Made available in DSpace on 2015-06-17T19:33:55Z (GMT). No. of bitstreams: 0 Previous issue date: 2014-09-10. Added 1 bitstream(s) on 2015-06-18T12:47:50Z : No. of bitstreams: 1 000828991.pdf: 1650989 bytes, checksum: 4e399312a262297cd8127550caef31c4 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Este estudo avaliou o efeito do trimetafosfato de sódio (TMP) e hexametafosfato de sódio (HMP) associados ou não ao fluoreto (F) na dissolução e estrutura da hidroxiapatita (HA). Para tanto, o estudo foi dividido em três subprojetos. Nos subprojetos 1 e 2, o pó de HA sintética (n=6) foi tratado com soluções contendo entre 0 e 10% de TMP associado a 0, 100, 250, 500 (Subprojeto 1) e a 0, 1100, 4500 e 9000 ppm F (Subprojeto 2), sendo submetido a um ciclo de pH. As concentrações de F alcáli- e ácido solúvel, cálcio (Ca) e fósforo (P) foram determinadas na HA, e as de P e F no sobrenadante. As amostras foram analisadas pela espectroscopia no infravermelho (FTIR), difração de Raios-X (DRX) e espectroscopia de energia dispersiva (EDX). No Subprojeto 3, discos de HA foram empregados para avaliar a taxa de dissolução da mesma utilizando o sistema pHstat. Estes foram tratados com soluções contendo 1100 ppm F, 1 e 8% de HMP ou TMP e 1100 ppm F associado com 1 e 8% de HMP ou TMP, totalizando 9 grupos (n=8). A influência da película salivar também foi avaliada. Discos de HA foram mantidos em saliva humana previamente ao tratamento com água deionizada e 1100 ppm F associado com 1 e 8% de HMP ou TMP, totalizando 5 grupos (n=8). A taxa de dissolução pós-tratamento foi determinada a partir de 3 medidas consecutivas a cada 30 min. Os dados foram submetidos a ANOVA, teste de Student-Newman-Keul's e coeficiente de correlação de Pearson (Subprojetos 1 e 2) e a ANOVA e testes de Fisher e Holm-Sidak (Subprojeto 3) (α=0,05). Valores de proporção Ca/P maiores foram observados para as soluções fluoretadas quando comparados à solução sem F e TMP, sendo os mesmos dependentes da proporção F:TMP (p<0,05). A deposição do F álcali-solúvel foi diretamente relacionada com as concentrações de TMP nas soluções... / This study evaluated the effect of sodium trimetaphosphate (TMP) and sodium hexametaphosphate (HMP) associated or no with fluoride (F) on the structure and dissolution of hydroxyapatite (HA). For this purpose, the study was divided into three subprojects. In Subprojects 1 and 2, synthetic HA powder (n=6) was treated with solutions containing TMP varying at 0-10% associated with 0, 100, 250, 500 (Subproject 1) and 0, 1100, 4500 and 9000 ppm F (Subproject 2) and submitted to a pH cycle. Afterwards, alkali- and acid soluble F, Ca and P were determined in/on HA, and P and F in the supernatants. Samples were analyzed by infrared spectroscopy (FTIR), X-ray diffraction (XDR) and energy-dispersive X-ray spectroscopy (EDX). In Subproject 3, HA discs were used to assess the dissolution rate of HA using a pHstat system. HA discs were treated with 1100 ppm F, 1% and 8% of HMP or TMP and 1100 ppm F associated with 1% and 8% of HMP or TMP, totaling 9 groups (n=8). The influence of a salivary pellicle on HA dissolution was also assessed. HA discs were kept in pooled human saliva before treatment with deionised water and 1100 ppm F associated with 1% and 8% of HMP or TMP, totaling 5 groups (n=8). The post-treatment dissolution rate was determined from three consecutive 30-min assays. Data were submitted to ANOVA, Student-Newman-Keuls' test and Pearson's correlation coefficient (Subprojects 1 and 2), and to ANOVA and Fisher and Holm- Sidak methods (Subproject 3) (α=0.05). Ca/P ratios values were higher for the fluoride solutions when compared with the no F and TMP groups and dependent of the F:TMP ratio used (p<0.05). The overall trend was that alkali-soluble F deposition was directly related to TMP concentrations in the treatment solutions, while acidsoluble incorporation was inversely related to TMP... / FAPESP: 11/17234-9

Orientador: Alberto Carlos Botazzo Delbem / Coorientador: Juliano Pelim Pessan / Banca: Robson Frederico Cunha / Banca: Douglas Roberto Monteiro / Banca: Marília Afonso Rabelo Buzalaf / Banca: João Carlos Silos Moraes / Resumo: Este estudo avaliou o efeito do trimetafosfato de sódio (TMP) e hexametafosfato de sódio (HMP) associados ou não ao fluoreto (F) na dissolução e estrutura da hidroxiapatita (HA). Para tanto, o estudo foi dividido em três subprojetos. Nos subprojetos 1 e 2, o pó de HA sintética (n=6) foi tratado com soluções contendo entre 0 e 10% de TMP associado a 0, 100, 250, 500 (Subprojeto 1) e a 0, 1100, 4500 e 9000 ppm F (Subprojeto 2), sendo submetido a um ciclo de pH. As concentrações de F alcáli- e ácido solúvel, cálcio (Ca) e fósforo (P) foram determinadas na HA, e as de P e F no sobrenadante. As amostras foram analisadas pela espectroscopia no infravermelho (FTIR), difração de Raios-X (DRX) e espectroscopia de energia dispersiva (EDX). No Subprojeto 3, discos de HA foram empregados para avaliar a taxa de dissolução da mesma utilizando o sistema pHstat. Estes foram tratados com soluções contendo 1100 ppm F, 1 e 8% de HMP ou TMP e 1100 ppm F associado com 1 e 8% de HMP ou TMP, totalizando 9 grupos (n=8). A influência da película salivar também foi avaliada. Discos de HA foram mantidos em saliva humana previamente ao tratamento com água deionizada e 1100 ppm F associado com 1 e 8% de HMP ou TMP, totalizando 5 grupos (n=8). A taxa de dissolução pós-tratamento foi determinada a partir de 3 medidas consecutivas a cada 30 min. Os dados foram submetidos a ANOVA, teste de Student-Newman-Keul's e coeficiente de correlação de Pearson (Subprojetos 1 e 2) e a ANOVA e testes de Fisher e Holm-Sidak (Subprojeto 3) (α=0,05). Valores de proporção Ca/P maiores foram observados para as soluções fluoretadas quando comparados à solução sem F e TMP, sendo os mesmos dependentes da proporção F:TMP (p<0,05). A deposição do F álcali-solúvel foi diretamente relacionada com as concentrações de TMP nas soluções... / Abstract: This study evaluated the effect of sodium trimetaphosphate (TMP) and sodium hexametaphosphate (HMP) associated or no with fluoride (F) on the structure and dissolution of hydroxyapatite (HA). For this purpose, the study was divided into three subprojects. In Subprojects 1 and 2, synthetic HA powder (n=6) was treated with solutions containing TMP varying at 0-10% associated with 0, 100, 250, 500 (Subproject 1) and 0, 1100, 4500 and 9000 ppm F (Subproject 2) and submitted to a pH cycle. Afterwards, alkali- and acid soluble F, Ca and P were determined in/on HA, and P and F in the supernatants. Samples were analyzed by infrared spectroscopy (FTIR), X-ray diffraction (XDR) and energy-dispersive X-ray spectroscopy (EDX). In Subproject 3, HA discs were used to assess the dissolution rate of HA using a pHstat system. HA discs were treated with 1100 ppm F, 1% and 8% of HMP or TMP and 1100 ppm F associated with 1% and 8% of HMP or TMP, totaling 9 groups (n=8). The influence of a salivary pellicle on HA dissolution was also assessed. HA discs were kept in pooled human saliva before treatment with deionised water and 1100 ppm F associated with 1% and 8% of HMP or TMP, totaling 5 groups (n=8). The post-treatment dissolution rate was determined from three consecutive 30-min assays. Data were submitted to ANOVA, Student-Newman-Keuls' test and Pearson's correlation coefficient (Subprojects 1 and 2), and to ANOVA and Fisher and Holm- Sidak methods (Subproject 3) (α=0.05). Ca/P ratios values were higher for the fluoride solutions when compared with the no F and TMP groups and dependent of the F:TMP ratio used (p<0.05). The overall trend was that alkali-soluble F deposition was directly related to TMP concentrations in the treatment solutions, while acidsoluble incorporation was inversely related to TMP... / Doutor

published_or_final_version / Biochemistry / Doctoral / Doctor of Philosophy

No description available.

Irradiation sterilization of precooked, hermetically sealed meat provides a shelf-stable, ready-to-eat product that can be stored for long periods of time without refrigeration. The Atomic Energy Corporation of South Africa started to develop precooked, shelf-stable meat products during the late 1970’s, using gamma radiation from a 60Co source at dose levels of at least 45 kGy. A number of meat dishes were successfully developed though problems were experienced with the texture of dry-packed roast beef slices, as these were found to be slightly dry. Polyphosphates can possibly be used to alleviate the textural problems found in precooked irradiation-sterilized meat because polyphosphates are known to increase the water binding properties of meat proteins, resulting in a juicy, tender product. The choice of cattle breed used for the preparation of precooked meat dishes may also affect cooked meat texture, due to genotypic differences in the amount and especially the solubility of collagen. Biceps femoris and semitendinosus muscles obtained from Afrikaner (Bos Indicus), Hereford (Bos Taurus) and Simmental (Bos Taurus) steers were treated with low levels of sodium tripolyphosphate (0.3% and 0.5%) and tetrasodium pyrophosphate (0.22% and 0.36%) in combination with 0.7% salt. The precooked meat was vacuum packed in flexible pouches and irradiated in the frozen state (-40°C) with a 60Co gamma source until a minimum target dose of 45 kGy was reached. Various physico-chemical tests as well as descriptive generic sensory evaluation were performed on the samples to determine the effect of breed, polyphosphate treatment and irradiation on the physico-chemical and sensory properties of irradiated precooked beef. Cattle breed affected the texture of precooked, irradiated, shelf-stable beef, with Afrikaner biceps femoris giving a more tender, juicy product than that of Hereford and Simmental. The low levels of polyphosphates used in combination with salt successfully increased the juiciness and tenderness of precooked, shelf-stable beef. There was little difference in the physico-chemical and sensory results obtained from samples treated with the two different polyphosphates, or the level at which the polyphosphates were administered. Irradiation sterilization of precooked beef resulted in a tender product. Comparison of irradiated and non-irradiated samples revealed that the irradiated samples had longer sarcomere and I-band lengths, and shorter A-band lengths, which explained the increased tenderness in irradiated samples. An increase in both soluble collagen and % collagen solubility after irradiation sterilization further substantiated the tenderness results. Treatment of the biceps femoris with low levels of sodium tripolyphosphate or tetrasodium pyrophosphate in combination with salt, prior to cooking and irradiation, resulted in a juicy, shelf-stable product. Irradiation sterilization did, however, produce a detectable wet dog flavour and aroma, and more research is required into improving the flavour and aroma of irradiation sterilized beef. Although this research indicated that irradiation of cooked, polyphosphate treated Afrikaner meat resulted in the most tender and juicy end-products, it is recommended that sensory evaluation using a consumer panel also be conducted, in order to determine if this level of tenderness is acceptable, or if it is over tender due to excessive degradation of the connective tissue. / Dissertation (MSc)--University of Pretoria, 2005. / Food Science / unrestricted

Suite aux restrictions réalisées par les Nations Unies et la Communauté Européenne concernant certains retardateurs de flammes halogénés, la demande actuelle du marché tend à se diriger vers des composés non halogénés, tels que les retardateurs de flammes phosphorés. Il est cependant nécessaire d’utiliser des taux de charges élevés pour obtenir des propriétés de résistance au feu intéressantes, ce qui entraîne une chute des propriétés mécaniques. Cela nous a amené à combiner une partie des composés phosphorés par des oxydes métalliques nanométriques, connus pour leur capacité à améliorer la stabilité du poly(méthacrylate de méthyle) (PMMA).Nous avons, dans un premier temps, étudié l’effet des nanoparticules (dioxyde de titane, alumine et boehmite) sur la diffusivité thermique du PMMA, permettant de mettre en évidence un mode d’action de ces additifs lors de la dégradation thermique du PMMA. Une partie de ces charges ont été, dans un deuxième temps, substituées par deux retardateurs de flammes phosphorés et azotés : le polyphosphate d’ammonium (APP) et le polyphosphate de mélamine (MPP). Dans les systèmes ternaires obtenus (APP/MPP/oxyde métallique), les propriétés de résistance au feu et de stabilité thermique ont été étudiées, ainsi que les mécanismes mis en jeu lors de la combustion. Les phases condensée et gazeuse ont été analysées à cet effet / Following the restrictions made by the United Nations and the European Community on certain halogenated flame-retardants, the current market demand tends to move towards non-halogenated compounds such as phosphorous flame-retardants. However, it is necessary to use high amounts of material for reaching interesting fire resistance properties, resulting in a drop of mechanical properties. This led us to combine a part of the phosphorous compounds with nanoscale metal oxides, known for their ability to improve the stability of poly (methyl methacrylate) (PMMA).We have first studied the effect of nanoparticles (titanium dioxide, alumina and boehmite) on the thermal diffusivity of PMMA, in order to highlight a mode of action of these additives during the thermal degradation of PMMA. A part of these metal oxides have then been substituted by two flame-retardants based on phosphorus and nitrogen: ammonium polyphosphate (APP) and melamine polyphosphate (MPP). In the obtained ternary systems (APP/MPP/metal oxide), the properties of fire resistance and thermal stability were studied and also the mechanisms involved in the degradation. Gaseous and condensed phases have been analyzed for this purpose

No description available.

The endogenous respiration rate and the intracellular ATP/ADP ratio were determined during synchronous growth of a high temperature strain of Chlorella pyrenoidosa in order to correlate their activities with a proposed mechanism for the control of intracellular levels of inorganic acid-insoluble polyphosphate, (Pi)x, during cellular growth and division. / Master of Science

Normal mRNA turnover is essential for genetic regulation within cells. The E. coli RNA degradosome, a large multi-component protein complex which originates through specific protein interactions, has been referred to as the “RNA decay machine” and is responsible for mRNA turnover. The degradosome functions to process RNA and its key components have been identified. The scaffold protein is RNase E and it tethers the degradosome to the cytoplasmic membrane. Polynucleotide phosphorylase (PNPase), ATP-dependent RNA helicase (RhlB helicase) and the glycolytic enzyme enolase associate with RNase E to form the degradosome. Polyphosphate kinase associates with the degradosome in substoichiometric amounts, as do the molecular chaperones DnaK and GroEL. The role of DnaK as well as that of enolase in the RNA degradosome is unknown. Very limited research has been conducted on the components of the RNA degradosome under conditions of stress. The aim of this study was to understand the role played by enolase in the assembly of the degradosome under conditions of stress, as well as investigating the protein levels of molecular chaperones under these conditions. The RNA degradosome was successfully purified through its scaffold protein using nickel-affinity chromatography. In vivo studies were performed to investigate the protein levels of DnaK and GroEL present in the degradosome under conditions of heat stress, and whether GroEL could functionally replace DnaK in the degradosome. To investigate the recruitment of enolase to the degradosome under heat stress, a subcellular fractionation was performed to determine the localization of enolase upon heat shock in vivo. The elevated temperature resulted in an increased concentration of enolase in the membrane fraction. To determine whether there is an interaction between enolase and DnaK, enolase activity assays were conducted in vitro. The effect of DnaK on enolase activity was measured upon quantifying DnaK and adding it to the enolase assays. For the first time it was observed that the activity of enolase increased with the addition of substoichiometric amounts of DnaK. This indicates that DnaK may be interacting with the RNA degradosome via enolase.

The present thesis presents new renewable, antimicrobial and biodegradable superabsorbent polymers (SAPs), produced from the cell wall of zygomycetes fungi. The cell wall was characterized and chitosan, being one of the most important ingredients, was extracted, purified, and converted to SAP for use in disposable personal care products designed for absorption of different body fluids. The cell wall of zygomycetes fungi was characterized by subsequent hydrolysis with sulfuric and nitrous acids and analyses of the products. The main ingredients of the cell wall were found to be polyphosphates (4-20%) and copolymers of glucosamine and N-acetyl glucosamine, i.e. chitin and chitosan (45-85%). The proportion of each of these components was significantly affected by the fungal strain and also the cultivation conditions. Moreover, dual functions of dilute sulfuric acid in relation to chitosan, i.e. dissolution at high temperatures and precipitation at lowered temperatures, were discovered and thus used as a basis for development of a new method for extraction and purification of the fungal chitosan. Treatment of the cell wall with dilute sulfuric acid at room temperature resulted in considerable dissolution of the cell wall polyphosphates, while chitosan and chitin remained intact in the cell wall residue. Further treatment of this cell wall residue, with fresh acid at 120°C, resulted in dissolution of chitosan and its separation from the remaining chitin/chitosan of the cell wall skeleton which was not soluble in hot acid. Finally, the purified fungal chitosan (0.34 g/g cell wall) was recovered by precipitation at lowered temperatures and pH 8-10. The purity and the yield of fungal chitosan in the new method were significantly higher than that were obtained in the traditional acetic acid extraction method. As a reference to pure chitosan, SAP from shellfish chitosan, was produced by conversion of this biopolymer into water soluble carboxymethyl chitosan (CMCS), gelation of CMCS with glutaraldehyde in aqueous solutions (1-2%), and drying the resultant gel. Effects of carboxymethylation, gelation and drying conditions on the water binding capacity (WBC) of the final products, were investigated. Finally, choosing the best condition, a biological superabsorbent was produced from zygomycetes chitosan. The CMCS-based SAPs were able to absorb up to 200 g water/g SAP. The WBC of the best SAP in urine and saline solutions was 40 and 32 g/g respectively, which is comparable to the WBC of commercially acceptable SAPs under identical conditions (34-57 and 30-37 g/g respectively). / <p>Disputationen sker fredagen den 1 oktober kl. 10.00 i KA-salen, Kemigården 4, Chalmers, Göteborg</p>