AFM characterization of protein net formation on a fibrous medium

Lysozyme protein net is set on a glass fiber support using the self-assembly technique. Enzymatic film formation is followed by surface imaging via atomic force microscopy (AFM). Change in roughness as a function of deposition time is used as an indirect indicator of film formation. The objective was to form a protein film that would have no effect on the permeability of the medium, aiming at its application as a bioactive membrane or reactor suitable for bacteria and chemical interactions in aqueous media

Tratamentos de silanização em grãos de feijão por hexametildissilazana: resultados preliminares Silanization treatments on beans by hexamethyldisilazane: preliminary results

Grãos comerciais de feijão (Phaseolus vulgaris L.) foram submetidos a tratamentos para formação de filme hidrofóbico por três procedimentos distintos de silanização. A solução precursora foi hexametildissilazana (HDMS) para todos os tratamentos. Os resultados indicam que todas as seqüências tornam a superfície dos grãos resistentes à umidade, reduzindo a absorção em valores de 15 a 57% em comparação às amostras não tratadas. Ensaios de germinação em teste-padrão mostraram que os tratamentos retardam ou evitam a germinação indesejável mesmo em condições de alta umidade.<br>Commercial beans (Phaseolus vulgaris L.) were submitted to silanization treatments aiming at the formation of hydrophobic films. The hexamethyldisilazane (HDMS) was the precursor reagent for all treatments. The results indicate that all sequence generate hydrophobic surface on the crops, reducing the relative absorbed humidity in the range of 15 to 57% when compared to non-treated samples. Standard germination tests showed that the treatments delay or avoid undesirable germination, even in high humidity environment

Mechanical properties of N,N,N-trimethylchitosan chloride films

Films of chitosan and N,N,N-trimethylchitosan were cast from aqueous solutions. Chitosan was dissolved in 1% acetic acid while deionized water was the solvent for N,N,N-trimethylchitosan chloride. The resulting films presented different mechanical behaviors as evaluated by DMTA. The film of chitosan exhibited an elastic-type behavior while that of N,N,N-trimethylchitosan was typically viscous. No glass transition temperatures were observed; however, a discrete thermal transition was detected at 25 °C in the case of the N,N,N-trimethylchitosan

Development of an algorithm for tip-related artifacts identification in AFM biological film imaging

One major drawback identified in atomic force microscopy imaging is the dependence of the image's precision on the shape of the probe tip. In this paper a simple algorithm is proposed to provide artifact identification signaling in-situ tip features in atomic force microscopy images. The base of the identifications lied when the angle formed between two scanned points was kept the same as the tip sweeps a certain length of the sample. The potential of the described method was illustrated on a chitosan polysaccharide film. The images produced were compared to evaluate tip-artifact regions. This algorithm showed promise as a tool in the measurement and characterization fields to separate true images from artificial images in probe microscopy.<br>Um aspecto limitante a plena interpretação de imagens geradas por microscopia de força atômica é a interação entre a superfie varrida e ponta de varredura do sistema gerando artefatos de imagens. Para a identificação desses artefatos, propomos neste texto, um algoritmo simples capaz de assinalar esse tipo de irregularidade de imagem. A medida tem por princípio a identificação de ângulos similares formados entre dois pontos sobre a espécie varrida. O potencial de aplicação do método proposto é aqui ilustrado sobre um filme de polissacarídeo quitosana. As imagens geradas são comparadas entre si, indicando regiões de artefatos típicos gerados pela ponta de varredura. Este algoritmo apresenta-se como uma ferramenta útil a cientistas e usuários, permitindo a separação de aspectos reais e artificiais, que são fundamentais para uma melhor caracterização e medida