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Baigiamajame magistro darbe nagrinėjama spaustuvės UAB „BALTO“ lankstymo kokybė. Aprašoma kokybės samprata, popieriaus lankstymo procesas, kombinuotų lankstymo mašinų parametrai, naudotų popierių techninės charakteristikos. Darbe pagal popieriaus rūšį ir gramatūrą yra nustatomi lankstymo broko procentai, tiriamos atsiradusio broko priklausomybės nuo popieriaus gramatūros, charakteristikų ir kitų faktorių. Gauti rezultatai pateikiami histogramomis, kurios analizuojamos pasitelkiant statistinius metodus. Remiantis gautais rezultatais buvo nustatyta UAB „BALTO“ spaustuvės lankstymo kokybė ir priežastys, lemiančios lankstymo broko atsiradimą. / In the master thesis is investigated the folding quality in the printing house “BALTO”. The concept of quality, paper folding process, combined folding machine parameters and printing papers are described. In the master thesis is determined the percent of folding defects, are investigated the spoilage dependence of paper characteristics and other factors. Results are presented as histograms and analyzed using statistical methods. Based on the results obtained were found folding quality of printing house “BALTO” and reasons that determined folding defects.

Submitted in fulfillment of the requirements of the Degree of Master of Technology: Chemistry, Durban University of Technology. 2014. / Peptide folding is a very complicated and dynamic process taking place in all living systems. The understanding of a bioactive conformation of the peptides is very important to understand their biological functions and underlying mechanism of action. However, the high flexible nature of peptides makes this process difficult as they can adopt thousands of conformations within the fraction of a second. The usage of experimental techniques in the characterization process is also limited due to several associated complications including synthesis, isolation and crystallization of peptides. The present computational methodologies, on the other hand, are solid enough to provide detailed complementary information about the intrinsic conformational features of peptides by mimicking their physiological conditions. In the present work, molecular dynamics (MD) computational method was used to explore the configurational space of three Aurein peptides, namely Aurein 2.3, Aurein 2.4 and Aurein 2.5. These peptides are secreted by the amphibian skin when they are exposed to external stimuli. These peptides have been reported to possess anti-cancer and anti-bacterial activity with minimum resistance compared to the available drugs. However, despite their medicinal significance, the precise three dimensional structures of Aurein 2.4 and Aurein 2.5 are not as yet known. First, a validation study was performed on Aurein 2.3 to check the efficiency of the computational protocol. The results obtained revealed the presence of -helicity in all residues of the Aurein 2.3, in accordance with its experimental structure. A similar protocol was further used to explore the conformational profiles of the remaining two peptides (Aurein 2.4 and Aurein 2.5) under implicit and explicit solvent conditions. The results obtained revealed that both these peptides exhibit -helical character in all residues although in varying percentages. The -helical region in the case of Aurein 2.4 was localized predominantly in the central residues extending towards its N-terminal residues, whereas it was flanked by N-terminal and the central residues in Aurein 2.5. However, -helicity was completely absent in the explicit solvents, and the peptides preferred to stay either in -turns or extended forms. Hence, the present work provides comprehensive information about the conformational preferences of Aurein peptides which could lead to a better understanding of their native conformations for future investigations and point the way towards developing their new agonists.

In mammalian cells newly synthesised proteins are translocated across the ER membrane and their subsequent folding is facilitated by an array of folding factors present in the lumen. These include the lectins calreticulin and calnexin, which form complexes with ERp57 to generate glycoprotein specific molecular chaperones. ERp57 is a member of the protein disulphide isomerase (PDI) family and its binding to ER lectins can be reconstituted in vitro. I have exploited this approach to define the regions of ERp57 that are necessary and sufficient for its specific interaction with calreticulin and calnexin. Truncated forms of ERp57, chimeric proteins containing various domains of ERp57 and PDI (which does not interact with calreticulin) and ERp57 b' domain point mutants have been constructed. By analysing the interactions of ERp57 derivatives with calreticulin using both cross-linking and binding assays I have been able to provide detailed insights into the molecular basis for the specific assembly of these components within the ER lumen. My results indicate that the b and b' domains of ERp57 are necessary, but not sufficient for binding to both calreticulin and calnexin. The more stringent binding assay revealed that the a' domain of ERp57 significantly enhanced binding to biotin-tagged calreticulin. The ERp57 C-terminal extension also increased binding to biotin-tagged calreticulin, perhaps by playing a role in the overall stability of the ERp57. In addition, the ERp57 b' domain point mutants show that certain amino acids in this domain, in particular residues F280, V283 and F299, may be crucial for binding to calreticulin, consistent with the principal lectin-binding site being located in the b' domain. However, the binding region clearly extends into other domains, in particular the b and a' domains.

published_or_final_version / Biochemistry / Doctoral / Doctor of Philosophy

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