19 research outputs found
Zinc-Silver, Zinc-Palladium, and Zinc-Gold as Bimetallic Systems for Carbon Tetrachloride Dechlorination in Water
Doping of zinc with silver, palladium, and gold was found to increase reactivity towards carbon tetrachloride in water. Commercial zinc dust, cryochemically prepared zinc metal particles (SMAD nanoparticles), and zinc dust pressed into pellets (mechanically activated zinc) were employed. Reduction products detected were methane, ethylene, acetylene, and other hydrocarbons along with products of partial dechlorination such as chloroform, methylene chloride, and methyl chloride. Dichloroethylenes (DCEs) and long-term reactions traces of trichloroethylene (TCE) were also detected. The use of zinc dust doped with palladium, gold, and silver resulted in 4-10 fold increases in carbon tetrachloride degradation rate and conversion into methane. Up to 30% of carbon tetrachloride was converted into methane by the Zn dust / 2 mol % Ag bimetallic system after the first six hours of reaction. Doping of activated forms of zinc, both cryoparticle and pellets, caused a further increase in methane formation and decrease in the concentration of methylene chloride. The data show that bimetallic enhancement with Pd, Ag, Au, as well as cryo and mechanical activation of zinc, enhances the metal surface reactivity and changes the priority of reaction pathways such that fully reduced products are favored. The “non-catalytic” gold metal was especially effective and this suggests that electron transfer, not catalytic hydrogenation, is rate determining
The optical identifcation of events with poorly defined locations: The case of the Fermi GBM GRB140801A
We report the early discovery of the optical afterglow of gamma-ray burst
(GRB) 140801A in the 137 deg 3- error-box of the Fermi Gamma-ray
Burst Monitor (GBM). MASTER is the only observatory that automatically react to
all Fermi alerts. GRB 140801A is one of the few GRBs whose optical counterpart
was discovered solely from its GBM localization. The optical afterglow of GRB
140801A was found by MASTER Global Robotic Net 53 sec after receiving the
alert, making it the fastest optical detection of a GRB from a GBM error-box.
Spectroscopy obtained with the 10.4-m Gran Telescopio Canarias and the 6-m BTA
of SAO RAS reveals a redshift of . We performed optical and
near-infrared photometry of GRB 140801A using different telescopes with
apertures ranging from 0.4-m to 10.4-m. GRB 140801A is a typical burst in many
ways. The rest-frame bolometric isotropic energy release and peak energy of the
burst is erg and
keV, respectively, which is consistent with the
Amati relation. The absence of a jet break in the optical light curve provides
a lower limit on the half-opening angle of the jet deg. The
observed is consistent with the limit derived from the
Ghirlanda relation. The joint Fermi GBM and Konus-Wind analysis shows that GRB
140801A could belong to the class of intermediate duration. The rapid detection
of the optical counterpart of GRB 140801A is especially important regarding the
upcoming experiments with large coordinate error-box areas.Comment: in press MNRAS, 201
Synthetic Circular RNA Functions as a miR-21 Sponge to Suppress Gastric Carcinoma Cell Proliferation
MicroRNA (miR) sponges containing miR binding sequences constitute a potentially powerful molecular therapeutic strategy. Recently, naturally occurring circular RNAs (circRNAs) were shown to function as efficient miR sponges in cancer cells. We hypothesized that synthetic circRNA sponges could achieve therapeutic loss-of-function targeted against specific miRs. Linear RNA molecules containing miR-21 binding sites were transcribed in vitro; after dephosphorylation and phosphorylation, circularization was achieved using 5′-3′ end-ligation by T4 RNA ligase 1. circRNA stability was assessed using RNase R and fetal bovine serum. Competitive inhibition of miR-21 activity by a synthetic circRNA sponge was assessed using luciferase reporter, cell proliferation, and cell apoptosis assays in three gastric cancer cell lines. circRNA effects on downstream proteins were also delineated by Tandem Mass Tag (TMT) labeling (data available via ProteomeXchange identifier PRIDE: PXD008584), followed by western blotting. We conclude that artificial circRNA sponges resistant to nuclease digestion can be synthesized using simple enzymatic ligation steps. These sponges inhibit cancer cell proliferation and suppress the activity of miR-21 on downstream protein targets, including the cancer protein DAXX. In summary, synthetic circRNA sponges represent a simple, effective, convenient strategy for achieving targeted loss of miR function in vitro, with potential future therapeutic application in human patients. Keywords: synthetic circular RNA, microRNA sponge, microRNA loss-of-function, gastric carcinoma, molecular therap
Degradation of 1,2,3-Trichloropropane (TCP): Hydrolysis, Elimination, and Reduction by Iron and Zinc
Proteolysis by Granzyme B Enhances Presentation of Autoantigenic Peptidylarginine Deiminase 4 Epitopes in Rheumatoid Arthritis
Proteolysis
of autoantigens can alter normal MHC class II antigen
processing and has been implicated in the induction of autoimmune
diseases. Many autoantigens are substrates for the protease granzyme
B (GrB), but the mechanistic significance of this association is unknown.
Peptidylarginine deiminase 4 (PAD4) is a frequent target of autoantibodies
in patients with rheumatoid arthritis (RA) and a substrate for GrB.
RA is strongly associated with specific MHC class II alleles, and
elevated levels of GrB and PAD4 are found in the joints of RA patients,
suggesting that GrB may alter the presentation of PAD4 by RA-associated
class II alleles. In this study, complementary proteomic and immunologic
approaches were utilized to define the effects of GrB cleavage on
the structure, processing, and immunogenicity of PAD4. Hydrogen–deuterium
exchange and a cell-free MHC class II antigen processing system revealed
that proteolysis of PAD4 by GrB induced discrete structural changes
in PAD4 that promoted enhanced presentation of several immunogenic
peptides capable of stimulating PAD4-specific CD4+ T cells from patients
with RA. This work demonstrates the existence of PAD4-specific T cells
in patients with RA and supports a mechanistic role for GrB in enhancing
the presentation of autoantigenic CD4+ T cell epitopes