Carbohydrates constitute the most abundant class of natural products in the living world and they play various roles. They are notably involved in cell-cell interactions and immune reactions. It has been observed that tumor cells express, on their surface, unusual oligosaccharides named Tumor-Associated Carbohydrate Antigen (TACA). One TACA of interest to our research group is the Lewis A Lewis X hexasaccharide that is displayed on the surface of squamous lung carcinoma cells. Since carbohydrates are involved in immune reactions and can be recognized by antibodies, it becomes possible to design a carbohydrate-based vaccine against these tumor cells. This thesis describes the total synthesis of the TACA Lewis A Lewis X hexasaccharide and the preparation of two fragments: one tetra- and one pentasaccharide. These molecules were prepared as hexyl and aminohexylglycosides. In addition, the hexasaccharide was synthesized as a disulfide. This diversity of these synthons will allow conjugation to a protein, analysis by nuclear magnetic resonance techniques, and immobilization on gold of the antigen. Without doubt, this work is a significant contribution to the development of an anti cancer vaccine as it constitutes the first stage of the process.

Equitable romantic relationships are relationships in which partners perceive that they are giving benefits to their partner that equal the benefits they receive from their partner (e.g., Walster, Traupmann, & Walster, 1978), and such relationships promote commitment (Rusbult, 1980). But do equity considerations influence observers’ impressions of a romantic couple? In the present study, I tested this possibility by examining observers’ impressions of romantic partners who were mismatched in physical attractiveness (i.e., one partner will be more physically attractive than the other). In this situation, heterosexual observers instinctually categorize the opposite-sex member of the couple as a potential mate and the same-sex member of the couple as a competitor for the potential mate’s affection (e.g., Buss & Dedden, 1990; Fisher & Cox, 2009). Furthermore, observers also conclude that a potential mate who is more attractive than his or her current partner (i.e., the competitor) is not committed to his or her current relationship (Stinson & Reddoch, unpublished data). Thus, when evaluating a romantic couple, I hypothesize that observers’ will demonstrate mating-motivated biased perceptions of potential mates and competitors when the mate is more attractive than the competitor, because such more-attractive potential mates will be perceived as romantically “available.” Participants viewed photos of dating couples who matched in attractiveness, or viewed photos of dating couples where the mate was more attractive or less attractive than the competitor. Participants then rated the potential mates’ and competitors’ status-resources (SR; Fletcher et al., 1999). Results supported my theory of mating-motivated person-perception: Observers derogated the SRs of competitors who were paired with a more attractive (and romantically available) potential mate. / Graduate / 0623 / 0451 / c.joordens@gmail.com

Conjugation is a fundamentally important mechanism of horizontal DNA transfer between bacteria, bacteria x archea, and bacteria x eukaryotes. This work has concentrated on conjugation between bacteria x eukaryotes, specifically Escherichia coli x Saccharomyces cerevisiae. Four hypotheses were tested, investigating the barriers to this particular form of DNA transfer. The first investigated if a mutation that altered the cell-surface of the recipient S. cerevisiae could inhibit DNA transfer. The final three utilised a recombination-dependent-conjugation assay to investigate the barrier to DNA transmission through recombination. The hypotheses tested if the frequency of recombination, in this recombination-dependent-conjugation assay, differed when using similar or diverged DNA substrates, if a mismatch repair mutation within the recipient could affect the frequencies of recombination observed, and if the position on the plasmid of the gene of interest affected the frequency of transmission. Transmission of the Ura3 DNA sequence in the recipient S. cerevisiae was used to test all four hypotheses. The cell wall mutants mnn9, knr4, fks1 and kre6 were utilised to investigate if the cell-surface of the recipient could affect the frequency of transmission. The similar and diverged substrates utilised in the investigation of the affect of sequence similarity on recombination were the DNA sequences of ura3 from S. cerevisiae and Saccharomyces carlsbergensis, respectively and the MMR mutants utilised were msh2, pms1 and pol30-52. Cell wall mutants were not found to limit the frequency of transfer once donor-recipient contact was induced through the solid surface mating procedure. Sequence similarity, MMR and the relative position of the ura3 DNA sequence on the conjugative plasmids were shown to have little effect on the frequency of transmission in S. cerevisiae. This suggests that any DNA that enters the nucleus of S. cerevisiae (eukaryotes) can recombine with the chromosome and alter it to the same extent. However, trends within the data also suggest that DNA is transferred into the recipient and then transported to the nucleus to recombine with the chromosome as a single-stranded DNA molecule.

Universiẗat, Diss., 2001--Mainz.

Submitted by Reginaldo Soares de Freitas (reginaldo.freitas@ufv.br) on 2017-03-29T11:03:04Z No. of bitstreams: 1 texto completo.pdf: 3774617 bytes, checksum: 197f3ca5359c93c3476e850581110d85 (MD5) / Made available in DSpace on 2017-03-29T11:03:04Z (GMT). No. of bitstreams: 1 texto completo.pdf: 3774617 bytes, checksum: 197f3ca5359c93c3476e850581110d85 (MD5) Previous issue date: 2013-04-16 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / O arsênio (As) é um elemento não só tóxico, mas também altamente genotóxico aos seres vivos. Muitas lacunas precisam ser preenchidas com relação aos processos causadores de toxidade do As em plantas, bem como os mecanismos de tolerância e sensibilidade a este metalóide. Para isso, plantas de Arabidopsis thaliana (WT, mutantes msh2 e transgênicas repórteres em mutações) e Allium cepa foram expostas a 0, 2, 8 e 16 mg As L -1, durante cinco dias, em sistema hidropônico ou em meio de cultura. As plantas acumularam grandes teores de As nas raízes e apresentaram elevado fator de translocação para a parte aérea, e também alterações no acúmulo de nutrientes. Os sintomas visuais se intensificaram com o aumento da concentração de As na solução nutritiva. As raízes adquiriram coloração escura e aspecto gelatinoso, danificado e aumento no comprimento e densidade dos pêlos; a parte aérea apresentou aumento dos teores de antocianinas e sinais de senescência precoce, bem como alterações na espessura de tecidos. O estresse oxidativo e a redução dos teores de fósforo foram apontados como os principais efeitos do As capazes de causar toxidez, evidenciando os danos indiretos deste elemento no organismo. Foram verificadas importantes alterações fotossintéticas, bem como indícios de danos ao processo de respiração celular devido o aumento da expressão de genes codificantes de oxidases alternativas. Também foram observadas alterações nos teores de açúcares em folhas jovens, maduras e raízes. O As promoveu fragmentação do DNA nos ápices radiculares de A. cepa e aumento das taxas de mutação pontual e de recombinação-não homóloga em A. thaliana. O significativo aumento da expressão dos genes msh2 e msh7, codificadores de enzimas-chave do processo mismatch repair, que realiza o reparo de bases danificadas ou erroneamente inseridas no DNA, sugeriu a importância deste mecanismo no combate à genotoxidade do As em A. thaliana. Isso foi confirmado pela maior sensibilidade observada nas plantas mutantes msh2 ao As, detectada visualmente via aumento da peroxidação de lipídios. Observou-se inibição da atividade da protease caspase-3, associada ao processo de morte celular programada, reforçando a capacidade de inibição da atividade enzimática pelo As. / Arsenic (As) is not only a toxic element, but also highly genotoxic to living organisms. Several gaps in our understanding of As toxicity in plants need to be filled, including the mechanisms that result in tolerance and sensitivity to this metalloid. For this reason Arabidopsis thaliana plants (WT, msh2 mutants and transgenic reporters in mutation process) and Allium cepa were exposed to 0, 2, 8 e 16 mg As L -1, for five days, in a hydroponic system or in culture medium. The plants accumulated large amounts of As in roots and presented a high translocation factor to the shoot, and also showed changes in nutrient accumulation. The visual symptoms have intensified with the increasing of As concentration in the nutritive solution. Roots showed dark coloration and a damaged and gelatinous aspect, with increased roots hair length and density. The shoots showed accumulation of anthocyanins and signs of early senescence, as well as changes in tissue thickness. Oxidative stress and reduction of phosphorus concentration in tissues have been implicated as the main cause of toxicity, evidencing the indirect damage from this element in the organism. Important changes in photosynthesis were observed, as signs of damage to respiration, due to increased expression of alternative oxidase genes. Thus, changes in the levels of synthesis and utilization of sugars by plants were observed. As promoted DNA fragmentation in A. cepa and increased rates of point mutation and nonhomologous recombination. The significant increase in the expression pattern of the msh2 and msh7 genes, which encode key enzymes in DNA repair process, suggests the importance of this mechanism in defense against As genotoxicity in A. thaliana. This was confirmed by the greater sensitivity observed in msh2 mutants to As as indicated by visual symptoms and by an increase in lipid peroxidation. Inhibition of the activity of the caspase-3 protease was also observed, evidencing the As capacity of enzyme activity inhibition. / Tese enviada pela secretaria do curso por e-mail, em 28-03-17.

The objective of this essay is to explain if there exist a mismatch on the Swedish labour market, with a main emphasis on overeducation. We frame our empirical work according to mismatch theories the human capital theory, technological change theory and the education-occupation mismatch theory. Using panel data from the European Social Survey covering the period 2002 and 2016 were we able to define overeducation at different levels to observe which is the most suitable for the topic of this essay. Our main result will be focusing on the 20 percent level, which means: “I and 20% other workers acquire a higher education than the other 80%”. Our result indicated that immigrants experienced a higher likelihood of being overeducated in comparison to natives. When we looked at the different birth regions did we found that individuals from the Central/South American countries were the ones who experienced the highest likelihood of being overeducated. Our result indicates that the further away your home country is from Sweden the higher is the probability of being overeducated, which goes hand in hand with the theories presented.

Escherichia coli MutS is a DNA binding repair protein (97 kDa, monomer) and its biological significance arises from its recognition of mismatches which occur as errors during DNA replication. Mismatches and mutagenic bases represent a fascinating and diverse range of shapes and sizes and it is not obvious how a single protein (MutS) can recognise such molecular diversity against a huge background of canonical Watson-Crick base pairs. In this project, the structure of a 17mer mismatch GT DNA was carried out using NMR spectroscopy to identify the differences caused by the introduction of a non-canonical base pair on helical structure. The resulting structure was B-form in conformation and local helical distortions were observed about the GT mispair due primarily to its sheared orientation. The effect of mismatch orientation, sequence context and oligonucleotide length on mismatch stability was also investigated using UV absorbance melting and NMR spectroscopy. The results showed that substitution of a TG mispair for a GT mispair was accompanied by a small drop in melting temperature. It was also discovered that sequences in which purine-purine or pyrimidine-pyrimidine stacking occurred induced additional stability of the mismatch resulting in a higher melting temperature of the duplex.Affinity of mismatch GT DNA and its mismatch orientation, sequence context and length analogues for MutS was investigated by monitoring changes to the chemical shifts and linewidths of imino protons resonances during NMR titration. The results showed that MutS displayed higher affinity towards sequences which involved better stacking between the flanking base pairs and the GT/TG mispair.Analogous NMR structural investigations of 6-thioguanine modified 13mer GC DNA and its oxidised derivatives have been successfully carried out. The NMR structure was successfully determined of the former and the results obtained showed the effect on helical structure induced by the substitution of a different DNA lesion.Although the crystal structures of MutS bound to DNA mismatches have been known for a number of years, the analogous crystal structures of uncomplexed apo MutS have not been determined to date. Consequently, vital structural knowledge on the large change in conformation of MutS upon binding to the DNA mismatch is seriously lacking. We have successfully isolated the structurally and functionally important NTD of E. coli MutS and its labelled (13C, 15N) analogues and have shown that it is endowed with a stable, tertiary structural fold and well suited to NMR structure determination. This is exemplified by the assignments of several backbone amide and side chain resonances using isotope aided 3D NMR techniques.

Although climate change is a global phenomenon, the Arctic is warming faster than any other region on earth. These climatic changes have driven rapid regional changes over the past half-century in both the physical landscape and the ecosystems therein. One such ecological interaction is between migratory shorebird survival and local insect emergence. Annually, tens of millions of migratory shorebirds travel to the Arctic to rear their young in the relative absence of predators, but in a relative abundance of food (insects). Over evolutionary time, these trophic levels have coupled: shorebird chicks tend to hatch during the period of highest terrestrial insect availability. However, climate change is currently uncoupling this food-web synchrony, creating potential for trophic mismatch. In the High Arctic near Utqiaġvik (formerly Barrow), Alaska, trophic mismatch between nesting shorebirds and their insect food base is already detectable. In this ecosystem, flies in the Family Chironomidae (non-biting midges) dominate the prey trophic level in the avian food web. We have found that the pre-emergence development of one particular midge, Trichotanypus alaskensis, defies conventional wisdom of the Family, as this species molts to an additional fifth larval instar prior to pupation and emergence (all other chironomids are known to have four larval instars). We discovered an Utqiaġvik midge that reproduces asexually, a species that was not documented in the 1970s. Utilizing controlled temperature rearings of Utqiaġvik midge larvae, we discovered that as temperatures rise, emerging chironomid adults are generally smaller in size. We have found that chironomid pre-emergence developmental rates follow a positive exponential relationship as temperatures increase, can vary by taxon, yet are consistent across field and lab settings for a given taxon. At Utqiaġvik in the 2010s, chironomid emergence occurs 8-12 days earlier than it did in the 1970s. These findings shape our understanding of trophic mismatch in this arctic food web. / Arctic Landscape Conservation Cooperative; NDSU Graduate School Dissertation Fellowship; U.S. National Fish and Wildlife Foundation; Environmental and Conservation Sciences Program; Department of Biological Sciences

No description available.

DNA encodes the genetic information of the cell, therefore, every single living organism has a precise DNA damage response mechanism to safeguard DNA integrity. Base mismatches are endogenous DNA lesions introduced by the replicative polymerase during DNA replication. The conserved DNA mismatch repair pathway corrects these base mismatches. Mismatch repair initiation is orchestrated by two proteins, MutS and MutL. MutS recognizes and binds to base mismatches and relays the presence of the lesion to MutL. MutL, in turn, interacts with downstream factors to coordinate mismatch excision. The processivity clamp, typically known for its role in tethering the DNA polymerase to DNA during replication, is also involved in several steps of this repair process including MutL endonuclease activation and strand resynthesis. The dynamics of the MutS-MutL and MutL-processivity clamp interactions present one of the bottlenecks to uncovering the spatial and time organization of these protein assemblies. Therefore, little is known about the interactions that orchestrate the early steps of mismatch repair. The biochemical and structural work included in this thesis outlines a precise series of molecular cues that activate MutL. / Thesis / Doctor of Philosophy (PhD)