scanning-probe-single-electron-capacitance-spectroscopy

Scanning-probe Single-electron Capacitance Spectroscopy

The integration of low-temperature scanning-probe techniques and single-electron capacitance spectroscopy represents a powerful tool to study the ...

Michigan State University

The metal-reducing bacterium Geobacter sulfurreducens produces conductive protein appendages known as "pilus nanowires" to transfer electrons to metal oxides and to other cells. These processes can be harnessed for the bioremediation of toxic metals and the generation of electricity in bioelectrochemical cells. Key to these applications is a detailed understanding of how these nanostructures conduct electrons. However, to the best of our knowledge, their mechanism of electron transport is not known. We used the capability of scanning tunneling microscopy (STM) to probe conductive materials with higher spatial resolution than other scanning probe methods to gain insights into the transversal electronic behavior of native, cell-anchored pili. Despite the presence of insulating cellular components, the STM topography resolved electronic molecular substructures with periodicities similar to those reported for the pilus shaft. STM spectroscopy revealed electronic states near the Fermi level, consistent with a conducting material, but did not reveal electronic states expected for cytochromes. Furthermore, the transversal conductance was asymmetric, as previously reported for assemblies of helical peptides. Our results thus indicate that the Geobacter pilus shaft has an intrinsic electronic structure that could play a role in charge transport.

Electronic properties of conductive pili of the metal-reducing bacterium Geobacter sulfurreducens probed by scanning tunneling microscopy.

La bact&eacute;rie de r&eacute;duction du m&eacute;tal Geobacter sulfurreducens produit appendices conductrice prot&eacute;ine appel&eacute;es &laquo; pilus nanofils &raquo; pour transf&eacute;rer les &eacute;lectrons &agrave; oxydes m&eacute;talliques et &agrave; d&#39;autres cellules. Ces processus peuvent &ecirc;tre exploit&eacute;es pour la biorestauration des m&eacute;taux toxiques et la production d&#39;&eacute;lectricit&eacute; dans les cellules bioelectrochemical. Cl&eacute; de ces applications est une compr&eacute;hension d&eacute;taill&eacute;e de comment ces nanostructures mener des &eacute;lectrons. Cependant, au meilleur de nos connaissances, leur m&eacute;canisme de transport des &eacute;lectrons ne sait pas. Nous avons utilis&eacute; la capacit&eacute; de la microscopie &agrave; effet tunnel (STM) pour sonder les mat&eacute;riaux conducteurs avec une r&eacute;solution spatiale plus &eacute;lev&eacute;e que les autres m&eacute;thodes balayage de sonde afin de mieux comprendre le comportement &eacute;lectronique transversale d&#39;indig&egrave;ne, ancr&eacute;es &agrave; cellule pili. Malgr&eacute; la pr&eacute;sence d&#39;isolation des composants cellulaires, la topographie de la STM a r&eacute;solu des sous-structures mol&eacute;culaires &eacute;lectroniques avec des p&eacute;riodicit&eacute;s analogues &agrave; celles de l&#39;arbre de pili. Spectroscopie de la STM a r&eacute;v&eacute;l&eacute; des &Eacute;tats &eacute;lectroniques pr&egrave;s le niveau de Fermi, conforme &agrave; un mat&eacute;riau conducteur, mais n&#39;a pas r&eacute;v&eacute;l&eacute; les &Eacute;tats &eacute;lectroniques attendues pour les cytochromes. En outre, la conductance transversale est asym&eacute;trique, comme indiqu&eacute; pr&eacute;c&eacute;demment pour les assemblys de peptides h&eacute;lico&iuml;dales. Ainsi, nos r&eacute;sultats indiquent que l&#39;arbre de pilus Geobacter a une structure &eacute;lectronique intrins&egrave;que qui pourrait jouer un r&ocirc;le dans le transport de charge.

Propri&eacute;t&eacute;s &eacute;lectroniques des pili conductrices de la bact&eacute;rie de r&eacute;duction du m&eacute;tal Geobacter sulfurreducens sond&eacute; par microscopie &agrave; effet tunnel.

Il riduzione del metallo batterio Geobacter sulfurreducens produce appendici conduttivo proteina conosciute come &quot;nanofili pilus&quot; per trasferire elettroni di ossidi metallici e di altre cellule. Questi processi possono essere sfruttati per il biorisanamento di metalli tossici e la generazione di energia elettrica nelle cellule bioelectrochemical. Chiave per queste applicazioni &egrave; una dettagliata comprensione di come queste nanostrutture conducono gli elettroni. Tuttavia, al meglio delle nostre conoscenze, il meccanismo di trasporto degli elettroni non &egrave; noto. Abbiamo utilizzato la capacit&agrave; di scanning tunneling microscopy (STM) per sondare materiali conduttivi con maggiore risoluzione spaziale rispetto ad altri metodi di sonda scansione per acquisire conoscenze sul comportamento elettronico trasversale di pili nativi, ancorata in cella. Nonostante la presenza di componenti cellulari di isolamento, la topografia STM risolti elettroniche molecolare sostruzioni con periodicit&agrave; simili a quelle riportate per l&#39;albero di pilus. Spettroscopia di STM ha rivelato gli Stati elettronici vicino al livello di Fermi, coerente con un materiale conduttore, ma non hanno rivelato stati elettronici previsti per i citocromi. Inoltre, la conduttanza trasversale era asimmetrica, come precedentemente segnalato per gli assembly di peptidi elicoidale. Cos&igrave; i nostri risultati indicano che l&#39;albero di pilus Geobacter ha un&#39;intrinseca struttura elettronica che potrebbe giocare un ruolo nel trasporto di carica.

Stuart Tessmer

Biography

JoVE Journal Publications

Other Publications