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Haidar Ahmad IA, Bennett R, Makey D, Shchurik V, Lhotka H, Mann BF, McClain R, Lu T, Hua X, Strulson CA, Loughney JW, Mangion I, Makarov AA, Regalado EL. In silico method development for the reversed-phase liquid chromatography separation of proteins using chaotropic mobile phase modifiers. J Chromatogr B Analyt Technol Biomed Life Sci 2021; 1173:122587. [PMID: 33845343 DOI: 10.1016/j.jchromb.2021.122587] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2020] [Revised: 02/02/2021] [Accepted: 02/05/2021] [Indexed: 10/22/2022]
Abstract
Recent advances in biomedical and pharmaceutical processes has enabled a notable increase of protein- and peptide-based drug therapies and vaccines that often contain a higher-order structure critical to their efficacy. Hyphenation of chromatographic and spectrometric techniques is at the center of all facets of biopharmaceutical analysis, purification and chemical characterization. Although computer-assisted chromatographic modeling of small molecules has reached a mature stage across the pharmaceutical industry, software-based method optimization approaches for large molecules has yet to see the same revitalization. Conformational changes of biomolecules under chromatographic conditions have been identified as the major culprit in terms of sub-optimal modeling outcomes. In order to circumvent these challenges, we herein investigate the outcomes generated via computer-assisted modeling from using different chaotropic and denaturing mobile phases (trifluoroacetic acid, sodium perchlorate and guanidine hydrochloride in acetonitrile/water-based eluents). Linear and polynomial regression retention models using ACD/Labs software were built as a function of gradient slope, column temperature and mobile phase buffer for eight different model proteins ranging from 12 to 670 kDa (holo-transferrin, cytochrome C, apomyoglobin, ribonuclease A, ribonuclease A type I-A, albumin, y-globulin and thyroglobulin bovine). Correlation between experimental and modeled outputs was substantially improved by using strong chaotropic and denaturing modifiers in the mobile phase, even when using linear regression modeling as typically observed for small molecules. On the contrary, the use of conventional TFA buffer concentrations at low column temperatures required the used of polynomial regression modeling indicating potential conformational structure changes of proteins upon chromatographic conditions. In addition, we illustrate the power of modern computer-assisted chromatography modeling combined with chaotropic agents in the developing of new RPLC assays for protein-based therapeutics and vaccines.
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Affiliation(s)
- Imad A Haidar Ahmad
- Analytical Research & Development, Merck & Co., Inc., Rahway, NJ 07065, USA.
| | - Raffeal Bennett
- Analytical Research & Development, Merck & Co., Inc., Rahway, NJ 07065, USA
| | - Devin Makey
- Department of Chemistry, Gustavus Adolphus College, Saint Peter, MN 56082, USA; Department of Chemistry, University of Michigan, Ann Arbor, MI 48109, USA
| | - Vladimir Shchurik
- Analytical Research & Development, Merck & Co., Inc., Rahway, NJ 07065, USA
| | - Hayley Lhotka
- Department of Chemistry, Gustavus Adolphus College, Saint Peter, MN 56082, USA; Department of Chemistry, University of Michigan, Ann Arbor, MI 48109, USA
| | - Benjamin F Mann
- Analytical Research & Development, Merck & Co., Inc., Rahway, NJ 07065, USA
| | - Ray McClain
- Analytical Research & Development, Merck & Co. Inc., West Point, PA 19486, USA
| | - Tian Lu
- Analytical Research & Development, Merck & Co. Inc., West Point, PA 19486, USA
| | - Xiaoqing Hua
- Analytical Research & Development, Merck & Co. Inc., Kenilworth, NJ 07033, USA
| | | | - John W Loughney
- Analytical Research & Development, Merck & Co. Inc., West Point, PA 19486, USA
| | - Ian Mangion
- Analytical Research & Development, Merck & Co., Inc., Rahway, NJ 07065, USA
| | - Alexey A Makarov
- Analytical Research & Development, Merck & Co., Inc., Boston, MA 02115, USA.
| | - Erik L Regalado
- Analytical Research & Development, Merck & Co., Inc., Rahway, NJ 07065, USA.
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Shimizu H, Toyoda K, Mawatari K, Terabe S, Kitamori T. Femtoliter Gradient Elution System for Liquid Chromatography Utilizing Extended Nanofluidics. Anal Chem 2019; 91:3009-3014. [PMID: 30661360 DOI: 10.1021/acs.analchem.8b05302] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
A gradient system was developed for the separation of proteins on a femtoliter scale utilizing nanofluidic channels. In the history of chromatography, miniaturization of the separation column has been important for efficient separation and downsizing of instruments. Previously, our group developed a small and highly efficient chromatography system utilizing nanofluidic channels, although a flexible design of the gradient was difficult and separation of proteins was not achieved. Here, we propose a flexible gradient system using standard HPLC pumps and an auxiliary mixer with a simple sample injection system. In contrast to our previous sample injection system using pressure balance, the system enables a femtoliter-scale sample injection which is compatible with gradient elution using HPLC pumps. The system was carefully designed, verified for sample injection and gradient elution, and finally applied to the separation of proteins from model and real samples. This femtoliter-scale, efficient separation system will contribute to omics studies at the single-cell level.
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Affiliation(s)
- Hisashi Shimizu
- International Research Center for Neurointelligence , The University of Tokyo , 7-3-1, Hongo , Bunkyo, Tokyo 113-0033 , Japan
| | - Kouto Toyoda
- Department of Applied Chemistry, School of Engineering , The University of Tokyo , 7-3-1, Hongo , Bunkyo, Tokyo 113-8656 , Japan
| | - Kazuma Mawatari
- Department of Applied Chemistry, School of Engineering , The University of Tokyo , 7-3-1, Hongo , Bunkyo, Tokyo 113-8656 , Japan
| | - Shigeru Terabe
- Graduate School of Material Science , University of Hyogo , 3-2-1, Kouto , Kamigori , Hyogo 678-1297 , Japan
| | - Takehiko Kitamori
- Department of Applied Chemistry, School of Engineering , The University of Tokyo , 7-3-1, Hongo , Bunkyo, Tokyo 113-8656 , Japan
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2D-LC as an on-line desalting tool allowing peptide identification directly from MS unfriendly HPLC methods. J Pharm Biomed Anal 2017; 137:139-145. [DOI: 10.1016/j.jpba.2016.11.012] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2016] [Revised: 10/20/2016] [Accepted: 11/09/2016] [Indexed: 11/20/2022]
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4
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Mant CT, Jiang Z, Boyes BE, Hodges RS. An improved approach to hydrophilic interaction chromatography of peptides: salt gradients in the presence of high isocratic acetonitrile concentrations. J Chromatogr A 2013; 1277:15-25. [PMID: 23332786 PMCID: PMC3639484 DOI: 10.1016/j.chroma.2012.12.044] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2012] [Revised: 12/17/2012] [Accepted: 12/20/2012] [Indexed: 12/31/2022]
Abstract
Hydrophilic interaction chromatography (HILIC) for separations of peptides has been employed infrequently, particularly considering that this technique was introduced over 20 years ago. The present manuscript describes a radical departure from the traditional HILIC elution approach, where separations are achieved via increasing salt (sodium perchlorate) gradients in the presence of high isocratic concentrations (>80%) of acetonitrile, denoted HILIC/SALT. This initial study compared to reversed-phase chromatography (RPC), HILIC and HILIC/SALT for the separation of mixtures of synthetic peptide standards varying in structure (amphipathic α-helix, random coil), length (10-26 residues), number of positively charged residues (+1 to +11) and hydrophilicity/hydrophobicity. Results showed a marked superiority of the HILIC/SALT approach compared to traditional HILIC and excellent complementarity to RPC for peptide separations. We believe these initial results offer a new dimension to HILIC, enabling it to transform from an occasional HPLC approach for peptide separations to a more generally applicable method.
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Affiliation(s)
- Colin T. Mant
- Department of Biochemistry and Molecular Genetics, University of Colorado Denver, School of Medicine, Aurora, CO 80045, USA
| | - Ziqing Jiang
- Department of Biochemistry and Molecular Genetics, University of Colorado Denver, School of Medicine, Aurora, CO 80045, USA
| | - Barry E. Boyes
- Advanced Materials Technology, Inc., Wilmington, DE 19810, USA
- CCRC, Department of Chemistry, University of Georgia, Athens, GA 30602, USA
| | - Robert S. Hodges
- Department of Biochemistry and Molecular Genetics, University of Colorado Denver, School of Medicine, Aurora, CO 80045, USA
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Balchen M, Hatterud AG, Reubsaet L, Pedersen-Bjergaard S. Fundamental studies on the electrokinetic transfer of net cationic peptides across supported liquid membranes. J Sep Sci 2010; 34:186-95. [DOI: 10.1002/jssc.201000703] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2010] [Revised: 11/05/2010] [Accepted: 11/05/2010] [Indexed: 11/10/2022]
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Makarov A, LoBrutto R, Kazakevich Y. Liophilic Mobile Phase Additives in Reversed Phase HPLC. J LIQ CHROMATOGR R T 2010. [DOI: 10.1080/10826070802125918] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Affiliation(s)
- Alexey Makarov
- a Novartis Pharmaceuticals, Pharmaceutical and Analytical Development , East Hanover, New Jersey, USA
| | - Rosario LoBrutto
- a Novartis Pharmaceuticals, Pharmaceutical and Analytical Development , East Hanover, New Jersey, USA
| | - Yuri Kazakevich
- b Department of Chemistry and Biochemistry , Seton Hall University , Orange, New Jersey, USA
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Abbood A, Smadja C, Taverna M, Herrenknecht C. High performance liquid chromatography separation of structurally related enkephalins on quaternary ammonium-embedded stationary phase in isocratic mode. J Chromatogr A 2010; 1217:450-8. [DOI: 10.1016/j.chroma.2009.11.058] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2009] [Revised: 11/13/2009] [Accepted: 11/17/2009] [Indexed: 12/15/2022]
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Peptide pore accessibility in reversed-phase chromatography. J Chromatogr A 2009; 1216:933-40. [DOI: 10.1016/j.chroma.2008.12.019] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2008] [Revised: 12/03/2008] [Accepted: 12/05/2008] [Indexed: 11/21/2022]
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Mant CT, Hodges RS. Mixed-mode hydrophilic interaction/cation-exchange chromatography (HILIC/CEX) of peptides and proteins. J Sep Sci 2008; 31:2754-73. [PMID: 18668504 PMCID: PMC2774265 DOI: 10.1002/jssc.200800243] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
This review represents a summary of the development and application of a novel mixed-mode HPLC approach to the separation and analysis of peptides and proteins termed hydrophilic interaction/cation-exchange chromatography (HILIC/CEX). This approach combines the most advantageous aspects of two widely different separation mechanisms, i.e. a separation based on hydrophilicity/hydrophobicity differences between polypeptides overlaid on a separation based on net charge. Applications described include HILIC/CEX separations of cyclic peptides, alpha-helical peptides, random coil peptides and modified or deletion products of synthetic peptides. In addition, the excellent resolving ability of HILIC/CEX for modified histone proteins is described. This approach is shown to represent an excellent complement to RP chromatography (RPC), as well as being a potent analytical tool in its own right.
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Affiliation(s)
- Colin T Mant
- Department of Biochemistry and Molecular Genetics, University of Colorado Denver, School of Medicine, Anschutz Medical Campus, Aurora, CO 80045, USA
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Mant CT, Hodges RS. Mixed-mode hydrophilic interaction/cation-exchange chromatography: separation of complex mixtures of peptides of varying charge and hydrophobicity. J Sep Sci 2008; 31:1573-84. [PMID: 18461566 DOI: 10.1002/jssc.200700619] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Mixed-mode hydrophilic interaction/cation-exchange chromatography (HILIC/CEX) was applied to the separation of two mixtures of synthetic peptide standards: (i) a 27-peptide mixture containing three groups of peptides (each group containing nine peptides of the same net charge of +1, +2 or +3), where the hydrophilicity/hydrophobicity of adjacent peptides within the groups varied only subtly (generally by only a single carbon atom); and (ii) peptide pairs with the same composition but different sequences, where the sole difference between the peptides was the position of a single amino acid substitution. HILIC/CEX is essentially CEX chromatography in the presence of high levels of organic modifier (generally ACN). The present study demonstrated the dramatic effect of increasing ACN concentration (optimum levels of 60-80%, depending on the application) on the separation of both mixtures of peptides. The greater the charge on the peptides, the better the separation achievable by HILIC/CEX. In addition, HILIC/CEX separation of both the peptide mixtures used in the present study was shown to be superior to that of the more commonly applied RP-HPLC mode. Our results highlight again the efficacy of HILIC/CEX as a peptide separation mode in its own right as well as an excellent complement to RP-HPLC.
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Affiliation(s)
- Colin T Mant
- Department of Biochemistry and Molecular Genetics, School of Medicine, University of Colorado Denver, CO, USA
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Yilmaz O, Keser S, Tuzcu M, Cetintaş B. Resveratrol (trans-3,4',5-trihydroxystilbene) decreases lipid peroxidation level and protects antioxidant capacity in sera and erythrocytes of old female Wistar rats induced by the kidney carcinogen potassium bromate. ENVIRONMENTAL TOXICOLOGY AND PHARMACOLOGY 2007; 24:79-85. [PMID: 21783793 DOI: 10.1016/j.etap.2007.05.007] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/17/2006] [Accepted: 10/11/2006] [Indexed: 05/31/2023]
Abstract
Resveratrol is a natural polyphenolic compound and it is found in number of edible plants, especially grapes and peanuts, has been shown to have anti-inflammatory, anti-oxidant, anti-tumor and anti-platelet activities. The aim of the study was to examine the effects of resveratrol on the level of malondialdehyde (MDA), homocysteine, cholesterol, GSH, GSSG and lipophylic vitamins in serum and erythrocytes of old female Wistar rats induced by the kidney carcinogen potassium bromate (KBrO(3)). In the study, total 30-old female Wistar rats were used, and the rats were randomly divided into three groups. The first group was used as a control, the second group KBrO(3) group, and third group R+KBrO(3). Rats in KBrO(3) and R+KBrO(3) groups were injected intraperitoneally a single dose KBrO(3) (80mg/kg) in physiologic saline buffer. After 2days, those in R+KBrO(3) group were intraperitoneally injected with resveratrol (33mg/kg) four times per week, and physiological saline was injected to control group rats. All the analysis was performed fully automatic with high performance liquid chromatography equipment. The results indicate that serum cholesterol level in the R+KBrO(3) group was higher than the control group (p<0.05), and level of the cholesterol in erythrocytes membranes was lower in the same group (p<0.01). The MDA level in serum and erythrocytes of the R+KBrO(3) were lower than the control and KBrO(3) groups (p<0.01). However, the MDA level in erythrocytes of the KBrO(3) group was high compared to the control group (p<0.05). Homocysteine and δ-tocopherol levels in serum of the R+KBrO(3) group were lower than the control group (p<0.05, p<0.001). α-Tocopherol level in serum and erythrocytes of the KBrO(3) group was lower than the control group (p<0.05), whereas its level was not found to differ between the control and R+KBrO(3) groups. GSH and GSSG levels in the KBrO(3) group of erythrocytes were higher than control group (p<0.05, p<0.01), however the ratio GSH/GSSG in the same group was lower than control group. In conclusion, our results confirm that the lipid peroxidation formation in serum and erythrocytes of old female Wistar rats by induced the KBrO(3) is prevented by the resveratrol. It was observed that the antioxidant capacity of erythrocytes was protected by resveratrol.
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Affiliation(s)
- Okkeş Yilmaz
- Firat University, Faculty of Science, Biology Department, 23169-Elazıg, Turkey
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12
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Vailaya A. Fundamentals of Reversed Phase Chromatography: Thermodynamic and Exothermodynamic Treatment. J LIQ CHROMATOGR R T 2007. [DOI: 10.1081/jlc-200052969] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Affiliation(s)
- Anant Vailaya
- a Merck Research Laboratories , Rahway, New Jersey, USA
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Kovacs JM, Mant CT, Kwok SC, Osguthorpe DJ, Hodges RS. Quantitation of the nearest-neighbour effects of amino acid side-chains that restrict conformational freedom of the polypeptide chain using reversed-phase liquid chromatography of synthetic model peptides with L- and D-amino acid substitutions. J Chromatogr A 2006; 1123:212-24. [PMID: 16712857 PMCID: PMC1976429 DOI: 10.1016/j.chroma.2006.04.092] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2005] [Revised: 04/18/2006] [Accepted: 04/28/2006] [Indexed: 10/24/2022]
Abstract
Side-chain backbone interactions (or "effects") between nearest neighbours may severely restrict the conformations accessible to a polypeptide chain and thus represent the first step in protein folding. We have quantified nearest-neighbour effects (i to i+1) in peptides through reversed-phase liquid chromatography (RP-HPLC) of model synthetic peptides, where L- and D-amino acids were substituted at the N-terminal end of the peptide sequence, adjacent to a L-Leu residue. These nearest-neighbour effects (expressed as the difference in retention times of L- and D-peptide diastereomers at pHs 2 and 7) were frequently dramatic, depending on the type of side-chain adjacent to the L-Leu residue, albeit such effects were independent of mobile phase conditions. No nearest-neighbour effects were observed when residue i is adjacent to a Gly residue. Calculation of minimum energy conformations of selected peptides supported the view that, whether a L- or D-amino acid is substituted adjacent to L-Leu, its orientation relative to this bulky Leu side-chain represents the most energetically favourable configuration. We believe that such energetically favourable, and different, configurations of L- and D-peptide diastereomers affect their respective interactions with a hydrophobic stationary phase, which are thus quantified by different RP-HPLC retention times. Side-chain hydrophilicity/hydrophobicity coefficients were generated in the presence of these nearest-neighbour effects and, despite the relative difference in such coefficients generated from peptides substituted with L- or D-amino acids, the relative difference in hydrophilicity/hydrophobicity between different amino acids in the L- or D-series is maintained. Overall, our results demonstrate that such nearest-neighbour effects can clearly restrict conformational space of an amino acid side-chain in a polypeptide chain.
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Affiliation(s)
- James M Kovacs
- Department of Biochemistry and Molecular Genetics, University of Colorado at Denver and Health Sciences Center, Aurora, CO 80045, USA
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Riddle LA, Guiochon G. Influence of Mobile Phase Gradients on the Retention and Separation of Peptides from a Cytochrome-c Digest by Reversed-Phase Liquid Chromatography. Chromatographia 2006. [DOI: 10.1365/s10337-006-0839-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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Flieger J. The effect of chaotropic mobile phase additives on the separation of selected alkaloids in reversed-phase high-performance liquid chromatography. J Chromatogr A 2006; 1113:37-44. [PMID: 16545827 DOI: 10.1016/j.chroma.2006.01.090] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2005] [Revised: 01/16/2006] [Accepted: 01/19/2006] [Indexed: 10/24/2022]
Abstract
The retention behavior of selected alkaloids from different classes was studied. The effect of chaotropic salts additives to the mobile phase on chromatographic parameters of protonated basic analytes was investigated on Zorbax Extend-C18 column. The influence of the type of salts and their concentration on retention, efficiency, peak symmetry and separation selectivity of investigated alkaloids was established. Buffered acetonitrile-water mobile phase was chosen because of significant retention of added liophilic ions due to strong dispersive pi-pi interactions. These conditions are responsible for great contribution of electrostatic forces in the retention of protonated bases. The addition of salt, such as hexafluorophosphate, perchlorate, trifluoroacetate leads to the increase in retention, efficiency and separation selectivity of examined analytes. The influence of added salts on increase in retention parameters could be expressed as follows: H2PO4- < CF3COO- < ClO4- < PF6-. This order is in agreement with ability of salts to "salting-in" effect according to Hofmeister series. Obtained chromatograms of alkaloids mixture illustrate suitability of chaotropic effect to improve their separation selectivity.
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Affiliation(s)
- J Flieger
- Department of Inorganic and Analytical Chemistry, Medical University of Lublin, 20-081 Lublin, Staszica 6, Poland.
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Drapała A, Jönsson JÅ, Wieczorek P. Peptides analysis in blood plasma using on-line system of supported liquid membrane and high-performance liquid chromatography. Anal Chim Acta 2005. [DOI: 10.1016/j.aca.2005.08.008] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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17
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Shibue M, Mant C, Hodges R. The perchlorate anion is more effective than the trifluoroacetate anion as an ion-pairing reagent for reversed-phase chromatography of peptides. J Chromatogr A 2005; 1080:49-57. [PMID: 16013614 PMCID: PMC2722116 DOI: 10.1016/j.chroma.2005.02.063] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The addition of salts, specifically sodium perchlorate (NaClO4), to mobile phases at acidic pH as ion-pairing reagents for reversed-phase high-performance liquid chromatography (RP-HPLC) has been generally overlooked. To demonstrate the potential of NaClO4 as an effective anionic ion-pairing reagent, we applied RP-HPLC in the presence of 0-100 mM sodium chloride (NaCl), sodium trifluoroacetate (NaTFA) or NaClO4 to two mixtures of synthetic 18-residue peptides: a mixture of peptides with the same net positive charge (+4) and a mixture of four peptides of +1, +2, +3 and +4 net charge. Interestingly, the effect of increasing NaClO4 concentration on increasing peptide retention times and selectivity changes was more dramatic than that of either NaCl or NaTFA, with the order of increasing anion effectiveness being Cl- << TFA- < C104-. Such effects were more marked when salt addition was applied to eluents containing 10 mM phosphoric acid (H3PO4) compared to 10 mM trifluoroacetic acid (TFA) due to the lesser starting anion hydrophobicity of the former mobile phase (containing the phosphate ion) compared to the latter (containing the TFA- ion).
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Affiliation(s)
| | | | - R.S. Hodges
- Corresponding author. Tel.: +1 303 724 3253; fax: +1 303 724 3249., E-mail address: (R.S. Hodges)
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Soukupová K, Krafková E, Suchánková J, Tesarová E. Comparison of zirconia- and silica-based reversed stationary phases for separation of enkephalins. J Chromatogr A 2005; 1087:104-11. [PMID: 16130703 DOI: 10.1016/j.chroma.2005.01.058] [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: 12/29/2022]
Abstract
In this study, the separation of biologically active peptides on two zirconia-based phases, polybutadiene (PBD)-ZrO2 and polystyrene (PS)-ZrO2, and a silica-based phase C18 was compared. Basic differences in interactions on both types of phases led to quite different selectivity. The retention characteristics were investigated in detail using a variety of organic modifiers, buffers, and temperatures. These parameters affected retention, separation efficiency, resolution and symmetry of peaks. Separation systems consisting of Discovery PBD-Zr column and mobile phase composed of a mixture of acetonitrile and phosphate buffer, pH 2.0 (45:55, v/v) at 70 degrees C and Discovery PS-Zr with acetonitrile and phosphate buffer, pH 3.5 in the same (v/v) ratio at 40 degrees C were suitable for a good resolution of enkephalin related peptides. Mobile phase composed of acetonitrile and phosphate buffer, pH 5.0 (22:78, v/v) was appropriate for separation of enkephalins on Supelcosil C18 stationary phase.
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Affiliation(s)
- K Soukupová
- Department of Analytical Chemistry, Faculty of Science, Charles University, Albertov 2030, 12840 Prague 2, Czech Republic
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Chen Y, Mant CT, Hodges RS. Selectivity differences in the separation of amphipathic α-helical peptides during reversed-phase liquid chromatography at pHs 2.0 and 7.0. J Chromatogr A 2004; 1043:99-111. [PMID: 15317418 DOI: 10.1016/j.chroma.2004.04.028] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
In an ongoing effort to understand the effect of varying reversed-phase high-performance liquid chromatography (RP-HPLC) parameters on the retention behaviour of peptides, necessary for the rational development of separation/optimization protocols, we believe it is important to delineate the contribution of alpha-helical structure to the selectivity of peptide separations. The present study reports the effects of varying column packing, mobile phase conditions and temperature on RP-HPLC retention behaviour at pHs 2.0 and 7.0 of peptides based on the amphipathic peptide sequence Ac-EAEKAAKEXEKAAKEAEK-amide (with position X in the centre of the hydrophobic face of the alpha-helix), where position X is substituted by L- or D-amino acids. At pH 2.0, an increase in trifluoroacetic acid concentration or the addition of sodium perchlorate to a phosphoric acid-based mobile phase had the similar effect of improving peak shape as well as increasing peptide retention time due to ion-pairing effects with the positively-charged peptides; in contrast, at pH 7.0, the addition of salt had little effect save an improvement in peak shape. Temperature was shown to have a complex influence on peptide selectivity due to varying effects on peptide conformation. In addition, subtle effects on peptide selectivity were also noted based on the column packings employed at pHs 2.0 and 7.0.
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Affiliation(s)
- Y Chen
- Department of Biochemistry and Molecular Genetics, University of Colorado Health, Sciences Center, Denver, CO 80262, USA
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Loukili B, Dufresne C, Jourdan E, Grosset C, Ravel A, Villet A, Peyrin E. Study of tryptophan enantiomer binding to a teicoplanin-based stationary phase using the perturbation technique. Investigation of the role of sodium perchlorate in solute retention and enantioselectivity. J Chromatogr A 2003; 986:45-53. [PMID: 12585321 DOI: 10.1016/s0021-9673(02)01952-0] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The retention of D,L-tryptophan enantiomers on an immobilized teicoplanin column was investigated in relation to the mobile phase sodium perchlorate concentration using the perturbation method to determine the solute distribution isotherms. From the experimental data, it appeared that the bi-Langmuir model was able to describe D- and L-enantiomer retention on the immobilized selector over the salt concentration range. An increase in the apparent enantioselectivity with an increase in sodium perchlorate concentration was observed. The chiral recognition enhancement was governed by (i) an increase in the difference of the adsorption constants for binding to the high-affinity site (aglycone pocket) between the two enantiomers and (ii) enhancement of the number of aglycone chiral regions interacting with D-tryptophan. It is suggested that an ion-pair formation mechanism between perchlorate and solute and/or selector is responsible for this behavior. In addition, this work shows that additional secondary sites on the teicoplanin surface are involved in the apparent enantioselectivity at low sodium perchlorate concentrations.
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Affiliation(s)
- Bouchra Loukili
- Equipe de Chimie Analytique, Département de Pharmacochimie Moléculaire, UMR 5063 CNRS-UJF, UFR de Pharmacie de Grenoble, Domaine de la Merci, 38700 La Tronche, France
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21
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LoBrutto R, Jones A, Kazakevich YV, McNair HM. Effect of the eluent pH and acidic modifiers in high-performance liquid chromatography retention of basic analytes. J Chromatogr A 2001; 913:173-87. [PMID: 11355811 DOI: 10.1016/s0021-9673(00)01012-8] [Citation(s) in RCA: 105] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The retention of ionogenic bases in liquid chromatography is strongly dependent upon the pH of the mobile phase. Chromatographic behavior of a series of substituted aniline and pyridine basic compounds has been studied on C18 bonded silica using acetonitrile-water (10:90) as the eluent with different pHs and at various concentrations of the acidic modifier counter anions. The effect of different acidic modifiers on solute retention over a pH range from 1.3 to 8.6 was studied. Ionized basic compounds showed increased retention with a decrease of the mobile phase pH. This increase in retention was attributed to the interaction with counter anions of the acidic modifiers. The increase in retention is dependent on the nature of the counter anion and its concentration in the mobile phase. It was shown that altering the concentration of counter anion of the acidic modifier allows the optimization of the selectivity between basic compounds as well as for neutral and acidic compounds.
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Affiliation(s)
- R LoBrutto
- Seton Hall University, Department of Chemistry, South Orange, NJ, USA
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22
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Viklund C, Sjögren A, Irgum K, Nes I. Chromatographic interactions between proteins and sulfoalkylbetaine-based zwitterionic copolymers in fully aqueous low-salt buffers. Anal Chem 2001; 73:444-52. [PMID: 11217744 DOI: 10.1021/ac000618r] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Macroporous monoliths containing N,N-dimethyl-N-methacryloyloxyethyl-N-(3-sulfopropyl)ammonium betaine (SPE) have been synthesized via in situ photopolymerization, yielding a stoichiometric balance between sulfur and nitrogen in the final polymer, which is indicative of a genuine strong/strong zwitterionic character. The chromatographic properties of these zwitterionic resins were evaluated with respect to the retention behavior of inorganic ions and proteins. The weak electrostatic nature of the interaction between the sulfobetaine monoliths and proteins provided a high selectivity between basic proteins and peptides. Elution was accomplished with low-ionic-strength fully aqueous mobile phases, whereby high recovery was obtained, even for hydrophobic proteins. Chaotropic ions such as perchlorate or thiocyanate were used as mobile phase modifiers to modulate the apparent ion exchange group density, thus introducing a route for the modulation of the ionic strength that is required to competitively elute the protein. The promising features of polymeric sulfoalkylbetaine interaction layers for separation and analysis of biological extracts was also manifested in an application involving purification of biologically active peptide-pheromone obtained from Enterococcus faecium.
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Affiliation(s)
- C Viklund
- Department of Analytical Chemistry, Umeå University, Sweden
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23
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Yoshida T, Okada T, Hobo T, Chiba R. Calculation of amino acid hydrophilicity indices for retention of peptides on amide, diol and silica columns in normal-phase liquid chromatography. Chromatographia 2000. [DOI: 10.1007/bf02535713] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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24
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Evaluation of trifluoroacetic acid as an ion-pair reagent in the separation of small ionizable molecules by reversed-phase liquid chromatography. Anal Chim Acta 1999. [DOI: 10.1016/s0003-2670(99)00461-4] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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25
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Litowski JR, Semchuk PD, Mant CT, Hodges RS. Hydrophilic interaction/cation-exchange chromatography for the purification of synthetic peptides from closely related impurities: serine side-chain acetylated peptides. THE JOURNAL OF PEPTIDE RESEARCH : OFFICIAL JOURNAL OF THE AMERICAN PEPTIDE SOCIETY 1999; 54:1-11. [PMID: 10448964 DOI: 10.1034/j.1399-3011.1999.00066.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Mixed-mode hydrophilic interaction/cation-exchange chromatography (HILIC/CEC) is a novel HPLC technique which has excellent potential for peptide separations. Separations by HILIC/CEC are carried out by subjecting peptides to linear increasing salt gradients in the presence of high levels of acetonitrile, which promotes hydrophilic interactions overlayed on ionic interactions with the cation-exchange matrix. Complex peptide mixtures produced by solid-phase synthesis are a frequently encountered and challenging purification problem. In the present study a two-step protocol, consisting of HILIC/CEC followed by RPC, was required for the successful purification of a 21-residue synthetic amphipathic alpha-helical peptide from serine side-chain acetylated impurities, with HILIC/CEC proving to be highly sensitive to subtle differences in hydrophilicities between the acetylated peptides and the desired product. Investigation of the three potential sites of serine acetylation through solid-phase synthesis of acetylated analogues of the desired peptide (peptides of the same sequence and secondary structure, but acetylated at different positions on the hydrophilic face of the alpha-helix) demonstrated that acetylation was occurring at different sites on the peptide. HILIC/CEC was able to take advantage of very subtle changes in environment around the acetylation sites and thus effect a separation of these analogues not achievable by RPC or CEC alone.
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Affiliation(s)
- J R Litowski
- Department of Biochemistry and the Medical Research Council of Canada Group in Protein Structure and Function, University of Alberta, Edmonton
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26
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Larive CK, Lunte SM, Zhong M, Perkins MD, Wilson GS, Gokulrangan G, Williams T, Afroz F, Schöneich C, Derrick TS, Middaugh CR, Bogdanowich-Knipp S. Separation and analysis of peptides and proteins. Anal Chem 1999; 71:389R-423R. [PMID: 10409086 DOI: 10.1021/a1990013o] [Citation(s) in RCA: 73] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- C K Larive
- Department of Chemistry, University of Kansas, Lawrence, Kansas 66045
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27
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Mant CT, Litowski JR, Hodges RS. Hydrophilic interaction/cation-exchange chromatography for separation of amphipathic alpha-helical peptides. J Chromatogr A 1998; 816:65-78. [PMID: 9741101 DOI: 10.1016/s0021-9673(98)00507-x] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Mixed-mode hydrophilic interaction/cation-exchange chromatography (HILIC/CEX) is a novel high-performance technique which has excellent potential for peptide separations. Separations by HILIC/CEX are carried out by subjecting peptides to linear increasing salt gradients in the presence of high levels of acetonitrile, which promotes hydrophilic interactions overlaid on ionic interactions with the cation-exchange matrix. In the present study, HILIC/CEX has been applied to the separation of synthetic amphipathic alpha-helical peptides, varying in amphipathicity and the nature of side-chain substitutions in the centre of the hydrophobic or hydrophilic face. Observation of the retention behaviour of these amphipathic alpha-helical peptide analogues during HILIC/CEX and reversed-phase chromatography (RPLC) enabled the establishment of general rules concerning the applicability of these complementary HPLC techniques to peptides displaying a secondary structural motif of common occurrence.
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Affiliation(s)
- C T Mant
- Department of Biochemistry, University of Alberta, Edmonton, Canada
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28
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Dorsey JG, Cooper WT, Siles BA, Foley JP, Barth HG. Liquid Chromatography: Theory and Methodology. Anal Chem 1998. [DOI: 10.1021/a1980022h] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Affiliation(s)
- John G. Dorsey
- Department of Chemistry, Florida State University, Tallahassee, Florida 32306-4390
| | - William T. Cooper
- Department of Chemistry, Florida State University, Tallahassee, Florida 32306-4390
| | - Barbara A. Siles
- Department of Chemistry, College of William and Mary, Williamsburg, Virginia 23187-8795
| | - Joe P. Foley
- Department of Chemistry, Villanova University, Villanova, Pennsylvania 19085-1699
| | - Howard G. Barth
- Central Research and Development Department, E. I. du Pont de Nemours & Company, P.O. Box 80228, Experimental Station, Wilmington, Delaware 19880
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