
| | - Wataru Shirai
- Department of Chemical Engineering, Tohoku University
| | | | - Akio Kitakawa
- Department of Materials Science and Engineering, Miyagi National College of Technology
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15
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Righetti PG, Gelfi C, Bossi A, Olivieri E, Castelletti L, Verzola B, Stoyanov AV. Capillary electrophoresis of peptides and proteins in isoelectric buffers: an update. Electrophoresis 2000; 21:4046-53. [PMID: 11192123 DOI: 10.1002/1522-2683(200012)21:18<4046::aid-elps4046>3.0.co;2-5] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Capillary electrophoresis in acidic, isoelectric buffers is a novel methodology allowing fast protein and peptide analysis in uncoated capillaries. Due to the low pH adopted and to the use of dynamic coating with cellulose derivatives, silanol ionization is essentially suppressed and little interaction of macromolecules with the untreated wall occurs. In addition, due to the low conductivity of quasi-stationary, isoelectric buffers, high-voltage gradients can be applied (up to 800 V/cm) permitting fast peptide analysis with a high resolving power due to minimal diffusional peak spreading. Four such buffers are here described: cysteic acid (Cys-A, pI 1.85), iminodiacetic acid (IDA, pI 2.23), aspartic acid (Asp, pI 2.77) and glutamic acid (Glu, pI 3.22). A number of applications are reported, ranging from food analysis to the study of folding/unfolding transitions of proteins.
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Affiliation(s)
- P G Righetti
- University of Verona, Department of Agricultural & Industrial Biotechnologies, Italy.
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Akahoshi A, Sato K, Nawa Y, Nakamura Y, Ohtsuki K. Novel approach for large-scale, biocompatible, and low-cost fractionation of peptides in proteolytic digest of food protein based on the amphoteric nature of peptides. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2000; 48:1955-1959. [PMID: 10820121 DOI: 10.1021/jf991286y] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
A large-scale, biocompatible, and low-cost procedure for peptide fractionation based on the amphoteric nature of peptide is developed. A sample cell (120 x 100 x 50 mm) with four joint tubes (17 mm i.d. and 20 mm in length) on the front and back was prepared. On the end of the joint tubes, a nylon screen (100 mesh)-supported agarose gel layer was formed. Five or nine of the sample cells were connected. A tryptic digest of casein (2.0-3.6 L) was applied to the sample cells. At each end of the sample cell apparatus, an additional cell filled with 0.1 M H(3)PO(4) or NaOH was connected and used as anode and cathode compartments, respectively. Reproducible fractionation of peptide could be achieved by collecting fractions with specific pH values when voltage reached a plateau by applying direct current at constant power. Running time necessary for fractionation of peptide was inversely proportional to electric power and directly proportional to sample volume.
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Affiliation(s)
- A Akahoshi
- Department of Food Sciences and Nutritional Health, Kyoto Prefectural University, Shimogamo, Kyoto 606-8522, Japan
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Abstract
Proteomic research, for its part, is benefiting enormously from the last decade of genomic research as we now have archived, annotated and audited sequence databases to correlate and query experimental data. While the two-dimensional electrophoresis (2-DE) gels are still a central part of proteomics, we reflect on the possibilities and realities of the current 2-DE technology with regard to displaying and analysing proteomes. Limitations of analysing whole cell/tissue lysates by 2-DE alone are discussed, and we investigate whether extremely narrow p/ranges (1 pH unit/25 cm) provide a solution to display comprehensive protein expression profiles. We are confronted with a challenging task: the dynamic range of protein expression. We believe that most of the existing technology is capable of displaying many more proteins than is currently achievable by integrating existing and new techniques to prefractionate samples prior to 2-DE display or analysis. The availability of a "proteomics toolbox", consisting of defined reagents, methods, and equipment, would assist a comprehensive analysis of defined biological systems.
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Affiliation(s)
- G L Corthals
- The Garvan Institute of Medical Research, St Vincent's Hospital, Sydney NSW, Australia.
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Bossi A, Olivieri E, Castelletti L, Gelfi C, Hamdan M, Righetti PG. General experimental aspects of the use of isoelectric buffers in capillary electrophoresis. J Chromatogr A 1999; 853:71-82. [PMID: 10486714 DOI: 10.1016/s0021-9673(99)00519-1] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Four acidic, isoelectric buffers, for peptide and protein separations, have been recently described and adopted in capillary zone electrophoresis: cysteic acid [Cys-A, isoelectric point (pI) 1.85], iminodiacetic acid (IDA, pI 2.23), aspartic acid (Asp, pI 2.77) and glutamic acid (Glu, pI 3.22). These four buffers allow to explore an acidic portion of the titration curves of macroions, covering about 1.6 pH units (from pH 1.85 to ca. 3.45), thus permitting resolution of compounds having coincident titration curves at a given pH value. Given the rather acidic pI values of these buffers, their long-term stability has been investigated, by monitoring pH and conductivity changes upon increasing storage times. When dissolved in plain water, all four buffers appear to give constant pH and conductivity readings up to 15 days; after that, the conductivity keeps steadily increasing in a similar fashion. The same parameters, when the same buffers are dissolved in 6 M urea, appear to be stable for only one week, with the conductivity progressively augmenting after this period. A similar behaviour is exhibited by histidine (pI 7.70), a neutral, isoelectric buffer adopted for separation of DNA fragments. By mass spectrometry, Cys-A shows minute amounts (ca. 1%) of a degradation product after ageing for 3 weeks; in the same time period, Glu is extensively degraded (20%). No degradation species could be detected in IDA and Asp solutions. It is additionally shown that the acidic buffers are not quite stationary in the electric field, but can be transported at progressively higher rates (according to the pI value) from the cathodic to the anodic vessel. This is due to the fact that, at their respective pI values, a fraction of the amphotere has to be negatively charged in order to provide counterions to the excess of protons due to bulk water dissociation. Guidelines are given for the proper use and storage of such buffers.
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Affiliation(s)
- A Bossi
- University of Verona, Department of Agricultural and Industrial Biotechnologies, Italy
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Righetti PG, Bossi A, Wenisch E, Orsini G. Protein purification in multicompartment electrolyzers with isoelectric membranes. JOURNAL OF CHROMATOGRAPHY. B, BIOMEDICAL SCIENCES AND APPLICATIONS 1997; 699:105-15. [PMID: 9392371 DOI: 10.1016/s0378-4347(97)00156-4] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Preparative purification of proteins under isoelectric conditions is reviewed, with particular regard to novel equipment, a multicompartment electrolyzer with isoelectric membranes, which can capture any desired protein into an isoelectric trap as the sole, ultra-pure component. This novel machine is based on the Immobiline chemistry, i.e. the novel generation of non-amphoteric buffers, based on the chemistry of acrylamides, which can be insolubilized onto polyacrylamide supports. After a description of the instrument and of its performance, a number of protein purification protocols are described, leading to truly homogeneous (by the most stringent criterion of surface charge) protein fractions. Such a high charge purity has been found to be often a fundamental prerequisite for the growth of protein crystals. Interfacing the electrolyzer with mass spectrometry has permitted the decoding of the structure of minor components generated from a parental molecule, especially ones having a higher pI. It was found that these species were often generated either by proteolytic cleavage or by the formation of a trisulphide bridge between two Cys residues. A unique application of the electrolyzer is finally described: its use as an immobilized enzyme reactor under an electric field. The performance of this reaction is outstanding, in that the kinetic parameters of the immobilized enzyme are identical to those of a free enzyme form.
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Affiliation(s)
- P G Righetti
- Department of Agricultural and Industrial Biotechnologies, University of Verona, Italy
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Bossi A, Righetti PG. Generation of peptide maps by capillary zone electrophoresis in isoelectric iminodiacetic acid. Electrophoresis 1997; 18:2012-8. [PMID: 9420161 DOI: 10.1002/elps.1150181122] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Capillary zone electrophoresis in stationary, isoelectric buffers is a novel method for generating peptide maps of protein digests. The buffer system developed is composed of iminodiacetic acid (IDA), whose physico-chemical parameters were found -- by theoretically modeling and experimental verification -- to be: pI 2.23 (at 100 mM concentration), pK1 = 1.73 and pK2 = 2.73 (no attempts were made at measuring the pK of the primary amino group, since such a low pI value would be compatible with any pK value of the basic group, down to as low as pK 5.5). IDA is compatible with most hydro-organic solvents, including trifluoroethanol (TFE), up to at least 40% v/v, typically used for modulating peptide mobility. In naked capillaries, a buffer comprising 50 mM IDA, 10% TFE and 0.5% hydroxyethylcellulose (HEC) allows generation of peptide maps with high resolution, reduced transit times and no interaction of even large peptides with the wall. However, the best background electrolyte was found to be a solution of 50 mM IDA in 0.5% HEC and 6-8 M urea, one of the best solubilizers of proteins and peptides known. In this last electrolyte system, peptide maps of beta-casein digests (known to contain also very large peptides, up to 6000 Da) could be generated with excellent resolution and half the transit times as compared with the standard buffer adopted in peptide analysis (80 mM phosphate buffer, pH 2.0). IDA thus appears to be another valid isoelectric buffer system, operating in a different pH window (pH 2.33 in 50 mM IDA) as compared to the other amphotere previously adopted (50 mM Asp, pH 2.77) for the same kind of analysis.
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Affiliation(s)
- A Bossi
- University of Verona, Department of Agricultural and Industrial Biotechnologies, Italy
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21
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Tulp A, Verwoerd D, Hart AA. Density gradient isoelectric focusing of proteins in artificial pH gradients made up of binary mixtures of amphoteric buffers. Electrophoresis 1997; 18:767-73. [PMID: 9194604 DOI: 10.1002/elps.1150180518] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
A density gradient electrophoresis apparatus made of Perspex (7 cm, O 2.2 cm) with a circular platinum anode and a palladium cathode was used for the separation of proteins in free liquid. Following a concept developed by M. Bier et al. (Electrophoresis 1993, 14, 1011-1018), mixtures of two suitable amphoteric buffers I and II provide for media with a fixed and electrophoretically stable pH or were used for the generation of preformed (electrophoretically stable) pH gradients covering about 1 pH unit. Amphoters I and II are considered suitable if there is overlap between (pK(1,1)-1-2) and the pK(2,II)+1+2) region. 3-(N-Morpholino)propanesulfonic acid (MOPS) and gamma-amino-n-butyric acid (GABA) were used as an example. Two approaches were followed: (i) rate-zonal separation of test proteins in a pH window, formed by a fixed ratio of MOPS/GABA. (ii) Isoelectric focusing in a shallow preformed pH gradient, made up of inverse reciprocal linear gradients of MOPS and GABA. At isopH, test proteins (bovine serum albumin, cytochrome c, ferritin, hemoglobin, lactoglobulin, myoglobin, and transferrin) were rate-zonally separated within a short time. Even the separation of the A and B forms of lactoglobulin was feasible at isopH. The glycoforms of transferrin were separated and enriched on a pH 5.2-6.1 pH gradient, indicating that pH differences of about 0.01 still permit resolution. Contrary to the ill-defined Ampholines, the cost of these well-defined amphoters is low.
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Affiliation(s)
- A Tulp
- The Netherlands Cancer Institute, Antoni van Leeuwenhoekhuis, Department of Cellular Biochemistry, Amsterdam
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Evans LL, Burns MA. Solute focusing techniques for bioseparations. BIO/TECHNOLOGY (NATURE PUBLISHING COMPANY) 1995; 13:46-52. [PMID: 9678909 DOI: 10.1038/nbt0195-46] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
The growth of industrial biotechnology has had a major impact on the research and development of both analytical and preparative focusing techniques. Pioneering methods such as isoelectric focusing are being modified to overcome the limitations of batch mode operation, scale up difficulties, high power requirement, and excessive heat generation. present advances in focusing techniques have been made by either overcoming the limitations of standard techniques or by investigating new focusing systems. Here we review the background and history of isoelectric focusing and discuss several new focusing techniques including recycle isoelectric (RIEF), counteracting chromatographic electrophoresis (CACE), and countercurrent gradient chromatography (CGC).
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Affiliation(s)
- L L Evans
- Department of Chemical Engineering, University of Michigan, Ann Arbor 48109, USA
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Weber W, Wenisch E, Günther N, Marnitz U, Betzel C, Righetti PG. Protein microheterogeneity and crystal habits: the case of epidermal growth factor receptor isoforms as isolated in a multicompartment electrolyzer with isoelectric membranes. J Chromatogr A 1994; 679:181-9. [PMID: 7951989 DOI: 10.1016/0021-9673(94)80325-0] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
A purified, soluble form of the epidermal growth factor receptor (sEGFR) was found, by isoelectric focusing in immobilized pH gradients, to consist of three major isoforms (with pI values 6.45, 6.71 and 6.96, respectively) and ca. a dozen minor components. This wild-type sEGFR, while producing crystals, has so far defied any attempt at decoding the structure, due to the very poor diffraction pattern. When the wild-type sEGFR was purified in a multicompartment electrolyzer with isoelectric Immobiline membranes, it yielded the three major isoforms as single-pI components, collected in three separate chambers of the recycling electrolyzer. The pI 6.71 and the pI 6.96 isoforms produced large crystals of apparent good quality. However, while the former produced a high-quality diffraction pattern, which may lead to decoding of three-dimensional structure, the pI 6.96 produced crystals which did not diffract at all. It is concluded that, in the case of "tough" proteins (large size, heterogeneous glycosylation, high water content of crystals), purification to single-charge components might be an essential step for growing proper crystals. The unique advantage of purification via isoelectric membranes is that the protein is collected both isoelectric and isoionic, i.e. uncontaminated by soluble buffers (such as the carrier ampholytes used in conventional focusing).
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Affiliation(s)
- W Weber
- Institut für Physiologische Chemie, Universitätskrankenhaus Eppendorf, Hamburg, Germany
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Caslavska J, Thormann W. Isolation of human serum transferrin by free-fluid recycling electrophoresis in simple buffers. Electrophoresis 1994; 15:1176-85. [PMID: 7859726 DOI: 10.1002/elps.11501501177] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The isolation of human serum transferrin (Tf) using recycling isotachophoresis (RITP) and recycling isoelectric focusing (RIEF) with simple buffers is described. Serum fractionation, the first step in the protocol for Tf purification, is shown to be easily performed either by RITP of filtered serum using low molecular mass spacers or by RIEF of dialyzed serum employing a binary mixture of a well-defined buffer pair covering the pH range between 5.2 and 6.2, called RIEF-OptiFocus. For polishing, Tf-containing fractions are reprocessed by RITP or RIEF-OptiFocus. Other RIEF approaches based on the use of single amino acids at high concentration and ternary amino acid mixtures are shown to constitute less effective methods for Tf isolation. With a four-step protocol, comprising in turn RITP, RIEF-OptiFocus, ultrafiltration and again RITP, "single-band" purity (as assessed by two-dimensional gel electrophoresis) is obtained. Omission of the first step (RITP) and direct processing of dialyzed serum by RIEF-OptiFocus, ultrafiltration and RITP, is shown to provide remarkable results as well.
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Affiliation(s)
- J Caslavska
- Department of Clinical Pharmacology, University of Berne, Switzerland
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Chiari M, Nesi M, Roncada P, Righetti PG. Preparative isoelectric focusing in multicompartment electrolyzers: novel, hydrolytically stable and hydrophilic isoelectric membranes. Electrophoresis 1994; 15:953-9. [PMID: 7813401 DOI: 10.1002/elps.11501501139] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Preparative isoelectric focusing in multicompartment electrolyzers is based on the production of isoelectric membranes of precise isoelectric point, able to buffer at their pI value and to titrate proteins tangent to or crossing the membranes. Up to the present, such membranes have been based on polyacrylamide chemistry; acrylamide, however, is neither stable in acidic nor basic environments. We describe here novel membranes, produced with a unique monomer, N-acryloylaminoethoxyethanol (AAEE). Poly(AAEE) membranes are extremely stable to alkaline hydrolysis (500 times more stable than polyacrylamide) and even more hydrophilic than the latter matrix. This allows production of highly reproducible membranes (these do not change their pI with time, since no acrylic acid is produced by hydrolysis upon storage) which do not adsorb proteins by hydrophobic interaction.
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Affiliation(s)
- M Chiari
- Istituto di Chimica degli Ormoni, CNR, Milano, Italy
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Bier M, Ostrem J, Marquez RB. A new buffering system and its use in electrophoresis and isoelectric focusing. Electrophoresis 1993; 14:1011-8. [PMID: 8125048 DOI: 10.1002/elps.11501401161] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
A novel buffer system with rather unique properties particularly well suited for preparative isoelectric focusing is described. The system was developed in response to the long standing need for pH gradients formulated using inexpensive components of known chemical composition. The system is binary consisting of buffer pairs covering the pH range of 3 to 10, in increments of less than 1 pH. The components are all readily available, nontoxic, and biologically acceptable, and are selected on the basis of their dissociation constants. The requirement for each buffer pair is that there be an overlapping pH zone where both components are largely non-ionized, having a ratio of neutral species to total buffer concentration between about 0.90 and 0.99. This ratio is defined as the 'electrophoretic reserve capacity' (ERC). Within the above ERC range a stable pH gradient is obtained, assuring sharply resolved protein focusing. Buffer parameters, mainly pH, buffering capacity, ERC, transport numbers, and conductivity, can be easily calculated and the buffer composition adjusted to meet requirements. All components are used at high concentration, typically of the order of up to 100 mM, yielding buffering capacities and conductivities analog to those customary in electrophoresis.
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Affiliation(s)
- M Bier
- Center for Separation Science, University of Arizona, Tucson 85721
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