This paper reports on how the surface chemistry of boron-doped nanocrystalline diamond (BDD) thin-film electrodes (H vs O) affects the wettability and electrochemical properties in two room-temperature ionic liquids (RTILs): [BMIM][PF6] and [HMIM][PF6]. Comparative measurements were made in 0.5 mol L–1 H2SO4. The BDD electrodes were modified by microwave or radio-frequency (RF) plasma treatment in H2 (H-BDD), Ar (Ar-BDD), or O2 (O-BDD). These modifications produced low-, medium-, and high-oxygen surface coverages. Atomic O/C ratios, as determined by X-ray photoelectron spectroscopy (XPS), were 0.01 for H-BDD, 0.08 for Ar-BDD, and 0.17 for O-BDD. The static contact angle of ultrapure water on the modified electrodes decreased from 110° (H-BDD) to 41° (O-BDD) with increasing surface oxygen coverage, as expected as the surface becomes more hydrophilic. Interestingly, the opposite trend was seen for both RTILs as the contact angle increased from 20° (H-BDD) to 50° (O-BDD) with increasing surface oxygen coverage. The cyclic voltammetric background current and potential-dependent capacitance in both RTILs were largest for BDD electrodes with the lowest O/C ratio (H-BDD) and smallest contact angle. Slightly larger voltammetric background currents and capacitance were observed in [HMIM][PF6] than in [BMIM][PF6]. Capacitance values ranged from 8 to 16 μF cm–2 over the potential range for H-BDD and from 4 to 6 μF cm–2 for O-BDD. The opposite trend was observed in H2SO4 as the voltammetric background current and capacitance were largest for BDD electrodes with the highest O/C ratio (O-BDD) and smallest contact angle. In summary, reducing the surface oxygen on BDD electrodes increases the wettability to two RTILs and this increases the voltammetric background current and capacitance.
A thermally stable lipase (EC 3.1.1.3.) was first identified in rice (Oryza sativa) bran, and the enzyme was purified to homogeneity using octyl-Sepharose chromatography. The enzyme was purified to 7.6-fold with the final specific activity of 0.38 mol min Ϫ1 mg Ϫ1 at 80°C using [9, H]triolein as a substrate. The purified enzyme was found to be a glycoprotein of 9.4 kD. Enzyme showed a maximum activity at 80°C and at pH 11.0. The protein was biologically active and retained most of its secondary structure even at 90°C as judged by the enzymatic assays and far-ultraviolet circular dichroism spectroscopy, respectively. Differential scanning calorimetric studies indicated that the transition temperature was 76°C and enthalpy 1.3 ϫ 10 5 Calorie mol Ϫ1 at this temperature. The purified lipase also exhibited phospholipase A 2 activity. Colocalization of both the hydrolytic activities in reverse-phase high-performance liquid chromatography and isoelectric focusing showed that the dual activity was associated with a single protein. Further, a direct interaction between both the substrates and the purified protein was demonstrated by photoaffinity labeling, using chemically synthesized analogs of triolein and phosphatidylcholine (PC). Apparent K m for triolein (6.71 mm) was higher than that for PC (1.02 mm). The enzyme preferentially hydrolyzed the sn-2 position of PC, whereas it apparently exhibited no positional specificity toward triacylglycerol. Diisopropyl fluorophosphate inhibited both lipase and phospholipase activities of the purified enzyme. This enzyme is a new member from plants in the family of lipases capable of hydrolyzing phospholipids.Lipases (EC 3.1.1.3.) are versatile enzymes that catalyze the hydrolysis of ester linkages, primarily in neutral lipids such as triglycerides. They hydrolyze the acyl chains either at primary (Ransac et al., 1990; Rogalska et al., 1993) or secondary positions (Candida antarctica lipase, Geotrichum candidum lipase B, lipase from Vernonia anthelmintica, etc.). However, a few lipases do not show any positional specificity (Rollof et al., 1987;Hiromasa et al., 1998). Plant lipases hydrolyze triacylglycerols at much lower rates (usually Ͻ0.5 mol min Ϫ1 mg Ϫ1 ) as compared with animal or microbial lipases. All the members of the lipase gene family have a conserved Ser, which is the nucleophile essential for catalysis. The active site triad of lipases consisting of Ser-His-Asp/Glu is reminiscent of the Ser proteases (Blow, 1990). In addition to triglycerides, lipases are also known to degrade Tween and water-soluble and insoluble esters. There are reports of a few animal and microbial lipases that hydrolyze phospholipids (Durand et al., 1978;Fauvel et al., 1981;Jensen et al., 1982; van Oort et al., 1989; Thirstrup et al., 1994). Enzymatic activity of many lipases has been shown to be modulated by calcium (Rosenstein and Gotz, 2000), ricinoleic acid (Ory et al., 1962), and bile salts (Miled et al., 2000).In plants, the regulation, in some cases the location, and the exact physio...
Ag0 nanoparticles were synthesized by Lantana camara plant (weed) leave extract. Antibacterial activity of the as synthesized Ag0 nanoparticles was excellent against both Gram −ve and Gram +ve bacterial culture.
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