arXiv subjects

Yuzuru Tozawa

Publications and source records attributed to Yuzuru Tozawa.

3 recordsLinked to original sources

arXiv2026

Genesis of a Horizontal Electric Field within the Lipid Bilayer: A Bilayer-Embedded Actuation Platform

The electric field of biological membranes has long been treated as a one-dimensional quantity, defined solely by the component normal to the bilayer (E_VERT). Here, we present a bioelectronic platform that enables controlled generation of a horizontal electric field within the hydrophobic core of a lipid bilayer (E_HORZ). The device incorporates micrometer-scale electrodes embedded within the bilayer torus, allowing sustained E_HORZ actuation. Applied E_HORZ selectively and reversibly accelerates slow inactivation of a voltage-gated potassium channel while leaving activation essentially unchanged. Physical considerations further indicate that E_HORZ arises naturally wherever membrane potential varies spatially, including at action potential wavefronts, suggesting broader physiological relevance. This platform provides experimental access to vector-resolved membrane electric fields and establishes a generalizable strategy for multidirectional electrical control of soft-matter biointerfaces.

physics.bio-ph↗

arXiv2023

Model-Free Idealization: Adaptive Integrated Approach for Idealization of Ion Channel Currents (AI2)

Single-channel electrophysiological recordings provide insights into transmembrane ion permeation and channel gating mechanisms. The first step in the analysis of the recorded currents involves an "idealization" process, in which noisy raw data are classified into two discrete levels corresponding to the open and closed states of channels. This provides valuable information on the gating kinetics of ion channels. However, the idealization step is often challenging in cases of currents with poor signal-to-noise ratios (SNR) and baseline drifts, especially when the gating model of the target channel is not identified. We report herein on a highly robust model-free idealization method for achieving this goal. The algorithm, called AI2 (Adaptive Integrated Approach for the Idealization of Ion Channel Currents), is composed of Kalman filter and Gaussian Mixture Model (GMM) clustering and functions without user input. AI2 automatically determines the noise reduction setting based on the degree of separation between the open and closed levels. We validated the method on pseudo-channel-current datasets which contain either computed or experimentally recorded noise. The AI2 algorithm was then tested on actual experimental data for biological channels including gramicidin A, a voltage-gated sodium channel, and other unidentified channels. We compared the idealization results with those obtained by the conventional methods, including the 50%-threshold-crossing method.

q-bio.QM↗

arXiv2019

A Teflon-based system for applying multidirectional voltages to lipid bilayers as a novel platform for membrane proteins

Artificial bilayer lipid membranes (BLMs), along with patch-clamped membranes, are frequently used for functional analyses of membrane proteins. In both methods, the electric properties of membranes are characterized by only one parameter, namely, transmembrane potential. Here the construction of a novel BLM system was reported, in which membrane voltages can be controlled in a lateral direction in addition to conventional transmembrane direction. A microaperture was fabricated in a Teflon film and Ti electrodes were evaporated around the aperture. BLMs were reproducibly formed in the aperture without being affected by the presence of the electrodes. The application of a lateral voltage induced no significant changes in the electric properties of the BLMs, such as baseline current, transmembrane resistance, and transmembrane capacitance. In contrast, lateral voltages clearly affected the activities of biological ion channels, suggesting that the lateral voltage might be a useful parameter for analyzing channel activities. The present Teflon-based system in which multidirectional voltages can be applied to BLMs represent a promising platform for the analysis of underlying functional properties of membrane proteins.

physics.bio-ph↗