Made available in DSpace on 2015-03-26T13:36:38Z (GMT). No. of bitstreams: 1 texto completo.pdf: 257593 bytes, checksum: 71387e966a71bd5ae61c8e69912ec2e1 (MD5) Previous issue date: 2006-02-15 / Universidade Federal de Viçosa / This study aimed to explore the physiological and biochemical strategies associated to the acclimation of the photosynthetic apparatus due to irradiance attenuation downwards the canopy of coffee plants, as well as the causes of their low photosynthetic rates. Sampling and measurements were made using outer leaves from upper and lower strata from east- and westfaced sides of a coffee hedgerow (north-south orientation). Photosynthetic active radiation (PAR) incident on the canopy varied from 500 to 1850 mmol (photons) m-2 s-1 but PAR effectively intercepted by leaves was smaller, ranging from 20 to 800 mmol (photons) m-2 s-1 for lower leaves, and from 50 to 1400 mmol (photons) m-2 s-1 for the upper ones. In general, net carbon assimilation rate (A) was larger in upper leaves (135%), while internal to ambient CO2 concentration ratio (Ci/Ca) was always larger, and carbon isotope composition smaller, in lower leaves. By contrast, both stomatal (gs) and mesophyll (gm) conductances were similar for both upper and lower leaves. The compensation and saturation irradiances as well as the apparent quantum yield were also similar regardless leaf position. Light-saturated A was relatively low even in upper leaves, suggesting that limitations other than light could be largely associated with the low photosynthetic rates of coffee plants. Initial and total activities of Rubisco, as well as its activation state, varied lightly along the treatments. These results, combined with those from curves A/Ci, suggest that: (i) spatial variation of photosynthetic rates in recently expanded leaves were not a result of biochemical or diffusional limitations, but mainly of photochemical limitations associated with low-light availability; (ii) low photosynthetic rates per se should have resulted mainly from diffusional limitations, as could be deduced from the low values of gs and gm irrespective of leaf position, but not necessarily due to a low mesophyll capacity for CO2 fixation. Even at Ci [>or=] 1000 mmol mol-1 (Ca [~] 1600 mmol mol-1) A was not saturated. In fact, small variations in carbohydrate concentrations as well as in the activities of several enzymes associated with carbon metabolism suggest that the coffee tree presents a low plasticity to adjust its biochemical apparatus for CO2 fixation in response to decreasing light availability. The greatest activities of sucrose-phosphate synthase and fructose-1,6-bisphosphatase in upper leaves appeared to be strongly associated with the greatest photosynthetic rates observed in these leaves in order to guarantee their abilities to maintain sucrose synthesis and export. Photoinhibition of photosynthesis was not observed even in the most exposed leaves. The quantum yield of electron transport was almost always smaller, while the electron transport rate and leaf angles were always larger, in the upper leaves than in the lower leaves. The differences observed in A were not related to a differential allocation of N for the production of photosynthetic pigments, which did not vary along the canopy. Taken together, despite the relatively low values of A, the photosynthetic apparatus of the coffee plants appears to exhibit a relatively low plasticity in response to varying irradiance. / O cafeeiro é originário de ambientes sombreados, exibindo baixas taxas fotossintéticas, mesmo sob condições ótimas de cultivo. No entanto, muito pouco se sabe, nessa espécie, acerca das oscilações espaciais e temporais da fotossíntese, bem como das causas de suas baixas taxas fotossintéticas. Neste estudo, portanto, examinou-se o comportamento diurno das trocas gasosas, da fluorescência da clorofila a e do metabolismo do carbono, em diferentes posições da copa do cafeeiro, investigando-se as estratégias fisiológicas e bioquímicas envolvidas na aclimatação da maquinaria fotossintética, em função da atenuação da irradiância interceptada, ao longo do dossel, em plantas cultivadas em renques orientados no sentido norte-sul. Apesar de a radiação fotossinteticamente ativa (RFA) incidente sobre a copa ter variado, de 500 a 1850 mmol (fótons) m-2 s-1 ao longo dos horários avaliados, a RFA efetivamente interceptada foi bem menor, entre 20 a 800 mmol (fótons) m-2 s-1 para as folhas inferiores, e 50 a 1400 mmol (fótons) m-2 s-1, para as superiores. A taxa de assimilação líquida do carbono (A) foi, em média, 135% maior nas folhas superiores, ao passo que a razão entre a concentração interna e ambiente de CO2 (Ci/Ca) foi sempre maior, e a composição isotópica do carbono menor, nas folhas inferiores, enquanto valores similares das condutâncias estomática (gs) e mesofílica (gm) foram observados, comparando-se folhas superiores e inferiores. Apesar da baixa disponibilidade de luz, observada nos estratos inferiores, tanto as irradiâncias de compensação como a de saturação foram similares entre folhas superiores e inferiores. O rendimento quântico aparente também foi similar entre faces e estratos. A taxa de assimilação líquida de carbono saturada pela luz foi relativamente baixa, mesmo nas folhas superiores, indicando que limitações outras, além da luz, podem estar largamente associadas às baixas taxas fotossintéticas do cafeeiro. As atividades inicial e total da Rubisco, bem como seu estado de ativação, pouco variaram entre faces e estratos. Com efeito, estes resultados, juntamente com os obtidos a partir das curvas A/Ci, sugerem que: (i) as causas da variação espacial das taxas fotossintéticas em folhas recém-expandidas não foram resultantes de limitações bioquímicas ou difusionais, mas, fundamentalmente de limitações fotoquímicas associadas à baixa disponibilidade de luz; (ii) as baixas taxas fotossintéticas per se, em café, devem ser resultantes, particularmente, de limitações difusivas, conforme se infere a partir dos valores baixos de gs e gm, tanto nas folhas superiores como nas inferiores, ao longo de todo o dia, mas não necessariamente devido a uma baixa capacidade mesofílica para fixação de CO2. Mesmo a Ci [>ou=] 1000 mmol mol-1 (Ca [~] 1600 mmol mol-1), não se observou saturação de A, em folhas de ambas as faces e estratos. De fato, as pequenas variações nas concentrações dos carboidratos e nas atividades de várias enzimas associadas com o metabolismo do carbono sugerem que o café apresenta uma baixa plasticidade para ajustar a sua maquinaria bioquímica para fixação do CO2, em resposta à redução da disponibilidade de luz. As maiores atividades da sintase da sacarose-fosfato e da fosfatase da frutose-1,6-bisfosfato nas folhas superiores, em relação às das inferiores, devem estar fortemente associadas com as maiores taxas fotossintéticas observadas nas primeiras, de modo a garantir-lhes a manutenção da síntese e da exportação de fotoassimilados. Não se verificou fotoinibição da fotossíntese, mesmo nas folhas mais expostas à irradiância. O rendimento quântico do transporte de elétrons através do fotossistema II foi quase sempre menor, e a taxa de transporte de elétrons e o ângulo de inclinação foliar sempre maiores, nas folhas superiores em relação às inferiores. As diferenças observadas em A não estiveram relacionadas a diferenças na alocação de N para a produção de pigmentos fotossintéticos, cujas concentrações não variaram ao longo do dossel. Concomitantemente, estes resultados sugerem que, apesar dos valores relativamente baixos de A, o aparelho fotossintético do café exibe uma plasticidade relativamente baixa às variações da RFA.

Made available in DSpace on 2015-03-26T13:39:43Z (GMT). No. of bitstreams: 1 texto completo.pdf: 466511 bytes, checksum: f3030460e9ee9f5dba51df5d32e2b05b (MD5) Previous issue date: 2006-09-19 / Hahnemann in his book The Organon , on the basis of a long time experimentation, reported that in human organisms similar medicines are antagonist to each other and so they loose effectivity. This statement is supported by experimentation in human body but there is no experimental data in plants. The objective of this research was to test the opposing actions of some homeopathic medicines and to obtain conceptual bases of the antagonism in order to develop homeopathic technologies for plants. The trials were conducted in the greenhouse and the Homeopathy Laboratory of Plant Science Department at Federal University of Viçosa, from august to December of 2005. The experiments follow the split plot model being the treatment in the plots and in the subplot was the determination time (10 minutes) and with 4 replicates. It was evaluated the effect of homeopathic preparations on CO2 assimilations of Ruta graveolens L. plants. Test solutions were the dilution of 4 mL of each homeopathic preparation per 1 L of distilled water being poured 1 mL over the soil at 1 cm around the plant. Along the trial, from 7 to 11 a.m. and after pouring the test solution CO2, assimilation data were taken each minute for 10 consecutive minutes by an Infrared Gas Analyzer (IRGA). Data were submitted to analysis of variance, mean test and regression through SAEG Statistical Analysis System which detected treatment influence on CO2 assimilation. The homeopathic treatment Apis mellifica 6CH did counteract pathogenesy effects caused previously in the same plant by Cantharis 4CH meaning that antagonism action did happen. The energy differences resulted from dynamization process of Ruta graveolens 3CH to 12CH homeopathic preparations were detected by plants as shown by CO2 assimilation rate. / Hahnemann no seu livro O Organon , com base em extensa experimentação, relata que medicamentos semelhantes inseridos no organismo têm comportamento antagônico e perdem efetividade. Essa afirmativa tem base na experimentação em seres humanos, mas não tem base experimental em plantas. O trabalho teve como objetivo gerar dados sobre a atuação conflitante de alguns medicamentos homeopáticos e elaborar a base dos conceitos de antagonismo destinada a futuros procedimentos tecnológicos do uso de homeopatia em plantas. Os experimentos foram conduzidos na casa de vegetação e no Laboratório de Homeopatia do Departamento de Fitotecnia da Universidade Federal de Viçosa-MG, no período de agosto a dezembro de 2005. Utilizou-se o esquema de parcela subdividida, tendo nas parcelas os tratamentos e nas subparcelas os tempos de avaliação (10 minutos) com quatro repetições. Foi avaliada a ação dos preparados homeopáticos sobre a planta Ruta graveolens (L.) quantificada pela assimilação de CO2. Os preparados homeopáticos foram aplicados via água destilada na diluição de 4 mL por litro de água destilada e vertido 1 mL da solução a 1 cm do caule e sobre o solo. Durante o ensaio (7 às 11 horas) após verter as soluções foram coletados os dados de assimilação de CO2 em 10 tempos de minuto a minuto no decorrer de 10 minutos consecutivos por tratamento após cada aplicação. A taxa de assimilação de CO2 foi determinada pelo equipamento IRGA (Analisador de Gás no Infravermelho). Os dados foram interpretados por meio da análise de variância, teste de médias e regressão utilizando o programa SAEG (Sistema para Análises Estatísticas). Os preparados homeopáticos provocaram efeito na assimilação de CO2 da planta Ruta graveolens (L.). O preparado homeopático Apis mellifica 6CH anulou a patogenesia causada por Cantharis 4CH significando antagonismo aos efeitos de Cantharis. As diferenças de energia causadas pelo processo físico de dinamização dos preparados homeopáticos Ruta graveolens 3CH a 12CH foram detectadas pelas plantas Ruta graveolens (L.) e retratadas na taxa de assimilação de CO2.

Made available in DSpace on 2016-12-08T16:44:49Z (GMT). No. of bitstreams: 1 PGPV15MA161.pdf: 1173261 bytes, checksum: 4f3f7e28028d6adb4aef09fe8fe8b6be (MD5) Previous issue date: 2015-02-19 / In the management of apple tree in the climatic conditions in southern Brazil, chemical thinning in post-flowering is the most suitable, due to the large climate variability, which can directly affect fruiting. Thus, when it is observed high fruit set, chemical thinning is recommended. However, the availability of products registered for thinning is limited. The metamitron has been reported in recent studies, as effective for the activity of apple fruit thinning due to direct action in the inhibition of photosynthesis. The goal of this study was to test application time and metamitron concentrations and mixtures of metamitron with benzyladenine, and to evaluate the potential raleante this product and its interference in the photosynthetic rate and the following year flowering return in plant apple tree. The experiments were conducted in an experimental orchard Epagri / Caçador Experimental Station - SC, in the 2013/2014 and 2014/2015 seasons. The study is divided into three chapters, the Chapter 1, presented a review of the updated topics covered at work, with information available to the present. Chapters 2 and 3 show results of experiments conducted during this study and are titled as follows: Chapter 2 - Effect of application of metamitron at different times, concentrations and combinations with benzyladenine in chemical thinning post-flowering apple tree, and; Chapter 3 - Balance of photosynthetic content of apple plants treated with metamitron. From the results obtained showed that the metamitron was efficient in reducing the number of fruits per plant and, when applied early, the falling petals (QP) to when the fruits with range between 5mm to 10mm in diameter, increased allocation fruit in larger caliber categories. However, it was not effective in thinning of fruit above 20mm in diameter. The metamitron alone or in mixture with benzyladenine, promoted fruit drop. However, one should be careful with the applied concentration, because, above 1050ppm concentrations can cause excessive thinning. The metamitron decreases the rate of photosynthesis in the first days after application, which returned to normal after the eighth day, in apple plants. Thus, the active principle can be metamitron an important alternative for chemical thinning of apple, since it decreases the number of fruits per plant, increased allocation of the fruits in larger categories. However, larger studies are needed in order to identify possible negative interference with the use of the product in the flowering of return (%) of the following year / No manejo da macieira nas condições climáticas do Sul do Brasil, o raleio químico em pós-floração é o mais indicado, devido a grande variabilidade climática, que pode influenciar diretamente a frutificação. Desta forma, quando é observado elevada frutificação efetiva, o raleio químico é recomendado. No entanto, a disponibilidade de produtos registrados para raleio é limitada. O metamitron foi relatado, em estudos recentes, como efetivo para a atividade de raleio de frutos de macieira devido a sua ação direta na inibição da fotossíntese. O objetivo desse estudo foi testar épocas de aplicação e concentrações de metamitron, bem como misturas de metamitron com benziladenina, além de avaliar, o potencial raleante desse produto, bem como sua interferência na taxa fotossintética e no retorno de floração do ano seguinte em plantas de macieira. Os experimentos foram conduzidos, em pomar experimental de propriedade da Epagri/Estação Experimental de Caçador SC, nas safras 2013/2014 e 2014/2015. O estudo está dividido em três capítulos, sendo que o Capitulo 1, apresentada uma revisão atualizada dos temas abordados no trabalho, com informações disponíveis até o presente. Os Capítulos 2 e 3 trazem resultados de experimentos realizados no decorrer desse estudo e são intitulados da seguinte forma: Capitulo 2 Efeito da aplicação de metamitron em diferentes épocas, concentrações e combinações com benziladenina no raleio químico de pós-floração da macieira, e; Capitulo 3 Balanço do conteúdo fotossintético de plantas de macieira tratadas com metamitron. A partir dos resultados obtidos, se observou que o metamitron foi eficiente na redução do número de frutos por planta e, quando aplicado precocemente, da queda de pétalas (QP) até quando os frutos com alcançam entre 5mm a 10mm de diâmetro, aumentou a alocação dos frutos em categorias de maior calibre. Porém, não foi efetivo no raleio de frutos acima de 20mm de diâmetro. O metamitron aplicado isoladamente ou em mistura com benziladenina, promoveu a queda de frutos. No entanto, deve-se tomar cuidado com a concentração aplicada, pois, concentrações acima de 1050ppm podem causar raleio excessivo. O metamitron promove redução da taxa de fotossíntese nos primeiros dias após a aplicação, que se normalizou a partir do oitavo dia, em plantas de macieiras. Sendo assim, o princípio ativo metamitron pode ser uma importante alternativa para o raleio químico da macieira, visto que promove redução do número de frutos por planta e aumentou a alocação dos frutos em categorias de maior tamanho. Porém, maiores estudos são necessários, afim de identificar possíveis interferências negativas ao uso do produto no retorno de floração (%) do ano seguinte

A importância científica da fotossíntese na geração e permanência da vida no planeta; a necessidade de difusão e incorporação dos conhecimentos científicos nos livros escolares; a hipótese do possível descompasso entre saber científico e saber ensinado, instigaram a busca e análise do percurso da palavra fotossíntese em 50 livros escolares de ciências naturais editados na Espanha (1900-1990) e da trajetória do termo "photosynthesis" em publicações científicas na base de dados ISI-Web of Science (1945-2012). Os critérios para selecionar os livros foram: livros de ciências naturais e datas de edição. Acompanhando a palavra fotossíntese, identificou-se um conjunto de palavras correlatas em significado, embora diferentes na grafia. As palavras foram categorizadas por significados, signos e símbolos, e número de aparecimentos nos livros. O pico máximo de aparecimento da categoria fotossíntese foi na década de 70 e seu percurso nos livros escolares não foi linear nem progressivo. As buscas realizadas na base de dados ISI-Web of Science de 1945 a 2012 mostraram que o número de artigos, de áreas de pesquisa e de periódicos com o termo “photosynthesis” cresceu significativamente entre 1945-1990, 1990-1991 e 1991-2012. A análise dos resultados obtidos fortaleceu a hipótese de um possível descompasso entre o saber científico produzido e o saber ensinado através de livros escolares. Conclui-se que nem sempre a evolução de conceitos científicos é acompanhada no tempo por termos didáticos e que a abordagem metodológica aplicada pode contribuir para outros estudos sobre outros tópicos específicos da ciência, como fotossíntese. Considerações: será que o aumento do número de publicações científicas significa um melhor desenvolvimento, discussão e atualização de conceitos científicos? Este aumento é significativo no sentido do aprimoramento do próprio conceito? Se sim, este aprimoramento poderá formar parte dos livros didáticos de ciências? Estas perguntas, quando respondidas, poderão contribuir para uma maior articulação entre o mundo da ciência e o mundo da educação, em especial no da produção de materiais didáticos como os livros escolares. / The scientific importance of photosynthesis for the generation and persistence of life on the planet; the need to disseminate and incorporate scientific knowledge in textbooks, the possible mismatch between scientific knowledge and taught knowledge, have instigated the search and analysis of the path of the word photosynthesis in 50 textbooks of natural sciences published in Spain (1900-1990) and the trajectory of the term "photosynthesis" in scientific publications in ISI-Web of Science database (1945- 2012). The criteria to examine the books were: books of natural sciences and publication dates. Along with the term photosynthesis, were identified a set of other terms with correlated meanings, although different in spelling. The words were categorized by meanings, signs and symbols, and number of appearances in the books. The peak of onset of photosynthesis category was in the 70s and your pathway in textbooks was neither linear nor progressive. Searches in the database ISI-Web of Science from 1945 to 2012 showed that the number of articles, the areas of research and journals with the term "photosynthesis" grew significantly among 1945-1990, 1990-1991 and 1991-2012. The analysis of the results obtained strengthened the hypothesis of a possible mismatch between scientific knowledge produced and taught knowledge through textbooks. It was concluded that not always the evolution of scientific concepts is followed in time by didactic terms, and that the methodological approach can contribute to the formulation and implementation of other studies related to the so-called scientific knowledge and taught knowledge. Considerations: does the increasing number of scientific publications mean a better development, discussion and updating of scientific concepts? Is this increase significant in the improvement of the concept itself? If yes, will this improvement become part of Natural Science textbooks? These questions, when answered, will contribute to greater interaction between the world of science and the world of education, particularly in the production of teaching materials such as textbooks.

abstract: Over the last century, X-ray crystallography has been established as the most successful technique for unravelling the structure-function relationship in molecules. For integral membrane proteins, growing well-ordered large crystals is a challenge and hence, there is room for improving current methods of macromolecular crystallography and for exploring complimentary techniques. Since protein function is deeply associated with its structural dynamics, static position of atoms in a macromolecule are insufficient to unlock the mechanism. The availability of X-ray free electron lasers presents an opportunity to study micron-sized crystals that could be triggered (using light, small molecules or physical conditions) to capture macromolecules in action. This method of ‘Time-resolved serial crystallography’ answers key biological questions by capturing snapshots of conformational changes associated with multi-step reactions. This dissertation describes approaches for studying structures of large membrane protein complexes. Both macro and micro-seeding techniques have been implemented for improving crystal quality and obtaining high-resolution structures. Well-diffracting 15-20 micron crystals of active Photosystem II were used to perform time-resolved studies with fixed-target Roadrunner sample delivery system. By employing continuous diffraction obtained up to 2 A, significant progress can be made towards understanding the process of water oxidation. Structure of Photosystem I was solved to 2.3 A by X-ray crystallography and to medium resolution of 4.8 A using Cryogenic electron microscopy. Using complimentary techniques to study macromolecules provides an insight into differences among methods in structural biology. This helps in overcoming limitations of one specific technique and contributes in greater knowledge of the molecule under study. / Dissertation/Thesis / Doctoral Dissertation Biochemistry 2018

abstract: Microbial electrochemical cells (MXCs) are promising platforms for bioenergy production from renewable resources. In these systems, specialized anode-respiring bacteria (ARB) deliver electrons from oxidation of organic substrates to the anode of an MXC. While much progress has been made in understanding the microbiology, physiology, and electrochemistry of well-studied model ARB such as Geobacter and Shewanella, tremendous potential exists for MXCs as microbiological platforms for exploring novel ARB. This dissertation introduces approaches for selective enrichment and characterization of phototrophic, halophilic, and alkaliphilic ARB. An enrichment scheme based on manipulation of poised anode potential, light, and nutrient availability led to current generation that responded negatively to light. Analysis of phototrophically enriched communities suggested essential roles for green sulfur bacteria and halophilic ARB in electricity generation. Reconstruction of light-responsive current generation could be successfully achieved using cocultures of anode-respiring Geobacter and phototrophic Chlorobium isolated from the MXC enrichments. Experiments lacking exogenously supplied organic electron donors indicated that Geobacter could produce a measurable current from stored photosynthate in the dark. Community analysis of phototrophic enrichments also identified members of the novel genus Geoalkalibacter as potential ARB. Electrochemical characterization of two haloalkaliphilic, non-phototrophic Geoalkalibacter spp. showed that these bacteria were in fact capable of producing high current densities (4-8 A/m2) and using higher organic substrates under saline or alkaline conditions. The success of these selective enrichment approaches and community analyses in identifying and understanding novel ARB capabilities invites further use of MXCs as robust platforms for fundamental microbiological investigations. / Dissertation/Thesis / Ph.D. Microbiology 2013

abstract: Developing a system capable of using solar energy to drive the conversion of an abundant and available precursor to fuel would profoundly impact humanity's energy use and thereby the condition of the global ecosystem. Such is the goal of artificial photosynthesis: to convert water to hydrogen using solar radiation as the sole energy input and ideally do so with the use of low cost, abundant materials. Constructing photoelectrochemical cells incorporating photoanodes structurally reminiscent of those used in dye sensitized photovoltaic solar cells presents one approach to establishing an artificial photosynthetic system. The work presented herein describes the production, integration, and study of water oxidation catalysts, molecular dyes, and metal oxide based photoelectrodes carried out in the pursuit of developing solar water splitting systems. / Dissertation/Thesis / Ph.D. Chemistry 2013

abstract: A clean and sustainable alternative to fossil fuels is solar energy. For efficient use of solar energy to be realized, artificial systems that can effectively capture and convert sunlight into a usable form of energy have to be developed. In natural photosynthesis, antenna chlorophylls and carotenoids capture sunlight and transfer the resulting excitation energy to the photosynthetic reaction center (PRC). Small reorganization energy, λ and well-balanced electronic coupling between donors and acceptors in the PRC favor formation of a highly efficient charge-separated (CS) state. By covalently linking electron/energy donors to acceptors, organic molecular dyads and triads that mimic natural photosynthesis were synthesized and studied. Peripherally linked free base phthalocyanine (Pc)-fullerene (C60) and a zinc (Zn) phthalocyanine-C60 dyads were synthesized. Photoexcitation of the Pc moiety resulted in singlet-singlet energy transfer to the attached C60, followed by electron transfer. The lifetime of the CS state was 94 ps. Linking C60 axially to silicon (Si) Pc, a lifetime of the CS state of 4.5 ns was realized. The exceptionally long-lived CS state of the SiPc-C60 dyad qualifies it for applications in solar energy conversion devices. A secondary electron donor was linked to the dyad to obtain a carotenoid (Car)-SiPc-C60 triad and ferrocene (Fc)-SiPc-C60 triad. Excitation of the SiPc moiety resulted in fast electron transfer from the Car or Fc secondary electron donors to the C60. The lifetime of the CS state was 17 ps and 1.2 ps in Car-SiPc-C60 and Fc-SiPc-C60, respectively. In Chapter 3, an efficient synthetic route that yielded regioselective oxidative porphyrin dimerization is presented. Using Cu2+ as the oxidant, meso-β doubly-connected fused porphyrin dimers were obtained in very high yields. Removal of the copper from the macrocycle affords a free base porphyrin dimer. This allows for exchange of metals and provides a route to a wider range of metallporphyrin dimers. In Chapter 4, the development of an efficient and an expedient route to bacteriopurpurin synthesis is discussed. Meso-10,20- diformylation of porphyrin was achieved and one-pot porphyrin diacrylate synthesis and cyclization to afford bacteriopurpurin was realized. The bacteriopurpurin had a reduction potential of - 0.85 V vs SCE and λmax, 845 nm. / Dissertation/Thesis / Ph.D. Chemistry 2014

abstract: Photosynthesis is the primary source of energy for most living organisms. Light harvesting complexes (LHC) play a vital role in harvesting sunlight and passing it on to the protein complexes of the electron transfer chain which create the electrochemical potential across the membrane which drives ATP synthesis. phycobilisomes (PBS) are the most important LHCs in cyanobacteria. PBS is a complex of three light harvesting proteins: phycoerythrin (PE), phycocyanin (PC) and allophycocyanin (APC). This work has been done on a newly discovered cyanobacterium called Leptolyngbya Heron Island (L.HI). This study has three important goals: 1) Sequencing, assembly and annotation of the L.HI genome - Since this is a newly discovered cyanobacterium, its genome was not previously elucidated. Illumina sequencing, a type of next generation sequencing (NGS) technology was employed to sequence the genome. Unfortunately, the natural isolate contained other contaminating and potentially symbiotic bacterial populations. A novel bioinformatics strategy for separating DNA from contaminating bacterial populations from that of L.HI was devised which involves a combination of tetranucleotide frequency, %(G+C), BLAST analysis and gene annotation. 2) Structural elucidation of phycoerythrin - Phycoerythrin is the most important protein in the PBS assembly because it is one of the few light harvesting proteins which absorbs green light. The protein was crystallized and its structure solved to a resolution of 2Å. This protein contains two chemically distinct types of chromophores: phycourobilin and phycoerythrobilin. Energy transfer calculations indicate that there is unidirectional flow of energy from phycourobilin to phycoerythrobilin. Energy transfer time constants using Forster energy transfer theory have been found to be consistent with experimental data available in literature. 3) Effect of chromatic acclimation on photosystems - Chromatic acclimation is a phenomenon in which an organism modulates the ratio of PE/PC with change in light conditions. Our investigation in case of L.HI has revealed that the PE is expressed more in green light than PC in red light. This leads to unequal harvesting of light in these two states. Therefore, photosystem II expression is increased in red-light acclimatized cells coupled with an increase in number of PBS. / Dissertation/Thesis / Ph.D. Chemistry 2014

abstract: The first chapter reviews three decades of artificial photosynthetic research conducted by the A. Moore, T. Moore, and D. Gust research group. Several carotenoid (Car) and tetrapyrrole containing molecules were synthesized and investigated for excitation energy transfer (EET), photoregulation, and photoprotective functions. These artificial photosynthetic compounds mimicked known processes and investigated proposed mechanisms in natural systems. This research leads to a greater understanding of photosynthesis and design concepts for organic based solar energy conversion devices. The second and third chapters analyze the triplet energy transfer in carotenoid containing dyads. Transient absorption, time-resolved FTIR and resonance Raman spectra revealed that in a 4-amide linked carotenophthalocyanine dyads the Car triplet state is shared across the larger conjugated system, which is similar to protein complexes in oxygenic photosynthetic organisms. In a carotenopurpurin dyad (CarPur) a methylene ester covalent bond prevents the purpurin (Pur) from influencing the Car triplet based on the transient absorption, time-resolved FTIR and resonance Raman spectra. Thus CarPur resembles the antenna proteins from anoxygenic photosynthetic bacteria. Additional examples of carotenoporphyrin dyads further demonstrates the need for orbital overlap for ultrafast triplet energy transfer and the formations of possible intramolecular charge transfer state. The fourth chapter studies a 4-amino phenyl carotenophthalocyanine and its model compounds using high temporal resolution transient absorption spectroscopy techniques. EET from the Car second excited (S2) state to the phthalocyanine (Pc) was determined to be 37% and a coupled hot ground state (S*)/Pc excited state spectrum was observed. Excitation of the tetrapyrrole portion of the dyad did not yield any kinetic differences, but there was an S* signal during the excited states of the dyad. This demonstrates the EET and photoregulating properties of this artificial photosynthetic compound are similar to those of natural photosynthesis. The last chapter covers the synthesis of silicon Pc (SiPc) dyes and the methods for attaching them to gold nanoparticles and flat gold surfaces. SiPc attached to patterned gold surfaces had unperturbed fluorescence, however the selectivity for the gold was low, so alternative materials are under investigation to improve the dye's selectivity for the gold surface. / Dissertation/Thesis / Ph.D. Chemistry 2014