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1.
Biochim Biophys Acta ; 1837(3): 345-53, 2014 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-24378845

RESUMO

The constitutive expression of the bacterial carotene desaturase (CRTI) in Arabidopsis thaliana leads to increased susceptibility of leaves to light-induced damage. Changes in the photosynthetic electron transport chain rather than alterations of the carotenoid composition in the antenna were responsible for the increased photoinhibition. A much higher level of superoxide/hydrogen peroxide was generated in the light in thylakoid membranes from the CRTI expressing lines than in wild-type while the level of singlet oxygen generation remained unchanged. The increase in reactive oxygen species was related to the activity of plastid terminal oxidase (PTOX) since their generation was inhibited by the PTOX-inhibitor octyl gallate, and since the protein level of PTOX was increased in the CRTI-expressing lines. Furthermore, cyclic electron flow was suppressed in these lines. We propose that PTOX competes efficiently with cyclic electron flow for plastoquinol in the CRTI-expressing lines and that it plays a crucial role in the control of the reduction state of the plastoquinone pool.


Assuntos
Arabidopsis/genética , Proteínas de Bactérias/genética , Regulação Enzimológica da Expressão Gênica , Oxirredutases/genética , Arabidopsis/metabolismo , Arabidopsis/efeitos da radiação , Proteínas de Arabidopsis/antagonistas & inibidores , Proteínas de Arabidopsis/metabolismo , Proteínas de Bactérias/metabolismo , Carotenoides/metabolismo , Clorofila/metabolismo , Transporte de Elétrons/genética , Transporte de Elétrons/efeitos da radiação , Ácido Gálico/análogos & derivados , Ácido Gálico/farmacologia , Peróxido de Hidrogênio/metabolismo , Immunoblotting , Oxirredução/efeitos da radiação , Oxirredutases/antagonistas & inibidores , Oxirredutases/metabolismo , Fotossíntese/genética , Fotossíntese/efeitos da radiação , Folhas de Planta/genética , Folhas de Planta/metabolismo , Folhas de Planta/efeitos da radiação , Plantas Geneticamente Modificadas , Plastoquinona/análogos & derivados , Plastoquinona/metabolismo , Oxigênio Singlete/metabolismo , Superóxidos/metabolismo , Tilacoides/metabolismo , Tilacoides/efeitos da radiação
2.
J Phys Chem A ; 119(1): 56-66, 2015 Jan 08.
Artigo em Inglês | MEDLINE | ID: mdl-25476500

RESUMO

We report here the resonance Raman spectra and the quantum chemical calculations of the Raman spectra for ß-carotene and 13,13'-diphenyl-ß-carotene. The first aim of this approach was to test the robustness of the method used for modeling ß-carotene, and assess whether it could accurately predict the vibrational properties of derivatives in which conjugated substituents had been introduced. DFT calculations, using the B3LYP functional in combination with the 6-311G(d,p) basis set, were able to accurately predict the influence of two phenyl substituents connected to the ß-carotene molecule, although these deeply perturb the vibrational modes. This experimentally validated modeling technique leads to a fine understanding of the origin of the carotenoid resonance Raman bands, which are widely used for assessing the properties of these molecules, and in particular in complex media, such as binding sites provided by biological macromolecules.


Assuntos
Carotenoides/química , Modelos Moleculares , Estrutura Molecular , Teoria Quântica , Análise Espectral Raman
3.
J Biol Chem ; 288(26): 18758-65, 2013 Jun 28.
Artigo em Inglês | MEDLINE | ID: mdl-23720734

RESUMO

The electronic properties of carotenoid molecules underlie their multiple functions throughout biology, and tuning of these properties by their in vivo locus is of vital importance in a number of cases. This is exemplified by photosynthetic carotenoids, which perform both light-harvesting and photoprotective roles essential to the photosynthetic process. However, despite a large number of scientific studies performed in this field, the mechanism(s) used to modulate the electronic properties of carotenoids remain elusive. We have chosen two specific cases, the two ß-carotene molecules in photosystem II reaction centers and the two luteins in the major photosystem II light-harvesting complex, to investigate how such a tuning of their electronic structure may occur. Indeed, in each case, identical molecular species in the same protein are seen to exhibit different electronic properties (most notably, shifted absorption peaks). We assess which molecular parameters are responsible for this in vivo tuning process and attempt to assign it to specific molecular events imposed by their binding pockets.


Assuntos
Complexos de Proteínas Captadores de Luz/química , Luteína/química , Complexo de Proteína do Fotossistema II/química , beta Caroteno/química , Luz , Fotossíntese , Ligação Proteica , Conformação Proteica , Solventes , Espectrofotometria Ultravioleta , Análise Espectral Raman , Spinacia oleracea/enzimologia , Temperatura
4.
Photosynth Res ; 121(1): 69-77, 2014 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-24861896

RESUMO

Siphonous green algae, a type of deep-sea green algae, appear olive drab and utilize blue-green light for photosynthesis. A siphonous green alga, Codium (C.) intricatum, was isolated from Okinawa prefecture in Japan, and a clonal algal culture in filamentous form was established. The major light-harvesting antenna was analogous to the trimeric LHCII found in higher plants, but the C. intricatum complex contained an unusual carbonyl carotenoid siphonaxanthin. Culture conditions were optimized to achieve high siphonaxanthin content in intact lyophilized filamentous bodies. Interestingly, the carotenoid composition was different when cultured under high irradiance: all-trans neoxanthin was accumulated in addition to the normal 9'-cis form in whole cell extract. Resonance Raman spectra of intact filamentous bodies, cultured under high- and low-light conditions, confirmed the accumulation of all-trans neoxanthin under high irradiance conditions. A plausible function of the presence of all-trans neoxanthin will be discussed in relation to the regulation against high light stress.


Assuntos
Clorófitas/química , Clorófitas/metabolismo , Análise Espectral Raman/métodos , Xantofilas/metabolismo , Xantofilas/química
5.
PLoS One ; 10(8): e0135779, 2015.
Artigo em Inglês | MEDLINE | ID: mdl-26313550

RESUMO

Human retinal macular pigment (MP) is formed by the carotenoids lutein and zeaxanthin (including the isomer meso-zeaxanthin). MP has several functions in improving visual performance and protecting against the damaging effects of light, and MP levels are used as a proxy for macular health-specifically, to predict the likelihood of developing age-related macular degeneration. While the roles of these carotenoids in retinal health have been the object of intense study in recent years, precise mechanistic details of their protective action remain elusive. We have measured the Raman signals originating from MP carotenoids in ex vivo human retinal tissue, in order to assess their structure and conformation. We show that it is possible to distinguish between lutein and zeaxanthin, by their excitation profile (related to their absorption spectra) and the position of their ν1 Raman mode. In addition, analysis of the ν4 Raman band indicates that these carotenoids are present in a specific, constrained conformation in situ, consistent with their binding to specific proteins as postulated in the literature. We discuss how these conclusions relate to the function of these pigments in macular protection. We also address the possibilities for a more accurate, consistent measurement of MP levels by Raman spectroscopy.


Assuntos
Luteína/química , Pigmento Macular/análise , Pigmentos da Retina/química , Zeaxantinas/química , Humanos , Luteína/metabolismo , Conformação Molecular , Pigmentos da Retina/metabolismo , Análise Espectral Raman , Zeaxantinas/metabolismo
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