Effects of zinc application on the growth and photosynthetic characteristics of pecan at the seedling stage.

Pecan (Carya illinoinensis) is sensitive to Zn, which is involved in basic physiological and biochemical processes. To explore the growth and physiology of pecan in response to Zn application, we used 1-year-old annual grafted seedlings (Pawnee) and applied four concentrations of Zn fertilizer (0.05, 0.10, 0.20 and 0.40 g·plant-1 ); a control (CK; no Zn fertilization) was also included. The growth characteristics, anatomical structure of the leaves and photosynthesis were assessed. Compared with the CK, photosynthesis and chlorophyll (Chl) fluorescence parameters, leaf area and leaf structure significantly increased at Zn concentrations of 0.05 and 0.10 g·plant-1 . In addition, growth of pecan at the seedling stage increased in response to moderate Zn application. In contrast, treatment with 0.20 and 0.40 g·Zn·plant-1 dramatically decreased these physiological indices and inhibited pecan growth. The results show that moderate soil Zn application promotes pecan growth and development by increasing photosynthesis. However excess Zn concentrations were not conducive to seedling growth. The concentration of 0.1 g·Zn·plant-1 was best when considering long-term soil Zn applications, providing a theoretical foundation for microelement management of pecan.

Conformation of DNA-DNA polymerase I complex observed by scanning tunneling microscopy.

The conformation of a complex of a 41 mer/31 mer DNA fragment and the Klenow fragment of DNA polymerase I of Escherichia coli was studied by scanning tunnelling microscopy (STM). The results shows that near two turns of double helix of this DNA fragment was outside of enzyme while another part containing more than one turn of helix and 10 nucleotides single strand was combined with enzyme. The dimension and shape of DNA polymerase I (KF) in complex were different from that of free enzyme. The conformation of DNA-DNA polymerase I (KF) complex and the application of STM in studying structure of complex of DNA polymerase with DNA were discussed.

Polymer- and surfactant-coated capillaries for isoelectric focusing.

This paper reports a method for deactivation of fused-silica capillaries to be used in capillary isoelectric focusing (cIEF). Deactivation was achieved by adsorbing either a surfactant or hydrophilic polymer to alkylsilane-derivatized capillaries. The surfactant PF-108 and methyl cellulose reduced electro-osmotic flow (EOF) 20 to 30 fold in comparison to underivatized capillaries. Although EOF was reduced sufficiently to allow focusing to permit separations to be completed before proteins were swept through the capillary, there was adequate flow to obviate the need for a separate mobilization step. This reduces the complexity of cIEF and increases reproducibility. Based on resolution of hemoglobin variants, proteins that varied 0.03 pH units in isoelectric point were resolvable. This is equivalent to the highest resolution achieved in conventional slab and tube gel isoelectric focusing.

Manipulation of electroosmotic flow in capillary electrophoresis.

This paper reports the use of surfactant and polymer-C18 coated capillaries that allow manipulation of electroosmotic flow (EOF). Although this approach to the control of EOF involves the preparation and use of multiple capillaries, all the coatings were prepared by a single procedure. It is shown that the ability to control EOF allows optimization of both separation time and resolution. In the case of proteins, low EOF maximizes resolution whereas high flow gives the shortest analysis time. It should be noted that proteins are a special case and this conclusion may not be true with other molecular species. Through selection of a specific coating, it is possible to complete a separation in the shortest time while maintaining sufficient resolution to give baseline resolution of proteins. The various coated capillaries were examined in capillary zone electrophoresis (CZE) and capillary isoelectric focusing (cIEF) separations of native protein standards and hemoglobin variants. Separation of glycosylated hemoglobin A1 variants was achieved by cIEF within 10 min, including the focusing time. Good run-to-run reproducibility was obtained by flushing the capillary with the coating solution between analyses.

Peptide nucleic acid pre-gel hybridization: an alternative to southern hybridization.

We have found that it is possible to use labeled peptide nucleic acid (PNA)-oligomers as probes in pre-gel hybridization experiments, as an alternative for Southern hybridization. In this technique, the PNA probe is hybridized to a denatured DNA sample at low ionic strength and the mixture is loaded directly on to an electrophoresis system for size separation. Ensuing gel electrophoresis separates the single-stranded DNA fragments by length. The neutral backbone of PNA allows for hybridization at low ionic strength and imparts very low mobility to excess PNA. Detection of the bound PNA is possible by direct fluorescence detection with capillary electrophoresis, or the DNA/PNA hybrids can be blotted onto a membrane and detected with standard chemiluminescent techniques. Efficient single bp discrimination was achieved routinely using both capillary and slab-gel electrophoresis.

Capillary electrophoresis-based immunoassay for cortisol in serum.

A competitive immunoassay for cortisol based on capillary electrophoresis (CE) and laser-induced fluorescence is described. The work involved the production of assay reagents and the development of separation conditions allowing for routine analysis of serum samples. Fluorescein-labeled cortisol was synthesized and purified. Fab fragments were produced from mouse monoclonal anticortisol antibody and purified using a POROS cation exchange chromatography column. After incubation of these reagents with serum, free and bound labeled antigen were separated by CE with high reproducibility. No prior sample cleanup of the serum samples was necessary. Serum calibration curves were established and used for the quantitation of cortisol in serum. The results demonstrate feasibility for a cortisol assay based on CE operating directly on serum samples.