Hannover, Universiẗat, Diss., 1998.

Hannover, Universiẗat, Diss., 2004.

In the quest to understand the physiological basis of postharvest needle loss in balsam fir, we hypothesized that, volatile terpene compounds (VTCs) have a role in needle abscission. This study focused on understanding the role of VTC’s in postharvest needle abscission. We demonstrated that balsam fir contains twelve VTCs with varying concentrations depending on whether it is a seedling or a clonal tree branch. Total VTC concentration consistently increased prior to needle loss. Five specific VTCs (?-Pinene, ?-Terpinene, Fenchyl acetate, Camphene and 3-Carene) have been identified as possible key signal molecules in needle abscission. VTCs were synthesized independently of ethylene, thus VTCs can be a possible signal molecule to needle abscission. Exposure of branches to ethylene showed an increase in both ethylene and VTC however, total VTC concentration was below the threshold required to cause needle abscission.

Techn. Universiẗat, Diss., 2006--München.

Zugl.: München, Techn. Universiẗat, Diss., 2008.

Universiẗat, Diss., 2001--Jena.

No description available.

Plant sesquiterpene synthases catalyze the conversion of the linear substrate farnesyl diphosphate, FPP, into a remarkable array of secondary metabolites. These secondary metabolites in turn mediate a number of important interactions between plants and their environment, such as plant-plant, plant-insect and plant-pathogen interactions. Given the relative biological importance of sesquiterpenes and their use in numerous practical applications, the current thesis was directed towards developing a better understanding of the mechanisms employed by sesquiterpene synthases in the biosynthesis of such a diverse class of compounds. Substrate preference for sesquiterpene synthases initially isolated from Nicotiana tabacum (TEAS), Hyoscyamus muticus (HPS) and Artemisia annuna (ADS) were optimized with regards to a divalent metal ion requirement. Surprisingly, careful titration with manganese stimulated bona fide synthase activity with the native 15-carbon substrate farnesyl diphopshate (FPP) as well as with the 10-carbon substrate geranyl diphosphate (GPP). Reaction product analysis suggested that the GPP could be used to investigate early steps in the catalytic cascade of these enzymes. To investigate how structural features of the sesquiterpene synthases translate into enzymatic traits, a series of substrate and active site residue contacts maps were developed and used in a comparative approach to identify residues that might direct product specificity. The role and contribution of several of these residues to catalysis and product specificity were subsequently tested by the creation of site-directed mutants. One series of mutants was demonstrated to change the reaction product to a novel sesquiterpene, 4-epi-eremophilene, and while another series successfully transmutated TEAS into a HPS-like enzyme. This is the first report of a rational redesign of product specificity for any terpene synthase. The contact map provides a basis for the prediction of specific configurations of amino acids that might be necessary for as yet uncharacterized sesquiterpene synthases from natural sources. This prediction was tested by the subsequent isolation and validation that valencene synthase, a synthase from citrus, did indeed have the amino acid configuration as predicted. Lastly, an in vitro system was developed for analyzing the interaction between sesquiterpene synthases and the corresponding terpene hydroxylase. Development of this in vitro system is presented as a new important tool in further defining those biochemical features giving rise to the biological diversity of sesquiterpenes.

Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico / O Acetato de lupeol (FAL), isolado do lÃtex extraÃdo do caule de Himatanthus drasticus (APOCYNCEAE), à quimicamente classificado como sendo um triterpeno pentacÃclico pertencente à classe do lupano, foi avaliado em modelos de nocicepÃÃo e inflamaÃÃo. No teste das contorÃÃes abdominais induzidas por Ãcido acÃtico (10 ml/kg, i.p.) em camundongos, a FAL (50 e 100 mg/kg, i.p.) reduziu de forma significativa o nÃmero de contorÃÃes abdominais em 56 e 61%, respectivamente, e a indometacina (10 mg/kg, i.p.) reduziu em 66%. No teste da formalina, a FAL (25 e 50 mg/kg, i.p.) reduziu de forma significativa o tempo gasto pelo animal lambendo a pata, tanto na fase inicial (21 e 46,5%, respectivamente) quanto na fase tardia (57,6 e 61,3%, respectivamente) e a morfina (7,5 mg/kg, i.p.) reduziu em 62 e 91%, respectivamente. O prÃ-tratamento com Naloxona (2 mg/kg, i.p) reverteu de modo significativo, os efeitos da FAL e da morfina tanto na fase inicial quanto na tardia do teste da formalina. No edema de pata induzido por carragenina, a FAL (10, 25 e 50 mg/kg,i.p.) reduziu de modo significativo, o volume do edema na 1Â, 2 e 3 hora apÃs a aplicaÃÃo da carragenina (1%, 50μl, s.p.). AnÃlise histopatolÃgica do tecido de pata de camundongo submetido à carragenina, demonstrou reduÃÃes significativas no edema e do infiltrado celular. Na marcaÃÃo imunohistoquÃmica, em tecido de pata de camundongo submetida ao estÃmulo da carragenina, a FAL (50mg/kg, i.p.) promoveu uma discreta reduÃÃo na expressÃo de TNF- α, porÃm causou uma significante reduÃÃo dos nÃveis de iNOS teciduais. No edema de pata induzido por dextrano, a FAL (12,5 e 25 mg/kg, i.p.) reduziu de modo significativo, o volume do edema na 2 e 3 hora apÃs a aplicaÃÃo de dextrano (12%, 50μl, s.p.). Na peritonite induzida por carragenina, a FAL (1, 10 e 20 mg/kg, i.p.) diminuiu de forma significativa, o nÃmero de leucÃcitos em 56, 80 e 92%, respectivamente. A Pentoxifilina (1 e 25mg/kg, i.p.) inibiu em 39 e 68%, respectivamente o nÃmero de leucÃcitos. No teste da inibiÃÃo da atividade da enzima mieloperoxidase (MPO), a FAL (10, 25, 50 e 100 μg/ml) reduziu a atividade da MPO em 36, 80, 79 e 74 %, respectivamente. A FAL nÃo demonstrou atividade antioxidante no teste do DPPH. Em conjunto, esses dados revelam que a FAL apresenta atividade antinociceptiva, que pode ser explicada pela habilidade deste composto em mimetizar efeitos de opiÃides endÃgenos, e antiinflamatÃria, explicada pela diminuiÃÃo da expressÃo de TNF-α e iNOS, bem como pela diminuiÃÃo da atividades da mieloperoxidase, resultando na inibiÃÃo da migraÃÃo de leucocitÃria para o foco da inflamaÃÃo. / The lupeol acetate (FAL), isolated from the latex extracted of the stem of Himatanthus drasticus (APOCYNCEAE) is chemically classified as a pentacyclic triterpene belonging to the lupane class, was evaluated in nociception and inflammation models. In the writhing test induced by acetic acid (10 ml/kg, i.p.) in mice, FAL (50 and 100 mg/kg, i.p.) significantly reduced the number of writhing in 56 and 61%, respectively, and indomethacin (10 mg/kg, i.p.) reduced by 66%. In the formalin test, FAL (25 and 50 mg/kg, i.p.) significantly reduced the time spent by the animal licking the paw, both in the initial phase (21 and 46.5%, respectively) and in the late phase (57 , 6, and 61.3%, respectively) and morphine (7.5 mg/kg, i.p.) reduced by 62 and 91%, respectively. Pretreatment with naloxone (2 mg/kg, i.p.) significantly reversed the effects of FAL and morphine in both the early and in late phase in formalin test. In the carrageenan induced paw oedema, FAL (10, 25 and 50 mg/kg, i.p.) reduced in significant way the oedema volume in the 1st, 2nd and 3rd hour after carrageenan application (1%, 50μl, s.p.). Histopathologic analysis of mice paw tissue subjected to carrageenan, showed significant reductions in oedema and cellular infiltration. In the immunohistochemical staining in mice paw tissue subjected to carrageenan stimulus, the FAL (50mg/kg, i.p.) induced a slight reduction in the expression of TNF-α, but caused a significant reduction of tissue iNOS levels. In the dextran induced paw oedema, FAL (12.5 and 25 mg/kg, i.p.) significantly reduced the oedema volume in the 2nd and 3rd hour after dextran application (12%, 50μl, s.p.). In carrageenan-induced peritonitis, FAL (1, 10 and 20 mg/kg, i.p.) significantly reduced the number of leukocytes at 56, 80 and 92%, respectively. Pentoxifylline (1 and 25mg/kg, i.p.) inhibited by 39 and 68%, respectively, the number of leukocytes. In the myeloperoxidase (MPO) enzyme inhibition test, FAL (10, 25, 50 and 100 μg/ml) reduced the activity of MPO at 36, 80, 79 and 74%, respectively. The FAL showed no antioxidant activity in DPPH test. Together, these data reveal that the FAL has antinociceptive activity, which can be explained by its ability in mimicking the endogenous opioids effects, and antiinflammatory, explained by TNF-α and iNOS expression decreased, as well as by the myeloperoxidase activity decreasing, resulting in inhibition of leukocyte migration to the focus of inflammation.

Since the 1970's there has been industrial interest in using microorganisms as microcapsules. The encapsulation of actives (e.g. flavours, drugs, perfumes) is a necessary process for pharmaceutical and food companies because the precious and often expensive ingredients must be protected from degradation and also released in a specific site or under a specific stimulus. Saccharomyces cerevisiae, baker's yeast, represents a first choice microorganism for the encapsulation of active ingredients. It is biodegradable and biocompatible with human digestion and skin, and can be produced in an easy and cheap way. A major part of this project has been dedicated to the development of robust methods of extraction and quantification of hydrophobic substances loaded inside yeast cells, which have been subsequently combined with an indirect, fluorescence-based method for the evaluation of the rate of loading of hydrophobic substances in the same cells. In particular, it has been found that this process reaches a limit in the maximal loading capacity of intact yeast cells, most likely reflecting the maximal volume of the lipid droplet organelles in which loaded hydrophobes accumulate. With the new on-line (fluorescence-based) and off-line (chromatography-based) methods developed here it has been established that the loading process fundamentally follows a diffusion model, in which the solubility in water determines the permeation of substances through the cell wall and ultimately their uptake by yeast cells. However, treating yeast cells with organic solvents like DMSO - a new approach introduced in Prof. Tirelli's lab to enhance the encapsulation of hydrophobes - completely changes the chemical-physical parameters of the encapsulation process. In DMSO-treated cells, substances are loaded fundamentally in response to their hydrophobicity. Conversely, once loaded, the same substances are released with a rate that is inversely proportional to their hydrophobicity, as observed by applying a novel approach to measure the release of hydrophobes encapsulated in yeast cells, either in the absence of presence of DMSO-treatment. In conclusion, the new evidence reported here clarifies basic aspects of hydrophobe encapsulation in intact yeast cells and will thus help improving future applications of these microcapsules as a valid, inexpensive and biocompatible drug delivery system.