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Socas LBP, Valdivia-Pérez JA, Fanani ML, Ambroggio EE. Multidimensional Spectral Phasors of LAURDAN's Excitation-Emission Matrices: The Ultimate Sensor for Lipid Phases? J Am Chem Soc 2024; 146:17230-17239. [PMID: 38874760 DOI: 10.1021/jacs.4c03443] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/15/2024]
Abstract
The impact of lipid diversity on the lateral organization of biological membranes remains a topic of debate. While the existence of domains in lamellar membranes is well-established, the nonlamellar phases occurring in biological systems are less explored due to technical constraints. Here, we present the measurement of the excitation-emission matrices (EEM) of LAURDAN in several lipid structures. LAURDAN is a fluorescence probe widely used for characterizing lipid assemblies. The EEMs were analyzed by multidimensional spectral phasors (MdSP), an approach that seizes information from both the excitation and emission spectra. We developed a computer algorithm to construct EEM data based on a model for LAURDAN's photophysics. The MdSP calculated from the simulated EEMs reveals that all feasible possibilities lie inside a universal triangle in the phasor's plot. We use this triangle to propose a ternary representation for the phasors, allowing a better assessment of LAURDAN's surroundings in terms of hydration, water mobility, and local electronic environment. Building upon this foundation, we constructed a theoretical "phase map" that can assess both lamellar and nonlamellar membranes. We thoroughly validated this theory using well-known lipid mixtures under different phase-state conditions and enzymatically generated systems. Our results confirm that the use of MdSP is a powerful tool for obtaining quantitative information on both lamellar and nonlamellar structures. This study not only advances our understanding of the impact of lipid diversity on membrane organization but also provides a robust and general framework for the assessment of fluorescence properties that can be further extended to other probes.
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Affiliation(s)
- Luis B P Socas
- Departamento de Química Biológica-Ranwel Caputto, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Haya de la Torre y Medina Allende s/n, Córdoba X5000HUA, Argentina
- Centro de Investigaciones en Química Biológica de Córdoba (CIQUIBIC), Universidad Nacional de Córdoba, CONICET, Haya de la Torre y Medina Allende s/n, Córdoba X5000HUA, Argentina
| | - Jessica A Valdivia-Pérez
- Departamento de Química Biológica-Ranwel Caputto, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Haya de la Torre y Medina Allende s/n, Córdoba X5000HUA, Argentina
- Centro de Investigaciones en Química Biológica de Córdoba (CIQUIBIC), Universidad Nacional de Córdoba, CONICET, Haya de la Torre y Medina Allende s/n, Córdoba X5000HUA, Argentina
| | - María L Fanani
- Departamento de Química Biológica-Ranwel Caputto, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Haya de la Torre y Medina Allende s/n, Córdoba X5000HUA, Argentina
- Centro de Investigaciones en Química Biológica de Córdoba (CIQUIBIC), Universidad Nacional de Córdoba, CONICET, Haya de la Torre y Medina Allende s/n, Córdoba X5000HUA, Argentina
| | - Ernesto E Ambroggio
- Departamento de Química Biológica-Ranwel Caputto, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Haya de la Torre y Medina Allende s/n, Córdoba X5000HUA, Argentina
- Centro de Investigaciones en Química Biológica de Córdoba (CIQUIBIC), Universidad Nacional de Córdoba, CONICET, Haya de la Torre y Medina Allende s/n, Córdoba X5000HUA, Argentina
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Suga K, Otsuka Y, Okamoto Y, Umakoshi H. Gel-Phase-like Ordered Membrane Properties Observed in Dispersed Oleic Acid/1-Oleoylglycerol Self-Assemblies: Systematic Characterization Using Raman Spectroscopy and a Laurdan Fluorescent Probe. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2018; 34:2081-2088. [PMID: 29309161 DOI: 10.1021/acs.langmuir.7b04044] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Aqueous dispersions of oleic acid (OA) and those modified with 1-oleoylglycerol (monoolein, MO) form various kinds of self-assembled structures: micelles, vesicles, oil-in-water (O/W) emulsions, hexagonal phases, and dispersed cubic phases. Conventionally, these self-assembled structures have been characterized using cryogenic transmission electron microscopy or X-ray diffraction spectroscopy. However, these methodologies require specialized treatment before they can be used, which may lead to the self-assemblies not adopting their true equilibrium state. Herein, we systematically characterized the self-assemblies composed of OA and MO in aqueous solution using Raman spectroscopy and fluorescent probe 6-dodecanoyl-2-dimethylaminonaphthalene (Laurdan). The OA/MO dispersions at pH 5.0 showed increased chain packing in comparison to the OA micelle at pH 11 or OA vesicle at pH 9.0, which were characterized by the intensity ratio of the Raman peaks at 2850 and 2890 cm-1, R = I2890/I2850. In the Laurdan fluorescence measurements, the obtained spectra were deconvoluted to two peak fractions (A1: λem= 490 nm; A2: λem = 440 nm), and the peak area ratio, A1/(A1 + A2), was defined as the membrane hydrophilicity Øm. The Øm value of the OA/MO dispersion at pH 5.0 was similar to that of the OA O/W emulsion, indicating that the membrane surfaces of these self-assemblies were relatively dehydrated compared to the OA micelle or OA vesicle. To categorize the type of self-assembly dispersion, a Cartesian diagram plot was systematically drawn: R on the x axis and Øm on the y axis, with the cross point at x = 1, y = 0.5. By comparing the membrane properties of the OA-based micelles, O/W emulsions, and dispersed cubic phases, we determined that the OA/MO dispersion at pH 5.0 possessed higher chain packing (R > 1) and a dehydrated membrane surface (Øm < 0.5), which is similar to that of the ordered membranes in gel phases. This characterization method can be useful in evaluating the ordered membrane properties in dispersed self-assemblies in aqueous media.
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Affiliation(s)
- Keishi Suga
- Division of Chemical Engineering, Graduate School of Engineering Science, Osaka University , 1-3 Machikaneyama-cho, Toyonaka, Osaka 560-8531, Japan
| | - Yoko Otsuka
- Division of Chemical Engineering, Graduate School of Engineering Science, Osaka University , 1-3 Machikaneyama-cho, Toyonaka, Osaka 560-8531, Japan
| | - Yukihiro Okamoto
- Division of Chemical Engineering, Graduate School of Engineering Science, Osaka University , 1-3 Machikaneyama-cho, Toyonaka, Osaka 560-8531, Japan
| | - Hiroshi Umakoshi
- Division of Chemical Engineering, Graduate School of Engineering Science, Osaka University , 1-3 Machikaneyama-cho, Toyonaka, Osaka 560-8531, Japan
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Vequi-Suplicy CC, Coutinho K, Lamy MT. Electric dipole moments of the fluorescent probes Prodan and Laurdan: experimental and theoretical evaluations. Biophys Rev 2014; 6:63-74. [PMID: 28509963 DOI: 10.1007/s12551-013-0129-8] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2013] [Accepted: 12/03/2013] [Indexed: 10/25/2022] Open
Abstract
Several experimental and theoretical approaches can be used for a comprehensive understanding of solvent effects on the electronic structure of solutes. In this review, we revisit the influence of solvents on the electronic structure of the fluorescent probes Prodan and Laurdan, focusing on their electric dipole moments. These biologically used probes were synthesized to be sensitive to the environment polarity. However, their solvent-dependent electronic structures are still a matter of discussion in the literature. The absorption and emission spectra of Prodan and Laurdan in different solvents indicate that the two probes have very similar electronic structures in both the ground and excited states. Theoretical calculations confirm that their electronic ground states are very much alike. In this review, we discuss the electric dipole moments of the ground and excited states calculated using the widely applied Lippert-Mataga equation, using both spherical and spheroid prolate cavities for the solute. The dimensions of the cavity were found to be crucial for the calculated dipole moments. These values are compared to those obtained by quantum mechanics calculations, considering Prodan in vacuum, in a polarizable continuum solvent, and using a hybrid quantum mechanics-molecular mechanics methodology. Based on the theoretical approaches it is evident that the Prodan dipole moment can change even in the absence of solute-solvent-specific interactions, which is not taken into consideration with the experimental Lippert-Mataga method. Moreover, in water, for electric dipole moment calculations, it is fundamental to consider hydrogen-bonded molecules.
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Affiliation(s)
- Cíntia C Vequi-Suplicy
- Instituto de Física, Universidade de São Paulo, CP 66318, CEP 05315-970, São Paulo, SP, Brazil
| | - Kaline Coutinho
- Instituto de Física, Universidade de São Paulo, CP 66318, CEP 05315-970, São Paulo, SP, Brazil
| | - M Teresa Lamy
- Instituto de Física, Universidade de São Paulo, CP 66318, CEP 05315-970, São Paulo, SP, Brazil.
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The New Fluorescent Membrane Probe Ahba: A Comparative Study with the Largely Used Laurdan. J Fluoresc 2013; 23:479-86. [DOI: 10.1007/s10895-013-1172-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2012] [Accepted: 01/31/2013] [Indexed: 10/27/2022]
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Vequi-Suplicy CC, Coutinho K, Teresa Lamy M. Optical characterization of Prodan aggregates in water medium. Phys Chem Chem Phys 2013; 15:11800-7. [DOI: 10.1039/c3cp51776d] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Ambrosini A, Bossi G, Dante S, Dubini B, Gobbi L, Leone L, Grazia Ponzi Bossi M, Zolese G. Lipid-drug interaction: thermodynamic and structural effects of antimicotic fluconazole on DPPC liposomes. Chem Phys Lipids 1998. [DOI: 10.1016/s0009-3084(98)00062-0] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Skórko-Glonek J, Lipińska B, Krzewski K, Zolese G, Bertoli E, Tanfani F. HtrA heat shock protease interacts with phospholipid membranes and undergoes conformational changes. J Biol Chem 1997; 272:8974-82. [PMID: 9083020 DOI: 10.1074/jbc.272.14.8974] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
The HtrA (DegP) protein of Escherichia coli is a heat shock serine protease, essential for cell survival only at temperatures above 42 degrees C. It has been shown by genetic experiments that HtrA is an envelope protease, functioning in the periplasmic space. To clarify the cellular localization of HtrA, E. coli cells were fractionated, and HtrA was not detected by the immunoblotting technique in the periplasm or in the fraction of soluble proteins but was found in the inner membrane. The protein could be partially eluted from the total membrane fraction by a high ionic strength solution, whereas solutions affecting protein conformation released HtrA almost completely. These results, taken together with the evidence showing that HtrA functions in the periplasm, indicate that HtrA is a peripheral membrane protein, localized on the periplasmic side of the inner membrane. As the first step toward solving the problem of HtrA-membrane interactions, the structure of HtrA in the presence of phosphatidylglycerol (PG), phosphatidylethanolamine (PE), or cardiolipin (CL) was analyzed by fluorescence and Fourier-transform infrared spectroscopy. The infrared and fluorescence data indicated an interaction of HtrA with PG and CL but not with PE suspensions. Fluorescence spectroscopy revealed that this interaction was at the level of the polar head group of the phospholipid. In the PG/HtrA system, small changes were observed in the HtrA secondary structure and a remarkable decrease of the thermal stability of the protein, which suggested changes in HtrA tertiary structure. This suggestion was supported by fluorescence data that showed a shift of the fluorescence emission spectrum of HtrA tyrosine residues in the presence of PG and a reduced fluorescence intensity, phenomena not observed in the presence of PE or CL suspensions. Infrared data revealed also that the interaction of HtrA with PG leads to a protection of unfolded protein against aggregation at relatively low temperatures. The conformational changes of HtrA in the presence of PG influenced the proteolytic activity of HtrA by increasing it at the temperatures 37-45 degrees C and inhibiting it at 50-55 degrees C. CL inhibited HtrA activity at all of the temperatures tested.
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Affiliation(s)
- J Skórko-Glonek
- Department of Biochemistry, University of Gdańsk, Kadki 24, 80-822 Gdańsk, Poland
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Gabbianelli R, Falcioni G, Mazzanti L, Bertoli E, Zolese G. Seasonal variations of physical and biochemical membrane properties in trout erythrocytes (Salmo irideus). Comp Biochem Physiol B Biochem Mol Biol 1996. [DOI: 10.1016/0305-0491(96)00032-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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Basanez G, Nieva JL, Rivas E, Alonso A, Goni FM. Diacylglycerol and the promotion of lamellar-hexagonal and lamellar-isotropic phase transitions in lipids: implications for membrane fusion. Biophys J 1996; 70:2299-306. [PMID: 9172753 PMCID: PMC1225204 DOI: 10.1016/s0006-3495(96)79795-3] [Citation(s) in RCA: 65] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Changes in steady-state fluorescence anisotropy of 1 -(4-trimethylaminophenyl)-6-phenyl-1,3,5-hexatriene TMA-DPH) are applied to the detection of lamellar-hexagonal transitions in egg phosphatidylethanolamine. Even low (2 mole%) proportions of diacylglycerol decrease the hexagonal transition temperature considerably, as confirmed by differential scanning calorimetry. Diacylglycerol is also found to promote a lamellar to "isotropic" (Q(224) cubic) transition in mixtures of phosphatidylcholine: phosphatidylethanolamine:cholesterol. This nonreversible transition is also observed by (31)P nuclear magnetic resonance and detected as a large increase in TMA-DPH steady-state anisotropy. The same technique reveals as well that lysophosphatidylcholine counteracts the effect of diacylglycerol and stabilizes the lamellar phase in both transitions. Diacylglycerol and lysophosphatidylcholine are known to respectively promote and inhibit membrane fusion in a variety of systems. These data are interpreted in support of the hypothesis of a highly bent structural fusion intermediate ("stalk"). They also show the interest of lipid-phase studies in predicting and rationalizing membrane fusion mechanisms.
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Affiliation(s)
- G Basanez
- Unidad Asociada al C.S.I.C., Departamento de Bioquimica, Universidad del Pais Vasco, Bilbao, Spain
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