1
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Clowes SR, Răsădean DM, Gianga TM, Jávorfi T, Hussain R, Siligardi G, Pantoş GD. Mueller Matrix Polarimetry on Cyanine Dye J-Aggregates. Molecules 2023; 28:molecules28041523. [PMID: 36838510 PMCID: PMC9960244 DOI: 10.3390/molecules28041523] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2022] [Revised: 01/28/2023] [Accepted: 02/02/2023] [Indexed: 02/09/2023] Open
Abstract
Cyanine dyes are known to form H- and J-aggregates in aqueous solutions. Here we show that the cyanine dye, S0271, assembles in water into vortex induced chiral J-aggregates. The chirality of the J-aggregates depends on the directionality of the vortex. This study utilised both conventional benchtop CD spectropolarimeters and Mueller matrix polarimetry. It was found that J-aggregates have real chirality alongside linear dichroism and linear and circular birefringence. We identify the factors that are key to the formation of metastable chiral J-aggregates and propose a mechanism for their assembly.
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Affiliation(s)
- Samuel R. Clowes
- Department of Chemistry, University of Bath, Claverton Down, Bath BA2 7AY, UK
| | - Dora M. Răsădean
- Department of Chemistry, University of Bath, Claverton Down, Bath BA2 7AY, UK
| | | | - Tamás Jávorfi
- B23 Beamline, Diamond Light Source, Didcot OX11 0DE, UK
| | | | | | - G. Dan Pantoş
- Department of Chemistry, University of Bath, Claverton Down, Bath BA2 7AY, UK
- Correspondence:
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2
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Górecki M, Lipparini F, Albano G, Jávorfi T, Hussain R, Siligardi G, Pescitelli G, Di Bari L. Cover Feature: Electronic Circular Dichroism Imaging (ECD
i
) Casts a New Light on the Origin of Solid‐State Chiroptical Properties (Chem. Eur. J. 4/2022). Chemistry 2022. [DOI: 10.1002/chem.202104601] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Marcin Górecki
- Institute of Organic Chemistry Polish Academy of Sciences ul. Kasprzaka 44/52 01-224 Warsaw Poland
| | - Filippo Lipparini
- Dipartimento di Chimica e Chimica Industriale Università di Pisa via Moruzzi 13 56124 Pisa Italy
| | - Gianluigi Albano
- Dipartimento di Chimica e Chimica Industriale Università di Pisa via Moruzzi 13 56124 Pisa Italy
- Present address: Dipartimento di Chimica Università degli Studi di Bari “Aldo Moro” via Edoardo Orabona 4 70126 Bari Italy
| | - Tamás Jávorfi
- Diamond Light Source, Ltd. Chilton, Didcot Oxfordshire OX11 0DE UK
| | - Rohanah Hussain
- Diamond Light Source, Ltd. Chilton, Didcot Oxfordshire OX11 0DE UK
| | | | - Gennaro Pescitelli
- Dipartimento di Chimica e Chimica Industriale Università di Pisa via Moruzzi 13 56124 Pisa Italy
| | - Lorenzo Di Bari
- Dipartimento di Chimica e Chimica Industriale Università di Pisa via Moruzzi 13 56124 Pisa Italy
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3
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Górecki M, Lipparini F, Albano G, Jávorfi T, Hussain R, Siligardi G, Pescitelli G, Di Bari L. Electronic Circular Dichroism Imaging (ECDi) Casts a New Light on the Origin of Solid-State Chiroptical Properties. Chemistry 2021; 28:e202103632. [PMID: 34935206 DOI: 10.1002/chem.202103632] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2021] [Indexed: 11/05/2022]
Abstract
Solid-state ECD (ss-ECD) spectra of a model microcrystalline solid, finasteride, dispersed into a KCl pellet were recorded by using the synchrotron radiation source at the Diamond B23 beamline. Scanning a surface of 36 mm2 with a step of 0.5 mm, we measured a set of ECD imaging (ECDi) spectra very different from each other and from the ss-ECD recorded with a bench-top instrument (1 cm2 area). This is due to the anisotropic part of the ECD (ACD), which averages to zero in solution or on a large number of randomly oriented crystallites, but can otherwise be extremely large. Two-way singular value decomposition (SVD) analysis, through experimental and simulated TDDFT spectra, disclosed that the measured and theoretical principal components are in line with each other. This finding demonstrates that the observed isotropic ss-ECD spectrum is governed by the anisotropy of locally oriented crystals. It also introduces a new quality for ss-ECD measurements and opens a new future for probing and mapping chiral materials in the solid state such as active pharmaceutical ingredients (APIs).
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Affiliation(s)
- Marcin Górecki
- Institute of Organic Chemistry, Polish Academy of Sciences, ul. Kasprzaka 44/52, 01-224, Warsaw, Poland
| | - Filippo Lipparini
- Dipartimento di Chimica e Chimica Industriale, Università di Pisa, via Moruzzi 13, 56124, Pisa, Italy
| | - Gianluigi Albano
- Dipartimento di Chimica e Chimica Industriale, Università di Pisa, via Moruzzi 13, 56124, Pisa, Italy.,Present address: Dipartimento di Chimica, Università degli Studi di Bari "Aldo Moro", via Edoardo Orabona 4, 70126, Bari, Italy
| | - Tamás Jávorfi
- Diamond Light Source, Ltd., Chilton, Didcot, Oxfordshire, OX11 0DE, UK
| | - Rohanah Hussain
- Diamond Light Source, Ltd., Chilton, Didcot, Oxfordshire, OX11 0DE, UK
| | | | - Gennaro Pescitelli
- Dipartimento di Chimica e Chimica Industriale, Università di Pisa, via Moruzzi 13, 56124, Pisa, Italy
| | - Lorenzo Di Bari
- Dipartimento di Chimica e Chimica Industriale, Università di Pisa, via Moruzzi 13, 56124, Pisa, Italy
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4
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Hussain R, Jávorfi T, Siligardi G. CD Imaging at High Spatial Resolution at Diamond B23 Beamline: Evolution and Applications. Front Chem 2021; 9:616928. [PMID: 33898387 PMCID: PMC8060634 DOI: 10.3389/fchem.2021.616928] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2020] [Accepted: 02/16/2021] [Indexed: 12/04/2022] Open
Abstract
Circular Dichroism imaging in the 190–650 nm spectral region pionered at Diamond Light Source B23 beamline, has been made possible by the highly collimated microbeam generated at the beamline and has been used to study the homogeneity of the supramolecular structures of thin films of chiral materials deposited on fused quartz substrates. This facility has been expanded with the installation of a Mueller Matrix Polarimeter, MMP, coupled to the beamlight, of which a preliminary data will be discussed. In the solid state, the measurement of CD related to the supramolecular structure is hampered by the presence of circular birefringence, linear dichroism, and linear birefringence that can only be evaluated using the MMP technique. The ability to characterize the chiroptical property of thin chiral films prepared under a variety of conditions and protocols such as drop cast, spin coating, spray at different temperatures and concentrations will enable the determination of the critical parameters for reproducible, uniform and homogeneous specimen preparation, which is the sine qua non for any commercial application. This is of particular importance for optoelectronic materials, but it can also be extended to a broad variety of materials with applications from biosensors to biological tissues.
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Affiliation(s)
- Rohanah Hussain
- Diamond Light Source Ltd., Harwell Science and Innovation Campus, Didcot, United Kingdom
| | - Tamás Jávorfi
- Diamond Light Source Ltd., Harwell Science and Innovation Campus, Didcot, United Kingdom
| | - Giuliano Siligardi
- Diamond Light Source Ltd., Harwell Science and Innovation Campus, Didcot, United Kingdom
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5
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Wade J, Hilfiker JN, Brandt JR, Liirò-Peluso L, Wan L, Shi X, Salerno F, Ryan STJ, Schöche S, Arteaga O, Jávorfi T, Siligardi G, Wang C, Amabilino DB, Beton PH, Campbell AJ, Fuchter MJ. Natural optical activity as the origin of the large chiroptical properties in π-conjugated polymer thin films. Nat Commun 2020; 11:6137. [PMID: 33262352 PMCID: PMC7708482 DOI: 10.1038/s41467-020-19951-y] [Citation(s) in RCA: 43] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2020] [Accepted: 11/06/2020] [Indexed: 11/09/2022] Open
Abstract
Polymer thin films that emit and absorb circularly polarised light have been demonstrated with the promise of achieving important technological advances; from efficient, high-performance displays, to 3D imaging and all-organic spintronic devices. However, the origin of the large chiroptical effects in such films has, until now, remained elusive. We investigate the emergence of such phenomena in achiral polymers blended with a chiral small-molecule additive (1-aza[6]helicene) and intrinsically chiral-sidechain polymers using a combination of spectroscopic methods and structural probes. We show that – under conditions relevant for device fabrication – the large chiroptical effects are caused by magneto-electric coupling (natural optical activity), not structural chirality as previously assumed, and may occur because of local order in a cylinder blue phase-type organisation. This disruptive mechanistic insight into chiral polymer thin films will offer new approaches towards chiroptical materials development after almost three decades of research in this area. Polymer thin films that emit and absorb circularly polarised light are promising in achieving important technological advances, but the origin of the large chiroptical effects in such films has remained elusive. Here the authors demonstrate that in non-aligned polymer thin films, large chiroptical effects are caused by magneto-electric coupling, not structural chirality as previously assumed.
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Affiliation(s)
- Jessica Wade
- Department of Physics, Imperial College London, South Kensington Campus, London, SW7 2AZ, UK.,Centre for Processable Electronics, Imperial College London, South Kensington Campus, London, SW7 2AZ, UK
| | - James N Hilfiker
- J.A. Woollam Co. Inc., 645M Street, Suite 102, Lincoln, NE, 68508-2243, USA
| | - Jochen R Brandt
- Centre for Processable Electronics, Imperial College London, South Kensington Campus, London, SW7 2AZ, UK.,Department of Chemistry and Molecular Sciences Research Hub, Imperial College London, White City Campus, 82 Wood Lane, London, W12 0BZ, UK
| | - Letizia Liirò-Peluso
- School of Chemistry & The GSK Carbon Neutral Laboratories for Sustainable Chemistry, University of Nottingham, Triumph Road, Nottingham, NG7 2TU, UK.,School of Physics and Astronomy, University of Nottingham, University Park, Nottingham, NG7 2RD, UK
| | - Li Wan
- Department of Physics, Imperial College London, South Kensington Campus, London, SW7 2AZ, UK.,Centre for Processable Electronics, Imperial College London, South Kensington Campus, London, SW7 2AZ, UK
| | - Xingyuan Shi
- Centre for Processable Electronics, Imperial College London, South Kensington Campus, London, SW7 2AZ, UK.,Department of Chemistry and Molecular Sciences Research Hub, Imperial College London, White City Campus, 82 Wood Lane, London, W12 0BZ, UK
| | - Francesco Salerno
- Centre for Processable Electronics, Imperial College London, South Kensington Campus, London, SW7 2AZ, UK.,Department of Chemistry and Molecular Sciences Research Hub, Imperial College London, White City Campus, 82 Wood Lane, London, W12 0BZ, UK
| | - Seán T J Ryan
- Department of Chemistry and Molecular Sciences Research Hub, Imperial College London, White City Campus, 82 Wood Lane, London, W12 0BZ, UK
| | - Stefan Schöche
- J.A. Woollam Co. Inc., 645M Street, Suite 102, Lincoln, NE, 68508-2243, USA
| | - Oriol Arteaga
- Departament de Física Aplicada, Universitat de Barcelona, IN2UB, Barcelona, 08028, Spain
| | - Tamás Jávorfi
- Diamond Light Source, Harwell Science and Innovation Campus, Didcot, Oxfordshire, OX11 0DE, UK
| | - Giuliano Siligardi
- Diamond Light Source, Harwell Science and Innovation Campus, Didcot, Oxfordshire, OX11 0DE, UK
| | - Cheng Wang
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California, 94720, USA
| | - David B Amabilino
- School of Chemistry & The GSK Carbon Neutral Laboratories for Sustainable Chemistry, University of Nottingham, Triumph Road, Nottingham, NG7 2TU, UK
| | - Peter H Beton
- School of Physics and Astronomy, University of Nottingham, University Park, Nottingham, NG7 2RD, UK
| | - Alasdair J Campbell
- Department of Physics, Imperial College London, South Kensington Campus, London, SW7 2AZ, UK. .,Centre for Processable Electronics, Imperial College London, South Kensington Campus, London, SW7 2AZ, UK.
| | - Matthew J Fuchter
- Centre for Processable Electronics, Imperial College London, South Kensington Campus, London, SW7 2AZ, UK. .,Department of Chemistry and Molecular Sciences Research Hub, Imperial College London, White City Campus, 82 Wood Lane, London, W12 0BZ, UK.
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6
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Akhtar P, Lindorfer D, Lingvay M, Pawlak K, Zsiros O, Siligardi G, Jávorfi T, Dorogi M, Ughy B, Garab G, Renger T, Lambrev PH. Anisotropic Circular Dichroism of Light-Harvesting Complex II in Oriented Lipid Bilayers: Theory Meets Experiment. J Phys Chem B 2019; 123:1090-1098. [PMID: 30604975 DOI: 10.1021/acs.jpcb.8b12474] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Anisotropic circular dichroism (ACD) spectroscopy of macroscopically aligned molecules reveals additional information about their excited states that is lost in the CD of randomly oriented solutions. ACD spectra of light-harvesting complex II (LHCII)-the main peripheral antenna of photosystem II in plants-in oriented lipid bilayers were recorded from the far-UV to the visible wavelength region. ACD spectra show a drastically enhanced magnitude and level of detail compared to the isotropic CD spectra, resolving a greater number of bands and weak optical transitions. Exciton calculations show that the spectral features in the chlorophyll Q y region are well-reproduced by an existing Hamiltonian for LHCII, providing further evidence for the identity of energy sinks at chlorophylls a603 and a610 in the stromal layer and chlorophylls a604 and a613 in the luminal layer. We propose ACD spectroscopy to be a valuable tool linking the three-dimensional structure and the photophysical properties of pigment-protein complexes.
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Affiliation(s)
- Parveen Akhtar
- Biological Research Centre , Hungarian Academy of Sciences , Temesvári krt. 62 , 6726 Szeged , Hungary.,ELI-ALPS, ELI-HU Nonprofit Ltd. , Budapesti út 5 , 6728 Szeged , Hungary
| | - Dominik Lindorfer
- Institute for Theoretical Physics , Johannes Kepler University Linz , Altenberger Str. 69 , 4040 Linz , Austria
| | - Mónika Lingvay
- Biological Research Centre , Hungarian Academy of Sciences , Temesvári krt. 62 , 6726 Szeged , Hungary.,Faculty of Science and Informatics, Doctoral School of Physics , University of Szeged , Dóm tér 9 , 6720 Szeged , Hungary
| | - Krzysztof Pawlak
- Biological Research Centre , Hungarian Academy of Sciences , Temesvári krt. 62 , 6726 Szeged , Hungary
| | - Ottó Zsiros
- Biological Research Centre , Hungarian Academy of Sciences , Temesvári krt. 62 , 6726 Szeged , Hungary
| | - Giuliano Siligardi
- Diamond Light Source Ltd. , Harwell Science and Innovation Campus , Didcot , Oxfordshire OX11 0DE , U.K
| | - Tamás Jávorfi
- Diamond Light Source Ltd. , Harwell Science and Innovation Campus , Didcot , Oxfordshire OX11 0DE , U.K
| | - Márta Dorogi
- Biological Research Centre , Hungarian Academy of Sciences , Temesvári krt. 62 , 6726 Szeged , Hungary
| | - Bettina Ughy
- Biological Research Centre , Hungarian Academy of Sciences , Temesvári krt. 62 , 6726 Szeged , Hungary
| | - Győző Garab
- Biological Research Centre , Hungarian Academy of Sciences , Temesvári krt. 62 , 6726 Szeged , Hungary.,Faculty of Science, Department of Physics , University of Ostrava , Chittussiho 10 , 710 00 Ostrava , Czech Republic
| | - Thomas Renger
- Institute for Theoretical Physics , Johannes Kepler University Linz , Altenberger Str. 69 , 4040 Linz , Austria
| | - Petar H Lambrev
- Biological Research Centre , Hungarian Academy of Sciences , Temesvári krt. 62 , 6726 Szeged , Hungary
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7
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Albano G, Górecki M, Pescitelli G, Di Bari L, Jávorfi T, Hussain R, Siligardi G. Electronic circular dichroism imaging (CDi) maps local aggregation modes in thin films of chiral oligothiophenes. NEW J CHEM 2019. [DOI: 10.1039/c9nj02746g] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A detailed investigation of the circular dichroism imaging (CDi) technique on thin films of a chiral 1,4-dialkoxyphenylene-based oligothiophene with outstanding chiroptical features revealed the primary role of local supramolecular structures.
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Affiliation(s)
- Gianluigi Albano
- Dipartimento di Chimica e Chimica Industriale
- Università di Pisa
- 56124 Pisa
- Italy
| | - Marcin Górecki
- Dipartimento di Chimica e Chimica Industriale
- Università di Pisa
- 56124 Pisa
- Italy
- Institute of Organic Chemistry
| | - Gennaro Pescitelli
- Dipartimento di Chimica e Chimica Industriale
- Università di Pisa
- 56124 Pisa
- Italy
| | - Lorenzo Di Bari
- Dipartimento di Chimica e Chimica Industriale
- Università di Pisa
- 56124 Pisa
- Italy
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8
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Bortolini C, Kartanas T, Copic D, Condado Morales I, Zhang Y, Challa PK, Peter Q, Jávorfi T, Hussain R, Dong M, Siligardi G, Knowles TPJ, Charmet J. Resolving protein mixtures using microfluidic diffusional sizing combined with synchrotron radiation circular dichroism. Lab Chip 2018; 19:50-58. [PMID: 30515508 DOI: 10.1039/c8lc00757h] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Circular dichroism spectroscopy has become a powerful tool to characterise proteins and other biomolecules. For heterogeneous samples such as those present for interacting proteins, typically only average spectroscopic features can be resolved. Here we overcome this limitation by using free-flow microfluidic size separation in-line with synchrotron radiation circular dichroism to resolve the secondary structure of each component of a model protein mixture containing monomers and fibrils. To enable this objective, we have integrated far-UV compatible measurement chambers into PDMS-based microfluidic devices. Two architectures are proposed so as to accommodate for a wide range of concentrations. The approach, which can be used in combination with other bulk measurement techniques, paves the way to the study of complex mixtures such as the ones associated with protein misfolding and aggregation diseases including Alzheimer's and Parkinson's diseases.
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Affiliation(s)
- Christian Bortolini
- Chemistry Department, University of Cambridge, Lensfield Road, Cambridge, CB3 0FF, UK
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9
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Sitsanidis ED, Piras CC, Alexander BD, Siligardi G, Jávorfi T, Hall AJ, Edwards AA. Circular dichroism studies of low molecular weight hydrogelators: The use of SRCD and addressing practical issues. Chirality 2018; 30:708-718. [PMID: 29645307 DOI: 10.1002/chir.22850] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2017] [Revised: 02/08/2018] [Accepted: 02/14/2018] [Indexed: 11/08/2022]
Abstract
Circular dichroism (CD) spectroscopy has been used extensively for the investigation of the conformation and configuration of chiral molecules, but its use for evaluating the mode of self-assembly in soft materials has been limited. Herein, we report a protocol for the study of such materials by electronic CD spectroscopy using commercial/benchtop instruments and synchrotron radiation (SR) using the B23 beamline available at Diamond Light Source. The use of the B23 beamtime for SRCD was advantageous because of the unique enhanced spatial resolution achieved because of its highly collimated and small beamlight cross section (ca. 250 μm) and higher photon flux in the far UV region (175-250 nm) enhancing the signal-to-noise ratio relative to benchtop CD instruments. A set of low molecular weight (LMW) hydrogelators, comprising two Fmoc-protected enantiomeric monosaccharides and one Fmoc dipeptide (Fmoc-FF), were studied. The research focused on the optimization of sample preparation and handling, which then enabled the characterization of sample conformational homogeneity and thermal stability. CD spectroscopy, in combination with other spectroscopic techniques and microscopy, will allow a better insight into the self-assembly of chiral building blocks into higher order structural architectures.
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Affiliation(s)
| | - Carmen C Piras
- Medway School of Pharmacy, Universities of Greenwich and Kent at Medway, Kent, UK
| | - Bruce D Alexander
- Department of Pharmaceutical, Chemical and Environmental Sciences, University of Greenwich, Kent, UK
| | | | | | - Andrew J Hall
- Medway School of Pharmacy, Universities of Greenwich and Kent at Medway, Kent, UK
| | - Alison A Edwards
- Medway School of Pharmacy, Universities of Greenwich and Kent at Medway, Kent, UK
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10
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Hussain R, Hughes CS, Jávorfi T, Siligardi G, Williams P, Bonev BB. To Boil an Egg: Substrate Binding Affects Critical Stability in Thermal Unfolding of Proteins. J Phys Chem B 2018; 122:2213-2218. [PMID: 29401389 DOI: 10.1021/acs.jpcb.7b10643] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Thermal unfolding of proteins is used extensively in screening of drug candidates because molecular interactions with ligands and substrates affect strongly protein stability, transition temperature, and cooperativity. We use synchrotron radiation circular dichroism to monitor the thermal evolution of secondary structure in proteins as they approach the melting point and the impact of substrate on their thermal behavior. Using Landau free energy expansion, we quantify transition strength and proximity to a critical point through the relative separation τ+ between the transition temperature Tm and the spinodal T+, obtained from the equation of state. The weakest transition was observed in lysozyme with τ+ = -0.0167 followed by holo albumin with τ+ = -0.0208 with the strongest transition in monomeric apo albumin τ+ = -0.0242. A structural transition at 45 °C in apo albumin leads to a noncooperative melt with τ+ = -0.00532 and amyloidogenic increase in beta content.
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Affiliation(s)
- Rohanah Hussain
- Diamond Light Source Ltd. , Harwell Science and Innovation Campus, Chilton, Didcot, Oxfordshire OX11 0DE, U.K
| | - Charlotte S Hughes
- Diamond Light Source Ltd. , Harwell Science and Innovation Campus, Chilton, Didcot, Oxfordshire OX11 0DE, U.K
| | - Tamás Jávorfi
- Diamond Light Source Ltd. , Harwell Science and Innovation Campus, Chilton, Didcot, Oxfordshire OX11 0DE, U.K
| | - Giuliano Siligardi
- Diamond Light Source Ltd. , Harwell Science and Innovation Campus, Chilton, Didcot, Oxfordshire OX11 0DE, U.K
| | - Paul Williams
- School of Life Sciences, University of Nottingham , Queen's Medical Centre, Nottingham NG7 2UH, U.K
| | - Boyan B Bonev
- School of Life Sciences, University of Nottingham , Queen's Medical Centre, Nottingham NG7 2UH, U.K
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11
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Zinna F, Resta C, Górecki M, Pescitelli G, Di Bari L, Jávorfi T, Hussain R, Siligardi G. Circular Dichroism Imaging: Mapping the Local Supramolecular Order in Thin Films of Chiral Functional Polymers. Macromolecules 2017. [DOI: 10.1021/acs.macromol.6b02590] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Affiliation(s)
- Francesco Zinna
- Dipartimento
di Chimica e Chimica Industriale, University of Pisa, Via Moruzzi
13, 56124 Pisa, Italy
| | - Claudio Resta
- Dipartimento
di Chimica e Chimica Industriale, University of Pisa, Via Moruzzi
13, 56124 Pisa, Italy
| | - Marcin Górecki
- Dipartimento
di Chimica e Chimica Industriale, University of Pisa, Via Moruzzi
13, 56124 Pisa, Italy
| | - Gennaro Pescitelli
- Dipartimento
di Chimica e Chimica Industriale, University of Pisa, Via Moruzzi
13, 56124 Pisa, Italy
| | - Lorenzo Di Bari
- Dipartimento
di Chimica e Chimica Industriale, University of Pisa, Via Moruzzi
13, 56124 Pisa, Italy
| | - Tamás Jávorfi
- Diamond Light
Source, Ltd., Chilton, Didcot OX11 0DE, United Kingdom
| | - Rohanah Hussain
- Diamond Light
Source, Ltd., Chilton, Didcot OX11 0DE, United Kingdom
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12
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Hussain R, Jávorfi T, Rudd TR, Siligardi G. High-throughput SRCD using multi-well plates and its applications. Sci Rep 2016; 6:38028. [PMID: 28004702 PMCID: PMC5177961 DOI: 10.1038/srep38028] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2016] [Accepted: 11/03/2016] [Indexed: 12/03/2022] Open
Abstract
The sample compartment for high-throughput synchrotron radiation circular dichroism (HT-SRCD) has been developed to satisfy an increased demand of protein characterisation in terms of folding and binding interaction properties not only in the traditional field of structural biology but also in the growing research area of material science with the potential to save time by 80%. As the understanding of protein behaviour in different solvent environments has increased dramatically the development of novel functions such as recombinant proteins modified to have different functions from harvesting solar energy to metabolonics for cleaning heavy and metal and organic molecule pollutions, there is a need to characterise speedily these system.
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Affiliation(s)
- Rohanah Hussain
- Diamond Light Source, Diamond House, Chilton, Didcot OX11 0DE, United Kingdom
| | - Tamás Jávorfi
- Diamond Light Source, Diamond House, Chilton, Didcot OX11 0DE, United Kingdom
| | - Timothy R Rudd
- Diamond Light Source, Diamond House, Chilton, Didcot OX11 0DE, United Kingdom
| | - Giuliano Siligardi
- Diamond Light Source, Diamond House, Chilton, Didcot OX11 0DE, United Kingdom
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13
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Pazderková M, Profant V, Seidlerová B, Dlouhá H, Hodačová J, Jávorfi T, Siligardi G, Baumruk V, Bednárová L, Maloň P. Electronic circular dichroism of the chiral rigid tricyclic dilactam with nonplanar tertiary amide groups. J Phys Chem B 2014; 118:11100-8. [PMID: 25180568 DOI: 10.1021/jp5063463] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Electronic circular dichroism (ECD) of the spirocyclic dilactam 5,8-diazatricyclo[6,3,0,0(1,5)]undecane-4,9-dione has been measured in the extended wavelength range (170-260 nm) utilizing far-UV CD instrumentation including synchrotron radiation light source. The data of this model of two nonplanar tertiary amide groups interacting within the rigid chiral environment provided new information particularly about the shorter wavelength π-π* transition region below 190 nm. The interpretation using TDDFT calculations confirmed that effects of amide nonplanarity follow our previous observations on monolactams as far as amide n-π* transitions are concerned. ECD band in the n-π* transition region of the nonplanar diamide exhibits an identical bathochromic shift and its sign remains tied to the sense of nonplanar deformation in the same way. As far as n-π* transitions are concerned amide nonplanarity acts as a local phenomenon independently reflecting sum properties of single amide groups. On the other hand, CD bands associated with π-π* transitions (found between ∼170 to 210 nm) form an exciton-like couplet with the sign pattern determined by mutual orientation of the associated electric transition moments. This sign pattern follows predictions pertaining to a coupled oscillator. The influence of amide nonplanarity on π-π* transitions is only minor and concentrates into the shorter wavelength lobe of the π-π* couplet. The detailed analysis of experimental ECD with the aid of TDDFT calculations shows that there is only little interaction between effects of inherent chirality caused by nonplanarity of amide groups and amide-amide coupling. Consequently these two effects can be studied nearly independently using ECD. In addition, the calculations indicate that participation of other type of transitions (n-σ*, π-σ* or Rydberg type transitions) is only minor and is concentrated below 180 nm.
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Affiliation(s)
- Markéta Pazderková
- Faculty of Mathematics and Physics, Charles University in Prague , Ke Karlovu 5, 121 16 Prague 2, Czech Republic
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Miloslavina Y, Lambrev PH, Jávorfi T, Várkonyi Z, Karlický V, Wall JS, Hind G, Garab G. Anisotropic circular dichroism signatures of oriented thylakoid membranes and lamellar aggregates of LHCII. Photosynth Res 2012; 111:29-39. [PMID: 21667227 DOI: 10.1007/s11120-011-9664-y] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/04/2011] [Accepted: 05/27/2011] [Indexed: 05/24/2023]
Abstract
In photosynthesis research, circular dichroism (CD) spectroscopy is an indispensable tool to probe molecular architecture at virtually all levels of structural complexity. At the molecular level, the chirality of the molecule results in intrinsic CD; pigment-pigment interactions in protein complexes and small aggregates can give rise to excitonic CD bands, while "psi-type" CD signals originate from large, densely packed chiral aggregates. It has been well established that anisotropic CD (ACD), measured on samples with defined non-random orientation relative to the propagation of the measuring beam, carries specific information on the architecture of molecules or molecular macroassemblies. However, ACD is usually combined with linear dichroism and can be distorted by instrumental imperfections, which given the strong anisotropic nature of photosynthetic membranes and complexes, might be the reason why ACD is rarely studied in photosynthesis research. In this study, we present ACD spectra, corrected for linear dichroism, of isolated intact thylakoid membranes of granal chloroplasts, washed unstacked thylakoid membranes, photosystem II (PSII) membranes (BBY particles), grana patches, and tightly stacked lamellar macroaggregates of the main light-harvesting complex of PSII (LHCII). We show that the ACD spectra of face- and edge-aligned stacked thylakoid membranes and LHCII lamellae exhibit profound differences in their psi-type CD bands. Marked differences are also seen in the excitonic CD of BBY and washed thylakoid membranes. Magnetic CD (MCD) spectra on random and aligned samples, and the largely invariable nature of the MCD spectra, despite dramatic variations in the measured isotropic and anisotropic CD, testify that ACD can be measured without substantial distortions and thus employed to extract detailed information on the (supra)molecular organization of photosynthetic complexes. An example is provided showing the ability of CD data to indicate such an organization, leading to the discovery of a novel crystalline structure in macroaggregates of LHCII.
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Affiliation(s)
- Yuliya Miloslavina
- Institute of Plant Biology, Biological Research Center, Hungarian Academy of Sciences, P.O. Box 521, 6701, Szeged, Hungary
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Hussain R, Jávorfi T, Siligardi G. Circular dichroism beamline B23 at the Diamond Light Source. J Synchrotron Radiat 2012; 19:132-135. [PMID: 22186655 DOI: 10.1107/s0909049511038982] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/05/2011] [Accepted: 09/22/2011] [Indexed: 05/31/2023]
Abstract
Synchrotron radiation circular dichroism (SRCD) is a well established technique in structural biology. The first UV-VIS beamline, dedicated to circular dichroism, at Diamond Light Source Ltd, a third-generation synchrotron facility in south Oxfordshire, UK, has recently become operational and it is now available for the user community. Herein the main characteristics of the B23 SRCD beamline, the ancillary facilities available for users, and some of the recent advances achieved are summarized.
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Chappaz-Gillot C, Marek PL, Blaive BJ, Canard G, Bürck J, Garab G, Hahn H, Jávorfi T, Kelemen L, Krupke R, Mössinger D, Ormos P, Reddy CM, Roussel C, Steinbach G, Szabó M, Ulrich AS, Vanthuyne N, Vijayaraghavan A, Zupcanova A, Balaban TS. Anisotropic organization and microscopic manipulation of self-assembling synthetic porphyrin microrods that mimic chlorosomes: bacterial light-harvesting systems. J Am Chem Soc 2011; 134:944-54. [PMID: 22148684 DOI: 10.1021/ja203838p] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Being able to control in time and space the positioning, orientation, movement, and sense of rotation of nano- to microscale objects is currently an active research area in nanoscience, having diverse nanotechnological applications. In this paper, we demonstrate unprecedented control and maneuvering of rod-shaped or tubular nanostructures with high aspect ratios which are formed by self-assembling synthetic porphyrins. The self-assembly algorithm, encoded by appended chemical-recognition groups on the periphery of these porphyrins, is the same as the one operating for chlorosomal bacteriochlorophylls (BChl's). Chlorosomes, rod-shaped organelles with relatively long-range molecular order, are the most efficient naturally occurring light-harvesting systems. They are used by green photosynthetic bacteria to trap visible and infrared light of minute intensities even at great depths, e.g., 100 m below water surface or in volcanic vents in the absence of solar radiation. In contrast to most other natural light-harvesting systems, the chlorosomal antennae are devoid of a protein scaffold to orient the BChl's; thus, they are an attractive goal for mimicry by synthetic chemists, who are able to engineer more robust chromophores to self-assemble. Functional devices with environmentally friendly chromophores-which should be able to act as photosensitizers within hybrid solar cells, leading to high photon-to-current conversion efficiencies even under low illumination conditions-have yet to be fabricated. The orderly manner in which the BChl's and their synthetic counterparts self-assemble imparts strong diamagnetic and optical anisotropies and flow/shear characteristics to their nanostructured assemblies, allowing them to be manipulated by electrical, magnetic, or tribomechanical forces.
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Affiliation(s)
- Cyril Chappaz-Gillot
- ISM2-Chirosciences, Faculté des Sciences, Aix-Marseille Univ. UMR 6263, Saint-Jérôme, Case A62, Avenue Escadrille Normandie-Niemen, F-13397 Marseille, Cedex 20, France
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Jávorfi T, Hussain R, Myatt D, Siligardi G. Measuring circular dichroism in a capillary cell using the b23 synchrotron radiation CD beamline at diamond light source. Chirality 2011; 22 Suppl 1:E149-53. [PMID: 21038386 DOI: 10.1002/chir.20924] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Synchrotron radiation circular dichroism (SRCD) is a well-established method in structural biology. The first UV-VIS beamline dedicated to circular dichroism at Diamond Light Source, a third generation synchrotron facility in South Oxfordshire, has recently become operational and it is now available for the user community. Herein we present an important application of SRCD: the CD measurement of protein solutions in fused silica rectangular capillary cells. This was achieved without the use of any lens between the photoelastic modulator and the photomultiplier tube detectors by exploiting the high photon flux of the collimated beam that can be as little as half a millimeter squared. Measures to minimize or eliminate vacuum-UV protein denaturation effects are discussed. The CD spectra measured in capillaries is a proof of principle to address CD measurements in microdevice systems using the new B23 SRCD beamline.
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Affiliation(s)
- Tamás Jávorfi
- Diamond Light Source Ltd., Harwell Science & Innovation Campus, Diamond House, OX11 0DE Didcot, United Kingdom
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De Santis E, Hjelmgaard T, Faure S, Roy O, Didierjean C, Alexander BD, Siligardi G, Hussain R, Jávorfi T, Edwards AA, Taillefumier C. Cyclic α,β-peptoid octamers with differing side chain patterns: synthesis and conformational investigation. Amino Acids 2011; 41:663-72. [DOI: 10.1007/s00726-011-0887-1] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2011] [Accepted: 03/08/2011] [Indexed: 11/28/2022]
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Naqvi KR, Melø TB, Jávorfi T, González-Pérez S, Arellano JB. Facile method for spectroscopic examination of radical ions of hydrophilic carotenoids. Phys Chem Chem Phys 2009; 11:6401-5. [DOI: 10.1039/b905454e] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Yang C, Lambrev P, Chen Z, Jávorfi T, Kiss AZ, Paulsen H, Garab G. The negatively charged amino acids in the lumenal loop influence the pigment binding and conformation of the major light-harvesting chlorophyll a/b complex of photosystem II. Biochim Biophys Acta 2008; 1777:1463-70. [PMID: 18809373 DOI: 10.1016/j.bbabio.2008.08.009] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/03/2008] [Revised: 08/21/2008] [Accepted: 08/25/2008] [Indexed: 10/21/2022]
Abstract
The major chlorophyll (Chl) a/b complexes of photosystem II (LHCIIb), in addition to their primary light-harvesting function, play key roles in the organization of the granal ultrastructure of the thylakoid membranes and in various regulatory processes. These functions depend on the structural stability and flexibility of the complexes. The lumenal side of LHCIIb is exposed to broadly variable pH environments, due to the build-up and decay of the pH gradient during photosynthesis. Therefore, the negatively charged amino acids in the lumenal loop might be of paramount importance for adjusting the structure and functions of LHCIIb. In order to clarify the structural roles of these residues, we investigated the pigment stoichiometries, absorption, linear and circular dichroism spectra of the reconstituted LHCIIb complexes, in which the negatively charged amino acids in the lumenal loop were exchanged to neutral ones (E94G, E107V and D111V). The mutations influenced the pigment binding and the molecular architecture of the complexes. Exchanging E94 to G destabilized the 3(10) helix in the lumenal loop structure and led to an acquired pH sensitivity of the LHCIIb structure. We conclude that these amino acids are important not only for pigment binding in the complexes, but also in stabilizing the conformation of LHCIIb at different pHs.
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Affiliation(s)
- Chunhong Yang
- Key Laboratory of Photosynthesis and Environmental Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, PR China.
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Stoitchkova K, Zsiros O, Jávorfi T, Páli T, Andreeva A, Gombos Z, Garab G. Heat- and light-induced reorganizations in the phycobilisome antenna of Synechocystis sp. PCC 6803. Thermo-optic effect. Biochim Biophys Acta 2007; 1767:750-6. [PMID: 17442263 DOI: 10.1016/j.bbabio.2007.03.002] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2006] [Revised: 02/15/2007] [Accepted: 03/02/2007] [Indexed: 11/17/2022]
Abstract
By using absorption and fluorescence spectroscopy, we compared the effects of heat and light treatments on the phycobilisome (PBS) antenna of Synechocystis sp. PCC 6803 cells. Fluorescence emission spectra obtained upon exciting predominantly PBS, recorded at 25 degrees C and 77 K, revealed characteristic changes upon heat treatment of the cells. A 5-min incubation at 50 degrees C, which completely inactivated the activity of photosystem II, led to a small but statistically significant decrease in the F(680)/F(655) fluorescence intensity ratio. In contrast, heat treatment at 60 degrees C resulted in a much larger decrease in the same ratio and was accompanied by a blue-shift of the main PBS emission band at around 655 nm (F(655)), indicating an energetic decoupling of PBS from chlorophylls and reorganizations in its internal structure. (Upon exciting PBS, F(680) originates from photosystem II and from the terminal emitter of PBS.). Very similar changes were obtained upon exposing the cells to high light (600-7500 micromol photons m(-2) s(-1)) for different time periods (10 min to 3 h). In cells with heat-inactivated photosystem II, the variations caused by light treatment could clearly be assigned to a similar energetic decoupling of the PBS from the membrane and internal reorganizations as induced at around 60 degrees C. These data can be explained within the frameworks of thermo-optic mechanism [Cseh et al. 2000, Biochemistry 39, 15250]: in high light the heat packages originating from dissipation might lead to elementary structural changes in the close vicinity of dissipation in heat-sensitive structural elements, e.g. around the site where PBS is anchored to the membrane. This, in turn, brings about a diminishment in the energy supply from PBS to the photosystems and reorganization in the molecular architecture of PBS.
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Affiliation(s)
- Katerina Stoitchkova
- Institute of Plant Biology, Biological Research Center, Hungarian Academy of Sciences, P.O. Box 521, H-6701 Szeged, Hungary
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Erostyák J, Jávorfi T, Buzády A, Naqvi KR, Garab G. Comparative study of integrating cavity absorption meters. ACTA ACUST UNITED AC 2006; 69:189-96. [PMID: 16644020 DOI: 10.1016/j.jbbm.2006.03.010] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2005] [Revised: 03/03/2006] [Accepted: 03/14/2006] [Indexed: 10/24/2022]
Abstract
Integrating spheres (IS) are widely used for recording spectra of scattering samples by placing the specimen inside or outside the sphere. An unusual application of integrating spheres has been also demonstrated earlier where the liquid sample completely filled the spherical cavity; such a device is often called an integrating cavity absorption meter (ICAM). In the present work, integrating cavities with different coatings are compared. The spheres were made of glass, covered by metal or white paint, and their surfaces were prepared for diffuse or specular reflectance. The spheres were evaluated by recording kinetic traces following a short light pulse with the aid of time-correlated single photon counting (TCSPC), and by recording steady-state spectra through single-photon counting (SPC) detection. The relative efficiencies of the spheres were determined by comparing the steady-state spectra. Possible reasons for differences in the performance are discussed.
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Affiliation(s)
- János Erostyák
- Department of Experimental Physics, University of Pécs, Ifjúság u. 6., H-7624 Pécs, Hungary.
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Mohamad SBB, Yousef YA, Melø TB, Jávorfi T, Partali V, Sliwka HR, Razi Naqvi K. Singlet oxygen quenching by thione analogues of canthaxanthin, echinenone and rhodoxanthin. J Photochem Photobiol B 2006; 84:135-40. [PMID: 16563794 DOI: 10.1016/j.jphotobiol.2006.02.006] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/03/2005] [Revised: 01/22/2006] [Accepted: 02/02/2006] [Indexed: 11/28/2022]
Abstract
Thione analogues of three naturally occurring carotenones (canthaxanthin, echinenone, and rhodoxanthin) were synthesized just over ten years ago, and it was reported that substitution of the oxygen atom by sulphur brings about a large red shift and some broadening in the optical absorption spectrum of the compound. Since the three carotenothiones are scarce, determination of their molar absorption coefficients presents a challenge. A method for relating the molar absorption coefficient of a carotenothione (Car-S) to that of its ketone analogue (Car-O) has been developed, which has revealed that the peak molar absorption coefficient of a Car-S is only about 60% of the corresponding value for Car-O. Using methylene blue as the sensitizer and acetonitrile as the solvent, we have also investigated the quenching (under photostationary conditions) of the 1270nm phosphorescence emission of singlet oxygen by each of the six carotenoids. The data conform to the Stern-Volmer relation, and show that substitution of a carbonyl oxygen atom by sulphur does not lead to an appreciable change in the value of the quenching constant, which is close to 1.5 x 10(10)M(-1)s(-1) for all six quenchers.
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Affiliation(s)
- Samsun B B Mohamad
- Department of Physics, Norwegian University of Science and Technology (NTNU), N-7491 Trondheim, Norway
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Jávorfi T, Erostyák J, Gál J, Buzády A, Menczel L, Garab G, Razi Naqvi K. Quantitative spectrophotometry using integrating cavities. J Photochem Photobiol B 2005; 82:127-31. [PMID: 16307890 DOI: 10.1016/j.jphotobiol.2005.10.002] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/20/2005] [Revised: 10/10/2005] [Accepted: 10/11/2005] [Indexed: 10/25/2022]
Abstract
Absorption spectrophotometry, a standard tool for quantitative analysis, suffers from two major drawbacks: lack of sensitivity and vulnerability to scattering. It has been pointed out earlier that the solution to these problems lies in using a reflecting cavity as a sample holder. Due to multiple reflections at the cavity wall, the effective pathlength becomes considerably larger than the diameter of the cavity, and scattering losses are eliminated because scattered light is prevented from escaping the detector. Though much effort has been spent in analysing and improving the performance of such a device, often called an integrating cavity absorption meter (ICAM), a simple strategy for deducing the absorbance of the sample is still lacking. It is shown here that the absorbance A' measured by using an ICAM exhibits a sublinear increase with the solute concentration C. The physical reason for this departure from linearity is explained, and a straightforward procedure for converting A' to the true absorbance A (proportional to C) is established. The reliability of the procedure is demonstrated by comparing the ICAM absorption spectrum of dilute dye solutions with the spectra of more concentrated solutions recorded in a conventional spectrophotometer. The ability of the device to cope with scattering was tested by filling the ICAM with a suspension of chloroplasts, and the spectrum was found, as expected, to be free from scattering artefacts.
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Affiliation(s)
- Tamás Jávorfi
- Institute of Plant Biology, Biological Research Center, P.O. Box 521, H-6701 Szeged, Hungary.
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Jávorfi T, Garab G, Naqvi KR. Reinvestigation of the triplet-minus-singlet spectrum of chloroplasts. Spectrochim Acta A Mol Biomol Spectrosc 2000; 56A:211-214. [PMID: 10728872 DOI: 10.1016/s1386-1425(99)00226-7] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
A comparison of the triplet-minus-singlet (TmS) absorption spectrum of spinach chloroplasts, recorded some thirty years ago, with the more recently published TmS spectrum of isolated Chla/b LHCII (light-harvesting complexes associated with photosystem II of higher plants) shows that the two spectra are very similar, which is to be expected, since only the carotenoid pigments contribute to each spectrum. Be that as it may, the comparison also reveals a dissimilarity: photoexcitation of the sample does, or does not, affect the absorbance in the Qy region (650-700 nm), depending on whether the sample is a suspension of chloroplasts or of isolated LHCII. The Qy-signal in the TmS spectrum of LHCII decays, it should be noted, at the same rate as the rest of the difference spectrum, and its most prominent feature is a negative peak. As the carotenoids do not absorb in the Qy region, the presence of a signal in this region calls for an explanation: van der Vos, Carbonera and Hoff, the first to find as well as fathom the phenomenon, attributed the Qy-signal to a change, in the absorption spectrum of a chlorophyll a (Chla) molecule, brought about by the presence of triplet excitation on a neighbouring carotenoid (Car). The difference in the behaviours of chloroplasts and LHCII, if reproducible, would imply that the Car triplets which give rise to the TmS spectrum of chloroplasts do not influence the absorption spectra of their Chla neighbours. With a view to reaching a firm conclusion about this vexed issue, spinach chloroplasts and thylakoids have been examined with the aid of the same kinetic spectrometer as that used for investigating LHCII; the TmS spectra of both chloroplasts and thylakoids contain prominent bleaching signals centred at 680 nm, and the triplet decay time in each case is comparable to that of the Chla/b LHCII triplets. Results pertaining to other closely related systems are recalled, and it is concluded that, so far as the overall appearance of the TmS spectrum is concerned, spinach chloroplasts are by no means abnormal.
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Osuka A, Kume T, Haggquist G, Jávorfi T, Lima JC, Melo E, Razi Naqvi K. Photophysical characteristics of two model antenna systems: a fucoxanthin–pyropheoporbide dyad and its peridinin analogue. Chem Phys Lett 1999. [DOI: 10.1016/s0009-2614(99)01098-2] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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