RESUMEN
The sensitivity of optical biosensors where the detection takes place on a planar gold surface can be improved by making the surface porous. The porosity allows a larger number of ligands per surface area resulting in larger optical shifts when interacting with specifically binding analyte molecules. The porous gold was deposited as a thin layer on a planar gold surface by electrochemical deposition in a solution of tetrachloroaurate and lead acetate. A protein, streptavidin, was adsorbed into the formed porous layer and the time course of the adsorption was monitored by in-situ ellipsometry. When the porous layer was 500 nm in thickness a six-fold increase of the ellipsometric response was obtained compared with a planar gold surface. The dependency of porosity and layer thickness was explained with a mathematical model of the gold/porous gold/protein/solution system.
Asunto(s)
Técnicas Biosensibles/métodos , Oro , Adsorción , Técnicas Biosensibles/estadística & datos numéricos , Microscopía Electrónica de Rastreo , Modelos Teóricos , Sensibilidad y Especificidad , Estreptavidina , Propiedades de SuperficieRESUMEN
This study was designed to explore young children's strategy development using a new kind of "same-different" task that minimized memory demands. Four-year-old children were asked to judge whether 2 sets of 7 toys were the same or different. Sets were identical or differed by one toy, with one set presented on a table and the other in a linen bag. Children's spontaneous behavior was highly strategic, and over trials it developed differently for "same" and "different" trials. Most children who did not spontaneously use the most effective strategy, that is, matching, could be trained to do so and were able to transfer this strategy to new materials. Results concerning production and utilization deficiencies are discussed in relation to task characteristics, trial type (same or different), and findings from prior research.
Asunto(s)
Conducta Infantil/psicología , Memoria/fisiología , Enseñanza , Preescolar , Cognición/fisiología , Femenino , Humanos , Juicio , Masculino , Juego e Implementos de JuegoRESUMEN
Porous silicon dioxide surfaces have been used for monitoring the specific affinity binding of low molecular weight molecules to streptavidin. Streptavidin was immobilized to the porous silicon dioxide surface by spontaneous adsorption at pH 7.4. Binding of biotin and an oligopeptide synthesized by means of combinatorial chemistry were monitored with an in situ null ellipsometer. Measurements were also done with hydroxy-azobenzene-2-carboxylic acid and DL-6-8-thioctic acid amide. The performance of porous silicon dioxide as a potential surface in biosensor applications was compared with a planar silicon dioxide surface. Porous silicon dioxide showed a 10-fold amplification of the response compared to planar silicon dioxide. It was possible to monitor the binding of biotin and the oligopeptide in the concentration range 2-40 microM. A response time as low as 30 s was obtained for the oligopeptide at 40 microM.
Asunto(s)
Técnicas Biosensibles , Silicio , Estreptavidina , Adsorción , Secuencia de Aminoácidos , Biotina , Rayos Láser , Datos de Secuencia Molecular , Peso Molecular , Oxidación-Reducción , Porosidad , Conformación ProteicaRESUMEN
Formation and special consequences of water-ordering are studied and discussed. Based on the knowledge of the water states, a special dynamic clustering (called dynamic frustration) is suggested. This can be an essential mechanism for life processes. A frustration mechanism and its consequences are discussed.
Asunto(s)
Agua/química , Agua/fisiología , Animales , Fenómenos Químicos , Química Física , Humanos , Modelos QuímicosRESUMEN
Twenty-seven male-to-female transsexuals underwent genital transformation. The cosmetic and functional results of 11 vagina constructions using only inverted penile skin were compared with 16 constructions using penile and scrotal skin flaps. Subjective (interview) and objective (physical examination) results are presented. The main conclusions are that vaginal width and subjective evaluation of functional aspects were clearly better after penile and scrotal skin inversion, especially when there was adequate dilatation by the patient. In addition, fewer complications were encountered. Cosmesis was judged better in the penile skin inversion group.