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Toru Ide

Publications and source records attributed to Toru Ide.

6 recordsLinked to original sources
PubMed2006

Immobilizing single lipid and channel molecules in artificial lipid bilayers with annexin A5.

The effects of annexin A5 on the lateral diffusion of single-molecule lipids and single-molecule proteins were studied in an artificial lipid bilayer membrane. Annexin A5 is a member of the annexin superfamily, which binds preferentially to anionic phospholipids in a Ca2+-dependent manner. In this report, we were able to directly monitor single BODIPY 1,2-dihexadecanoyl-sn-glycero-3-phosphoethanolamine (DHPE) and ryanodine receptor type 2 (RyR2) labeled with Cy5 molecules in lipid bilayers containing phosphatidylserine (PS) by using fluorescence microscopy. The diffusion coefficients were calculated at various annexin A5 concentrations. The diffusion coefficients of BODIPY-DHPE and Cy5-RyR2 in the absence of annexin A5 were 4.81 x 10(-8) cm(2)/s and 2.13 x 10(-8) cm(2)/s, respectively. In the presence of 1 microM annexin A5, the diffusion coefficients of BODIPY-DHPE and Cy5-RyR2 were 2.2 x 10(-10) cm(2)/s and 9.5 x 10(-11) cm(2)/s, respectively. Overall, 1 microM of annexin A5 was sufficient to induce a 200-fold decrease in the lateral diffusion coefficient. Additionally, we performed electrophysiological examinations and determined that annexin A5 has little effect on the function of RyR2. This means that annexin A5 can be used to immobilize RyR2 in a lipid bilayer when imaging and analyzing RyR2.

Animals↗
PubMed2006

Lysenin forms a voltage-dependent channel in artificial lipid bilayer membranes.

Lysenin, a hemolytic protein derived from the body fluid of earthworm, was incorporated into artificial bilayer membranes. Upon insertion, it formed a voltage-dependent large conductance channel in asolectin bilayers in a sphingomyelin-dependent manner. The channel had low ion-selectivity. Single-channel conductance was calculated as approximately 550 pS in 100 mM KCl. The channel in asolectin bilayers closed when the membrane was held at a positive potential. In contrast, the channel showed no voltage dependency in membranes made of pure phosphatidylcholine and sphingomyelin, suggesting some lipid contents included in the asolectin membranes affected channel gating.

Animals↗
PubMed2005

A novel method for artificial lipid-bilayer formation.

Many proposals have been made regarding the development of biosensors using single-channel recording with an artificial planar bilayer. The fragile nature of bilayer membranes is the major difficulty for the application of the artificial bilayer technique to the development of biosensors. We have developed an apparatus that promptly forms artificial bilayers. This technique is more efficient than other techniques for forming artificial bilayers. Bilayer membranes could be formed within 10s requiring 1 microl of analyte solution to record single-channel currents using our apparatus. A bilayer was formed by pressing the membrane on an agarose layer with hydraulic pressure. With this novel apparatus, we have recorded single-channel currents of various types of channels such as the BK-channel, the nicotinic receptor channel and the ryanodine receptor channel. The properties of the channels determined with this novel technique agreed well with those determined with conventional techniques.

Biosensing Techniques↗
PubMed2004

An amphotericin B-ergosterol covalent conjugate with powerful membrane permeabilizing activity.

Amphotericin B-sterol conjugates were synthesized and examined for their membrane permeabilizing activity. Ergosterol and cholesterol, each connected with amphotericin B via an ethylenecarbamate or hexamethylenecarbamate linker, were examined by K(+) flux assays using liposomes and by single-channel recording across phospholipid membrane. Among four conjugates tested, AmB-ergosterol bearing an ethylenecarbamate linker exhibited the most powerful activity, which substantially exceeded that of the cholesterol homolog. Single-channel recording clearly exhibited that the ergosterol conjugate elicited channel current with the conductance of 28 pS, which was comparable with those by AmB, and revealed a higher channel open probability than the cholesterol conjugate. These results imply that direct interaction between amphotericin B and ergosterol is reproduced by their conjugate, which may serve as a model compound for understanding the drug's selective toxicity.

Amphotericin B↗
PubMed2002

Simultaneous optical and electrical recording of a single ion-channel.

In recent years, the single-molecule imaging technique has proven to be a valuable tool in solving many basic problems in biophysics. The technique used to measure single-molecule functions was initially developed to study electrophysiological properties of channel proteins. However, the technology to visualize single channels at work has not received as much attention. In this study, we have for the first time, simultaneously measured the optical and electrical properties of single-channel proteins. The large conductance calcium-activated potassium channel (BK-channel) labeled with fluorescent dye molecules was incorporated into a planar bilayer membrane and the fluorescent image captured with a total internal reflection fluorescence microscope simultaneously with single-channel current recording. This innovative technology will greatly advance the study of channel proteins as well as signal transduction processes that involve ion permeation processes.

Electric Conductivity↗