Oscillation of Membrane Potential in Chemically Modified Poly(α-amino acid) Membranes

Abstract

Chemically modified poly(γ-methyl-L-glutamate) membranes having several lengths of diamine segments generated oscillation of membrane potential under a concentration gradient of several salts, although nonmodified membranes showed constant potential. The oscillation of membrane potential is considered to be caused by the fluctuation of the fixed charge density originating from the thermal fluctuation of partially ionized amine segments in the modified membranes. The amplitude of the oscillation was greater in the modified membranes having longer diamine segments. It was also influenced by the salts used, and the highest amplitude of the oscillation was observed when LiCl was used as the salt. Fast Fourier transport analysis revealed that the oscillation of membrane potential is not chaotic but has specific frequencies. It might be possible to recognize a particular salt present in the solution from the information on the amplitude and the power spectrum of fast Fourier transport in the oscillation of membrane potential.

Oscillation of membrane potential in ion–complex membranes of DNA and hexamethylenediamine

“…The oscillation of the membrane potential in the ionÈcomplex membranes of DNA and hexamethylenediamine can be expected to be generated at pH 7.0 which is a more natural condition compared to pH 10.0 in the previous study. 19 The recognition of the salt present in the solution is also investigated from the amplitude and the power spectra of fast Fourier transform during the oscillation of the membrane potential. This observation may contribute to a simple model of the processing method for the recognition of taste and smell found in animal brains.…”

Development of Molecular Recognition Membrane showing Autonomous Adsorption-Desorption Phenomenon

“…By seeking such chemical oscillation system, some researchers achieved artificial nonlinear oscillators such as BZ reaction, permeation phenomena of membrane, rhythmic drug delivery systems, and so on. [1][2][3][4][5] However, only one work has achieved an artificial oscillatory system induced by molecular recognition, the important feature of living body. [6] Meanwhile, our group has succeeded in developing polymeric material exhibiting a coordination of molecular recognition and actuation function within the polymer itself.…”

Oscillation of Membrane Potential in Immobilized DNA Membranes

“…The Belousov-Zhabotinsky reaction [11][12][13] is widely known in such phenomena and was explained by the Field-Koros-Noyas mechanism. 14 Several kinds of artificial membranes [15][16][17][18][19][20][21][22][23][24] which induce the oscillation of the membrane potential have also been reported as simple models of cells and living membranes. Most of the studied artificial membranes [15][16][17][18][19] are bimolecular lipid or liquid membranes.…”

“…Only a few studies deal with the electrical oscillatory phenomena in artificial polymeric membranes. [20][21][22][23][24] Huang and Spangler 21 studied a poly(glutamic acid)-Ca 2+ membrane in order to clarify the dynamic behavior of the electrical oscillation. Minoura et al 22 observed the spontaneous oscillation of the electrical membrane potential in a triblock copolypeptide membrane separating KCl solutions of different concentrations.…”

“…Poly(γ-methyl-L-glutamate), PMLG, membranes were prepared by casting a 1 wt % PMLG solution onto flat Petri dishes and then drying at room temperature for 6 days. The membranes having a thickness of 30-35 µm were selected for use in the chemically modified reaction, and the aminolysis reaction of the PMLG membranes (i.e., Scheme 1) was performed by dipping the membranes in ethylenediamine (EDA), 1,3-diaminopropane (DAP), 1,4-diaminobutane (DAB), and hexamethylenediamine (HMD) at 25 °C (for the EDA and DAP reactions) or 50 °C (for the DAB and HMD reactions) for 6 h. 23 The modified membranes were rinsed with ethanol and subsequently dried under vacuum at room temperature. The diaminated ratio was estimated from an atomic analysis of the membranes, and the diaminated ratio under the described conditions was estimated to be 0.21 ( 0.02 for the EDA modification (EDA-PMLG), 0.12 ( 0.01 for the DAP modification (DAP-PMLG), 0.24 ( 0.02 for the DAB modification (DAB-PMLG), and 0.15 ( 0.02 for the HMD modification (HMD-PMLG) in this study (see Scheme 1).…”