Tadaaki Kakutani

Electrorotation of non-spherical cells: Theory for ellipsoidal cells with an arbitrary number of shells

Abstract Theoretical expressions for electrorotation are derived for an ellipsoidal cell model with an arbitrary number of confocal shells. The theory for a spherical cell model with an arbitrary number of shells can be obtained as a special case of the present theory. Theoretical expressions are presented for several ellipsoidal cell models which are relevant to biological cells. The effects of cell shape and size on the electrorotation spectrum are discussed in detail for the case of the ellipsoidal single-shell model under the conditions that seem appropriate for biological cells.

403 - Polarographic studies on proteins

Abstract Basic information concerning the behavior, on electrochemical reduction and oxidation, of proteins and enzymes at a mercury electrode and other electrodes is summarized. The electrochemical behavior of ferredoxin at a mercury electrode is interpreted on the basis of the theory of surface redox reaction. Equations of Brdicka current at a d.m.e. and a h.m.d.e. of SS/SH-containing proteins are presented in which the Brdicka current activity of protein is represented by a constant k B -Values of k B of various proteins are given. Cytochrome c and myoglobin contain neither the SS nor the SH group, but give a Brdicka current which is attributable to the heme moiety in the molecules. The Brdicka current can be utilized for the study of protein-protein interaction, as well as for trace analysis of proteins. Other polarographic methods of trace analysis of proteins are summarized.

Electrochemical study of the transfer of uncouplers across the organic/aqueous interface

Abstract Ion-transfer electrochemistry at the polarizable nitrobenzene/water interface of four uncouplers of oxidative phosphorylation: picric acid, 2,4-dinitrophenol, carbonylcyanide p-trifluoromethoxyphenylhydrazine (FCCP), and 3,5-di(tert-butyl)-4-hydroxybenzylidenemalononitril (SF6847) is studied using potential step chronoamperometry (normal pulse voltammetry) and cyclic voltammetry. The voltammograms are interpreted in terms of the facilitated transfer of protons from the water to the nitrobenzene phase by the dissociated form the uncouplers present in the nitrobenzene phase for all the four compounds and of the simple transfer of the dissociated forms from the nitrobenzene to water phase for the first two compounds, depending on the pH of the water phase. Some physicochemical properties of the uncouplers relevant to the facilitated transfer of protons at the interface between organic and aqueous phases are presented.

Electrorotation of barley mesophyll protoplasts

Abstract Electrorotation of barley mesophyll protoplasts was investigated as a function of the conductivity of the external medium in the frequency range 1-1800 kHz. The halfwidth of the first peak in the electrorotation spectrum increased with increasing conductivity of the external medium and its values were appreciably larger than the theoretical value of (1, 14 given by) the single-shell model described in the literature, whereas the (first) characteristic frequency at which the electrorotation velocity reaches a maximum increased approximately linearly with the conductivity of the external medium. These results were explained well by the three-shell model theory which assumes another membrane-covered sphere inside the single-shell model cell. The plasma membrane capacitance was determined from the dependences of both the halfwidth of the peak and the characteristic frequency on the conductivity of the external medium by using the three-shell model theory under appropriate assumptions for several parameters. Also, the conditions under which the three-shell model theory can be reduced to the single-shell model theory are theoretically discussed under assumptions which seem appropriate for biological cells.

Polarographic studies on proteins

Summary Basic information concerning the behavior, on electrochemical reduction and oxidation, of proteins and enzymes at a mercury electrode and other electrodes is summarized. The electrochemical behavior of ferredoxin at a mercury electrode is interpreted on the basis of the theory of surface redox reaction. Equations of Brdicka current at a d.m.e. and a h.m.d.e. of SS/SH-containing proteins are presented, in which the Brdicka current activity of protein is represented by a constant k B . Values of k B of various proteins are given. Cytochrome c and myoglobin contain neither the SS nor the SH group, but give a Brdicka current which is attributable to the heme moiety in the molecules. The Brdicka current can be utilized for the study of protein-protein interaction, as well as for trace analysis of proteins. Other polarographic methods of trace analysis of proteins are summarized.

Electrorotation of vacuoles isolated from barley mesophyll cells

Abstract Electrorotation of vacuoles isolated from barley mesophyll protoplasts was investigated as a function of the conductivity of the external medium in the frequency range from 1 to 1800 kHz. The half-peak width of the electrorotation spectrum was independent of the conductivity of the external medium, whereas the (first) characteristic frequency at which the electrorotation velocity reaches a maximum increased linearly with increasing conductivity of the external medium. These results were well explained by the single-shell model theory which considers the cell as a homogenous sphere surrounded by a thin homogenous shell (cell membrane). The electrical properties of tonoplast membrane were determined by the dependence of the characteristic frequency on the conductivity of the external medium. The membrane capacitance and conductance of barley mesophyll vacuole were found to be 0.68 ± 0.14 μF cm −2 and −2 S cm −2 respectively.

THEORY OF ION-SELECTIVE ELECTRODES, AMPEROMETRIC ISE AND POTENTIOMETRIC ISE

ABSTRACT The polarizable liquid/liquid or oil/water interface can function as the ion-selective electrode interface for both amperometry (or voltammetry) and potentiometry of ion(s). The amperometric ion-selective electrode gives the current response proportional to the concentration of ion(s) whereas the potentiometric ion-selective electrode gives the potential response linear to the logarithm of the activity of ion.

Electrocapillarity and the Electric Double Layer Structure at Oil/Water Interfaces

Oil/water interfaces are classified into the ideal-polarized interface and the nonpolarized interface. The interface between a nitrobenzene solution of tetrabutylammonium tetraphenylborate and an aqueous solution of lithium chloride behaves as an ideal-polarized interface in a certain potential range. Electrocapillary curves of the interface were measured. The results are analyzed using the electrocapillary equation of the ideal-polarized interface and the Gouy-Chapman theory of diffuse double layers. The electric double layer structure consisting of the inner layer and the two diffuse double layers on each side of the interface is discussed. Electrocapillary curves of the nonpolarized oil/water interface are discussed for two cases of a nonpolarized nitrobenzene/water interface.

Polarographic studies of some porphyrins and metalloporphyrins in N, N′-dimethylformamide☆

Abstract Electrochemical behavior of protoporphyrin IX dimethylester (PPDM), mesoporphyrin IX dimethylester, Fe(III)Cl-protoporphyrin, Ni(II)-, Cu(II)-, Zn(II)-, Co(II)- and Mn(III)Cl-PPDM was investigated in dimethylformamide by use of d.c. polarography, a.c. polarography, cyclic voltammetry and radio-frequency polarography. These porphyrins and divalent metal complexes of prophyrin gave, for the most part, three reduction waves. The first and second waves were reversible one-electron steps in each case but the third one was irreversible. Kinetic parameters of the first two steps were determined by radio-frequency polarographic method.