Pour se protéger des fortes illuminations, les cyanobactéries ont développé un mécanisme de photo-protection nommé qEcya. Sous forte lumière, il diminue la formation d'espèces dérivées de l'oxygène très réactives et dangereuses, en augmentant la dissipation de l'énergie absorbée sous forme de chaleur. L'énergie provenant des phycobilisomes (PBS, les antennes externes des cyanobactéries) atteignant les centres réactionnels est ainsi diminuée. Le mécanisme est induit par l'absorption de la lumière bleue-verte par une protéine photoactive soluble qui attache un caroténoïde : l'Orange Carotenoïd Protein (OCP). Le processus est accompagné d'une diminution de fluorescence réversible. Dans une étude sur les mécanismes de photo-protection sous carence en fer, nous avons montré que le large quenching de fluorescence induit par la lumière bleue-verte est associé à l'OCP et au mécanisme qEcya. Et qu'il n'est pas associé à la protéine IsiA induite sous carence en fer comme cela avait été suggéré dans le passé. Ensuite, j'ai montré que l'OCP et son mécanisme de photo-protection associé sont répandus chez les cyanobactéries à phycobilisomes. Alors que les cyanobactéries contenant l'OCP augmentent leur dissipation d'énergie au niveau des phycobilisomes pour diminuer l'énergie arrivant aux centres réactionnels, il est apparu que les quelques cyanobactéries ne contenant pas l'OCP ont développé une autre stratégie basée sur la dégradation rapide de leurs phycobilisomes en condition de stress. Des résultats préliminaires sur les interactions OCP-PBS sont aussi décrits dans ce travail. Des PBS incubés en présence de l'OCP ont été co-isolés en complexes OCP-PBS dans un gradient de saccharose, même quand seulement des cœurs de PBS ont été mis en présence de l'OCP. Ces résultats suggèrent fortement que l'OCP et les PBS interagissent. Cependant le mécanisme qEcya n'a pas pu être induit in vitro sur ces complexes OCP-PBS purifiés. Le résultat principal de cette thèse est la découverte d'un nouvel acteur essentiel au mécanisme qEcya: une protéine de 13kDa fortement attachée à la membrane. Nous l'avons nommée la Fluorescence Recovery Protein, FRP, car elle est impliquée dans la récupération de l'émission de fluorescence des phycobilisomes dans le mécanisme qEcya après une forte illumination de lumière bleue-verte. La caractérisation de son gène, slr1964, a montré qu'il est conservé en aval du gène de l'OCP chez les cyanobactéries, et qu'il peut être transcrit indépendamment ou co-transcrit avec le gène de l'OCP. De plus, notre étude suggère fortement que l'OCP et la FRP interagissent.

abstract: Natural photosynthesis features a complex biophysical/chemical process that requires sunlight to produce energy rich products. It is one of the most important processes responsible for the appearance and sustainability of life on earth. The first part of the thesis focuses on understanding the mechanisms involved in regulation of light harvesting, which is necessary to balance the absorption and utilization of light energy and in that way reduce the effect caused by photooxidative damage. In photosynthesis, carotenoids are responsible not only for collection of light, but also play a major role in protecting the photosynthetic system. To investigate the role of carotenoids in the quenching of the excited state of cyclic tetrapyrroles, two sets of dyads were studied. Both sets of dyads contain zinc phthalocyanine (Pc) covalently attached to carotenoids of varying conjugation lengths. In the first set of dyads, carotenoids were attached to the phthalocyanine via amide linkage. This set of dyads serves as a good model for understanding the molecular "gear-shift" mechanism, where the addition of one double bond can turn the carotenoid from a nonquencher to a very strong quencher of the excited state of a tetrapyrrole. In the second set of dyads, carotenoids were attached to phthalocyanine via a phenyl amino group. Two independent studies were performed on these dyads: femtosecond transient absorption and steady state fluorescence induced by two-photon excitation. In the transient absorption study it was observed that there is an instantaneous population of the carotenoid S1 state after Pc excitation, while two-photon excitation of the optically forbidden carotenoid S1 state shows 1Pc population. Both observations provide a strong indication of the existence of a shared excitonic state between carotenoid and Pc. Similar results were observed in LHC II complexes in plants, supporting the role of such interactions in photosynthetic down regulation. In the second chapter we describe the synthesis of porphyrin dyes functionalized with carboxylate and phosphonate anchoring groups to be used in the construction of photoelectrochemical cells containing a porphyrin-IrO2·nH2O complex immobilized on a TiO2 electrode. The research presented here is a step in the development of high potential porphyrin-metal oxide complexes to be used in the photooxidation of water. The last chapter focuses on developing synthetic strategies for the construction of an artificial antenna system consisting of porphyrin-silver nanoparticle conjugates, linked by DNA of varied length to study the distance dependence of the interaction between nanoparticles and the porphyrin chromophore. Preliminary studies indicate that at the distance of about 7-10 nm between porphyrin and silver nanoparticle is where the porphyrin absorption leading to fluorescence shows maximum enhancement. These new hybrid constructs will be helpful for designing efficient light harvesting systems. / Dissertation/Thesis / Ph.D. Chemistry 2011

Les problèmes d’hyperpigmentation cutanée sont caractérisés par l’apparition de taches brunes foncées, distribuées irrégulièrement sur la peau, généralement sur les zones photo-exposées. Ce problème largement répandu est la conséquence de plusieurs perturbations cutanées d’une ampleur autant physiologique qu’esthétique. Les rayonnements ultraviolets (UV) jouent un rôle important dans la mélanogenèse mais sont aussi à l’origine de plusieurs dérèglements physiologiques des mélanocytes induisant ainsi leur mal-fonctionnement.L’application d’un écran solaire est un moyen très efficace pour la protection contre les UV et la prévention des problèmes d’hyperpigmentation cutanée. Pour la première fois, nous avons pu mettre en place une nouvelle méthode in vitro pour la détermination du facteur de protection solaire (SPF) d’un écran en utilisant le film Gafchromic® EBT3 comme substrat et en se basant sur le changement de couleur du substrat. La variation de couleur est évaluée par spectroscopie ultraviolet-visible et est rapportée à l’absorbance du film après son exposition à un simulateur de soleil.En plus, nous nous sommes intéressés à la recherche de principes actifs extraits de plantes pour la régulation des problèmes d’hyperpigmentation cutanée. Pour ce, des huiles essentielles (HE) ont été extraites à partir de cinq plantes indigènes ou endémiques au Liban et leur composition analysée par chromatographie en phase gazeuse couplée à la spectrométrie de masse (GC-MS). Leurs effets moléculaires sur les structures cutanées ont été déterminés par analyses in tubo et in vitro. Les analyses enzymatiques in tubo ont permis de détecter une activité anti tyrosinase importante des deux HE d’Origanum syriacum et Origanum ehrenbergii. Cette activité a été liée à la composition phytochimique de chaque HE et a été attribuée au composé majoritaire, le carvacrol. Les études in vitro sur des cultures de mélanocytes ont permis de déterminer une diminution significative de la production de la mélanine en présence des HE et du carvacrol. Nous avons pu établir un lien entre les deux études pour déterminer le mécanisme d’action du carvacrol. Il s’agit d’une inhibition compétitive où le carvacrol se lie à la tyrosinase pour suivre une série d’oxydations enzymatiques bloquant ainsi l’oxydation de la tyrosine et causant un dérèglement de la mélanogenèse.Notre étude est la première à démontrer l’activité anti tyrosinase des HE d’O. syriacum et d’O. ehrenbergii. La complémentarité entre les tests d’efficacité et les analyses GC-MS nous a permis d’attribuer l’activité anti tyrosinase au carvacrol qui agit par inhibition compétitive.Ainsi, l’application de protecteur solaire associée à l’application cutanée de régulateurs de la mélanogenèse pourrait être une solution efficace pour les problèmes d’hyperpigmentation cutanée. / Hyperpigmentation disorders are characterized by an irregular distribution of dark spots on the skin, mainly on photo-exposed skin areas. This widespread problem is the result of several skin disorders leading to many physiological and aesthetic perturbations. Ultraviolet (UV) radiations play an important role in melanogenesis. However, they are also the source of several physiological disorders that induce a malfunctioning of melanocytes.The application of sunscreen is a very effective UV protection method and it is considered a main factor in the prevention of skin hyperpigmentation problems. One of the novelties in our research is that, for the first time, we were able to establish a new in vitro method for the determination of the sun protection factor (SPF) of a sunscreen, using EBT3 Gafchromic® film as a substrate. Our method relied on the color change of the substrate that was evaluated by UV-visible spectrophotometric measurements and valued by the absorbance of the film exposed to a solar simulator.In addition, we were interested in discovering new plant-derived active ingredients for the regulation of skin hyperpigmentation disorders. For this process, five essential oils (EO) of indigenous or endemic plants to Lebanon were extracted and their composition was studied by gas chromatography coupled to mass spectrometry (GC-MS). We studied as well their molecular effects on cutaneous structures by in tubo and in vitro analysis. In tubo enzymatic analysis allowed us to identify an important anti tyrosinase activity of the two EO of Origanum syriacum and Origanum ehrenbergii. This activity was linked to the phytochemical composition of the EO and was assigned to the presence of their main component, carvacrol. In vitro cell cultures of melanocytes enabled us to determine a significant reduction in the melanin production in the presence of the EOs and carvacrol. Furthermore, we were able to define the mechanism of action of carvacrol by linking both in tubo and in vitro studies: carvacrol binds to tyrosinase and undergoes a series of oxidation reactions, thus preventing the oxidation of tyrosine. This mechanism is called competitive inhibition and it disturbs the regular pathway of melanogenesis.Our study is the first to demonstrate the anti tyrosinase activity of the EO of O. syriacum and O. ehrenbergii. The complementarity between efficacy tests and the phytochemical GC-MS analysis was our tool to discover that tyrosinase inhibition is mainly due to the presence of carvacrol that acts by competitive inhibition.Thus, the application of a sunscreen paired with the application of cutaneous melanogenesis regulator could be an effective solution for skin hyperpigmentation disorders.

[pt] O Sol é essencial para a vida na Terra e traz muitos benefícios ao homem, porém a sua incidência em excesso pode causar alguns distúrbios e doenças. A radiação solar afeta a pele, causando aumento do risco de câncer cutâneo, fotoenvelhecimento e exacerbação de dermatoses fotossensíveis. Para prevenir essas patologias, uma das opções é o uso de fotoprotetores, que geralmente são emulsões para uso tópico contendo filtros de radiação UV. Eles representam uma fatia importante do mercado de cosméticos e vêm se mostrando um segmento comercialmente promissor, além de ser um nicho relevante dentro da ciência cosmética para pesquisas e desenvolvimento tecnológico. A formulação de emulsões de fotoprotetores é complexa e pode envolver vários ingredientes como filtros orgânicos, filtros inorgânicos, emolientes, emulsionantes, umectantes, água e ainda conservantes, fragrâncias, ativos de tratamento, anti-oxidantes ou corantes, sendo cada um deles adicionado ou na fase aquosa ou na fase oleosa, a depender de sua polaridade. Dentre as substâncias que compõem a fase oleosa deste tipo de emulsão, podem-se destacar os emolientes e os filtros orgânicos. Diferentes classes de emolientes resultam em modificações físicoquímicas e sensoriais dos cosméticos, que são muito relevantes para uma boa aplicação. O objetivo deste projeto é estudar a influência de diferentes composições de fase oleosa, modificando-se os emolientes utilizados nas emulsões e comparando amostras com e sem filtros orgânicos, correlacionando as características dos emolientes com os resultados experimentais de caracterização das emulsões. Estas informações possibilitarão desenvolver estratégias para maior assertividade na escolha de emolientes a serem utilizados em emulsões para fotoproteção e controlar as propriedades do produto de acordo com as necessidades do consumidor e demandas de marketing das empresas cosméticas. A metodologia consiste em preparar duas versões de conjuntos de formulações, fixando-se o tipo e concentração de emulsionante e co-emulsionante, a concentração de fase oleosa e o método de preparação. A primeira versão é um conjunto de 7 amostras, em que se modifica a composição da fase oleosa alterando o emoliente utilizado. Já a segunda versão é outro conjunto de 7 amostras, porém com a adição de uma mistura de 3 filtros orgânicos comumente utilizados em fotoproteção. Após o preparo das amostras, são feitos testes de estabilidade e caracterização das propriedades físico-químicas através de análise visual, centrifugação, reologia, microscopia e difração de laser. Os resultados da caracterização indicam que a alteração da composição da fase oleosa por utilização de diferentes emolientes modifica o comportamento da emulsão formada. Foram encontrados diferentes perfis de distribuição de tamanhos de gota nas análises de microscopia e difração de laser, assim como diferenças nas curvas de fluxo, viscosidade e módulos de perda e armazenamento nas análises reológicas. A estabilidade preliminar também aponta que há dependência do emoliente utilizado com o tempo em que a emulsão permanece estável. Após a adição da mistura de filtros orgânicos, ocorrem mais alterações nas características das emulsões e as tendências de estabilidade são alteradas devido às interações entre os filtros orgânicos e os emolientes. Logo, o estudo permite maior previsibilidade e controle das propriedades de formulações de emulsões com ou sem filtros orgânicos. / [en] The Sun is essential for life on Earth and brings many benefits to the human beings, but its incidence in excess can cause some disorders and diseases. Solar radiation affects the skin, causing an increased risk of skin cancer, photoaging and exacerbation of photosensitive dermatoses. To prevent these pathologies, one of the options is the use of sunscreens, which are usually emulsions for topical use containing UV filters. They represent an important part of the cosmetics market and have shown to be a commercially promising segment, in addition to being a relevant niche within cosmetic science for research and technological development. The formulation of sunscreen emulsions is complex and may involve several ingredients such as organic filters, inorganic filters, emollients, emulsifiers, humectants, water and even preservatives, fragrances, treatment actives, anti-oxidants or dyes, each one being added or in the aqueous phase or in the oil phase, depending on its polarity. Among the substances comprising the oily phase of this type of emulsion, emollients and organic filters can be highlighted. Different classes of emollients result in changes of physicochemical and sensorial properties of cosmetics, which are very relevant for a good application. The objective of this project is to study the influence of different compositions of the oil phase, modifying the emollients used in the emulsions and comparing samples with and without organic filters, correlating the characteristics of the emollients with the experimental results of emulsion characterization. This information will allow developing strategies for greater assertiveness in the choice of emollients to be used in sunscreen emulsions and to control the properties of the product according to consumer needs and marketing demands of cosmetic companies. The methodology consists of preparing two versions of sets of formulas, fixing the type and concentration of emulsifier and co-emulsifier, the concentration of the oil phase and the method of preparation. The first version is a set of 7 samples, in which the composition of the oil phase is modified by changing the emollient used. The second version is another set of 7 samples, but with the addition of a mixture of 3 organic filters commonly used in sunscreens. After preparing the samples, stability tests and characterization of the physicochemical properties are performed through visual analysis, centrifugation, rheology, microscopy and laser diffraction. The characterization results indicate that changing the composition of the oil phase by using different emollients modifies the behavior of the emulsion formed. Different droplet size distribution profiles were found in laser diffraction analyses, as well as differences in flow curves, viscosity and loss and storage modulus in rheological analyses. Preliminary stability also indicates that the emollient used depends on the time the emulsion remains stable. After the addition of the mixture of organic filters, more changes in the emulsion properties and trends of stability occur. Therefore, the study allows greater predictability and control of the properties of emulsion formulations with or without organic filters.

Made available in DSpace on 2015-07-22T20:50:07Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-08-25 / As relações entre Trabalho e Saúde neste estudo tiveram por base possíveis agravos originados de exposições prolongadas e repetidas ao sol sem a devida proteção. Objetivou-se analisar as atitudes e práticas face à exposição solar dos carteiros do Município de Juazeiro do Norte-CE, identificando quais os recursos e como são utilizados por eles para se protegerem da ação nociva do sol. Objetivou- se também identificar a existência de iniciativa por parte da Empresa de Correios e Telégrafos no sentido de fornecer aos trabalhadores a adoção de recursos para fotoproteção. Tratou-se de um estudo de corte transversal, com abordagem quantitativa. O estudo foi realizado na Empresa de Correios e Telégrafos da cidade de Juazeiro do Norte- CE, envolvendo 25 carteiros, sendo 23 homens e 2 mulheres, com média de idade 35,84 anos. A coleta dos dados foi realizada por meio de um questionário contemplando variáveis de caracterização do grupo, conhecimento sobre os efeitos nocivos dos RUVs, práticas de exposição solar e medidas preventivas relevantes à fotoexposição. Para análise estatística, foi utilizado o programa Statistical Package for the Social Sciences (SPSS) versão 13.0 e realizou- se uma análise descritiva.Dos carteiros pesquisados a maioria foi do sexo masculino (92%) e a média da idade foi de 35,84 anos e todos tinham um bom nível de escolaridade. Em relação ao tempo de vinculo empregatício, a maioria dos carteiros tem mais de 9 anos de trabalho. Quanto ao horário de trabalho externo, todos os carteiros o realizam a partir das 11h00min e retornam a sede dos correios entre às 16h00min e 18h00min. Em relação ao fototipo cutâneo, 56% dos carteiros enquadram- se no fototipo III e o restante distribui- se entre os II, IV e V.Em relação ao fator de proteção 22 carteiros utilizam o fator 30. Quanto ao fornecimento dos correios do filtro solar, 56% responderam que ocorre semanalmente, independentemente de estar faltando ou não o produto.Pode-se concluir que a maioria dos carteiros utiliza meios para proteção solar, no entanto não realizam esta proteção da forma mais adequada. Quanto aos Correios, identificamos que a instituição contribui parcialmente no sentido de fornecer aos trabalhadores investigados recursos para fotoproteção. / The relations between Work and Health in this study have been based on likely damages from long, repeated exposition to the sun without the necessary protection. It has been aimed to analyze the attitudes and practices to solar exposition of Juazeiro do Norte mailmen, we have identified what resources and how they are used by the mailmen in order to protect them from the sun’s harmful rays. It has also been aimed to identify the existence of initiative from the Brazilian Post Company in Juazeiro do Norte city, there are 25 mailmen involved all in all, they are 23 men and 2 women and their age is 34. 84 at average. The data collect has been made through a questionnaire covering variables of group characterization, knowledge about harmful effects of UVRs practices of solar expositions and preventive steps relevant to photo exposure. For statistics analyses, the Statical Package for the Social Sciences program was used (SSPS) 13.0 version and a descriptive analysis. Among the post officers surveyed, most of them are male (92%) and the age average has been 35.85 years and all had a good education level. When it comes to time of employing link, most of post officers have worked for over nine years. In relation to working time, most post officers work from 11:00 am and they get back to the headquarters at about 4:00 pm to 6:00 pm. In relation to cutaneous photo type, 56% post officers fit in photo type III and the rest in II, IV and V groups. In relation to protection factor, 22 post officers utilize factor 30. In relation to the supply of sun screen, 56% answered that it happens every week, independently to lack or not the product. In conclusion, every post man uses some kind of sun protection, nevertheless, they do not do this protection correctly. In relation to the Post Office, we have observed that the company contributes partly in order to supply its investigated clerks resources to protection. / TEDE

[pt] A irradiação solar é vista como uma importante fonte de dano aos cabelos, contudo, medir instrumentalmente as consequências da sua interação com os diferentes constituintes da fibra capilar ainda é um desafio. Neste trabalho, investigou-se o potencial da metodologia de flexabrasão em medir as alterações nas propriedades mecânicas de fibras de cabelo decorrentes dos danos estruturais ocasionados pelas radiações solares. Para isto, desenvolveu-se um experimento in-vitro, no qual amostras de cabelo humano, simulando diferentes níveis de sensibilização química (natural, descolorido, colorido e alisado com formaldeído), foram submetidas a diferentes níveis de radiação emitida por uma lâmpada de xenônio. Após análise estatística dos dados obtidos, observou-se que a metodologia de flexabrasão é capaz de captar a influência da radiação solar na resistência mecânica de fibras de cabelo, sobretudo em cabelos naturais a partir de 60 horas de exposição à lâmpada de xenônio, o que equivale aproximadamente a 5 meses de exposição solar na cidade do Rio de Janeiro, para pessoas que ficam diretamente expostas ao sol por cerca de 1,5 h por dia. Desta forma, concluiu-se que a flexabrasão é uma possível metodologia para avaliação do fator de proteção solar oferecido por produtos cosméticos capilares. / [en] Solar radiation is an important source of damage to hair fibers. However, it is still a huge challenge to instrumentally measure the consequences of its interaction with the fibers constituents. In this work, the flexabrasion methodology has been investigated as a potential tool to quantify the alterations on hair mechanical properties due to structural damages caused by solar radiation. For that, an in-vitro experiment has been developed, in which human hair samples, simulating different levels of chemical sensitization (natural, bleached, dyed and straightened with formaldehyde), were submitted to different levels of radiation from a xenon lamp source. Statistical analysis of the data obtained with the methodology showed that it is able to capture the influence of solar radiation on hair mechanical resistance, especially when using natural fibers from 60 hours of exposure onwards, what would be equivalent to around 5 months of real solar exposure at Rio de Janeiro, on people that are directly exposed to the sun during 1,5 h per day. Thus, one can conclude that flexabrasion is a methodology option to evaluate the photo protection efficacy offered by hair care products.