Comparison of clonogenic assay with premature chromosome condensation assay in prediction of human cell radiosensitivity

Aim: To determine whether the number of non-rejoining G2-chromatid breaks can predict the radiosensitivity of human cell lines. Methods: Cell lines of human ovary carcinoma cells (HO8910), human hepatoma cells (HepG2) and liver cells (L02) were irradiated with a range of doses and assessed both of cell survival and non-rejoining G2-chromatid breaks at 24 h after irradiation. Cell survival was documented by a colony assay. Non-rejoining G2-chromatid breaks were measured by counting the number of non-rejoining G2 chromatid breaks at 24 h after irradiation, detected by the prematurely chromosome condensed (PCC) technique. Results: A linear-quadratic survival curve was observed in three cell lines, and HepG2 was the most sensitive to gamma-radiation. A dose-dependent linear increase was observed in radiation-induced non-rejoining G2-PCC breaks measured at 24 h after irradiation in all cell lines, and HepG2 was the most susceptible to induction of non-rejoining G2-PCC breaks. A close correlation was found between the clonogenic radiosensitivity and the radiation-induced non-rejoining G2-PCC breaks (r=0.923). Furthermore, survival-aberration correlations for two or more than two doses lever were also significant. Conclusion: The number of non-rejoining G2 PCC breaks holds considerable promise for predicting the radiosensitivity of normal and tumor cells when two or more than two doses lever is tested.

重离子诱变技术选育碱性蛋白酶高产菌株；The Selection for High-yield Alkaline Protease Producing Strain by Heavy-ion Irradiation

从采集的土壤样品中分离筛选出一株碱性蛋白酶产生菌G-41,经16S rRNA分子鉴定为芽孢杆菌属菌株。该菌株在发酵培养基中能产生较高产量的胞外碱性蛋白酶(1.7×104U/mL)。以G-41为出发菌株,对其进行重离子辐照诱变处理,获得突变株G-41-68,将该突变株再次经重离子诱变,从大量突变株中筛选出碱性蛋白酶高产菌株15Gy-54,其酶活力达到6.22×104U/mL。与出发菌株相比较,突变株G-41-68和15Gy-54的酶活力分别提高了1.58倍和2.65倍。对突变株15Gy-54的发酵条件进行了优化研究,结果表明,该菌株的碱性蛋白酶活力得到进一步提高,达到7.18×104U/mL,其最适发酵条件为:培养基(g/100mL)为胰蛋白胨1、酵母膏0.5、乳糖5、Na2HPO4·12H2O0.4、KH2PO40.03、Na2CO30.1、MgSO40.0481(4×10-3mol/L)、pH8.0,培养温度41℃,振荡培养时间42-48h。实验结果表明,重离子辐照诱变技术是一种非常有效的微生物诱变育种新技术。

Ultrasensitive colorimetric detection of protein by aptamer - Au nanoparticles conjugates based on a dot-blot assay

A simple, rapid and ultrasensitive colorimetric detection of protein using aptamer-Au nanoparticles (AuNPs) conjugates based on a dot-blot array has been developed, which was combined with the unique optical properties of AuNPs, enabling the visual detection of protein within minutes without any instrument.

Sensitive, Label-Free Protein Assay Using 1-ethyl-3-methylimidazolium Tetrafluoroborate Supported Microchip Electrophoresis with Laser-Induced Fluorescence Detection

Based on the dimer-monomer equilibrium movement of the fluorescent dye Pyronin Y (PY), a rapid, simple, highly sensitive, label-free method for protein detection was developed by microchip electrophoresis with LIF detection. PY formed a nonfluorescent dimer induced by the premicellar aggregation of an anionic surfactant, SDS, however, the fluorescence intensity of the system increased dramatically when proteins such as BSA, bovine hemoglobin, cytochrome c, and trypsin were added to the solution due to the transition of dimer to fluorescent monomer. Furthermore, 1-ethyl-3-methylimidazolium tetrafluoroborate (EMImBF(4)) instead of PBS was applied as running buffers in microchip electrophoresis.

Selective, peroxidase substrate based "signal-on" colorimetric assay for the detection of chromium (VI)

Due to the potentially adverse effects of the chromium (VI) on the human health and also on the environment, the quantitative determination of Cr(VI) is of particular interest. This work herein reports a facile, selective and rapid colorimetric determination of Cr(VI) based on the peroxidase substrate-2,2'-azino-bis(3-ethylbenzo-thiazoline-6-sulfonic acid) diammonium salt (ABTS) as the color developing agent. ABTS, which was usually acted as peroxidase substrate for the enzyme linked immunosorbent assay, is used here for the first time to fabricate the "signal-on" colorimetric Assay for Cr(VI).

Uniform Colloidal Alkaline Earth Metal Fluoride Nanocrystals: Nonhydrolytic Synthesis and Luminescence Properties

In this paper, we present a facile and general synthetic route to high-quality alkaline earth metal fluoride (AEF(2), AE = Ca, Sr, Ba) nanocrystals and CaF2:Tb3+ nanocrystals based on the thermal decomposition of corresponding trifluoroacetate precursors in hot oleylamine. X-ray diffraction, transmission electron microscopy, thermogravimetric and differential thermal analysis, Fourier transform infrared spectra, photoluminescence spectra, and kinetic decays were employed to characterize the samples. The use of single-source precursors plays an important role in the formation of high-quality AEF(2) nanocrystals, and the formation process is demonstrated in detail.

Gold nanoparticle-based surface enhanced Raman scattering spectroscopic assay for the detection of protein-protein interactions

In the present work, a sensitive spectroscopic assay based on surface-enhanced Raman spectroscopy (SERS) using gold nanoparticles as substrates was developed for the rapid detection protein-protein interactions. Detection is achieved by specific binding biotin-modification antibodies with protein-stabilized 30 nm gold nanoparticles, followed by the attachment of avidin-modification Raman-active dyes. As a proof-of-principle experiment, a well-known biomolecular recognition system, IgG with protein A, was chosen to establish this new spectroscopic assay. Highly selective recognition of IgG down to 1 ng/ml in solution has been demonstrated.

Novel Hybrid Electrocatalyst with Enhanced Performance in Alkaline Media: Hollow Au/Pd Core/Shell Nanostructures with a Raspberry Surface

In this paper, a hollow Au/Pd core/shell nanostructure with a raspberry surface was developed for methanol, ethanol, and formic acid oxidation in alkaline media. The results showed that it possessed better electrocatalyst performance than hollow Au nanospheres or Pd nanoparticles. The nanostructure was fabricated via a two-step method. Hollow Au nanospheres were first synthesized by a galvanic replacement reaction, and then they were coated with a layer of Pd grains. Several characterizations such as transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS) were used to investigate the prepared nanostructures.

Microarray-based Raman spectroscopic assay for kinase inhibition by gold nanoparticle probes

In this paper, a microarray-based surface-enhanced Raman spectroscopic (SERS) assay for detection of kinase functionality and inhibition has been reported. Biotinylated anti-phosphoserinen antibodies mark the phosphorylation and inhibition events and gold nanoparticles are attached to the antibodies by standard avidin-biotin chemistry, followed by silver deposition for SERS signal enhancement. The avidin conjugated fluorescein is used as SERS probe. The alpha-catalytic subunit of cyclic adenosine 5'-monophosphate (cAMP) dependent protein kinase (PKA), its well known substrate, kemptide, and three inhibitors, H89, HA1077, and KN62 have been chosen here to establish the SERS assay. As expected, highly selective inhibition of PKA is demonstrated with the inhibitor H89 and the inhibition assay enable to detect kinase inhibition as well as derive IC50 (half maximal inhibitory concentration) plots.

A Simple, Universal Colorimetric Assay for Endonuclease/Methyltransferase Activity and Inhibition Based on an Enzyme-Responsive Nanoparticle System

An enzyme responsive nanoparticle system that uses a DNA-gold nanoparticle (AuNP) assembly as the substrate has been developed for the simple, sensitive, and universal monitoring of restriction endonucleases in real time. This new assay takes advantage of the palindromic recognition sequence of the restriction nucleases and the unique optical properties of AuNPs and is simpler than the procedure previously described by by Xu et al. (Angew. Chem. Int. Ed. Engl. 2007, 46, 3468-3470). Because it involves only one type of ssDNA modified AuNPs, this assay can be directed toward most of the endonucleases by simply changing the recognition sequence found within the linker DNA. In addition, the endonuclease activity could be quantitatively analyzed by the value of the reciprocal of hydrolysis half time (t(1/2)(-1). Furthermore, our new design could also be applied to the assay of methyltransferase activity since the methylation of DNA inhibits its cleavage by the corresponding restriction endonuclease, and thus, this new methodology can be easily adapted to high-throughput screening of methyltransferase inhibitors.

Aptamer-based label-free method for hemin recognition and DNA assay by capillary electrophoresis with chemiluminescence detection

An aptamer-based label-free approach to hemin recognition and DNA assay using capillary electrophoresis with chemiluminescence detection is introduced here. Two guanine-rich DNA aptamers were used as the recognition element and target DNA, respectively. In the presence of potassium ions, the two aptamers folded into the G-quartet structures, binding hemin with high specificity and affinity. Based on the G-quartet-hemin interactions, the ligand molecule was specifically recognized with a K (d)approximate to 73 nM, and the target DNA could be detected at 0.1 mu M. In phosphate buffer of pH 11.0, hemin catalyzed the H2O2-mediated oxidation of luminol to generate strong chemiluminescence signal; thus the target molecule itself served as an indicator for the molecule-aptamer interaction, which made the labeling and/or modification of aptamers or target molecules unnecessary. This label-free method for molecular recognition and DNA detection is therefore simple, easy, and effective.