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Arthur K Covington - One of the best experts on this subject based on the ideXlab platform.
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re evaluation of the first and second stoichiometric Dissociation Constants of phthalic acid at temperatures from 0 to 60 c in aqueous phthalate buffer solutions with or without potassium chloride 2 estimation of parameters for the model for the first Dissociation Constant and tests and use of the resulting activity coefficient equations
Journal of Chemical & Engineering Data, 2006Co-Authors: Jaakko I Partanen, Arthur K CovingtonAbstract:Previously (in Part 1, J. Chem. Eng. Data 2006, 51, 777−784), equations were determined for the calculation of the second stoichiometric (molality scale) Dissociation Constant (Km2) of phthalic acid in buffer solutions containing potassium hydrogen phthalate (KHPh), dipotassium phthalate, and potassium chloride from the determined thermodynamic values of this Dissociation Constant (Ka2) and the molalities of the components in the solutions. These equations apply at temperatures from (0 to 60) °C up to ionic strengths of about 0.5 mol·kg-1, and they were based on the single-ion activity coefficient equations of the Huckel type. The parameters of phthalate species for these equations and the second thermodynamic Dissociation Constant of this acid at various temperatures were determined from Harned cell data of Hamer and Acree (J. Res. Natl. Bur. Stand. 1945, 35, 381−416), and the resulting parameter values were also tested with these data. In the present study, the corresponding equations were determined fr...
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re evaluation of the first and second stoichiometric Dissociation Constants of phthalic acid at temperatures from 0 to 60 c in aqueous phthalate buffer solutions with or without potassium chloride 1 estimation of the parameters for the huckel model activity coefficient equations for calculation of the second Dissociation Constant
Journal of Chemical & Engineering Data, 2006Co-Authors: Jaakko I Partanen, Arthur K CovingtonAbstract:Equations were developed for the calculation of the second stoichiometric (molality scale) Dissociation Constant (Km2) of phthalic acid in buffer solutions containing potassium dihydrogen phthalate, hydrogen phthalate, and chloride from the determined thermodynamic values of this Dissociation Constant (Ka2) and the molalities of the components in the solutions. These equations apply at temperatures from (0 to 60) °C up to ionic strengths of about 0.5 mol·kg-1, and they are based on the single-ion activity coefficient equations of the Huckel type. The parameters of phthalate ions for these equations and the thermodynamic values of the second Dissociation Constant of this acid at various temperatures were determined from the Harned cell data measured by Hamer and Acree (J. Res. Natl. Bur. Stand. 1945, 35, 381−416). In these parameter estimations, the stoichiometric values of the first Dissociation Constant of phthalic acid were needed, and these values were obtained from the Harned cell results of Hamer et ...
Jaakko I Partanen - One of the best experts on this subject based on the ideXlab platform.
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re evaluation of the first and second stoichiometric Dissociation Constants of phthalic acid at temperatures from 0 to 60 c in aqueous phthalate buffer solutions with or without potassium chloride 2 estimation of parameters for the model for the first Dissociation Constant and tests and use of the resulting activity coefficient equations
Journal of Chemical & Engineering Data, 2006Co-Authors: Jaakko I Partanen, Arthur K CovingtonAbstract:Previously (in Part 1, J. Chem. Eng. Data 2006, 51, 777−784), equations were determined for the calculation of the second stoichiometric (molality scale) Dissociation Constant (Km2) of phthalic acid in buffer solutions containing potassium hydrogen phthalate (KHPh), dipotassium phthalate, and potassium chloride from the determined thermodynamic values of this Dissociation Constant (Ka2) and the molalities of the components in the solutions. These equations apply at temperatures from (0 to 60) °C up to ionic strengths of about 0.5 mol·kg-1, and they were based on the single-ion activity coefficient equations of the Huckel type. The parameters of phthalate species for these equations and the second thermodynamic Dissociation Constant of this acid at various temperatures were determined from Harned cell data of Hamer and Acree (J. Res. Natl. Bur. Stand. 1945, 35, 381−416), and the resulting parameter values were also tested with these data. In the present study, the corresponding equations were determined fr...
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re evaluation of the first and second stoichiometric Dissociation Constants of phthalic acid at temperatures from 0 to 60 c in aqueous phthalate buffer solutions with or without potassium chloride 1 estimation of the parameters for the huckel model activity coefficient equations for calculation of the second Dissociation Constant
Journal of Chemical & Engineering Data, 2006Co-Authors: Jaakko I Partanen, Arthur K CovingtonAbstract:Equations were developed for the calculation of the second stoichiometric (molality scale) Dissociation Constant (Km2) of phthalic acid in buffer solutions containing potassium dihydrogen phthalate, hydrogen phthalate, and chloride from the determined thermodynamic values of this Dissociation Constant (Ka2) and the molalities of the components in the solutions. These equations apply at temperatures from (0 to 60) °C up to ionic strengths of about 0.5 mol·kg-1, and they are based on the single-ion activity coefficient equations of the Huckel type. The parameters of phthalate ions for these equations and the thermodynamic values of the second Dissociation Constant of this acid at various temperatures were determined from the Harned cell data measured by Hamer and Acree (J. Res. Natl. Bur. Stand. 1945, 35, 381−416). In these parameter estimations, the stoichiometric values of the first Dissociation Constant of phthalic acid were needed, and these values were obtained from the Harned cell results of Hamer et ...
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determination of stoichiometric Dissociation Constant of n butyric acid in aqueous sodium or potassium chloride solutions at 298 15 k
Fluid Phase Equilibria, 2000Co-Authors: Jaakko I Partanen, Pekka M JuusolaAbstract:Abstract Single-ion activity coefficient equations were determined for the calculation of the molality-scale Dissociation Constants, K m , for n -butyric acid in aqueous NaCl or KCl solutions at 298.15 K. The activity coefficient equations are of the Huckel type, and K m can be calculated by those for a certain ionic strength from the thermodynamic Dissociation Constant. The data used for the estimation of the parameters of these equations were measured by potentiometric titrations in a glass electrode cell. A new method was used to calculate the experimental K m values from the titration data. It was based on calibration titrations of acetic acid. The activity parameters for the Huckel equation were determined from the experimental K m values obtained by this method. The final activity parameters recommended in this study seem to be reliable. In addition to titration data, these parameters were here tested with the literature data measured on Harned and conductivity cells. K m can be calculated for n -butyric acid in NaCl and KCl solutions by using the Huckel model almost within experimental error up to I m of about 1 mol kg −1 .
Alan P Koretsky - One of the best experts on this subject based on the ideXlab platform.
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calibration of the calcium Dissociation Constant of rhod2in the perfused mouse heartusing manganese quenching
Cell Calcium, 2001Co-Authors: Congwu Du, Guy A Macgowan, Daniel L Farkas, Alan P KoretskyAbstract:Both theoretical and experimental results are presented for in vivo calibration of the Dissociation Constant KCadof the calcium-sensitive fluorescent dye Rhod2in the perfused mouse heart, using manganese quenching of fluorescence transients. An analytical model is derived, based on the biochemical equilibrium of manganese competition with calcium for Rhod2binding. Expressing the differential of the changes between systole and diastole in fluorescence transient (δΔ Fsys-dia). δΔFsys-diain a beating heart as a function of the perfusate manganese concentration [Mn2+]pallows correlation of the measured differential transient changes δΔ Fsys-diawith the calcium Dissociation Constant KCadof Rhod2and the calcium concentration in the heart. Numerical modeling indicates that the KCadpredominantly affects the asymptotic slope of the δΔ Fsys-diaversus [Mn2+]pcurve at certain manganese concentrations, which suggests that the KCadcan be inversely calculated by partially fitting the δΔ Fsys-diadistribution as a function of the perfusate manganese concentration. The feasibility of this approach is confirmed by quenching of calcium transients by manganese infusion into isolated perfused beating mouse hearts. The resulting calculated Dissociation Constant KCadof Rhod2is 720nM. Using the same approach, we are able to also estimate intracellular calcium concentrations of 700nM at peak systole and 300nM in diastole. This is in good agreement with values obtained by calibration of fluorescence values with a calcium saturation tetanization procedure in the same perfused mouse heart model.
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calibration of the calcium Dissociation Constant of rhod 2 in the perfused mouse heart using manganese quenching
Cell Calcium, 2001Co-Authors: Guy A Macgowan, Daniel L Farkas, Alan P KoretskyAbstract:Both theoretical and experimental results are presented for in vivo calibration of the Dissociation Constant KCadof the calcium-sensitive fluorescent dye Rhod2in the perfused mouse heart, using manganese quenching of fluorescence transients. An analytical model is derived, based on the biochemical equilibrium of manganese competition with calcium for Rhod2binding. Expressing the differential of the changes between systole and diastole in fluorescence transient (δΔ Fsys-dia). δΔFsys-diain a beating heart as a function of the perfusate manganese concentration [Mn2+]pallows correlation of the measured differential transient changes δΔ Fsys-diawith the calcium Dissociation Constant KCadof Rhod2and the calcium concentration in the heart. Numerical modeling indicates that the KCadpredominantly affects the asymptotic slope of the δΔ Fsys-diaversus [Mn2+]pcurve at certain manganese concentrations, which suggests that the KCadcan be inversely calculated by partially fitting the δΔ Fsys-diadistribution as a function of the perfusate manganese concentration. The feasibility of this approach is confirmed by quenching of calcium transients by manganese infusion into isolated perfused beating mouse hearts. The resulting calculated Dissociation Constant KCadof Rhod2is 720nM. Using the same approach, we are able to also estimate intracellular calcium concentrations of 700nM at peak systole and 300nM in diastole. This is in good agreement with values obtained by calibration of fluorescence values with a calcium saturation tetanization procedure in the same perfused mouse heart model.
Daniel L Farkas - One of the best experts on this subject based on the ideXlab platform.
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calibration of the calcium Dissociation Constant of rhod2in the perfused mouse heartusing manganese quenching
Cell Calcium, 2001Co-Authors: Congwu Du, Guy A Macgowan, Daniel L Farkas, Alan P KoretskyAbstract:Both theoretical and experimental results are presented for in vivo calibration of the Dissociation Constant KCadof the calcium-sensitive fluorescent dye Rhod2in the perfused mouse heart, using manganese quenching of fluorescence transients. An analytical model is derived, based on the biochemical equilibrium of manganese competition with calcium for Rhod2binding. Expressing the differential of the changes between systole and diastole in fluorescence transient (δΔ Fsys-dia). δΔFsys-diain a beating heart as a function of the perfusate manganese concentration [Mn2+]pallows correlation of the measured differential transient changes δΔ Fsys-diawith the calcium Dissociation Constant KCadof Rhod2and the calcium concentration in the heart. Numerical modeling indicates that the KCadpredominantly affects the asymptotic slope of the δΔ Fsys-diaversus [Mn2+]pcurve at certain manganese concentrations, which suggests that the KCadcan be inversely calculated by partially fitting the δΔ Fsys-diadistribution as a function of the perfusate manganese concentration. The feasibility of this approach is confirmed by quenching of calcium transients by manganese infusion into isolated perfused beating mouse hearts. The resulting calculated Dissociation Constant KCadof Rhod2is 720nM. Using the same approach, we are able to also estimate intracellular calcium concentrations of 700nM at peak systole and 300nM in diastole. This is in good agreement with values obtained by calibration of fluorescence values with a calcium saturation tetanization procedure in the same perfused mouse heart model.
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calibration of the calcium Dissociation Constant of rhod 2 in the perfused mouse heart using manganese quenching
Cell Calcium, 2001Co-Authors: Guy A Macgowan, Daniel L Farkas, Alan P KoretskyAbstract:Both theoretical and experimental results are presented for in vivo calibration of the Dissociation Constant KCadof the calcium-sensitive fluorescent dye Rhod2in the perfused mouse heart, using manganese quenching of fluorescence transients. An analytical model is derived, based on the biochemical equilibrium of manganese competition with calcium for Rhod2binding. Expressing the differential of the changes between systole and diastole in fluorescence transient (δΔ Fsys-dia). δΔFsys-diain a beating heart as a function of the perfusate manganese concentration [Mn2+]pallows correlation of the measured differential transient changes δΔ Fsys-diawith the calcium Dissociation Constant KCadof Rhod2and the calcium concentration in the heart. Numerical modeling indicates that the KCadpredominantly affects the asymptotic slope of the δΔ Fsys-diaversus [Mn2+]pcurve at certain manganese concentrations, which suggests that the KCadcan be inversely calculated by partially fitting the δΔ Fsys-diadistribution as a function of the perfusate manganese concentration. The feasibility of this approach is confirmed by quenching of calcium transients by manganese infusion into isolated perfused beating mouse hearts. The resulting calculated Dissociation Constant KCadof Rhod2is 720nM. Using the same approach, we are able to also estimate intracellular calcium concentrations of 700nM at peak systole and 300nM in diastole. This is in good agreement with values obtained by calibration of fluorescence values with a calcium saturation tetanization procedure in the same perfused mouse heart model.
Pawel Wiczling - One of the best experts on this subject based on the ideXlab platform.
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simultaneous determination of hydrophobicity and Dissociation Constant for a large set of compounds by gradient reverse phase high performance liquid chromatography mass spectrometry technique
Journal of Chromatography A, 2015Co-Authors: łukasz Kubik, Wiktoria Strucklewicka, Roman Kaliszan, Pawel WiczlingAbstract:Fast and reliable methods for the determination of hydrophobicity and acidity are desired in pre-clinical drug development phases to eliminate compounds with poor pharmacokinetic properties. Reversed-phase high-performance liquid chromatography (RP HPLC) coupled with time-of-flight mass spectrometry (RP HPLC-ESI-TOF-MS) is a convenient technique for that purpose. In this work we determined the chromatographic measure of hydrophobicity (logkw) and Dissociation Constant (pKa) simultaneously for a large and diverse group of 161 drugs. Retention times were determined by means of RP HPLC-ESI-TOF-MS for a series of pH and organic modifier gradients. We were able to measure retention times for 140 out of 161 (87%) compounds. For those analytes logkw and pKa parameters were calculated and compared with literature and ACD Labs-calculated data. The determined chromatographic measure of hydrophobicity and Dissociation Constant was closely related to literature and theoretically calculated values. Applied methodology achieved the medium-throughput screening rate of 100 compounds per day and proved to be a simple, fast and reliable approach of assessing important physicochemical properties of drugs. This technique has certain limitations as it is not applicable for very hydrophilic analytes (logP<0.5) and compounds with identical molar masses.
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the simultaneous determination of hydrophobicity and Dissociation Constant by liquid chromatography mass spectrometry
Journal of Pharmaceutical and Biomedical Analysis, 2014Co-Authors: Pawel Wiczling, Wiktoria Strucklewicka, łukasz Kubik, Danuta Siluk, Michal J Markuszewski, Roman KaliszanAbstract:Abstract Convenient methods for testing drug candidates’ lipophilicity and acidity are highly requested in modern pharmaceutical research and drug development strategies. Reversed-phase high-performance liquid chromatography (RP HPLC) might be particularly useful for the determination of both Dissociation Constant and the (pH-dependent) partition coefficient related parameters, applicable in high-throughput analysis of multi-component mixtures. The general theory of combined pH/organic modifier gradient has recently provided equations relating gradient retention time and pH of the mobile phase. The purpose of this work was to facilitate the identification of analytes in this technique by its transfer to RP HPLC coupled with time-of-flight mass spectrometry with electrospray ionization source (ESI-TOF-MS). The accuracy of the proposed methodology was assessed by analyzing a set of known drugs. The ammonium formate, ammonium acetate or ammonium bicarbonate buffers were used to control pH during chromatographic analysis. In result, the p K a and hydrophobicity parameters were determined and the accuracy of the estimated values was assessed by comparing them with literature data. The gradient RP HPLC coupled with ESI-TOF-MS methods allowed for the rapid determination of Dissociation Constant and hydrophobicity and was shown to be especially applicable for complex mixtures. The use of ESI-TOF-MS detection allowed to achieve the medium-throughput screening rate (100 compounds/day) and provided a simple approach to assess pharmacokinetically important physicochemical properties of drugs.