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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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Fearon AD, Stokes GY. Thermodynamics of Indomethacin Adsorption to Phospholipid Membranes. J Phys Chem B 2017; 121:10508-10518. [PMID: 29064244 DOI: 10.1021/acs.jpcb.7b08359] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Using second-harmonic generation, we directly monitored adsorption of indomethacin, a nonsteroidal anti-inflammatory drug, to supported lipid bilayers composed of phospholipids of varying phase, cholesterol content, and head group charge without the use of extrinsic labels at therapeutically relevant aqueous concentrations. Indomethacin adsorbed to gel-phase lipids with a high binding affinity, suggesting that like other arylacetic acid-containing drugs, it preferentially interacts with ordered lipid domains. We discovered that adsorption of indomethacin to gel-phase phospholipids was endothermic and entropically driven, whereas adsorption to fluid-phase phospholipids was exothermic and enthalpically driven. As temperature increased from 19 to 34 °C, binding affinities to gel-phase lipids increased by 7-fold but relative surface concentration decreased to one-fifth of the original value. We also compared our results to the entropies reported for indomethacin adsorbed to surfactant micelles, which are used in drug delivery systems, and assert that adsorbed water molecules in the phospholipid bilayer may be buried deeper into the acyl chains and less accessible for disruption. The thermodynamic studies reported here provide mechanistic insight into indomethacin interactions with mammalian plasma membranes in the gastrointestinal tract and inform studies of drug delivery, where indomethacin is commonly used as a prototypical, hydrophobic small-molecule drug.
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Affiliation(s)
- Amanda D Fearon
- Department of Chemistry and Biochemistry, Santa Clara University , 500 El Camino Real, Santa Clara, California 95053, United States
| | - Grace Y Stokes
- Department of Chemistry and Biochemistry, Santa Clara University , 500 El Camino Real, Santa Clara, California 95053, United States
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Antioxidant actions of flavonoids: Thermodynamic and kinetic analysis. Arch Biochem Biophys 2010; 501:23-30. [DOI: 10.1016/j.abb.2010.04.005] [Citation(s) in RCA: 159] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2010] [Revised: 04/05/2010] [Accepted: 04/07/2010] [Indexed: 11/15/2022]
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Sivakumar Swamy G, Ramanarayan K, Inamdar LS, Inamdar SR. Triacontanol and jasmonic acid differentially modulate the lipid organization as evidenced by the fluorescent probe behavior and 31P nuclear magnetic resonance shifts in model membranes. J Membr Biol 2009; 228:165-77. [PMID: 19418089 DOI: 10.1007/s00232-009-9169-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2009] [Accepted: 04/05/2009] [Indexed: 10/20/2022]
Abstract
Fluorescence resonance energy transfer (FRET), time-resolved fluorescence and anisotropy decays were determined in large unilamellar vesicles (LUVs) of egg phosphatidylcholine with the FRET pair N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)-1,2-dipalmitoyl-sn-glycero-3-phospho-ethanolamine as donor and lissamine rhodamine B 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine as acceptor, using 2-ps pulses from a Ti:sapphire laser on LUVs with incorporated plant growth regulators: triacontanol (TRIA) and jasmonic acid (JA). FRET efficiency, energy transfer rate, rotation correlation time, microviscosity, and diffusion coefficient of lateral diffusion of lipids were calculated from these results. It was observed that TRIA and JA differentially modulated all parameters studied. The effect of JA in such modulations was always partially reversed by TRIA. Also, the generalized polarization of laurdan fluorescence indicated that JA enhances the degree of hydration in lipid bilayers to a larger extent than does TRIA. Solid-state (31)P magic-angle spinning nuclear magnetic resonance spectra of LUVs showed two chemical shifts, at 0.009 and -11.988 ppm, at low temperatures (20 degrees C), while at increasing temperatures (20-60 degrees C) only one (at -11.988 ppm) was prominent and the other (0.009 ppm) gradually became obscure. However, LUVs with TRIA exhibited only one of the shifts at 0.353 ppm even at lower temperatures and JA did not affect the chemical shifts.
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Lygre H, Moe G, Nerdal W, Holmsen H. Interaction of articaine hydrochloride with prokaryotic membrane lipids. Acta Odontol Scand 2009; 67:1-7. [PMID: 18941950 DOI: 10.1080/00016350802443466] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
OBJECTIVE Local anesthetics are the most commonly used drugs in dentistry, with a wide range of effects, including antimicrobial activity. High antimicrobial effects have recently been reported on oral microbes from articaine hydrochloride, revealed by the minimum inhibitory concentration and minimal bactericidal concentration. Additionally, articaine has recently been used as an alkaline component in endodontic materials with a proposed antibacterial activity. However, the detailed mechanisms of action have not been discussed. MATERIAL AND METHODS We determined the Langmuir surface pressure/molecular area isotherms of prokaryotic lipid monolayers, as well as the phospholipid phase transitions, by employing differential scanning calorimetry on unilamellar prokaryotic liposomes (bilayers). RESULTS Articaine hydrochloride was found to interact with the prokaryotic membrane lipids in both monolayers and bilayers. An increase of the phospholipid molecular area of acidic glycerophospholipids as well as a decrease in phase transition temperature and enthalpy were found with increasing articaine hydrochloride concentration. The thermodynamic changes by adding articaine hydrochloride to prokaryotic membrane lipids are potentially related to the effects observed from antimicrobial peptides resulting from membrane insertion, aggregate composition, pore formation, and lysis. CONCLUSION Interaction of articaine hydrochloride with prokaryotic membrane lipids is indicated. Hence, further research is necessary to gain insight into where these compounds exert their effects at the molecular level.
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Nymeyer H, Woolf TB, Garcia AE. Folding is not required for bilayer insertion: replica exchange simulations of an alpha-helical peptide with an explicit lipid bilayer. Proteins 2006; 59:783-90. [PMID: 15828005 DOI: 10.1002/prot.20460] [Citation(s) in RCA: 94] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
We implement the replica exchange molecular dynamics algorithm to study the interactions of a model peptide (WALP-16) with an explicitly represented DPPC membrane bilayer. We observe the spontaneous, unbiased insertion of WALP-16 into the DPPC bilayer and its folding into an alpha-helix with a transbilayer orientation. The free energy surface suggests that the insertion of the peptide into the DPPC bilayer precedes secondary structure formation. Although the peptide has some propensity to form a partially helical structure in the interfacial region of the DPPC/water system, this state is not a productive intermediate but rather an off-pathway trap for WALP-16 insertion. Equilibrium simulations show that the observed insertion/folding pathway mirrors the potential of mean force (PMF). Calculation of the enthalpic and entropic contributions to this PMF show that the surface bound conformation of WALP-16 is significantly lower in energy than other conformations, and that the insertion of WALP-16 into the bilayer without regular secondary structure is enthalpically unfavorable by 5-10 kcal/mol/residue. The observed insertion/folding pathway disagrees with the dominant conceptual model, which is that a surface-bound helix is an obligatory intermediate for the insertion of alpha-helical peptides into lipid bilayers. In our simulations, the observed insertion/folding pathway is favored because of a large (>100 kcal/mol) increase in system entropy that occurs when the unstructured WALP-16 peptide enters the lipid bilayer interior. The insertion/folding pathway that is lowest in free energy depends sensitively on the near cancellation of large enthalpic and entropic terms. This suggests the possibility that intrinsic membrane peptides may have a diversity of insertion/folding behaviors depending on the exact system of peptide and lipid under consideration.
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Affiliation(s)
- Hugh Nymeyer
- Theoretical Biology & Biophysics Group, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
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Claydon TW, Makary SY, Dibb KM, Boyett MR. The Selectivity Filter May Act as the Agonist-activated Gate in the G Protein-activated Kir3.1/Kir3.4 K+ Channel. J Biol Chem 2003; 278:50654-63. [PMID: 14525972 DOI: 10.1074/jbc.m308183200] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The Kir3.1/Kir3.4 channel is activated by Gbetagamma subunits released on binding of acetylcholine to the M2 muscarinic receptor. A mechanism of channel opening, similar to that for the KcsA and Shaker K+ channels, has been suggested that involves translocation of pore lining transmembrane helices and the opening of an intracellular gate at the "bundle crossing" region. However, in the present study, we show that an extracellular gate at the selectivity filter is critical for agonist activation of the Kir3.1/Kir3.4 channel. Increasing the flexibility of the selectivity filter, by disrupting a salt bridge that lies directly behind the filter, abolished both selectivity for K+ and agonist activation of the channel. Other mutations within the filter that altered selectivity also altered agonist activation. In contrast, mutations within the filter that did not affect selectivity had little if any effect on agonist activation. Interestingly, mutation of bulky side chain phenylalanine residues at the bundle crossing also altered both agonist activation and selectivity. These results demonstrate a significant correlation between agonist activation and selectivity, which is determined by the selectivity filter, and suggests, therefore, that the selectivity filter may act as the agonist-activated gate in the Kir3.1/Kir3.4 channel.
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Affiliation(s)
- Thomas W Claydon
- School of Biomedical Sciences, University of Leeds, Leeds LS2 9JT, United Kingdom
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