The objective of this study is to evaluate the influence of different chemical surface treatments (H 3 PO 4 , HNO 3 , and NaOH) in the formation of calcium phosphate phases on the surface of Al 2 O 3 /ZrO 2 (5 vol%) nanocomposite. For this purpose, Al 2 O 3 /ZrO 2 samples were shaped, calcined at 400°C, sintered at 1500°C, subjected to different chemical treatments, and biomimetically coated from 14 to 21 days. Surface characterization was performed by scanning electron microscopy, atomic force microscopy, confocal microscopy, X-ray diffraction, and infrared spectroscopy. It was observed that the preliminary chemical treatment favored the formation of particular calcium phosphate phases of interest, such as α-TCP (alpha-tricalcium phosphate), β-TCP (betatricalcium phosphate), and HA (hydroxyapatite). The differences among the percentages of the phases formed affected the homogeneity of calcium phosphate distribution within the nanocomposites as well as the roughness of the formed layer, effectively contributing to adhesion, proliferation, and desired cell biofixation on bone implant.

The proline-rich N-terminal domain of gamma-zein has been reported in relevant processes, which include its ability to cross the cell membranes. Evidences indicate that synthetic hexapeptide (PPPVHL), naturally found in N-terminal portion of gamma-zein, can adopt the polyproline II (PPII) conformation in aqueous solution. The secondary structure of gamma-zein in maize protein bodies had been analyzed by solid state Fourier transform infrared and nuclear magnetic resonance spectroscopies. However, it was not possible to measure PPII content in physiological environment since the beta-sheet and PPII signals overlap in both solid state techniques. Here, the secondary structure of gamma-zein has been analyzed by circular dichroism in SDS aqueous solution with and without ditiothreitol (DTT), and in 60% of 2-propanol and water with DTT. The results show that gamma-zein has high helical content in all solutions. The PPII conformation was present at about 7% only in water/DTT solution.

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Atomic Force Microscopy (AFM) can be used to obtain high-resolution topographical images of bacteria revealing surface details and cell integrity. During scanning however, the interactions between the AFM probe and the membrane results in distortion of the images. Such distortions or artifacts are the result of geometrical effects related to bacterial cell height, specimen curvature and the AFM probe geometry. The most common artifact in imaging is surface broadening, what can lead to errors in bacterial sizing. Several methods of correction have been proposed to compensate for these artifacts and in this study we describe a simple geometric model for the interaction between the tip (a pyramidal shaped AFM probe) and the bacterium (Escherichia coli JM-109 strain) to minimize the enlarging effect. Approaches to bacteria immobilization and examples of AFM images analysis are also described.

FTIR. The FTIR spectroscopy has been used to quantify the secondary structures of proteins, using amide I band (1600 -1700 cm -1 ). The resolution enhancement methods have been used to resolve the individual components of this band that correlate to the secondary structure. In this paper we discuss the methods of derivative, Fourier deconvolution and fitting with simulated spectra. The results shows that they have serious problems and can be used only as a qualitative or semiquatitative method.Keywords: methods of resolution enhancement; FTIR; protein. ARTIGO I. INTRODUÇÃOAs técnicas utilizadas para a determinação das estruturas tridimensionais de proteínas em alta resolução são a cristalografia de raios X e a Ressonância Magnética Nuclear (RMN) 1 . A técnica de raios X exige monocristais de alta qualidade, o que não é trivial de obter, principalmente no caso de proteínas de membranas [1][2][3][4][5] . Já a RMN se restringe a proteínas de baixo peso molecular 3 . Dessa forma, técnicas como dicroísmo circular (CD) e as espectroscopias Raman e Infravermelho com transformada de Fourier (FTIR) têm sido utilizadas para quantificar os tipos de estruturas secundárias de proteínas (ESP) presentes nas amostras sem, contudo, determinar as suas localizações [3][4][5] . As principais vantagens dessas técnicas são a rapidez na realização das medidas, o fato de não haver restrições quanto ao peso molecular da proteína em estudo e a não necessidade de cristais.Dentre essas técnicas o FTIR vêm apresentando grandes avanços 2,3,4 pois além de ser uma técnica rápida, permite que a amostra seja analisada em vários ambientes como solução aquosa 3,4,5 , sólido amorfo 6 ou cristalino 3 , filmes 3,6,7,8 , membranas 3,4,5,9 , pastilhas de KBr 10 , além dos espectrômetros de FTIR serem mais facilmente encontrados do que os de Raman e Dicroísmo Circular.A maioria das informações de FTIR sobre as estruturas secundárias das proteínas (α-hélice, folhas β, voltas β e irregulares) é obtida da análise da banda de amida I, que ocorre na região de 1700-1600 cm -1 . Esta banda é devida principalmente ao estiramento da ligação C=O da ligação peptídica e é sensí-vel às diferentes conformações das ESP.A atribuição dos picos da banda de amida I às diferentes estruturas secundárias é encontrada na literatura 11 . Para α-hélices em solução aquosa a absorção ocorre em 1656 cm -1 ; para as folhas β em 1624, 1627, 1632, 1638 e 1642 cm -1 , voltas β em 1666, 1672, 1680, 1688 cm -1 e as irregulares em 1650 cm -1 . Como todos esses sinais podem estar presen-E-mail:lucimara@cnpdia.embrapa.br; E-mail:rubens@cnpdia.embrapa.br; E-mail:colnago@cnpdia.embrapa.br tes numa única proteína, a banda de amida I é uma banda altamente complexa, onde esses componentes não são observados individualmente 5 . Assim o processo de quantificação das ESP a partir de espectros de FTIR envolve o uso de métodos matemáticos como os de aumento de resolução e reconhecimento de padrões [3][4][5]6,8 . Desses métodos os de aumento de resolução são os mais usados 4 e serão analisados neste ...

Estudos do comportamento morfológico dos ácidos fúlvicos foram realizados utilizando a técnica de microscopia de força atômica aliada às técnicas de potencial zeta e espectroscopia de fluorescência. Os resultados mostraram que o ácido fúlvico (AFA) de um rio tropical mudou a sua morfologia quando variado o pH da solução aquosa dos AFA. Em pH ácido a morfologia é mais granular formando aglomerados de altura entre 10-55 nm. Em pH alcalino os valores foram de 2,5-4,0 nm, sendo que a morfologia em condições alcalinas é aberta formando estruturas não granulares. Estes resultados sugerem que para pH 3,5 as interações eletrostáticas são fracas e as ligações de hidrogênio são responsáveis pela formação de agregados, enquanto em pH 9,0 as interações eletrostáticas são fortes devido ao aumento da ionização de grupos fenólicos e ocorrem poucas ligações hidrogênio formando estruturas mais abertas. Os resultados de espectroscopia de fluorescência mostraram mudança na estrutura do AFA de rio tropical em pH alcalino em comparação com a estrutura em pH ácido, corroborando com os resultados obtidos pela AFM.Studies of the morphological behavior of fulvic acids were carried out using the Atomic Force Microscopy technique together with zeta Potential techniques and fluorescence spectroscopy. Results showed that the aquatic fulvic acid (AFA) of a Brazilian River changed its morphology when the AFA aqueous solution had its pH changed. In acid pH the morphology is granular forming 10-55 nm high agglomerates. In alkaline pH values were 2.5-4.0 nm, and the morphology forms non granular structures. These results suggest that for pH 3.0 electrostatic interactions are weak and hydrogen bonding is responsible for the aggregates formation; while at pH 9.0 electrostatic interactions are strong due to the increase in phenolic groups ionization and low hydrogen interaction forming open structures. Fluorescence spectroscopy results confirmed the AFM, that is, a change in the AFA in tropical river in alkaline pH compared to the structure in acid pH.

High-resolution (13)C solid-state NMR stands out as one of the most promising techniques to solve the structure of insoluble proteins featuring biological and technological importance. The simplest nuclear magnetic resonance (NMR) spectroscopy method to quantify the secondary structure of proteins uses the areas of carbonyl and alpha carbon peaks. The quantification obtained by fitting procedures depends on the assignment of the peaks to the structure, type of line shape, number of peaks to be used, and other parameters that are set by the operator. In this paper, we demonstrate that the analysis of (13)C NMR spectra by a pattern recognition method-based on the singular value decomposition (SVD) regression, which does not depend on the operator-shows higher correlation coefficients for α-helix and β-sheet (0.96 and 0.91, respectively) than Fourier transform infrared spectroscopy (FTIR) method. Therefore, the use of (13)C solid-state NMR spectra and SVD is a simple and reliable method for quantifying the secondary structures of insoluble proteins in solid-state.

During the shelf-life of fresh meat, physical, chemical, microbiological, and sensory changes may occur. To avoid such changes, the combination of vacuum-packaging and use of edible coatings make a good strategy. This study aimed to evaluate the physicochemical characteristics of vacuum-packaged lamb meat combined with different zein-based edible coatings containing different vegetable oils (pink pepper, rosemary, olive oil, and the combinations of olive oil + pink pepper or rosemary), stored at 5 ± 1 °C. Parameters including pH, instrumental color, water holding capacity (WHC), shear force, and thiobarbituric acid reactive substances (TBARS) were analyzed every seven days, for 29 days. Significant differences (P<0.05) were observed in coating effects and storage time. The combination of olive oil and pepper oil (OLPP) exhibited higher color stability, while the coatings containing rosemary (RO), rosemary and olive oil (OLRO), and pink pepper oil (PP) exhibited the highest oxidative stability in 29 days. The pH, WHC, and shear force parameters did not appear to have been affected by the coatings. In summary, as appearance is an important purchasing factor, the coating containing olive oil and pink pepper oil is very promising as an alternative for maintaining vacuum-packaged lamb meat quality.