RESUMO
Viable methods for bacterial biofilm remediation require a fundamental understanding of biofilm mechanical properties and their dependence on dynamic environmental conditions. Mechanical test data, such as elasticity or adhesion, can be used to perform physical modelling of biofilm behaviour, thus enabling the development of novel remediation strategies. To achieve real-time, dynamic measurements of these properties, a novel microfluidic flowcell device has been designed and fabricated for in situ analysis using atomic force microscopy (AFM). The flowcell consists of microfluidic channels for biofilm establishment that are then converted into an open architecture, laminar flow channel for AFM measurement in a liquid environment. Finite element analysis (FEA) was used to profile fluid conditions within the flowcell during biofilm establishment. Force-mode AFM was used to measure the elastic properties of mature Pseudomonas aeruginosa PAO1 biofilms as well as polyacrylamide hydrogels. Elastic moduli ranging from 0.58 to 2.61kPa were determined for the mature biofilm, which fall within the range of moduli previously reported by optical, rheometric, and microindentation techniques. These results demonstrate the validity of the microfluidic flowcell system as an effective platform for future investigations of biofilm mechanical and morphological response to dynamic environmental conditions.
Assuntos
Biofilmes/crescimento & desenvolvimento , Técnicas Analíticas Microfluídicas/métodos , Pseudomonas aeruginosa/fisiologia , Aderência Bacteriana , Fenômenos Biomecânicos , Elasticidade , Microscopia de Força Atômica/métodosRESUMO
Recently, well-ordered biological materials have been exploited to pattern inorganic nanoparticles into linear arrays that are of particular interest for nanoelectronic applications. In this work, a de novo designed E. coli-expressed polypeptide (previously shown to form highly rectilinear, ß-sheet-containing structures) operates as a template for divalent metal cations. EDX and TEM analysis verify the attachment of platinum ions to the histidine-rich fibril surface, which was designed specifically to facilitate attachment of chemical moieties. Following chemical reduction, TEM further confirms the formation of localized zero-valent metal aggregates with sub-nanometer interparticle spacing.
Assuntos
Materiais Biocompatíveis/síntese química , Nanotecnologia/métodos , Peptídeos/química , Platina/química , Sequência de Aminoácidos , Materiais Biocompatíveis/análise , Cátions Bivalentes/química , Escherichia coli , Histidina/química , Microscopia Eletrônica de Transmissão , Dados de Sequência Molecular , Peptídeos/genética , Engenharia de Proteínas , Estrutura Secundária de Proteína , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Espectrometria por Raios XRESUMO
A de novo, genetically engineered 687 residue polypeptide expressed in E. coli has been found to form highly rectilinear, beta-sheet containing fibrillar structures. Tapping-mode atomic force microscopy, deep-UV Raman spectroscopy, and transmission electron microscopy definitively established the tendency of the fibrils to predominantly display an apparently planar bilayer or ribbon assemblage. The ordered self-assembly of designed, extremely repetitive, high molecular weight peptides is a harbinger of the utility of similar materials in nanoscience and engineering applications.
Assuntos
Bicamadas Lipídicas/química , Bicamadas Lipídicas/síntese química , Peptídeos/química , Peptídeos/síntese química , Engenharia de Proteínas , Sequência de Bases , DNA/química , DNA/genética , Bicamadas Lipídicas/isolamento & purificação , Microscopia de Força Atômica , Microscopia Eletrônica de Transmissão , Dados de Sequência Molecular , Peso Molecular , Tamanho da Partícula , Peptídeos/isolamento & purificação , Conformação Proteica , Estrutura Secundária de Proteína , Sensibilidade e Especificidade , Análise Espectral RamanRESUMO
Channeling describes the collimated motion of energetic charged particles along the lattice plane or axis in a crystal. The energetic particles are steered through the channels formed by strings of atomic constituents in the lattice. In the case of planar channeling, the motion of a charged particle between the atomic planes can be periodic or quasiperiodic, such as a simple oscillatory motion in the transverse direction. In practice, however, the periodic motion of the channeling particles can be accompanied by an irregular, chaotic behavior. In this paper, the Moliere potential, which is considered as a good analytical approximation for the interaction of channeling particles with the rows of atoms in the lattice, is used to simulate the channeling behavior of positively charged particles in a tungsten (100) crystal plane. By appropriate selection of channeling parameters, such as the projectile energy E(0) and incident angle psi(0), the transition of channeling particles from regular to chaotic motion is demonstrated. It is argued that the fine structures that appear in the angular scan channeling experiments are due to the particles' chaotic motion.
