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Bendová M, Heyda J, Wagner Z, Feder-Kubis J, Polák J, Tankam T, Sýkorová A. Aqueous solutions of chiral ionic liquids based on (–)-menthol: An experimental and computational study of volumetric and transport properties. J Mol Liq 2023. [DOI: 10.1016/j.molliq.2023.121591] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/21/2023]
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2
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Martínková E, Křížek T, Kubíčková A, Coufal P. Mobilization of electroosmotic flow markers in capillary zone electrophoresis. Electrophoresis 2021; 42:932-938. [PMID: 33570209 DOI: 10.1002/elps.202000301] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2020] [Revised: 02/05/2021] [Accepted: 02/05/2021] [Indexed: 11/11/2022]
Abstract
UV-absorbing neutral substances are commonly used as markers of mean electroosmotic flow in capillary electrophoresis for their zero electrophoretic mobility in an electric field. However, some of these markers can interact with background electrolyte components and migrate at a different velocity than the electroosmotic flow. Thus, we tested 11 markers primarily varying in their degree of methylation and type of central atom in combination with five background electrolyte cations differing in their ionic radii and surface charge density, measuring the relative electrophoretic mobility using thiourea as a reference marker. Our results from this set of experiments showed some general trends in the mobilization of the markers based on the effects of marker structure and type of background electrolyte cation on the relative electrophoretic mobility. As an example, the effects of an inadequate choice of marker on analyte identification were illustrated in the electrophoretic separation of glucosinolates. Therefore, our findings may help electrophoretists appropriately select electroosmotic flow markers for various electrophoretic systems.
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Affiliation(s)
- Eva Martínková
- Department of Analytical Chemistry, Faculty of Science, Charles University, Prague, Czech Republic
| | - Tomáš Křížek
- Department of Analytical Chemistry, Faculty of Science, Charles University, Prague, Czech Republic
| | - Anna Kubíčková
- Department of Analytical Chemistry, Faculty of Science, Charles University, Prague, Czech Republic
| | - Pavel Coufal
- Department of Analytical Chemistry, Faculty of Science, Charles University, Prague, Czech Republic
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3
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Liang D, Dahal U, Zhang YK, Lochbaum C, Ray D, Hamers RJ, Pedersen JA, Cui Q. Interfacial water and ion distribution determine ζ potential and binding affinity of nanoparticles to biomolecules. NANOSCALE 2020; 12:18106-18123. [PMID: 32852025 DOI: 10.1039/d0nr03792c] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
The molecular features that dictate interactions between functionalized nanoparticles and biomolecules are not well understood. This is in part because for highly charged nanoparticles in solution, establishing a clear connection between the molecular features of surface ligands and common experimental observables such as ζ potential requires going beyond the classical models based on continuum and mean field models. Motivated by these considerations, molecular dynamics simulations are used to probe the electrostatic properties of functionalized gold nanoparticles and their interaction with a charged peptide in salt solutions. Counterions are observed to screen the bare ligand charge to a significant degree even at the moderate salt concentration of 50 mM. As a result, the apparent charge density and ζ potential are largely insensitive to the bare ligand charge densities, which fall in the range of ligand densities typically measured experimentally for gold nanoparticles. While this screening effect was predicted by classical models such as the Manning condensation theory, the magnitudes of the apparent surface charge from microscopic simulations and mean-field models are significantly different. Moreover, our simulations found that the chemical features of the surface ligand (e.g., primary vs. quaternary amines, heterogeneous ligand lengths) modulate the interfacial ion and water distributions and therefore the interfacial potential. The importance of interfacial water is further highlighted by the observation that introducing a fraction of hydrophobic ligands enhances the strength of electrostatic binding of the charged peptide. Finally, the simulations highlight that the electric double layer is perturbed upon binding interactions. As a result, it is the bare charge density rather than the apparent charge density or ζ potential that better correlates with binding affinity of the nanoparticle to a charged peptide. Overall, our study highlights the importance of molecular features of the nanoparticle/water interface and underscores a set of design rules for the modulation of electrostatic driven interactions at nano/bio interfaces.
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Affiliation(s)
- Dongyue Liang
- Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, WI 53706, USA
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4
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Duboué-Dijon E, Delcroix P, Martinez-Seara H, Hladílková J, Coufal P, Křížek T, Jungwirth P. Binding of Divalent Cations to Insulin: Capillary Electrophoresis and Molecular Simulations. J Phys Chem B 2018; 122:5640-5648. [PMID: 29360367 DOI: 10.1021/acs.jpcb.7b12097] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
In the present study, we characterize the binding of divalent cations to insulin in aqueous salt solutions by means of capillary electrophoresis and molecular dynamics simulations. The results show a strong pH dependence. At low pH, at which all the carboxylate groups are protonated and the protein has an overall positive charge, all the cations exhibit only weak and rather unspecific interactions with insulin. In contrast, at close to neutral pH, when all the carboxylate groups are deprotonated and negatively charged, the charge-neutralizing effect of magnesium, calcium, and zinc, in particular, on the electrophoretic mobility of insulin is significant. This is also reflected in the results of molecular dynamics simulations showing accumulation of cations at the protein surface, which becomes smaller in magnitude upon effective inclusion of electronic polarization via charge rescaling.
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Affiliation(s)
- Elise Duboué-Dijon
- Institute of Organic Chemistry and Biochemistry , Czech Academy of Sciences , Flemingovo nám. 542/2 , 160 00 Prague , Czech Republic
| | - Pauline Delcroix
- Institute of Organic Chemistry and Biochemistry , Czech Academy of Sciences , Flemingovo nám. 542/2 , 160 00 Prague , Czech Republic.,J. Heyrovský Institute of Physical Chemistry , Czech Academy of Sciences , v.v.i, Dolejškova 2155/3 , 182 23 Prague 8 , Czech Republic
| | - Hector Martinez-Seara
- Institute of Organic Chemistry and Biochemistry , Czech Academy of Sciences , Flemingovo nám. 542/2 , 160 00 Prague , Czech Republic
| | - Jana Hladílková
- Division of Theoretical Chemistry , Lund University , POB 124, SE-22100 Lund , Sweden
| | - Pavel Coufal
- Department of Analytical Chemistry , Faculty of Science, Charles University in Prague , Albertov 2030 , 12840 Prague 2 , Czech Republic
| | - Tomáš Křížek
- Department of Analytical Chemistry , Faculty of Science, Charles University in Prague , Albertov 2030 , 12840 Prague 2 , Czech Republic
| | - Pavel Jungwirth
- Institute of Organic Chemistry and Biochemistry , Czech Academy of Sciences , Flemingovo nám. 542/2 , 160 00 Prague , Czech Republic
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5
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Self-association of a highly charged arginine-rich cell-penetrating peptide. Proc Natl Acad Sci U S A 2017; 114:11428-11433. [PMID: 29073067 DOI: 10.1073/pnas.1712078114] [Citation(s) in RCA: 50] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Small-angle X-ray scattering (SAXS) measurements reveal a striking difference in intermolecular interactions between two short highly charged peptides-deca-arginine (R10) and deca-lysine (K10). Comparison of SAXS curves at high and low salt concentration shows that R10 self-associates, while interactions between K10 chains are purely repulsive. The self-association of R10 is stronger at lower ionic strengths, indicating that the attraction between R10 molecules has an important electrostatic component. SAXS data are complemented by NMR measurements and potentials of mean force between the peptides, calculated by means of umbrella-sampling molecular dynamics (MD) simulations. All-atom MD simulations elucidate the origin of the R10-R10 attraction by providing structural information on the dimeric state. The last two C-terminal residues of R10 constitute an adhesive patch formed by stacking of the side chains of two arginine residues and by salt bridges formed between the like-charge ion pair and the C-terminal carboxyl groups. A statistical analysis of the Protein Data Bank reveals that this mode of interaction is a common feature in proteins.
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6
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Kašička V. Recent developments in capillary and microchip electroseparations of peptides (2013-middle 2015). Electrophoresis 2015; 37:162-88. [DOI: 10.1002/elps.201500329] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2015] [Revised: 08/25/2015] [Accepted: 08/25/2015] [Indexed: 12/16/2022]
Affiliation(s)
- Václav Kašička
- Institute of Organic Chemistry and Biochemistry, v.v.i; The Czech Academy of Sciences; Prague Czech Republic
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7
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Roberts D, Keeling R, Tracka M, van der Walle CF, Uddin S, Warwicker J, Curtis R. Specific Ion and Buffer Effects on Protein–Protein Interactions of a Monoclonal Antibody. Mol Pharm 2014; 12:179-93. [DOI: 10.1021/mp500533c] [Citation(s) in RCA: 109] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- D. Roberts
- School
of Chemical Engineering and Analytical Science, The University of Manchester, Sackville Street, Manchester M13 9PL, U.K
| | - R. Keeling
- School
of Chemical Engineering and Analytical Science, The University of Manchester, Sackville Street, Manchester M13 9PL, U.K
| | - M. Tracka
- Formulation
Sciences, MedImmune, Ltd., Aaron Klug Building, Granta Park, Cambridge CB21 6GH, U.K
| | - C. F. van der Walle
- Formulation
Sciences, MedImmune, Ltd., Aaron Klug Building, Granta Park, Cambridge CB21 6GH, U.K
| | - S. Uddin
- Formulation
Sciences, MedImmune, Ltd., Aaron Klug Building, Granta Park, Cambridge CB21 6GH, U.K
| | - J. Warwicker
- School
of Chemical Engineering and Analytical Science, The University of Manchester, Sackville Street, Manchester M13 9PL, U.K
| | - R. Curtis
- School
of Chemical Engineering and Analytical Science, The University of Manchester, Sackville Street, Manchester M13 9PL, U.K
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Allison SA, Wu H, Bui TM, Dang L, Huynh GH, Nguyen T, Soegiarto L, Truong BC. Specific ion effects on the electrophoretic mobility of small, highly charged peptides: A modeling study. J Sep Sci 2014; 37:2403-10. [DOI: 10.1002/jssc.201400484] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2014] [Revised: 06/09/2014] [Accepted: 06/10/2014] [Indexed: 11/08/2022]
Affiliation(s)
| | - Hengfu Wu
- Department of Chemistry; Georgia State University; Atlanta GA USA
| | - Tuyen M. Bui
- Department of Chemistry; Georgia State University; Atlanta GA USA
| | - Lac Dang
- Department of Chemistry; Georgia State University; Atlanta GA USA
| | - Giang H. Huynh
- Department of Chemistry; Georgia State University; Atlanta GA USA
| | - Tam Nguyen
- Department of Chemistry; Georgia State University; Atlanta GA USA
| | - Linda Soegiarto
- Department of Chemistry; Georgia State University; Atlanta GA USA
| | - Bi C. Truong
- Department of Chemistry; Georgia State University; Atlanta GA USA
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Stellwagen NC, Peters JP, Dong Q, Maher LJ, Stellwagen E. The free solution mobility of DNA and other analytes varies as the logarithm of the fractional negative charge. Electrophoresis 2014; 35:1855-63. [PMID: 24648187 DOI: 10.1002/elps.201400040] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2014] [Revised: 03/10/2014] [Accepted: 03/12/2014] [Indexed: 11/09/2022]
Abstract
The free solution mobilities of ssDNA and dsDNA molecules with variable charge densities have been measured by CE. DNA charge density was modified either by appending positively or negatively charged groups to the thymine residues in a 98 bp DNA molecule, or by replacing some of the negatively charged phosphate internucleoside linkers in small ssDNA or dsDNA oligomers with positively charged phosphoramidate linkers. Mobility ratios were calculated for each dataset by dividing the mobility of a charge variant by the mobility of its unmodified parent DNA. Mobility ratios essentially eliminate the effect of the BGE on the observed mobility, making it possible to compare analytes measured under different experimental conditions. Neutral moieties attached to the thymine residues in the 98-bp DNA molecule had little or no effect on the mobility ratios, indicating that bulky substituents in the DNA major groove do not affect the mobility significantly. The mobility ratios observed for the thymine-modified and linker-modified DNA charge variants increased approximately linearly with the logarithm of the fractional negative charge of the DNA. Mobility ratios calculated from previous studies of linker-modified DNA charge variants and small multicharged organic molecules also increased approximately linearly with the logarithm of the fractional negative charge of the analyte. The results do not agree with the Debye-Hückel-Onsager theory of electrophoresis, which predicts that the mobility of an analyte should depend linearly on analyte charge, not the logarithm of the charge, when the frictional coefficient is held constant.
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Křížek T, Kubíčková A, Hladílková J, Coufal P, Heyda J, Jungwirth P. Electrophoretic mobilities of neutral analytes and electroosmotic flow markers in aqueous solutions of Hofmeister salts. Electrophoresis 2014; 35:617-24. [PMID: 24338984 DOI: 10.1002/elps.201300544] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2013] [Revised: 11/29/2013] [Accepted: 11/29/2013] [Indexed: 11/07/2022]
Abstract
Small neutral organic compounds have traditionally the role of EOF markers in electrophoresis, as they are expected to have zero electrophoretic mobility in external electric fields. The BGE contains, however, ions that have unequal affinities to the neutral molecules, which in turn results in their mobilization. In this study we focused on two EOF markers-thiourea and DMSO, as well as on N-methyl acetamide (NMA) as a model of the peptide bond. By means of CE and all atom molecular dynamics simulations we explored mobilization of these neutral compounds in large set of Hofmeister salts. Employing a statistical mechanics approach, we were able to reproduce by simulations the experimental electrophoretic mobility coefficients. We also established the role of the chemical composition of marker and the BGE on the measured electrophoretic mobility coefficient. For NMA, we interpreted the results in terms of the relative affinities of cations versus anions to the peptide bond.
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Affiliation(s)
- Tomáš Křížek
- Department of Analytical Chemistry, Faculty of Science, Charles University in Prague, Prague, Czech Republic
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11
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Kašička V. Recent developments in capillary and microchip electroseparations of peptides (2011-2013). Electrophoresis 2013; 35:69-95. [PMID: 24255019 DOI: 10.1002/elps.201300331] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2013] [Revised: 09/10/2013] [Accepted: 09/10/2013] [Indexed: 01/15/2023]
Abstract
The review presents a comprehensive survey of recent developments and applications of capillary and microchip electroseparation methods (zone electrophoresis, ITP, IEF, affinity electrophoresis, EKC, and electrochromatography) for analysis, isolation, purification, and physicochemical and biochemical characterization of peptides. Advances in the investigation of electromigration properties of peptides, in the methodology of their analysis, including sample preseparation, preconcentration and derivatization, adsorption suppression and EOF control, as well as in detection of peptides, are presented. New developments in particular CE and CEC modes are reported and several types of their applications to peptide analysis are described: conventional qualitative and quantitative analysis, determination in complex (bio)matrices, monitoring of chemical and enzymatical reactions and physical changes, amino acid, sequence and chiral analysis, and peptide mapping of proteins. Some micropreparative peptide separations are shown and capabilities of CE and CEC techniques to provide relevant physicochemical characteristics of peptides are demonstrated.
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Affiliation(s)
- Václav Kašička
- Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Prague, Czech Republic
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Gurnev PA, Bezrukov SM. Inversion of membrane surface charge by trivalent cations probed with a cation-selective channel. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2012; 28:15824-30. [PMID: 23088396 PMCID: PMC4307797 DOI: 10.1021/la302676t] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
We demonstrate that the cation-selective channel formed by gramicidin A can be used as a reliable sensor for studying the multivalent ion accumulation at the surfaces of charged lipid membranes and the "charge inversion" phenomenon. In asymmetrically charged membranes with the individual leaflets formed from pure negative and positive lipids bathed by 0.1 M CsCl solutions the channel exhibits current rectification, which is comparable to that of a typical n/p semiconductor diode. We show that even at these highly asymmetrical conditions the channel conductance can be satisfactorily described by the electrodiffusion equation in the constant field approximation but, due to predictable limitations, only when the applied voltages do not exceed 50 mV. Analysis of the changes in the voltage-dependent channel conductance upon addition of trivalent cations allows us to gauge their interactions with the membrane surface. The inversion of the sign of the effective surface charge takes place at the concentrations, which correlate with the cation size. Specifically, these concentrations are close to 0.05 mM for lanthanum, 0.25 mM for hexaamminecobalt, and 4 mM for spermidine.
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Affiliation(s)
- Philip A Gurnev
- Program in Physical Biology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, United States.
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Kubíčková A, Křížek T, Coufal P, Vazdar M, Wernersson E, Heyda J, Jungwirth P. Overcharging in biological systems: reversal of electrophoretic mobility of aqueous polyaspartate by multivalent cations. PHYSICAL REVIEW LETTERS 2012; 108:186101. [PMID: 22681091 DOI: 10.1103/physrevlett.108.186101] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/18/2012] [Indexed: 06/01/2023]
Abstract
Charge reversal as an extreme case of charge compensation is directly observed by capillary electrophoresis for a negatively charged peptide in aqueous solutions of trivalent cations. Atomistic and coarse-grained simulations provide molecular interpretation of this effect showing that it is largely of electrostatic origin with a minor contribution of chemical specificity of the salt ions.
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Affiliation(s)
- Anna Kubíčková
- Charles University in Prague, Faculty of Science, Department of Analytical Chemistry, Albertov 2030, 12840 Prague 2, Czech Republic
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