JPH03244171A - Bioelement - Google Patents

Abstract

PURPOSE:To dispense with an external pressure in the self-oscillation of an artificial film by a method wherein the pH of the salt solution on a low- concentration side among salt solutions, between which the excitative artificial film, which has adsorbed a fatty material having an oleyl group is interposed, is set at a specified value or lower. CONSTITUTION:An artificial film 11 is supported in a state that it is in contact to both of 100mMKCl of an aqueous solution 15a housed in an electrolytic cell 13a and 5mMKCl of an aqueous solution 15b housed in an electrolytic cell 13b. HCl is added to the aqueous solution 15b in this cell 13b and the self- oscillation of a potential in the case where the pH of the aqueous solution 15b is changed is measured. Whereupon, as the pH is decreased, an oscillation starting pressure is steeply reduced and when the pH reaches a pH4, the pressure becomes unnecessary. Moreover, when the pH is reduced, a DC current is also reduced gradually and becomes unnecessary in a pH2.5 or lower. In the pH2.5 or lower, the oscillation is generated without applying the external pressure and the DC current and this oscillation frequency is increased as the pH is reduced and is changed into a distorted waveform in a pH1 or lower.

Description

[Detailed Description of the Invention] (Field of Industrial Application) This invention is a biological technology using an excitable artificial membrane that can imitate the information expression and transmission functions of biological nerve cells and perform various types of recognition. Regarding elements.

(Prior Art) Elements in conventional computers are mainly composed of inorganic materials such as silicon semiconductor elements, and their processing functions are based on phono-neuman (VanNeuman) technology.
n n ) method to execute serial logical operations. Although this method can perform accurate logical operations, it has the drawback that, for example, it is difficult to simultaneously perform the large amount of information processing required for pattern recognition, which the brains of higher organisms are good at. Ta.

On the other hand, research on the cognitive functions of living organisms has progressed rapidly in recent years. It is becoming clear that these materials have so-called plasticity.

However, there are still many unknowns about the principles on which functions such as pattern recognition, learning, and memory found in the brain are carried out, as well as the constituent components involved. Many researchers are working to elucidate these issues.

In general, living things receive various stimuli from the outside world through their sensory organs, transmit these to the brain via neurons and synapses connecting multiple neurons, and the brain, which is made up of many neurons, processes the information. ing. An example of such a recognition function will be explained.

First, stimulation (information) from the outside world is converted into an electrical signal and a nerve impulse is generated. When this nerve impulse reaches the end of the axon that makes up a neuron, chemicals contained in vesicles called neurotransmitters are released. As such neurotransmitters, acetylcholine, etc., and ions such as calcium ions (Ca') in a broader sense are also known, and neurotransmitters released outside the cell are, for example, activated by receptors present in the plasma membrane of adjacent cells. It is taken into cells through the body and induces new nerve impulses.

Furthermore, neurotransmitters are released from the presynaptic membrane that receives such nerve impulses in the same way as described above, and diffuse to other adjacent postsynaptic membranes, where they are taken up through receptors and induce nerve impulses. be exposed. This series of information transmission via nerve impulses is called excitation, and is thought to reach the brain via multiple synapses.

In imitating such biological systems and performing parallel information processing, there have been attempts to realize functional elements using the aforementioned lipids that constitute the plasma membrane.

For example, "Phase transition and self-oscillation phenomena in synthetic lipid membranes"
(Kyoshi Toko et al., MEMBRANE, 12 (
1).

P., 12-21, 1987), an excitable artificial membrane (hereinafter sometimes simply referred to as an artificial membrane) in which lipids are adsorbed to a porous membrane is used, and this artificial membrane is automatically activated. The phenomenon of oscillation is known.

The automatic oscillation phenomenon described above will be briefly explained below. number(
C) An artificial membrane is prepared by adsorbing dioleyl phosphate, which is a synthetic lipid, onto a porous membrane having a pore size of approximately

One surface of such an artificial membrane is brought into contact with an electrolytic solution with a high salt concentration, and the other surface is brought into contact with an electrolytic solution with a low salt concentration. The artificial membrane placed in such a state generates a predetermined potential difference between these electrolytes over a period of several minutes to several tens of minutes,
An electrical impulse is generated. Automatic oscillation with such a period is called long-period oscillation.

Next, in addition to the salt concentration difference (ion concentration gradient) mentioned above,
By applying a direct current to the artificial membrane and also applying a predetermined pressure to the membrane, automatic oscillation with a period of several seconds, called short-period oscillation, is observed.

In this short-period oscillation, the oscillation period of the electrical impulse can be controlled by changing the above-mentioned DC current value.

The mechanism of automatic oscillation described above is thought to be associated with a phase transition of lipids, such as a change from an oil droplet state to a multilayer film. By using such excitable artificial membranes, it is possible to construct biodevices that mimic the functions of neurons and synapses.

The inventors of this application have proposed a biodevice utilizing the above-mentioned artificial membrane, as disclosed in Japanese Patent Application No. 63-96851 and Japanese Patent Application No. 63-192116. It is expected that it will be applied to

(Problem to be solved by the invention) However, in the conventional biodevice described above,
When changing the period to oscillate a short period to suit various information processing purposes, there is a problem in that in addition to the salt concentration difference mentioned above, direct current and external pressure must be added.

The purpose of this invention is to eliminate the need for external pressure necessary to perform short-period automatic oscillation and further reduce or eliminate the need for direct current. The objective is to provide a biodevice that can.

(Means for Solving the Problems) The present invention sets the pl+ of the salt solution on the low concentration side between the excitable artificial membranes formed by adsorbing lipids having oleyl groups to 4 or less, and thereby, the artificial membrane This eliminates the need for external pressure for automatic oscillation, and further reduces or eliminates the need for direct current.

(Function) As described above, the pH of the low concentration side of the excitable artificial membrane on both sides of the salt concentration is 4 or less, and when H in the solution on the low salt concentration side increases, the low salt concentration Diffusion of H occurs from the solution side to the high salt concentration solution side. As a result, the flow of cations from the high salt concentration solution side to the low salt concentration solution side is promoted, which is necessary for automatic oscillation to maintain electrically neutral conditions.

(Embodiments) Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

The lipid with an oleyl group used, dioleyl phosphate (DOPH), is oleyl alcohol (Kanto Kagaku ■
(manufactured by Kanto Kagaku ■) and phosphorus oxychloride (manufactured by Kanto Kagaku ■) by a conventional synthesis method, and the resulting synthetic substance was hydrolyzed.

The obtained DOP) was bathed in benzene, and a cellulose ester porous membrane (trade name, Millipore filter, manufactured by Millipore) having a pore size of 8 (am) was immersed in this solution. In this way, DOPI+4■/cI
An artificial membrane was prepared by adsorbing it onto a porous membrane at an adsorption amount of II (dry weight).

As shown in FIG. 1, the artificial membrane 11, the first electrolytic cell 1
100 mM KfJ aqueous solution 15a contained in 3a,
and a 5mM Kcf aqueous solution 15b housed in the second electrolytic cell 13b.

Silver-silver chloride (Ag-Agcz) electrodes 17a or 17b are immersed in the KC1 aqueous solutions 15a and 15b, respectively. And high concentration side MCI aqueous solution 15a
The electrode 17a immersed therein is connected to the anode side of the DC power source 19, and the electrode 17a immersed in the KC4 aqueous solution 15b on the low concentration side is connected to the anode side of the DC power source 19.
b is connected to the same cathode side. Furthermore, the above artificial membrane 1
In order to measure and record the time change of the potential difference applied to 1,
A measuring device 21 consisting of a high impedance electrometer and an X-Y recorder is provided, and its silver-silver chloride electrodes 23a and 2
3b is immersed in each of the above-mentioned KCI aqueous solutions 15a and 15b.

Further, a manometer 25 is disposed in the first electrolytic cell 13a, and is configured to be able to apply an external pressure indicated by an arrow a to the artificial membrane 11.

Automatic oscillation of the potential was measured when HCI was added to the 5mM KC4 aqueous solution in the electrolytic cell 13b and pl+ was changed.

FIG. 2 shows the relationship between the pH of a 5mM K(J aqueous solution and the external pressure and direct current required to produce automatic oscillation).

In addition, in the above measurement, when using pure water, starting with an MCI aqueous solution (pH 5,8), the initial DC current was 0.5.
It was kept fixed at μA, and the DC current was gradually reduced after external pressure was no longer needed.

As is clear from the results in FIG. 2, the oscillation initiation pressure was rapidly reduced as the pH decreased and became unnecessary when the pH reached 4. When the pH was further lowered, the direct current was also gradually reduced and became unnecessary at pH 2 and 5. pH2,
5 or less, oscillation occurs without the application of external pressure or direct current, and the frequency increases as pn is lowered.
At pH 1 or lower, the waveform changed to a disordered one.

FIG. 3 shows the oscillation waveforms at pH 2, 5 and pll. In this figure, the vertical axis is the membrane potential with the 5mMKC/aqueous solution side facing the aqueous solution side, but in the case of pH 5 and 8 (H
The sign is reversed from that in the case where C/ is not added.

Note that this sign reversal occurred at pn 3.5.

Various conditions in the above-mentioned embodiments may be arbitrarily modified and modified within the scope of the present invention. For example, for the above pH change, instead of HCI, other H2S04C1 (3C
A similar effect was observed using OOH and the like.

Regarding the lipid having an oleyl group to be used, monoolein or triolein may be used in addition to the above-mentioned dioleyl phosphate, and the same effects as described above can be obtained.

(Effects of the Invention) As explained above in detail, the present invention provides the following advantages: By adjusting the pH of the low concentration solution in contact with the artificial membrane made of adsorbing a synthetic lipid having an oleyl group, such as dioleyl phosphate, to 4 or less, Since the external pressure required to cause the artificial membrane to oscillate automatically is not required, and direct current can be reduced or eliminated, it is useful as a biodevice with great industrial effects.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of automatic oscillation of a biodevice according to an embodiment of the present invention, FIG. 2 is an explanatory diagram of the same characteristics, and FIG. 3 is a diagram of the same waveforms. 11... Artificial membrane, 13a, 13b... Electrolytic cell, 15
a, 15 b-KCI aqueous solution, 17a, 17b. 23a 23b... Electrode, a... Pressure.

Claims (2)

[Claims] (1) A biodevice characterized in that the pH of the low-concentration salt solution sandwiching the excitable artificial membrane formed by adsorbing a lipid having an oleyl group is set to 4 or less. (2) The bioelement according to claim 1, wherein the lipid is dioleyl phosphate, monoolein, or triolein.