1
|
Bílek J, Koval D, Šolínová V, Talele HL, Severa L, Gutiérrez PER, Teplý F, Kašička V. Determination of the binding constants and ionic mobilities of diquat complexes with randomly sulfated cyclodextrins by affinity capillary electrophoresis. J Sep Sci 2024; 47:e2400286. [PMID: 38863086 DOI: 10.1002/jssc.202400286] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2024] [Revised: 05/16/2024] [Accepted: 05/19/2024] [Indexed: 06/13/2024]
Abstract
The enantiomers of diquats (DQs), a new class of functional organic molecules, were recently separated by capillary electrophoresis (CE) with high resolution up to 11.4 within 5-7 min using randomly sulfated α-, β-, and γ-cyclodextrins (CDs) as chiral selectors. These results indicated strong interactions between dicationic diquats and multiply negatively charged sulfated CDs (S-CDs). However, the binding strength of these interactions was not quantified. For that reason, in this study, affinity CE was applied for the determination of the binding constants and ionic mobilities of the complexes of DQ P- and M-enantiomers with CD chiral selectors in an aqueous medium. The non-covalent interactions of 10 pairs of DQ enantiomers with the above CDs were investigated in a background electrolyte (BGE) composed of 22 mM NaOH, 35 mM H3PO4, pH 2.5, and 0.0-1.0 mM concentrations of CDs. The average apparent binding constant and the average actual ionic mobility of the DQ-CD complexes were determined by nonlinear regression analysis of the dependence of the effective mobility of DQ enantiomers on the concentration of CDs in the BGE. The complexes were found to be relatively strong with the averaged apparent binding constants in the range 13 600-547 400 L/mol.
Collapse
Affiliation(s)
- Jan Bílek
- Electromigration Methods, Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Prague 6, Czechia
| | - Dušan Koval
- Electromigration Methods, Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Prague 6, Czechia
| | - Veronika Šolínová
- Electromigration Methods, Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Prague 6, Czechia
| | - Harish L Talele
- Electromigration Methods, Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Prague 6, Czechia
| | - Lukáš Severa
- Electromigration Methods, Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Prague 6, Czechia
| | - Paul E Reyes Gutiérrez
- Electromigration Methods, Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Prague 6, Czechia
| | - Filip Teplý
- Electromigration Methods, Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Prague 6, Czechia
| | - Václav Kašička
- Electromigration Methods, Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Prague 6, Czechia
| |
Collapse
|
2
|
Šolínová V, Štěpánová S, Jančařík A, Klívar J, Šámal M, Stará IG, Chocholoušová JV, Vacek J, Starý I, Kašička V. Nonaqueous capillary electrophoresis and quantum chemical calculations applied to investigation of acid-base and electromigration properties of azahelicenes. Electrophoresis 2021; 43:696-707. [PMID: 34933403 DOI: 10.1002/elps.202100331] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2021] [Revised: 12/06/2021] [Accepted: 12/16/2021] [Indexed: 11/07/2022]
Abstract
Nonaqueous capillary electrophoresis (NACE) using methanol (MeOH) as a solvent of the BGEs and quantum mechanical density functional theory (DFT) have been applied to determine the thermodynamic acidity (ionization) constants (pKa ) of mono- and diaza[5]helicenes, mono- and diaza[6]helicenes, and their dibenzo derivatives in MeOH and water. First, the mixed acidity constants, p K a , MeOH mix , of ionogenic pyridinium groups of azahelicenes and their derivatives in MeOH were obtained by nonlinear regression analysis of pH dependence of their effective electrophoretic mobilities. The effective mobilities were measured by NACE in a large series of methanolic BGEs within a wide conventional pH range (pHMeOH 1.6-12.0) and at ambient temperature (21-26°C) in a home-made CE device. Prior to mixed acidity constant calculation, the effective mobilities were corrected to reference temperature (25°C) and constant ionic strength (25 mM). Then, the mixed acidity constants were recalculated to the thermodynamic acidity constants pKa,MeOH by the Debye-Hückel theory of nonideality of electrolyte solutions. Finally, from the methanolic thermodynamic pKa,MeOH values, the aqueous thermodynamic p K a , H 2 O constants were estimated using the empirical relations between methanolic and aqueous acidity constants derived for structurally related pyridine derivatives. Depending on the number and position of the nitrogen atoms in their molecules, the analyzed azahelicenes were found to be weak to moderate bases with methanolic pKa,MeOH in the range 2.01-8.75 and with aqueous p K a , H 2 O in the range 1.67-8.28. The thermodynamic pKa,MeOH obtained by the DFT calculations were in a good agreement with those determined experimentally by NACE.
Collapse
Affiliation(s)
- Veronika Šolínová
- Institute of Organic Chemistry and Biochemistry, The Czech Academy of Sciences, Czech Republic
| | - Sille Štěpánová
- Institute of Organic Chemistry and Biochemistry, The Czech Academy of Sciences, Czech Republic
| | - Andrej Jančařík
- Institute of Organic Chemistry and Biochemistry, The Czech Academy of Sciences, Czech Republic
| | - Jiří Klívar
- Institute of Organic Chemistry and Biochemistry, The Czech Academy of Sciences, Czech Republic
| | - Michal Šámal
- Institute of Organic Chemistry and Biochemistry, The Czech Academy of Sciences, Czech Republic
| | - Irena G Stará
- Institute of Organic Chemistry and Biochemistry, The Czech Academy of Sciences, Czech Republic
| | | | - Jaroslav Vacek
- Institute of Organic Chemistry and Biochemistry, The Czech Academy of Sciences, Czech Republic
| | - Ivo Starý
- Institute of Organic Chemistry and Biochemistry, The Czech Academy of Sciences, Czech Republic
| | - Václav Kašička
- Institute of Organic Chemistry and Biochemistry, The Czech Academy of Sciences, Czech Republic
| |
Collapse
|
3
|
Lebanov L, Fuguet E, Melo JM, Rosés M. Determination of acidity constants at 37 °C through the internal standard capillary electrophoresis (IS-CE) method: internal standards and application to polyprotic drugs. Analyst 2020; 145:5897-5904. [PMID: 32671360 DOI: 10.1039/d0an00918k] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
This work provides the pKa at the biorelevant temperature of 37 °C for a set of compounds proposed as internal standards for the internal standard capillary electrophoresis (IS-CE) method. This is a high throughput method that allows the determination of the acidity constants of compounds in a short time, avoiding the exact measurement of the pH of the buffers used. pH electrode calibration at 37 °C can be avoided too. In order to anchor the pKa values obtained through the IS-CE method in the pH scale, the acidity constant at 37 °C of some of the standards has been determined also by the reference potentiometric method. In general, a decrease in the pKa value is observed when changing the temperature from 25 to 37 °C, and the magnitude of the change depends on the nature of the compounds. Once the pKa values at 37 °C of the internal standards have been established, the method is applied to the determination of the acidity constants of seven polyprotic (5 diprotic and 2 triprotic) drugs. The obtained mobility-pH profiles show well-defined curves, and the fits provide precise pKa values. Due to the lack of reference data at 37 °C only the pKa values of labetalol can be compared to values from the literature, and a very good agreement is observed.
Collapse
Affiliation(s)
- Leo Lebanov
- Departament d'Enginyeria Química i Química Analítica and Institut de Biomedicina (IBUB), Universitat de Barcelona, Martí I Franquès 1-11, 08028, Barcelona, Spain.
| | | | | | | |
Collapse
|
4
|
Determination of thermodynamic binding constants by affinity capillary electrophoresis. Talanta 2018; 192:448-454. [PMID: 30348416 DOI: 10.1016/j.talanta.2018.09.044] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2018] [Revised: 09/03/2018] [Accepted: 09/13/2018] [Indexed: 11/24/2022]
Abstract
A strategy to study thermodynamic binding constants by affinity capillary electrophoresis (ACE) is presented. In order to simplify mathematical treatment, analogy with acid-base dissociation equilibrium is proposed: instead of ligand concentration [X], negative logarithm of ligand concentration (or activity), pX = -log[X], is used. On this base, and taking into account ionic activities, a general procedure for obtaining thermodynamic binding constants is proposed. In addition, the method provides electrophoretic mobilities of the free analyte and analyte-ligand complex, even when binding constants are low and thus, the complexed analyte fraction is also low. This is useful as a base to rationally analyze a diversity of situations, i.e., different mathematical dependencies are obtained when analytes and ligands with different charges are combined. Practical considerations are given for carrying out a full experimental design. Enantiomeric ACE separation based on the use of chiral selectors is addressed. 2-hydroxypropyl-β-cyclodextrin was chosen as a model ligand, and both enantiomeric forms of four pharmaceutical drugs (propranolol, pindolol, oxprenolol and homatropine methylbromide) were considered as model analytes. Practical aspects are detailed and thermodynamic binding constants as well as free and complexed analytes mobilities are determined.
Collapse
|
5
|
Sázelová P, Koval D, Severa L, Teplý F, Kašička V. Chiral analysis of α-diimine Ru(II) and Fe(II) complexes by capillary electrophoresis using sulfated cyclodextrins as stereoselectors. Electrophoresis 2017; 38:1913-1921. [DOI: 10.1002/elps.201700077] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2017] [Revised: 04/13/2017] [Accepted: 04/13/2017] [Indexed: 12/19/2022]
Affiliation(s)
- Petra Sázelová
- Institute of Organic Chemistry and Biochemistry; Czech Academy of Sciences; Prague Czech Republic
| | - Dušan Koval
- Institute of Organic Chemistry and Biochemistry; Czech Academy of Sciences; Prague Czech Republic
| | - Lukáš Severa
- Institute of Organic Chemistry and Biochemistry; Czech Academy of Sciences; Prague Czech Republic
| | - Filip Teplý
- Institute of Organic Chemistry and Biochemistry; Czech Academy of Sciences; Prague Czech Republic
| | - Václav Kašička
- Institute of Organic Chemistry and Biochemistry; Czech Academy of Sciences; Prague Czech Republic
| |
Collapse
|
6
|
Hlaváček J, Vítovcová M, Sázelová P, Pícha J, Vaněk V, Buděšínský M, Jiráček J, Gillner DM, Holz RC, Mikšík I, Kašička V. Mono-N-acyl-2,6-diaminopimelic acid derivatives: Analysis by electromigration and spectroscopic methods and examination of enzyme inhibitory activity. Anal Biochem 2014; 467:4-13. [DOI: 10.1016/j.ab.2014.08.032] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2014] [Revised: 08/15/2014] [Accepted: 08/26/2014] [Indexed: 10/24/2022]
|
7
|
Wang JL, Xu XJ, Chen DY. Determination of pKa values of a triptolide derivative and its impurities by pressure-assisted capillary electrophoresis. J Pharm Biomed Anal 2014; 88:22-6. [DOI: 10.1016/j.jpba.2013.08.012] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2013] [Revised: 08/06/2013] [Accepted: 08/08/2013] [Indexed: 11/25/2022]
|
8
|
Šolínová V, Kašička V. Determination of acidity constants and ionic mobilities of polyprotic peptide hormones by CZE. Electrophoresis 2013; 34:2655-65. [PMID: 23775856 DOI: 10.1002/elps.201300119] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2013] [Revised: 04/23/2013] [Accepted: 04/23/2013] [Indexed: 12/16/2022]
Abstract
CZE has been applied to determination of thermodynamic acidity constants (pKa ) of ionogenic groups and actual ionic mobilities of polyprotic peptides-synthetic human and salmon gonadotropin-releasing hormones and their derivatives and fragments. First, the mixed acidity constants, pKa,imix, of ionogenic groups, and actual ionic mobilities, mi , of gonadotropin-releasing hormone peptides were determined by nonlinear regression analysis of pH dependence of their effective electrophoretic mobilities. The effective mobilities were measured by CZE in a series of BGEs within a broad pH range (1.80-12.10), at constant ionic strength (25 mM) and reference temperature (25°C). Second, the pKa,imix values were recalculated to thermodynamic pKa s using the Debye-Hückel theory. Thermodynamic pKa of carboxyl groups was estimated to be in the range of 2.5-3.3 for C-terminal amino acids of the above peptides, and 5.2 for glutamic acid in the middle of peptide chain; pKa of imidazolyl group of histidine residues was in the range of 5.7-6.8, pKa of N-terminal amino group of the peptide with free N-terminus was equal to 6.2, pKa of phenol group of tyrosine residues was in the range of 9.8-10.8, and pKa of guanidinyl group or arginine residues reached values 11.1-11.3, depending on the position of the residues in the peptide and on the amino acid sequence of the peptide. Absolute values of actual ionic mobilities of peptides with charge number ±2 were in the range (14.6-18.6) × 10(-9) m(2) V(-1) s(-1) , and ionic mobilities of peptides with charge number ±1 reached values (6.5-12.9) × 10(-9) m(2) V(-1) s(-1) .
Collapse
Affiliation(s)
- Veronika Šolínová
- Institute of Organic Chemistry and Biochemistry, v.v.i., Academy of Sciences of the Czech Republic, Prague, Czech Republic
| | | |
Collapse
|
9
|
Ren H, Wang L, Wang X, Liu X, Jiang S. Measurement of acid dissociation constants and ionic mobilities of 3-nitro-tyrosine and 3-chloro-tyrosine by capillary zone electrophoresis. J Pharm Biomed Anal 2013; 77:83-7. [DOI: 10.1016/j.jpba.2013.01.015] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2012] [Revised: 01/07/2013] [Accepted: 01/07/2013] [Indexed: 10/27/2022]
|
10
|
Šolínová V, Poitevin M, Koval D, Busnel JM, Peltre G, Kašička V. Capillary electrophoresis in classical and carrier ampholytes-based background electrolytes applied to separation and characterization of gonadotropin-releasing hormones. J Chromatogr A 2012; 1267:231-8. [DOI: 10.1016/j.chroma.2012.07.059] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2012] [Revised: 07/16/2012] [Accepted: 07/19/2012] [Indexed: 10/28/2022]
|
11
|
Capillary electrophoretic profiling of tryptic digests of water soluble proteins from Bacillus thuringiensis-transgenic and non-transgenic maize species. Food Chem 2012; 134:1607-15. [DOI: 10.1016/j.foodchem.2012.02.220] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2010] [Revised: 02/27/2012] [Accepted: 02/28/2012] [Indexed: 11/22/2022]
|
12
|
Ehala S, Grishina AA, Sheshenev AE, Lyapkalo IM, Kašička V. Determination of acid–base dissociation constants of very weak zwitterionic heterocyclic bases by capillary zone electrophoresis. J Chromatogr A 2010; 1217:8048-53. [DOI: 10.1016/j.chroma.2010.08.077] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2010] [Revised: 08/25/2010] [Accepted: 08/26/2010] [Indexed: 10/19/2022]
|
13
|
|
14
|
Sázelová P, Kašička V, Ibáñez E, Cifuentes A. Extraction and separation of water-soluble proteins fromBacillus thuringiensis-transgenic and non-transgenic maize species by CZE. J Sep Sci 2009; 32:3801-8. [DOI: 10.1002/jssc.200900448] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
|
15
|
Vanek V, Budesínský M, Kabeleová P, Sanda M, Kozísek M, Hanclová I, Mládková J, Brynda J, Rosenberg I, Koutmos M, Garrow TA, Jirácek J. Structure-activity study of new inhibitors of human betaine-homocysteine S-methyltransferase. J Med Chem 2009; 52:3652-65. [PMID: 19534555 DOI: 10.1021/jm8015798] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Betaine-homocysteine S-methyltransferase (BHMT) catalyzes the transfer of a methyl group from betaine to l-homocysteine, yielding dimethylglycine and l-methionine. In this study, we prepared a new series of BHMT inhibitors. The inhibitors were designed to mimic the hypothetical transition state of BHMT substrates and consisted of analogues with NH, N(CH(3)), or N(CH(3))(2) groups separated from the homocysteine sulfur atom by a methylene, ethylene, or a propylene spacer. Only the inhibitor with the N(CH(3)) moiety and ethylene spacer gave moderate inhibition. This result led us to prepare two inhibitors lacking a nitrogen atom in the S-linked alkyl chain: (RS,RS)-5-(3-amino-3-carboxypropylthio)-3-methylpentanoic acid and (RS)-5-(3-amino-3-carboxypropylthio)-3,3-dimethylpentanoic acid. Both of these compounds were highly potent inhibitors of BHMT. The finding that BHMT does not tolerate a true betaine mimic within these inhibitors, especially the nitrogen atom, is surprising and evokes questions about putative conformational changes of BHMT upon the binding of the substrates/products and inhibitors.
Collapse
Affiliation(s)
- Václav Vanek
- Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, v.v.i., Flemingovo nam. 2, 166 10 Prague 6, Czech Republic
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
16
|
Jerez G, Kaufman G, Prystai M, Schenkeveld S, Donkor KK. Determination of thermodynamic pKavalues of benzimidazole and benzimidazole derivatives by capillary electrophoresis. J Sep Sci 2009; 32:1087-95. [DOI: 10.1002/jssc.200800482] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
|
17
|
Šlampová A, Křivánková L, Gebauer P, Boček P. Standard systems for measurement of pKs and ionic mobilities. J Chromatogr A 2008; 1213:25-30. [DOI: 10.1016/j.chroma.2008.08.101] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2008] [Revised: 08/26/2008] [Accepted: 08/29/2008] [Indexed: 11/29/2022]
|
18
|
Koval D, Busnel J, Hlaváček J, Jiráček J, Kašička V, Peltre G. Evaluation of carrier ampholyte‐based capillary electrophoresis for separation of peptides and peptide mimetics. Electrophoresis 2008; 29:3759-67. [DOI: 10.1002/elps.200800193] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Dušan Koval
- Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Prague, Czech Republic
| | - Jean‐Marc Busnel
- Laboratoire Environnement et Chimie and Analytique, Ecole Supérieure de Physique et Chimie Industrielles, Paris, France
- Laboratoire d'Electrochimie Physique et Analytique, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
| | - Jan Hlaváček
- Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Prague, Czech Republic
| | - Jiří Jiráček
- Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Prague, Czech Republic
| | - Václav Kašička
- Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Prague, Czech Republic
| | - Gabriel Peltre
- Laboratoire Environnement et Chimie and Analytique, Ecole Supérieure de Physique et Chimie Industrielles, Paris, France
| |
Collapse
|
19
|
Šlampová A, Boček P. Statistical evaluation of mobility curves of univalent weak acids. Electrophoresis 2008; 29:1196-9. [DOI: 10.1002/elps.200700621] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
|
20
|
Šlampová A, Boček P. Statistical data processing of mobility curves of univalent weak bases. Electrophoresis 2008; 29:538-41. [DOI: 10.1002/elps.200700524] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
|
21
|
Solínová V, Kasicka V, Sázelová P, Barth T, Miksík I. Separation and investigation of structure–mobility relationship of gonadotropin-releasing hormones by capillary zone electrophoresis in conventional and isoelectric acidic background electrolytes. J Chromatogr A 2007; 1155:146-53. [PMID: 17229433 DOI: 10.1016/j.chroma.2007.01.019] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2006] [Revised: 12/22/2006] [Accepted: 01/05/2007] [Indexed: 11/25/2022]
Abstract
Capillary zone electrophoresis (CZE) has been applied to qualitative and quantitative analysis, separation and physicochemical characterization of synthetic gonadotropin-releasing hormones (GnRHs) and their analogs and fragments. Structurally related peptides were separated in conventional and isoelectric acidic background electrolytes (BGEs), pH 2.18-2.50. Best separation was achieved in isoelectric BGE composed of 200 mM iminodiacetic acid, pH 2.32. The effective electrophoretic mobilities, m(ep), of GnRHs in five BGEs were determined and four semiempirical models correlating effective mobility with charge, q, and relative molecular mass, M(r), (m(ep) versus q/M(r)(k), where k is related to the molecular shape) were tested to describe the migration behavior of GnRHs in CZE. None of the models was found to be quite definitively applicable for the whole set of 10 GnRHs differing in size (tetrapeptide-decapeptide) and positive charge (0.91-3.00 elementary charges). Nevertheless, for the dependence of m(ep) on q/M(r)(k), the highest coefficient of correlation, R=0.995-0.999, was obtained for k close to the value 0.5 in all five acidic BGEs. This indicates that the most probable structure of GnRHs in these BGEs can be predicted as a random coil.
Collapse
Affiliation(s)
- Veronika Solínová
- Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Flemingovo 2, 166 10 Prague 6, Czech Republic
| | | | | | | | | |
Collapse
|
22
|
Lisková A, Slampová A. Measurement of pKa values of newly synthesized heteroarylaminoethanols by CZE. Eur J Pharm Sci 2007; 30:375-9. [PMID: 17289356 DOI: 10.1016/j.ejps.2006.12.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2006] [Revised: 12/20/2006] [Accepted: 12/27/2006] [Indexed: 11/26/2022]
Abstract
Heteroarylaminoethanol derivates are drugs which affect sympathetic nervous system and are used for medications of hypertension. In solutions they behave like weak bases and their pK(a) values represent important information on their potential biological uptake, pharmacological activity and in vivo biodisponsibility. This article brings the measurement of pK(a) values of the series of seven new important heteroarylaminoethanols, compounds with potential vasodilating, beta-adrenolytic and antioxidant activity, by capillary zone electrophoresis (CZE) with diode-array detection. It has been shown that capillary zone electrophoresis measurements of pK(a) can be easily performed with very small quantities of studied substances, and, due to CZE separation power, the purity of samples is not of key importance. Moreover, the CZE method is fast and reliable, providing that suitable operational conditions are selected. The method is based on the measurement of the effective mobility curves within a suitable pH range and related regression analysis where pK(BH)(+) and electrophoretic mobility of BH(+) are explicitly involved. The selection of sufficient operational buffers is of key importance for accurate and reproducible results, and, this article brings step by step the consideration procedure involved in this process. Further, this paper brings principles of least square regression analysis of non-linear function corresponding to exact explicit formula for mobility curve of monovalent weak base.
Collapse
Affiliation(s)
- Anna Lisková
- Department of Chemical Drugs, Faculty of Pharmacy, University of Veterinary and Pharmaceutical Sciences Brno, Brno, Czech Republic.
| | | |
Collapse
|
23
|
Koval D, Kasicka V, Jirácek J, Collinsová M. Determination of pKa values of diastereomers of phosphinic pseudopeptides by CZE. Electrophoresis 2006; 27:4648-57. [PMID: 17080488 DOI: 10.1002/elps.200600133] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
A CE method was used for the determination of acidity constants (pK(a)) of a series of ten phosphinic pseudopeptides, which varied in number and type of ionogenic groups. Effective electrophoretic mobilities were measured in the 1.8-12.0 pH range in the BGEs of constant ionic strength of 25 mM. Effective electrophoretic mobilities, corrected to standard temperature of 25 degrees C, were subjected to non-linear regression analysis and the obtained apparent pK(a) values were recalculated to thermodynamic pK(a)'s by extrapolation to zero ionic strength according to the extended Debye-Hückel model. The pK(a) values of the phosphinic acid group fell typically in the 1.5-2.25 interval, C-terminal carboxylic groups in the 2.94-3.50 interval, carboxylic groups of the lateral chain of glutamate and aspartate in the 4.68-4.97 interval, imidazolyl moiety of histidine in the 6.55-8.32 interval, N-terminal amino groups in the 7.65-8.28 interval and epsilon-amino group of the lateral chain of lysine in the 10.46-10.61 interval. Further, separation of diastereomers of the phosphinic pseudopeptides was investigated in achiral BGEs. Evaluation of the resolution of the diastereomers as a function of pH of the BGE revealed that most suitable pH region for separation of the diastereomers is around the pK(a) values of the central phosphinic acid group of the pseudopeptides. Successful separation of some diastereomers was, however, achieved in the neutral and alkaline BGEs as well.
Collapse
Affiliation(s)
- Dusan Koval
- Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Prague, Czech Republic
| | | | | | | |
Collapse
|
24
|
Preinerstorfer B, Lubda D, Mucha A, Kafarski P, Lindner W, Lämmerhofer M. Stereoselective separations of chiral phosphinic acid pseudodipeptides by CEC using silica monoliths modified with an anion-exchange-type chiral selector. Electrophoresis 2006; 27:4312-20. [PMID: 17006883 DOI: 10.1002/elps.200600253] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
A nonaqueous CEC method for the simultaneous separation of the four stereoisomers of the N-benzyloxycarbonyl phosphinic pseudodipeptide methyl ester benzyloxycarbonyl-homophenylalanine Z-hPhepsi(PO2HCH2)Phe-OCH3 as well as of the corresponding N-2,4-dinitrophenyl (DNP)-derivative with free C-terminal carboxylic group DNP-hPhepsi(PO2HCH2)Phe-OH was developed. For this purpose, a monolithic silica capillary column modified with a cinchona alkaloid-derived anion-exchange-type chiral selector, namely O-9-(tert-butylcarbamoyl)quinidine (tBuCQD) was prepared. The mobile phase composition (ACN/methanol ratio, counterion type) was thoroughly optimized to end up with baseline resolution of all four stereoisomers with critical resolution of as high as about 2. The CEC method proved to be superior over the corresponding HPLC separations primarily due to significantly enhanced plate numbers (between 200,000 and 600,000 m(-1) in CEC). Diastereoselectivity contributions arising from electrophoretic mobility differences of the diastereomers facilitated the separation of the later eluted diastereomeric peak pair (peaks III and IV), but had a negative influence on the selectivity of the earlier eluted diastereomeric peak pair (peaks I and II). The stereoselective CEC assay allowed the assessment of the stereoisomeric purity of the individual isomers which were obtained by preparative HPLC on a CHIRALPAK QD-AX column that is based on the same tBuCQD selector. The present study demonstrates that there exist problems which are hard to solve by HPLC, yet can be conveniently solved by CEC. Moreover, it was intended to prove by this practical application that CEC with monolithic columns is robust enough to be used for solving real-life problems.
Collapse
Affiliation(s)
- Beatrix Preinerstorfer
- Christian Doppler Laboratory for Molecular Recognition Materials, Department of Analytical & Food Chemistry, University of Vienna, Vienna, Austria
| | | | | | | | | | | |
Collapse
|
25
|
Zusková I, Novotná A, Vceláková K, Gas B. Determination of limiting mobilities and dissociation constants of 21 amino acids by capillary zone electrophoresis at very low pH. J Chromatogr B Analyt Technol Biomed Life Sci 2006; 841:129-34. [PMID: 16567135 DOI: 10.1016/j.jchromb.2006.03.015] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2006] [Revised: 03/06/2006] [Accepted: 03/07/2006] [Indexed: 10/24/2022]
Abstract
The dependence of the effective electrophoretic mobility on pH of the background electrolyte was experimentally determined by capillary zone electrophoresis (CZE) for cationic forms of amino acids. The pH of the background electrolytes was in the highly acidic range, 1.6-2.6 pH units, to ensure a high degree of protonation of the amino acids. Poly(vinyl alcohol) was added to the background electrolytes to avoid possible adsorption of the analytes at the inner capillary wall. Non-linear regression of the experimental data was applied to obtain the parameters of the relevant regression functions--the actual mobilities and mixed dissociation constants corresponding to the actual ionic strength. The extended Onsager and Debye-Hückel law was used to calculate the limiting mobilities and thermodynamic dissociation constants. The comparison of the experimental electropherogram with the computer prediction by PeakMaster using the determined data is presented for the selected sample of amino acids.
Collapse
Affiliation(s)
- Iva Zusková
- Department of Physical and Macromolecular Chemistry, Faculty of Science, Charles University, Prague, Czech Republic.
| | | | | | | |
Collapse
|
26
|
Jiráček J, Collinsová M, Rosenberg I, Buděšínský M, Protivínská E, Netušilová H, Garrow TA. S-alkylated homocysteine derivatives: new inhibitors of human betaine-homocysteine S-methyltransferase. J Med Chem 2006; 49:3982-9. [PMID: 16789755 PMCID: PMC2622432 DOI: 10.1021/jm050885v] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
A series of S-alkylated derivatives of homocysteine were synthesized and characterized as inhibitors of human recombinant betaine-homocysteine S-methyltransferase (BHMT). Some of these compounds inhibit BHMT with IC50 values in the nanomolar range. BHMT is very sensitive to the structure of substituents on the sulfur atom of homocysteine. The S-carboxybutyl and S-carboxypentyl derivatives make the most potent inhibitors, and an additional sulfur atom in the alkyl chain is well tolerated. The respective (R,S)-5-(3-amino-3-carboxy-propylsulfanyl)-pentanoic, (R,S)-6-(3-amino-3-carboxy-propylsulfanyl)-hexanoic, and (R,S)-2-amino-4-(2-carboxymethylsulfanyl-ethylsulfanyl)-butyric acids are very potent inhibitors and are the strongest ever reported. We determined that (R,S)-5-(3-amino-3-carboxy-propylsulfanyl)-pentanoic acid displays competitive inhibition with respect to betaine binding with a Kappi of 12 nM. Some of these compounds are currently being tested in mice to study the influence of BHMT on the metabolism of sulfur amino acids in vivo.
Collapse
Affiliation(s)
- Jiří Jiráček
- Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Flemingovo nám. 2, 166 10 Prague 6, Czech Republic
- Corresponding authors. Tel +420220183441, fax +420220183571, e-mails ,
| | - Michaela Collinsová
- Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Flemingovo nám. 2, 166 10 Prague 6, Czech Republic
| | - Ivan Rosenberg
- Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Flemingovo nám. 2, 166 10 Prague 6, Czech Republic
- Corresponding authors. Tel +420220183441, fax +420220183571, e-mails ,
| | - Miloš Buděšínský
- Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Flemingovo nám. 2, 166 10 Prague 6, Czech Republic
| | - Eva Protivínská
- Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Flemingovo nám. 2, 166 10 Prague 6, Czech Republic
| | - Hana Netušilová
- Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Flemingovo nám. 2, 166 10 Prague 6, Czech Republic
| | - Timothy A. Garrow
- Department of Food Science and Human Nutrition, University of Illinois, Urbana, Illinois 61801, USA
| |
Collapse
|
27
|
Solínová V, Kasicka V, Koval D, Cesnek M, Holý A. Determination of acid-base dissociation constants of amino- and guanidinopurine nucleotide analogs and related compounds by capillary zone electrophoresis. Electrophoresis 2006; 27:1006-19. [PMID: 16470755 DOI: 10.1002/elps.200500815] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
CZE has been applied for determination of acid-base dissociation constants (pKa) of ionogenic groups of newly synthesized amino- and (amino)guanidinopurine nucleotide analogs, such as acyclic nucleoside phosphonate, acyclic nucleoside phosphonate diesters and other related compounds. These compounds bear characteristic pharmacophores contained in various important biologically active substances, such as cytostatics and antivirals. The pKa values of ionogenic groups of the above compounds were determined by nonlinear regression analysis of the experimentally measured pH dependence of their effective electrophoretic mobilities. The effective mobilities were measured by CZE performed in series of BGEs in a broad pH range (3.50-11.25), at constant ionic strength (25 mM) and temperature (25 degrees C). pKa values were determined for the protonated guanidinyl group in (amino)guanidino 9-alkylpurines and in (amino)guanidinopurine nucleotide analogs, such as acyclic nucleoside phosphonates and acyclic nucleoside phosphonate diesters, for phosphonic acid to the second dissociation degree (-2) in acyclic nucleoside phosphonates of amino and (amino)guanidino 9-alkylpurines, and for protonated nitrogen in position 1 (N1) of purine moiety in acyclic nucleoside phosphonates of amino 9-alkylpurines. Thermodynamic pKa of protonated guanidinyl group was estimated to be in the range of 7.75-10.32, pKa of phosphonic acid to the second dissociation degree achieved values of 6.64-7.46, and pKa of protonated nitrogen in position 1 of purine was in the range of 4.13-4.89, depending on the structure of the analyzed compounds.
Collapse
Affiliation(s)
- Veronika Solínová
- Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Prague, Czech Republic
| | | | | | | | | |
Collapse
|
28
|
Solínová V, Kasicka V, Barth T, Hauzerová L, Fanali S. Analysis and separation of enkephalin and dalargin analogues and fragments by capillary zone electrophoresis. J Chromatogr A 2005; 1081:9-18. [PMID: 16013591 DOI: 10.1016/j.chroma.2005.01.046] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Capillary zone electrophoresis (CZE) has been applied to qualitative and quantitative analysis and separation of synthetic analogues and fragments of enkephalins ([Leu5]enkephalin, H-Tyr-Gly-Gly-Phe-Leu-OH, [Met5]enkephalin, H-Tyr-Gly-Gly-Phe-Met-OH), and dalargin (H-Tyr-D-Ala-Gly-Phe-Leu-Arg-OH), biologically active peptides with morphin-like effects acting as ligands for the opiate receptors in the brain. These oligopeptides (dipeptides to hexapeptides) were analyzed as cations in two acidic background electrolytes (BGEs), BGE I (100mM H3PO4, 50mM Tris, pH 2.25), BGE II (100mM iminodiacetic acid, pH 2.30), and both as cations and anions in alkaline BGE IV (40 mM Tris, 40 mM Tricine, pH 8.10). Purity degrees of peptides, expressed in three different ways (relative peak height, relative peak area and relative corrected peak area), were determined by their CZE analyses in the above BGEs, and their values were compared with respect to the peak shapes and migration times of the main synthetic products and their admixtures. Selected analogues and fragments of enkephalins and dalargin were successfully separated by CZE in acidic isoelectric buffers, 100 and 200 mM iminodiacetic acid, pH 2.30 and 2.32, respectively. The effective electrophoretic mobilities at standard temperature 25 degrees C, and effective and specific charges of all analyzed peptides in the above three BGEs were determined. Correlation between effective electrophoretic mobility of the analyzed peptides and their charge and size (relative molecular mass) was investigated, which revealed different molecular shape of analyzed peptides in acidic and alkaline BGEs. In addition, the selected characteristics of the UV-absorption detector (noise, signal to noise ratio, sensitivity, and limits of detection and quantification) were determined.
Collapse
Affiliation(s)
- Veronika Solínová
- Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Flemingovo 2, 16610 Prague 6, Czech Republic
| | | | | | | | | |
Collapse
|
29
|
Tůma P, Samcová E, Balínová P. Determination of 3-methylhistidine and 1-methylhistidine in untreated urine samples by capillary electrophoresis. J Chromatogr B Analyt Technol Biomed Life Sci 2005; 821:53-9. [PMID: 15899597 DOI: 10.1016/j.jchromb.2005.04.006] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2004] [Revised: 04/04/2005] [Accepted: 04/09/2005] [Indexed: 10/25/2022]
Abstract
Capillary electrophoretic (CE) method was developed for the determination of urinary 3-methylhistidine (3MH) and 1-methylhistidine (1MH) indicating the extent of degradation of skeletal muscle proteins and thereby the state of human health. 3MH, 1MH and histidine can be separated in both acidic and alkaline media, where these amino acids form cation and anion, respectively. The effective mobility of all ionic forms was measured over a broad range of pH (1.67-11.80), which made it possible to evaluate the corresponding dissociation constants. 3MH and 1MH were determined together with creatinine in untreated urine samples with the limit of detection of 2.4 microM (0.4 mgL(-1)) and 3.0 microM (0.5 mgL(-1)), respectively. Determination was fast and took ca. 12 min including the column washing. Method was employed for an analysis of urine collected from healthy individuals, and from the patients hospitalized with obesity and diabetes mellitus II. This analysis has revealed differences between the healthy individuals and the patients pointing to a more extensive degradation of muscle proteins in the latter group.
Collapse
Affiliation(s)
- Petr Tůma
- Charles University, 3rd Faculty of Medicine, Centre of Biomedical Sciences, Ruská 87, 100 00 Prague 10, Czech Republic
| | | | | |
Collapse
|
30
|
Koval D, Kašička V, Jiráček J, Collinsová M. Separation of diastereomers of phosphinic pseudopeptides by capillary zone electrophoresis and reverse phase high-performance liquid chromatography. J Sep Sci 2003. [DOI: 10.1002/jssc.200301382] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
|
31
|
Collinsová M, Castro C, Garrow TA, Yiotakis A, Dive V, Jirácek J. Combining combinatorial chemistry and affinity chromatography: highly selective inhibitors of human betaine: homocysteine S-methyltransferase. CHEMISTRY & BIOLOGY 2003; 10:113-22. [PMID: 12618183 DOI: 10.1016/s1074-5521(03)00008-5] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
A new method to find novel protein targets for ligands of interest is proposed. The principle of this approach is based on affinity chromatography and combinatorial chemistry. The proteins within a crude rat liver homogenate were allowed to interact with a combinatorial library of phosphinic pseudopeptides immobilized on affinity columns. Betaine: homocysteine S-methyltransferase (BHMT) was one of the proteins that was retained and subsequently eluted from these supports. The phosphinic pseudopeptides, which served as immobilized ligands for the isolation of rat BHMT, were then tested for their ability to inhibit human recombinant BHMT in solution. The most potent inhibitor also behaved as a selective ligand for the affinity purification of BHMT from a complex media. Further optimization uncovered Val-Phe-psi[PO(2-)-CH(2)]-Leu-His-NH(2) as a potent BHMT inhibitor that has an IC(50) of about 1 microM.
Collapse
Affiliation(s)
- Michaela Collinsová
- Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Flemingovo nám. 2, 16610 Praha 6, Czech Republic
| | | | | | | | | | | |
Collapse
|