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Urquhart RJ, van Teijlingen A, Tuttle T. ANI neural network potentials for small molecule p Ka prediction. Phys Chem Chem Phys 2024; 26:23934-23943. [PMID: 39235138 DOI: 10.1039/d4cp01982b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/06/2024]
Abstract
The pKa value of a molecule is of interest to chemists across a broad spectrum of fields including pharmacology, environmental chemistry and theoretical chemistry. Determination of pKa values can be accomplished through several experimental methods such as NMR techniques and titration together with computational techniques such as DFT calculations. However, all of these methods remain time consuming and computationally expensive. In this work we develop a method for the rapid calculation of pKa values of small molecules which utilises a combination of neural network potentials, low energy conformer searches and thermodynamic cycles. We show that neural network potentials trained on different phase and charge states can be employed in tandem to predict the full thermodynamic energy cycle of molecules. Focusing here on imidazolium derived carbene species, the method utilised can easily be extended to other functional groups of interest such as amines with further training.
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Affiliation(s)
- Ross James Urquhart
- Department of Pure and Applied Chemistry, University of Strathclyde, 295 Cathedral Street, Glasgow, G1 1XL, UK.
| | - Alexander van Teijlingen
- Department of Pure and Applied Chemistry, University of Strathclyde, 295 Cathedral Street, Glasgow, G1 1XL, UK.
| | - Tell Tuttle
- Department of Pure and Applied Chemistry, University of Strathclyde, 295 Cathedral Street, Glasgow, G1 1XL, UK.
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2
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Du Y, Li J, Suryanarayanan R, Su Y. Probing Chemical Equilibrium in Frozen Sodium Phosphate Buffer Solution by 31P Solid-State NMR. J Phys Chem Lett 2024; 15:5714-5720. [PMID: 38768559 DOI: 10.1021/acs.jpclett.4c00877] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/22/2024]
Abstract
Phosphate buffers are crucial for cryopreservative stability in pharmaceuticals, food processing, biomedical sciences, and biology. However, their freeze concentrates lack quantitative characterization, especially regarding the physicochemical properties of phosphate salt species in equilibrium at subzero temperatures. This study employs 31P solid-state NMR (ssNMR) to analyze frozen sodium phosphate (NaP) solutions, providing insights into phase composition, ionic strength, and pH. For the first time, we have directly quantified phosphate species in frozen NaP buffer, including crystallized disodium phosphate dodecahydrate (Na2HPO4·12H2O) content and the concentrations of H2PO4- and HPO42- in the freeze concentrate. This enabled the calculation of the pH as well as the ionic strength in the freeze concentrate. Trehalose effectively mitigated pH shifts in buffer solutions by preventing the selective crystallization of salt, a spectroscopic phenomenon not previously observed experimentally.
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Affiliation(s)
- Yong Du
- Analytical Research and Development, Merck & Co., Inc., Rahway, New Jersey 07065, United States
| | - Jinghan Li
- Department of Pharmaceutics College of Pharmacy, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Raj Suryanarayanan
- Department of Pharmaceutics College of Pharmacy, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Yongchao Su
- Analytical Research and Development, Merck & Co., Inc., Rahway, New Jersey 07065, United States
- Pharmaceutical Sciences and Clinical Supply, Merck & Co., Inc., West Point, Pennsylvania 19486, United States
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3
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Paporakis S, Liu KTC, Brown SJ, Harper JB, Martin AV, Greaves TL. Thermal Stability of Protic Ionic Liquids. J Phys Chem B 2024; 128:4208-4219. [PMID: 38650054 DOI: 10.1021/acs.jpcb.3c08011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/25/2024]
Abstract
While protic ionic liquids (ILs) have found great success as solvents for a broad range of applications, little is known about their degradation when exposed to temperatures above ambient for extended periods of time. Here, we report the thermal stability of six protic ILs, namely, ethylammonium nitrate, ethylammonium formate, ethylammonium acetate, ethanolammonium nitrate, ethanolammonium formate, and ethanolammonium acetate. The effect of heating each ionic liquid to 60 °C for 1 h or 1 week (sealed or open to the atmosphere) was evaluated by considering the changes to water content, pH, mass, thermal phase transitions, and molecular structure after each treatment. Heating each of the six ILs when sealed led to measurable shifts in their water content and 10 wt % pH, but there was no significant change in their mass, thermal phase transitions according to differential scanning calorimetry (DSC), or molecular structure using proton nuclear magnetic resonance (1H NMR) spectra, indicating that the samples were largely unchanged. The samples that were heated open to the atmosphere also displayed no significant changes after 1 h but displayed significant changes after 1 week.
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Affiliation(s)
- Stefan Paporakis
- School of Science, College of STEM, RMIT University, 124 La Trobe Street, Melbourne ,VIC 3000, Australia
| | - Kenny T-C Liu
- School of Science, College of STEM, RMIT University, 124 La Trobe Street, Melbourne ,VIC 3000, Australia
| | - Stuart J Brown
- School of Science, College of STEM, RMIT University, 124 La Trobe Street, Melbourne ,VIC 3000, Australia
| | - Jason B Harper
- School of Chemistry, University of New South Wales, UNSW, Sydney, NSW 2052, Australia
| | - Andrew V Martin
- School of Science, College of STEM, RMIT University, 124 La Trobe Street, Melbourne ,VIC 3000, Australia
| | - Tamar L Greaves
- School of Science, College of STEM, RMIT University, 124 La Trobe Street, Melbourne ,VIC 3000, Australia
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4
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Gauthier-Manuel B, Benmouhoub C, Wacogne B. Fluorescence Spectra of Prototropic Forms of Fluorescein and Some Derivatives and Their Potential Use for Calibration-Free pH Sensing. SENSORS (BASEL, SWITZERLAND) 2024; 24:1705. [PMID: 38475241 DOI: 10.3390/s24051705] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/25/2024] [Revised: 03/04/2024] [Accepted: 03/05/2024] [Indexed: 03/14/2024]
Abstract
Fluorescence pH sensing has proven to be efficient but with the drawback that molecules photobleach, requiring frequent calibrations. Double-emission peak molecules allow ratiometric measurements and theoretically avoid calibration. However, they are often expensive and fragile and usually have very low quantum yields. Single emission peaks such as fluorescein and derivatives are inexpensive and have very high quantum yields. Because they are single emission peaks, the pH is assumed to be derived from the ratio of emitted intensities at measured pH and at high pH values, i.e., they require frequent calibration. However, the shape of their single emitted peak evolves slightly with pH. In this paper, we first demonstrate a simple method to calculate the emission spectrum shape of each prototropic form of fluorescein (and derivatives) as well as the values of the pKas. A complete model of the evolution of the emission spectrum shape with pH is then constructed. Second, we evaluate the potential of these molecules for pH sensing by fitting the experimental spectra with the complete emission model. The method is applied to fluorescein, FITC and FAM. Depending on the molecule, pH can be measured from pH 1.9 to pH 7.3 with standard deviations between 0.06 and 0.08 pH units. Estimating pH and pKas from shape instead of intensity allows calibration-free measurements even with single-emission peak molecules.
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Affiliation(s)
| | - Chafia Benmouhoub
- CNRS, Institut FEMTO-ST, Université de Franche-Comté, 25000 Besançon, France
- SATT Grand Est, SAYENS, 25000 Besançon, France
| | - Bruno Wacogne
- CNRS, Institut FEMTO-ST, Université de Franche-Comté, 25000 Besançon, France
- INSERM CIC 1431, Besançon University Hospital, 25030 Besançon, France
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5
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Patyk-Kaźmierczak E, Izquierdo-Ruiz F, Lobato A, Kaźmierczak M, Moszczyńska I, Olejniczak A, Recio JM. The curious case of proton migration under pressure in the malonic acid and 4,4'-bipyridine cocrystal. IUCRJ 2024; 11:168-181. [PMID: 38275161 PMCID: PMC10916288 DOI: 10.1107/s2052252524000344] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/10/2023] [Accepted: 01/09/2024] [Indexed: 01/27/2024]
Abstract
In the search for new active pharmaceutical ingredients, the precise control of the chemistry of cocrystals becomes essential. One crucial step within this chemistry is proton migration between cocrystal coformers to form a salt, usually anticipated by the empirical ΔpKa rule. Due to the effective role it plays in modifying intermolecular distances and interactions, pressure adds a new dimension to the ΔpKa rule. Still, this variable has been scarcely applied to induce proton-transfer reactions within these systems. In our study, high-pressure X-ray diffraction and Raman spectroscopy experiments, supported by DFT calculations, reveal modifications to the protonation states of the 4,4'-bipyridine (BIPY) and malonic acid (MA) cocrystal (BIPYMA) that allow the conversion of the cocrystal phase into ionic salt polymorphs. On compression, neutral BIPYMA and monoprotonated (BIPYH+MA-) species coexist up to 3.1 GPa, where a phase transition to a structure of P21/c symmetry occurs, induced by a double proton-transfer reaction forming BIPYH22+MA2-. The low-pressure C2/c phase is recovered at 2.4 GPa on decompression, leading to a 0.7 GPa hysteresis pressure range. This is one of a few studies on proton transfer in multicomponent crystals that shows how susceptible the interconversion between differently charged species is to even slight pressure changes, and how the proton transfer can be a triggering factor leading to changes in the crystal symmetry. These new data, coupled with information from previous reports on proton-transfer reactions between coformers, extend the applicability of the ΔpKa rule incorporating the pressure required to induce salt formation.
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Affiliation(s)
- Ewa Patyk-Kaźmierczak
- Facuty of Chemistry, Adam Mickiewicz University in Poznań, Uniwersytetu Poznańskiego 8, Poznań 61-614, Poland
| | - Fernando Izquierdo-Ruiz
- MALTA-Consolider Team and Departamento de Química Física, University Complutense of Madrid, Avda. de Séneca, 2 Ciudad Universitaria, Madrid 28040, Spain
| | - Alvaro Lobato
- MALTA-Consolider Team and Departamento de Química Física, University Complutense of Madrid, Avda. de Séneca, 2 Ciudad Universitaria, Madrid 28040, Spain
| | - Michał Kaźmierczak
- Facuty of Chemistry, Adam Mickiewicz University in Poznań, Uniwersytetu Poznańskiego 8, Poznań 61-614, Poland
| | - Ida Moszczyńska
- Facuty of Chemistry, Adam Mickiewicz University in Poznań, Uniwersytetu Poznańskiego 8, Poznań 61-614, Poland
| | - Anna Olejniczak
- Facuty of Chemistry, Adam Mickiewicz University in Poznań, Uniwersytetu Poznańskiego 8, Poznań 61-614, Poland
| | - J. Manuel Recio
- MALTA-Consolider Team and Departamento de Química Física y Analítica, University of Oviedo, Julián Clavería n° 8, Oviedo 33006, Spain
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6
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Precupas A, Popa VT. Impact of Sinapic Acid on Bovine Serum Albumin Thermal Stability. Int J Mol Sci 2024; 25:936. [PMID: 38256010 PMCID: PMC10815719 DOI: 10.3390/ijms25020936] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2023] [Revised: 01/09/2024] [Accepted: 01/10/2024] [Indexed: 01/24/2024] Open
Abstract
The thermal stability of bovine serum albumin (BSA) in Tris buffer, as well as the effect of sinapic acid (SA) on protein conformation were investigated via calorimetric (differential scanning microcalorimetry-μDSC), spectroscopic (dynamic light scattering-DLS; circular dichroism-CD), and molecular docking approaches. μDSC data revealed both the denaturation (endotherm) and aggregation (exotherm) of the protein, demonstrating the dual effect of SA on protein thermal stability. With an increase in ligand concentration, (i) protein denaturation shifts to a higher temperature (indicating native form stabilization), while (ii) the aggregation process shifts to a lower temperature (indicating enhanced reactivity of the denatured form). The stabilization effect of SA on the native structure of the protein was supported by CD results. High temperature (338 K) incubation induced protein unfolding and aggregation, and increasing the concentration of SA altered the size distribution of the protein population, as DLS measurements demonstrated. Complementary information offered by molecular docking allowed for the assessment of the ligand binding within the Sudlow's site I of the protein. The deeper insight into the SA-BSA interaction offered by the present study may serve in the clarification of ligand pharmacokinetics and pharmacodynamics, thus opening paths for future research and therapeutic applications.
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Affiliation(s)
| | - Vlad Tudor Popa
- “Ilie Murgulescu” Institute of Physical Chemistry, Romanian Academy, Splaiul Independentei 202, 060021 Bucharest, Romania;
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7
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Sit I, Fashina BT, Baldo AP, Leung K, Grassian VH, Ilgen AG. Formic and acetic acid p Ka values increase under nanoconfinement. RSC Adv 2023; 13:23147-23157. [PMID: 37533784 PMCID: PMC10390803 DOI: 10.1039/d2ra07944e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2022] [Accepted: 06/22/2023] [Indexed: 08/04/2023] Open
Abstract
Organic acids are prevalent in the environment and their acidity and the corresponding dissociation constants can change under varying environmental conditions. The impact of nanoconfinement (when acids are confined within nanometer-scale domains) on physicochemical properties of chemical species is poorly understood and is an emerging field of study. By combining infrared and Raman spectroscopies with molecular dynamics (MD) simulations, we quantified the effect of nanoconfinement in silica nanopores on one of the fundamental chemical reactions-the dissociation of organic acids. The pKa of formic and acetic acids confined within cylindrical silica nanopores with 4 nm diameters were measured. MD models were constructed to calculate the shifts in the pKa values of acetic acid nanoconfined within 1, 2, 3, and 4 nm silica slit pores. Both experiments and MD models indicate a decrease in the apparent acid dissociation constants (i.e., increase in the pKa values) when organic acids are nanoconfined. Therefore, nanoconfinement stabilizes the protonated species. We attribute this observation to (1) a decrease in the average dielectric response of nanoconfined aqueous solutions where charge screening may be decreased; or (2) an increase in proton concentration inside nanopores, which would shift the equilibrium towards the protonated form. Overall, the results of this study provide the first quantification of the pKa values for nanoconfined formic and acetic acids and pave the way for a unifying theory predicting the impact of nanoconfinement on acid-base chemistry.
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Affiliation(s)
- Izaac Sit
- Department of Nanoengineering, University of California San Diego La Jolla CA 92093 USA
| | - Bidemi T Fashina
- Geochemistry Department, Sandia National Laboratories Albuquerque NM 87123 USA
| | - Anthony P Baldo
- Geochemistry Department, Sandia National Laboratories Albuquerque NM 87123 USA
| | - Kevin Leung
- Geochemistry Department, Sandia National Laboratories Albuquerque NM 87123 USA
| | - Vicki H Grassian
- Department of Chemistry & Biochemistry, University of California San Diego La Jolla CA 92093 USA
| | - Anastasia G Ilgen
- Geochemistry Department, Sandia National Laboratories Albuquerque NM 87123 USA
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8
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Walton-Raaby M, Floen T, García-Díez G, Mora-Diez N. Calculating the Aqueous pK a of Phenols: Predictions for Antioxidants and Cannabinoids. Antioxidants (Basel) 2023; 12:1420. [PMID: 37507958 PMCID: PMC10376140 DOI: 10.3390/antiox12071420] [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: 05/30/2023] [Revised: 06/30/2023] [Accepted: 07/10/2023] [Indexed: 07/30/2023] Open
Abstract
We aim to develop a theoretical methodology for the accurate aqueous pKa prediction of structurally complex phenolic antioxidants and cannabinoids. In this study, five functionals (M06-2X, B3LYP, BHandHLYP, PBE0, and TPSS) and two solvent models (SMD and PCM) were combined with the 6-311++G(d,p) basis set to predict pKa values for twenty structurally simple phenols. None of the direct calculations produced good results. However, the correlations between the calculated Gibbs energy difference of each acid and its conjugate base, ΔGaq(BA)°=ΔGaqA-°-ΔGaq(HA)°, and the experimental aqueous pKa values had superior predictive accuracy, which was also tested relative to an independent set of ten molecules of which six were structurally complex phenols. New correlations were built with twenty-seven phenols (including the phenols with experimental pKa values from the test set), which were used to make predictions. The best correlation equations used the PCM method and produced mean absolute errors of 0.26-0.27 pKa units and R2 values of 0.957-0.960. The average range of predictions for the potential antioxidants (cannabinoids) was 0.15 (0.25) pKa units, which indicates good agreement between our methodologies. The new correlation equations could be used to make pKa predictions for other phenols in water and potentially in other solvents where they might be more soluble.
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Affiliation(s)
- Max Walton-Raaby
- Department of Chemistry, Thompson Rivers University, Kamloops, BC V2C 0C8, Canada
- Department of Chemistry, University of Waterloo, Waterloo, ON N2L 3G1, Canada
| | - Tyler Floen
- Department of Chemistry, Thompson Rivers University, Kamloops, BC V2C 0C8, Canada
| | | | - Nelaine Mora-Diez
- Department of Chemistry, Thompson Rivers University, Kamloops, BC V2C 0C8, Canada
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9
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Das S, Mussel M. Characterizing Oscillatory and Excitability Regimes in a Protein-Free Lipid Membrane. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2023; 39:5752-5760. [PMID: 37058369 DOI: 10.1021/acs.langmuir.2c03495] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Observations of electric potential oscillations in artificial lipid bilayers near the order-disorder transition indicate the existence of a stable limit cycle and, therefore, the possibility of producing excitable signals close to the bifurcation. We present a theoretical investigation of membrane oscillatory and excitability regimes induced by an increase in ion permeability at the order-disorder transition. The model accounts for the coupled effects of state-dependent permeability, membrane charge density, and hydrogen ion adsorption. A bifurcation diagram shows a transition between fixed-point and limit cycle solutions, enabling both oscillatory and excitability responses at different values of the acid association parameter. Oscillations are identified in terms of the membrane state, electric potential difference, and ion concentration near the membrane. The emerging voltage and time scales agree with measurements. Excitability is demonstrated by applying an external electric current stimulus, and the emerging signals display a threshold response and the appearance of repetitive signals upon using a long-lasting stimulus. The approach highlights the important role of the order-disorder transition, enabling membrane excitability in the absence of specialized proteins.
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Affiliation(s)
- Sandip Das
- Department of Physics, University of Haifa, 199 Aba Khoushy Avenue, Haifa 3498838, Israel
| | - Matan Mussel
- Department of Physics, University of Haifa, 199 Aba Khoushy Avenue, Haifa 3498838, Israel
- Center for Biophysics and Quantitative Biology, University of Haifa, 199 Aba Khoushy Avenue, Haifa 3498838, Israel
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10
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Han GE, Priefer R. A systematic review of various pK a determination techniques. Int J Pharm 2023; 635:122783. [PMID: 36858133 DOI: 10.1016/j.ijpharm.2023.122783] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2022] [Revised: 02/19/2023] [Accepted: 02/23/2023] [Indexed: 03/02/2023]
Abstract
The pKa values of functional groups is crucial in determining the pharmacokinetic properties of a drug, affecting its absorption and thus bioavailability. This physicochemical property is also vital for the designing of drug excipients and vehicles. There are currently 13 known methods of determining a pKa value, namely: potentiometric titration, spectrometry, fluorometry, NMR, HPLC, conductometry, electrophoresis, voltammetry, solubility, partition coefficient, calorimetry, computational, and surface tension. Some of these techniques are more widely utilized and well-established compared to others, with each having their inherent advantages and disadvantages. This review discusses each of the aforementioned techniques with emphasis on their pros and cons.
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Affiliation(s)
- Gi Eun Han
- Massachusetts College of Pharmacy and Health Sciences, Boston, MA, United States
| | - Ronny Priefer
- Massachusetts College of Pharmacy and Health Sciences, Boston, MA, United States.
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11
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Kim SE, Hong SC. Two Opposing Effects of Monovalent Cations on the Stability of i-Motif Structure. J Phys Chem B 2023; 127:1932-1939. [PMID: 36811958 DOI: 10.1021/acs.jpcb.2c07069] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/24/2023]
Abstract
At acidic pH, cytosine-rich single-stranded DNA can be folded into a tetraplex structure called i-motif (iM). In recent studies, the effect of monovalent cations on the stability of iM structure has been addressed, but a consensus about the issue has not been reached yet. Thus, we investigated the effects of various factors on the stability of iM structure using fluorescence resonance energy transfer (FRET)-based analysis for three types of iM derived from human telomere sequences. We confirmed that the protonated cytosine-cytosine (C:C+) base pair is destabilized as the concentration of monovalent cations (Li+, Na+, K+) increases and that Li+ has the greatest tendency of destabilization. Intriguingly, monovalent cations would play an ambivalent role in iM formation by making single-stranded DNA flexible and pliant for an iM structure. In particular, we found that Li+ has a notably greater flexibilizing effect than Na+ and K+. All taken together, we conclude that the stability of iM structure is controlled by the subtle balance of the two counteractive effects of monovalent cations: electrostatic screening and disruption of cytosine base pairing.
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Affiliation(s)
- Sung Eun Kim
- Center for Molecular Spectroscopy and Dynamics, Institute for Basic Science, Seoul, Korea, Department of Physics, Korea University, Seoul 02841, Korea
| | - Seok-Cheol Hong
- Center for Molecular Spectroscopy and Dynamics, Institute for Basic Science, Seoul, Korea, Department of Physics, Korea University, Seoul 02841, Korea
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12
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Gashe F, Wynendaele E, De Spiegeleer B, Suleman S. Degradation kinetics of artesunate for the development of an ex-tempore intravenous injection. Malar J 2022; 21:256. [PMID: 36068561 PMCID: PMC9450271 DOI: 10.1186/s12936-022-04278-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2022] [Accepted: 08/24/2022] [Indexed: 11/10/2022] Open
Abstract
Background Artesunate is recommended by the World Health Organization (WHO) for parenteral treatment of severe Plasmodium falciparum malaria. However, artesunate is inherently unstable in an aqueous solution and hydrolyses rapidly after its preparation for injection. Therefore, the aim of the study was to evaluate the stabilizing effects of phosphate buffer and mannitol against short-term (ex-tempore) artesunate hydrolysis. Methods A HPLC–UV isocratic method was developed using a reversed-phase fused core column (HALO RP-C18) and a mobile phase consisting of a mixture of 45% ammonium formate 10 mM in water (pH 4.5) and 55% methanol. Artesunate was formulated as aqueous solutions using a design of experiment (DOE) to investigate the artesunate stabilizing effects of pH (8–10), phosphate buffer strength (0.3–0.5 M), and mannitol (0–0.22 mmol/mL). The solutions were incubated at predefined temperatures (5, 25, and 40 °C) with subsequent analysis. Arrhenius equation was applied to model and evaluate the stability results. Results The developed HPLC-based method using fused-core stationary phase allowed to selectively quantify artesunate in the presence of its main hydrolysis degradants; namely β-dihydroartemisinin (β-DHA) and α-dihydroartemisinin (α-DHA) within 10 min. By applying the Arrhenius equation, the rate of hydrolysis of the drug increased approximately by 3.4 as the temperature raised by 10 °C. Buffer strength was found to be the main factor affecting the hydrolysis rate constants at 5 and 25 °C (p < 0.05), the activation energy (p = 0.009), and the frequency factor (p = 0.045). However, the effect of the buffer was predominant on the activation energy and hydrolysis rate constants, revealing its stabilizing effect on the drug at lower buffer strength (0.3 M). Within the investigated range (pH = 8–10), pH was found to influence the activation energy, with a positive stabilizing effect in the pH range of 8–9. The addition of mannitol as stabilizing agent into artesunate aqueous formulation did not show an improved response. Conclusion Phosphate buffer was the main stability determining factor of artesunate in the aqueous intravenous (i.v.) formulation and was found to be more effective in stabilizing artesunate at a buffer strength of 0.3 M in pH 8–9, while mannitol lacked stabilizing effect. Supplementary Information The online version contains supplementary material available at 10.1186/s12936-022-04278-4.
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Affiliation(s)
- Fanta Gashe
- Jimma University Laboratory of Drug Quality (JuLaDQ) and School of Pharmacy, Jimma University, PO Box 378, Jimma, Ethiopia.,Drug Quality and Registration (DruQuaR) Group, Faculty of Pharmaceutical Sciences, Ghent University, Harelbekestraat 72, 9000, Ghent, Belgium
| | - Evelien Wynendaele
- Drug Quality and Registration (DruQuaR) Group, Faculty of Pharmaceutical Sciences, Ghent University, Harelbekestraat 72, 9000, Ghent, Belgium
| | - Bart De Spiegeleer
- Drug Quality and Registration (DruQuaR) Group, Faculty of Pharmaceutical Sciences, Ghent University, Harelbekestraat 72, 9000, Ghent, Belgium
| | - Sultan Suleman
- Jimma University Laboratory of Drug Quality (JuLaDQ) and School of Pharmacy, Jimma University, PO Box 378, Jimma, Ethiopia.
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13
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Development of liquid chromatographic and UV-visible spectrophotometric methods for determination of pK a values of folic acid antimetabolites. J Pharm Biomed Anal 2022; 212:114647. [PMID: 35180566 DOI: 10.1016/j.jpba.2022.114647] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2021] [Revised: 02/02/2022] [Accepted: 02/04/2022] [Indexed: 11/20/2022]
Abstract
In this study, the values of ionization/protonation constants (pKa) of pemetrexed and raltitrexed, which are folic acid antimetabolites, were determined by reversed-phase liquid chromatography (RPLC) and UV-visible spectrophotometric methods at 25 °C. The pKass values were evaluated by retention time (tR) in binary acetonitrile-water mixtures with acetonitrile (ACN) contents of 13%, 15%, 17% and 20% (v/v) for the RPLC method and 13%, 15% and 17% (v/v) for the spectrophotometric method. The aqueous pKa values (pKaww) of the studied compounds were calculated from the pKass value using the macroscopic parameters (mole fraction and dielectric constant), which play an important role in solvent properties. In addition, the degree of ionization of pemetrexed and raltitrexed was calculated using the pKaww values.
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14
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Gollu G, Gummadi S. OUP accepted manuscript. J Chromatogr Sci 2022; 61:358-365. [PMID: 35152281 DOI: 10.1093/chromsci/bmac011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2021] [Revised: 12/15/2021] [Accepted: 01/20/2022] [Indexed: 11/13/2022]
Abstract
A simple, robust stability indicating RP-HPLC method was developed for simultaneous quantification of serdexmethyl phenidate and dexmethyl phenidate in a fixed capsule dosage form. This is the first method to be reported for simultaneous estimation and quantification of degradation products produced from forced stressing of the dosage form as per ICH guidelines. The chromatographic separation was attained on Waters X-terra C18 column using a mixture of trifluoro acetic acid and acetonitrile (70:30 v/v) as mobile phase with a flow rate of 1 mL, monitored at 265 nm over a run time of 10 min. Serdexmethyl phenidate and dexmethyl phenidate were eluted with retention times of 2.71 min and 7.33 min, respectively. The method displayed linear responses in the range of 4.2-63 μg/mL (0.9994) for serdexmethyl phenidate and 0.9 to 3.5 μg/mL (0.9998) for dexmethyl phenidate, respectively. The percentage recoveries of the two drugs were found within the acceptable limits. Forced degradation was conducted and showed considerable degradation in various stress conditions. It also confirms the specificity of the method as no interference peaks were observed concerning for to stress products. This method can be routinely used in quality control labs for simultaneous determination of respective drugs in marketed dosage form.
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Affiliation(s)
- Gowri Gollu
- Department of Pharmaceutical Analysis, Maharajah's College of Pharmacy, Phool Baugh, Vizianagaram, Andhra Pradesh 535002, India
| | - Sowjanya Gummadi
- Department of Pharmaceutical Analysis, GITAM Institute of Pharmacy, GITAM (Deemed to be University), Visakhapatnam, Andhra Pradesh 530045, India
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15
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Samuelsen L, Holm R, Schönbeck C. Simultaneous determination of cyclodextrin stability constants as a function of pH and temperature – A tool for drug formulation and process design. J Drug Deliv Sci Technol 2021. [DOI: 10.1016/j.jddst.2021.102675] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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16
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Rose HB, Wilber MM, Bommarius AS. Evaluation of ionic equilibria in mixed-buffer isothermal titration calorimetry and continuously stirred tank reactors. Int J Pharm 2020; 594:120170. [PMID: 33309829 DOI: 10.1016/j.ijpharm.2020.120170] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2020] [Revised: 11/18/2020] [Accepted: 12/07/2020] [Indexed: 12/01/2022]
Abstract
Determination of an equilibrium pH value in complex aqueous solution and deconvolution of this equilibrium to evaluate phenomena related to mixing, dilution, or progress of reaction is increasingly important in areas ranging from water quality to pharmaceutical formulations and manufacturing. Linearization of pH problems by simple algebraic substitution enables equilibria within complex buffered aqueous solutions to be modeled as an eigenvalue problem. This formulation approach makes rigorous determination of equilibrium pH values and reactor dynamics more accessible than with previous calculation methods, even when activity coefficients and non-ideality are considered. This work demonstrates how such calculations can enable detailed modeling of enthalpic changes in an isothermal titration calorimeter. In support of this work, the acid dissociation constants for three furancarboxylic acids (2-furancarboxylic acid, FA; 5-formyl-2-furancarboxylic acid, FFA; and 2,5-furandicarboxylic acid, FDCA), two of them novel, were determined and compared with multi-wavelength ultraviolet-visible spectrophotometry. The thermodynamic pKa values were determined to be 3.1 for FA, 2.2 for FFA, and 2.1 and 3.4 for the first and second ionization steps of FDCA, respectively.
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Affiliation(s)
- Harrison B Rose
- School of Chemical & Biomolecular Engineering, Krone Engineered Biosystems Building, Georgia Institute of Technology, Atlanta, GA 30332, United States
| | - Madison M Wilber
- School of Chemical & Biomolecular Engineering, Krone Engineered Biosystems Building, Georgia Institute of Technology, Atlanta, GA 30332, United States
| | - Andreas S Bommarius
- School of Chemical & Biomolecular Engineering, Krone Engineered Biosystems Building, Georgia Institute of Technology, Atlanta, GA 30332, United States; School of Chemistry & Biochemistry, Krone Engineered Biosystems Building, Georgia Institute of Technology, Atlanta, GA 30332, United States.
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17
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Azhari NR, Yahaya N, Mohd Suah FBM, Prabu S, Yih Hui B, Shahriman MS, Mohamad Zain NN, Raoov M. Enantioseparation of ketoconazole and miconazole by capillary electrophoresis and a study on their inclusion interactions with β-cyclodextrin and derivatives. Chirality 2020; 33:37-50. [PMID: 33197086 DOI: 10.1002/chir.23285] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2020] [Revised: 09/22/2020] [Accepted: 10/14/2020] [Indexed: 11/07/2022]
Abstract
A chiral separation method coupled with capillary electrophoresis (CE) analysis for ketoconazole and miconazole enantiomers using chiral selectors such as β-cyclodextrin (β-CD) and hydroxypropyl-β-CD (HP-β-CD) was developed in this study, which included the optimisation, validation and application of the method on the antifungal cream samples. The formation of inclusion complex between the hosts (β-CD and HP-β-CD) and guests (ketoconazole and miconazole) were compared and analysed using ultraviolet-visible spectrophotometry, nuclear magnetic resonance (NMR) spectroscopy and molecular docking methods. Results from the study showed that in a concentration that ranged between 0.25 and 50 mg L-1 , the linear calibration curves of each enantiomer had a high coefficient of regression (R2 > 0.999), low limit of detection (0.075 mg L-1 ) and low limit of quantification (0.25 mg L-1 ). The relative standard deviation (RSD) of the intraday and interday analyses ranged from 0.79% to 8.01% and 3.30% to 11.43%, respectively, while the recoveries ranged from 82.0% to 105.7% (RSD < 7%, n = 3). The most probable structure of the inclusion complexes was proposed based on the findings from the molecular docking studies conducted using the PatchDock server.
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Affiliation(s)
- Nurul Raihana Azhari
- Integrative Medicine Cluster, Advanced Medical and Dental Institute (AMDI), University of Science, Malaysia, Penang, Malaysia
| | - Noorfatimah Yahaya
- Integrative Medicine Cluster, Advanced Medical and Dental Institute (AMDI), University of Science, Malaysia, Penang, Malaysia
| | | | - Samikannu Prabu
- Department of Chemistry, Faculty of Science, University of Malaya, Kuala Lumpur, Malaysia
| | - Boon Yih Hui
- Malaysian Pharmaceutical Industries Sdn. Bhd, Penang, Malaysia
| | | | - Nur Nadhirah Mohamad Zain
- Integrative Medicine Cluster, Advanced Medical and Dental Institute (AMDI), University of Science, Malaysia, Penang, Malaysia
| | - Muggundha Raoov
- Department of Chemistry, Faculty of Science, University of Malaya, Kuala Lumpur, Malaysia
- Centre for Ionic Liquids, Department of Chemistry, Faculty of Science, University of Malaya, Kuala Lumpur, Malaysia
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18
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Certain carboxylic acid buffers can destabilize β-cyclodextrin complexes by competitive interaction. Int J Pharm 2020; 589:119774. [DOI: 10.1016/j.ijpharm.2020.119774] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2020] [Revised: 08/11/2020] [Accepted: 08/13/2020] [Indexed: 11/22/2022]
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19
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Samuelsen L, Holm R, Lathuile A, Schönbeck C. Determination of acidity constants for weak acids and bases by isothermal titration calorimetry. J Pharm Biomed Anal 2020; 184:113206. [PMID: 32126458 DOI: 10.1016/j.jpba.2020.113206] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2019] [Revised: 02/19/2020] [Accepted: 02/22/2020] [Indexed: 10/24/2022]
Abstract
The advantage of isothermal titration calorimetry (ITC) to determine the acid dissociation constant (pKa value) is the simultaneous determination of the binding constant and binding enthalpy, as well as being precise and easy to use. The pKa can be calculated from the binding constant, and the temperature dependency of the pKa can be calculated from the binding enthalpy. The use of ITC to study protonation reactions is less common compared to its more conventional use of studying macromolecules and ligands. Water will influence the equilibrium due to autoionization, meaning that both the conjugate base and acid will exist in the sample cell at the beginning of the experiment. These differences are accounted for by optimizing the theoretical model used to estimate the binding constant and binding enthalpy. Through simulations and experimental measurements, we show that ITC can be used to determine the pKa for ibuprofen, ascorbic acid, 2-morpholin-4-ylethanesulfonic acid and paracetamol. The pKa values were consistent with potentiometric or spectrophotometric determinations as well as literature values. Optimizing the theoretical model does not lead to an improved determination, so the "one set of sites" model is adequate for the determination of pKa values.
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Affiliation(s)
- Lisa Samuelsen
- Department of Science and Environment, Roskilde University, Universitetsvej 1, DK-4000 Roskilde, Denmark
| | - René Holm
- Department of Science and Environment, Roskilde University, Universitetsvej 1, DK-4000 Roskilde, Denmark; Drug Product Development, Janssen Research and Development, Johnson & Johnson, Turnhoutseweg 30, 2340 Beerse, Belgium.
| | - Audrey Lathuile
- Drug Product Development, Janssen Research and Development, Johnson & Johnson, Turnhoutseweg 30, 2340 Beerse, Belgium
| | - Christian Schönbeck
- Department of Science and Environment, Roskilde University, Universitetsvej 1, DK-4000 Roskilde, Denmark
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20
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Correlation between the stability constant and pH for β-cyclodextrin complexes. Int J Pharm 2019; 568:118523. [DOI: 10.1016/j.ijpharm.2019.118523] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2019] [Revised: 06/17/2019] [Accepted: 07/13/2019] [Indexed: 01/15/2023]
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