In this work, a convenient and dual-signal readout optical sensing platform for the sensitively and selectively determination of beta-glucosidase (β-Glu) activity was reported using protein-inorganic hybrid nanoflowers [BSA-Cu3(PO4)2·3H2O] possessing peroxidase-mimicking activity. The nanoflowers (NFs) were facilely synthesized through a self-assembled synthesis strategy at room temperature. The as-prepared NFs could catalytically convert the colorless and non-fluorescent Amplex Red into colored and highly fluorescent resorufin in the presence of hydrogen peroxide via electron transfer process. β-Glu could hydrolyze cyanogenic glycoside, using amygdalin (Amy) as a model, into cyanide ions (CN?), which can subsequently efficiently suppress the catalytic activity of NFs, accompanied with the fluorescence decrease and the color fading. The concentration of CN? was controlled by β-Glu-triggered enzymatic reaction of Amy. Thus, a sensing system was established for fluorescent and visual determination of β-Glu activity. Under the optimum conditions, the present fluorescent and visual bimodal sensing platform exhibited good sensitivity for β-Glu activity assay with a detection limit of 0.33 U·L?1. The sensing platform was further applied to determinate β-Glu in real samples and satisfactory results were attained. Additionally, the optical sensing system can potentially be a promising candidate for β-Glu inhibitors screening.
These last decades, it has been widely assumed that 18-crown-6-ether (CE) plays a spectator role during the chemical processes occurring in isolated host-guest complexes between peptides or proteins and CE after activation in mass spectrometers. Our present experimental and theoretical results challenge this hypothesis by showing that CE can abstract a proton or a protonated molecule from protonated peptides after activation by collisions in argon or electron capture/transfer. Furthermore, thanks to comparison between experimental and calculated values of collision cross-sections, we demonstrate that CE can change binding site after electron transfer. We also propose detailed mechanisms for these processes. 相似文献
The porosity of 1‐hexanethiol‐functionalised gold nanoparticle films was assessed and utilised as chemiresistor sensors. Electrochemical capacitance measurements showed that the accessibility of electrolytes of different ionic strengths into the pores depended on the thickness of the electric double layer formed. A large variation in capacitance was measured in 0.01–1000 mM NaClO4, implying a wide pore size distribution. The change in morphology of the nanoparticle films upon storage in air, water and ethanol for two weeks was investigated. There was a significant decrease in the electrochemical capacitance at high electrolyte concentrations for the ethanol‐stored films compared to the freshly‐prepared films suggesting a decrease in the number of small pores of radii in the range of 0.3–3 nm. This was further supported by optical topographical measurements where a decrease in the thickness of ethanol‐stored films was observed relative to the freshly‐prepared films. The porous nature of the nanoparticle films was found to have an effect on the chemical sensing behaviour. When used as chemiresistor sensors, for the detection of heptane in water, the ethanol‐stored films provided larger resistance changes and longer response times. This suggests that the more densely packed ethanol‐stored films provided more sites that enabled film swelling, and that diffusion of the analyte occurred through the narrower water‐filled pores. This demonstrates the effect of different storage conditions on film morphology and subsequently sensor response. 相似文献
In the field of FTIR spectroscopy, the far infrared (FIR) spectral region has been so far less investigated than the mid-infrared
(MIR), even though it presents great advantages in the characterization of those inorganic compounds, which are inactive in
the MIR, such as some art pigments, corrosion products, etc. Furthermore, FIR spectroscopy is complementary to Raman spectroscopy
if the fluorescence effects caused by the latter analytical technique are considered. In this paper, ATR in the FIR region
is proposed as an alternative method to transmission for the analyses of pigments. This methodology was selected in order
to reduce the sample amount needed for analysis, which is a must when examining cultural heritage materials. A selection of
pigments have been analyzed in both ATR and transmission mode, and the resulting spectra were compared with each other. To
better perform this comparison, an evaluation of the possible effect induced by the thermal treatment needed for the preparation
of the polyethylene pellets on the transmission spectra of the samples has been carried out. Therefore, pigments have been
analyzed in ATR mode before and after heating them at the same temperature employed for the polyethylene pellet preparation.
The results showed that while the heating treatment causes only small changes in the intensity of some bands, the ATR spectra
were characterized by differences in both intensity and band shifts towards lower frequencies if compared with those recorded
in transmission mode. All pigments' transmission and ATR spectra are presented and discussed, and the ATR method was validated
on a real case study.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
Three major hypotheses have been proposed to explain why dinoflagellate bioluminescence deters copepod grazing: startle response, aposematic warning, and burglar alarm. These hypotheses propose dinoflagellate bioluminescence (A) startles predatory copepods, (B) warns potential predators of toxicity, and (C) draws the attention of higher order visual predators to the copepod's location. While the burglar alarm is the most commonly accepted hypothesis, it requires a high concentration of bioluminescent dinoflagellates to be effective, meaning the bioluminescence selective advantage at lower, more commonly observed, dinoflagellate concentrations may result from another function (e.g. startle response or aposematic warning). Therefore, a series of experiments was conducted to evaluate copepod grazing (Acartia tonsa) on bioluminescent dinoflagellates (during bioluminescent and nonbioluminescent phases, corresponding to night and day, respectively) at different concentrations (10, 1000, and 3000 cells mL?1), on toxic (Pyrodinium bahamense var. bahamense) and nontoxic (Lingulodinium polyedrum) bioluminescent dinoflagellates, and in the presence of nonluminescent diatoms (Thalassiosira eccentrica). Changes in copepod ingestion rates, clearance rates, and feeding preferences as a result of these experimental factors, particularly during the mixed trails with nonluminescent diatoms, indicate there is a concentration threshold at which the burglar alarm becomes effective and below which dinoflagellate bioluminescence functions as an aposematic warning. 相似文献
The enzymatic kinetic resolution of α-hydroxysilanes where the silicon bears a variety of substituents has been explored. Reactions were performed on various α-hydroxysilanes with several commercially available enzymes, solvents, acetylation reagents, and temperatures. The resulting optically active α-hydroxysilanes and their corresponding acetates were obtained in varying yields and ees. 相似文献
Abstract In 1968 Zen and coworkers reported that thep-tolylsulfonyl group could be removed from carbohydrate systems by photochemical reaction (eq 1).1 Since then other investigators have used this deprotection process in carbohydrate synthesis.2-10 Mechanistic studies11-16 have shown that tosylate photolysis is promoted by compounds (e.g., triethylamine) that donate an electron to an excitedp-toluenesulfonate to generate a radical anion (1). This intermediate then fragments to form the anion of the deprotected sugar (Scheme 1). Since generating a radical anion is the central element in this photochemical process, structural changes that impact radical anion formation should influence the reaction. Replacing the p - tolylsulfonyl group with the pentafluorophenylsulfonyl group generates a more stable radical anion (2) because the electronegative fluorine atoms can help stabilize the negative charge. Since we have a continuing interest in the photochemistry of sulfonic acid esters, we synthesized the pentafluorobenzenesulfonates (pentaflates) 3-6 and studied their photochemistry under electron transfer conditions. 相似文献
Let G be a finite p-group, where p is a prime number, and a ∈ G. Denote by Cl(a) = {gag−1| g ∈ G} the conjugacy class of a in G. Assume that |Cl(a)| = pn. Then Cl(a) Cl(a−1) = {xy | x ∈ Cl(a), y ∈ Cl(a−1)} is the union of at least n(p − 1) + 1 distinct conjugacy classes of G.
Received: 16 December 2004 相似文献