3 resultados para Cer
em Doria (National Library of Finland DSpace Services) - National Library of Finland, Finland
Resumo:
Systems biology is a new, emerging and rapidly developing, multidisciplinary research field that aims to study biochemical and biological systems from a holistic perspective, with the goal of providing a comprehensive, system- level understanding of cellular behaviour. In this way, it addresses one of the greatest challenges faced by contemporary biology, which is to compre- hend the function of complex biological systems. Systems biology combines various methods that originate from scientific disciplines such as molecu- lar biology, chemistry, engineering sciences, mathematics, computer science and systems theory. Systems biology, unlike “traditional” biology, focuses on high-level concepts such as: network, component, robustness, efficiency, control, regulation, hierarchical design, synchronization, concurrency, and many others. The very terminology of systems biology is “foreign” to “tra- ditional” biology, marks its drastic shift in the research paradigm and it indicates close linkage of systems biology to computer science. One of the basic tools utilized in systems biology is the mathematical modelling of life processes tightly linked to experimental practice. The stud- ies contained in this thesis revolve around a number of challenges commonly encountered in the computational modelling in systems biology. The re- search comprises of the development and application of a broad range of methods originating in the fields of computer science and mathematics for construction and analysis of computational models in systems biology. In particular, the performed research is setup in the context of two biolog- ical phenomena chosen as modelling case studies: 1) the eukaryotic heat shock response and 2) the in vitro self-assembly of intermediate filaments, one of the main constituents of the cytoskeleton. The range of presented approaches spans from heuristic, through numerical and statistical to ana- lytical methods applied in the effort to formally describe and analyse the two biological processes. We notice however, that although applied to cer- tain case studies, the presented methods are not limited to them and can be utilized in the analysis of other biological mechanisms as well as com- plex systems in general. The full range of developed and applied modelling techniques as well as model analysis methodologies constitutes a rich mod- elling framework. Moreover, the presentation of the developed methods, their application to the two case studies and the discussions concerning their potentials and limitations point to the difficulties and challenges one encounters in computational modelling of biological systems. The problems of model identifiability, model comparison, model refinement, model inte- gration and extension, choice of the proper modelling framework and level of abstraction, or the choice of the proper scope of the model run through this thesis.
Resumo:
My research deals with agent nouns in the language of the works of Mikael Agricola (ca. 1510–1557). The main tasks addressed in my thesis have been to describe individual agent noun types, to provide a comprehensive picture of the category of agent nouns and to clarify the relations between different types of agent nouns. My research material consists of all the agent nouns referring to persons in the language of Agricola’s works, together with their context. The language studied is for the most part translated language. Agent nouns play an important role both in the vocabulary of natural language and in broader sentence structures, since in a text it is constantly necessary to refer to actors re-ferring to persons in the text. As a concept and a phenomenon, the agent noun is widely known in languages. It is a word formed with a certain derivational affixes, which typical-ly refers to a person. In my research the agent noun category includes both deverbal and denominal derivatives referring to persons, e.g. kirjoittaa > kirjoittaja (to write > writer), asua > asuva (to inhabit > inhabitant), imeä > imeväinen (to suck > suckling), juopua > juopunut (to drink > drunkard), pelätä > pelkuri (to fear > one who fears ‘a coward’), apu > apulainen (help/to help > helper); lammas > lampuri (sheep > shepherd). Besides original Finnish expressions, agent noun derivatives taken as such from foreign languages form a word group of central importance for the research (e.g. nikkari, porvari, ryöväri, based on the German/Swedish for carpenter, burgher, robber). Especially important for the formation of agent nouns in Finnish are the models offered by foreign languages. The starting point for my work is predominantly semantic, as both the criteria for collecting the material and the categorisation underlying the analysis of the material are based on semantic criteria. When examining derivatives, aspects relating to structure are also inevitably of central importance, as form and meaning are closely associated with each other in this type of vocabulary. The alliance of structure and meaning can be described in an illustrative manner with the help of structural schemata. The examination of agent nouns comprises on the one hand analysis of syntactic elements and on the other, study of cultural words in their most typical form. The latter aspect offers a research object in which language and the extralinguistic world, referents, their designations and cultural-historical reality are in concrete terms one and the same. Thus both the agent noun types that follow the word formation principles of the Finn-ish language and those of foreign origin borrowed as a whole into Finnish illustrate very well how an expression of a certain origin and formed according to a certain structural model is inseparably bound up with the background of its referent and in general with semantic factors. This becomes evident both on the level of the connection between cer-tain linguistic features and text genre and in relation to cultural words referring to per-sons. For example, the model for the designations of God based on agent nouns goes back thousands of years and is still closely linked in 16th century literature with certain text genres. This brings out the link between the linguistic feature and the genre in a very con-crete manner. A good example of the connection between language and the extralinguistic world is provided by the cultural vocabulary referring to persons. Originally Finnish agent noun derivatives are associated with an agrarian society, while the vocabulary relat-ing to mediaeval urbanisation, the Hansa trade and specialisation by trade or profession is borrowed and originates in its entirety from vocabulary that was originally German.
Resumo:
Cholesterol (Chol) is an important lipid in cellular membranes functioning both as a membrane fluidity regulator, permeability regulator and co-factor for some membrane proteins, e.g. G-protein coupled receptors. It also participates in the formation of signaling platforms and gives the membrane more mechanical strenght to prevent osmotic lysis of the cell. The sterol structure is very conserved and already minor structural modifications can completely abolish its membrane functions. The right interaction with adjacent lipids and the preference of certain lipid structures over others are also key factors in determining the membrane properties of cholesterol. Because of the many important properties of cholesterol it is of value to understand the forces and structural properties that govern the membrane behavior of this sterol. In this thesis we have used established fluorescence spectroscopy methods to study the membrane behavior of both cholesterol and some of its 3β-modified analogs. Using several fluorescent probes we have established how the acyl chain order of the two main lipid species, sphingomyelin (SM) and phosphatidylcholine (PC) affect sterol partitioning as well as characterized the membrane properties of 3β-aminocholesterol and cholesteryl phosphocholine. We concluded that cholesterol prefers SM over PC at equal acyl chain order, indicating that other structural properties besides the acyl chain order are important for sphingomyelin-sterol interactions. A positive charge at the 3β position only caused minor changes in the sterol membrane behavior compared to cholesterol. A large phosphocholine head group caused a disruption in membrane packing together with other membrane lipids with large head groups, but was also able to form stable fluid bilayers together with ceramide and cholesterol. The Ability of the large head group sterol to form bilayers together with ceramide was further explored in the last paper where cholesteryl phosphocholine/ceramide (Chol-PC/Cer) complexes were successfully used to transfer ceramide into cultured cells.