RESUMO
The information processing capabilities of biomolecular excitable media based on nonlinear dynamic mechanisms are discussed. Given even the simplest medium geometry, dynamics and information processing features inherent in biomolecular excitable media proves to be diverse and sophisticated. For the case of pseudo two-dimensional versions these media can be described in terms of neural networks having lateral connections. The main responses of shunting on-center off-surround feedback neural networks and pseudo two-dimensional excitable systems to the external excitations are surprisingly similar. The excitable media are capable of short-time memory, of contour enhancement and quenching or amplifying small features depending on medium state. The analogies discussed reaffirm specific neural net characteristics of excitable media and give the opportunity to estimate more accurate excitable medium characteristics.
Assuntos
Computadores , Modelos Biológicos , Processamento de Imagem Assistida por Computador , Teoria da Informação , Substâncias Macromoleculares , Redes Neurais de Computação , Dinâmica não LinearRESUMO
Purple membranes (PM) from Halobacterium were reconstituted with 57Fe ions and investigated by Mössbauer spectroscopy within the temperature range from 5 to 300 K at the Fe/bacteriorhodopsin (BR) ratio 0.6-300. When the Fe/Br ratio was below 2, Fe3+ bonded to PM mostly as hydroxymonomeric particle [FeOH]2+.5H2O, the apparent charge of the iron ion being two. When the Fe/BR ratio exceeded two, the dimeric form [FeOH](2+)4.8H2O along with a cluster form dominated. The temperature dependences of the mean square displacement show that the mobility of Fe ions changes from the solid-state type to the quasi-diffusional one at temperatures approximately 200 and approximately 230 K for the dimeric or monomeric and cluster iron forms, respectively. The nature of the cation binding sites and their location on the PM surface are discussed. A possible role of the divalent cation binding to PM in the mechanism of BR proton pumping is suggested.
Assuntos
Compostos Férricos/metabolismo , Halobacterium salinarum/metabolismo , Membrana Purpúrea/metabolismo , Sequência de Aminoácidos , Bacteriorodopsinas/química , Bacteriorodopsinas/metabolismo , Cátions , Citoplasma/metabolismo , Espectroscopia de Ressonância de Spin Eletrônica , Compostos Férricos/química , Halobacterium salinarum/química , Halobacterium salinarum/ultraestrutura , Dados de Sequência Molecular , Bombas de Próton/metabolismo , Membrana Purpúrea/química , Espectroscopia de Mossbauer , TemperaturaRESUMO
Basic primitive image-processing operations performed by molecular and biomolecular dynamic media functioning in the oscillating mode are discussed. These operations have rather high computational complexity and can be considered as simulations of human vision capabilities.
Assuntos
Redes Neurais de Computação , Visão Ocular , Simulação por Computador , Humanos , Sistemas de InformaçãoRESUMO
The importance of non-linear dynamic mechanisms for implementing neural network devices at a molecular level is discussed. Information processing devices based on these mechanisms proved to be capable of performing some primitive operations important for image processing.
Assuntos
Redes Neurais de Computação , Algoritmos , Simulação por Computador , Computadores , Enzimas , Processamento de Imagem Assistida por Computador , CinéticaRESUMO
The structure of the Langmuir purple membrane (PM) monolayer was studied by scanning tunneling microscopy (STM). The topography of both the external and cytoplasmic sides of the monolayer was investigated. The thickness of the PM monolayer was determined to be about 4 nm. PM films include specific oval 'crater'-like structures of 50-60 nm in diameter.
