Václav Kašička - Academia.edu (original) (raw)
Papers by Václav Kašička
Journal of Separation Science, 2016
Journal of Organic Chemistry, Feb 1, 2023
Dyes and Pigments, Apr 1, 2023
CRC Press eBooks, Jan 3, 2023
Chemicke Listy, 2013
Rukopis byl zařazen k tisku v rámci placené služby urychleného publikování. Klíčová slova: kapilá... more Rukopis byl zařazen k tisku v rámci placené služby urychleného publikování. Klíčová slova: kapilární elektromigrační metody, ionizační techniky, rozhraní, hmotnostní spektrometrie Obsah 1. Úvod 2. Ionizační techniky pro spojení CE-MS 2.1. Chemická ionizace za atmosférického tlaku 2.2. Fotoionizace za atmosférického tlaku 2.3. Ionizace elektrosprejem 2.4. Desorpční ionizace elektrosprejem 2.5. Přímá analýza v reálném čase 2.6. Ionizace laserem za účasti matrice 3. Rozhraní pro spojení CE-ESI-MS 3.1. Rozhraní bez přídavné kapaliny 3.2. Kapalinový spoj 3.3. Rozhraní s přídavnou kapalinou 4. Závěr
High-performance capillary electrophoresis (HPCE) has been applied to qualitative and quantitativ... more High-performance capillary electrophoresis (HPCE) has been applied to qualitative and quantitative analysis of several biologically active peptides and their derivatives and fragments, e.g. insulins, insect oostatic hormones, and peptide and glycopeptide dendrimers
Two methods were used for analysis of purity of different kinds of peptides those having ionogeni... more Two methods were used for analysis of purity of different kinds of peptides those having ionogenic groups and those devoid of ionogenic groups
Electrophoresis, Sep 6, 2022
We present a method for finely adjustable electroosmotic flow (EOF) velocity in cathodic directio... more We present a method for finely adjustable electroosmotic flow (EOF) velocity in cathodic direction for the optimization of separations in capillary electrophoresis. To this end, we use surface modification of the separation fused silica capillary by the covalently attached copolymer of acrylamide (AM) and 2‐acrylamido‐2‐methyl‐1‐propanesulfonate (AMPS), that is, poly(AM‐co‐AMPS) or PAMAMPS. Coatings were formed by the in‐capillary polymerization of a mixture of the neutral AM and anionic AMPS monomers premixed in various ratios in order to control the charge density of the copolymer. EOF mobility varies in the 0 to ∼40 × 10−9 m2 V−1 s−1 interval for PAMAMPS coatings ranging from 0 to 60 mol.% of charged AMPS monomer. For EOF in PAMAMPS‐treated capillaries, we observed (i) a negligible dependence on pH in the 2–10 interval, (ii) a minor variance among background electrolytes (BGEs) in function of their components and (iii) its standard decrease with increasing ionic strength of the BGE. Interest in variable cathodic EOF was demonstrated by the amelioration of separation of two kinds of isomeric anionic analytes, that is, monosaccharides phosphates and helquat enantiomers, in counter‐EOF mode.
Capillary zone electrophoresis and micellar electrokinetic chromatography have been employed for ... more Capillary zone electrophoresis and micellar electrokinetic chromatography have been employed for determination of electrophoretic purity degree, limit of detection and limit of quantification of twelve mono-Nacylated derivatives of 2,6-diaminopimelic acid (DAP). In addition, the DAP derivatives were characterized by effective electrophoretic mobilities of their cationic and anionic forms in several classical and isoelectric buffer-based background electrolytes within a broad pH range 2.18 – 8.64
The mechanisms of reactions causing irreversible inhibition of the activity of enzymes when irrad... more The mechanisms of reactions causing irreversible inhibition of the activity of enzymes when irradiated in the presence of the recently developed alpha-methyl-6-nitroveratryl-based photolinker [Holmes CP. J. Org. Chem. 1997; 62: 2370-2380] have been investigated. Several experiments based on the interaction of the photolinker with model peptides or n-butylamine have been accomplished. A complexity of products, resulting from the side reactions competing with the 'normal' photocleavage of the linker, have been found. The amino and thiol groups of the molecules present in the solvents upon irradiation were recognized as having a major influence on the course of photolysis. Some of these side products resulting from the interaction with amines were identified and the mechanisms by which they can be generated are discussed. The mechanism of the interaction of the thiol groups present in peptides or proteins with the photolinker is unclear and it remains to be further elucidated. It was found that the undesirable effects are favored by a basic pH and are largely reduced by a slightly acidic pH, together with the presence of dithiothreitol. Significant positive effects of dithiothreitol have been observed on the rate as well as the yield of the photocleavage. These results demonstrate that the use of photolabile linkers in biological media can be accompanied by undesired effects, which can be largely reduced by choosing appropriate conditions and additives.
Capillary affinity electrophoresis was applied to quantitative evaluation of the strength of the ... more Capillary affinity electrophoresis was applied to quantitative evaluation of the strength of the complexes of i) valinomycin, macrocyclic dodecadepsipeptide ionophore, with small cations (ammonium and alkali metal ions, Li+, Na+, K+, Rb+ and Cs+) in methanol, and ii) enantiomers of dipeptide beta-alanyl-D,L-tyrosine and its derivatives with a chiral selector, 2 hydroxypropyl-beta-cyclodextrin (2-HP-beta-CD), in water
Journal of Separation Science, Mar 4, 2023
Recent developments and applications of capillary and microchip electrophoresis in proteomic and ... more Recent developments and applications of capillary and microchip electrophoresis in proteomic and peptidomic analyses This review presents recent developments and applications of capillary and microchip electromigration methods in proteomics and peptidomics. Sample preparation methods as well as instrumental innovations in the coupling of these advanced electromigration methods with mass spectrometry detection employed in proteomic and peptidomic analyses are presented. Interesting applications of various capillary electromigration methods in bottom-up as well as top-down proteomics, including investigation of post-translational modifications of proteins are described. In addition, several examples of the use of capillary electromigration methods combined with mass spectrometry detection in clinical proteomics and peptidomics are demonstrated.
Journal of Chromatography A, Aug 1, 2021
Triazole fungicides (TAFs) are frequently used fungicides for various antifungal treatments of cr... more Triazole fungicides (TAFs) are frequently used fungicides for various antifungal treatments of crops. Tre treatment is provided foliarly. However, some significant amount of TAFs may remain on/in fruits. We have developed a methodology for the determination of penconazole, tebuconazole and cyproconazole in tomato fruit peel. The extraction of TAFs was provided with chloroform (acidified with 0.1% acetic acid). In the electrokinetic chromatography, the mixed micellar pseudo-stationary phase was composed of anionic detergent sodium dodecyl sulphate (15 mM) and randomly highly sulphated gamma-cyclodextrin (17.5 mg/mL). The background electrolyte consisted of 100 mM phosphoric acid and 100 mM Tris in the mixed hydro-organic solvent water/methanol (80/20 v/v), apparent pH 4.8. Complete separation of penconazole, tebuconazole, and two diastereomers of cyproconazole with resolutions higher than 5.1 were achieved within a relatively short time of less than 17 min in the bare fused silica capillary of 425/500 mm total/effective lengths and 50/375 μm I.D./O.D. at separation voltage -15 kV (cathode at injection capillary end) and at constant capillary cassette temperature of 22°C. The TAFs were detected by a UV-spectrophotometric diode array detector set at 200 nm. The limits of detection and limits of quantification were in the range of 71-92 and 214-278 μg/kg of peel, respectively. Analyses of the peel extracts revealed that even 10 days after the last treatment, TAF concentrations were higher than the recommended maximum residue limits in both application ways, as individual as well as in the TAF binary or ternary mixtures.
![Research paper thumbnail of Affinity capillary electrophoresis and quantum mechanical calculations applied to investigation of [Gly6]-antamanide binding with sodium and potassium ions](https://attachments.academia-assets.com/114335856/thumbnails/1.jpg)
](Electrophoresis, Feb 14, 2017
In this study, two complementary approaches, affinity capillary electrophoresis (ACE) and quantum... more In this study, two complementary approaches, affinity capillary electrophoresis (ACE) and quantum mechanical density functional theory (DFT) calculations, have been employed for quantitative characterization and structure elucidation of the complex between hexaarylbenzene (HAB)-based receptor R and lithium ion Li 1. First, by means of ACE, the apparent binding constant of LiR 1 complex (K LiR 1) in methanol was determined from the dependence of the effective electrophoretic mobilities of LiR 1 complex on the concentration of lithium ions in the 25 mM Tris/50 mM chloroacetate background electrolyte (BGE) using non-linear regression analysis. Prior to regression analysis, the effective electrophoretic mobilities of the LiR 1 complex were corrected to reference temperature 251C and constant ionic strength 25 mM. The apparent binding constant of the LiR 1 complex in the above methanolic BGE was evaluated as logK LiR 1 = 1.1570.09. Second, the most probable structures of nonhydrated LiR 1 and hydrated LiR 1 Á 3H 2 O complexes were derived by DFT calculations. The optimized structure of the hydrated LiR 1 Á 3H 2 O complex was found to be more realistic than the nonhydrated LiR 1 complex because of the considerably higher binding energy of LiR 1 Á 3H 2 O complex (500.4 kJ/mol) as compared with LiR 1 complex (427.5 kJ/mol).
Talanta, Jun 1, 2021
Robust decoupling of the ESI potential from the separation potential in CE-ESI-MS interfaces is v... more Robust decoupling of the ESI potential from the separation potential in CE-ESI-MS interfaces is very important for the high performance of the CE-ESI-MS devices and their applications for highly sensitive analyses of ionogenic compounds. In this study, we utilize a nanoflow sheath-liquid CE-ESI-MS interface composed of a quartz emitter and a separation fused silica capillary treated by etching, which are threaded to cross coupling for sheath liquid and electrode connection. Specifically, we have tested the ability of the interface to decouple the ESI potential from the separation potential at different positions of the separation capillary and ESI emitter tube tips. The interface with the separation capillary tip protruding the emitter tip by 20 μm did not provide sufficient robustness. The real ESI potential (delivered as 2.0 kV from the independent high voltage power supply HV2) ranged from 2.1 kV to 4.5 kV depending on the applied separation voltage (12.0-20.0 kV, provided by the power supply HV1) and electric conductivity of the background electrolyte (BGE) used. The interface robustness was partially improved when the capillary tip was aligned with the emitter tip. However, the complete decoupling of the spray and separation potentials was achieved only when the capillary tip was retracted 20 μm inside the emitter. In this arrangement, the ESI potential was stable and independent of both the separation potential (voltage) and the BGE conductivity. Moreover, this setting provided better sensitivity for the CE-ESI-MS analysis of selected drugs and benzylpyridinium cations than the setup with the capillary tip aligned with or protruding the emitter tip.
Journal of Separation Science, 2016
Journal of Organic Chemistry, Feb 1, 2023
Dyes and Pigments, Apr 1, 2023
CRC Press eBooks, Jan 3, 2023
Chemicke Listy, 2013
Rukopis byl zařazen k tisku v rámci placené služby urychleného publikování. Klíčová slova: kapilá... more Rukopis byl zařazen k tisku v rámci placené služby urychleného publikování. Klíčová slova: kapilární elektromigrační metody, ionizační techniky, rozhraní, hmotnostní spektrometrie Obsah 1. Úvod 2. Ionizační techniky pro spojení CE-MS 2.1. Chemická ionizace za atmosférického tlaku 2.2. Fotoionizace za atmosférického tlaku 2.3. Ionizace elektrosprejem 2.4. Desorpční ionizace elektrosprejem 2.5. Přímá analýza v reálném čase 2.6. Ionizace laserem za účasti matrice 3. Rozhraní pro spojení CE-ESI-MS 3.1. Rozhraní bez přídavné kapaliny 3.2. Kapalinový spoj 3.3. Rozhraní s přídavnou kapalinou 4. Závěr
High-performance capillary electrophoresis (HPCE) has been applied to qualitative and quantitativ... more High-performance capillary electrophoresis (HPCE) has been applied to qualitative and quantitative analysis of several biologically active peptides and their derivatives and fragments, e.g. insulins, insect oostatic hormones, and peptide and glycopeptide dendrimers
Two methods were used for analysis of purity of different kinds of peptides those having ionogeni... more Two methods were used for analysis of purity of different kinds of peptides those having ionogenic groups and those devoid of ionogenic groups
Electrophoresis, Sep 6, 2022
We present a method for finely adjustable electroosmotic flow (EOF) velocity in cathodic directio... more We present a method for finely adjustable electroosmotic flow (EOF) velocity in cathodic direction for the optimization of separations in capillary electrophoresis. To this end, we use surface modification of the separation fused silica capillary by the covalently attached copolymer of acrylamide (AM) and 2‐acrylamido‐2‐methyl‐1‐propanesulfonate (AMPS), that is, poly(AM‐co‐AMPS) or PAMAMPS. Coatings were formed by the in‐capillary polymerization of a mixture of the neutral AM and anionic AMPS monomers premixed in various ratios in order to control the charge density of the copolymer. EOF mobility varies in the 0 to ∼40 × 10−9 m2 V−1 s−1 interval for PAMAMPS coatings ranging from 0 to 60 mol.% of charged AMPS monomer. For EOF in PAMAMPS‐treated capillaries, we observed (i) a negligible dependence on pH in the 2–10 interval, (ii) a minor variance among background electrolytes (BGEs) in function of their components and (iii) its standard decrease with increasing ionic strength of the BGE. Interest in variable cathodic EOF was demonstrated by the amelioration of separation of two kinds of isomeric anionic analytes, that is, monosaccharides phosphates and helquat enantiomers, in counter‐EOF mode.
Capillary zone electrophoresis and micellar electrokinetic chromatography have been employed for ... more Capillary zone electrophoresis and micellar electrokinetic chromatography have been employed for determination of electrophoretic purity degree, limit of detection and limit of quantification of twelve mono-Nacylated derivatives of 2,6-diaminopimelic acid (DAP). In addition, the DAP derivatives were characterized by effective electrophoretic mobilities of their cationic and anionic forms in several classical and isoelectric buffer-based background electrolytes within a broad pH range 2.18 – 8.64
The mechanisms of reactions causing irreversible inhibition of the activity of enzymes when irrad... more The mechanisms of reactions causing irreversible inhibition of the activity of enzymes when irradiated in the presence of the recently developed alpha-methyl-6-nitroveratryl-based photolinker [Holmes CP. J. Org. Chem. 1997; 62: 2370-2380] have been investigated. Several experiments based on the interaction of the photolinker with model peptides or n-butylamine have been accomplished. A complexity of products, resulting from the side reactions competing with the 'normal' photocleavage of the linker, have been found. The amino and thiol groups of the molecules present in the solvents upon irradiation were recognized as having a major influence on the course of photolysis. Some of these side products resulting from the interaction with amines were identified and the mechanisms by which they can be generated are discussed. The mechanism of the interaction of the thiol groups present in peptides or proteins with the photolinker is unclear and it remains to be further elucidated. It was found that the undesirable effects are favored by a basic pH and are largely reduced by a slightly acidic pH, together with the presence of dithiothreitol. Significant positive effects of dithiothreitol have been observed on the rate as well as the yield of the photocleavage. These results demonstrate that the use of photolabile linkers in biological media can be accompanied by undesired effects, which can be largely reduced by choosing appropriate conditions and additives.
Capillary affinity electrophoresis was applied to quantitative evaluation of the strength of the ... more Capillary affinity electrophoresis was applied to quantitative evaluation of the strength of the complexes of i) valinomycin, macrocyclic dodecadepsipeptide ionophore, with small cations (ammonium and alkali metal ions, Li+, Na+, K+, Rb+ and Cs+) in methanol, and ii) enantiomers of dipeptide beta-alanyl-D,L-tyrosine and its derivatives with a chiral selector, 2 hydroxypropyl-beta-cyclodextrin (2-HP-beta-CD), in water
Journal of Separation Science, Mar 4, 2023
Recent developments and applications of capillary and microchip electrophoresis in proteomic and ... more Recent developments and applications of capillary and microchip electrophoresis in proteomic and peptidomic analyses This review presents recent developments and applications of capillary and microchip electromigration methods in proteomics and peptidomics. Sample preparation methods as well as instrumental innovations in the coupling of these advanced electromigration methods with mass spectrometry detection employed in proteomic and peptidomic analyses are presented. Interesting applications of various capillary electromigration methods in bottom-up as well as top-down proteomics, including investigation of post-translational modifications of proteins are described. In addition, several examples of the use of capillary electromigration methods combined with mass spectrometry detection in clinical proteomics and peptidomics are demonstrated.
Journal of Chromatography A, Aug 1, 2021
Triazole fungicides (TAFs) are frequently used fungicides for various antifungal treatments of cr... more Triazole fungicides (TAFs) are frequently used fungicides for various antifungal treatments of crops. Tre treatment is provided foliarly. However, some significant amount of TAFs may remain on/in fruits. We have developed a methodology for the determination of penconazole, tebuconazole and cyproconazole in tomato fruit peel. The extraction of TAFs was provided with chloroform (acidified with 0.1% acetic acid). In the electrokinetic chromatography, the mixed micellar pseudo-stationary phase was composed of anionic detergent sodium dodecyl sulphate (15 mM) and randomly highly sulphated gamma-cyclodextrin (17.5 mg/mL). The background electrolyte consisted of 100 mM phosphoric acid and 100 mM Tris in the mixed hydro-organic solvent water/methanol (80/20 v/v), apparent pH 4.8. Complete separation of penconazole, tebuconazole, and two diastereomers of cyproconazole with resolutions higher than 5.1 were achieved within a relatively short time of less than 17 min in the bare fused silica capillary of 425/500 mm total/effective lengths and 50/375 μm I.D./O.D. at separation voltage -15 kV (cathode at injection capillary end) and at constant capillary cassette temperature of 22°C. The TAFs were detected by a UV-spectrophotometric diode array detector set at 200 nm. The limits of detection and limits of quantification were in the range of 71-92 and 214-278 μg/kg of peel, respectively. Analyses of the peel extracts revealed that even 10 days after the last treatment, TAF concentrations were higher than the recommended maximum residue limits in both application ways, as individual as well as in the TAF binary or ternary mixtures.
Electrophoresis, Feb 14, 2017
In this study, two complementary approaches, affinity capillary electrophoresis (ACE) and quantum... more In this study, two complementary approaches, affinity capillary electrophoresis (ACE) and quantum mechanical density functional theory (DFT) calculations, have been employed for quantitative characterization and structure elucidation of the complex between hexaarylbenzene (HAB)-based receptor R and lithium ion Li 1. First, by means of ACE, the apparent binding constant of LiR 1 complex (K LiR 1) in methanol was determined from the dependence of the effective electrophoretic mobilities of LiR 1 complex on the concentration of lithium ions in the 25 mM Tris/50 mM chloroacetate background electrolyte (BGE) using non-linear regression analysis. Prior to regression analysis, the effective electrophoretic mobilities of the LiR 1 complex were corrected to reference temperature 251C and constant ionic strength 25 mM. The apparent binding constant of the LiR 1 complex in the above methanolic BGE was evaluated as logK LiR 1 = 1.1570.09. Second, the most probable structures of nonhydrated LiR 1 and hydrated LiR 1 Á 3H 2 O complexes were derived by DFT calculations. The optimized structure of the hydrated LiR 1 Á 3H 2 O complex was found to be more realistic than the nonhydrated LiR 1 complex because of the considerably higher binding energy of LiR 1 Á 3H 2 O complex (500.4 kJ/mol) as compared with LiR 1 complex (427.5 kJ/mol).
Talanta, Jun 1, 2021
Robust decoupling of the ESI potential from the separation potential in CE-ESI-MS interfaces is v... more Robust decoupling of the ESI potential from the separation potential in CE-ESI-MS interfaces is very important for the high performance of the CE-ESI-MS devices and their applications for highly sensitive analyses of ionogenic compounds. In this study, we utilize a nanoflow sheath-liquid CE-ESI-MS interface composed of a quartz emitter and a separation fused silica capillary treated by etching, which are threaded to cross coupling for sheath liquid and electrode connection. Specifically, we have tested the ability of the interface to decouple the ESI potential from the separation potential at different positions of the separation capillary and ESI emitter tube tips. The interface with the separation capillary tip protruding the emitter tip by 20 μm did not provide sufficient robustness. The real ESI potential (delivered as 2.0 kV from the independent high voltage power supply HV2) ranged from 2.1 kV to 4.5 kV depending on the applied separation voltage (12.0-20.0 kV, provided by the power supply HV1) and electric conductivity of the background electrolyte (BGE) used. The interface robustness was partially improved when the capillary tip was aligned with the emitter tip. However, the complete decoupling of the spray and separation potentials was achieved only when the capillary tip was retracted 20 μm inside the emitter. In this arrangement, the ESI potential was stable and independent of both the separation potential (voltage) and the BGE conductivity. Moreover, this setting provided better sensitivity for the CE-ESI-MS analysis of selected drugs and benzylpyridinium cations than the setup with the capillary tip aligned with or protruding the emitter tip.