Michiko Tanaka

Ab initio calculation of capacitance of semi-infinite jellium electrodes with a nanoscale gap

We have examined the capacitance of two parallel jellium electrodes with a nanoscale gap using an ab initio method within the density functional theory. As the gap becomes smaller, first the calculated capacitance exhibits behavior qualitatively similar to that estimated using classical electrostatics, but is systematically larger than the classical one. Then, the calculated capacitance decreases when the gap approaches zero. The value of the maximum capacitance is larger for a smaller Wigner-Seitz radius of the electrodes. These results can be understood from two quantum effects, namely, electron spill from the electrodes and tunneling between the electrodes.

Unsaturated fatty acid synthesis in respiratory-deficient yeast

Summary 1. The composition and formation of unsaturated fatty acids in respiratory-deficient and in normal yeast were the same. 2. The mutant cell was shown to possess no normal mitochondria. Particles which bind the enzyme for the desaturation of fatty acids have another origin.

Ultrasonic Properties of a Binary System of a Soluble Protein, α-Lactalbumin and Dimyristoyl Phosphatidylcholine Membrane

The interaction between a soluble protein α-lactalbumin (α-LA) and dimyristoyl phosphatidylcholine (DMPC) liposomes was studied using an ultrasonic technique. The ultrasonic properties of DMPC liposomes changed significantly after the addition of α-LA at pH 3. The lipid bilayer transition temperature became higher and transition anomalies of DMPC liposomes were enhanced in the presence of α-LA under these conditions. At the same time, the size of the liposomes apparently decreased as revealed by the clearing of suspensions.

ab initio Calculation of Capacitance of Nanostructures

We report our recent results on the electrochemical capacitances of nanostructures under various conditions investigated by new ab initio methods based on the density-functional theory. As the gap of two semi-infinite electrodes decreases, capacitance shows a crossover from classical to quantum behaviors caused by electron tunneling that is highly sensitive to the atomic geometry of electrode surfaces. The calculated capacitances of two electrodes of various nanostructures in the case without electron tunneling are in good agreement with the experimental observations. The atomic geometry and electronic states of clusters and fullerenes are found to faithfully reflect the self-capacitances of the electrodes. The results enable us to emphasize the quantum nature of capacitance on the nanoscale.

Effect of Carbonic Anhydrase II in Molten Globule State on Physical Properties of Dimyristoylphosphatidylcholine Liposome

Ultrasonic relaxation measurement was employed for confirmation of the interaction between dimyristoylphosphatidylcholine (DMPC) membrane and a soluble protein, carbonic anhydrase II (CA II). The enhancement of the fluctuation of DMPC membrane structure was observed in the presence of CA II under acidic condition, pH 3.6–4, indicating the interaction between DMPC and CA II. The pyrene fluorescence spectrum of CA II solution clearly showed that this protein adopted an unfolding intermediate called the molten globule state under the low pH condition, in which CA II interacted with DMPC. However, CA II in the molten globule state did not cause membrane lysis in contrast to the high lytic activity of α-lactalbumin on DMPC liposomes.