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Carabadjac I, Vormittag LC, Muszer T, Wuth J, Ulbrich MH, Heerklotz H. Transfer of ANS-Like Drugs from Micellar Drug Delivery Systems to Albumin Is Highly Favorable and Protected from Competition with Surfactant by "Reserved" Binding Sites. Mol Pharm 2024; 21:2198-2211. [PMID: 38625037 DOI: 10.1021/acs.molpharmaceut.3c00875] [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] [Indexed: 04/17/2024]
Abstract
Micellar drug delivery systems (MDDS) for the intravenous administration of poorly soluble drugs have great advantages over alternative formulations in terms of the safety of their excipients, storage stability, and straightforward production. A classic example is mixed micelles of glycocholate (GC) and lecithin, both endogenous substances in human blood. What limits the use of MDDS is the complexity of the transitions after injection. In particular, as the MDDS disintegrate partially or completely after injection, the drug has to be transferred safely to endogenous carriers in the blood, such as human serum albumin (HSA). If this transfer is compromised, the drug might precipitate─a process that needs to be excluded under all circumstances. The key question of this paper is whether the high local concentration of GC at the moment and site of MDDS dissolution might transiently saturate HSA binding sites and, hence, endanger quick drug transfer. To address this question, we have used a new approach, which is time-resolved fluorescence spectroscopy of the single tryptophan in HSA, Trp-214, to characterize the competitive binding of GC and the drug substitute anilinonaphthalenesulfonate (ANS) to HSA. Time-resolved fluorescence of Trp-214 showed important advantages over established methods for tackling this problem. ANS has been the standard "model drug" to study albumin binding for decades, given its structural similarity to the class of naphthalene-containing acidic drugs and the fact that it is displaced from HSA by numerous drugs (which presumably bind to the same sites). Our complex global fit uses the critical approximation that the average lifetimes behave similarly to a single lifetime, but the resulting errors are found to be moderate and the results provide a convincing explanation of the, at first glance, counterintuitive behavior. Accordingly, and largely in line with the literature, we observed two types of sites binding ANS at HSA: 3 type A, rather peripheral, and 2 type B, likely more central sites. The latter quench Trp-214 by Förster Resonance Energy Transfer (FRET) with a rate constant of ≈0.4 ns-1 per ANS. Adding millimolar concentrations of GC displaces ANS from the A sites but not from B sites. At incomplete ANS saturation, this causes a GC-induced translocation of ANS from A to the more FRET-active B sites. This leads to the apparent paradox that the partial displacement of ANS from HSA increases its quenching effect on Trp-214. The most important conclusion is that (ANS-like) drugs cannot be displaced from the type-B sites, and consequently, drug transfer to these sites is not impaired by competitive binding of GC in the vicinity of a dissolving micelle. The second conclusion is that for unbound GC above the CMC (9 mM), ANS equilibrates between HSA and GC micelles but with a strong preference for free sites on HSA. That means that even persisting micelles would lose their cargo readily once exposed to HSA. For all MDDS sharing this property, targeted drug delivery approaches involving them as the nanocarrier would be pointless.
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Affiliation(s)
- Iulia Carabadjac
- Institute of Pharmaceutical Sciences, University of Freiburg, Hermann-Herder-Str. 9, 79104 Freiburg, Germany
| | - Leonie C Vormittag
- Institute of Pharmaceutical Sciences, University of Freiburg, Hermann-Herder-Str. 9, 79104 Freiburg, Germany
| | - Thomas Muszer
- Institute of Pharmaceutical Sciences, University of Freiburg, Hermann-Herder-Str. 9, 79104 Freiburg, Germany
| | - Jakob Wuth
- Institute of Pharmaceutical Sciences, University of Freiburg, Hermann-Herder-Str. 9, 79104 Freiburg, Germany
| | - Maximilian H Ulbrich
- Department of Neuroanatomy, Institute of Anatomy and Cell Biology, Faculty of Medicine, University of Freiburg, Albertstr. 17, 79104 Freiburg, Germany
- BIOSS Centre for Biological Signalling Studies, Schan̈zlestr. 18, Freiburg 79104, Germany
| | - Heiko Heerklotz
- Institute of Pharmaceutical Sciences, University of Freiburg, Hermann-Herder-Str. 9, 79104 Freiburg, Germany
- Leslie Dan Faculty of Pharmacy, University of Toronto, 144 College Street, Toronto M5s 3M2, Ontario, Canada
- BIOSS Centre for Biological Signalling Studies, Schan̈zlestr. 18, Freiburg 79104, Germany
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Tao Y, Fan Y, Wang M, Wang S, Cui JJ, Lian D, Lu S, Li L. Comparative study of the interaction mechanism of astilbin, isoastilbin, and neoastilbin with CYP3A4. LUMINESCENCE 2023; 38:1654-1667. [PMID: 37421260 DOI: 10.1002/bio.4553] [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: 04/11/2023] [Revised: 06/23/2023] [Accepted: 07/03/2023] [Indexed: 07/10/2023]
Abstract
The interactions of human CYP3A4 with three selected isomer flavonoids, such as astilbin, isoastilbin and neoastilbin, were clarified using spectral analysis, molecular docking, and molecular dynamics simulation. During binding with the three flavonoids, the intrinsic fluorescence of CYP3A4 was statically quenched in static mode with nonradiative energy conversion. The fluorescence and ultraviolet/visible (UV/vis) data revealed that the three flavonoids had a moderate and stronger binding affinity with CYP3A4 due to the order of the Ka1 and Ka2 values ranging from 104 to 105 L·mol-1 . In addition, astilbin had the highest affinity with CYP3A4, then isoastilbin and neoastilbin, at the three experimental temperatures. Multispectral analysis confirmed that binding of the three flavonoids resulted in clear changes in the secondary structure of CYP3A4. It was found from fluorescence, UV/vis and molecular docking analyses that these three flavonoids strongly bound to CYP3A4 by means of hydrogen bonds and van der Waals forces. The key amino acids around the binding site were also elucidated. Furthermore, the stabilities of the three CYP3A4 complexes were evaluated using molecular dynamics simulation.
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Affiliation(s)
- Yanzhou Tao
- The College of Chemistry, Changchun Normal University, Changchun, China
| | - Yangyang Fan
- The College of Chemistry, Changchun Normal University, Changchun, China
| | - Meizi Wang
- The College of Chemistry, Changchun Normal University, Changchun, China
| | - Suqing Wang
- The College of Chemistry, Changchun Normal University, Changchun, China
| | - Jing Jing Cui
- The College of Chemistry, Changchun Normal University, Changchun, China
| | - Di Lian
- The College of Chemistry, Changchun Normal University, Changchun, China
| | - Shuning Lu
- The College of Chemistry, Changchun Normal University, Changchun, China
| | - Li Li
- The College of Chemistry, Changchun Normal University, Changchun, China
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Povinelli APR, de Carvalho Bertozo L, Zazeri G, Ximenes VF. A flaw in applying the FRET technique to evaluate the distance between ligands and tryptophan residues in human serum albumin: Proposal of correction. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY. B, BIOLOGY 2023; 242:112693. [PMID: 36947916 DOI: 10.1016/j.jphotobiol.2023.112693] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/10/2023] [Revised: 02/23/2023] [Accepted: 03/08/2023] [Indexed: 03/15/2023]
Abstract
Due to its primordial function as a drug carrier, human serum albumin (HSA) is extensively studied regarding its binding affinity with developing drugs. Förster resonance energy transfer (FRET) is frequently applied as a spectroscopic molecular ruler to measure the distance between the binding site and the ligand. In this work, we have shown that most of the published results that use the FRET technique to estimate the distance from ligands to the binding sites do not corroborate the crystallography data. By comparing the binding affinity of dansyl-proline with HSA and ovotransferrin, we demonstrated that FRET explains the quenching provoked by the interaction of ligands in albumin. So, why does the distance calculation via FRET not corroborate the crystallography data? We have shown that this inconsistency is related to the fact that a one-to-one relationship between donor and acceptor is not present in most experiments. Hence, the quenching efficiency used for calculating energy transfer depends on distance and binding constant, which is inconsistent with the correct application of FRET as a molecular ruler. We have also shown that the indiscriminate attribution of 2/3 to the relative orientation of transition dipoles of the acceptor and donor (κ2) generates inconsistencies. We proposed corrections based on the experimental equilibrium constant and theoretical orientation of transition dipoles to correct the FRET results.
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Affiliation(s)
- Ana Paula Ribeiro Povinelli
- Federal Institute of Education, Science and Technology of Mato Grosso, Campo Novo do Parecis, 78360-000, MT, Brazil
| | - Luiza de Carvalho Bertozo
- Department of Chemistry, Faculty of Sciences, UNESP - São Paulo State University, 17033-360 Bauru, SP, Brazil
| | - Gabriel Zazeri
- Federal Institute of Education, Science and Technology of Mato Grosso, Campo Novo do Parecis, 78360-000, MT, Brazil
| | - Valdecir Farias Ximenes
- Department of Chemistry, Faculty of Sciences, UNESP - São Paulo State University, 17033-360 Bauru, SP, Brazil.
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4
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Heger JE, Chen W, Zhong H, Xiao T, Harder C, Apfelbeck FAC, Weinzierl AF, Boldt R, Schraa L, Euchler E, Sambale AK, Schneider K, Schwartzkopf M, Roth SV, Müller-Buschbaum P. Superlattice deformation in quantum dot films on flexible substrates via uniaxial strain. NANOSCALE HORIZONS 2023; 8:383-395. [PMID: 36723240 DOI: 10.1039/d2nh00548d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
The superlattice in a quantum dot (QD) film on a flexible substrate deformed by uniaxial strain shows a phase transition in unit cell symmetry. With increasing uniaxial strain, the QD superlattice unit cell changes from tetragonal to cubic to tetragonal phase as measured with in situ grazing-incidence small-angle X-ray scattering (GISAXS). The respective changes in the optoelectronic coupling are probed with photoluminescence (PL) measurements. The PL emission intensity follows the phase transition due to the resulting changing inter-dot distances. The changes in PL intensity accompany a redshift in the emission spectrum, which agrees with the Förster resonance energy transfer (FRET) theory. The results are essential for a fundamental understanding of the impact of strain on the performance of flexible devices based on QD films, such as wearable electronics and next-generation solar cells on flexible substrates.
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Affiliation(s)
- Julian E Heger
- Technical University of Munich, TUM School of Natural Sciences, Department of Physics, Chair for Functional Materials, James-Franck-Str. 1, 85748 Garching, Germany.
| | - Wei Chen
- Technical University of Munich, TUM School of Natural Sciences, Department of Physics, Chair for Functional Materials, James-Franck-Str. 1, 85748 Garching, Germany.
- College of Engineering Physics, Shenzhen Technology University (SZTU), Lantian Road 3002, Pingshan, 518118 Shenzhen, China
| | - Huaying Zhong
- Technical University of Munich, TUM School of Natural Sciences, Department of Physics, Chair for Functional Materials, James-Franck-Str. 1, 85748 Garching, Germany.
| | - Tianxiao Xiao
- Technical University of Munich, TUM School of Natural Sciences, Department of Physics, Chair for Functional Materials, James-Franck-Str. 1, 85748 Garching, Germany.
| | - Constantin Harder
- Technical University of Munich, TUM School of Natural Sciences, Department of Physics, Chair for Functional Materials, James-Franck-Str. 1, 85748 Garching, Germany.
- Deutsches Elektronen-Synchrotron DESY, Notkestraße 85, 22607 Hamburg, Germany
| | - Fabian A C Apfelbeck
- Technical University of Munich, TUM School of Natural Sciences, Department of Physics, Chair for Functional Materials, James-Franck-Str. 1, 85748 Garching, Germany.
| | - Alexander F Weinzierl
- Technical University of Munich, TUM School of Natural Sciences, Department of Physics, Chair for Functional Materials, James-Franck-Str. 1, 85748 Garching, Germany.
| | - Regine Boldt
- Leibniz-Institut für Polymerforschung Dresden e.V., Institut für Polymerwerkstoffe, Hohe Straße 6, 01069 Dresden, Germany
| | - Lucas Schraa
- Leibniz-Institut für Polymerforschung Dresden e.V., Institut für Polymerwerkstoffe, Hohe Straße 6, 01069 Dresden, Germany
| | - Eric Euchler
- Leibniz-Institut für Polymerforschung Dresden e.V., Institut für Polymerwerkstoffe, Hohe Straße 6, 01069 Dresden, Germany
| | - Anna K Sambale
- Leibniz-Institut für Polymerforschung Dresden e.V., Institut für Polymerwerkstoffe, Hohe Straße 6, 01069 Dresden, Germany
| | - Konrad Schneider
- Leibniz-Institut für Polymerforschung Dresden e.V., Institut für Polymerwerkstoffe, Hohe Straße 6, 01069 Dresden, Germany
| | | | - Stephan V Roth
- Deutsches Elektronen-Synchrotron DESY, Notkestraße 85, 22607 Hamburg, Germany
- Royal Institute of Technology KTH, Teknikringen 34-35, 100 44 Stockholm, Sweden
| | - P Müller-Buschbaum
- Technical University of Munich, TUM School of Natural Sciences, Department of Physics, Chair for Functional Materials, James-Franck-Str. 1, 85748 Garching, Germany.
- Technical University of Munich, Heinz Maier-Leibnitz Zentrum (MLZ), Lichtenbergstraße 1, 85748 Garching, Germany
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Saurabh A, Fazel M, Safar M, Sgouralis I, Pressé S. Single-photon smFRET. I: Theory and conceptual basis. BIOPHYSICAL REPORTS 2022; 3:100089. [PMID: 36582655 PMCID: PMC9793182 DOI: 10.1016/j.bpr.2022.100089] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/21/2022] [Accepted: 11/28/2022] [Indexed: 12/03/2022]
Abstract
We present a unified conceptual framework and the associated software package for single-molecule Förster resonance energy transfer (smFRET) analysis from single-photon arrivals leveraging Bayesian nonparametrics, BNP-FRET. This unified framework addresses the following key physical complexities of a single-photon smFRET experiment, including: 1) fluorophore photophysics; 2) continuous time kinetics of the labeled system with large timescale separations between photophysical phenomena such as excited photophysical state lifetimes and events such as transition between system states; 3) unavoidable detector artefacts; 4) background emissions; 5) unknown number of system states; and 6) both continuous and pulsed illumination. These physical features necessarily demand a novel framework that extends beyond existing tools. In particular, the theory naturally brings us to a hidden Markov model with a second-order structure and Bayesian nonparametrics on account of items 1, 2, and 5 on the list. In the second and third companion articles, we discuss the direct effects of these key complexities on the inference of parameters for continuous and pulsed illumination, respectively.
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Affiliation(s)
- Ayush Saurabh
- Center for Biological Physics, Arizona State University, Tempe, Arizona,Department of Physics, Arizona State University, Tempe, Arizona
| | - Mohamadreza Fazel
- Center for Biological Physics, Arizona State University, Tempe, Arizona,Department of Physics, Arizona State University, Tempe, Arizona
| | - Matthew Safar
- Center for Biological Physics, Arizona State University, Tempe, Arizona,Department of Mathematics and Statistical Science, Arizona State University, Tempe, Arizona
| | - Ioannis Sgouralis
- Department of Mathematics, University of Tennessee Knoxville, Knoxville, Tennesse
| | - Steve Pressé
- Center for Biological Physics, Arizona State University, Tempe, Arizona,Department of Physics, Arizona State University, Tempe, Arizona,School of Molecular Sciences, Arizona State University, Tempe, Arizona,Corresponding author
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6
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Detection of protein oxidation products by fluorescence spectroscopy and trilinear data decomposition: Proof of concept. Food Chem 2022; 396:133732. [PMID: 35872499 DOI: 10.1016/j.foodchem.2022.133732] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2022] [Revised: 06/21/2022] [Accepted: 07/15/2022] [Indexed: 11/19/2022]
Abstract
Current analytical methods studying protein oxidation modifications require laborious sample preparation and chromatographic methods. Fluorescence spectroscopy is an alternative, as many protein oxidation products are fluorescent. However, the complexity of the signal causes misinterpretation and quantification errors if single emission spectra are used. Here, we analyzed the entire fluorescence excitation-emission matrix using the trilinear decomposition method parallel factor analysis (PARAFAC). Two sample sets were used: a calibration set based on known mixtures of tryptophan, tyrosine, and four oxidation products, and a second sample set of oxidized protein solutions containing UV-illuminated β-lactoglobulin. The PARAFAC model succeeded in resolving the signals of the model systems into the pure fluorophore components and estimating their concentrations. The estimated concentrations for the illuminated β-lactoglobulin samples were validated by liquid chromatography-mass spectrometry. Our approach is a promising tool for reliable identification and quantification of fluorescent protein oxidation products, even in a complex protein system.
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7
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Bhattacharyya N, Singh S, Mukherjee D, Das N, Chatterjee A, Adhikari A, Mondal S, Mondal P, Mallick AK, Pal SK. Picosecond-resolved fluorescence resonance energy transfer (FRET) in diffuse reflectance spectroscopy explores biologically relevant hidden molecular contacts in a non-invasive way. Phys Chem Chem Phys 2022; 24:6176-6184. [PMID: 35229087 DOI: 10.1039/d1cp05159h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The potentiality of Förster resonance energy transfer (FRET) for studying molecular interactions inside biological tissues with improved spatial (Angström) and temporal (picosecond) resolution is well established. On the other hand, the efficacy of diffuse reflectance spectroscopy (DRS) that uses optical radiation in order to determine physiological parameters including haemoglobin, and oxygen saturation is well known. Here we have made an attempt to combine diffuse reflectance spectroscopy (DRS) with picosecond-resolved FRET in order to show improvement in the exploration of molecular contacts in biological tissue models. We define the technique as ultrafast time-resolved diffuse reflectance spectroscopy (UTRDRS). The illuminated photon of the fluorophore from the surface of the tissue-mimicking layers carries the hidden information of the molecular contact. In order to investigate the validation of the Kubelka-Munk (KM) formulism for the developed UTRDRS technique in tissue phantoms, we have studied the propagation of incandescent and picosecond-laser light through several layers of cellulose membranes. While picosecond-resolved FRET in the diffuse reflected light confirms the hidden nano-contact (4.6 nm) of two different dye layers (8-anilino-1-naphthalenesulfonic acid and Nile blue), high-resolution optical microscopy on the cross-section of the layers reveals the proximity and contacts of the layers with limited spatial resolution (∼300 nm). We have also investigated two biologically relevant molecules, namely carboxyfluorescein and haemoglobin, in tissue phantom layers in order to show the efficacy of the UTRDRS technique. Overall, our studies based on UTRDRS in tissue mimicking layers may have potential applications in non-invasive biomedical diagnosis for patients suffering from skin diseases.
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Affiliation(s)
- Neha Bhattacharyya
- Department of Radio Physics and Electronics, University of Calcutta, Kolkata 700009, India.,Technical Research Centre, S.N. Bose National Centre for Basic Sciences, Kolkata 700106, India.
| | - Soumendra Singh
- Technical Research Centre, S.N. Bose National Centre for Basic Sciences, Kolkata 700106, India.
| | - Dipanjan Mukherjee
- Department of Chemical, Biological and Macromolecular Sciences, S.N. Bose National Centre for Basic Sciences, Kolkata 700106, India
| | - Nairit Das
- Department of Electrical Engineering, Indian Institute of Technology, Kharagpur 721302, India
| | - Arka Chatterjee
- Department of Chemical, Biological and Macromolecular Sciences, S.N. Bose National Centre for Basic Sciences, Kolkata 700106, India
| | - Aniruddha Adhikari
- Department of Chemical, Biological and Macromolecular Sciences, S.N. Bose National Centre for Basic Sciences, Kolkata 700106, India
| | - Susmita Mondal
- Department of Chemical, Biological and Macromolecular Sciences, S.N. Bose National Centre for Basic Sciences, Kolkata 700106, India
| | - Pulak Mondal
- Department of Radio Physics and Electronics, University of Calcutta, Kolkata 700009, India
| | - Asim Kumar Mallick
- Department of Paediatrics, Nil Ratan Sircar Medical College and Hospital, Kolkata 700014, India
| | - Samir Kumar Pal
- Technical Research Centre, S.N. Bose National Centre for Basic Sciences, Kolkata 700106, India. .,Department of Chemical, Biological and Macromolecular Sciences, S.N. Bose National Centre for Basic Sciences, Kolkata 700106, India
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8
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Gordon F, Casamayou-Boucau Y, Ryder AG. Evaluating the interaction of human serum albumin (HSA) and 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) liposomes in different aqueous environments using anisotropy resolved multi-dimensional emission spectroscopy (ARMES). Colloids Surf B Biointerfaces 2022; 211:112310. [PMID: 35007857 DOI: 10.1016/j.colsurfb.2021.112310] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2021] [Revised: 12/09/2021] [Accepted: 12/26/2021] [Indexed: 11/28/2022]
Abstract
Studying the interaction between plasma proteins and liposomes is critical, particularly for their use as drug delivery systems. Here, the efficacy of anisotropy resolved multidimensional emission spectroscopy (ARMES) for investigating the interaction of human serum albumin (HSA) with liposomes was explored and compared to conventional spectroscopic techniques. Dynamic Light Scattering (DLS) and absorbance spectroscopy (with Multivariate Curve Resolution (MCR) modeling) indicated that the highest degree of liposome rupturing, and aggregation occurred in water, with less in ammonium bicarbonate buffer (ABC) and phosphate buffered saline (PBS). Fluorescence emission spectra of HSA-liposome mixtures revealed significant hypsochromic shifts for water and ABC, but much less in PBS, where the data suggests a non-penetrating protein layer was formed. Average fluorescence lifetimes decreased upon liposome interaction in water (6.2→5.2 ns) and ABC buffer (6.3→5.6 ns) but increased slightly for PBS (5.6→5.8 ns). ARMES using polarized Total Synchronous Fluorescence Scan measurements with parallel factor (PARAFAC) analysis resolved intrinsic HSA fluorescence into two components for interactions in water and ABC buffer, but only one component for PBS. These components, in water and ABC buffer, corresponded to two different HSA populations, one blue-shifted and penetrating the liposomes (λex/em = ~ 280/320 nm) and a second, similar to free HSA in solution (λex/em = ~ 282/356 nm). PARAFAC scores for water and ABC buffer suggested that a large proportion of HSA interacted in an end on configuration. ARMES provides a new way for investigating protein-liposome interactions that exploits the full intrinsic emission space of the protein and thus avoids the use of extrinsic labels. The use of multivariate data analysis provided a comprehensive and structured framework to extract a variety of useful information (resolving different fluorescent species, quantifying their signal contribution, and extracting light scatter signals) all of which can be used to discriminate between interaction mechanisms.
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Affiliation(s)
- Fiona Gordon
- Nanoscale BioPhotonics Laboratory, School of Chemistry, National University of Ireland, Galway, Galway H91 CF50, Ireland
| | - Yannick Casamayou-Boucau
- Nanoscale BioPhotonics Laboratory, School of Chemistry, National University of Ireland, Galway, Galway H91 CF50, Ireland
| | - Alan G Ryder
- Nanoscale BioPhotonics Laboratory, School of Chemistry, National University of Ireland, Galway, Galway H91 CF50, Ireland.
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9
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Socas LB, Ambroggio EE. Introducing the multi-dimensional spectral phasors: a tool for the analysis of fluorescence excitation-emission matrices. Methods Appl Fluoresc 2022; 10. [PMID: 35139496 DOI: 10.1088/2050-6120/ac5389] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2021] [Accepted: 02/09/2022] [Indexed: 11/12/2022]
Abstract
The use of phasors to analyze fluorescence data was first introduced for time-resolved studies for a simpler mathematical analysis of the fluorescence-decay curves. Recently, this approach was extended to steady-state experiments with the introduction of the spectral phasors (SP), derived from the Fourier transform of the fluorescence emission spectrum. In this work, we revise key mathematical aspects that lead to an interpretation of SP as the characteristic function of a probability distribution. This formalism allows us to introduce a new tool, called multi-dimensional spectral phasor (MdSP) that seize, not only the information from the emission spectrum, but from the full excitation-emission matrix (EEM). In addition, we developed a homemade open-source Java software to facilitate the MdSP data processing. Due to this mathematical conceptualization, we settled a mechanism for the use of MdSP as a tool to tackle spectral signal unmixing problems in a more accurate way than SP. As a proof of principle, with the use of MdSP we approach two important biophysical questions: protein conformational changes and protein-ligand interactions. Specifically, we experimentally measure the EEM changes upon denaturation of human serum albumin (HSA) or during its association with the fluorescence dye 1,8-anilinonaphtalene sulphate (ANS) detected via tryptophan-ANS Förster Resonance Energy Transfer (FRET). In this sense, MdSP allows us to obtain information of the system in a simpler and finer way than the traditional SP. Specifically, understanding a protein's EEM as a molecular fingerprint opens new doors for the use of MdSP as a tool to analyze and comprehend protein conformational changes and interactions.
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Affiliation(s)
- Luis Bp Socas
- Química Biológica, Centro de Investigaciones en Química Biológica de Córdoba, Haya de la Torre y Medina Allende s/n, Cordoba, Córdoba, X5000HUA, ARGENTINA
| | - Ernesto Esteban Ambroggio
- Química Biológica, CIQUIBIC Química Biológica, Haya de la Torre y Medina Allende s/n, Cordoba, X5000HUA, ARGENTINA
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