Instability of the Homogeneous Distribution of Chemical Waves in the Belousov-Zhabotinsky Reaction.

Nobuhiko J. Suematsu,Satoshi Nakata

doi:10.3390/ma14206177

Nobuhiko J. Suematsu, Satoshi Nakata

Open Access

https://doi.org/10.3390/ma14206177

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Abstract

Chemical traveling waves play an important role in biological functions, such as the propagation of action potential and signal transduction in the nervous system. Such chemical waves are also observed in inanimate systems and are used to clarify their fundamental properties. In this study, chemical waves were generated with equivalent spacing on an excitable medium of the Belousov–Zhabotinsky reaction. The homogeneous distribution of the waves was unstable and low- and high-density regions were observed. In order to understand the fundamental mechanism of the observations, numerical calculations were performed using a mathematical model, the modified Oregonator model, including photosensitive terms. However, the homogeneous distribution of the traveling waves was stable over time in the numerical results. These results indicate that further modification of the model is required to reproduce our experimental observations and to discover the fundamental mechanism for the destabilization of the homogeneous-distributed chemical traveling waves.

Highlights

Traveling waves are widely observed in biological systems, such as the action potential propagation on cardiac muscles, which results in the pump function of the heart [1,2,3].These traveling waves were observed in nonliving chemical systems, such as the Belousov–Zhabotinsky (BZ) reaction, which is a well-known nonlinear chemical reaction that realizes periodic oscillation and ordered pattern formation [4,5]
If the core of the spiral wave is periodically perturbed by electrical stimuli, the spacing of the chemical waves oscillates over time
To generate chemical waves with a homogeneous distribution, we used a characteristic condition of the photosensitive BZ reaction, in which both photoexcitation and photoinhibition could be realized under the same chemical conditions with different light fields [26]

Summary

Introduction

Traveling waves are widely observed in biological systems, such as the action potential propagation on cardiac muscles, which results in the pump function of the heart [1,2,3]. Lázár et al preliminarily demonstrated the behavior of inhomogeneous-distributed wave trains [24] They prepared a circular excitable medium of the BZ reaction, and unidirectional traveling waves were generated on the medium. To generate chemical waves with a homogeneous distribution, we used a characteristic condition of the photosensitive BZ reaction, in which both photoexcitation and photoinhibition could be realized under the same chemical conditions with different light fields [26] Under these conditions, steady light illumination inhibits a chemical wave, while a sudden increase in light intensity excites a chemical wave. Steady light illumination inhibits a chemical wave, while a sudden increase in light intensity excites a chemical wave Using this characteristic photosensitivity, we successfully prepared a homogeneous wave train as the initial condition and investigated its stability. To support our experimental observation, we carried out numerical calculations using a modified Oregonator model for such a characteristic photosensitive BZ reaction [26]

Materials and Methods

Generation of Unidirectional Chemical Waves

Stability

Snapshots

4.4.Discussion

Stability of the Homogeneous Distribution of Chemical Waves

Stability of the Homogeneous