38 research outputs found
Long range electronic transport in DNA molecules deposited across a disconnected array of metallic nanoparticles
We report in detail our experiments on the conduction of DNA
molecules over a wide range of temperature deposited across slits in a few
nanometers thick platinum film. These insulating slits were fabricated using
focused ion beam etching and characterized extensively using near field and
electron microscopy. This characterization revealed the presence of metallic Ga
nanoparticles inside the slits, as a result of the ion etching. After
deposition of DNA molecules, using a protocol that we describe in
detail, some of the slits became conducting and exhibited superconducting
fluctuations at low temperatures. We argue that the observed conduction was due
to transport along DNA molecules, that interacted with the Ga nanoparticles
present in the slit. At low temperatures when Ga becomes superconducting,
induced superconductivity could therefore be observed. These results indicate
that minute metallic particles can easily transfer charge carriers to attached
DNA molecules and provide a possible reconciliation between apparently
contradictory previous experimental results concerning the length over which
DNA molecules can conduct electricity
Novel bimodular DNA aptamers with guanosine quadruplexes inhibit phylogenetically diverse HIV-1 reverse transcriptases
DNA aptamers RT5, RT6 and RT47 form a group of related sequences that inhibit HIV-1 reverse transcriptase (RT). The essential inhibitory structure is identified here as bimodular, with a 5′ stem–loop module physically connected to a 3′-guanosine quadruplex module. The stem–loop tolerates considerable sequence plasticity. Connections between the guanosine triplets in the quadruplex could be simplified to a single nucleotide or a nonnucleic acid linker, such as hexaethylene glycol. All 12 quadruplex guanosines are required in an aptamer retaining most of the original loop sequence from RT6; only 11 are required for aptamer R1T (single T residue in intra-quadruplex loops). Circular dichroism (CD) spectroscopy gave ellipticity minima and maxima at 240 nm and 264 nm, indicating a parallel arrangement of the quadruplex strands. The simplified aptamers displayed increased overall stability. An aptamer carrying the original intra-quadruplex loops from RT6 inhibited RT in K+ buffers but not in Na+ buffers and displayed significant CD spectral broadening in Na+ buffers, while R1T inhibited RT in both buffers and displayed less broadening in Na+ buffers. The bimodular ssDNA aptamers inhibited RT from diverse primate lentiviruses with low nM IC50 values. These data provide insight into the requirements for broad-spectrum RT inhibition by nucleic acid aptamers
HIV-1 Protease and Reverse Transcriptase Control the Architecture of Their Nucleocapsid Partner
The HIV-1 nucleocapsid is formed during protease (PR)-directed viral maturation, and is transformed into pre-integration complexes following reverse transcription in the cytoplasm of the infected cell. Here, we report a detailed transmission electron microscopy analysis of the impact of HIV-1 PR and reverse transcriptase (RT) on nucleocapsid plasticity, using in vitro reconstitutions. After binding to nucleic acids, NCp15, a proteolytic intermediate of nucleocapsid protein (NC), was processed at its C-terminus by PR, yielding premature NC (NCp9) followed by mature NC (NCp7), through the consecutive removal of p6 and p1. This allowed NC co-aggregation with its single-stranded nucleic-acid substrate. Examination of these co-aggregates for the ability of RT to catalyse reverse transcription showed an effective synthesis of double-stranded DNA that, remarkably, escaped from the aggregates more efficiently with NCp7 than with NCp9. These data offer a compelling explanation for results from previous virological studies that focused on i) Gag processing leading to nucleocapsid condensation, and ii) the disappearance of NCp7 from the HIV-1 pre-integration complexes. We propose that HIV-1 PR and RT, by controlling the nucleocapsid architecture during the steps of condensation and dismantling, engage in a successive nucleoprotein-remodelling process that spatiotemporally coordinates the pre-integration steps of HIV-1. Finally we suggest that nucleoprotein remodelling mechanisms are common features developed by mobile genetic elements to ensure successful replication
Nucleocapsid protein: A desirable target for future therapies against HIV-1
8noneThe currently available anti-HIV-1 therapeutics is highly beneficial to infected patients. However, clinical failures occur as a result of the ability of HIV-1 to rapidly mutate. One approach to overcome drug resistance is to target HIV-1 proteins that are highly conserved among phylogenetically distant viral strains and currently not targeted by available therapies. In this respect, the nucleocapsid (NC) protein, a zinc finger protein, is particularly attractive, as it is highly conserved and plays a central role in virus replication, mainly by interacting with nucleic acids. The compelling rationale for considering NC as a viable drug target is illustrated by the fact that point mutants of this protein lead to noninfectious viruses and by the inability to select viruses resistant to a first generation of anti-NC drugs. In our review, we discuss the most relevant properties and functions of NC, as well as recent developments of small molecules targeting NC. Zinc ejectors show strong antiviral activity, but are endowed with a low therapeutic index due to their lack of specificity, which has resulted in toxicity. Currently, they are mainly being investigated for use as topical microbicides. Greater specificity may be achieved by using non-covalent NC inhibitors (NCIs) targeting the hydrophobic platform at the top of the zinc fingers or key nucleic acid partners of NC. Within the last few years, innovative methodologies have been developed to identify NCIs. Though the antiviral activity of the identified NCIs needs still to be improved, these compounds strongly support the druggability of NC and pave the way for future structure-based design and optimization of efficient NCIs.noneMori, Mattia; Kovalenko, Lesia; Lyonnais, Sébastien; Antaki, Danny; Torbett, Bruce E.; Botta, Maurizio; Mirambeau, Gilles; Mély, YvesMori, Mattia; Kovalenko, Lesia; Lyonnais, Sébastien; Antaki, Danny; Torbett, Bruce E.; Botta, Maurizio; Mirambeau, Gilles; Mély, Yve
Object oriented model and method applied to build an expert system for intoxication diagnoses
SIGLEAvailable at INIST (FR), Document Supply Service, under shelf-number : DO 2196 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc
Une methode de developpement au service des acteurs qui developpent un systeme expert :'Q4' \Qui, Quid, Quomodo, Quando\
SIGLEAvailable at INIST (FR), Document Supply Service, under shelf-number : DO 1052 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc
Resolving heterogeneity in a multidatabase environment through an 0-0 model
SIGLEAvailable at INIST (FR), Document Supply Service, under shelf-number : DO 1064 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc
Cooperation between heterogeneous databases using an 0.0. model
SIGLEAvailable at INIST (FR), Document Supply Service, under shelf-number : DO 1055 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc