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Cordeiro MM, Filipe HAL, dos Santos P, Samelo J, Ramalho JPP, Loura LMS, Moreno MJ. Interaction of Hoechst 33342 with POPC Membranes at Different pH Values. Molecules 2023; 28:5640. [PMID: 37570608 PMCID: PMC10420284 DOI: 10.3390/molecules28155640] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2023] [Revised: 07/18/2023] [Accepted: 07/21/2023] [Indexed: 08/13/2023] Open
Abstract
Hoechst 33342 (H33342) is a fluorescent probe that is commonly used to stain the DNA of living cells. To do so, it needs to interact with and permeate through cell membranes, despite its high overall charge at physiological pH values. In this work, we address the effect of pH in the association of H33342 with lipid bilayers using a combined experimental and computational approach. The partition of H33342 to 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) lipid membranes was experimentally quantified using fluorescence spectroscopy and isothermal titration calorimetry (ITC) measurements. Quantum chemical calculations were performed to select the most stable isomer of H33342 for the overall charges 0, +1, and +2, expected to predominate across the 5 < pH < 10 range. The interaction of these isomers with POPC bilayers was then studied by both unrestrained and umbrella sampling molecular dynamics (MD) simulations. Both experimental results and computational free energy profiles indicate that the partition coefficient of H33342 displays a small variation over a wide pH range, not exceeding one order of magnitude. The enthalpy variation upon partition to the membrane suggests efficient hydrogen bonding between the probe and the lipid, namely, for the protonated +2 form, which was confirmed in the MD simulation studies. The relatively high lipophilicity obtained for the charged species contrasts with the decrease in their general hydrophobicity as estimated from octanol/water partition. This highlights the distinction between lipophilicity and hydrophobicity, as well as the importance of considering the association with lipid bilayers when predicting the affinity for biomembranes.
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Affiliation(s)
- Margarida M. Cordeiro
- Coimbra Chemistry Center, Institute of Molecular Sciences (CQC-IMS), University of Coimbra, 3004-535 Coimbra, Portugal; (M.M.C.); (H.A.L.F.); (J.S.)
- Department of Chemistry, Faculty of Sciences and Technology, University of Coimbra, 3004-535 Coimbra, Portugal
| | - Hugo A. L. Filipe
- Coimbra Chemistry Center, Institute of Molecular Sciences (CQC-IMS), University of Coimbra, 3004-535 Coimbra, Portugal; (M.M.C.); (H.A.L.F.); (J.S.)
- Polytechnic of Guarda, CPIRN-IPG—Center of Potential and Innovation of Natural Resources, 6300-559 Guarda, Portugal
| | - Patrícia dos Santos
- Coimbra Chemistry Center, Institute of Molecular Sciences (CQC-IMS), University of Coimbra, 3004-535 Coimbra, Portugal; (M.M.C.); (H.A.L.F.); (J.S.)
- Department of Chemistry, Faculty of Sciences and Technology, University of Coimbra, 3004-535 Coimbra, Portugal
| | - Jaime Samelo
- Coimbra Chemistry Center, Institute of Molecular Sciences (CQC-IMS), University of Coimbra, 3004-535 Coimbra, Portugal; (M.M.C.); (H.A.L.F.); (J.S.)
- Department of Chemistry, Faculty of Sciences and Technology, University of Coimbra, 3004-535 Coimbra, Portugal
| | - João P. Prates Ramalho
- LAQV, REQUIMTE, Hercules Laboratory, Department of Chemistry, School of Science and Technology, University of Évora, 7000-671 Évora, Portugal;
| | - Luís M. S. Loura
- Coimbra Chemistry Center, Institute of Molecular Sciences (CQC-IMS), University of Coimbra, 3004-535 Coimbra, Portugal; (M.M.C.); (H.A.L.F.); (J.S.)
- CNC—Center for Neuroscience and Cell Biology, University of Coimbra, 3004-535 Coimbra, Portugal
- Faculty of Pharmacy, University of Coimbra, 3000-548 Coimbra, Portugal
| | - Maria J. Moreno
- Coimbra Chemistry Center, Institute of Molecular Sciences (CQC-IMS), University of Coimbra, 3004-535 Coimbra, Portugal; (M.M.C.); (H.A.L.F.); (J.S.)
- Department of Chemistry, Faculty of Sciences and Technology, University of Coimbra, 3004-535 Coimbra, Portugal
- CNC—Center for Neuroscience and Cell Biology, University of Coimbra, 3004-535 Coimbra, Portugal
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Dimitrijevic D, Fabian E, Nicol B, Funk-Weyer D, Landsiedel R. Toward Realistic Dosimetry In Vitro: Determining Effective Concentrations of Test Substances in Cell Culture and Their Prediction by an In Silico Mass Balance Model. Chem Res Toxicol 2022; 35:1962-1973. [PMID: 36264934 PMCID: PMC9682521 DOI: 10.1021/acs.chemrestox.2c00128] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Nominal concentrations (CNom) in cell culture media are routinely used to define concentration-effect relationships in the in vitro toxicology. The actual concentration in the medium (CMedium) can be affected by adsorption processes, evaporation, or degradation of chemicals. Therefore, we measured the total and free concentration of 12 chemicals, covering a wide range of lipophilicity (log KOW -0.07-6.84), in the culture medium (CMedium) and cells (CCell) after incubation with Balb/c 3T3 cells for up to 48 h. Measured values were compared to predictions using an as yet unpublished in silico mass balance model that combined relevant equations from similar models published by others. The total CMedium for all chemicals except tamoxifen (TAM) were similar to the CNom. This was attributed to the cellular uptake of TAM and accumulation into lysosomes. The free (i.e., unbound) CMedium for the low/no protein binding chemicals were similar to the CNom, whereas values of all moderately to highly protein-bound chemicals were less than 30% of the CNom. Of the 12 chemicals, the two most hydrophilic chemicals, acetaminophen (APAP) and caffeine (CAF), were the only ones for which the CCell was the same as the CNom. The CCell for all other chemicals tended to increase over time and were all 2- to 274-fold higher than CNom. Measurements of CCytosol, using a digitonin method to release cytosol, compared well with CCell (using a freeze-thaw method) for four chemicals (CAF, APAP, FLU, and KET), indicating that both methods could be used. The mass balance model predicted the total CMedium within 30% of the measured values for 11 chemicals. The free CMedium of all 12 chemicals were predicted within 3-fold of the measured values. There was a poorer prediction of CCell values, with a median overprediction of 3- to 4-fold. In conclusion, while the number of chemicals in the study is limited, it demonstrates the large differences between CNom and total and free CMedium and CCell, which were also relatively well predicted by the mass balance model.
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Affiliation(s)
- Dunja Dimitrijevic
- Free
University of Berlin, Institute of Pharmacy, Pharmacology and Toxicology, Königin-Luise-Straße
2−4, 14195Berlin, Germany
| | - Eric Fabian
- BASF
SE, Experimental Toxicology and Ecology, Carl-Bosch-Straße 38, 67056Ludwigshafen am Rhein, Germany
| | - Beate Nicol
- Safety
& Environmental Assurance Centre, Unilever
U.K., Sharnbrook, MK44 ILQBedford, United Kingdom
| | - Dorothee Funk-Weyer
- BASF
SE, Experimental Toxicology and Ecology, Carl-Bosch-Straße 38, 67056Ludwigshafen am Rhein, Germany
| | - Robert Landsiedel
- Free
University of Berlin, Institute of Pharmacy, Pharmacology and Toxicology, Königin-Luise-Straße
2−4, 14195Berlin, Germany,BASF
SE, Experimental Toxicology and Ecology, Carl-Bosch-Straße 38, 67056Ludwigshafen am Rhein, Germany,. Fax: +49 621 60-58134
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Abstract
The study of enzyme kinetics in drug metabolism involves assessment of rates of metabolism and inhibitory potencies over a suitable concentration range. In all but the very simplest in vitro system, these drug concentrations can be influenced by a variety of nonspecific binding reservoirs that can reduce the available concentration to the enzyme system(s) under investigation. As a consequence, the apparent kinetic parameters, such as Km or Ki, that are derived can deviate from the true values. There are a number of sources of these nonspecific binding depots or barriers, including membrane permeation and partitioning, plasma or serum protein binding, and incubational binding. In the latter case, this includes binding to the assay apparatus as well as biological depots, depending on the characteristics of the in vitro matrix being used. Given the wide array of subcellular, cellular, and recombinant enzyme systems utilized in drug metabolism, each of these has different components which can influence the free drug concentration. The physicochemical properties of the test compound are also paramount in determining the influential factors in any deviation between true and apparent kinetic behavior. This chapter describes the underlying mechanisms determining the free drug concentration in vitro and how these factors can be accounted for in drug metabolism studies, illustrated with case studies from the literature.
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Affiliation(s)
- Nigel J Waters
- Preclinical Development, Black Diamond Therapeutics, Cambridge, MA, USA
| | - R Scott Obach
- Pharmacokinetics, Dynamics and Metabolism, Pfizer Inc, Groton, CT, USA
| | - Li Di
- Pharmacokinetics, Dynamics and Metabolism, Pfizer Inc, Groton, CT, USA
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Wood I, Fabian L, Moglioni A, Cabeça LF, de Paula E, Pickholz M. Combining nuclear magnetic resonance with molecular dynamics simulations to address sumatriptan interaction with model membranes. Chem Phys Lipids 2019; 225:104792. [DOI: 10.1016/j.chemphyslip.2019.104792] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2019] [Revised: 06/21/2019] [Accepted: 07/17/2019] [Indexed: 02/07/2023]
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Brehm M, Saddiq G, Watermann T, Sebastiani D. Influence of Small Fluorophilic and Lipophilic Organic Molecules on Dipalmitoylphosphatidylcholine Bilayers. J Phys Chem B 2017; 121:8311-8321. [DOI: 10.1021/acs.jpcb.7b06520] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Affiliation(s)
- Martin Brehm
- Institut für Chemie—Theoretische
Chemie, Martin-Luther-Universität Halle-Wittenberg, Von-Danckelmann-Platz 4, 06120 Halle (Saale), Germany
| | - Ghulam Saddiq
- Institut für Chemie—Theoretische
Chemie, Martin-Luther-Universität Halle-Wittenberg, Von-Danckelmann-Platz 4, 06120 Halle (Saale), Germany
| | - Tobias Watermann
- Institut für Chemie—Theoretische
Chemie, Martin-Luther-Universität Halle-Wittenberg, Von-Danckelmann-Platz 4, 06120 Halle (Saale), Germany
| | - Daniel Sebastiani
- Institut für Chemie—Theoretische
Chemie, Martin-Luther-Universität Halle-Wittenberg, Von-Danckelmann-Platz 4, 06120 Halle (Saale), Germany
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Timmer N, Droge STJ. Sorption of Cationic Surfactants to Artificial Cell Membranes: Comparing Phospholipid Bilayers with Monolayer Coatings and Molecular Simulations. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2017; 51:2890-2898. [PMID: 28187261 PMCID: PMC5343551 DOI: 10.1021/acs.est.6b05662] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
This study reports the distribution coefficient between phospholipid bilayer membranes and phosphate buffered saline (PBS) medium (DMW,PBS) for 19 cationic surfactants. The method used a sorbent dilution series with solid supported lipid membranes (SSLMs). The existing SSLM protocol, applying a 96 well plate setup, was adapted to use 1.5 mL glass autosampler vials instead, which facilitated sampling and circumvented several confounding loss processes for some of the cationic surfactants. About 1% of the phospholipids were found to be detached from the SSLM beads, resulting in nonlinear sorption isotherms for compounds with log DMW values above 4. Renewal of the medium resulted in linear sorption isotherms. DMW values determined at pH 5.4 demonstrated that cationic surfactant species account for the observed DMW,PBS. Log DMW,PBS values above 5.5 are only experimentally feasible with lower LC-MS/MS detection limits and/or concentrated extracts of the aqueous samples. Based on the number of carbon atoms, dialkylamines showed a considerably lower sorption affinity than linear alkylamine analogues. These SSLM results closely overlapped with measurements on a chromatographic tool based on immobilized artificial membranes (IAM-HPLC) and with quantum-chemistry based calculations with COSMOmic. The SSLM data suggest that IAM-HPLC underestimates the DMW of ionized primary and secondary alkylamines by 0.8 and 0.5 log units, respectively.
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7
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Wood I, Pickholz M. Naratriptan aggregation in lipid bilayers: perspectives from molecular dynamics simulations. J Mol Model 2016; 22:221. [PMID: 27558798 DOI: 10.1007/s00894-016-3096-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2016] [Accepted: 08/08/2016] [Indexed: 11/27/2022]
Abstract
In order to understand the interaction between naratriptan and a fully hydrated bilayer of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphatidyl-choline (POPC), we carried out molecular dynamics simulations. The simulations were performed considering neutral and protonated ionization states, starting from different initial conditions. At physiological pH, the protonated state of naratriptan is predominant. It is expected that neutral compounds could have larger membrane partition than charged compounds. However, for the specific case of triptans, it is difficult to study neutral species in membranes experimentally, making computer simulations an interesting tool. When the naratriptan molecules were originally placed in water, they partitioned between the bilayer/water interface and water phase, as has been described for similar compounds. From this condition, the drugs displayed low access to the hydrophobic environment, with no significant effects on bilayer organization. The molecules anchored in the interface, due mainly to the barrier function of the polar and oriented lipid heads. On the other hand, when placed inside the bilayer, both neutral and protonated naratriptan showed self-aggregation in the lipid tail environment. In particular, the protonated species exhibited a pore-like structure, dragging water through this environment. Graphical Abstract Different behaviour of Naratriptan and Sumatriptan, when the drugs were originally placed in the lipid core.
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Affiliation(s)
- Irene Wood
- Instituto de Nanobiotecnología (NANOBIOTEC), Universidad de Buenos Aires, CONICET, Junin 956 CP 1113, Buenos Aires, Argentina.,National Science Research Council (CONICET), Buenos Aires, Argentina
| | - Mónica Pickholz
- Instituto de Nanobiotecnología (NANOBIOTEC), Universidad de Buenos Aires, CONICET, Junin 956 CP 1113, Buenos Aires, Argentina. .,National Science Research Council (CONICET), Buenos Aires, Argentina.
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8
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Waters NJ, Obach RS, Di L. Consideration of the unbound drug concentration in enzyme kinetics. Methods Mol Biol 2014; 1113:119-45. [PMID: 24523111 DOI: 10.1007/978-1-62703-758-7_7] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/08/2022]
Abstract
The study of enzyme kinetics in drug metabolism involves assessment of rates of metabolism and inhibitory potencies over a suitable concentration range. In all but the very simplest in vitro system, these drug concentrations can be influenced by a variety of nonspecific binding reservoirs that can reduce the available concentration to the enzyme system under investigation. As a consequence, the apparent kinetic parameters that are derived, such as K m or K i, can deviate from the true values. There are a number of sources of these nonspecific binding depots or barriers, including membrane permeation and partitioning, plasma or serum protein binding, and incubational binding. In the latter case, this includes binding to the assay apparatus, as well as biological depots, depending on the characteristics of the in vitro matrix being used. Given the wide array of subcellular, cellular, and recombinant enzyme systems utilized in drug metabolism, each of these has different components that can influence the free drug concentration. The physicochemical properties of the test compound are also paramount in determining the influential factors in any deviation between true and apparent kinetic behavior. This chapter describes the underlying mechanisms determining the free drug concentration in vitro and how these factors can be accounted for in drug metabolism studies, illustrated with case studies from the literature.
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Affiliation(s)
- Nigel J Waters
- Drug Metabolism and Pharmacokinetics, Epizyme Inc., Cambridge, MA, USA
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9
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Huang D, Zhao T, Xu W, Yang T, Cremer PS. Sensing small molecule interactions with lipid membranes by local pH modulation. Anal Chem 2013; 85:10240-8. [PMID: 24152205 DOI: 10.1021/ac401955t] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Herein, we utilized a label-free sensing platform based on pH modulation to detect the interactions between tetracaine, a positively charged small molecule used as a local anesthetic, and planar supported lipid bilayers (SLBs). The SLBs were patterned inside a flow cell, allowing for various concentrations of tetracaine to be introduced over the surface in a buffer solution. Studies with membranes containing POPC (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine) yielded an equilibrium dissociation constant value of Kd = 180 ± 47 μm for this small molecule-membrane interaction. Adding cholesterol to the SLBs decreased the affinity between tetracaine and the bilayers, while this interaction tightened when POPE (1-hexadecanoyl-2-(9-Z-octadecenoyl)-sn-glycero-3-phosphoethanolamine) was added. Studies were also conducted with three negatively charged membrane lipids, POPG (1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-(1'-rac-glycerol) (sodium salt)), POPS (1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-l-serine (sodium salt)), and ganglioside GM1. All three measurements gave rise to a similar tightening of the apparent Kd value compared with pure POPC membranes. The lack of chemical specificity with the identity of the negatively charged lipid indicated that the tightening was largely electrostatic. Through a direct comparison with ITC measurements, it was found that the pH modulation sensor platform offers a facile, inexpensive, highly sensitive, and rapid method for the detection of interactions between putative drug candidates and lipid bilayers. As such, this technique may potentially be exploited as a screen for drug development and analysis.
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Affiliation(s)
- Da Huang
- Department of Chemistry and §Department of Biochemistry and Molecular Biology, Penn State University , University Park, PA 16802
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10
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Sreekanth V, Bansal S, Motiani RK, Kundu S, Muppu SK, Majumdar TD, Panjamurthy K, Sengupta S, Bajaj A. Design, synthesis, and mechanistic investigations of bile acid-tamoxifen conjugates for breast cancer therapy. Bioconjug Chem 2013; 24:1468-84. [PMID: 23909664 DOI: 10.1021/bc300664k] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
We have synthesized two series of bile acid tamoxifen conjugates using three bile acids lithocholic acid (LCA), deoxycholic acid (DCA), and cholic acid (CA). These bile acid-tamoxifen conjugates possess 1, 2, and 3 tamoxifen molecules attached to hydroxyl groups of bile acids having free acid and amine functionalities at the tail region of bile acids. The in vitro anticancer activities of these bile acid-tamoxifen conjugates show that the free amine headgroup based cholic acid-tamoxifen conjugate (CA-Tam3-Am) is the most potent anticancer conjugate as compared to the parent drug tamoxifen and other acid and amine headgroup based bile acid-tamoxifen conjugates. The cholic acid-tamoxifen conjugate (CA-Tam3-Am) bearing three tamoxifen molecules shows enhanced anticancer activities in both estrogen receptor +ve and estrogen receptor -ve breast cancer cell lines. The enhanced anticancer activity of CA-Tam3-Am is due to more favorable irreversible electrostatic interactions followed by intercalation of these conjugates in hydrophobic core of membrane lipids causing increase in membrane fluidity. Annexin-FITC based FACS analysis showed that cells undergo apoptosis, and cell cycle analysis showed the arrest of cells in sub G0 phase. ROS assays showed a high amount of generation of ROS independent of ER status of the cell line indicating changes in mitochondrial membrane fluidity upon the uptake of the conjugate that further leads to the release of cytochrome c, a direct and indirect regulator of ROS. The mechanistic studies for apoptosis using PCR and western analysis showed apoptotsis by intrinsic and extrinsic pathways in ER +ve MCF-7 cells and by only an intrinsic pathway in ER -ve cells. In vivo studies in the 4T1 tumor model showed that CA-Tam3-Am is more potent than tamoxifen. These studies showed that bile acids provide a new scaffold for high drug loading and that their anticancer activities strongly depend on charge and hydrophobicity of lipid-drug conjugates.
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Affiliation(s)
- Vedagopuram Sreekanth
- The Laboratory of Nanotechnology and Chemical Biology, Regional Centre for Biotechnology , 180 Udyog Vihar, Phase 1, Gurgaon-122016, Haryana, India
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Bilayer Composition, Temperature, Speciation Effects and the Role of Bilayer Chain Ordering on Partitioning of Dexamethasone and its 21-Phosphate. Pharm Res 2013; 30:3154-69. [DOI: 10.1007/s11095-013-1143-z] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2013] [Accepted: 07/01/2013] [Indexed: 10/26/2022]
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Cousido-Siah A, Petrova T, Hazemann I, Mitschler A, Ruiz FX, Howard E, Ginell S, Atmanene C, Van Dorsselaer A, Sanglier-Cianférani S, Joachimiak A, Podjarny A. Crystal packing modifies ligand binding affinity: the case of aldose reductase. Proteins 2012; 80:2552-61. [PMID: 22752989 DOI: 10.1002/prot.24136] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2012] [Revised: 06/05/2012] [Accepted: 06/13/2012] [Indexed: 01/06/2023]
Abstract
The relationship between the structures of protein-ligand complexes existing in the crystal and in solution, essential in the case of fragment-based screening by X-ray crystallography (FBS-X), has been often an object of controversy. To address this question, simultaneous co-crystallization and soaking of two inhibitors with different ratios, Fidarestat (FID; K(d) = 6.5 nM) and IDD594 (594; K(d) = 61 nM), which bind to h-aldose reductase (AR), have been performed. The subatomic resolution of the crystal structures allows the differentiation of both inhibitors, even when the structures are almost superposed. We have determined the occupation ratio in solution by mass spectrometry (MS) Occ(FID)/Occ(594) = 2.7 and by X-ray crystallography Occ(FID)/Occ(594) = 0.6. The occupancies in the crystal and in solution differ 4.6 times, implying that ligand binding potency is influenced by crystal contacts. A structural analysis shows that the Loop A (residues 122-130), which is exposed to the solvent, is flexible in solution, and is involved in packing contacts within the crystal. Furthermore, inhibitor 594 contacts the base of Loop A, stabilizing it, while inhibitor FID does not. This is shown by the difference in B-factors of the Loop A between the AR-594 and AR-FID complexes. A stable loop diminishes the entropic energy barrier to binding, favoring 594 versus FID. Therefore, the effect of the crystal environment should be taken into consideration in the X-ray diffraction analysis of ligand binding to proteins. This conclusion highlights the need for additional methodologies in the case of FBS-X to validate this powerful screening technique, which is widely used.
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Affiliation(s)
- Alexandra Cousido-Siah
- Department of Integrative Biology, IGBMC, CNRS, INSERM, Université de Strasbourg, Illkirch, France
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Beattie D, Bradley M, Brearley A, Charlton SJ, Cuenoud BM, Fairhurst RA, Gedeck P, Gosling M, Janus D, Jones D, Lewis C, McCarthy C, Oakman H, Stringer R, Taylor RJ, Tuffnell A. A physical properties based approach for the exploration of a 4-hydroxybenzothiazolone series of β2-adrenoceptor agonists as inhaled long-acting bronchodilators. Bioorg Med Chem Lett 2010; 20:5302-7. [DOI: 10.1016/j.bmcl.2010.06.136] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2010] [Revised: 06/21/2010] [Accepted: 06/24/2010] [Indexed: 11/28/2022]
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Complexation between amine- and hydroxyl-terminated PAMAM dendrimers and sodium dodecyl sulfate. Colloids Surf A Physicochem Eng Asp 2010. [DOI: 10.1016/j.colsurfa.2010.04.029] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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15
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Ojogun V, Vyas SM, Lehmler HJ, Knutson BL. Partitioning of homologous nicotinic acid ester prodrugs (nicotinates) into dipalmitoylphosphatidylcholine (DPPC) membrane bilayers. Colloids Surf B Biointerfaces 2010; 78:75-84. [PMID: 20227859 PMCID: PMC2873030 DOI: 10.1016/j.colsurfb.2010.02.015] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2010] [Revised: 02/09/2010] [Accepted: 02/11/2010] [Indexed: 11/30/2022]
Abstract
The partitioning behavior of a series of perhydrocarbon nicotinic acid esters (nicotinates) between aqueous solution and dipalmitoylphosphatidylcholine (DPPC) membrane bilayers is investigated as a function of increasing alkyl chain length. The hydrocarbon nicotinates represent putative prodrugs, derivatives of the polar drug nicotinic acid, whose functionalization provides the hydrophobic character necessary for pulmonary delivery in a hydrophobic, fluorocarbon solvent, such as perfluorooctyl bromide. Independent techniques of differential scanning calorimetry and 1,6-diphenyl-1,3,5-hexatriene (DPH) fluorescence anisotropy measurements are used to analyze the thermotropic phase behavior and lipid bilayer fluidity as a function of nicotinate concentration. At increasing concentrations of nicotinates over the DPPC mole fraction range examined (X(DPPC)=0.6-1.0), all the nicotinates (ethyl (C2H5); butyl (C4H9); hexyl (C6H13); and octyl (C8H17)) partition into the lipid bilayer at sufficient levels to eliminate the pretransition, and decrease and broaden the gel to fluid phase transition temperature. The concentration at which these effects occur is chain length-dependent; the shortest chain nicotinate, C2H5, elicits the least dramatic response. Similarly, the DPH anisotropy results demonstrate an alteration of the bilayer organization in the liposomes as a consequence of the chain length-dependent partitioning of the nicotinates into DPPC bilayers. The membrane partition coefficients (logarithm values), determined from the depressed bilayer phase transition temperatures, increase from 2.18 for C2H5 to 5.25 for C8H17. The DPPC membrane/water partitioning of the perhydrocarbon nicotinate series correlates with trends in the octanol/water partitioning of these solutes, suggesting that their incorporation into the bilayer is driven by increasing hydrophobicity.
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Affiliation(s)
- Vivian Ojogun
- Department of Chemical and Materials Engineering 177 Anderson Hall, University of Kentucky, Lexington, KY 40506-0046
| | - Sandhya M. Vyas
- Department of Occupational and Environmental Health, 100 Oakdale Campus, #124 IREH, University of Iowa, Iowa City, IA 52242-5000
| | - Hans-Joachim Lehmler
- Department of Occupational and Environmental Health, 100 Oakdale Campus, #124 IREH, University of Iowa, Iowa City, IA 52242-5000
| | - Barbara L Knutson
- Department of Chemical and Materials Engineering 177 Anderson Hall, University of Kentucky, Lexington, KY 40506-0046
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Howell BA, Chauhan A. Interaction of cationic drugs with liposomes. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2009; 25:12056-12065. [PMID: 19821620 DOI: 10.1021/la901644h] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Interactions between cationic drugs and anionic liposomes were studied by measuring binding of drugs and the effect of binding on liposome permeability. The measurements were analyzed in the context of a continuum model based on electrostatic interactions and a Langmuir isotherm. Experiments and modeling indicate that, although electrostatic interactions are important, the fraction of drug sequestered in the double-layer is negligible. The majority of drug enters the bilayer with the charged regions interacting with the charged lipid head groups and the lipophilic regions associated with the bilayer. The partitioning of the drug can be described by a Langmuir isotherm with the electrostatic interactions increasing the sublayer concentration of the drug. The binding isotherms are similar for all tricyclic antidepressants (TCA). Bupivacaine (BUP) binds significantly less compared to TCA because its structure is such that the charged region has minimal interactions with the lipid heads once the BUP molecule partitions inside the bilayer. Conversely, the TCAs are linear with distinct hydrophilic and lipophilic regions, allowing the lipophilic regions to lie inside the bilayer and the hydrophilic regions to protrude out. This conformation maximizes the permeability of the bilayer, leading to an increased release of a hydrophilic fluorescent dye from liposomes.
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Affiliation(s)
- Brett A Howell
- Department of Chemical Engineering, University of Florida, Gainesville, Florida 32611, USA
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Howell BA, Chauhan A. Binding of Imipramine, Dosulepin, and Opipramol to Liposomes for Overdose Treatment. J Pharm Sci 2009; 98:3718-29. [DOI: 10.1002/jps.21683] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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Scherrer RA, Donovan SF. Automated potentiometric titrations in KCl/water-saturated octanol: method for quantifying factors influencing ion-pair partitioning. Anal Chem 2009; 81:2768-78. [PMID: 19265385 PMCID: PMC2664611 DOI: 10.1021/ac802729k] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2008] [Accepted: 01/30/2009] [Indexed: 11/28/2022]
Abstract
The knowledge base of factors influencing ion pair partitioning is very sparse, primarily because of the difficulty in determining accurate log P(I) values of desirable low molecular weight (MW) reference compounds. We have developed a potentiometric titration procedure in KCl/water-saturated octanol that provides a link to log P(I) through the thermodynamic cycle of ionization and partitioning. These titrations have the advantage of being independent of the magnitude of log P, while maintaining a reproducibility of a few hundredths of a log P in the calculated difference between log P neutral and log P ion pair (diff (log P(N - I))). Simple model compounds can be used. The titration procedure is described in detail, along with a program for calculating pK(a)'' values incorporating the ionization of water in octanol. Hydrogen bonding and steric factors have a greater influence on ion pairs than they do on neutral species, yet these factors are missing from current programs used to calculate log P(I) and log D. In contrast to the common assumption that diff (log P(N - I)) is the same for all amines, they can actually vary more than 3 log units, as in our examples. A major factor affecting log P(I) is the ability of water and the counterion to approach the charge center. Bulky substituents near the charge center have a negative influence on log P(I). On the other hand, hydrogen bonding groups near the charge center have the opposite effect by lowering the free energy of the ion pair. The use of this titration method to determine substituent ion pair stabilization values (IPS) should bring about more accurate log D calculations and encourage species-specific QSAR involving log D(N) and log D(I). This work also brings attention to the fascinating world of nature's highly stabilized ion pairs.
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Elsayed MMA, Vierl U, Cevc G. Accurate potentiometric determination of lipid membrane-water partition coefficients and apparent dissociation constants of ionizable drugs: electrostatic corrections. Pharm Res 2009; 26:1332-43. [PMID: 19283456 DOI: 10.1007/s11095-009-9842-1] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2008] [Accepted: 01/26/2009] [Indexed: 11/25/2022]
Abstract
PURPOSE Potentiometric lipid membrane-water partition coefficient studies neglect electrostatic interactions to date; this leads to incorrect results. We herein show how to account properly for such interactions in potentiometric data analysis. MATERIALS AND METHODS We conducted potentiometric titration experiments to determine lipid membrane-water partition coefficients of four illustrative drugs, bupivacaine, diclofenac, ketoprofen and terbinafine. We then analyzed the results conventionally and with an improved analytical approach that considers Coulombic electrostatic interactions. RESULTS The new analytical approach delivers robust partition coefficient values. In contrast, the conventional data analysis yields apparent partition coefficients of the ionized drug forms that depend on experimental conditions (mainly the lipid-drug ratio and the bulk ionic strength). This is due to changing electrostatic effects originating either from bound drug and/or lipid charges. A membrane comprising 10 mol-% mono-charged molecules in a 150 mM (monovalent) electrolyte solution yields results that differ by a factor of 4 from uncharged membranes results. CONCLUSION Allowance for the Coulombic electrostatic interactions is a prerequisite for accurate and reliable determination of lipid membrane-water partition coefficients of ionizable drugs from potentiometric titration data. The same conclusion applies to all analytical methods involving drug binding to a surface.
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Nussio MR, Sykes MJ, Miners JO, Shapter JG. Characterisation of the binding of cationic amphiphilic drugs to phospholipid bilayers using surface plasmon resonance. ChemMedChem 2008; 2:366-73. [PMID: 17191292 DOI: 10.1002/cmdc.200600252] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The interactions of three cationic amphiphilic drugs (CPZ, AMI, PROP) with phospholipid vesicles comprising DOPC, DMPC, or DSPC were investigated using surface plasmon resonance (SPR). Responses for CAD concentrations in the range 15.625 to 1500 microM were measured. The greatest uptake by each phospholipid bilayer occurred with CPZ. Inclusion of CAD concentrations between 750 and 1500 microM provided evidence for a second nonsaturable binding process, which may arise from intercalation of the drugs within the lipid bilayer. CAD binding was additionally shown to be dependent on membrane fluidity. Responses were initially fitted over a concentration range of 15.625 to 500 microM using a model which incorporated terms for a saturable binding site. This yielded very poor values of K(D) and nonsensible values of saturation responses. Subsequently, responses were fit to the expression for a model which incorporated terms for both a saturable binding site and second nonsaturable site. Measurable binding affinities (K(D) values ranged from 170 to 814 microM) were obtained for DOPC and DMPC bilayers which are similar to values reported previously. This work demonstrates that SPR studies with synthetic phospholipid bilayers provide a potentially useful approach for characterising drug-membrane binding interactions and for providing insight into the processes that contribute to drug-membrane binding.
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Affiliation(s)
- Matthew R Nussio
- School of Chemistry, Physics and Earth Sciences, Flinders University, Sturt Road, Bedford Park, Adelaide, SA 5001, Australia
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Sykes MJ, Sorich MJ, Miners JO. Molecular modeling approaches for the prediction of the nonspecific binding of drugs to hepatic microsomes. J Chem Inf Model 2007; 46:2661-73. [PMID: 17125206 DOI: 10.1021/ci600221h] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Molecular modeling approaches for the prediction of the nonspecific binding of drugs to hepatic microsomes were examined using a published database of 56 compounds. Models generated were evaluated using an independent test set of 13 compounds. A pharmacophore approach identified structural features of drugs associated with nonspecific binding. A side-chain amino group and complementary hydrophobic domain were the principal features noted. The use of shape overlays, based on the pharmacophore, in conjunction with a chemical force field in the program ROCS, yielded discrimination between molecules classified as strong binders (experimental fraction unbound in microsomes<0.50) and those with a lower degree of binding (experimental fraction unbound in microsomes>0.50). In the initial data set of 56 molecules, 18 were classified as strong binders (on the basis of the above criteria), and all of those were recovered in the top 22 molecular hits from ROCS. Additionally, computationally generated values of log P were shown to provide a reasonable estimate of the fraction unbound in microsomes, providing the compounds were in their basic form at physiological pH.
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Affiliation(s)
- Matthew J Sykes
- Department of Clinical Pharmacology, Flinders University and Flinders Medical Centre, Adelaide, Australia.
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Wang C, Wyn-Jones E, Sidhu J, Tam KC. Supramolecular complex induced by the binding of sodium dodecyl sulfate to PAMAM dendrimers. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2007; 23:1635-9. [PMID: 17279639 DOI: 10.1021/la0625897] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
Isothermal titration calorimetry (ITC) and dynamic light scattering (DLS) were employed to study the spontaneous supramolecular complexation of amine terminated PAMAM dendrimer (G3[EDA] PAMAM-NH2) induced by the binding of an anionic surfactant, sodium dodecyl sulfate (SDS). At pH<or=2, SDS molecules bound to protonated amines on the outer rims of G3[EDA] PAMAM-NH2 driven by electrostatic interaction, which induced the formation of PAMAM/SDS supramolecular complex via hydrophobic association between bound SDS molecules. The complex with radius of approximately 37 nm was observed at SDS concentration as low as 0.02 mM (in 0.2 mM PAMAM). The size of the complex increased progressively with increasing SDS concentration and precipitated when the SDS concentration exceeded 15 mM. At pH of approximately 7.4, the formation of PAMAM/SDS complex was observed at higher SDS concentration (0.1 mM in 0.2 mM PAMAM), and it resolubilized with further increase of SDS concentration to approximately 18 mM due to weaker electrostatic interaction at higher pH. At pH>or=10, the electrostatic binding ceased because the deprotonated PAMAM dendrimer was uncharged, and hence the surfactant-induced supramolecular assembly could not be formed.
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Affiliation(s)
- Chang Wang
- Singapore-MIT Alliance, School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798
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Ababou A, Ladbury JE. Survey of the year 2005: literature on applications of isothermal titration calorimetry. J Mol Recognit 2007; 20:4-14. [PMID: 17006876 DOI: 10.1002/jmr.803] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Isothermal titration calorimetry (ITC) can provide a full thermodynamic characterization of an interaction. Its usage does not suffer from constraints of molecular size, shape or chemical constitution. Neither is there any need for chemical modification or attachment to solid support. This ease of use has made it an invaluable instrumental resource and led to its appearance in many laboratories. Despite this, the value of the thermodynamic parameterization has, only quite recently, become widely appreciated. Although our understanding of the correlation between thermodynamic data and structural details continues to be somewhat naïve, a large number of publications have begun to improve the situation. In this overview of the literature for 2005, we have attempted to highlight works of interest and novelty. Furthermore, we draw attention to those works which we feel have provided a route to better analysis and increased our ability to understand the meaning of thermodynamic change on binding.
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Affiliation(s)
- Adessamad Ababou
- Department of Biochemistry and Molecular Biology, University College London, Gower Street, London WC1E 6BT, UK
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