Microcalorimetric investigation of the toxic action of Cr(VI) on the metabolism of Tetrahymena thermophila BF5 during growth

Tetrahymena thermophila BF5 produce heat by metabolism and movement. Using a TAM air isothermal microcalorimeter, the power-time curves of the metabolism of T thermophila BF5 during growth were obtained and the action on them by the addition of Cr(VI) were studied. The morphological change with Cr(VI) coexisted and biomass change during the process of T thermophila BF5 growth were studied by light microscope. Chromium has been regarded as an essential trace element for life. However, hexavalent chromium is a known carcinogen, mutagen, cytotoxicant and strong oxidizing agent. Cr(VI) of different concentration have different effects on T thermophila BF5 growth with the phenomenon of low dose stimulation (0-3 x 10(-5) mol L-1) and high dose inhibition (3 x 10(-5) to 2.4 x 10(-4) mol L-1). The relationship between the growth rate constant (k) and c is a typical U-shaped curve, which is a characteristic of hormesis. T thermophila BF5 cannot grow at all when the concentration of Cr(VI) is up to 2.4 x 10(-4) mol L-1. The microscopic observations agree well with the results obtained by means of microcalorimetry. And T thermophila BF5 had obviously morphological changes by the addition of Cr(VI). (c) 2006 Elsevier B.V. All rights reserved.

Changes in culture growth dynamics and cell size in a Scenedesmus quadricauda upon action of potassium dichromate

The effect of potassium dichromate in concentrations of 0.5 to 10 mg/l on a laboratory culture of Sc. quadricauda algae was studied in standard conditions. The total cell numbers decreased at potassium dichromate concentrations over 1 mg/l, and the proportion of living cells decreased at all studied concentrations. A positive correlation was found between changes in cell size and their numbers at toxin concentrations of 1 and 3 mg/l, and a negative correlation was found between the relative size and the cell numbers at 3 and 10 mg/l. This may be due to different intensity of growth inhibition and cell division under the influence of the toxin. The culture sensitivity to the toxin increased in autumn and decreased in the spring.

Recombinant protein of heptad-repeat HR212, a stable fusion inhibitor with potent anti-HIV action in vitro

HR212, a recombinant protein expressed in Escherichia coli, has been previously reported to inhibit HIV-1 membrane fusion at low nanomolar level. Here we report that HR212 is effective in blocking laboratory strain HIV-1IIIB entry and replication with EC50 values of 3.92±0.62 and 6.59±1.74 nM, respectively, and inhibiting infection by clinic isolate HIV-1KM018 with EC50 values of 44.44±10.20 nM, as well as suppressing HIV-1- induced cytopathic effect with an EC50 value of 3.04±1.20 nM. It also inhibited HIV-2ROD and HIV-2CBL-20 entry and replication in the μM range. Notably, HR212 was highly effective against T20-resistant strains with EC50 values ranging from 5.09 to 7.75 nM. Unlike T20, HR212 showed stability sufficient to inhibit syncytia formation in a time-of-addition assay, and was insensitive to proteinase K digestion. These results suggest that HR212 has great potential to be further developed as novel HIV-1 fusion inhibitor for treatment of HIV/ AIDS patients, particularly for those infected by T20-resistant variants.

Survivin表达在高LET射线诱导细胞凋亡中作用机理的初步研究；A Preliminary Study on Action Mechanisms of Survivin Expression in Cell Apoptosis Induced by High-LET Radiation

先前的研究表明,肿瘤细胞中survivin的高表达与细胞对高传能线密度(LET)射线的辐射抗性相关。研究了survivin表达在高LET射线诱导的细胞凋亡中的作用,发现抑制survivin表达对高LETC离子辐射诱导的Bcl-2和Bax表达没有明显的影响。在高LET射线辐照中,survivin可能通过抑制caspase-3和-9活性的途径,抑制了细胞凋亡。

Development of functionalized terbium fluorescent nanoparticles for antibody labeling and time-resolved fluoroimmunoassay application

Silica-based functionalized terbium fluorescent nanoparticles were prepared, characterized and developed as a fluorescence probe for antibody labeling and time-resolved fluoroimmunoassay. The nanoparticles were prepared in a water-in-oil (W/O) microemulsion containing a strongly fluorescent Tb3+ chelate. N,N.N-1,N-1-12,6-bis(3'-aminomethyl-1'-pyrazolyl)phenylpyridine] tetrakis(acetate)-Tb3+ (BPTA-Tb3+), Triton X-100, octanol, and cyclohexane by controlling copolymerization of tetraethyl orthosilicate (TEOS) and 3-[2-(2- aminoethylamino)-ethylamino]propyl-trimethoxysilane (AEPS) with ammonia water. The characterizations by transmission electron microscopy and fluorometric quantum methods show that the nanoparticles are spherical and uniform in size, 45 +/- 3 nm in diameter, strongly fluorescent with fluorescence yield of 10% and a long fluorescence lifetime of 2.0 ms. The amino groups directly introduced to the nanoparticle's surface by using AEPS in the preparation made the surface modification and bioconjugation of the nanoparticles easier. The nanoparticle-labeled anti-human alpha-fetoprotein antibody was prepared and used for time-resolved fluoroimmunoassay of (x-fetoprotein (AFP) in human serum samples. The assay response is linear from 0.10 ng ml(-1) to about 100 ng ml(-1) with the detection limit of 0.10 ng ml(-1). The coefficient variations (CVs) of the method are less than 9.0%. and the recoveries are in the range of 84-98% for human serum sample measurements. (C) 2004 Elsevier B.V. All rights reserved.

SiO2 nanoparticles as scatterers for random organic laser action in red fluorescent dye 4-(dicyanomethylene)-2-tert-butyl-6(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran doped polystyrene films

Random multimode lasers are achieved in 4-(dicyanomethylene)-2-tert-butyl-6(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB) doped polystyrene thin films by introducing silicon dioxide (SiO2) nanoparticles as scatterers. The devices emit a resonance multimode peak at a center wavelength of 640 nm with a mode linewidth less than 0.87 nm. The threshold excitation intensity is as low as 0.25 mJ pulse(-1) cm(-2). It can be seen that the microscopic random resonance cavities can be formed by multiple scattering of SiO2 nanoparticles.

[Ru(bpy)(2)(dcbpy)NHS] Labeling/Aptamer-Based Biosensor for the Detection of Lysozyme by Increasing Sensitivity with Gold Nanoparticle Amplification

A novel [Ru(bpy)(2) (dcbpy)NHS] labeling/aptamer-based biosensor combined with gold nanoparticle amplification for the determination of lysozyme with an electrochemiluminescence (ECL) method is presented. In this work, an aptamer, an ECL probe, gold nanoparticle amplification, and competition assay are the main protocols employed in ECL detection. With all the protocols used, an original biosensor coupled with an aptamer and [Ru(bpy)(2)(dcbpy)NHS] has been prepared. Its high selectivity and sensitivity are the main advantages over other traditional [Ru(bpy)(3)](2+) biosensors. The electrochemical impedance spectroscopy (EIS) and atomic force microscopy (AFM) characterization illustrate that this biosensor is fabricated successfully. Finally, the biosensor was applied to a displacement assay in different concentrations of lysozyme solution, and an ultrasensitive ECL signal was obtained. The ECL intensity decreased proportionally to the lysozyme concentration over the range 1.0 x 10-(13)-1.0 x 10(-8) mol L-1 with a detection limit of 1.0 x 10(-13) mol L-1.

The combined catalytic action of solid acids with nickel for the transformation of polypropylene into carbon nanotubes by pyrolysis

The effects of both organically modified montmorillonite (OMMT) and Ni2O3 on the carbonization of polypropylene (PP) during pyrolysis were investigated. The results from TEM and Raman spectroscopy showed that the carbonized products of PP were mainly multiwalled carbon nanotubes (MWNTs). Surprisingly, a combination of OMMT and Ni2O3 led to high-yield formation of MWNTs. X-ray powder diffraction (XRD) and GC-MS were used to investigate the mechanism of this combination for the high-yield formation of MWNTs from PP. Bronsted acid sites were created in degraded OMMT layers by thermal decomposition of the modifiers. The resultant carbenium ions play an important role in the carbonization of PP and the formation of MWNTs. The degradation of PP was induced by the presence of carbenium ions to form predominantly products with lower carbon numbers that could be easily catalyzed by the nickel catalyst for the growth of MWNTs. Furthermore, carbenium ions are active intermediates that promote the growth of MWNTs from the degradation products with higher carbon numbers through hydride-transfer reactions. The XRD measurements showed that Ni2O3 was reduced into metallic nickel (Ni) in situ to afford the active sites for the growth of MWNTs.

Europium ion labeling anti-HBs

A microsecond time-resolved laser fluorescence spectroscopic analysis set was developed, A chelate-cyclic anhydride of diethylenetrimin pentaacetic acid anhydride (DTPAA) was synthesized. An anti-HBs antibody was purified, A EU3+ -DTPAA-anti-HBs label was prepared by two step procedure. We described the optimal condtion with EU3+ as marker and DTPAA as chelate bounding to antibody molecule. Labeling parameters such as solvent pH, protein and chelate molar ratio, reaction time, separation method were discussed in detail.

STUDIES ON STRUCTURE OF EO/THF RANDOM COPOLYETHER(I) - NMR-STUDIES ON SOLUTION ACTION AND COMPLEX

The special action of TEO solution was investigated by 1D, 2D-NMR in CDCl3. For the present measurements, when the concentration of TEO was higher in CDCl3, the chemical shift difference (Delta delta) and the peak number of C-13 NMR spectrum were changed with increasing the solution concentration, At lower concentration(< 3% V/V ), the peaks will be closed together for -CH2O- resonance carbon and it is not the appearance of the narrowed, When temperature was changed, the Delta delta value was contrary to the solvent effect, So, the shifts of the resonance carbon in the NMR spectra indicated clearly that the complex formation for the system of CDCl3, and TEO molecular interaction were affected by the experiment temperature and the solution concentration.

Fluorescence spectroscopy studies on the action of rare earths with bovine serum albumin in multimolecular system

In this paper. the interaction of tripositive terbium ions (Tb3+) with bovine serum albumin (BSA) has been investigated in the presence of some alkaline earth metals and citric acid (Cit) by using fluorescence spectroscopy. The results show that Tb-31. BSA and Cit can form ternary complex BSA . Tb-2. Cit(4) in mu =0.1 mol/l NaCl. pH6.3 hexamethylenetetramine buffer. Other tare earths are able to compete for the same binding site in BSA with Tb3+-. The sequence of con,petition is Eu3+>Pr3+>Yb3+>Gd3+>La3+>Ca2+ and Mg2+ cannot replace Tb bound to BSA.

Product monitoring and quantitation of oligosaccharides composition in agar hydrolysates by precolumn labeling HPLC

Since the discovery of multiple bioactivities for agarobiose oligomers, a quantitative method has been in great need to monitor the agarobiose oligomers. This report demonstrates that agarobiose oligomers can be separated with high resolution in HPLC after introducing a-naphthylamine into compounds. Agarobiose oligomers ranged from biose to decaose were isolated by Sephadex column. HPLC analysis indicated that each oliomer could be quantified with good linearity and a low detection limit of 0.1-4 mug/ml. The chromatographic profiles of agaro-oligosaccharides with different hydrolysis modes (hydrochloride, citric acid, solid acid, and hydroxyl radical degradation) showed that agarobiose could be obtained more than 57.8% using solid acid mediated hydrolysis, while hydrochloride acid could degrade agar into a series of agaro-oligosaccharides from biose to decaose. The yield of oligosaccharides was low if hydrolyzed by citric acid. The Fenton degradation can increase the speed of hydrolysis, but the product was complex. (C) 2004 Elsevier B.V. All rights reserved.