53 research outputs found
Neutralization of the edema-forming, defibrinating and coagulant effects of Bothrops asper venom by extracts of plants used by healers in Colombia
We determined the neutralizing activity of 12 ethanolic extracts of plants against the edema-forming, defibrinating and coagulant effects of Bothrops asper venom in Swiss Webster mice. The material used consisted of the leaves and branches of Bixa orellana (Bixaceae), Ficus nymphaeifolia (Moraceae), Struthanthus orbicularis (Loranthaceae) and Gonzalagunia panamensis (Rubiaceae); the stem barks of Brownea rosademonte (Caesalpiniaceae) and Tabebuia rosea (Bignoniaceae); the whole plant of Pleopeltis percussa (Polypodiaceae) and Trichomanes elegans (Hymenophyllaceae); rhizomes of Renealmia alpinia (Zingiberaceae), Heliconia curtispatha (Heliconiaceae) and Dracontium croatii (Araceae), and the ripe fruit of Citrus limon (Rutaceae). After preincubation of varying amounts of each extract with either 1.0 µg venom for the edema-forming effect or 2.0 µg venom for the defibrinating effect, the mixture was injected subcutaneously (sc) into the right foot pad or intravenously into the tail, respectively, to groups of four mice (18-20 g). All extracts (6.2-200 µg/mouse) partially neutralized the edema-forming activity of venom in a dose-dependent manner (58-76% inhibition), with B. orellana, S. orbicularis, G. panamensis, B. rosademonte, and D. croatii showing the highest effect. Ten extracts (3.9-2000 µg/mouse) also showed 100% neutralizing ability against the defibrinating effect of venom, and nine prolonged the coagulation time induced by the venom. When the extracts were administered either before or after venom injection, the neutralization of the edema-forming effect was lower than 40% for all extracts, and none of them neutralized the defibrinating effect of venom. When they were administered in situ (sc at the same site 5 min after venom injection), the neutralization of edema increased for six extracts, reaching levels up to 64% for C. limon
Site-dependent reactivity of MoS2 nanoparticles in hydrodesulfurization of thiophene
N.S. and J.R.F. performed the experiments. N.S. analyzed the experimental data. S.R.
performed the theory. J.V.L. and M.M. planned and organized the studies. N.S. wrote the
first draft. J.V.L. wrote the final version. All authors contributed to the final version of the
manuscript.The catalytically active site for the removal of S from organosulfur compounds in catalytic
hydrodesulfurization has been attributed to a generic site at an S-vacancy on the edge of
MoS2 particles. However, steric constraints in adsorption and variations in S-coordination
means that not all S-vacancy sites should be considered equally active. Here, we use a
combination of atom-resolved scanning probe microscopy and density functional theory to
reveal how the generation of S-vacancies within MoS2 nanoparticles and the subsequent
adsorption of thiophene (C4H4S) depends strongly on the location on the edge of MoS2.
Thiophene adsorbs directly at open corner vacancy sites, however, we find that its adsorption
at S-vacancy sites away from the MoS2 particle corners leads to an activated and concerted
displacement of neighboring edge S. This mechanism allows the reactant to self-generate a
double CUS site that reduces steric effects in more constrained sites along the edge.The U.S. Department of Energy (DOEBasic Energy Sciences (BES)Office of Chemical SciencesCatalysis Science Program. DE‐FG02‐05ER15731National Energy Research Scientific Computing Center
(NERSC)Center for Nanoscale Materials (CNM)Argonne National
Laboratory (ANL)Department of Energy,
Office of Science, under contracts DE‐AC02‐06CH11357 and DE‐AC02‐05CH1123
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