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Free energy calculations of biopolymeric systems at cellular interfaceYang, Tianyi 26 May 2010 (has links)
Cells interact with both tethered and motile ligands in their extra-cellular environment, which mediates, initiates and regulates a series of cellular functions, such as cell adhesion, migration, morphology, proliferation, apoptosis, bi-directional signal transduction, tissue homeostasis, wound healing among others. A fundamental understanding of the thermodynamics of receptor-mediated cell interaction is necessary not only from the aspect of physiology, but also for bioengineering applications, e.g. drug discovery, tissue engineering and biomaterial fabrication. Our models on free energy calculations of receptor mediated cell-matrix interactions supplement computational endeavors based on continuum mechanics. By incorporating conformational, entropic, solvation, steric effect, implicit and explicit interactions of receptors and extra-cellular ligand molecules, we can predict free energy, chemical equilibrium constant of binding, spatial and conformational distributions of biopolymers, adhesion force as functions of a set of key variables, e.g. surface coverage of receptor, interaction distance between cell and substrate, specific binding energy, implicit interaction strength, constraint in ligand’s conformation, size of motile nano-ligand, aggregation of receptors, sliding velocity relative to fluid. Our work has improved understanding of phenomena in cell-matrix interactions at both cellular and the molecular scales. / text
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Relationships between material properties and microstructure-mechanical attributes of extruded biopolymeric foamsAgbisit, Roderick Nazario Malcaba January 1900 (has links)
Doctor of Philosophy / Department of Grain Science and Industry / Sajid Alavi / Material formulation and extrusion process parameters affect the foaming process in terms of expansion, cell nucleation, and resultant foam microstructure, which, in turn, control mechanical properties. This study utilizes non-invasive x-ray microtomography (XMT), in combination with mechanical testing and novel phase transition analysis techniques, to understand these complex relationships. The first part of this study provided significant insight into the deformation mechanism of extruded cornstarch foams. Microstructure features, including average cell diameter (2.07-6.32 mm), wall thickness (0.13-0.25 mm) and number density (18-146 cm-3), were measured. Microstructure had moderate to high correlations (|r| = 0.48 - 0.81) with mechanical properties, including compression modulus (2.2-7.8 MPa), crushing stress (42-240 kPa), number of spatial ruptures (2.6-3.6 mm-1), average crushing force (22-67 N) and crispness work (6.4-22 N-mm). The second part of this study investigated the effects of formulation, using model systems comprising of cornstarch, whey protein isolate (WPI) and sucrose, on phase transition behavior, and physical, microstructure and mechanical properties of extrudates. Increase in WPI led to greater specific mechanical energy (SME) and higher extrudate expansion. WPI had a foaming effect, which increased the cell number density accompanied by decrease in average cell diameter. Increase in sucrose led to lesser SME and lower expansion of extrudates. Contrary to expectations, phase transition properties (softening temperature, Ts, and flow temperature, Tf) were not good indicators of SME. The concluding part of this study investigated glass transition and rheological properties of cornstarch at different moisture contents (18-30% wet basis) using differential scanning calorimetry (DSC), phase transition analysis (PTA) and on-line slit-die rheometry. Glass transition temperature (Tg) (31.20 - 57.55 C) of extrudates decreased as moisture content increased. Ts (42.5 - 85.6C) and Tf (109 - 136C) also followed the same trend, and exhibited high correlations (r = 0.89 and 0.86, respectively) with Tg. These parameters were good estimates of phase transition properties of the complex and heterogeneous formulations. As expected, on-line rheological parameters, including flow behavior index, n (0.0438 - 0.304) and consistency coefficient, K (10,500 - 45,700 Pa-sn-1), were functions of in-barrel moisture, and were related to phase transition properties using WLF kinetics.
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Síntese, caracterização e estudo da atividade biológica de bases de Schiff biopoliméricas, preparadas a partir de quitosanas e salicilaldeídos e seus complexos de Zn(II), Pd(II) e Pt(II) / Synthesis, characterization and study of the biological activity of biopolymeric Schiff bases prepared of chitosan and salicylaldehydes and their complexes of Zn(II), Pd(II) and Pt(II)Barbosa, Hellen Franciane Gonçalves 27 April 2018 (has links)
Este trabalho teve como objetivo a síntese e a caracterização de bases de Schiff biopoliméricas e alguns de seus complexos metálicos formados a partir do biopolímero quitosana. Na primeira etapa do trabalho foram utilizados o salicilaldeído e seus derivados, 5-metóxisalicilaldeído e 5-nitrosalicilaldeído para produzir as bases de Schiff biopoliméricas com a quitosana (GD = 90,4 %, Mw =223 kDa), as quais foram utilizadas para a síntese dos complexos de Zn(II), Pd(II) e Pt(II). Na segunda etapa, bases de Schiff biopoliméricas anfifílicas foram sintetizadas utilizando as quitosanas (GD = 90,4 e 89%, Mw = 223 e 64 kDa), e o grupo hidrofóbico salicilaldeído bem como o grupo hidrofílico 2,3-epóxi-1-propanol (glicidol). E esses ligantes também foram utilizados para complexar os metais Zn(II), Pd(II) e Pt(II). As bases de Schiff biopoliméricas anfifílicas foram sintetizadas a fim de se avaliar o efeito da presença do grupo hidrofílico glicidol e também o da variação dos valores de Mw nas propriedades físico-químicas e biológicas. Todos os compostos sintetizados foram caracterizados por espectroscopia (1H-RMN, FTIR, DRX, UV-Vis), análise térmica (TG/DTG-DTA) e microscopia (MEV-EDX). Afim de se avaliar a atividade biológica das bases de Schiff biopoliméricas e seus complexos foram utilizados dois agentes patógenos de plantas: a bactéria Gram-negativa Pseudomonas syringae pv. tomato e o fungo de cerais Fusarium graminearum. Os resultados obtidos demostraram que tanto as bases de Schiff biopoliméricas quanto seus complexos exibiram atividade antibacteriana significante. Entretanto, o potencial antifúngico das bases de Schiff foi melhor que para alguns complexos, devido a diferença morfológica relacionada a constituição da membrana celular externa e da parede celular dos microrganismos testados. Portanto, foi observado que a morfologia é um fator diretamente relacionado aos mecanismos de ação. A avaliação da citotoxicidade foi realizada in vitro contra células de carcinoma de mama MCF-7 por ensaio de MTT. Os resultados de citotoxicidade obtidos demonstraram que todos os compostos apresentaram uma diminuição na percentagem da viabilidade celular, em função da concentração. Observou-se para as bases de Schiff biopoliméricas uma atividade antitumoral mais efetiva que para as quitosanas sem modificação. Em baixas concentrações dos complexos, observou-se uma baixa inibição celular, especialmente para os complexos de zinco. Porém, em concentrações mais elevadas, foi verificado um aumento significativo da toxicidade. Portanto, a principal contribuição esperada deste trabalho foi a síntese, caracterização e estudo desses novos compostos de bases de Schiff biopoliméricas e dos biocomplexos, com potencial para atuar em aplicações biológicas. / Biopolymeric Schiff bases prepared from chitosan and some of their complexes were synthesized, characterized and evaluated regarding their biological activity. In a first step, salicylaldehyde, 5-methoxysalicylaldehyde and 5-nitrosalicylaldehyde were used to synthesize biopolymeric Schiff bases with chitosan (GD = 90.4 %, Mw =223 kDa), as well as their Zn(II), Pd(II) and Pt(II) complexes. In a second stage, amphiphilic biopolymeric Schiff bases were prepared from two different chitosans (GD = 90.4 and 89%, Mw = 223 e 64 kDa), but introducing the salicylaldehyde hydrophobic group and also 2,3-epoxy-1-propanol (glycidol) hydrophilic group. Zn(II), Pd(II) and Pt(II) complexes where prepared from such amphiphilic biopolimeric ligands. All these ligands and respective complexes were obtained in order to evaluate the effect of increased solubility caused by glycidol the hydrophilic group and as well as the different Mw values in physical chemical and biological properties. Thus different spectroscopic (1H-NMR, FTIR, XRD, UV-Vis), thermal analytical (TG/DTG-DTA) and microscopy (MEV-EDX) techniques were used to characterize all the compounds. The biological activity was evaluated against two economically important plant pathogens, Gram-negative bacteria Pseudomonas syringae pv. tomato and Fusarium graminearum cereal fungus. In general, the results demonstrated that biopolymer Schiff bases and their complexes exhibited significant antibacterial activity. However, the antifungal potential of the Schiff bases was better than for some complexes, due to the morphological difference related to the constitution of the cell membrane and cell wall of the tested microorganisms. Therefore, it was observed that morphology is a factor directly related to the mechanisms of action. Cytotoxicity was evaluated in vitro against breast cancer cells (MCF-7) using MTT. The results of cytotoxicity against MCF-7 cells demonstrated a decrease in the cell viability as a function of the concentration, for all the samples tested, being the biopolymeric Schiff bases were more effective antitumor agent than chitosan itself. In lower concentration, the complexes did not show effective decrease on cells viability, especially for zinc complexes. However, at high concentrations a significant increase of cytotoxicity was observed. Therefore, the main contribution expected these work was the synthesis, characterization and biological activity evaluation of these new biopolymeric Schiff bases and complexes, aiming to evaluate the antimicrobial and antitumor activity.
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Produção, avaliação e aplicação de filmes nanocompósitos obtidos a partir de extrato proteico da microalga spirulina platensisFurtado, Ariane Schmidt January 2013 (has links)
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Previous issue date: 2013 / A microalga Spirulina platensis é uma fonte renovável e não-convencional de proteínas
que pode ser aplicada na confecção de filmes biopoliméricos, para serem utilizados na
produção de embalagens biodegradáveis, minimizando agressões ao meio ambiente e
agregando valor a esta matéria-prima antes utilizada principalmente como ração animal.
Com base nisso, este trabalho teve por objetivo a produção, avaliação e aplicação de
filmes nanocompósitos obtidos a partir de extrato proteico proveniente da microalga
Spirulina platensis. Para tanto, inicialmente foi obtido um extrato proteico da Spirulina
(EPS) através de extração química por variação do pH. Este extrato, contendo 64 % de
proteína (base seca), foi avaliado quanto à sua composição de aminoácidos e
caracterizado quanto à sua funcionalidade (solubilidade; capacidade de retenção de água
e óleo; capacidade espumante; estabilidade espumante). Posteriormente, o EPS foi
utilizado como matéria-prima para obtenção de filmes proteicos nanocompósitos com
adição de nanoargila montmorilonita (MMT). A obtenção dos mesmos foi realizada
através do preparo de soluções filmogênicas, seguido da técnica de casting e secagem a
40 °C (±2 °C) em estufa com circulação de ar. Foram utilizados dois tipos de
planejamento: um para avaliar as variáveis do processo de obtenção dos filmes
(Planejamento Fatorial Fracionário) e outro para determinar as melhores condições de
obtenção dos filmes (Delineamento Central Composto Rotacional - DCCR). Os filmes
foram avaliados quanto às suas propriedades mecânicas (resistência à tração - RT, e
elongação) e ópticas (diferença de cor - ΔE* e opacidade – Y %), espessura,
permeabilidade ao vapor de água (PVA), solubilidade em água e umidade (U %). Com
base na menor PVA (8,51 g.mm.(kPa. d. m2
)
-1
) e umidade (12,7 %), o filme escolhido
para ser utilizado como parte de um sistema de embalagem individual para massa de
pizza teve a seguinte formulação: 4,5 g de EPS, 1,35 g de glicerol e 0,1 g de MMT em
150 mL de água destilada, pH 11,0 e temperatura final do processo de 75 °C (ensaio 5 do
DCCR). Ele foi um dos filmes menos espesso (0,092 mm), elástico (elongação de 16 %),
escuro e opaco, apresentou RT de 2,49 MPa (dentre as maiores) e foi o mais solúvel dos
filmes, com solubilidade de 69,2 %. Foi avaliada a eficiência deste filme como parte do
sistema de embalagem através de análises de perda de massa, textura e contagem de
bolores e leveduras nas pizzas. Verificou-se que o mesmo não foi eficiente em conservar
as massas de pizza, pois permitiu uma grande perda de massa e alterações inaceitáveis na
textura, indicando assim uma alta permeabilidade ao vapor de água, o que também é
indesejável. De modo geral, concluiu-se que é possível obter um extrato proteico a partir
de Spirulina e aplicá-lo como matéria-prima de filmes proteicos nanocompósito com
adição de MMT. No entanto, o filme em questão não foi eficiente quando aplicado como
embalagem para conservação de massa de pizza. / Microalgae Spirulina platensis are a renewable, unconventional source of protein which
can generate biopolymeric films to be applied on the production of biodegradable
packaging, minimizing environmental damage and adding economic value to a raw
material mostly used as animal feed. Based on that, the purpose of this study was to
product, evaluate and test an application of nanocomposite films obtained from protein
concentrate of Spirulina platensis microalgae. In that regard, a Spirulina-based protein
concentrate (SPC) was developed by chemical extraction through pH-shift process. This
concentrate contains 64 % protein (dry base) and the tests analyzed its amino acid
composition and its functionality (solubility; water/oil absorption capability; capacity of
producing foam; foam stability). Afterwards, the SPC was used as raw material to
produce nanocomposite protein films with addition of montmorillonite nanoclay (MMT).
The production was done using filmogenic solutions, followed by casting and drying at
40 °C (±2 °C) in incubator with blower. Two types of planning were used: Fractional
Factorial Planning (FFP), to evaluate film-producing process variables, and Central
Composite Rotational Delineation (CCRD), to settle the best conditions to make the
films. Those films had their mechanical (tensile strength – TS and elongation) and optical
(color deviation and opacity) properties analyzed, as well as thickness, water steam
permeability, solubility in water and humidity. Based on the smaller permeability (8.51
g.mm.(kPa. d. m2
)
-1
) and humidity (12.7 %), the film chosen for use as part of a system of
individual packing for pizza dough had the following formulation: 4.5 g of SPC, 1.35 g of
glycerol and 0.1 g of MMT in 150 mL of distilled water, pH 11.0 and final process
temperature of 75 ºC (CCRD sample no. 5). That film was one of the thinnest (0.092 mm)
and less elastic (16 % of elongation), dark and opaque, as well as it had a TS of 2.49 MPa
(one of the highest) and was the most soluble (69.2 % of solubility). Its efficiency as part
of a packaging system was evaluated by texture, mass losses and mold and yeast count.
The tests showed that the film is inefficient to preserve pizza dough, since it was unable
to avoid large mass losses and inacceptable texture modifications, indicating moreover
high permeability to water steam, which is also undesirable. In conclusion, it is possible
to obtain a Spirulina-based protein concentrate and use it to make nanocomposite protein
films with addition of MMT. Nevertheless, the film tested in this study is inefficient as
part of a packaging system for pizza dough.
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