We report on DNA translocations through nanopores created in graphene membranes. Devices consist of 1-5 nm thick graphene membranes with electron-beam sculpted nanopores from 5 to 10 nm in diameter. Due to the thin nature of the graphene membranes, we observe larger blocked currents than for traditional solid-state nanopores. However, ionic current noise levels are several orders of magnitude larger than those for silicon nitride nanopores. These fluctuations are reduced with the atomic-layer deposition of 5 nm of titanium dioxide over the device. Unlike traditional solid-state nanopore materials that are insulating, graphene is an excellent electrical conductor. Use of graphene as a membrane material opens the door to a new class of nanopore devices in which electronic sensing and control are performed directly at the pore.

Nanopore sensors have attracted considerable interest for high-throughput sensing of individual nucleic acids and proteins without the need for chemical labels or complex optics. A prevailing problem in nanopore applications is that the transport kinetics of single biomolecules are often faster than the measurement time resolution. Methods to slow down biomolecular transport can be troublesome and are at odds with the natural goal of high-throughput sensing. Here we introduce a low-noise measurement platform that integrates a complementary metal-oxide semiconductor (CMOS) preamplifier with solid-state nanopores in thin silicon nitride membranes. With this platform we achieved a signal-to-noise ratio exceeding five at a bandwidth of 1 MHz, which to our knowledge is the highest bandwidth nanopore recording to date. We demonstrate transient signals as brief as 1 μs from short DNA molecules as well as current signatures during molecular passage events that shed light on submolecular DNA configurations in small nanopores.

Transient receptor potential channels (TRPs) as cellular sensors are thought to function as tetramers. Yet, the molecular determinants governing homotetramerization of heat-activated TRPV1-4 remain largely elusive. In this study, we identified a segment comprising 20 amino acids after the known TRPlike domain in the channel C-terminus that functions as a tetrameric assembly domain (TAD). Purified recombinant C-terminal proteins of TRPV1-4, but not the N-terminus, mediated the protein-protein interaction in in vitro pull-down assay. Western blot analysis combined with confocal calcium imaging further demonstrated that the TAD exerted robust dominant-negative effect on wildtype TRPV1. When fused with membrane-tethered peptide Gap43, the TAD blocked the formation of stable homomultimers, and removal of the TAD from the full length TRPV1 resulted in nonfunctional channels. Calcium imaging and current recording showed that deletion of the TAD in a poreless TRPV1 mutant subunit suppressed its dominantnegative phenotype, confirming the involvement of the TAD in assembly of functional channels. Our findings suggest that the C-terminal TAD in heat-activated TRPV1-4 channels functions as a conserved domain that mediates a direct subunitsubunit interaction for tetrameric assembly.

We report electronic measurements on high-quality graphene nanoconstrictions (GNCs) fabricated in a transmission electron microscope (TEM), and the first measurements on GNC conductance with an accurate measurement of constriction width down to 1 nm. To create the GNCs, freely suspended graphene ribbons were fabricated using few-layer graphene grown by chemical vapor deposition. The ribbons were loaded into the TEM, and a current-annealing procedure was used to clean the material and improve its electronic characteristics. The TEM beam was then used to sculpt GNCs to a series of desired widths in the range 1–700 nm; after each sculpting step, the sample was imaged by TEM and its electronic properties were measured in situ. GNC conductance was found to be remarkably high, comparable to that of exfoliated graphene samples of similar size. The GNC conductance varied with width approximately as G(w) = (e2/h)w0.75, where w is the constriction width in nanometers. GNCs support current densities greater than 120 µA/nm2, 2 orders of magnitude higher than that which has been previously reported for graphene nanoribbons and 2000 times higher than that reported for copper.

We have studied photocurrent generation in large carbon nanotube (CNT) films using electrodes with different spacings. We observe that the photocurrent depends strongly on the position of illumination, with maximum observed response occurring upon illumination at the electrode edges. The rate of change of the response decays exponentially, with the fastest response occurring for samples with the smallest electrode spacing.We show that the time response is due to charge carrier diffusion in lowmobility CNT films.Carbon nanotubes have been considered for incorporation into photovoltaic devices because of their unique electronic and mechanical properties 1,2 . CNT/polymer composites and transparent CNT films have been studied as electrodes 3-5 and photocurrent collectors 6,7 for such devices. Semiconducting CNTs themselves hold promise as photocurrent generators 8,9 because they possess a bandgap suitable to visiblelight wavelengths 2 . It is believed that the Schottky barrier at the CNT-metal interface is