Mechanism of How Salt-Gradient-Induced Charges Affect the Translocation of DNA Molecules through a Nanopore

Experiments using nanopores demonstrated that a salt gradient enhances the capture rate of DNA and reduces its translocation speed. These two effects can help to enable electrical DNA sequencing with nanopores. Here, we provide a quantitative theoretical evaluation that shows the positive net charges, which accumulate around the pore entrance due to the salt gradient, are responsible for the two observed effects: they reinforce the electric capture field, resulting in promoted molecule capture rate; and they induce cationic electroosmotic flow through the nanopore, thus significantly retarding the motion of the anionic DNA through the nanopore. Our multiphysical simulation results show that, during the polymer trapping stage, the former effect plays the major role, thus resulting in promoted DNA capture rate, while during the nanopore-penetrating stage the latter effect dominates and consequently reduces the DNA translocation speed significantly. Quantitative agreement with experimental results has been reached by further taking nanopore wall surface charges into account.     

A comparative analysis of photosynthetic characteristics of hulless barley at two altitudes on the Tibetan Plateau

To determine the photosynthetic characteristics of C₃ plants and their sensitivity to CO₂ at different altitudes on the Tibetan Plateau, hulless barley (Hordeum vulgare L. ssp. vulgare) was grown at altitudes of 4,333 m and 3,688 m. Using gas-exchange measurements, photosynthetic parameters were simulated, including the maximum net photosynthesis (P _max) and the apparent quantum efficiency (α). Plants growing at higher altitude had higher net photosynthetic rates (P _N), photosynthesis parameters (P _max and α) and sensitivities to CO₂ enhancement than plants growing at lower altitude on the Tibetan Plateau. The enhancements of P _N, P _max, and α for plants growing at higher altitude, corresponding with 10 μmol(CO₂) mol⁻¹ increments, were approximately 0.20∼0.45%, 0.05∼0.20% and 0.12∼0.36% greater, respectively, than for plants growing at lower altitude, respectively, where CO₂ levels rose from 10 to 170 μmol(CO₂) mol⁻¹. Therefore, on the Tibetan Plateau, the changes in the photosynthetic capacities and the photosynthetic sensitivities to CO₂ observed in the C₃ plants grown above 3,688 m are likely to increase with altitude despite the decreasing CO₂ partial pressure.     

Clinical manifestations of taeniasis in Taiwan aborigines.

From 1974 to 1989, a total of 24,500 aborigines at 67 villages in ten mountainous districts/towns in Taiwan were examined for the Taiwan Taenia infection and 12% were found to be infected. In order to define the clinical manifestations of taeniasis caused by the Taiwan Taenia, 1661 aborigines in ten mountainous districts were surveyed. The overall clinical rate was 76%. The clinical rate was highest among Atayal aborigines (81%), followed by Bunun (66%) and Yami (61%) aborgines and lowest among Ami aborigines (40%). Among 1153 infected people, 10% had passed gravid segments in the faeces for less than 1 year, 24% for 1-3 years, 17% for 4-5 years, 23% for 6-10 years, 16% for 11-20 years, 7% for 21-30 years, and 3% over 30 years. Twenty-six occurrences of gastrointestinal and neurological symptoms were reported by 1258 infected persons. Passing proglottides in the faeces (95%) was the most frequent sign, followed by pruritis ani (77%), nausea (46%), abdominal pain (45%), dizziness (42%), increased appetite (30%), headache (26%), etc.     

Production and characterization of antibodies against HT-2 toxin and T-2 tetraol tetraacetate.

Three new immunogens which were prepared by conjugation of the carboxymethyl oxime (CMO) derivatives of HT-2 toxin, T-2 tetraol (T-2 4ol), and T-2 tetraol tetraacetate (T-2 4Ac) to bovine serum albumin (BSA) were tested for the production of antibodies against the major metabolites of T-2 toxin. Antibodies against HT-2 toxin and T-2 4Ac were obtained from rabbits 5 to 10 weeks after immunizing the animals with CMO-HT-2-BSA and CMO-T-2 4Ac-BSA conjugates. Immunization with CMO-T-2 4ol-BSA resulted in no antibody against T-2 4ol. The antibody produced against HT-2 toxin had great affinity for HT-2 toxin as well as good cross-reactivity with T-2 toxin. The relative cross-reactivities of anti-HT-2 toxin antibody with HT-2 toxin, T-2 toxin, iso-T-2 toxin, acetyl-T-2 toxin, 3'-OH HT-2, 3'-OH T-2, T-2 triol, and 3'-OH acetyl-T-2, were 100, 25, 10, 3.3, 0.25, 0.15, 0.12 and 0.08%, respectively. Antibody against CMO-T-2 4Ac was very specific for T-2 4Ac and had less than 0.1% cross-reactivity with T-2 toxin, HT-2 toxin, acetyl-T-2 toxin, diacetoxyscirpenol, deoxynivalenol, and deoxynivalenol triacetate as compared with T-2 4Ac. The detection limits for HT-2 toxin and T-2 4ol by radioimmunoassay were approximately 0.1 and 0.5 ng per assay, respectively.     

An electrophoretic karyotype for Schizosaccharomyces pombe by pulsed field gel electrophoresis.

The three chromosomal DNAs of S. pombe have been fractionated by pulsed field gel electrophoresis. The resulting molecular karyotype will greatly speed gene mapping in this organism, and it indicates that the separation range of the technique extends to DNA molecules as large as 9,000,000 base pairs.     

记辽宁东部新鳞齿鱼属一新种

本文记述了产自辽宁东部红庙子盆地下桦皮甸子组的新鳞齿鱼属—新种——Neolepidotes liaodongensis sp. nov..根据新材料,将 Neolepidotes 与 Lepidotes 等属作了补充比较,增订了新鳞齿鱼属的特征.     

Level of protein kinase C activity correlates directly with resistance to adriamycin in murine fibrosarcoma cells

In this report, we demonstrate a direct correlation between protein kinase C (PKC) activity and adriamycin (ADR) resistance in mouse fibrosarcoma cells. PKC activity was measured in four murine UV-2237M fibrosarcoma cell lines that differed in the degrees to which they expressed resistance to ADR, which is an inhibitor of PKC. A comparison of the four cell lines revealed a positive correlation between the level of PKC activity and resistance to ADR. Incubation of the cells with the PKC inhibitor H-7 produced a partial reversal of ADR resistance. Taken together, these results suggest a role for PKC in the mechanism of ADR resistance.     

Exon-intron organization, expression, and chromosomal localization of the human motilin gene

The human motilin gene has been isolated and characterized. The gene spans about 9 kilobase pairs (kb) and the 0.7 kb motilin mRNA is encoded by five exons. The 22-amino-acid motilin sequence is encoded by exons 2 and 3. The human motilin gene was mapped to the p21.2----p21.3 region of chromosome 6 by hybridization of the cloned cDNA to DNAs from a panel of reduced human-mouse somatic cell hybrids and by in situ hybridization to human prometaphase chromosomes. RNA blotting using RNA prepared from various regions of the human gastrointestinal tract revealed high levels of motilin mRNA in duodenum and lower levels in the antrum of the stomach; motilin mRNA could not be detected by this procedure in the esophagus, cardia of the stomach, descending colon or gallbladder.     

Production and characterization of a monoclonal antibody cross-reactive with most group A trichothecenes

A monoclonal antibody cross-reactive with most group A trichothecenes was produced by fusion of P3/NS-1/1-AG4-1 myeloma cells with spleen cells isolated from a BALB/c mouse that had been immunized with 3-acetyl-neosolaniol-hemisuccinate conjugated to bovine serum albumin. One stable clone, H159B1D5, which produced monoclonal antibody that bound with both T-2 toxin and diacetoxyscirpenol (DAS) was obtained after subcloning. Enzyme-linked immunosorbent assay (ELISA) revealed that the antibody belongs to the immunoglobulin G1 (kappa chain) isotype and had binding constants of 2.81 x 10(9), 1.05 x 10(9), and 1.57 x 10(8) liters per mole for T-2 tetraol tetraacetate, T-2 toxin, and DAS, respectively. The relative cross-reactivities of the antibody with T-2 tetraol tetraacetate, T-2 toxin, and DAS were 200, 100, and 20, respectively, with tritiated T-2 toxin as the marker ligand. The relative cross-reactivities for the above toxins were 667, 100, and 73, respectively, with tritiated DAS as the marker ligand. No cross-reaction with HT-2 and deoxynivalenol triacetate was observed in either system. By using this monoclonal antibody, an indirect ELISA for analysis of T-2 toxin was also developed. The linear portion of the standard curve for analysis of T-2 toxin in each analysis by radioimmunoassay and ELISA was in the range of 0.1 to 2 ng and 0.05 to 1.0 ng, respectively.