Thesis (M.S.)--Mississippi State University. Department of Chemistry. / Title from title screen. Includes bibliographical references.

Thesis (Ph. D.)--Institute of Paper Chemistry, 1969. / Bibliography: leaves 89-91.

The permeability of lipid bilayer membranes to glucose and carboxyfluorescein has been studied in model membranes. Using an enzyme assay, the permeability of glucose was monitored spectrometrically with both large and giant unilamellar vesicles (LUVs and GUVs). The permeability of carboxyfluorescein was studied by entrapping the dye and monitoring its leakage over time from a single GUV. Permeability study using GUVs may provide new information that cannot be obtained from LUVs.The stability of lipid membranes was enhanced by incorporating polymer scaffold. LUVs were prepared with hydrophobic monomers partitioned and then polymerized inside the hydrophobic interior of the lipid bilayers. The sizes of the formed polymers were characterized using gel permeation chromatography and mass spectrometry. This study suggests that large molecular weight polymers were formed inside the lipid bilayers and that the stability of the membranes is related to the size of the polymers.

Killer yeasts secrete polypeptide toxins which kill sensitive cells of their own species and frequently those of other species and genera of yeasts. These protein compounds are designated as killer toxins. Also killer toxins of certain yeast strains have potential growth inhibitory activity on gram-positive pathogenic bacteria and plant pathogenic fungi. The yeasts are immune to their own killer protein. The killer phenomenon can be utilized for the protection of fermentation process against contaminating yeasts and for biological control of undesirable yeasts in the preservation of foods. The killer trait can also be used to produce large amount of foreign proteins in yeast. In the medical field , it is thought that their anti-microbial and anti-mycotic activity could be exploited in a therapeutic strategy. Yeast killer toxins are classified into 11 types according to their killing spectra and immunity-specificities such as K1, K2, etc. Altough there is considerable amount of published information concerning the applications of yeast killer toxins , among the 11 types , only K1 , K2 and K6 have been characterized. In this study , it was aimed to purify and characterize the K4 type yeast killer toxin secreted by the Hansenula anomala NCYC 432. Gel permeation chromatography was performed to isolate the killer toxin by using a HPLC system. The toxin was shown to be a glycoprotein having a molecular mass of between 49.08 kDa and 47.25 kDa and isoelectric point of between 3.77 and 3.41.

Thesis (Ph. D.)--Ohio University, March, 2001. / Title from PDF t.p.

Thesis (M.Sc. (Pharmacy)) - Rhodes University, 2008

Made available in DSpace on 2014-06-11T19:24:41Z (GMT). No. of bitstreams: 0 Previous issue date: 2004-11-09Bitstream added on 2014-06-13T19:31:32Z : No. of bitstreams: 1 silva_fi_me_botfca.pdf: 679722 bytes, checksum: 83065f5a372855f2ea5b618304dfefac (MD5) / Universidade Estadual Paulista (UNESP) / A fécula de mandioca (Manihot esculenta Crantz) contém aproximadamente 98 % de amido, em peso seco. Este amido é constituído por dois tipos de polissacarídeos: a amilose ( de 16 a 20 % ), com cadeias lineares de monômeros de glicose e peso molecular 1,5.105 a 1,0.106 Da; e amilopectina ( de 80 a 84 % ), com cadeias ramificadas e peso molecular 5,0.106 a 1,0.108 Da. A estrutura molecular desses polissacarídeos influi diretamente nas propriedades funcionais dos amidos, as quais são interessantes para diversos usos industriais. O principal objetivo desta pesquisa é avaliar e adaptar a técnica de separação de moléculas conhecida por cromatografia de permeação em gel, seguida da caracterização das frações coletadas na permeação e verificar as propriedades viscográficas do amido. Nesta principal técnica utilizada, conhecida também por cromatografia por exclusão de tamanho, as moléculas se separam de acordo com seus tamanhos e pesos moleculares. Sendo assim, moléculas maiores que os poros do gel, saem primeiro da coluna, enquanto moléculas de tamanhos intermediários aos dos poros do gel, saem no final da permeação. As amostras usadas neste trabalho foram féculas extraídas de sete etnovariedades de mandioca, que foram previamente tratadas e posteriormente solubilizadas em solventes adequados e injetadas na coluna de permeação contendo um gel de porosidade pré-determinada. Foi usado um sistema completo para permeação em gel, contendo colunas, géis, coletor automático das frações permeadas, bomba peristáltica, kit de proteínas e carboidrato padrão, dentre outros acessórios fornecidos pela Amersham Pharmacia Biotech. Empregou-se solventes P.A. e enzima pura (Sigma-Aldrich); equipamento analisador de carbono (TOC), marca Shimadzu e espectrofotômetro UV-visível com varredura de 190 a 1100 nm, marca Varian... / Cassava starch ( Manihot esculenta Crantz ) contains approximately 98 % of starch in dry weight. This starch is constituted of two polysaccharide: amylose ( 16 to 20% ), with lineal chains of glucose monomers and molecular weight 1,5.105 to 1,0.106 Da; and amylopectin ( 80 to 84% ), with ramified chains and molecular weight from 5,0.106 to 1,0.108 Da. The molecular structure of these polysaccharides influences directly the functional properties of the starches, which are interesting for several industrial uses. The main objective of this research is to evaluate and to adapt the technique of separation of molecules known by gel permeation chromatography, followed by the characterization of the fractions collected in the permeation and to verify the viscographic properties of the starch. In this main used technique, also known by size exclusion chromatography, the molecules are separated in agreement with sizes and molecular weights. So, molecules larger than the pores of the gel, leave the column first, while molecules of intermediary sizes come out in the end of the permeation. The samples used in this work were starches extracted from seven cassava ethnovarieties, that were previously treated and then dissolved in appropriate solvents and injected in the permeation column that was filled with a gel of defined porosity. A complete system for gel permeation was used, constituted of columns, gels, automatic collector, peristaltic pump, kit of proteins and standard carbohydrate, among other accessories supplied by Amersham Pharmacia Biotech. Solvents (for analysis) and pure enzyme (Sigma-Aldrich) were used; equipment to analyze organic carbon (TOC), from Shimadzu and UV-visible spectrophotometer with scanning from 190 to 1100 nm, from Varian were employed...

Orientador: Liliane Maria Ferrareso Lona / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química / Made available in DSpace on 2018-08-19T01:46:35Z (GMT). No. of bitstreams: 1 Malere_CarolinePaganuccidosReis_M.pdf: 1568071 bytes, checksum: 720e59aec25863d529bde7e649b7ece7 (MD5) Previous issue date: 2011 / Resumo: A Cromatografia de Permeação em Gel ou "Gel Permeation Chromatography (GPC), também conhecida como Cromatografia de Exclusão por Tamanho ou "Size Exclusion Chromatography" (SEC) é uma das técnicas analíticas mais utilizadas para separação e caracterização de polímeros naturais e sintéticos, copolímeros e proteínas, fornecendo informações distribuição de massa molar (MWD), viscosidade intrínseca (IV) e polidispersividade (PDI). A importância de sua resposta na análise de determinado polímero se reflete em termos de sua processabilidade, uma vez que as propriedades mecânicas e químicas são drasticamente afetadas por sua massa molar média, tamanho da cadeia e distribuição. Na técnica de GPC os padrões utilizados são de primordial importância para obtenção de resultados confiáveis, pois são utilizados nas construções de curvas de calibrações necessárias para aquisição dos resultados quanti e qualitativos na técnica. Apesar da vasta utilização da técnica de GPC no Brasil, tanto em centros de pesquisa como em indústrias químicas e petroquímicas, os padrões disponíveis para comercialização são todos adquiridos no exterior, por meio de importação a altos custos. Visto a necessidade de mudança desse paradigma, este trabalho tem como objetivo desenvolver um produto nacional utilizando a polimerização via radical livre mediada por radicais nitróxidos (NMRP), também chamada "living free radical polymerization (LFRP)". O padrão escolhido para o estudo foi o poliestireno (PS), por ser ele um dos padrões mais utilizados na calibração de análise de GPC orgânico. Um dos desafios enfrentados neste trabalho foi a obtenção de polímeros com índices de polidispersividade (PDI) variando de 1 a 1,10, distribuição de massa molar (MWD) estreita e alto grau de pureza, utilizando pela primeira vez uma mistura de iniciadores no processo NMRP. A NMRP é uma técnica robusta e inovadora comparada com a polimerização iônica que é atualmente o processo empregado para obtenção de polímeros com valores de PDI muito baixos. O processo NMRP possui vantagens frente à polimerização iônica para produção de polímeros com estrutura controlada, pois nele não são necessários etapas de purificações complexas, sendo que as reações requerem menos condições estritas em relação a impurezas e temperaturas de trabalho. Este é um processo simples e barato, na qual as reações podem ser realizadas em ampolas de vidros / Abstract: Gel Permeation Chromatography, also known as Size Exclusion Chromatography, is the most employed technique to characterize macromolecules such as proteins, copolymers, natural and synthetic polymers. It provides information such as molecular weight distribution (MWD), intrinsic viscosity (IV) and polydispersity (PDI). The importance of its response reflects in terms of polymer processability once the mechanic and chemicals properties are drastically affected by the polymer average molecular weight, chain size and distribution. The standards in the GPC technique have a great importance to obtain reliable results because they are employed in calibration curves needed to acquire the quantitative and qualitative data. Despite the wide use of GPC in Brazil at research centers, chemical and petrochemical industries, all the standards available are obtained outside the country through high importation costs. To change this paradigm, this work aims to develop a national product using the pseudo-living radical polymerization or living free radical polymerization (LFRP), which is a robust and innovative technique in the polymerization science area. The standard chosen was the polystyrene, which is the most used polymer in calibration curves of organic GPC analysis. Our challenge in this work was to obtain a controlled structure polymer with polydispersity index (PDI) between 1 and 1.10, narrow molecular weight distribution (MWD) and high purity degree, using to the best of our knowledge for the first time a mixture of initiators in a NMRP process. The NMRP is a robust and innovative technique compared with the ionic polymerization that is the currently employed process to obtain polymers with very low PDI. The advantages of NMRP process over ionic polymerization to produce controlled structure polymers are that no complicated purification steps are needed, controlled radical reactions require less stringent conditions for impurities and working temperatures, it is a simple and cheaper process, where the reactions can be carried out into glass ampoules / Mestrado / Desenvolvimento de Processos Químicos / Mestre em Engenharia Química

The polymer of intrinsic microporosity PIM-1 was synthesized following various procedures: (i) from fluoro-monomer by the conventional method, (ii) from fluoro-monomer by a high temperature, high shear mixing method and (iii) from chloro-monomer. For a more complete understanding of the structure of the resultant products of a series of polymerizations under different reaction conditions, a multi-detector gel permeation chromatography (GPC) method was established and validated. A procedure for fractionating PIM-1 using chloroform methanol solvent mixtures was established and validated. A combination of multi-detector GPC and matrix-assisted laser desorption/ionization-time of flight (MALDI-ToF) masss pectrometry was used for the determination of molar mass distribution and to identify structural differences between fractions and between the products from different synthetic procedures. High molar mass samples tended to have broader molar mass distributions. Both Mark-Houwink plots and hydrodynamic volume plots showed deviation from linearity at Mw= 200000 g mol-1, which was attributed to branching. A low cost route for the preparation of PIM-1 from chloro-monomer was successfully established, though samples prepared by this route had broader polydispersities than those prepared from fluoro-monomers. It was found that stable flexible membranes were formed from samples with Mw > 83000 g mol -1. In addition, a comparison of two analytical methods for extraction and determination of additives in HDPE, LLDPE and PP polymers of interest to Saudi Basic Industries Corporation was performed. A comparison of dissolution with ultrasonic assisted extraction methods for the determination of anti-oxidant additives in polyolefins was performed. Ultrasound assisted extraction methods were found to be superior for HDPE and LLDPE, where conventional dissolution was preferred for PP.

Pectin has a long history as a food additive. However, elucidation of its fine structural and property relationships remains elusive. Recent research has focused on pectin's ability to complex with divalent heavy metals to aid in characterizing it. Commercial pectins of unknown composition were obtained from local grocers. Purified pectin samples from orange peel, lemon peel, and apple pomace, each of low and high levels of methyl esterification and of unknown distribution pattern were also purchased. Instead of metal complexation, several highly absorbing dyes such as Ruthenium Red, Nile Blue, and Acridine Orange were used to complex with the pectins and their resulting UV-Vis spectral patterns were employed to determine if one can characterize the different pectins. Chemometric methods are also included to aid in distinguishing them apart.