RESUMEN
The effect of acidic pH on the translocation of single-stranded DNA through the α-hemolysin pore is investigated. Two significantly different types of events, i.e. deep blockades and shallow blockades, are observed at low pH. The residence times of the shallow blockades are not significantly different from those of the DNA translocation events obtained at or near physiological pH, whereas the deep blockades have much larger residence times and blockage amplitudes. With a decrease in the pH of the electrolyte solution, the percentage of the deep blockades in the total events increases. Furthermore, the mean residence time of these long-lived events is dependent on the length of DNA, and also varies with the nucleotide base, suggesting that they are appropriate for use in DNA analysis. In addition to being used as an effective approach to affect DNA translocation in the nanopore, manipulation of the pH of the electrolyte solution provides a potential means to greatly enhance the sensitivity of nanopore stochastic sensing.
Asunto(s)
Transporte Biológico Activo , ADN de Cadena Simple/metabolismo , Proteínas Hemolisinas/metabolismo , Modelos Biológicos , Nanoporos , ADN de Cadena Simple/química , Técnicas Electroquímicas , Electrólitos/química , Proteínas Hemolisinas/química , Concentración de Iones de Hidrógeno , Cloruro de SodioRESUMEN
A rapid highly sensitive method to determine sample composition is reported. By monitoring the interaction between the sample of interest and a properly engineered nanopore, information regarding the identities and concentrations of the sample components could be revealed via their characteristic signatures, e.g., blockage amplitudes and event residence times. The sample composition method should be applicable in various research areas, including analytical chemistry, organic synthesis, pharmaceutical industry, etc.
Asunto(s)
Interpretación Estadística de Datos , Ensayo de Materiales/métodos , Modelos Estadísticos , Nanoestructuras/química , Nanoestructuras/ultraestructura , Nanotecnología/métodos , Tamaño de la Partícula , Simulación por Computador , NanoporosRESUMEN
The transmembrane protein α-hemolysin pore has been used to develop ultrasensitive biosensors, study biomolecular folding and unfolding, investigate covalent and noncovalent bonding interactions, and probe enzyme kinetics. Here, we report that, by addition of ionic liquid tetrakis(hydroxymethyl)phosphonium chloride solution to the α-hemolysin pore, the α-hemolysin channel can be controlled open or closed by adjusting the pH of the solution. This approach can be employed to develop a novel molecular switch to regulate molecular transport and should find potential applications as a "smart" drug delivery method.
Asunto(s)
Técnicas Biosensibles , Proteínas Hemolisinas/metabolismo , Líquidos Iónicos/química , Electrólitos/química , Concentración de Iones de Hidrógeno , Cinética , Pliegue de Proteína , Desplegamiento Proteico , beta-Ciclodextrinas/químicaRESUMEN
Biological protein α-hemolysin nanopore is under intense investigation as a potential platform for rapid and low-cost DNA sequencing. However, due to its narrow constriction, analysis of DNA in the α-hemolysin pore has long time been restricted to single strands. In this paper, we report that by introducing new surface functional groups into the α-hemolysin pore, facilitated unzipping of double-stranded DNA through the channel could be achieved. Since the mean residence time of the DNA events is dependent on the length of the duplex, and also varies with the nucleotide base composition, the modified protein pore approach offers the potential for rapid double-stranded DNA analysis, including sequencing.
RESUMEN
Molecular weights of {[3,5-(CF 3) 2Pz]Ag} 3, {[3-(C 3F 7),5-( t-Bu)Pz]Ag} 3, and {[3,5-( i-Pr) 2Pz]Ag} 3 at various solution concentrations have been investigated using vapor-pressure osmometry. Depending on the concentration, the trinuclear {[3,5-(CF 3) 2Pz]Ag} 3 either dissociates into mono- and dinuclear moieties or remains trinuclear or aggregates to hexanuclear species in toluene. In contrast, {[3-(C 3F 7),5-( t-Bu)Pz]Ag} 3, which has a bulky and relatively electron-rich pyrazolate, retains the trinuclear form even at low concentrations in toluene. Both {[3,5-(CF 3) 2Pz]Ag} 3 and {[3,5-( i-Pr) 2Pz]Ag} 3 adopt trinuclear structures in heptane at low concentrations. At higher concentrations, {[3,5-( i-Pr) 2Pz]Ag} 3 forms hexanuclear species. The aggregation-segregation points are rather sharp and are reminiscent of the all-or-none character of phase transitions. Remarkably, at higher concentrations, the aggregation states of these silver pyrazolates are similar to those expected based on solid-state data.
