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1.
Photosynth Res ; 159(2-3): 133-152, 2024 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-37191762

RESUMO

Photo-induced triplet states in the thylakoid membranes isolated from the cyanobacterium Acaryocholoris marina, that harbours Chlorophyll (Chl) d as its main chromophore, have been investigated by Optically Detected Magnetic Resonance (ODMR) and time-resolved Electron Paramagnetic Resonance (TR-EPR). Thylakoids were subjected to treatments aimed at poising the redox state of the terminal electron transfer acceptors and donors of Photosystem II (PSII) and Photosystem I (PSI), respectively. Under ambient redox conditions, four Chl d triplet populations were detectable, identifiable by their characteristic zero field splitting parameters, after deconvolution of the Fluorescence Detected Magnetic Resonance (FDMR) spectra. Illumination in the presence of the redox mediator N,N,N',N'-Tetramethyl-p-phenylenediamine (TMPD) and sodium ascorbate at room temperature led to a redistribution of the triplet populations, with T3 (|D|= 0.0245 cm-1, |E|= 0.0042 cm-1) becoming dominant and increasing in intensity with respect to untreated samples. A second triplet population (T4, |D|= 0.0248 cm-1, |E|= 0.0040 cm-1) having an intensity ratio of about 1:4 with respect to T3 was also detectable after illumination in the presence of TMPD and ascorbate. The microwave-induced Triplet-minus-Singlet spectrum acquired at the maximum of the |D|-|E| transition (610 MHz) displays a broad minimum at 740 nm, accompanied by a set of complex spectral features that overall resemble, despite showing further fine spectral structure, the previously reported Triplet-minus-Singlet spectrum attributed to the recombination triplet of PSI reaction centre, 3 P 740 [Schenderlein M, Çetin M, Barber J, et al. Spectroscopic studies of the chlorophyll d containing photosystem I from the cyanobacterium Acaryochloris marina. Biochim Biophys Acta 1777:1400-1408]. However, TR-EPR experiments indicate that this triplet displays an eaeaea electron spin polarisation pattern which is characteristic of triplet sublevels populated by intersystem crossing rather than recombination, for which an aeeaae polarisation pattern is expected instead. It is proposed that the observed triplet, which leads to the bleaching of the P740 singlet state, sits on the PSI reaction centre.


Assuntos
Cianobactérias , Complexo de Proteína do Fotossistema I , Tilacoides , Tilacoides/química , Complexo de Proteína do Fotossistema I/química , Clorofila/química , Complexo de Proteína do Fotossistema II/química , Espectroscopia de Ressonância de Spin Eletrônica
2.
J Environ Manage ; 364: 121459, 2024 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-38870798

RESUMO

The current trend in the European biogas industry is to shift away from electricity production towards the production of biomethane for the need to replace natural gas. The upgrading of biogas to biomethane is normally performed by separating the biogas in a stream containing natural gas grid quality methane and a stream containing mostly CO2. The CO2 stream is normally released into the atmosphere; however, part of the methane may still remain in it, and, if not oxidized, even a small fraction of methane released may jeopardise all the GHG emissions savings from producing the biomethane, being methane a powerful climate forcer. Scope of this work is to assess the opportunity cost of installing an Off Gas Combustion (OGC) device in biomethane upgrading plants. The currently available technologies for biogas upgrading to biomethane and the most common technology of OGC (the Regenerative Thermal Oxidisers, RTO) are described according to their performances and cost. Then the cost per tonne of CO2eq avoided associated to the adoption of RTO systems in relation to the upgrading performance is calculated to identify a potential threshold for an effective and efficient application of the RTO systems. It is found that, in case of upgrading technologies which can capture almost all biomethane in the upgrading off-gas (i.e. 99.9%), currently the adoption of an RTO to oxidise the methane left in the off-gas would add costs and need additional fuel to be operated, but would generate limited GHG emission savings, therefore the cost per tonne of CO2eq emissions avoided would result not competitive with other GHG emissions mitigation investments. While the installation of RTOs on upgrading systems with a methane slip of 0.3%, or higher, normally results cost competitive in reducing GHG emissions. The installation of an RTO on systems with a methane slip of 0.2% results in a cost per tonne of CO2eq emissions avoided of 50-100 euro, which is comparable to the current cost of CO2 emissions allowances in the EU ETS carbon market, representing therefore a reasonable choice for a threshold on methane slip regulation for biogas upgrading systems.


Assuntos
Biocombustíveis , Dióxido de Carbono , Gases de Efeito Estufa , Metano , Gases de Efeito Estufa/análise , Dióxido de Carbono/análise , Efeito Estufa , Gás Natural
3.
Phys Chem Chem Phys ; 25(42): 28998-29016, 2023 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-37859550

RESUMO

The influence of carotenoid triplet states on the Qy electronic transitions of chlorophylls has been observed in experiments on light-harvesting complexes over the past three decades, but the interpretation of the resulting spectral feature in the triplet minus singlet (T-S) absorption spectra of photosystems is still debated, as the physical-chemical explanation of this feature has been elusive. Here, we resolve this debate, by explaining the T-S spectra of pigment complexes over the Qy-band spectral region through a comparative study of chlorophyll-carotenoid model dyads and larger pigment complexes from the main light harvesting complex of higher plants (LHCII). This goal is achieved by combining state-of-the-art time-dependent density functional theory with analysis of the relationship between electronic properties and nuclear structure, and by comparison to the experiment. We find that the special signature in the T-S spectra of both model and natural photosystems is determined by singlet-like triplet excitations that can be described as effective singlet excitations on chlorophylls influenced by a stable electronic triplet on the carotenoid. The comparison with earlier experiments on different light-harvesting complexes confirms our theoretical interpretation of the T-S spectra in the Qy spectral region. Our results indicate an important role for the chlorophyll-carotenoid electronic coupling, which is also responsible for the fast triplet-triplet energy transfer, suggesting a fast trapping of the triplet into the relaxed carotenoid structure. The gained understanding of the interplay between the electronic and nuclear structures is potentially informative for future studies of the mechanism of photoprotection by carotenoids.

4.
BMC Med ; 20(1): 500, 2022 12 27.
Artigo em Inglês | MEDLINE | ID: mdl-36575453

RESUMO

BACKGROUND: Obesity and related co-morbidities represent a major health challenge nowadays, with a rapidly increasing incidence worldwide. The gut microbiome has recently emerged as a key modifier of human health that can affect the development and progression of obesity, largely due to its involvement in the regulation of food intake and metabolism. However, there are still few studies that have in-depth explored the functionality of the human gut microbiome in obesity and even fewer that have examined its relationship to eating behaviors. METHODS: In an attempt to advance our knowledge of the gut-microbiome-brain axis in the obese phenotype, we thoroughly characterized the gut microbiome signatures of obesity in a well-phenotyped Italian female cohort from the NeuroFAST and MyNewGut EU FP7 projects. Fecal samples were collected from 63 overweight/obese and 37 normal-weight women and analyzed via a multi-omics approach combining 16S rRNA amplicon sequencing, metagenomics, metatranscriptomics, and lipidomics. Associations with anthropometric, clinical, biochemical, and nutritional data were then sought, with particular attention to cognitive and behavioral domains of eating. RESULTS: We identified four compositional clusters of the gut microbiome in our cohort that, although not distinctly associated with weight status, correlated differently with eating habits and behaviors. These clusters also differed in functional features, i.e., transcriptional activity and fecal metabolites. In particular, obese women with uncontrolled eating behavior were mostly characterized by low-diversity microbial steady states, with few and poorly interconnected species (e.g., Ruminococcus torques and Bifidobacterium spp.), which exhibited low transcriptional activity, especially of genes involved in secondary bile acid biosynthesis and neuroendocrine signaling (i.e., production of neurotransmitters, indoles and ligands for cannabinoid receptors). Consistently, high amounts of primary bile acids as well as sterols were found in their feces. CONCLUSIONS: By finding peculiar gut microbiome profiles associated with eating patterns, we laid the foundation for elucidating gut-brain axis communication in the obese phenotype. Subject to confirmation of the hypotheses herein generated, our work could help guide the design of microbiome-based precision interventions, aimed at rewiring microbial networks to support a healthy diet-microbiome-gut-brain axis, thus counteracting obesity and related complications.


Assuntos
Microbioma Gastrointestinal , Humanos , Feminino , Microbioma Gastrointestinal/genética , RNA Ribossômico 16S/genética , Multiômica , Obesidade/genética , Dieta , Comportamento Alimentar/fisiologia , Fezes/microbiologia
5.
Photosynth Res ; 152(2): 213-234, 2022 May.
Artigo em Inglês | MEDLINE | ID: mdl-35290567

RESUMO

The photoexcited triplet state of the "primary donors" in the two photosystems of oxygenic photosynthesis has been investigated by means of electron-nuclear double resonance (ENDOR) at Q-band (34 GHz). The data obtained represent the first set of 1H hyperfine coupling tensors of the 3P700 triplet state in PSI and expand the existing data set for 3P680. We achieved an extensive assignment of the observed electron-nuclear hyperfine coupling constants (hfcs) corresponding to the methine α-protons and the methyl group ß-protons of the chlorophyll (Chl) macrocycle. The data clearly confirm that in both photosystems the primary donor triplet is located on one specific monomeric Chl at cryogenic temperature. In comparison to previous transient ENDOR and pulse ENDOR experiments at standard X-band (9-10 GHz), the pulse Q-band ENDOR spectra demonstrate both improved signal-to-noise ratio and increased resolution. The observed ENDOR spectra for 3P700 and 3P680 differ in terms of the intensity loss of lines from specific methyl group protons, which is explained by hindered methyl group rotation produced by binding site effects. Contact analysis of the methyl groups in the PSI crystal structure in combination with the ENDOR analysis of 3P700 suggests that the triplet is located on the Chl a' (PA) in PSI. The results also provide additional evidence for the localization of 3P680 on the accessory ChlD1 in PSII.


Assuntos
Complexo de Proteína do Fotossistema I , Prótons , Clorofila A , Espectroscopia de Ressonância de Spin Eletrônica , Fotossíntese
6.
Int J Mol Sci ; 23(9)2022 Apr 27.
Artigo em Inglês | MEDLINE | ID: mdl-35563202

RESUMO

Carotenoids represent the first line of defence of photosystems against singlet oxygen (1O2) toxicity, because of their capacity to quench the chlorophyll triplet state (3Chl) through a physical mechanism based on the transfer of triplet excitation (triplet-triplet energy transfer, TTET). In previous works, we showed that the antenna LHCII is characterised by a robust photoprotective mechanism, able to adapt to the removal of individual chlorophylls while maintaining a remarkable capacity for 3Chl quenching. In this work, we investigated the effects on this quenching induced in LHCII by the replacement of the lutein bound at the L1 site with violaxanthin and zeaxanthin. We studied LHCII isolated from the Arabidopsis thaliana mutants lut2-in which lutein is replaced by violaxanthin-and lut2 npq2, in which all xanthophylls are replaced constitutively by zeaxanthin. We characterised the photophysics of these systems via optically detected magnetic resonance (ODMR) and time-resolved electron paramagnetic resonance (TR-EPR). We concluded that, in LHCII, lutein-binding sites have conserved characteristics, and ensure efficient TTET regardless of the identity of the carotenoid accommodated.


Assuntos
Arabidopsis , Luteína , Arabidopsis/metabolismo , Carotenoides/metabolismo , Clorofila/metabolismo , Transferência de Energia , Complexos de Proteínas Captadores de Luz/metabolismo , Complexo de Proteína do Fotossistema II/metabolismo , Xantofilas/química , Zeaxantinas/metabolismo
7.
Molecules ; 27(12)2022 Jun 07.
Artigo em Inglês | MEDLINE | ID: mdl-35744779

RESUMO

A magnetophotoselection (MPS) investigation of the photoexcited triplet state of chlorophyll a both in a frozen organic solvent and in a protein environment, provided by the water-soluble chlorophyll protein (WSCP) of Lepidium virginicum, is reported. The MPS experiment combines the photoselection achieved by exciting with linearly polarized light with the magnetic selection of electron paramagnetic resonance (EPR) spectroscopy, allowing the determination of the relative orientation of the optical transition dipole moment and the zero-field splitting tensor axes in both environments. We demonstrate the robustness of the proposed methodology for a quantitative description of the excitonic interactions among pigments. The orientation of the optical transition dipole moments determined by the EPR analysis in WSCP, identified as an appropriate model system, are in excellent agreement with those calculated in the point-dipole approximation. In addition, MPS provides information on the electronic properties of the triplet state, localized on a single chlorophyll a pigment of the protein cluster, in terms of orientation of the zero-field splitting tensor axes in the molecular frame.


Assuntos
Clorofila , Lepidium , Clorofila/química , Clorofila A/metabolismo , Espectroscopia de Ressonância de Spin Eletrônica , Lepidium/metabolismo , Complexos de Proteínas Captadores de Luz/química , Água/química
8.
Photochem Photobiol Sci ; 20(6): 747-759, 2021 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-34018156

RESUMO

The type-I, homodimeric photosynthetic reaction center (RC) of Heliobacteria (HbRC) is the only known RC in which bacteriochlorophyll g (BChl g) is found. It is also simpler than other RCs, having the smallest number of protein subunits and bound chromophores of any type-I RC. In the presence of oxygen, BChl g isomerizes to 81-hydroxychlorophyll aF (Chl aF). This naturally occurring process provides a way of altering the chlorophylls and studying the effect of these changes on energy and electron transfer. Transient absorbance difference spectroscopy reveals that triplet-state formation occurs in the antenna chlorophylls of HbRCs but does not provide site-specific information. Here, we report on an extended optically detected magnetic resonance (ODMR) study of the antenna triplet states in HbRCs with differing levels of conversion of BChl g to Chl aF. The data reveal pools of BChl g molecules with different triplet zero-field splitting parameters and different susceptibilities to chemical oxidation. By relating the detailed spectroscopic characteristics derived from the ODMR data to the recently solved crystallographic structure, we have tentatively identified BChl g molecules in which the probability of triplet formation is high and sites at which BChl g conversion is more likely, providing useful information about the fate of the excitation in the complex.


Assuntos
Bacterioclorofilas/química , Clostridiales/química , Oxigênio/análise , Bacterioclorofilas/metabolismo , Clostridiales/metabolismo , Espectroscopia de Ressonância Magnética , Oxigênio/metabolismo
9.
Adv Health Sci Educ Theory Pract ; 25(4): 799-808, 2020 10.
Artigo em Inglês | MEDLINE | ID: mdl-31960188

RESUMO

Medical students' motivations for choosing a medical career are likely based on and remain tethered to the affectively-laden caring component of doctor-patient interactions. However, this component is rarely presented in educational surgical videos. It is unknown whether affectively engaging students by including patient-related emotionally salient information potentiates or draws focus away from learning a surgical procedure and whether such information affects motivation and attitudes toward the video. Therefore, we investigate whether presenting a patient's emotional state before video surgery enhances or weakens the educational value of that video. In a within-subjects crossover design, second-year medical students (n = 130) viewed video clips of surgeries. These videos, from online medical education platforms, were preceded by the patient's information from the original video or by information about the patient's preoperative emotional preparation. After each video, participants completed a multiple-choice test about the video's content to measure learning, answered a question about their motivation to re-watch the video, and completed an attitude scale regarding the video. Incorporating patient's information into surgical videos significantly enhanced students' acquisition of the technical aspects of surgery procedures (p < 0.0001), motivation to re-watch the video (p < 0.001), and favorable attitudes toward the video (p = 0.02). These findings show that incorporating information about patients' emotional states may enhance students' positive attitudes and motivations toward educational videos and may improve their learning of surgical techniques. They also suggest that the role of this factor should be considered when developing guidelines for medical educational video release.


Assuntos
Educação Médica/métodos , Emoções , Pacientes/psicologia , Procedimentos Cirúrgicos Operatórios/educação , Gravação em Vídeo , Atitude do Pessoal de Saúde , Competência Clínica , Estudos Cross-Over , Feminino , Humanos , Aprendizagem , Masculino , Motivação , Adulto Jovem
10.
Biochim Biophys Acta Bioenerg ; 1859(8): 612-618, 2018 08.
Artigo em Inglês | MEDLINE | ID: mdl-29782823

RESUMO

The peridinin-chlorophyll-a protein (PCP) is a water-soluble light harvesting protein of the dinoflagellate Amphidinium carterae, employing peridinin (Per) as the main carotenoid to fulfil light harvesting and photo-protective functions. Per molecules bound to the protein experience specific molecular surroundings which lead to different electronic and spectral properties. In the refolded N89 L variant PCP (N89 L-RFPCP) a significant part of the intensity on the long wavelength side of the absorption spectrum is shifted to shorter wavelengths due to a significant change in the Per-614 site energy. Since Per-614 has been shown to be the main chlorophyll (Chl) triplet quencher in the protein, and the relative geometry of pigments is not affected by the mutation as verified by X-ray crystallography, this variant is ideally suited to study the dependence of the triplet-triplet energy transfer (TTET) mechanism on the pigment site energy. By using a combination of Optically Detected Magnetic Resonance (ODMR), pulse Electron Paramagnetic Resonance (EPR) and Electron Nuclear DOuble Resonance (ENDOR) we found that PCP maintains the efficient Per-614-to-Chl-a TTET despite the change of Per-614 local energy. This shows the robustness of the photoprotective site, which is very important for the protection of the system.


Assuntos
Carotenoides/química , Clorofila/química , Transferência de Energia , Fotossíntese , Proteínas de Protozoários/química , Spiroplasma/química , Dinoflagellida/metabolismo , Espectroscopia de Ressonância de Spin Eletrônica , Modelos Moleculares , Conformação Proteica
11.
Eur Eat Disord Rev ; 26(6): 657-670, 2018 11.
Artigo em Inglês | MEDLINE | ID: mdl-30350446

RESUMO

Similarities in neural activation patterns in obese and substance-dependent subjects led to the food addiction concept, but studies exploiting this issue for obesity stratification are missing. We assessed brain activation in response to food cues using 18 F-2-fluoro-2-deoxy-glucose-PET in 36 overweight women, stratified by low or high food addiction groups according to the Yale Food Addiction Scale (YFAS). Assessments were repeated after a 3-month diet. We found greater activation in thalamus, hypothalamus, midbrain, putamen, and occipital cortex (reward), but not in prefrontal and orbitofrontal cortices (control/reward receipt) in the high-YFAS versus low-YFAS group. In high-YFAS subjects, orbitofrontal responsiveness was inversely related to YFAS severity and hunger rating, and positive associations were observed between regional brain activation and lipid intake. A 3-month diet abolished group differences in brain activation. Our data suggest that food addiction distinguishes an overweight phenotype that can be reversed by diet, opening to personalized strategies in obesity treatment.


Assuntos
Encéfalo/fisiologia , Restrição Calórica , Dependência de Alimentos/fisiopatologia , Sobrepeso/dietoterapia , Sobrepeso/fisiopatologia , Adulto , Sinais (Psicologia) , Feminino , Alimentos , Dependência de Alimentos/diagnóstico , Humanos , Fenótipo , Escalas de Graduação Psiquiátrica , Resultado do Tratamento
12.
Biochemistry ; 56(12): 1726-1736, 2017 03 28.
Artigo em Inglês | MEDLINE | ID: mdl-28252285

RESUMO

Water-soluble chlorophyll proteins (WSCPs) of class IIa from Brassicaceae form tetrameric complexes containing one chlorophyll (Chl) per apoprotein but no carotenoids. The complexes are remarkably stable toward dissociation and protein denaturation even at 100 °C and extreme pH values, and the Chls are partially protected against photooxidation. There are several hypotheses that explain the biological role of WSCPs, one of them proposing that they function as a scavenger of Chls set free upon plant senescence or pathogen attack. The biochemical properties of WSCP described in this paper are consistent with the protein acting as an efficient and flexible Chl scavenger. At limiting Chl concentrations, the recombinant WSCP apoprotein binds substoichiometric amounts of Chl (two Chls per tetramer) to form complexes that are as stable toward thermal dissociation, denaturation, and photodamage as the fully pigmented ones. If more Chl is added, these two-Chl complexes can bind another two Chls to reach the fully pigmented state. The protection of WSCP Chls against photodamage has been attributed to the apoprotein serving as a diffusion barrier for oxygen, preventing its access to triplet excited Chls and, thus, the formation of singlet oxygen. By contrast, the sequential binding of Chls by WSCP suggests a partially open or at least flexible structure, raising the question of how WSCP photoprotects its Chls without the help of carotenoids.


Assuntos
Apoproteínas/química , Brassica/metabolismo , Clorofila/química , Complexos de Proteínas Captadores de Luz/química , Proteínas de Plantas/química , Apoproteínas/genética , Apoproteínas/metabolismo , Brassica/química , Brassica/genética , Clorofila/metabolismo , Clorofila A , Expressão Gênica , Temperatura Alta , Concentração de Íons de Hidrogênio , Luz , Complexos de Proteínas Captadores de Luz/genética , Complexos de Proteínas Captadores de Luz/metabolismo , Modelos Moleculares , Oxirredução , Oxigênio , Pisum sativum/química , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Ligação Proteica , Desnaturação Proteica , Domínios Proteicos , Multimerização Proteica , Estabilidade Proteica , Estrutura Secundária de Proteína , Proteínas Recombinantes de Fusão/química , Proteínas Recombinantes de Fusão/genética , Proteínas Recombinantes de Fusão/metabolismo , Oxigênio Singlete , Solubilidade , Tilacoides/química , Tilacoides/metabolismo , Água/química
13.
Biochemistry ; 55(26): 3636-49, 2016 07 05.
Artigo em Inglês | MEDLINE | ID: mdl-27290879

RESUMO

Carotenes and their oxygenated derivatives, xanthophylls, are structural elements of the photosynthetic apparatus and contribute to increasing both the light-harvesting and photoprotective capacity of the photosystems. ß-Carotene is present in both the core complexes and light-harvesting system (LHCI) of Photosystem (PS) I, while xanthophylls lutein and violaxanthin bind exclusively to its antenna moiety; another xanthophyll, zeaxanthin, which protects chloroplasts against photooxidative damage, binds to the LHCI complexes under conditions of excess light. We functionally dissected various components of the xanthophyll- and carotene-dependent photoprotection mechanism of PSI by analyzing two Arabidopsis mutants: szl1 plants, with a carotene content lower than that of the wild type, and npq1, with suppressed zeaxanthin formation. When exposed to excess light, the szl1 genotype displayed PSI photoinhibition stronger than that of wild-type plants, while removing zeaxanthin had no such effect. The PSI-LHCI complex purified from szl1 was more photosensitive than the corresponding wild-type and npq1 complexes, as is evident from its faster photobleaching and increased rate of singlet oxygen release, suggesting that ß-carotene is crucial in controlling chlorophyll triplet formation. Accordingly, fluorescence-detected magnetic resonance analysis showed an increase in the amplitude of signals assigned to chlorophyll triplets in ß-carotene-depleted complexes. When PSI was fractioned into its functional moieties, it was revealed that the boost in the rate of singlet oxygen release caused by ß-carotene depletion was greater in LHCI than in the core complex. We conclude that PSI-LHCI complex-bound ß-carotene elicits a protective response, consisting of a reduction in the yield of harmful triplet excited states, while accumulation of zeaxanthin plays a minor role in restoring phototolerance.


Assuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/metabolismo , Carotenoides/metabolismo , Complexos de Proteínas Captadores de Luz/metabolismo , Complexo de Proteína do Fotossistema I/metabolismo , Xantofilas/metabolismo , Arabidopsis/genética , Arabidopsis/efeitos da radiação , Proteínas de Arabidopsis/genética , Clorofila/metabolismo , Clorofila/efeitos da radiação , Cloroplastos/metabolismo , Cloroplastos/efeitos da radiação , Fluorescência , Luz , Complexos de Proteínas Captadores de Luz/genética , Mutação , Fotossíntese/efeitos da radiação , Complexo de Proteína do Fotossistema I/genética , Oxigênio Singlete
14.
Biochim Biophys Acta ; 1847(2): 262-275, 2015 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-25481107

RESUMO

The photo-excited triplet states of carotenoids, sensitised by triplet-triplet energy transfer from the chlorophyll triplet states, have been investigated in the isolated Photosystem II (PSII) core complex and PSII-LHCII (Light Harvesting Complex II) supercomplex by Optically Detected Magnetic Resonance techniques, using both fluorescence (FDMR) and absorption (ADMR) detection. The absence of Photosystem I allows us to reach the full assignment of the carotenoid triplet states populated in PSII under steady state illumination at low temperature. Five carotenoid triplet ((3)Car) populations were identified in PSII-LHCII, and four in the PSII core complex. Thus, four (3)Car populations are attributed to ß-carotene molecules bound to the core complex. All of them show associated fluorescence emission maxima which are relatively red-shifted with respect to the bulk emission of both the PSII-LHCII and the isolated core complexes. In particular the two populations characterised by Zero Field Splitting parameters |D|=0.0370-0.0373 cm(-1)/|E|=0.00373-0.00375 cm(-1) and |D|=0.0381-0.0385 cm(-1)/|E|=0.00393-0.00389 cm(-1), are coupled by singlet energy transfer with chlorophylls which have a red-shifted emission peaking at 705 nm. This observation supports previous suggestions that pointed towards the presence of long-wavelength chlorophyll spectral forms in the PSII core complex. The fifth (3)Car component is observed only in the PSII-LHCII supercomplex and is then assigned to the peripheral light harvesting system.


Assuntos
Carotenoides/química , Complexos de Proteínas Captadores de Luz/química , Complexo de Proteína do Fotossistema II/química , Transferência de Energia , Espectroscopia de Ressonância Magnética , Espectrometria de Fluorescência
15.
Biochim Biophys Acta ; 1837(8): 1235-46, 2014 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-24704151

RESUMO

Violaxanthin-chlorophyll a binding protein (VCP) is the major light harvesting complex (LHC) of the Heterokonta Nannochloropsis gaditana. It binds chlorophyll a, violaxanthin and vaucheriaxanthin, the last in the form of 19' deca/octanoate esters. Photosynthetic apparatus of algae belonging to this group have been poorly characterized in the past, but they are now receiving an increasing interest also because of their possible biotechnological application in biofuel production. In this work, isolated VCP proteins have been studied by means of advanced EPR techniques in order to prove the presence of the photoprotective mechanism based on the triplet-triplet energy transfer (TTET), occurring between chlorophyll and carotenoid molecules. This process has been observed before in several light harvesting complexes belonging to various photosynthetic organisms. We used Optically Detected Magnetic Resonance (ODMR) to identify the triplet states populated by photo-excitation, and describe the optical properties of the chromophores carrying the triplet states. In parallel, time-resolved EPR (TR-EPR) and pulse EPR have been employed to get insight into the TTET mechanism and reveal the structural features of the pigment sites involved in photoprotection. The analysis of the spectroscopic data shows a strong similarity among VCP, FCP from diatoms and LHC-II from higher plants. Although these antenna proteins have differentiated sequences and bind different pigments, results suggest that in all members of the LHC superfamily there is a protein core with a conserved structural organization, represented by two central carotenoids surrounded by five chlorophyll a molecules, which plays a fundamental photoprotective role in Chl triplet quenching through carotenoid triplet formation.


Assuntos
Proteínas de Ligação à Clorofila/genética , Clorofila/genética , Fotossíntese/genética , Sequência de Aminoácidos , Carotenoides/química , Carotenoides/genética , Clorofila/química , Clorofila/metabolismo , Clorofila A , Proteínas de Ligação à Clorofila/química , Transferência de Energia , Complexos de Proteínas Captadores de Luz/genética , Conformação Proteica , Estramenópilas/genética , Estramenópilas/crescimento & desenvolvimento , Xantofilas/química , Xantofilas/genética
16.
Chemistry ; 20(18): 5271-81, 2014 Apr 25.
Artigo em Inglês | MEDLINE | ID: mdl-24700694

RESUMO

The synthesis and characterization of two new capped silica mesoporous nanoparticles for controlled delivery purposes are described. Capped hybrid systems consist of MCM-41 nanoparticles functionalized on the outer surface with polymer ε-poly-L-lysine by two different anchoring strategies. In both cases, nanoparticles were loaded with model dye molecule [Ru(bipy)3](2+). An anchoring strategy involved the random formation of urea bonds by the treatment of propyl isocyanate-functionalized MCM-41 nanoparticles with the lysine amino groups located on the ε-poly-L-lysine backbone (solid Ru-rLys-S1). The second strategy involved a specific attachment through the carboxyl terminus of the polypeptide with azidopropyl-functionalized MCM-41 nanoparticles (solid Ru-tLys-S1). Once synthesized, both nanoparticles showed a nearly zero cargo release in water due to the coverage of the nanoparticle surface by polymer ε-poly-L-lysine. In contrast, a remarkable payload delivery was observed in the presence of proteases due to the hydrolysis of the polymer's amide bonds. Once chemically characterized, studies of the viability and the lysosomal enzyme-controlled release of the dye in intracellular media were carried out. Finally, the possibility of using these materials as drug-delivery systems was tested by preparing the corresponding ε-poly-L-lysine capped mesoporous silica nanoparticles loaded with cytotoxic drug camptothecin (CPT), CPT-rLys-S1 and CPT-tLys-S1. Cellular uptake and cell-death induction were studied. The efficiency of both nanoparticles as new potential platforms for cancer treatment was demonstrated.


Assuntos
Preparações de Ação Retardada/química , Nanopartículas/química , Polilisina/química , Dióxido de Silício/química , Linhagem Celular Tumoral , Corantes/administração & dosagem , Preparações de Ação Retardada/metabolismo , Células HeLa , Humanos , Lisossomos/enzimologia , Nanopartículas/metabolismo , Nanopartículas/ultraestrutura , Polilisina/metabolismo , Porosidade , Rutênio/administração & dosagem , Dióxido de Silício/metabolismo
17.
18.
Int J Colorectal Dis ; 29(10): 1291-6, 2014 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-25034592

RESUMO

PURPOSE: Inflammatory bowel diseases (IBD) are chronic disorders affecting psychological well-being, quality of life (QOL), social interactions, and close interpersonal relationships of patients affected. The attachment theory provides a theoretical framework to evaluate the quality of close interpersonal relationships in the context of chronic disorders. The aims of this study were to compare the attachment dimensions between IBD patients and healthy controls and to evaluate the impact of these dimensions on QOL in IBD patients. METHODS: One hundred three consecutive IBD outpatients (70 with Crohn's disease and 33 with ulcerative colitis) were recruited in the IBD Unit of the University of Bologna. They were clinically evaluated and filled out the questionnaire Short Form health survey-36 (SF-36), assessing QOL, and the attachment style questionnaire (ASQ), assessing attachment dimensions. One hundred three matched healthy subjects filled out the same questionnaires and represented the control group. RESULTS: IBD patients exhibited worst scores in the QOL measures (both physical and mental health) and in the attachment dimensions Relationships as secondary and Preoccupation with relationships. In IBD, the significant predictors of physical health were disease activity and disease type, while the significant predictors of mental health were disease activity and type, surgery, and the attachment dimensions Confidence and Preoccupation with relationships. CONCLUSIONS: Compared to controls, in IBD patients, the close interpersonal relationships are characterized by attachment insecurity that, in turn, is a significant predictor of QOL. These findings suggest plausible insights for psychological interventions in IBD patients with deterioration in QOL.


Assuntos
Doenças Inflamatórias Intestinais/psicologia , Relações Interpessoais , Qualidade de Vida , Adolescente , Adulto , Idoso , Estudos Transversais , Humanos , Masculino , Pessoa de Meia-Idade , Psicometria , Inquéritos e Questionários , Adulto Jovem
20.
J Phys Chem Lett ; 15(9): 2392-2399, 2024 Mar 07.
Artigo em Inglês | MEDLINE | ID: mdl-38394035

RESUMO

Fucoxanthin Chlorophyll Protein (FCP) is a Light Harvesting Complex found in diatoms and brown algae. It is particularly interesting for its efficiency in capturing the blue-green part of the light spectrum due to the presence of specific chromophores (fucoxanthin, chlorophyll a, and chlorophyll c). Recently, the crystallographic structure of FCP was solved, revealing the 3D arrangement of the pigments in the protein scaffold. While this information is helpful for interpreting the spectroscopic features of FCP, it has also raised new questions about the potential interactions between fucoxanthin and chlorophyll c. These interactions were suggested by their spatial closeness but have never been experimentally observed. To investigate this possible interaction mechanism, in this work, two-dimensional electronic spectroscopy (2DES) has been applied to study the ultrafast relaxation dynamics of FCP. The experiments captured an instantaneous delocalization of the excitation among fucoxanthin and chlorophyll c, suggesting the presence of a non-negligible coupling between the chromophores.


Assuntos
Clorofila , Xantofilas , Clorofila A , Clorofila/química , Análise Espectral , Xantofilas/química , Complexos de Proteínas Captadores de Luz/química
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