A facile approach to immobilize protein for biosensor: self-assembled supported bilayer lipid membranes on glassy carbon electrode

A kind of solid substrate, glassy carbon (GC) electrode. was selected to support self-assembled lipid layer membranes. On the surface of GC electrode. we made layers of dimyristoylphosphatidylcholine (DMPG, a kind of lipid). From electrochemical impedance experiments. we demonstrated that the lipid layers on the GC electrode were bilayer lipid membranes. We immobilized horseradish peroxidase (HRP) into the supported bilayer lipid membranes (s-BLM) to develop a kind of mediator-free biosensor for H2O2. The biosensor exhibited fine electrochemical response, stability and reproducibility due to the presence of the s-BLM. As a model of biological membrane, s-BLM could supply a biological environment for enzyme and maintain its activity. So s-BLM is an ideal choice to immobilize enzyme for constructing the mediator-free biosensor based on GC electrode. (C) 2001 Elsevier Science B.V. All rights reserved.

MAGNETIC-RESONANCE EXPERIMENTS ON UNDOPED AND DOPED POLY(PARA-PHENYLENE)

We investigated the electron paramagnetic resonance (EPR) spectra of undoped, FeCl3- and iodine-doped poly(para-phenylene) (PPP) prepared by the method of Kovacic. EPR measurements are used to characterize electronic states relevant for carrier transport in doped PPP. We found a novel dependence of room temperature linewidth (DELTAH(pp)) and spin density (N(spin)) on the dopant concentrations for iodine-doped PPP, namely, DELTAH(pp) first decreased and increased, and then decreased and increased again with increasing iodine concentration in the iodine-doped PPP. The corresponding value of N(spin) first increased and decreased, and then increased and decreased again with increasing iodine concentration in PPP. However, the changes in DELTAH(pp) and N(spin) with FeCl3 concentration in FeCl3-doped PPP differ from those of iodine-doped PPP. We explain the different EPR properties in FeCl3-doped and iodine-doped PPP.

In vitro iron enrichment experiments in the Prydz Bay, the Southern Ocean: A test of the iron hypothesis

In "high nitrate, low chlorophyll" (HNLC) ocean regions, iron has been typically regarded as the limiting factor for phytoplankton production. This "iron hypothesis" needs to be tested in various oceanic environments to understand the role of iron in marine biological and biogeochemical processes. In this paper, three in vitro iron enrichment experiments were performed in Prydz Bay and at the Polar Front north of the Ross Sea, to study the role of iron on phytoplankton production. At the Polar Front of Ross Sea, iron addition significantly (P < 0.05, Student's t-test) stimulated phytoplankton growth. In Prydz Bay, however, both the iron treatments and the controls showed rapid phytoplankton growth, and no significant effect (P > 0.05, Student's t-test) as a consequence of iron addition was observed. These results confirmed the limiting role of iron in the Ross Sea and indicated that iron was not the primary factor limiting phytoplankton growth in Prydz Bay. Because the light environment for phytoplankton was enhanced in experimental bottles, light was assumed to be responsible for the rapid growth of phytoplankton in all treatments and to be the limiting factor controlling field phytoplankton growth in Prydz Bay. During the incubation experiments, nutrient consumption ratios also changed with the physiological status and the growth phases of phytoplankton cells. When phytoplankton growth was stimulated by iron addition, N was the first and Si was the last nutrient which absorption enhanced. The Si/N and Si/P consumption ratios of phytoplankton in the stationary and decay phases were significantly higher than those of rapidly growing phytoplankton. These findings were helpful for studies of the marine ecosystem and biogeochemistry in Prydz Bay, and were also valuable for biogeochemical studies of carbon and nutrients in various marine environments.

注意在视觉刺激位置编码中的作用

There is extensive agreement that attention may play a role in spatial stimmlus coding (Lu & Proctor, 1995). Some authors investigated the effects of spatial attention on the spatial coding by using spatial cueing procedure and spatial Stroop task. The finding was that the stroop effects were modulated by spatial cueing. Three hypotheses including attentional shift account, referential coding account, and event integration account were used to explain the modulation of spatial cueing over the spatial Stroop effects. In these previous studies, on validly cued trials, cue and target not only appeared at the same location, but also in the same object, which resulted in both location and object cued. Consequently, the modulation of spatial attentional cueing over spatial Stroop effects was confounded with the role of object-based attention. In the third chapter of this dissertation, using a modification of double rectangles cueing procedure developed by Egly, Driver and Rafal (1994) and spatial Stroop task employed by Lupiáñez and Funes (2005), separate effects of spatial attention and object-based attention on the location code of visual stimuli were investigated. Across four experiments, the combined results showed that spatial Stroop effects were modulate by object-based attention, but not by location-based attention. This pattern of results could be well explained by event integration account, but not by attentional shift account and referential coding account. In the fourth chapter, on the basis of the prior chapter, whether the modulation of attentional cueing on location code occurred at the stage of perceptual identification or response choice was investigated. The findings were that object-based attention modulated spatial Stroop effects and did not modulate the Simon effects, whereas spatial attention did not modulate Stroop and Simon effects. This pattern of results partially replicated the outcome of the previous chapter. The previous studies generally argued that the conflicts of spatial Stroop task and Simon task respectively occurred at at the stage of perceptual identification and response choice. Therefore, it is likely to conclude that the modulation of attention over spatial Stroop effect was mediated by object-based attention, and this modulation occurred at the stage perceptual identification. Considering that the previous studies mostly investigated the effects of attention captured by abrupt onset on the spatial Stroop effects, few studies investigated the effects of attention captured by offset cue on the spatial Stroop effects. The aim of the fifth chapter was to investigate the role of attention induced by offset and abrupt onset cue in the spatial Stroop task. These results showed that attention elicited by offset cue or abrupt onset cue modulated the spatial Stroop effects, which reconciled with event integration account.