Thesis (Ph. D.)--Oregon State University, 2008. / Printout. Includes bibliographical references (leaves 91-109). Also available on the World Wide Web.

Thesis (Ph. D.)--University of Washington, 1996. / Vita. Includes bibliographical references (leaves [100]-118).

Thesis (Ph. D.)--Marquette University, 2009. / James R. Kincaid, Daniel Sem, Michael D. Ryan, Advisors. Access available to Marquette University only.

München, Techn. Univ., Diss., 2000.

ix, 46 leaves : ill. ; 29 cm Notes Typescript Thesis (M.S.)--University of Oregon, 1987 Includes vita and abstract Bibliography: leaves 37-46 Another copy on microfilm is located in Archives

O pigmento da carne fresca, oximioglobina, e a sua forma oxidada, metmioglobina, podem ser ambos oxidados pela riboflavina quando expostos à radiação luminosa, afetando sua estabilidade redox da carne do ponto de vista nutricional e sensorial. A reação da MbFe(II)O2 e da MbFe(III) com o estado tripleto da riboflavina, 3Rib, envolve uma eficiente transferência de elétrons entre o anel isoaloxazina da riboflavina e a cadeia polipeptídica da proteína, o que leva à formação de cross-link e/ou fragmentação, como demostrado por SDS-PAGE e Western-blot. A constante global de velocidade para a oxidação da MbFe(II)O2 pela 3Rib é (3,0 ± 0,5 ) 109 L·mol-1·s-1 e de (3,1 ± 0,4) 109 L·mol-1·s-1 para a oxidação da MbFe(III) pelo estado tripleto da riboflavina. Cálculos termodinâmicos demonstram ainda que há formação de um complexo exotérmico com estequiometria 1:1 favorecido a temperaturas mais baixas com Ka = (1.2 ± 0.2) 104 mol·L-1 a 25 °C e ΔHo = -112 ± 22 kJ·mol-1 e ΔSo = -296 ± 75 J·mol-1·K-1. Conclui-se que para carne, a riboflavina é um fotossensibilizador para oxidação de proteína e não para a descoloração. / The fresh meat pigment oxymyoglobin, MbFe(II)O2, and its oxidized form metmyoglobin, MbFe(III), are both oxidized by riboflavin as photosensitizer. The reaction of MbFe(II)O2 and MbFe(III) with triplet-state riboflavin, 3Rib, involves the pigment protein, which is oxidatively cleaved or dimerized as shown by SDS-PAGE and Western-blotting, while the heme iron center is not oxidized. The over-all rate constant for oxidation of MbFe(II)O2 by 3Rib is (3.0 ± 0.5) 109 L·mol-1·s-1 and (3.1 ± 0.4) 109 L·mol-1·s-1 for MbFe(III) in aqueous 0.20 mol·L-1 NaCl phosphate buffer of pH 7.4 at 25 °C as determined by transient absorption laser flash photolysis. The high rates are rationalized by ground state hydrophobic interactions as detected as static quenching of fluorescence from singlet-excited state riboflavin by myoglobins using single photon counting time resolved fluorescence spectroscopy and a Stern-Volmer approach. Binding of riboflavin to MbFe(III) has Ka = (1.2 ± 0.2) 104 mol·L-1 at 25 °C with ΔHo = -112 ± 22 kJ·mol-1 and ΔSo = -296 ± 75 J·mol-1·K-1. For meat, riboflavin is concluded to be a photosensitizer for protein oxidation but not for discoloration.

NMR studies of paramagnetic hemoproteins have improved significantly our understanding of the structure-function relationship ofhemoproteins in general. Up to date most of the studies focus on low-spin ferric systems which are characterized by relatively narrow resonance peaks and concomitant better resolution. However, characterizing in detail the NMR spectra of high-spin ferric hemoproteins is important since there are several hemoproteins, such as peroxidases, catalases, oxygenases, and some ferricytochromes that contain high-spin iron (III) in their biologically active forms. Yet assigning resonances from heme peripheral protons and/or heme pocket residues in high-spin myoglobins is a daunting undertaking. Only a sparse number of active site residues are assigned in such instances, even for metaquo-myoglobin. The protons from the heme and heme pocket residues in high-spin complexes experience extremely fast relaxation and very broad linewidths, which impede the 2D methods that detect through-space and through-bond connectivities. It is the intention of this study to develop an effective strategy to gain more resonance assignments for fast-relaxing protons in hemoproteins. We have set out to use a combined strategy, using two-dimensional exchange spectroscopy (2D-EXSY) with two dimensional nuclear Overhauser effect spectroscopy I correlation spectroscopy I total correlation spectroscopy (NOESY/COSY/TOCSY). I demonstrate here that 2D EXSY experiments can be used to obtain assignment correlations for the heme protons of methydroxy-, metthiocyano-, metaquo-, and metimidazole-myoglobin forms. All these assignments are unambiguous and straightforward. Moreover, saturation-transfer experiments allow determination of ligand binding kinetics. Thus, the exchange rates between the metaquo- and metimidazole- or methyl substituted imidazole myoglobin complexes are estimated. The differences between the exchange rates reflect the differences in the hydrophobic and steric interactions between the ligands and the protein moiety. Although I only demonstrate the feasibility of2D EXSY for the myoglobin case, this assignment strategy should to be applicable to other hemoprotein systems.

No description available.

Cristais de mioglobina tipo A foram dopados por processo de difusão com o marcador 2, 2, 6, 6 - tetrametil-l-oxil (TEMPO). Observa-se a existência de uma espécie de marcador isotrópica e outra anisotrópica, que exibe uma simetria axial com A// = 23,4 G, A&#8869 = 20, 6 G e g = 2,0056. São estimados os tempos de correlação rotacional &#964// = 7,2.10-9s e &#964&#8869 = 4,8.10-9s. Uma análise do grau de hidrofobicidade dos resíduos, situados na parte interna da molécula, sugere como um possível sitio de localização para o TEMPO o bolso formado na região da tirosina 103 - hélice H e 151 - terminal 3HC. Este bolso tem tamanho suficiente para abrigar o radical e posição coerente com a heme, o que não acontece com outros sítios. Observa-se uma mudança conformacional da proteína, induzida pela temperatura na região 20-30&#176. Esta pode ser atribuída a um movimento da hélice H. Este resultado somado ao de outros autores indica uma mudança conformacional de grande extensão na molécula. / Type A myoglobin single crystals were doped with the 2, 2, 6, 6 -tetramethyl - 1 - oxyl (TEMPO) spin label by a diffusion process. We observed one isotropic spin label type, and another anisotropic type which shows an axial symmetry with A// = 23,4 G, A&#8869 = 20, 6 G and g = 2,0056. The rotational correlation times are estimated to be a &#964// = 7,2.10-9s and &#964&#8869 = 4,8.10-9s. A quantitative analysis on the hydrophobic nature of the residues situated inside the molecule suggests, as a possible site for the TEMPO, the pocket formed in the region of tyrosine 103-helix H and tyrpsine 151 - terminal 3HC. This pocket is of sufficient size to contain the radical and is positioned in such fashion as to be a compatible with the heme group, this not holding for other sites. A temperature induced conformational change in the protein is observed in the region 20-30&#176, which may be ascribed to a shift of the H helix. This fact, together with the finds of other authors, seems to indicate a generalized temperature induced conformational alteration in the molecule.

O uso de antioxidantes sintéticos para promover a conservação de alimentos tem sido alvo de questionamentos devido a possíveis efeitos tóxicos que estes podem causar. Desse modo, a utilização de substâncias naturais com poder antioxidante mostra-se uma alternativa bastante interessante. Além de conter compostos antioxidantes, muitas plantas também apresentam atividade antimicrobiana, o que tem sido alvo de interesse nas últimas décadas. A cor da carne bovina in natura é um de seus principais atributos, pois a maioria dos consumidores associa esta característica à qualidade do produto no ato da compra. A mioglobina, pigmento responsável pela cor vermelha da carne bovina, uma vez oxidada adquire coloração amarronzada e causa a rejeição da carne. Sua oxidação está ligada também ao processo de oxidação de lipídeos, que igualmente compromete a estabilidade deste produto durante a refrigeração. Desse modo, esta tese teve como objetivo caracterizar extratos aquosos de folhas de pitanga (Eugenia uniflora L.) e alecrim (Rosmarinus officinalis) e de sementes de guaraná (Paullinia cupana Kunth), e avaliar sua aplicação na estabilidade da carne bovina moída refrigerada. Foram realizados 3 experimentos: 1) Caracterização dos materiais vegetais (composição centesimal, teor de clorofila e carotenoides totais) e extratos aquosos (cor, pH, teor de sólidos solúveis, atividade antioxidante pelos métodos do captura do radical DPPH• e o do radical ABTS•+ e capacidade redutora); 2) Estudo da estabilidade da carne bovina moída com extratos vegetais por meio de análises de cor, pH, atividade de água, oxidação lipídica (TBARS), oxidação da mioglobina e análises microbiológicas; e 3) Análise sensorial de cor e odor da carne bovina moída com extratos. Conclui-se que: os extratos vegetais de plantas nativas brasileiras, guaraná e pitanga, apresentaram melhor capacidade antioxidante; os extratos de pitanga promoveram a inibição do crescimento das bactérias testadas; o extrato de pitanga promoveu melhor estabilidade na oxidação de lipídios, além de ter apresentado ação antimicrobiana para bactérias psicrotróficas na carne; a adição de extratos aquosos de pitanga e alecrim à carne bovina moída in natura refrigerada não interferiu na preferência dos atributos de cor e odor, e ainda, que o atributo odor parece estar associado a preferências pessoais. / The use of synthetic antioxidants to promote conservation of foods has been questioned due to possible toxic effects that such substances may cause, thereby the use of natural antioxidant sources seems to be a good alternative. Besides containing antioxidant compounds, many plants also have antimicrobial activity, which has been the subject of interest in recent decades. Color is one of the main attributes of fresh beef, since most consumers associate this characteristic to the quality of the product at the moment of purchase. Myoglobin, the pigment responsible for the red color of beef, once oxidized gets brownish and cause rejection of the product. This protein oxidation is also linked to the lipid oxidation process, which also impairs the stability of the product during cold storage. Thus, this thesis aimed at characterizing aqueous extracts Pitanga (Eugenia uniflora L.) and Rosemary (Rosmarinus officinalis) leaves, and Guarana (Paullinia cupana Kunth) seeds, evaluating their use on the stability of ground refrigerated beef. The experiments were carried out in three steps, namely: 1) Characterization of plant materials (chemical composition, chlorophyll content and carotenoids) and aqueous extracts (color, pH, soluble solids content, antioxidant activity by the methods of radical DPPH• and ABTS•+ scavenging and reducing capacity); 2) Study of the stability of ground beef with plant extracts through color analysis, pH, water activity, lipid oxidation (TBARS), myoglobin oxidation and microbiological analysis; and 3) Sensory analysis of color and odor of ground beef with extracts. As conclusion, the plant extracts of Brazilian native plants, Guarana and Pitanga, showed better antioxidant capacity; Pitanga extracts promoted growth inhibition of the tested bacteria; Pitanga extract provided better stability in the oxidation of lipids, and has presented antimicrobial activity for psychotropic bacteria in the ground beef; the addition of aqueous extracts of Pitanga and Rosemary to fresh ground beef during cold storage for 6 days did not affect the preference of color and odor attributes; odor attribute of beef seems to be associated with personal preferences.