Direct electrochemistry of horseradish peroxidase immobilized in a chitosan-[C4mim][BF4] film: determination of electrode kinetic parameters

The direct electrochemistry of a HRP-chi-[C(4)mim][BF(4)] film (where HRP = horseradish peroxidase, chi = chitosan, and [C(4)mim][BF(4)] = the room temperature ionic liquid (RTIL) 1-butyl-3-methylimidazolium tetrafluoroborate) has been studied by cyclic voltammetry on a glassy carbon electrode. The mechanism for the electrochemical reaction of HRP is suggested to be EC for the reduction, and CE for the following re-oxidation, as the oxidative peak potential remained approximately unchanged across the scan rate range. The half wave potential of HRP reduction was found to be pH dependent, suggesting that a concomitant proton and electron transfer is occurring. Using theoretical simulations of the experimentally obtained peak positions, the standard electron transfer rate constant, k(0), was found to be 98 (+/-16) s(-1) at 295 K in pH 7 phosphate buffer solution, which is very close to the value reported in the absence of ionic liquid. This suggests that the ionic liquid used here in the HRP-chi-[C(4)mim][BF(4)]/GC electrode does not enhance the rate of electron transfer. k(0) was found to increase systematically with increasing temperature and followed a linear Arrhenius relation, giving an activation energy of 14.20 kJ mol(-1). The electrode kinetics and activation energies obtained are identical to those reported for HRP films in aqueous media. This leads us to question if the use of RTIL films provide any unique benefits for enzyme/protein voltammetry. Rather the films may likely contain aqueous zones in which the enzymes are located and undergo electron transfer.     

Sarcoplasmic reticulum calcium ATPase is inhibited by organic vanadium coordination compounds: pyridine-2,6-dicarboxylatodioxovanadium(V), BMOV, and an amavadine analogue

The general affinity of the sarcoplasmic reticulum (SR) Ca (2+)-ATPase was examined for three different classes of vanadium coordination complexes including a vanadium(V) compound, pyridine-2,6-dicarboxylatodioxovanadium(V) (PDC-V(V)), and two vanadium(IV) compounds, bis(maltolato)oxovanadium(IV) (BMOV), and an analogue of amavadine, bis( N-hydroxylamidoiminodiacetato)vanadium(IV) (HAIDA-V(IV)). The ability of vanadate to act either as a phosphate analogue or as a transition-state analogue with enzymes' catalysis phosphoryl group transfer suggests that vanadium coordination compounds may reveal mechanistic preferences in these classes of enzymes. Two of these compounds investigated, PDC-V(V) and BMOV, were hydrolytically and oxidatively reactive at neutral pH, and one, HAIDA-V(IV), does not hydrolyze, oxidize, or otherwise decompose to a measurable extent during the enzyme assay. The SR Ca (2+)-ATPase was inhibited by all three of these complexes. The relative order of inhibition was PDC-V(V) > BMOV > vanadate > HAIDA-V(IV), and the IC 50 values were 25, 40, 80, and 325 microM, respectively. Because the observed inhibition is more potent for PDC-V(V) and BMOV than that of oxovanadates, the inhibition cannot be explained by oxovanadate formation during enzyme assays. Furthermore, the hydrolytically and redox stable amavadine analogue HAIDA-V(IV) inhibited the Ca (2+)-ATPase less than oxovanadates. To gauge the importance of the lipid environment, studies of oxidized BMOV in microemulsions were performed and showed that this system remained in the aqueous pool even though PDC-V(V) is able to penetrate lipid interfaces. These findings suggest that the hydrolytic properties of these complexes may be important in the inhibition of the calcium pump. Our results show that two simple coordination complexes with known insulin enhancing effects can invoke a response in calcium homeostasis and the regulation of muscle contraction through the SR Ca (2+)-ATPase.     

Interaction of dipicolinatodioxovanadium(V) with polyatomic cations and surfaces in reverse micelles

In confined media such as reverse micelles, molecular probes frequently reside at and interact strongly with the interface. If the interface is charged, it is often difficult to separate effects arising from interactions with the charged species from the effect of the interfacial environment. With reverse micelles as a model system, the work reported here explores the interaction of the charged surfactant headgroups at a self-assembled interface with the dipicolinatodioxovanadium(V) coordination complex. The vanadium complex studied in these experiments serves as an excellent probe to investigate how charged metal complexes interact with lipid interfaces. For comparison, measurements were also carried out probing the interaction of the vanadium complex with a model cationic headgroup, tetramethylammonium bromide. The impact of the environment is gauged by changes in the 51V chemical shift, longitudinal relaxation times, and 1H NMR pulsed field gradient measurements. These measurements suggest that while interface component parts, as modeled by the dispersed systems, interact with the vanadium complex, the interfacial environment perturbs the complex substantially more strongly than the sum of the components alone. Coulomb attraction dominates the interaction in all systems probed and surprisingly orients the hydrophobic portion into the bulk water.     

Cytotoxicity of syringin and 4-methoxycinnamyl alcohol isolated from Foeniculum vulgare on selected human cell lines

This study was carried out to determine the cytotoxic effect of seven plant extracts and the isolated compounds – syringin and 4-methoxycinnamyl alcohol – on cancerous and non-cancerous cells. The ethanol extract of Foeniculum vulgare was found to exhibit the most significant toxicity with an IC₅₀ value of 19.97 μg/mL on HeLa cells. Bioassay-guided fractionation led to the isolation of two compounds, syringin (1) and 4-methoxycinnamyl alcohol (2). Both compounds showed toxicity against MCF-7, HeLa and DU145 cancer cell line. The results showed that compound 2 showed high toxicity against all the cancer cell lines with IC₅₀ values of 14.24, 7.82 and 22.10 μg/mL, respectively. 4-Methoxycinnamyl alcohol also showed no apoptotic effect in cell cycle analysis after 48 h at a concentration of 10 μg/mL. However, DNA fragmentation study revealed that necrosis took place at a concentration of 10 μg/mL after 48 h exposure.     

Soft C—H⃛O hydrogen bonds in methyl 2,4‐di­nitro­benzene­sulfenate: sheets built from R22(10) and R66(42) rings

Molecules of the title compound, C₇H₆N₂O₅S, are linked into sheets containing R₂²(10) and R₆⁶(42) rings by C—H?O hydrogen bonds [C?O 3.405 (3) and 3.511 (2) Å; C—H?O 159 and 169°], in which both acceptors are in the same nitro group. Comparisons are made with the hydrogen bonding in other nitro­benzene­sulfenate esters.     

汉高新一代专利芯片粘接剂:流控芯片粘接技术智能控制胶层倒角(英文)

为了简化存储器等更多应用的芯片堆叠,传统的芯片粘接剂正逐步被薄膜型的芯片粘接所取代,原因在于芯片堆叠设计难以使用传统的膏状材料。但现在,Self-Filleting材料可能标志着芯片粘接剂再度成为寻求低廉成本以及在不牺牲性能的情况下,最大限度提高现有资本生命周期的公司所选择的材料。对于多数应用来说,Self-Filleting材料的确取得了突破性的进步。     

Assessing ion-exchange properties and purity of lipophilic electrolytes by potentiometry and spectrophotometry

Many ionic salts synthesized using metathesis are often found to contain significant amounts of impurities, despite careful control of the weighing of starting materials. In this work, a potentiometric method is devised to monitor ion-exchange properties (or ‘purity’) of an organic solvent containing a lipophilic electrolyte. Its permselective behaviour is monitored by treating the solvent as a liquid membrane and contacting it with two aqueous solutions with different electrolyte activities. This electrolyte mismatch results in a drastic potential change when excess lipophilic cation-exchanger is titrated with anion-exchanger, altering the membrane from being cation to anion responsive. Here, the cation-exchanger potassium tetrakis(4-chlorophenyl)borate (KTpClPB) dissolved in nitrobenzene was titrated with tetradodecylammonium chloride (TDDACl), in contact with Ag/AgCl electrodes placed in aqueous 1 M and 10^?2 M KCl, respectively. The predicted potential change of ?214 mV was observed at the equivalence point, forming the inert lipophilic electrolyte ETH 500, in a very small concentration range of added anion-exchanger (0.8% for ±10 mV), suggesting good precision. The approach was confirmed by monitoring absorbance and fluorescence intensity changes of the chromoionophore Nile Blue. This method may be applied for the synthesis of a range of highly lipophilic salts for which established metathesis protocols are not suitable.     

When is water not water? Exploring water confined in large reverse micelles using a highly charged inorganic molecular probe

The interior water pool of aerosol OT (AOT) reverse micelles tends toward bulk water properties as the micelle size increases. Thus, deviations from bulk water behavior in large reverse micelles are less expected than in small reverse micelles. Probing the interior water pool of AOT reverse micelles with a highly charged decavanadate (V(10)) oligomer using (51)V NMR spectroscopy shows distinct changes in solute environment. For example, when an acidic stock solution of protonated V(10) is placed in a reverse micelle, the (51)V chemical shifts show that the V(10) is deprotonated consistent with a decreased proton concentration in the intramicellar water pool. Results indicate that a proton gradient exists inside the reverse micelles, leaving the interior neutral while the interfacial region is acidic.