Ultrasensitive Label-Free Resonance Rayleigh Scattering Aptasensor for Hg(2+) Using Hg(2+)-Triggered Exonuclease III-Assisted Target Recycling and Growth of G-Wires for Signal Amplification.

A novel signal-on and label-free resonance Rayleigh scattering (RRS) aptasensor was constructed for detection of Hg(2+) based on Hg(2+)-triggered Exonuclease III-assisted target recycling and growth of G-quadruplex nanowires (G-wires) for signal amplification. The hairpin DNA (H-DNA) was wisely designed with thymine-rich recognition termini and a G-quadruplex sequence in the loop and employed as a signal probe for specially recognizing trace Hg(2+) by a stable T-Hg(2+)-T structure, which automatically triggered Exonuclease III (Exo-III) digestion to recycle Hg(2+) and liberate the G-quadruplex sequence. The free G-quadruplex sequences were self-assembled into guanine nanowire (G-wire) superstructure in the presence of Mg(2+) and demonstrated by gel electrophoresis. The RRS intensity was dramatically amplified by the resultant G-wires, and the maximum RRS signal at 370 nm was linear with the logarithm of Hg(2+) concentration in the range of 50.0 pM to 500.0 nM (R = 0.9957). Selectivity experiments revealed that the as-prepared RRS sensor was specific for Hg(2+), even coexisting with high concentrations of other metal ions. This optical aptasensor was successfully applied to identify Hg(2+) in laboratory tap water and river water samples. With excellent sensitivity and selectivity, the proposed RRS aptasensor was potentially suitable for not only routine detection of Hg(2+) in environmental monitoring but also various target detection just by changing the recognition sequence of the H-DNA probe.

Low temperature inhibits root growth by reducing auxin accumulation via ARR1/12.

Plants exhibit reduced root growth when exposed to low temperature; however, how low temperature modulates root growth remains to be understood. Our study demonstrated that low temperature reduces both meristem size and cell number, repressing the division potential of meristematic cells by reducing auxin accumulation, possibly through the repressed expression of PIN1/3/7 and auxin biosynthesis-related genes, although the experiments with exogenous auxin application also suggest the involvement of other factor(s). In addition, we verified that ARABIDOPSIS RESPONSE REGULATOR 1 (ARR1) and ARR12 are involved in low temperature-mediated inhibition of root growth by showing that the roots of arr1-3 arr12-1 seedlings were less sensitive than wild-type roots to low temperature, in terms of changes in root length and meristem cell number. Furthermore, low temperature reduced the levels of PIN1/3 transcripts and the auxin level to a lesser extent in arr1-3 arr12-1 roots than in wild-type roots, suggesting that cytokinin signaling is involved in the low-temperature-mediated reduction of auxin accumulation. Taken together, our data suggest that low temperature inhibits root growth by reducing auxin accumulation via ARR1/12.

TIME FOR COFFEE controls root meristem size by changes in auxin accumulation in Arabidopsis.

Roots play important roles in plant survival and productivity as they not only anchor the plants in the soil but are also the primary organ for the uptake of nutrients from the outside. The growth and development of roots depend on the specification and maintenance of the root meristem. Here, we report a previously unknown role of TIME FOR COFFEE (TIC) in controlling root meristem size in Arabidopsis. The results showed that loss of function of TIC reduced root meristem length and cell number by decreasing the competence of meristematic cells to divide. This was due to the repressed expression of PIN genes for decreased acropetal auxin transport in tic-2, leading to low auxin accumulation in the roots responsible for reduced root meristem, which was verified by exogenous application of indole-3-acetic acid. Downregulated expression of PLETHORA1 (PLT1) and PLT2, key transcription factors in mediating the patterning of the root stem cell niche, was also assayed in tic-2. Similar results were obtained with tic-2 and wild-type plants at either dawn or dusk. We also suggested that the MYC2-mediated jasmonic acid signalling pathway may not be involved in the regulation of TIC in controlling the root meristem. Taken together, these results suggest that TIC functions in an auxin-PLTs loop for maintenance of post-embryonic root meristem.

Effects of Different Irradiation Treatments on Total Saponins Content of Sapindus mukorossi.

Sapindus mukorossi Gaertn is also known as Mu Huanzi, You Huanzi, soap tree, etc. The pericarp of Sapindus mukorossi contains many saponins, which is a type of natural non-ionic surfactant. Its extract has vigorous surface activity and biological activities such as bacteriostasis, oxidation resistance, and free radical scavenging. The Sapindus mukorossi extract is an environmentally friendly washing product that microorganisms can be rapidly decompose in nature without any environmental pollution.This study aims to investigate the effects of E-beam and Co60-γ irradiation on the total saponins content in the crude extract of the S mukorossi. The S mukorossi powder is irradiated with E-beam and Co60-γ ray at doses of 0, 4, 6, 8, 10, and 12 kGy for E-beam and 0, 50, 100, 150, and 200 Gy, respectively, for Co60-γ ray. The changes in the content of total saponins in the crude extract, total detergency, and the bacteriostatic abilities before and after the irradiation were analyzed. The results showed that the content of total saponins in samples irradiated by E-beam was significantly higher than that in non-irradiated samples. The saponins yield was the highest at a radiation dose of 6 kGy, and the detergency and bacteriostatic ability were also the strongest. After low-dose Co6-γ irradiation, the total saponins in the S mukorossi crude extract, and detergency and bacteriostatic ability had no apparent change. Conclusion: E-beam irradiation at a dose of 6 kGy can effectively improve the content of total saponins in the crude extract of S mukorossi powder. In addition, its effects on detergency and bacteriostatic abilities are relatively significant. The findings provide sufficient reference data for the further development of S mukorossi commodities.

A regenerative ratiometric electrochemical biosensor for selective detecting Hg²âº based on Y-shaped/hairpin DNA transformation.

Inspired by dual-signaling ratiometric mechanism which could reduce the influence of the environmental change, a novel, convenient, and reliable method for the detection of mercury ions (Hg(2+)) based on Y-shaped DNA (Y-DNA) was developed. Firstly, the Y-DNA was formed via the simple annealing way of using two different redox probes simultaneously, omitting the multiple operation steps on the electrode. The Y-DNA was immobilized on the gold electrode surface and then an obvious ferrocene (Fc) signal and a weak methylene blue (MB) signal were observed. Upon addition of Hg(2+), the Y-DNA structure was transformed to hairpin structure based on the formation of T-Hg(2+)-T complex. During the transformation, the redox MB gets close to and the redox Fc gets far away from the electrode surface, respectively. This special design allows a reliable Hg(2+) detection with a detection range from 1 nM to 5 µM and a low detection limit down to 0.094 nM. Furthermore, this biosensor exhibits good selectivity and repeatability, and can be easily regenerated by using L-cysteine. This study offers a simple and effective method for designing ratiometric biosensors for detecting other ions and biomolecules.

Fluorometric detection of mutant DNA oligonucleotide based on toehold strand displacement-driving target recycling strategy and exonuclease III-assisted suppression.

We describe here a fluorometric assay for sensitive detection of oligonucleotides, based on a target recycling amplification strategy driven by toehold-mediated strand displacement reaction and on exonuclease III (Exo Ш)-assisted fluorescence background suppression strategy. The network consists of a pair of partially complementary DNA hairpins (HP1 and HP2) with 3' overhang ends, between which the spontaneous hybridization is kinetically hindered by the stems. The target DNA is repeatedly used to trigger a recycling progress between the hairpins, generating numerous HP1-HP2 duplex complexes. Exo III was then employed to digest the double strand parts of the residual hairpins and the intermediate products. The fluorescent dye, SYBR Green I, binds to the double-strand DNA products and emits strong fluorescence to achieve sensitive detection of the target DNA with the detection limit of 5.34 pM. Moreover, this proposed strategy showed high discrimination efficiency towards target DNA against mismatched DNA and was successfully applied in the analysis of human serum sample.

Genetic polymorphism of 5 short tandem repeat loci in Hui population in Ningxia area / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To analyze the genetic polymorphism of 5 short tandem repeat(STR) loci in Hui population in Ningxia area.</p><p><b>METHODS</b>The genetic polymorphisms of five selected STR loci(D11S1984, D14S306, D14S617, D17S1290 and D19S433) in chromosomes 11, 14, 17 and 19 in 144 unrelated individuals in Hui population in Ningxia area were analyzed by PCR amplification, denaturing polyacrylamide gel electrophoresis(PAGE) and silver staining.</p><p><b>RESULTS</b>10, 8, 11, 13 and 8 alleles, 30, 25, 33, 40 and 23 genotypes of the 5 STR loci in Hui population in Ningxia were detected. The measured values of the heterozygosity of the 5 STR loci were 0.8413, 0.8033, 0.8331, 0.8369 and 0.7703; of the polymorphism information content were 0.8217, 0.7746, 0.8121, 0.8174 and 0.7332; of the discrimination power (DP) were 0.9516, 0.9257, 0.9611, 0.9660 and 0.9135. The calculated discrimination power was 0.9999995. The measured values of paternity exclusion were 0.7046, 0.6367, 0.6911, 0.7012 and 0.5801; the calculated paternity exclusion was 0.9958. The genotype distributions were in accordance with Hardy-Weinberg equilibrium.</p><p><b>CONCLUSION</b>The 5 STR loci have better polymorphism in Hui population in the Ningxia area, and thus could serve as useful markers for population genetics research and for individual identification and paternity test in forensic medicine.</p>

Application of homozygosity mapping to the fine mapping of the osteoporosis-pseudoglioma syndrome locus / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To evaluate the role of homozygosity mapping in the fine mapping of the genes responsible for the rare autosomal recessive diseases.</p><p><b>METHODS</b>Polymerase chain reaction-single sequence length polymorphism was used to genotype the family members from 8 families with osteoporosis-pseudoglioma syndrome(OPS) for 14 polymorphic loci within candidate region. The OPS candidate region was narrowed by searching for homozygous region in affected.</p><p><b>RESULTS</b>The OPS candidate region was narrowed to a 1 cM interval between D11S1296 and D11S4136.</p><p><b>CONCLUSION</b>Homozygosity mapping is a powerful method for mapping and narrowing the candidate region of the genes responsible for the rare autosomal recessive diseases.</p>