68 research outputs found
Chemically modified dsRNA induces RNAi effects in insects in vitro and in vivo: a potential new tool for improving RNA-based plant protection
Global agriculture loses over $100 billion of produce annually to crop pests such as insects. Many of these crop pests either are not currently controlled by artificial means or have developed resistance against chemical pesticides. Long dsRNAs are capable of inducing RNAi in insects and are emerging as novel, highly selective alternatives for sustainable insect management strategies. However, there are significant challenges associated with RNAi efficacy in insects. In this study, we synthesized a range of chemically modified long dsRNAs in an approach to improve nuclease resistance and RNAi efficacy in insects. Our results showed that dsRNAs containing phosphorothioate modifications demonstrated increased resistance to southern green stink bug saliva nucleases. Phosphorothioate-modified and 2âČ-fluoro-modified dsRNA also demonstrated increased resistance to degradation by soil nucleases and increased RNAi efficacy in Drosophila melanogaster cell cultures. In live insects, we found chemically modified long dsRNAs successfully resulted in mortality in both stink bug and corn rootworm. These results provide further mechanistic insight into the dependence of RNAi efficacy on nucleotide modifications in the sense or antisense strand of the dsRNA in insects and demonstrate for the first time that RNAi can successfully be triggered by chemically modified long dsRNAs in insect cells or live insects
A Kinematically Complete Measurement of the Proton Structure Function F2 in the Resonance Region and Evaluation of Its Moments
We measured the inclusive electron-proton cross section in the nucleon
resonance region (W < 2.5 GeV) at momentum transfers Q**2 below 4.5 (GeV/c)**2
with the CLAS detector. The large acceptance of CLAS allowed for the first time
the measurement of the cross section in a large, contiguous two-dimensional
range of Q**2 and x, making it possible to perform an integration of the data
at fixed Q**2 over the whole significant x-interval. From these data we
extracted the structure function F2 and, by including other world data, we
studied the Q**2 evolution of its moments, Mn(Q**2), in order to estimate
higher twist contributions. The small statistical and systematic uncertainties
of the CLAS data allow a precise extraction of the higher twists and demand
significant improvements in theoretical predictions for a meaningful comparison
with new experimental results.Comment: revtex4 18 pp., 12 figure
eta-prime photoproduction on the proton for photon energies from 1.527 to 2.227 GeV
Differential cross sections for the reaction gamma p -> eta-prime p have been
measured with the CLAS spectrometer and a tagged photon beam with energies from
1.527 to 2.227 GeV. The results reported here possess much greater accuracy
than previous measurements. Analyses of these data indicate for the first time
the coupling of the etaprime N channel to both the S_11(1535) and P_11(1710)
resonances, known to couple strongly to the eta N channel in photoproduction on
the proton, and the importance of j=3/2 resonances in the process.Comment: 6 pages, 3 figure
Measurement of the Deuteron Structure Function F2 in the Resonance Region and Evaluation of Its Moments
Inclusive electron scattering off the deuteron has been measured to extract
the deuteron structure function F2 with the CEBAF Large Acceptance Spectrometer
(CLAS) at the Thomas Jefferson National Accelerator Facility. The measurement
covers the entire resonance region from the quasi-elastic peak up to the
invariant mass of the final-state hadronic system W~2.7 GeV with four-momentum
transfers Q2 from 0.4 to 6 (GeV/c)^2. These data are complementary to previous
measurements of the proton structure function F2 and cover a similar
two-dimensional region of Q2 and Bjorken variable x. Determination of the
deuteron F2 over a large x interval including the quasi-elastic peak as a
function of Q2, together with the other world data, permit a direct evaluation
of the structure function moments for the first time. By fitting the Q2
evolution of these moments with an OPE-based twist expansion we have obtained a
separation of the leading twist and higher twist terms. The observed Q2
behaviour of the higher twist contribution suggests a partial cancellation of
different higher twists entering into the expansion with opposite signs. This
cancellation, found also in the proton moments, is a manifestation of the
"duality" phenomenon in the F2 structure function
A Precise Measurement of the Neutron Magnetic Form Factor GMn in the Few-GeV2 Region
The neutron elastic magnetic form factor GMn has been extracted from
quasielastic electron scattering data on deuterium with the CEBAF Large
Acceptance Spectrometer (CLAS) at Jefferson Lab. The kinematic coverage of the
measurement is continuous from Q2=1 GeV2 to 4.8 GeV2. High precision was
achieved by employing a ratio technique in which many uncertainties cancel, and
by a simultaneous in-situ calibration of the neutron detection efficiency, the
largest correction to the data. Neutrons were detected using the CLAS
electromagnetic calorimeters and the time-of-flight scintillators. Data were
taken at two different electron beam energies, allowing up to four
semi-independent measurements of GMn to be made at each value of Q2. The dipole
parameterization is found to provide a good description of the data over the
measured Q2 range.Comment: 14 pages, 5 figures, revtex4, submitted to Physical Review Letters,
Revised version has changes recommended by journal referee
Tensor Polarization of the phi meson Photoproduced at High t
As part of a measurement of the cross section of meson photoproduction
to high momentum transfer, we measured the polar angular decay distribution of
the outgoing in the channel in the
center-of-mass frame (the helicity frame). We find that s-channel helicity
conservation (SCHC) holds in the kinematical range where -channel exchange
dominates (up to GeV for =3.6 GeV). Above this
momentum, -channel production of a meson dominates and induces a
violation of SCHC. The deduced value of the coupling constant lies in
the upper range of previously reported values.Comment: 6 pages; 5 figure
Measurement of the - and -Dependence of the Asymmetry on the Nucleon
We report results for the virtual photon asymmetry on the nucleon from
new Jefferson Lab measurements. The experiment, which used the CEBAF Large
Acceptance Spectrometer and longitudinally polarized proton (NH) and
deuteron (ND) targets, collected data with a longitudinally
polarized electron beam at energies between 1.6 GeV and 5.7 GeV. In the present
paper, we concentrate on our results for and the related ratio
in the resonance and the deep inelastic regions for our lowest
and highest beam energies, covering a range in momentum transfer from
0.05 to 5.0 GeV and in final-state invariant mass up to about 3 GeV.
Our data show detailed structure in the resonance region, which leads to a
strong --dependence of for below 2 GeV. At higher , a
smooth approach to the scaling limit, established by earlier experiments, can
be seen, but is not strictly --independent. We add
significantly to the world data set at high , up to . Our data
exceed the SU(6)-symmetric quark model expectation for both the proton and the
deuteron while being consistent with a negative -quark polarization up to
our highest . This data setshould improve next-to-leading order (NLO) pQCD
fits of the parton polarization distributions.Comment: 7 pages LaTeX, 5 figure
Beam Spin Asymmetries in DVCS with CLAS at 4 .8 GeV
We report measurements of the beam spin asymmetry in Deeply Virtual Compton
Scattering (DVCS) at an electron beam energy of 4.8 GeV using the CLAS detector
at the Thomas Jefferson National Accelerator Facility. The DVCS beam spin
asymmetry has been measured in a wide range of kinematics, 1(GeV/c)
(GeV/c), , and 0.1 (GeV/c)
(GeV/c), using the reaction \pEpX. The number of
H and H events are separated in
each bin by a fit to the line shape of the H
distribution. The validity of the method was studied in detail using
experimental and simulated data. It was shown, that with the achieved missing
mass squared resolution and the available statistics, the separation of DVCS-BH
and events can reliably be done with less than 5% uncertainty. The
- and -dependences of the moments of the asymmetry are
extracted and compared with theoretical calculations
The Coupling of Alternative Splicing and Nonsense-Mediated mRNA Decay
Most human genes exhibit alternative splicing, but not all alternatively spliced transcripts produce functional proteins. Computational and experimental results indicate that a substantial fraction of alternative splicing events in humans result in mRNA isoforms that harbor a premature termination codon (PTC). These transcripts are predicted to be degraded by the nonsense-mediated mRNA decay (NMD) pathway. One explanation for the abundance of PTC-containing isoforms is that they represent splicing errors that are identified and degraded by the NMD pathway. Another potential explanation for this startling observation is that cells may link alternative splicing and NMD to regulate the abundance of mRNA transcripts. This mechanism, which we call "Regulated Unproductive Splicing and Translation" (RUST), has been experimentally shown to regulate expression of a wide variety of genes in many organisms from yeast to human. It is frequently employed for autoregulation of proteins that affect the splicing process itself. Thus, alternative splicing and NMD act together to play an important role in regulating gene expression
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