Disturbance of firefly luciferase-based bioassays by different aluminum species

Luciferase-dependent assays, important for biochemical analyses of cytotoxicity and reporter genes, may be perturbed by compounds interfering with the luciferase reaction. We analyzed the impact of different aluminum (Al) species on a luciferase-based assay for determination of cellular adenosine triphosphate. Al⁰ nanoparticles (Al⁰–NPs) but not Al₂O₃–NPs decreased luminescence, correlated to high absorbance of Al⁰–NPs. By contrast, Al ions increased the luminescent signal. Data demonstrate that luciferase-dependent assays can be reciprocally disturbed by Al–NPs or Al ions in a specific manner, depending on the particular Al species. Careful interpretation of data from such experiments is essential in order to obtain conclusive results.     

Dmrt1 polymorphism covaries with sex‐determination patterns in Rana temporaria

Patterns of sex‐chromosome differentiation and gonadal development have been shown to vary among populations of Rana temporaria along a latitudinal transect in Sweden. Frogs from the northern‐boreal population of Ammarnäs displayed well‐differentiated X and Y haplotypes, early gonadal differentiation, and a perfect match between phenotypic and genotypic sex. In contrast, no differentiated Y haplotypes could be detected in the southern population of Tvedöra, where juveniles furthermore showed delayed gonadal differentiation. Here, we show that Dmrt1, a gene that plays a key role in sex determination and sexual development across all metazoans, displays significant sex differentiation in Tvedöra, with a Y‐specific haplotype distinct from Ammarnäs. The differential segment is not only much shorter in Tvedöra than in Ammarnäs, it is also less differentiated and associates with both delayed gonadal differentiation and imperfect match between phenotypic and genotypic sex. Whereas Tvedöra juveniles with a local Y haplotype tend to ultimately develop as males, those without it may nevertheless become functional XX males, but with strongly female‐biased progeny. Our findings suggest that the variance in patterns of sex determination documented in common frogs might result from a genetic polymorphism within a small genomic region that contains Dmrt1. They also substantiate the view that recurrent convergences of sex determination toward a limited set of chromosome pairs may result from the co‐option of small genomic regions that harbor key genes from the sex‐determination pathway.     

木薯离体培养与快速繁殖

选取3个木薯品种的腋芽作为外植体,分别接种于MS基本培养基上进行离体培养及快速繁殖。结果表明, 6-BA不同浓度对木薯品种不定芽诱导效果不一,在MS+6-BA 0.5~1.0mg/L中,3个品种均可诱导产生幼芽;在MS+6-BA 3.0mg/L中,3个品种的幼芽诱导率高达100%;MS+6-BA 3.0mg/L+NAA 0.1mg/L对继代效果较好;MS+NAA 0.1mg/L对生根效果最佳。     

Flow‐injection chemiluminescence method for the determination of chloramphenicol based on luminol–sodium periodate order‐transform second‐chemiluminescence reaction

A new chemiluminescence (CL) reaction was observed when chloramphenicol solution was injected into the mixture after the end of the reaction of alkaline luminol and sodium periodate or sodium periodate was injected into the reaction mixture of chloramphenicol and alkaline luminol. This reaction is described as an order‐transform second‐chemiluminescence (OTSCL) reaction. The OTSCL method combined with a flow‐injection technique was applied to the determination of chloramphenicol. The optimum conditions for the order‐transform second‐chemiluminescence emission were investigated. A mechanism for OTSCL has been proposed on the basis of the chemiluminescence kinetic characteristics, the UV‐visible spectra and the chemiluminescent spectra. Under optimal experimental conditions, the CL response is proportional to the concentration of chloramphenicol over the range 5.0 × 10^?7–5.0 × 10^?5 mol/L with a correlation coefficient of 0.9969 and a detection limit of 6.0 × 10^?8 mol/L (3σ). The relative standard deviation (RSD) for 11 repeated determinations of 5.0 × 10^?6 mol/L chloramphenicol is 1.7%. The method has been applied to the determination of chloramphenicol in pharmaceutical samples with satisfactory results. Copyright © 2011 John Wiley & Sons, Ltd.     

Determination of the Absolute P-Configuration of a Phthalidyl-Phosphonate Thymidine-Thymidine Dimer

Abstract

Phthalidyl modified oligonucleotide thymidine-thymidine dimer building blocks were synthesized via the H-phosphonate-method. The compounds which are diastereomeric at the phosphorus atom were separated by chromatography and the absolute configuration at the phosphorus atoms was determined using ROE-experiments using the corresponding methyl-phosphonates.     

ESEEM and Mössbauer studies of the ferriheme model compound bis(3-aminopyrazole)tetraphenylporphyrinatoiron(III) chloride, [TPPFe(NH2PzH)2]Cl

A model heme complex, bis(3-aminopyrazole)tetraphenylporphinatoiron(III) chloride, [TPPFe (NH₂PzH)₂]Cl, for which the EPR g-values lead to a rhombicity V/Δ=1.2 if g _zz is the largest g-value, have been investigated by electron spin echo envelope modulation (ESEEM) and Mössbauer spectroscopies. The ESEEM studies focus on the proton sum frequency peaks at near twice the proton Larmor frequency. Analysis of the distant proton peak (mainly due to the pyrrole-H) at exactly twice the proton Larmor frequency shows conclusively that g _zz is aligned along the normal to the porphyrin plane, and thus the electron configuration is (d _xy )²(d _xz ,d _yz )³, with g _zz >g _yy >g _xx . This system is thus another violation to Taylor's "proper axis system" rule. The near proton (the α-H and N-H of the axial ligands) peaks provide distance information for those protons from the metal. Magnetic Mössbauer studies of the same complex confirm the (d _xy )²(d _xz ,d _yz )³ ground state and indicate that, as is the case for cytochrome P450_cam, A _xx is the largest magnitude A-value, and is negative in sign. Other low-spin iron(III) porphyrinates also have A _xx of negative sign, but usually the magnitude is only about half that of A _zz , which is always positive in sign.     

Recent advances in analytical procedures for the detection of diarrhetic phycotoxins: a review

Okadaic acid and dinophysistoxins are produced by some marine unicellular algae from the plankton and also benthic microalgae and may accumulate in shellfish. These phycotoxins are involved in a gastrointestinal syndrome called diarrhetic shellfish poisoning (DSP), which occurs in humans after consumption of bivalve molluscs. Thousands cases of human poisonings in Europe were caused by consumption of toxic shellfish during the past decade. The rapid detection and the reliable determination of the main phycotoxins implicated in DSP are a major concern for governmental institutions in charge of the sanitary control of seafood safety. Analytical procedures for the detection and determination of DSP toxins can be classified as: bioassays, biochemical methods including immunoassays, or physicochemical methods. Although a large number of methods have been developed, none have been officially validated. A complete panel of tools for DSP toxin analysis should include screening, investigation, and confirmation methods. This paper presents a compilation of recent developments and optimisations of these methods. This revised version was published online in June 2006 with corrections to the Cover Date.     

On the challenges of detecting whole Staphylococcus aureus cells with biosensors

Due to the increasing number of nosocomial infections and multidrug‐resistant bacterial strains, Staphylococcus aureus is now a major worldwide concern. Rapid detection and characterization of this bacterium has become an important issue for biomedical applications. Biosensors are increasingly appearing as low‐cost, easy‐to‐operate and fast alternatives for rapid detection. In this review, we will introduce the main characteristics of S. aureus and will focus on the interest of biosensors for a faster detection of whole S. aureus cells. In particular, we will review the most promising strategies in the choice of ligand for the design of selective and efficient biosensors. Their specific characteristics as well as their advantages and/or disadvantages will also be commented.