JPS6146780B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for measuring the electrophoretic velocity of visible suspended particles.

When an electric field is applied to a suspension of cells, the cells move due to the action of the electric field. Measuring this moving speed provides information for medical diagnosis, for example. For this reason, devices for measuring the electrophoresis of visible suspended particles have already been proposed.

When measuring the electrophoresis of suspended particles in places, there are the following problems. In Figure 1, 1 is an electrophoresis tube, 2 and 3 are electrodes, and particles are suspended in a solution filled in the tube 1, and a voltage is applied between the electrodes 2 and 3 to cause the particles to undergo electrophoresis, causing the particles to move. is observed optically. The electrophoresis tube is glass and the solution is aqueous.
When two types of conductive materials come into contact, a positive charge appears on the contact surface on the side with a larger dielectric constant, and a negative charge appears on the opposite side. In this case, since water has a higher dielectric constant than glass, negative charges appear on the inner surface of the electrophoresis tube 1, and positive charges appear on the surface of the aqueous solution in contact with the electrophoresis tube 1.
This positive charge occurs near the area where the H ⁺ ions (more precisely, H ₃ O ⁺ in which H ⁺ combines with H ₂ O molecules) generated by the dissociation of water are in contact with the inner surface of the electrophoresis tube 1 in the solution. It appears by coming together. When a voltage is applied between the electrodes 2 and 3, the positive ions described above are drawn toward the negative electrode 2, and the solution in the layer that is in contact with the inner surface of the electrophoresis tube 1 flows to the left. do. Since the total amount of movement of the solution in any cross section of the electrophoresis tube 1 must be 0, a flow to the right is formed near the center of the tube 1, and the solution in the tube 1 performs convection as shown by the arrows in the figure. . This convection is called electroosmotic flow. Floating particles perform electrophoresis while flowing along with this convection current, so to measure the correct electrophoresis speed, focus the optical system on the layer in tube 1 where the electroosmotic flow has a flow rate of 0 and observe electrophoresis. There is a need. However, since this layer cannot be seen concretely, the position of the layer is estimated by calculation based on appropriate assumptions, and the optical system is focused on that position. This calculation is performed on the assumption that, for example, when the tube 1 has a circular cross section, the cross sections of the leftward flow and rightward flow of the electroosmotic flow are equal. However, it is unclear whether the layer defined by this assumption truly has an electroosmotic flow velocity of 0, and it is not easy to make appropriate assumptions for calculations when the cross section of the pipe is not circular. .

The present invention has been made with the object of providing a method for solving the above-mentioned problem of electroosmotic flow.

The present invention forms an electrode layer on the outer surface of an electrophoresis tube,
By changing the voltage applied to this electrode layer, the amount of charge appearing on the inner surface of the tube and the surface in contact with the solution is changed, thereby changing the strength of the electroosmotic flow. Measuring the moving speed of suspended particles, calculating the ratio of the particle moving speed of the same layer before and after changing the voltage of the electrode layer,
The moving speed of the layer where this ratio becomes 1 is determined. The shape of the flow velocity distribution of the electroosmotic flow is constant regardless of the strength of the electroosmotic flow, so the layer where the ratio of the particle movement velocity before and after changing the speed of the electroosmotic flow is 1 is between before and after changing the voltage applied to the electrode layer. This is the layer where the flow rate of the electroosmotic flow does not change, and the layer where the electroosmotic flow does not change is the layer where the electroosmotic flow is 0, so the moving speed in this layer is the true electrophoretic speed. The present invention will be explained below with reference to Examples.

FIG. 2 shows an embodiment of the present invention. Reference numeral 1 denotes an electrophoresis tube, 2 and 3 electrodes for causing electrophoresis in suspended particles, and 4 a transparent electrode layer formed on the outer surface of the electrophoresis tube 1 to cover the outer surface of the tube 1. 5 is a laser light source, and 6 is a condensing lens that converges a laser beam into the tube 1 in a long line in the tube axis direction. A projection lens 7 focuses on the convergence line of the laser beam and forms an image of that point on the grating 8. Laser light source 5
The parts from to the grating 8 are mounted on one pedestal 9 so that the convergence line of the laser beam can move in one radial direction within the electrophoresis tube 1.
The voltage applied to the electrode 4 can be switched between two types, 0 and a constant value, by a switch S. A light-receiving element 10 is placed behind the grating 8, and its output is sent to a frequency analysis circuit 11, where the spectral distribution of the output of the light-receiving element 10 is determined. This spectral distribution is stored in memory M.

Images of floating particles illuminated by the convergence line of the laser beam are formed as bright spots on the grid 8, and move on the grid as the particles move. Therefore, the amount of light transmitted through the grating 8 changes periodically as particle images are hidden by the grating lines or appear between the grating lines. Since there are many floating particle images, and their moving speeds vary slightly, the output of the light-receiving element 10 is not a single-cycle waveform, but an irregular waveform in which waveforms with various cycles overlap. Therefore, when the frequency distribution spectrum is obtained using a frequency analysis circuit, it represents the moving velocity distribution of the suspended particles.

While moving the pedestal 9, perform the above measurement operation every fixed amount of movement, store the spectrum observed at that time in the memory M, and repeat the same operation twice by opening and closing the switch S to correspond to the same pedestal position. If the two spectra before and after are read out from memory and their shapes are compared, and the one that most closely matches is found, that represents the true electrophoretic velocity distribution of suspended particles.

Another method for processing measurement results in the above-mentioned apparatus is to determine the movement velocity of suspended particles at only three positions in the radial direction within the electrophoresis tube 1, and to measure the movement of particles at the three positions before and after applying a voltage to the electrode 4. By interpolation or extrapolation from the velocity, find the moving speed at a point where the particle moving speeds in both cases match. FIG. 3 shows the procedure for carrying out the operation diagrammatically. p1, p2, p3 are floating particle movement speeds (average) at three positions before applying voltage to electrode 4;
q1, q2, and q3 are the moving speeds at the same position when a voltage is similarly applied to the electrode 4. p1~p
When the intersection point f of one curve connecting 3 and one curve connecting q1 to q3 is found, the velocity v with respect to f is the true electrophoretic velocity. This operation can also be performed by calculation. Since the lines connecting p1 to p3 and q1 to q3 are each quadratic curve, each can be determined by three points. If the number of points is increased by one more, the method of least squares can be applied, which further improves accuracy, and these calculations can be performed by a computer.

In the above embodiment, the electrode 4 on the outer surface of the electrophoresis tube 1 is a transparent electrode, but when it is a plated metal electrode, a small window for illumination and observation may be provided.

With the electrophoresis measuring device of the present invention having the above-described configuration, the moving speed of suspended particles in a layer with zero electroosmotic flow can be determined not simply by mere estimation, so that accurate electrophoretic speed can be determined.

[Brief explanation of the drawing]

FIG. 1 is a side view of an electrophoresis tube, FIG. 2 is a perspective view of an apparatus according to an embodiment of the present invention, and FIG. 3 is a graph illustrating a measurement result processing method. DESCRIPTION OF SYMBOLS 1... Electrophoresis tube, 2, 3... Electrode, 4... Electrode layer on the outer surface of the electrophoresis tube, 5... Laser light source, 6...
... Condensing lens, 7... Projection lens, 8... Grid,
9... Mount, 10... Light receiving element, 11... Frequency analysis circuit, M... Memory.

Claims (1)

[Claims] 1 Cover the outer surface of the electrophoresis tube with an electrode layer, make it possible to change the voltage applied to this electrode layer, and align the viewing position inside the electrophoresis tube of the optical device for observing suspended particles inside the electrophoresis tube with the tube axis of the electrophoresis tube. Electrophoresis measurement device that can be moved in the right angle direction.