Health benefits of high molecular weight (MW) β-glucans are well documented. Therefore, understanding and controlling depolymerization of β-glucan in baked products, would increase the effectiveness of β-glucan to confer health benefits. In this study we demonstrated that endogenous β-glucanase in wheat kernels are responsible for the depolymerization of β-glucans. A protocol was developed based on the Megzayme procedure to detect low levels of β-glucanase activity in wheat flour. This was confirmed by using HPLC-Calcofluor detection to monitor molecular weight changes. The distribution of β-glucanase in wheat kernels was also investigated. The effect of genotype, location, planting season and environmental factors on the level of endogenous β-glucanase in selected wheat cultivars was investigated using different wheat varieties planted under different condition and different seasons. Furthermore, kinetics of β-glucan depolymerization by endogenous glucanase in two dough systems with different moisture content was investigated. The results demonstrated that enzymes with β-glucanase activity are concentrated primarily in the outer layer of wheat kernels. Also genotype, environmental conditions and agronomic practice all had significant effects on the β-glucanase activity in wheat flours and poor harvesting conditions can significantly increase β-glucanase activity level in wheat. The kinetics results demonstrated that moisture content, incubation time and levels of endogenous β-glucanase activity of the system had significant impact on the final MW of β-glucan in the dough. Among all factors investigated, moisture content had the greatest impact. This study presents opportunities for industry to fortify baked products with high molecular weight β-glucan. / Ontario Ministry of Agricultural Food and Rural Affairs

A solid-state DE-E telescope beta spectrometer has been built and used to study beta-minus spectra. The system consists of a 15 mm x 500 mm$ sp2$ hyperpure germanium (HPGe) E-detector and a 300 $ mu$m x 200 mm$ sp2$ Si DE-detector with a special "keyhole" design. / The response function of the system has been determined experimentally using mono-energetic electron beams with incident energies ranging from 1 to 12 MeV. / The beta endpoint energies of 25 nuclei, namely, $ sp{32}$P, $ sp{88}$Rb, $ sp{91-99}$Rb, $ sp{91-96}$Sr, $ sp{99-100}$Sr, $ sp{92-96}$Y and $ sp{100}$Y have been measured. The Q-beta values and mass excesses for A = 91-100 have been determined. The results for $ sp{99}$Rb, $ sp{99-100}$Sr and $ sp{100}$Y have been obtained for the first time. / The beta strength functions for odd mass Rb isotopes, namely $ sp{91-99}$Rb have been measured for the first time from direct beta spectroscopy with a solid-state telescope system. The experimental results have been compared to calculations using the Brown-Bolsterli (B-B) model.

An accurate response function for a superconducting solenoid beta spectrometer for electrons up to 5.5 MeV has been found using Monte Carlo calculations and measurements of standard spectra. Experimental conditions affecting the response function have been studied and corrections for source scattering and pileup devised. / An anomalous shift in the electron energy calibration caused by the magnetic field has been discovered and explained. / The beta spectrum of ('32)P, ('90)Y, ('28)Al, ('42)K, ('38)Cl and ('88)Rb have been studied. Systematic uncertainties in endpoint, branch intensity and shape factor measurements have been estimated. / A beta spectra analysis program has been written to calculate endpoints, branch intensities and shape factors in a multi-branch spectrum. / The beta spectra of ('141)La, ('142)La, ('139)Ba, ('141)Ba, ('142)Ba, ('138)Cs and ('139)Cs have been studied. Q(,(beta))-values, intensities for all branches and some shape factors have been measured. / The shape factor of the ('20)F beta spectrum has been measured. The value found for the linear coefficient, a = 0.006 (+OR-) .002 (mc('2))('-1), supports the "weak magnetism" predictions of the Conserved Vector Current theory.

Submitted by Ramon Santana (ramon.souza@ufpe.br) on 2015-03-11T19:15:47Z No. of bitstreams: 2 TESE Dyana Leal Veras.pdf: 6559035 bytes, checksum: 43988c4ed7fb791a6e593067fb17b1eb (MD5) license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) / Made available in DSpace on 2015-03-11T19:15:47Z (GMT). No. of bitstreams: 2 TESE Dyana Leal Veras.pdf: 6559035 bytes, checksum: 43988c4ed7fb791a6e593067fb17b1eb (MD5) license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Previous issue date: 2014-02-24 / O objetivo deste trabalho foi determinar a ação in vitro de antibióticos β-lactâmicos em isolados de Klebsiella pneumoniae portadores dos genes blaKPC, blaSHV, blaTEM ou blaCTX-M, desenvolvendo embasamento teórico para futura proposição de novas combinações terapêuticas. Sete isolados de K. pneumoniae foram utilizados, sendo 3 clínicos, 2 de comunidade e 2 de microbiota. Os isolados clínicos e de comunidade são portadores de genes codificantes de ESBL ou KPC e os de microbiota de -lactamases clássicas. Os genes de resistência foram identificados por PCR e seqüenciados utilizando primers específicos. A primeira fase deste estudo identificou os efeitos ultra-estruturais causados por -lactâmicos in vitro nos isolados clínicos e de microbiota de K. pneumoniae. Os isolados clínicos foram submetidos a concentrações clinicamente relevantes de ceftazidima, cefotaxima, aztreonam e/ou imipenem e os isolados de microbiota a ampicilina e amoxicilina, para análise pela Microscopia Eletrônica de Transmissão (MET) e Varredura (MEV). Diferentes alterações morfológicas e ultra-estruturais foram identificadas, como filamentação celular, perda de material citoplasmático e deformação dos septos de divisão, após submissão aos antibióticos, tanto nos isolados clínicos de K. pneumoniae como nos obtidos de microbiota. A segunda fase deste estudo determinou a influência destes antibióticos na produção de cápsula polissacarídica (CPS) nos isolados clínicos e de comunidade de K. pneumoniae. Os isolados foram submetidos a concentrações clinicamente relevantes de cefotaxima, ceftazidima, aztreonam e/ou imipenem para analise pela MET, utilizando citoquímica de carboidratos. Todos os isolados tiveram confirmação da presença da região promotora do operon envolvido na produção de CPS, identificado através de PCR e sequenciamento. A ceftazidima e o aztreonam foram capazes de inibir a produção de CPS nos isolados de K. pneumoniae produtores de ESBLs mas não no isolado produtor de KPC, o qual teve sua síntese fortemente inibida apenas pelo imipenem. A cefotaxima não interferiu na produção de CPS em nenhum dos isolados analisados. Nossos resultados demonstraram que antibióticos -lactâmicos possuem ação residual in vitro nos isolados analisados, sugerindo que a produção de ESBL e KPC por isolados de K. pneumoniae não são capazes de evitar completamente a interação de antibióticos β-lactâmicos com as PBPs bacterianas. Podemos concluir ainda que a ceftazidima, o aztreonam e o imipenem, podem ser capazes de inibir a produção de CPS em isolados clínicos e de comunidade de K. pneumoniae, contribuindo para diminuir a expressão do fator de virulência mais importante desta espécie bacteriana.

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published_or_final_version / Biochemistry / Doctoral / Doctor of Philosophy

published_or_final_version / Physics / Master / Master of Science

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