• Carbon letters
• /
• v.13 no.4
• /
• pp.248-253
• /
• 2012

Dielectrophoretic filtering and alignment of single-walled carbon nanotubes (SWCNTs) were tested using deuterium oxide as a solvent. A solution of deuterium oxide-SWCNTs was dropped on top of a silicon chip and an ac electric field was applied between pre-defined electrodes. Deuterium oxide was found to be a better solvent than hydrogen oxide for the dielectrophoresis process with higher efficiency of filtering. This was demonstrated by comparing Raman spectra measured on the initial solution with those measured on the filtered solution. We found that the aligned nanotubes along the electric field were not deposited on the substrate but suspended in solution, forming chain-like structures along the field lines. This so-called pearl chain formation of CNTs was verified by electrical measurements through the aligned tubes. The solution was frozen in liquid nitrogen prior to the electrical measurements to maintain the chain formation. The current-voltage characteristics for the sample demonstrate the existence of conduction channels in the solution, which are associated with the SWCNT chain structures.

• Journal of Life Science
• /
• v.7 no.4
• /
• pp.282-288
• /
• 1997

To obtain a basic information on the development of Genus Viola, ultrastructure and electrofusion process between the two protoplasts from wild Viola callus cells and pansy mesophyll cells were observed with a scanning electron microscopy(SEM) and transmission electron microscopy(TEM). In the ultrastructural observation of wild viola callus protoplasts and pansy mesophyll protoplasts using SEM, their cell walls were removed completely. A knob-like formation was observed on the enlarge surface of viola callus protoplasts. On the surface of pansy mesophyll protoplasts net-like chloroplasts were observed. In SEM observation of pansy mesophyll protoplasts, chloroplasts devoid of membrane were observed on the surface the protoplasts. Pearl chain was formed by applying AC field of 200 V/cm at 1.0 MHz for 43 sec. The lysis of plasma membranes and fusion process occurred by applying a 1,600 V/cm DC pulse twice for 1 sec. After 1-2 hours of a DC pulse application, it was observed that the two protoplasts were fused completely into one cell. In TEM observation of the fused cell, many small vacuoles were located in the fusion area of the two protoplasts. Indeed, two distinct regions were observed during fusing process; in one region, a nucleus was found, while in the other region, both nucleus and nucleous were found.

• Applied Biological Chemistry
• /
• v.33 no.1
• /
• pp.93-100
• /
• 1990

The optimum conditions of electric stimulation for electrofusion of protoplasts of petunia, carrot and soybean, and the effects of calcium, magnesium, protease, trypsin, triton X-100, concanavalin A, dimethyl sulfoxide(DMSO), glycerol monooleate and spermine on fusion frequency and/or viability of petunia protoplast were investigated. The optimum frequencies(Hz)-amplitudes(V/cm) of AC Pulse for protoplast pearl-chain formation were 10 kHz-20 V/cm and 1 MHz-60 V/cm for petunia, 100 kHz-40 V/cm and $1\;MHz-40{\sim}60\;V/cm$ for carrot, and $1\;MHz-40{\sim}80\;V/cm$ for soybean, respectively. The optimum condition of DC pulse treatment at the 1 MHz-60 V/cm-15sec treatment of AC for electrofusion of petunia protoplasts was 2.5 kV/cm-40 sec, and under this condition the fusion frequency and viability of protoplasts were 45 % and 10 %, respectively, Both of the protoplasts of carrot and soybean were not fused under the AC and DC conditions tested in this experiment. The electrofusion of petunia protoplasts was stimulated by calcium, and the fusion frequency and the viability of the protoplasts were 43 % and 11 % , respectively at the calcium concentration of 140 mM. Although fusion frequency was not affected by magnesium only, magnesium stimulated fusion frequency in the presence of calcium, and the viability and fusion frequency of petunia protoplasts were 45 % and 13 %, respectively, at 140 mM of magnesium-140 mM of calcium. The relative fusion frequencies of petunia protoplasts to the controls were increased by 2.4, 2.1, 1.6, 1.4, 1.8, 1.5 and 2.2 folds, respectively, by the treatments of protease, trypsin, triton X-100, concanavalin A, DMSO, glycerol monooleate, and spermine. The viabilities of petunia protoplasts were decreased by these substances.