Trichobilharzia spp. are avian schistosomes related to medically important human parasites of the genus Schistosoma. Penetrating cercariae are well known as causative agent of cercarial dermatitis in humans. Cercariae actively penetrate the skin of definitive hosts and transform into schistosomula. This process is preceded by cercarial tail detachment and includes emptying of penetration glands and extensive surface changes. One of these changes is the loss of highly immunogenic glycocalyx which represents a protective coat in the aquatic environment. The glycocalyx has specific composition of saccharide molecules which are bound to lipids or proteins on the membrane of cercarial tegument. There is only limited information about the mechanism of shedding. Hypotheses based on indirect evidences suggest that peptidases or (phospho)lipases from penetration glands could be involved. This work describes the changes in surface glycosylation during transformation of cercariae into schistosomula by fluorescently labelled lectins and monoclonal antibodies against Lewis X antigen. Lectins UEA-I, LTA and PNA have been chosen as markers of transformation of T. regenti. Further, our experiments have been focused on shedding of cercarial glycocalyx. During in vitro induction of penetration gland emptying and...

Diante da importância das lectinas no sistema imunológico avaliamos o papel da Nattectina, lectina tipo C identificada no veneno de Thalassophryne nattereri, no desenvolvimento das respostas imunes inata e específica. A Nattectina induziu peritonite em camundongos, caracterizada pelo influxo de neutrófilos e macrófagos, acompanhada da liberação de PGE2, LTB4, IL-1<font face=\"symbol\">b, IL-6, KC, MCP-1, IL-10 e IL-12p70. A resposta imune específica induzida pela Nattectina foi caracterizada pela produção de anticorpos específicos IgG, IgG1 e principalmente IgG2a com síntese de IL-10 e IFN-<font face=\"symbol\">g pelas células esplênicas re-estimuladas in vitro. A incubação de células dendríticas imaturas com a Nattectina gerou maturação destas células com aumento da expressão de moléculas MHC classe II, CD40, CD80, CD86 e expressão de MMP-2 e MMP-9 distribuídas no núcleo e no citoplasma celular, produção das citocinas IL-10 e IL-12p70 e eficiente apresentação antigênica. Concluímos que a Nattectina é capaz de induzir inflamação e resposta imune específica do tipo Th1 mediante a ativação de células dendríticas. / Due to the importance of the lectins in the immunological system we evaluated the role of Nattectin a C-type lectin identified in the venom of Thalassophryne nattereri on development of the innate and specific immune responses. Nattectin induced a significant cellular recruitment into peritoneal cavity of mice, mainly by influx of neutrophils, followed by macrophages, with synthesis of PGE2, LTB4, IL-1<font face=\"symbol\">b, IL-6, KC, MCP-1, IL-10, and IL-12p70. The specific immune response induced by Nattectin was characterized by the production of specific antibodies IgG, IgG1 and mainly IgG2a with IL-10 and IFN-<font face=\"symbol\">g synthesis by splenic cells. Incubation of immature dendritic cells with Nattectin resulted in maturation with up-regulation of MHC class II, CD40, CD80, CD86, and expression of MMP-2 e MMP-9 distributed in nucleus and cytoplasm. Mature dendritic cells produced and release IL-10 and IL-12p70 and present the antigen efficiently. We concluded that Nattectin is able to induce inflammation and Th1 specific immune response through the activation of dendritic cells.

A implantação embrionária e a placentação em cobaios são caracterizadas pela presença trofoblastos que se destacam da placenta principal, semelhantes ao trofoblasto extra-viloso de humanos. Nestes animais ultrapassam os limites, e podem ser encontrados infiltrados no profundamente no endométrio e no em ambiente externo ultrapassando aos limites da parede uterina. A cobaia desenvolve uma importante estrutura fisiológica de troca materno-embrionária, denominada de placenta vitelina invertida, definidas como membrana fetal destituída parcial ou totalmente do revestimento trofoblástico que permite a exposição do endoderma extra-embrionário em contato direto com o tecido materno. Tais características denotam um mecanismo de controle da resposta imune materna distinta dos paradigmas estabelecidos na reprodução humana e de roedores, assim como ratos e camundongos. Sendo a mais intrigante, a destituição do trofoblasto como célula da interface-materno-fetal que controla a tolerância imune-materna.No presente trabalho, procurou-se estabelecer a organização da placenta vitelina de cobaios a partir da identificação das células que compõe esta membrana extra-embrionária e identificar em que momento ocorre à remoção das células trofoblásticas, e a subseqüente forma de interação das células da placenta vitelina na interface com o tecido materno. Para tanto foram utilizados cobaias fêmeas com idade gestacional conhecida, sacrificadas para coleta de segmentos uterinos nos períodos iniciais da gestação e destinados ao processamento histotógico de embebição em parafina. Na ausência de marcadores celulares específicos conhecidos para cobaios, foram realizados testes prospectivos com reações: citoquímicas de PAS e azul de toluidina (AT; um painel de lectinas biotinadas com afinidade específica para diferentes açúcares; e imunocitoquímica para citoqueratina. As reações realizadas com PAS e AT não identificaram populações celulares com marcação seletiva. Contudo dentre as lectinas tetadas, a Erytrina cristagali lectin (ECL) apresentou reação altamente seletiva para a população de trofoblasto mural (TM) que se origina do trofectoderma, mantendo esta reatividade ao longo da gestação. Esta marcação permitiu avaliar temporal e espacialmente o destino destas células que ao longo da gestação eram mantidas como monocamada de TM revestindo externamente a placenta vitelina e, portanto, não expondo as células do endoderma parietal ou visceral ao ecido materno. Pelo acompanhamento do desenvolvimento embrionário nos cortes seriados, foi constatada no interior do blastocisto a organização de duas massas celulares internas em pólos opostos desde a fase de pré-eclosão. Uma das massas celulares constituída de embrioblastos que dará origem aos os folhetos embrionários nas fases subseqüentes, enquanto a outra formada as células tronco trofoblásticas precursora do cone ectoplacentário (CE). A cavidade da blastocele que separa estas duas massas celulares tem a sua parede revestida pelo endoderma parietal em fase tardia, após a formação da cavidade amniótica. Estes achados demonstram a pecularidade da embriogênese no cobaio, diferente daquelas descritas para humanos e outros roedores, não permitem analogias diretas, o que pode ter contribuído para o equívoco na descrição clássica da organização e constituição da placenta vitelina invertida de constituição córion-amniótica. Isto é, o trofoblasto participa da organização da placenta vitelina inicial e permanece na membrana âmnion-córion-vitelina perfazendo todo o limite do embrião ao longo da gestação. Portanto a hipótese da placenta vitelina parcial ou totalmente invertida baseada na descrição clássica em cobaios é decorrente da interpretação equivocada da embriogênese destes animais. / The guinea pig embryo implantation and placentation is characterized by trophoblast cells detaching from the main placenta in a similar way of human extra-villous trophobasts that deeply intrude inside the endometrium and sometimes also found outside the uterine wall. Furthermore, this animal also develops inverted yolk sac placenta defined as fetal membrane partially or fully devoided of trophoblast sheet that allows extra-embryonic endoderma direct exposition to the maternal environment. These characteristics denote a distinct control mechanism of maternal immune response from the established paradigm for human and rodents (rat and mouse) reproduction, being most intriguing the depriving of trophoblast as cells of maternal-fetal interface regulating the maternal immune tolerance. The present work aimed to establish the organization of guinea pig yolk sac based on identification of cell populations composing this membrane and identification if, or, when the trophoblast cells are removed from and subsequent interaction way of yolk sac cell in interface with maternal tissue. It was used pregnant guinea pig sacrificed on established gestational day to collect uterine fragments on early pregnancy stage and processed by conventional paraffin embedding. Due to absence of known specific cell markers for guinea pig, was performed the prospective evaluation using PAS and toluidine blue (TB) cytochemistry and a screening using a panel of biotinylated lectin specific for different sugars and, anti-cytokeratin. The PAS and TB staining did not identify any specific cell population, however, among the lectins used, Erytrina cristagali lectin (ECL) showed high selective labeling to the trophoblast cells originated from the trophectoderm that was kept through the gestational period. This reaction pattern was useful to evaluate chronologically and topologically the fate of this cell and confirmed the constancy of these cells layering the yolk sac placenta in contact with maternal tissue and therefore, endodermal cells were not exposed to maternal environment. Evaluation of embryo development step by step in the serial sections showed the presence of two inner cell mass in opposite sites inside the pre-hatched blastocyst. One of this, was formed with embryoblast that latter will originate the embryonic sheets and the other formed with trophoblast stem cells (ST) will originate the ectoplacental-cone. The wall of blastocele cavity separate these two inner cell mass was initially covered by a single ECL positive mural trophoblast and only later after the amniotic cavity is formed the extraembyonic endodermal cells migrate from the embryonic sheets to cover internally the blastocele cavity to organize the yolk sac placenta. These findings show the peculiarity of guinea pig embryogenesis, quite different from those described for human and rodents and therefore, does not allow direct analogy and seems to contribute in the misunderstanding of classic description of inverted yolk sac placenta and its cellular organization. It means, the trophoblast cell participates in the early organization of yolk sac placenta and remains in chorioamniotic yolk sac fetal membrane constantly limiting the embryo surface in contact with maternal environment. Therefore, the hypothesis of complete or partially inverted yolk sac placenta seems to be a miss understanding of guinea pig embryogenesis.

Pulchellina é uma proteína inativadora de ribossomo (RIP) isolada de sementes de Abrus pulchellus fragmento que codifica a cadeia A da pulchellina (PAC) foi clonado e inserido no vetor pGEX-5X para expressar a cadeia A recombinante (rPAC) como uma proteína de fusão em Escherichia coli. A análise da seqüência de aminoácidos mostrou que a rPAC apresenta uma alta identidade seqüencial (&#62 86%) com a cadeia A da abrina-c. A habilidade que a rPAC possui para depurinar rRNA em ribossomos de levedura também foi demonstrada em testes in vitro. Objetivando verificar a atividade tóxica do produto heterólogo, nós promovemos a associação in vitro da rPAC com a cadeia B recombinante da pulchellina (rPBC). Ambas as cadeias foram incubadas na presença de um sistema de redução/oxidação, originando um heterodímero ativo (rPAB). O rPAB apresentou uma massa molecular aparente de aproximadamente 60 kDa, similar a pulchellina nativa. As atividades tóxicas do rPAB e da pulchellina nativa foram comparadas através da injeção intraperitonial em camundongos, usando diferentes diluições de cada proteína. O rPAB foi capaz de matar 50% dos animais testados com doses de 45&#956g.kg-1. Nossos resultados mostraram que o heterodímero recombinante apresenta tanto toxicidade quanto um padrão conformacional similar a pulchellina nativa. Estudos usando cultura de tecidos também foram realizados com o objetivo de investigar a presença da pulchellina em calos obtidos a partir de sementes de A. pulchellus. Segmentos de cotilédones de sementes imaturas foram inoculados em meio MS suplementado com diferentes concentrações de auxina, citocinina e sacarose para promover a indução dos calos. A expressão da pulchellina nos calos foi monitorada através de RT-PCR e testes de atividade biológica. Os calos obtidos após 35 dias foram congelados, macerados e submetidos a extração de RNA total e proteínas. Um fragmento específico de DNA que codifica a cadeia A da pulchellina foi amplificado a partir do RNA total sugerindo a síntese da proteína nos calos. Isto foi confirmado no extrato bruto de calos, que mostrou atividade hemaglutinante contra sangue de coelho e uma alta toxicidade quando injetado via intraperitoneal em camundongos.O extrato bruto também foi submetido à cromatografia de afinidade em coluna de Sepharose-4B. A fração retida na coluna apresentou duas bandas protéicas quando analisadas em gel de poliacrinamida, sob condições desnaturantes, apresentando um padrão similar ao obtido com a pulchellina de semente. / Pulchellin is a type 2 ribosome-inactivating protein (RIP) isolated from seeds of the Abrus pulchellus tenuiflorus plant. The DNA fiagment encoding Pulchellin A-chain (PAC) was cloned and inserted in pGEX-5X to express the recombinant pulchellin Achain (rPAC) as a fusion protein in Escherichin coli. The deduced amino acid sequence analyses of the rPAC presented a high sequential identity (&#62 86%) with the A-chain of abrin-c. The ability of the rPAC to depurinate rRNA in yeast ribosome was also demonstrated in vitro. Intending to validate the toxic activity we promoted the in vitro association of the rPAC with the recombinant pulchellin binding chain (rPBC). Both chains were incubated in the presence of a reducedloxidized system, yielding an active heterodimer (rPAB). The rPAB showed an apparent molecular mass of about 60 D a similar to the native pulchellin. The toxic activities of the rPAB and native pulchellin were compared by intraperitoneal injection in mice using different dilutions. The rPAB was able to kill 50% of the tested mice with doses of 45&#956g.kg-1. Our results indicated that the recombinant heterodimer presented toxic activity and a conformational pattern similar to pulchellin. Studies using tissue cultures were also performed to investigate the presence of the pulchellin in callus established from seed explants of A. pulchellus. Cotyledon segments of immature seeds were inoculated in basal medium MS supplemented with different concentrations of auxin, citokinin and sucrose in order to determine the best callus induction. The pulchellin expression was monitored in callus cultures by RT-PCR and biological activity. The calli obtained aRer 35 days were freeze dried, macerated and submitted to extraction of total RNA and proteins. A specific DNA fragment codifying the A-chain pulchellin was amplified from callus RNA suggesting the synthesis of the protein. This was confirmed in the calli crude extract that showed haemagglutinating activity against rabbit blood cells and a high intraperitoneal toxicity to mice. The crude extract was also submitted to affinity chromatography on a Sepharose-4B column. The retained protein, showed to be composed by two main bands in polyacrylamide gel electrophoresis, in denaturating conditions, with a similar pattern to the results obtained with seeds pulchellin.

De la reconnaissance protéine-glucides. Une activité lectine avec une spécificité mannose/glucose a été détectée dans les graines de Platypodium elegans, une légumineuse de la sous-tribu Dalbergiae. Le gène de la lectine PELa a été cloné. Son produit est une protéine de 261 acides aminés appartenant à la famille des lectines de légumineuses et présentant des similarités avec l'agglutinine de Pterocarpus angolensis (PAL). La lectine recombinante a été exprimée dans E. coli et renaturée à partir des corps d'inclusion. L'analyse de la spécificité par Glycan Array montre une préférence très rare pour des N-glycanes de type complexe avec des branches disymmétriques. Une branche courte composée d'un résidu de mannose est préférée sur le bras 1-6 des N-glycanes, tandis que l'extension par les résidus GlcNAc et Gal et favorable sur le bras 1-3. Les affinités ont été mesurées par microcalorimétrie de titration en utilisant des heptasaccharides liés à une asparagine et obtenus par une méthode semi-enzymatique. Une très forte affinité de 5 uM a été obtenue pour deux ligands symétriques et disymmétriques. Les structures cristallographiques de PELa complexé avec le trimannose branché et l'heptasaccharide-Asn symétrique de type complexe ont été résolues respectivement à 2,1 et 1,65 Å de résolution. La lectine adopte l'organisation dimérique canonique des lectines de légumineuses. Le trimannose ponte les sites de liaison de deux dimères voisins, résultant en la formation de chaînes infinies dans le cristal. L'heptasaccharide-Asn se lie par le mannose du bras 1-6 dans le site principal de liaison et de nombreux contacts supplémentaires sont établis avec les autres résidus glucidiques. Le GlcNAc du bras 1-3 interagit avec la surface de la protéine dans une conformation contrainte qui peut expliquer la plus grande affinité que l'on observe sur les puces pour les oligosaccharides avec des bras 1-3 courts qui ne contiennent pas ce monosaccharide. / Lectin activity with specificity for mannose and glucose has been detected in the seed of Platypodium elegans, a legume from the Dalbergiae tribe. The gene of the lectin PELa has been cloned and the resulting 261 amino acid protein belongs to the legume lectin family with similarity with Pterocarpus angolensis agglutinin (PAL) from the same tribe. The recombinant lectin has been expressed in E. coli and refolded from inclusion bodies. Analysis of specificity by Glycan Array evidenced a very unusual preference for complex type N-glycans with asymmetrical branches. A short branch consisting of one mannose residue is preferred on the 6- arm of the N-glycan, while extension by GlcNAc, Gal and NeuAc are favorable on the 3-arm. Affinities have been obtained by microcalorimetry using symmetrical and asymmetrical Asn- linked heptasaccharide prepared by semi-enzymatic method. Strong affinity of 5 µM was obtained for both ligands. Crystal structures of PELa complexed with branched trimannose and symmetrical complex type Asn-linked heptasaccharide have been solved at 2.1 and 1.65 Å resolution respectively. The lectin adopts the canonical dimeric organization of legume lectins. The trimannose bridges the binding sites of two neighbouring dimers, resulting in the formation of infinite chains in the crystal. The Asn-linked heptasaccharide binds with the 6-arm in the primary binding site and extensive additional contacts on both arms. The GlcNAc on the 3-arm is bound in a constrained conformation that may rationalize the higher affinity that is observed on chips for oligosaccharide with shorter 3-arm that do not present this monosaccharide.

Lectins are ubiquitous proteins that has domain(s) for recognition and binding to carbohydrates and that can decipher the glicocode in the structures of the glycans linked to soluble glycoproteins and membrane. Molecular interactions based on protein-carbohydrate recognition play key roles in numbers biological processes, such as: cellular communication, gametes recognition, embryonic development, and immune response, among others. Lectins from algae are poorly studied compared to plant lectins and this fact is due to the difficulty of obtaining material for study. The isolectins isolated from red marine alga Solieria filiformis have purification protocols well established. Furthermore, these isolectins have a bacteriostatic effect over gram-negative bacteria and antinociceptive and anti- inflammatory activities. The aim of this study was to determine the primary structure of the isolectins isolated from marine red alga Solieria filiformis. The primary structure of two isoforms (SfL1 and SFL2) were determined by combination of mass spectrometry and molecular biology. The sequences of the two isolectinas were compared to databases (NCBI) and showed similarity to lectins belonging to the family OAAH. The structural similarity of these proteins suggests that bacteria, cyanobacteria and macroalgae are evolutionarily related. Others bioinformatic analysis showed that the SfLs have four internal repeated domains in its sequences as well as presence of an N-glycosylation site and a conserved carbohydrate-binding site with high identity to the CRD from OAAHs. This family of lectins is related to the anti-HIV activity due to its characteristics of binding the high&#8208;mannose&#8208;type N&#8208;glycans. What makes these two isoforms molecules potential for the study of anti-HIV activity. / Lectinas sÃo proteÃnas ubÃquas que possuem domÃnio(s) de reconhecimento e ligaÃÃo a carboidratos e podem decifrar o glicocÃdigo das estruturas dos glicanos associados à glicoproteÃnas solÃveis e de membrana. As interaÃÃes moleculares baseadas no reconhecimento proteÃna-carboidrato desempenham papÃis chave em nÃmeros processos biolÃgicos, tais como: comunicaÃÃo celular, reconhecimento de gametas, desenvolvimento embrionÃrio, reposta imune, entre outras. As lectinas de algas marinhas sÃo pouco estudadas em comparaÃÃo Ãs lectinas de plantas e isso se deve, em parte, à dificuldade de obtenÃÃo de material para estudo. As isolectinas da alga vermelha Solieria filiformis jà possuem protocolo de purificaÃÃo estabelecido. AlÃm disso, jà fora observado efeito bacteriostÃtico contra bactÃrias gram-negativas, atividade antinociceptiva e anti-inflamatÃria para estas lectinas. O objetivo desse trabalho foi determinar a estrutura primÃria das isolectinas da alga marinha vermelha Solieria filiformis. A estrutura primÃria de duas isoformas (SfL1 e SfL2) foi determinada por combinaÃÃo de espectrometria de massas e biologia molecular. As sequÃncias das duas isolectinas foram comparados a sequÃncias depositadas em bancos de dados (NCBI) e houve similaridade com as lectinas pertencentes à famÃlia OAAH. A semelhanÃa estrutural dessas proteÃnas sugere que as bactÃrias, cianobactÃrias e as macroalgas sÃo evolutivamente relacionadas. Outras anÃlises de bioinformÃtica demostraram que as SfLs possuem quatro domÃnios internos repetidos em suas sequÃncias, a existÃncia de um sÃtio de N-glicosilaÃÃo, e um sÃtio de ligaÃÃo a carboidrato conservado e com alta identidade com os sÃtios das OAAHs. Essa famÃlia de lectinas està relacionada à atividade anti-HIV devido a suas caracterÃsticas de ligaÃÃo a N-glicanos ricos em manose. O que torna estas duas isoformas molÃculas potenciais para o estudo de atividade anti-HIV.

Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico / Lectinas podem ser definidas como proteÃnas/glicoporteÃnas que reconhecem carboidratos de maneira especÃfica, mas nÃo participam do metabolismo dos mesmos e nÃo pertencem a nenhuma das principais classes de imunoglobulinas. As lectinas sÃo proteÃnas ubÃquas, estando presente em todos os organismos conhecidos. Em cÃlulas animais, lectinas tÃm sido encontradas no citoplasma, no nÃcleo e associadas a membranas das mais diversas organelas e nos mais variados tipos celulares. Tais lectinas animais podem ser classificadas em famÃlias distintas com base em suas caracterÃsticas fÃsico quÃmicas, funÃÃo e especialmente em sua identidade de estrutura primÃria e terciÃria. O objetivo deste trabalho foi purificar duas novas lectinas da esponja marinha Haliclona (Soestella) caerulea e caracterizar estruturalmente uma delas. EspÃcimes de H.caerulea foram coletados na praia do paracuru, CearÃ. Duas lectinas (H-1 e H-3) foram isoladas por tÃcnicas clÃssicas de quÃmica de proteÃnas. A estrutura primÃria de uma delas foi determinada por espectrometria de massas e RACE. A atividade tÃxica das lectinas foi avaliada frente à nÃuplios de Artemia e cepas das bactÃrias Escherichia coli e Staphylococus aureus. H-1 e H-3 apresentaram caracterÃsticas distinhas da lectina previamente isolada de H. caerulea. H-1 à uma proteÃna monomÃrica de aporoximadamente 40 kDa enquanto que H-3 à uma proteÃna trimÃrica com cadeias com massa aproximada de 9, 16 e 18 kDa. H-3 aglutina eritrÃcitos humanos do tipo A e B e foi inibida GalNAc e PSM, H-1 aglutina diversos grupos sanguineos e nÃo pÃde ser inibida por nenhum aÃÃcar testado. H-1 foi tÃxica a naÃplios de Artemia (LC50=6,4 &#956;g.mL-1) e H-3 foi considerada nÃo tÃxica (LC50=414,2 &#956;g.mL-1). H-3 à uma proteÃna azul, pois interage com um cromÃforo de 597 Da com absorÃÃo mÃxima a 620 nm. A estrutura primÃria de H-3 foi determinada e revelou-se Ãnica, nÃo sendo conhecida nenhuma lectina com estrutura similar. H-3 apresenta um glicano hÃbrido composto por Hex7NAcHex7DeoxiHex2. A cadeia &#945; de H-3 sofre um processamento proteolÃtico complexo que ainda nÃo foi completamente elucidado. AlÃm disso, H-3 foi cristalizada, mas nÃo foi possÃvel a obtenÃÃo de um padraÃo de difraÃÃo que permita a resoluÃÃo da estrutura. Em suma, duas novas lectinas foram isoladas e fora observado pela primeira vez a interaÃÃo entre uma lectina e um cromÃforo natural. Pela primeira vez tambÃm, fora determinada a composiÃÃo glicÃdica de uma lectina de esponja. / Lectins are proteins/glycoproteins that recognize carbohydrate of a specific way, but not participate in the metabolism of the same and do not belong to any of major classes of immunoglobulins. Lectins are ubiquitous proteins, present in all known organisms. In animal cells, lectins have been found in the cytoplasm, in the nucleous and as membrane-associated proteins, in diverse organelles and cells. Animal lectins can be classified into distinct families based on their physicochemical characteristics, especially in their function and identity of primary and tertiary structure. The aim of this study was to purify, characterize structural and biologically new lectins from the marine sponge Haliclona (Soestella) caerulea. H. caerulea specimens were collected in Paracuru beach, CearÃ. Two lectins (H-1 and H-3) were isolated by classical techniques of protein chemistry. The primary structure of H-3 was determined by mass spectrometry and RACE. The toxic activity of lectins was evaluated against Artemia nauplii and Escherichia coli and Staphylococcus aureus strains. H-1 and H-3 showed distinct characteristics of the lectin previously isolated from H. caerulea. H-1 is a monomeric protein of 40 kDa whereas H-3 is a heterogeneus protein with chains of 9, 16 and 18 kDa. H-3 binds human erythrocytes of A and B type and was inhibited by GalNAc and PSM, H-1 binds different blood groups and could not be inhibited by any sugar tested. H-1 was toxic to Artemia nauplii (LC50 = 6.4 &#956;g.mL-1) and H-3 was not considered toxic (LC50 = 414.2 &#956;g.mL-1). H-3 is a blue protein that interacts with a chromophore of 597 Da of maximum absorbance at 620 nm. The primary structure of H-3 revealed a unique amino acid sequence no similar to any animal lectins known. H-3 has a hybrid glycan comprising by Hex7NAcHex7DeoxiHex2. The &#945;-chain of H-3 undergoes complex proteolytic processing that not been fully elucidated. Moreover, H-3 was crystallized, but was not possible to obtain a diffraction pattern that permits solving the structure. In short, two new lectins were isolated and out first observed the interaction between a lectin and natural chromophore. Furthermore, for the first time given the composition glicidic out of a sponge lectin.

De nombreux glycoclusters multivalents des calixarènes, des pillararènes ou des fullerènes ont été synthétisés au sein de notre laboratoire et ont montré d'excellentes affinités pour diverses lectines grâce à leur multivalence et au « glycoside cluster effect ». Nous avons cherché à approfondir ces résultats en ajoutant un degré de dynamisme à ces molécules. Pour cela, nous avons appliqué les concepts de la chimie combinatoire dynamique où des briques moléculaires s'auto-assemblent via des liaisons réversibles pour générer à l'équilibre thermodynamique une chimiothèque d'oligomères. Des briques moléculaires dithiophénols glycosylés sont capables de s'auto-assembler via la formation de ponts disulfures. Leurs propriétés ont été investiguées en chimie combinatoire dynamique et la distribution d'espèces résultant de l'équilibration a montré la formation exclusive des cyclotrimères et cyclotétramères, ou dyn[3]- et dyn[4]arènes. La répétition de l'expérience en présence d'une lectine modèle (ConA) a mené à l'amplification des homodyn[3]- et homodyn[4]arènes. Ces derniers ont été isolés par HPLC semi-préparative et leurs affinités pour ConA ont été mesurées en ITC dans le domaine du nanomolaire. Une extension de cette méthodologie aux lectines LecA et LecB de Pseudomonas aeruginosa est en cours / Several glycoclusters based on calixarenes, pillararenes or fullerenes have been synthesized in our laboratory. They exhibited strong affinities for several lectins through their multivalence and the “glycoside cluster effect”. The prupose of this study was to add a dynamic part to these molecules. We therefore applied the concept of dynamic combinatorial chemistry in which building blocks are able to self-assemble through reversible bonds to generate a library of oligomers. Dithiophenols bearing carbohydrate epitopes can self-assemble through the formation and exchange of disulfide bonds. Their properties in dynamic combinatorial chemistry were studied and the species distribution at the thermodynamic equilibrium revealed the selective formation of cyclotrimers and cyclotetramers named dyn[3]- and dyn[4]arenes. The equilibration in the presence of ConA, used as a model lectin, have led to the amplification of homodyn[3]- and homodyn[4]arenes. These glycodyn[n3,4]arenes have been isolated and their affinities toward ConA measured by ITC in the nanomolar range. Extension of this methodology toward the lectins LecA and LecB of Pseudomonas aeruginosa is in progress

In this thesis the synthesis of several hydrolytically stable carbohydrate mimics with the potential to function as glycosidase or lectin inhibitors are described. This work is presented in Chapters 2-5. Chapters 2 and 3 describe synthetic efforts for producing carbasugars, and include the first synthesis of 1,2-bis-epi-valienamine and the preparation of two previously known aminocarbasugars. All three compounds were synthesised starting from D-mannose, using ring-closing metathesis as the key step. 1,2-Bis-epi-valienamine was found to inhibit Cellulomonas fimi β-mannosidase with a Ki value of 140 mM. Also included is the development of a novel synthetic route from cheap D-fructose to three mannose-mimicking carbasugars using a ring-closing metathesis strategy. Two of the compounds are potential inhibitors of the FimH adhesin. In Chapters 4 and 5 the synthesis of a number of pseudodisaccharides are presented; valienamine- and epi-valienamine-containing pseudodisaccharides and a small library of S-linked pseudodisaccharides were prepared. Various synthetic strategies were explored, including an alkylation strategy, Mitsunobu couplings, and sulfonate displacements. This is the first report on the synthesis of a valienamine pseudodisaccharide with β-lyxo-configuration. Two of the S-linked pseudodisaccharides were found to bind to Concanavalin A with high affinity. The final chapter (Chapter 6) of this thesis focuses on the development of a carbohydrate epimerisation method using transition metal catalysis. Two equilibrium constants involving gluco/manno- and gluco/allo-alcohols were determined via this method. / At the time od doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Submitted. Paper 3: Manuscript. Paper 5: Manuscript.

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