Organophosphorus poisoning caused by some pesticides and nerve agents is a life-threating condition that must be swiftly addressed to avoid casualties. Despite the availability of medical ...countermeasures, the clinically available compounds lack a broad spectrum, are not effective towards all organophosphorus toxins, and have poor pharmacokinetics properties to allow them crossing the blood-brain barrier, hampering cholinesterase reactivation at the central nervous system. In this work, we designed and synthesised novel isatin derivatives, linked to a pyridinium 4-oxime moiety by an alkyl chain with improved calculated properties, and tested their reactivation potency against paraoxon- and NEMP-inhibited acetylcholinesterase in comparison to the standard antidote pralidoxime. Our results showed that these compounds displayed comparable in vitro reactivation also pointed by the in silico studies, suggesting that they are promising compounds to tackle organophosphorus poisoning.
Radioactive ^{27}Mg (t_{1/2}=9.5 min) was implanted into GaN of different doping types at CERN's ISOLDE facility and its lattice site determined via β^{-} emission channeling. Following ...implantations between room temperature and 800 °C, the majority of ^{27}Mg occupies the substitutional Ga sites; however, below 350 °C significant fractions were also found on interstitial positions ∼0.6 Å from ideal octahedral sites. The interstitial fraction of Mg was correlated with the GaN doping character, being highest (up to 31%) in samples doped p type with 2×10^{19} cm^{-3} stable Mg during epilayer growth, and lowest in Si-doped n-GaN, thus giving direct evidence for the amphoteric character of Mg. Implanting above 350 °C converts interstitial ^{27}Mg to substitutional Ga sites, which allows estimating the activation energy for migration of interstitial Mg as between 1.3 and 2.0 eV.
We investigated the effects of eyestalk ablation and cheliped autotomy in inducing molting in Callinectes ornatus. The specimens in intermolt stage were divided into two size classes: 1 (30-50 mm) ...and 2 (51-70 mm) and were further divided into four experimental groups. In the CA group (Cheliped Autotomy, n=76), crabs were submitted to cheliped autotomy; in the UA group (Unilateral Ablation, n=66) and BA group (Bilateral Ablation, n=66) to unilateral and bilateral eyestalk ablation, respectively. The C group (Control, n=70) was used as control. The animals were individually kept in tanks interconnected to a recirculation system for 30 days. The highest frequency of premolt was recorded in the BA group (32%), followed by the CA group (16%). The premolt frequency of class 1 (28%) was significantly higher (p<0.05) than of class 2 (8%). The mean time until molt in the BA group was significantly lower (p <0.05) than other groups tested. The highest mortality rates were 55% and 25% in crabs from the BA and CA groups, respectively. The results indicate bilateral eyestalk ablation and cheliped autotomy are potentially capable of inducing molt in C. ornatus, but these techniques have limited efficiency for the commercial application of large-scale soft-shell crab.
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▶ We studied the resolution of racemic solketal (IPG) ester derivatives by lipases. ▶ IPG octanoate was found to be a better substrate than acetate counterpart. ▶ Among several lipases, Amano AK ...led to the best selectivities (E up to 200).
A study on the enantioselective hydrolysis of (R,S)-1,2-isopropylidene glycerol (4-hydroxymethyl-2,2-dimethyl-1,3-dioxolane, solketal) octanoate catalyzed by different lipases was carried out. Among them, Pseudomonas sp. lipase proved to be the most effective. It was shown that the ester bearing the longer octanoyl acyl chain is a more suitable substrate for this lipase compared to the acetate counterpart. By properly combining enzyme load, temperature and reaction time, either the (S)-alcohol or the remaining ester could be obtained in moderate to high selectivities. Ethyl acetate was found to be the best solvent for the kinetic resolutions effected by such lipase but our results show that toluene may prove useful.
Although the formation of transition metal-boron pairs is currently well established in silicon processing, the geometry of these complexes is still not completely understood. We investigated the ...lattice location of the transition metals manganese, iron, cobalt and nickel in n- and p+-type silicon by means of electron emission channeling. For manganese, iron and cobalt, we observed an increase of sites near the ideal tetrahedral interstitial position by changing the doping from n- to p+-type Si. Such increase was not observed for Ni. We ascribe this increase to the formation of pairs with boron, driven by Coulomb interactions, since the majority of iron, manganese and cobalt is positively charged in p+-type silicon while Ni is neutral. We propose that breathing mode relaxation around the boron ion within the pair causes the observed displacement from the ideal tetrahedral interstitial site. We discuss the application of the emission channeling technique in this system and, in particular, how it provides insight on the geometry of such pairs.
(±)-1,2-O-Isopropylidene-3,6-di-O-benzyl-myo-inositol is a relevant starting material in the synthesis of inositol phosphates and their analogs. In this study, we disclose our efforts toward an ...efficient methodology for the kinetic resolution of this compound by lipase B of Candida antarctica (Novozym 435). This reaction selectively affords L-(−)-1,2-O-isopropylidene-5-O-acetyl-3,6-di-O-benzyl-myo-inositol. From a conversion of 34% with EtOAc as an acylating agent, the use of vinyl acetate increased the yield to over 49%, while maintaining a very high ee (>99%). The combination of the latter reagent with TBME as a solvent accelerates the reaction.
Nine other cases. A successful reaction relying on substoichiometric tin (∼0.15
mol
equiv) is also reported.
A direct selective protection (O-benzylation) of two or more hydroxyl groups in polyols ...displaying diverse structural patterns was made possible by the establishment of conditions that enable an efficient turnover for the Bu
2Sn group, initially at the corresponding stannylene acetals (only ∼1.0
mol
equiv of Bu
2SnO was employed). It was also demonstrated that one might exert control over the number of protected groups, by means of appropriate tuning of reaction conditions. The feasibility of a substoichiometric (tin source) catalytic protocol was demonstrated as well.
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