Fundamental understanding of ionic transport at the nanoscale is essential for developing biosensors based on nanopore technology and new generation high-performance nanofiltration membranes for separation and purification applications. We study here ionic transport through single putatively neutral hydrophobic nanopores with high aspect ratio (of length L = 6 μm with diameters ranging from 1 to 10 nm) and with a well controlled cylindrical geometry. We develop a detailed hybrid mesoscopic theoretical approach for the electrolyte conductivity inside nanopores, which considers explicitly ion advection by electro-osmotic flow and possible flow slip at the pore surface. By fitting the experimental conductance data we show that for nanopore diameters greater than 4 nm a constant weak surface charge density of about 10−2 C m−2 needs to be incorporated in the model to account for conductance plateaus of a few pico-siemens at low salt concentrations. For tighter nanopores, our analysis leads to a higher surface charge density, which can be attributed to a modification of ion solvation structure close to the pore surface, as observed in the molecular dynamics simulations we performed.

APO2L/TRAIL (TNF-related apoptosis-inducing ligand) induces death of tumor cells through two agonist receptors, TRAIL-R1 and TRAIL-R2. We demonstrate here that N-linked glycosylation (N-glyc) plays also an important regulatory role for TRAIL-R1-mediated and mouse TRAIL receptor (mTRAIL-R)-mediated apoptosis, but not for TRAIL-R2, which is devoid of N-glycans. Cells expressing N-glyc-defective mutants of TRAIL-R1 and mouse TRAIL-R were less sensitive to TRAIL than their wild-type counterparts. Defective apoptotic signaling by N-glyc-deficient TRAIL receptors was associated with lower TRAIL receptor aggregation and reduced DISC formation, but not with reduced TRAIL-binding affinity. Our results also indicate that TRAIL receptor N-glyc impacts immune evasion strategies. The cytomegalovirus (CMV) UL141 protein, which restricts cell-surface expression of human TRAIL death receptors, binds with significant higher affinity TRAIL-R1 lacking N-glyc, suggesting that this sugar modification may have evolved as a counterstrategy to prevent receptor inhibition by UL141. Altogether our findings demonstrate that N-glyc of TRAIL-R1 promotes TRAIL signaling and restricts virus-mediated inhibition.

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL or Apo2L) is a member of the tumor necrosis factor (TNF) superfamily. This type II transmembrane protein is able to bound specifically to cancer cell receptors (i.e., TRAIL-R1 (or DR4) and TRAIL-R2 (or DR5)) and to induce apoptosis without being toxic for healthy cells. Because membrane-bound TRAIL induces stronger receptor aggregation and apoptosis than soluble TRAIL, we proposed here to vectorize TRAIL using single-walled carbon nanotubes (SWCNTs) to mimic membrane TRAIL. Owing to their exceptional and revolutional properties, carbon nanotubes, especially SWCNTs, are used in a wide range of physical or, now, medical applications. Indeed due to their high mechanical resistance, their high flexibility and their hydrophobicity, SWCNTs are known to rapidly diffuse in an aqueous medium such as blood, opening the way of development of new drug nanovectors (or nanocarriers). Our TRAIL-based SWCNTs nanovectors proved to be more efficient than TRAIL alone death receptors in triggering cancer cell killing. These NPTs increased TRAIL pro-apoptotic potential by nearly 20-fold in different Human tumor cell lines including colorectal, nonsmall cell lung cancer, or hepatocarcinomas. We provide thus a proof-of-concept that TRAIL nanovector derivatives based on SWCNT may be useful to future nanomedicine therapies.

A hybrid nanoporous membrane made of a solid-state polymeric thin film in which an ion channel is confined is realized. The primary and extremely encouraging results obtained by confocal fluorescence spectroscopy and ion diffusion measurement demonstrate respectively that (i) the considered ion channel, that is, Gramicidin-A, can be confined selectively inside the nanopores and (ii) the ionic permeability of the membrane is enhanced. Atomistic molecular simulations are also reported and fruitfully compared to the experimental findings.

In this work, we report the design and the fine-tuning of boron nitride single nanopore and nanoporous membranes by atomic layer deposition (ALD). First, we developed an ALD process based on the use of BBr and NH as precursors in order to synthesize BN thin films. The deposited films were characterized in terms of thickness, composition, and microstructure. Next, we used the newly developed process to grow BN films on anodic aluminum oxide nanoporous templates, demonstrating the conformality benefit of BN prepared by ALD, and its scalability for the manufacturing of membranes. For the first time, the ALD process was then used to tune the diameter of fabricated single transmembrane nanopores by adjusting the BN thickness and to enable studies of the fundamental aspects of ionic transport on a single nanopore. At pH = 7, we estimated a surface charge density of 0.16 C·m without slip and 0.07 C·m considering a reasonable slip length of 3 nm. Molecular dynamics simulations performed with experimental conditions confirmed the conductivities and the sign of surface charges measured. The high ion transport results obtained and the ability to fine-tune nanoporous membranes by such a scalable method pave the way toward applications such as ionic separation, energy harvesting, and ultrafiltration devices.

The adsorption of small molecules (N 2 ,O 2 , CO, CO 2 ,H 2 O, and HF͒ in model ropes of carbon nanotubes has been studied to determine the main parameters ͑stable adsorption sites, potential barriers, ...) which define the ability of carbon nanotubes to select small molecules through their different behavior in the diffusion mechanism. When the polarization of the nanotubes is taken into account in the semiempirical potentials, it has a significant influence on the adsorption of polar species. Examination of the potential maps along the ropes shows that the nature and the stability of the adsorption sites are strongly dependent on the molecular species and on the diameter of the tubes. For a small rope formed with ͑10,10͒ single-wall nanotubes, different trapping sites are favored by the molecules considered. Furthermore the corresponding trapping well depths are sufficiently selective to discriminate the species. Improving the size homogeneity of the ropes and judiciously calibrating their diameter would provide an efficient mean of selecting molecular species.

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The complex band structure of an isolated polyethylene chain is calculated within Density Functional Theory (DFT). A plane wave basis and ultrasoft pseudopotentials are used. The results are compared with those obtained via a local basis set. We obtain a gap between the highest occupied molecular orbilar (HOMO) and the antibonding unoccupied molecular orbitals of 9.3 eV and a non-resonant tunneling β parameter of 0.9 per monomer, in reasonable agreement with experiment and with results obtained via local basis. Polyethylene is a negative electron affinity material and the actual gap should be the energy of the HOMO with respect to the vacuum level (in DFT approximation only about 5.14 eV). The Bloch states at imaginary k are mainly free-electron-like parabolic bands which are missing in the local basis. We present also the complex bands of the bulk polyethylene in order to estimate the effects of the chain-chain interactions on the complex band structure. The relevance of these results for the tunnelling conduction of n-alkane chains is discussed. * Fellow of TMR FULPROP, EU Contract ERBFMRXCT970155. PACS: 71.20-Rv Band structure of polymers and organic compounds. 71.15-m Methods of electronic structure calculation. 73.63-b Electron transport in nanoscale materials and structures.