GEL CELL AND APPARATUS FOR GEL ELECTROPHORESIS

Abstract: A cell gell for performing gel electrophoresis that comprises gel chamber defined by transparent walls open at one end, in which a buffer chamber (20) is coupled to and built integrally with the gel chamber (12), the chambers (12 and 20) are made of a thermoplastic material, the buffer chamber (20) has an inner storage space substantially larger in volume than the interior of the gel chamber (12) and the storage space communicates through a transitional section to the open end (15) of the gel chamber (12). An apparatus has also been provided for gel electrophoresis by using this gel cell, which comprises a tank (31) with transparent walls having an internal space in which a gel cell is arranged with vertically extending gel chamber, a coil pipe (34) is arranged around the gel chamber (12) having a height substantially equal to that of the gel chamber (12), a first buffer solution is stored in the buffer chamber (20) of the gel cell (10) and a second buffer solution is in the tank (31) around the gel cell (10), this buffer solution is connectable through respective electrodes to a gel electrophorising circuit.

Description: GEL CELL AND APPARATUS FOR GEL ELECTROPHORESIS The invention relates to a gel cell for performing gel electrophoresis which comprises a gel chamber defined by transparent walls open at least at an end section. The invention relates also to a novel gel electrophoresis apparatus in which the gel cell can be used. The gel cell and the apparatus are the type by which vertical gel electrophoresis can be made. It is known in the art that for performing vertical gel electrophoresis a number of conditions should be provided. The first and often the most significant task lies in the preparation of the gel body which is generally made in the form of a gel sheet. The gel body is used during gel electrophoresis to carry and hold the sample to be examined. In addition to this task the storage and the mechanical support of the gel body should be solved. The electrophoresis can be carried out if two opposing end sections of the gel body are exposed to respective buffer solutions between which a complete isolation should be provided, and when the electrophoresis is completed, an access to the gel body should be made which step should not cause any damage to the delicate structure of the gel body. These tasks can be solved by several known ways. Most of these have the common characteristic of making the gel body in a gel chamber defined by glass walls, and when the gel body has solidified, the lower end portion of the chamber is opened e.g. by removing a lower sealing, whereafter the open upper and lower ends of the flat rectangular gel chamber are exposed to respective upper -and lower buffer solutions by using special sealings for appropriate isolation between the buffers. There are different ways of coupling the buffer solutions to the gel body. In a widely used embodiment a face of the gel chamber made of glass plates is pressed to th side wall of a glass tank containing the upper buffer solution and a sealing is provided between the two adjacant glasses. The gel chamber and the liquid in the tank communicate through appropriate upper recesses made in the side wall of the tank and of the gel chamber, respectively. The so obtained arrangement is then inserted in a larger tank containing the lower buffer solution which is communicating with the lower opening of the gel chamber. In this embodiment the establishment of a sealed connection between the gel chamber and the first tank is a labor-intensive activity and the construction cannot provide an appropriate cooling for the inner wall of the gel chamber which is pressed to the side wall of the first tank. The next problem arises when the electrophoresis process has finished, because the arrangement should then be disassembled and the gel body should be removed from the gel chamber. To this end the gel chamber made of several glass plates should be teared open, while attention should be payed for preventing the gel body from being damaged. The parts and accessories can be re-used after being washed, sterilized and re-assembled. Most of the known gel electrophoresis equipment operate according to the principles described hereinabove, the difference between them lies mainly in the actual design and not in the basic way of operation. Typical examples for illustrating the state of this art are described in the German patent No. 2,640,892, the apparatus Type: LK8-2001 of the Swedish company LKB, the British patent No. 1.577.712 and the U.S. patents 4.224.134; 4.290.871 and 4.292.161. The object of the invention is to provide a gel cell and an apparatus for gel electrophoresis which does not require the labor demanding assembly of the parts, which simplifies the connection of the two buffer solutions with the gel body, facilitates, the access to the gel body and which results in an increase in quality of the gel electrophoresis process. These objects can be solved by utilizing the recognition that the whole process of the gel electrophoresis starting from the prepartion of the gel up to the removal of the gel body from the gel chamber following the electrophoresis can be made in a single location by using a disposable gel cell intended for a single use, and the sealed connection to the buffer solutions will be automa ically provided if the gel cell comprises a gel chamber ' and a buffer chamber connected to and forming an integral part with the gel chamber. In this way the gel cell consists of two main and integral parts i,e # of the gel chamber and the buffer chamber defining respective inner spaces which a rt} communicating with each other through the upper opening of the gel chamber. The gel cell can be made of a transparent thermoplastic material. The term "transparent" designates a property which enables that the inner processes can be visually inspected through the walls, i.e. the walls need not be physically as transparent as normal glass generally is. Preferably the gel chamber po prises planar rear and front walls and reinforced i.e. thicker side walls. The width of the buffer and gel chambers can preferably be the same, and the spacing between the rear and front walls of the gel chamber is at least with a decimal order of magnitude smaller than the distance between the two side walls. The opening of the gel chamber is facilitated if the rear and front walls approaching each other in a lower . end zone and they get united in a common lower edge closure. The required lower opening can simply be made by cutting this edge closure. In a preferable embodiment more than one gel chambers can be connected to a buffer chamber. The required parallel and planar shape of the gel body is defined by the # geometrical form of the inner walls of the gel chamber. The planar and parallel form can be ensured by providing appropriate reinforcement ribs in these walls, however, the same condition can be met if instead of using increased wall thickness, a reduced thickness is used and respective glass plates are attached outwardly to the rear and front walls of the gel chamber which determine the shape of the thin and resilient walls. According to the invention a gel electrophoresis apparatus using the novel gel cell has also been provided which comprises a tank with transparent walls defining an interior in which at least one gel cell made according to the invention is arranged with vertically positioned gel chamber, and a coil pipe is arranged around the gel ' chamber in which a cooling liquid can be circulated, the height of the coil pipe is substantially equal to that of the gel chamber, and the buffer chamber of the gel cell comprises a first buffer solution, while the tank comprises a second buffer solution which solutions are conπectable through respective electrodes to an electrophoresis circuit. For optimum utilization of the buffer solutions it is advantageous if the space available in the tank for the second buffer solution is substantially equal to the combined volume of the first buffer solutions ' in the buffer chambers of all gel cells in th ' e tank. The term "equal" should not be interpreted with mathematical accuracy, it is sufficient if they a re in a tolerance range of -10 to +50 per cent. The hydrostatic pressure difference acting on the gel body will cease to exist if during operation the level of the two buffer solutions is equal. The invention will now be described in connection with preferable embodiments thereof, in which reference will be made to the accompanying drawings, In the drawing: FIG. 1 shows the perspective view of the first embodiment of the gel cell according to the invention, FIG. 2 shows the perspective view of a second preferable embodiment, FIG. 3 shows the perspective view of a third preferable embodiment, and FIG. 4 shows the perspective view of the apparatus for gel electrophoresis using the gel cell shown in FIG. 1, partly in section. Fig. 1 shows the perspective view of a first embodiment of a gel cell 10 made according to the invention. The gel cell 10 is made as a single piece of a thermoplastic material su-ch as polyvinyl-chloride, polycarbonate, polystyrene, ethacrylate or of a similar plastic material and it can be divided into two main parts i.e. gel chamber 12 and buffer chamer 20. These parts are directly connected and mutually form the extensions of each other, The gel chamber 12 has a flat prismatic shape defined by a pair of narrow side walls 13 and a respective rear and a front wall 14 which are normal to the side walls 13. Between the walls a flat rectangular internal room is defined which is closed at the bottom. Downwardly over the lower edge of the internal room the walls 14 gradually get closer in an arcuate and narrow edge zone 18 and meet along a closing edge 19. The buffer chamber 20 is arranged above the gel chamber 12 symmetrically to the vertical central plane thereof. The interior of the buffer chamber 20 has a rectangular form and it is just as long as the internal room of the gel chamber 12 but it has a much higher width. In the lower part the buffer chamber 20 gradually narrows and finally its internal space reaches the internal space of the gel chamber 12. The two internal spaces communicate through a common narrow opening 15 (dashed line in Fig. 1). The buffer chamber 20 has vertical walls limited by a horizont flange 27 which is adapted to reinforce the gel cell 10 and to form a mounting support. The two side walls 23, 24 of the buffer chamber 20 are the extensions of the side walls 13 of the gel cell 12 and define respective central recesses 25 and 26. The recesses 25 and 26 are open towards the interior of the buffer chamber 20 and they have the task of mechanically supporting an electrode immersed in a buffer solution filling the buffer chamber 20 during operation. A transition zone is formed between the buffer chamber 20 and the gel chamber 12 which has preferably a slightly arcuate form as shown in the drawing, however, it can be preferable in certain applications if the transition zone is made by a sudden bellying section just above the opening 15 which is followed by a steeper section to reach the vertical walls of the buffer chamber 20. The gel cell 10 should be made of a transparent or at least semi-transparent plastic material, thus the gel electrophoresis can be visually inspected. Regarding the structural design of the gel chamber 12 it is of high significance that the walls 14 of the gel chamber 12 be strictly parallel to each other. The parallel structure can be made in several ways. In a preferable embodiment the rear and front walls 14 comprise outer reinforcement ribs. The thickness of the wall material is much greater at the side walls 13 than at the rear and front walls, therefore the ribs will be sufficiently supported at their end sections if they reach to the s ' ide walls. Fig. 2 shows an other embodiment for the reinforcement of the walls of the gel chamber 12. The structural design of this gel cell 10 is functionally identical with that shown in Fig, 1, the difference lies only in the much thinner design of the front and rear walls 14 of the gel chamber 12. Such a small wall thickness allows the flexible and resilient, displacement of the walls. In this embodiment the thickness of the side walls 13 is also much greater than that of the other walls 14, The reinforcement is made by separate outer glass plates 16 and 17 which can be releasably attached to the gel chamber 12 by means of clamps 21 and 22 and bolts 28 made preferably of a plastic material. During gel formation the inner space of the gel chamber 12 is filled by a gel-forming liquid and owing to the hydrostatic pressure of the liquid the resilient walls 14 get pressed to the glass plates 16, 17 and take their planar form. When the gel-forming process has finished, the solidified gel body will keep the planar form. Obviously, plastic plates can well be used instead of the glass plates. Depending on the intended use the size of the gel chamber 12 can vary in a wide range. For the electrophoresis of proteins the internal size of 2 x 150 x 150mmispreferable, while for the electrophoresis of nucleotic acids, polypeptids and polynucleotids the size of 1 to 2 mm x x 300 x 600 mm is more preferable. The embodiment shown in Fig. 2 is particularly useful in case of larger gel chambers, since with increasing size the technical problem of providing parallel walls gets more and more difficult. Reference is made now to Fig. 3 showing a further embodiment of the gel cell according to the invention. This gel cell 30 has a buffer chamber 20 which is connected to a pair of gel chambers 11 and 12, therefore it is capable of performing two gel electrophoresis at a time. The gel cell with double gel chamber has otherwise a similar design to the embodiment shown in Fig. 1, The gel chambers 11 and 12 can have reinforced walls, or the reinforcement by means of the outer glass plates can be used in the twin embodiment, too. When the gel cell according to the invention is used, it is preferable if first the gel body is made, and for that purpose a gel-forming liquid is filled in the gel chamber through the buffer chamber 20 when the gel chamber is kept in vertical position, and in given cases a sample forming comb can be inserted through the opening 15. Before the starting of the gel electrophoresis the lower edge of the gel chamber should be opened. This can be done e.g. by cutting the walls 14 in the edge zone 18. In this zone the distance between the opposing walls is very small and the cutting can be made by means of scissors or any other appropriate cutting means. The cutting step can be facilitated if in the edge zone 18 respective grooves are made which should extend parallel to the closing edge 19. When the closing edge 19 is removed, a lower access opening is obtained towards the gel body. At this tiπre respective samples can be inserted in the pre-for ed locations in the gel body and the gel electrophoresis can be started. For performing the gel electrophoresis the use of the apparatus shown in Fig. 4 is considered to be preferable. •Referring now to Fig. 4 showing an oblong-shaped tank 31 with transparent walls and comprising a pair of gel cells 10a and 10b in a side by side arrangement. A transparent cover 32 is used for closing the tank 31, and in the inside of the cover 32 icroswitches 33 (shewn schematically only) are arranged which establish a closed electrical circuit for the electrophoresis when the cover 32 is in operational (closed) position. The gel cells 10a and 10b are supported by means of their flanges 27 * oπ upper edges of the walls of the tank 31. In the interior of the tank 31 a coil pipe 34 is arranged around the gel chambers supported by a plurality of spaced support plates 35 comprising respective bores for the respective coil windings. The ends of the coil pipe 34 are extending out of the tank 31 and they are connected to a cooling liquid circulating means. The height of the coiled pipe 34 is substantially identical with that of the gel chambers of the gel cells. In the bottom of the tank 31 in a section between the two gel chambers an electrode support 35 is arranged for receiving a cemmon electrode required for the elec rop oresis. The gel electrophoresis can be performed by the apparatus shown in Fig. 4 as follows. The preparation of the gel cells should be made as described hereinabove. When the samples are placed in the gel bodies, the gel cells are inserted in the tank 31 as shown in Fig. 4. The interior of the tank 31 is filled by a lower buffer liquid while the buffer chambers 20 of the gel cells are filled by an upper buffer liquid. With appropriate dimensioning the combined volume of the upper buffer liquid is substantially the same as the volume of the lower buffer liquid, and the level of the lower liquid is just as high as that of the upper one. With such conditions no hydrostatic pressure difference will act on the gel bodies in the open gel chambers. Upper electrodes should be inserted in the upper buffer chambers while the common electrode should be mounted on the electrode support 36. By closing the cover 32 the electrophoretic circuit can be switched on. A cooling liquid (water) is now circulated through the coil pipe 34. The gel electrophoretic process can be visually watched through the transparent gel-electrophoresis apparatus. With the described way of cooling and optimum dimen'sions both faces and sides of the gel chambers will be exposed to a uniform cooling effect and even the heat generated in the upper buffer chamber will be removed through the thin wall of the chamber. The cooling effect can be increased by using a magnetic mixing equipment (not shown in the drawing). Owing to the evenly distributed cooling the well known edge effects or smiling effects present in conventional electrophoretic apparatuses will not take place and the electrophcsesis can be carried out under even circumstances. When the gel electrophoresis is finished, the gel cells 10a and 10b are removed from the tank 31, and after removal of the upper buffer solutions and of the upper electrodes, the internal space of each gel chamber 12 is opened. This step can be performed by cutting the walls near to the side walls 13. The gel body can be easily removed from the gel chamber when it is cut along its two sides, because to this end one or both of the walls 14 should only be turned up and then a sufficiently large opening is obtained through which the gel body can be removed without the danger of being damaged. The gel cells according to the invention are means intended to a single use only and this property forms one of their largest advantage. The use of such cells enables the preparation of the gel body, the formation of appropriate nests for receiving the samples, by cutting the lower edges of the gel chamber the gel cell is ready for performing gel electrophoresis and before this step the cell can be used for storing the gel body. A further advantage lies in that the gel cell provides space for receiving the upper buffer solution, whereby the connection between the upper buffer solution and the upper side of the gel body is automatically established without the presence of the well known problems connected with the watertight sealing of the conventional gel chambers. During the electrophoretic process the double-sided access of the cooling agent, to the gel chamber is also preferable, since this ensures an even cooling effect. A further advantage lies in that there will be no hydrostatic pressure differences that would urge the gel body to slip out of the gel chamber. The samples can be easily and hygienically stored and transported in the gel chamber following the gel electrophoresis without the danger of being damaged or doped, The disposable design of the gel cell according to the invention provides additionally a substantial saving in labour compared to conventional technique. These advantages will take place not only in case of the actual and preferable embodiments described nereinabove, and a number of modifications can be mad e relative to these embodiments without departing from the scope and spirit of the present invention. In this regard e.g. the electrophoresis can well be carried out if a gel cell with double gel chamber is used in the tank 31, or if the interior of the tank is divided into separate parts with different sizes, several different gel cells can be used for gel electrophoresis simultaneuously or alternately by using the same tank.

Claims: Claims •1. A gel cell for performing gel electrophoresis, comprising a gel chamber defined by transparent walls and being open at one end, c h a r a c t e r i z e d in that a buffer chamber (2θ) is coupled to and built integrally with said gel chamber (12), said chambers (12 and 20) being made of a thermoplastic material, said buffer chamber (2θ) having an inner storage space substantially larger in volume than the interior of the gel chamber (12) and the storage space is communicating through a transitional section to the open end (15) of the gel chamber (12). 2, The gel cell as claimed in claim 1, c h a r a c t e r i z e d in that the gel chamber (12) being defined by planar rear and front walls (14) and a pair of side walls (13) substantially thicker than the rear and front walls (14), and the side walls (13) being spaced by a spacing which is at least by a decimal order of magnitude higher than the spacing between the rear and front walls (14), 3. The gel cell as claimed in claim 2, c h a r a c t e r i z e d in that the rear and front walls (14) of the gel chamber (12) approaching each other in an edge zone (18) opposite to the open end and being united along an edge (19) closing the interior of the gel chamber (12). 4. The gel cell as claimed in any of claims 1 to 3, c h a r a c t e r i z e d in that the buffer chamber (20) and the gel chamber (12) having a common width. 5. The gel cell as claimed in any of claims 1 to 4, c h a r a c t e r i z e d in that the buffer chamber (20) comprising a flange (27). 6. The gel cell as claimed in any of claims 1 to 5, c h a r a c t e r i z e d in that the side walls of the buffer chamber (2θ) define respective recesses (25,26) open from above for receiving and supporting an electrode for the electrophoresis. 7. The gel cell as claimed in any of the claims 1 to 6, c h a r a c t e r i z e d in that more than one gel chambers (11,12) being integrally coupled to the buffer chamber (20). 8. The gel cell as claimed in any of the claims 2 to 7, c h a r a c t e r i z e d in that the rear and front walls (14) of the gel chamber (12) having a uniform and reduced thickness, and these walls (14) being operatively supported by outer planar plates, preferably glass plates (16,17). 9. The gel cell as claimed in claim 8, c h a r a c t e r i z e d in that the plates (16,17) being attached to the gel chamber by means of clamps (21,22) and releasable fixing means, such as bolts (21,22) said clamps encasing the side walls (13) of the gel chamber (12). 10, An apparatus for carrying out gel electrophoresis by using the gel cell as claimed in any of claims 1 to 9, c h a r a c t e r i z e d in that the apparatus comprises a tank (31) with transparent walls having an internal space in which a gel cell is arranged with vertically extending gel chamber, a coil pipe (34 ) being arranged around the gel chamber (12) having a height substantially equal to that of the gel chamber (12), a first buffer solution being stored in the buffer chamber (20) of the gel cell (10) and a second buffer solution being arranged in the tank (3l) around the gel cell (lθ), said buffer solutions being connectable through respective electrodes to a gel electrophorising circuit, 11. The apparatus as claimed in claim 10, c h a r a c t e r i z e d in that the internal space of the tank (31) for receiving the second buffer solution being substantially the same as the storage place provided in the buffer chamber or chambers (20) for the first buffer solution. 12. The apparatus as claimed in claim 10, c h a r a c t e r i z e d in that in operation both of said buffer solutions have a substantially common level. 13. The apparatus as claimed in claim 10, c h a r a c t e r i z e d in that the flange (27) of any gel cell (10) inserted in the tank (31) being supported by upper edges of the side walls of the tank (31).

Inventors: BALINT MIKLOS, TOEROEK GABOR, BALINT, MIKLOS, TOEROEK, GABOR
Applicants: LICENCIA TALALMANYOKAT, LICENCIA TALALMANYOKAT ERTEKESITOE ES INNOVACIOS
Application year: 1985
Main classification: G01N27
IPC codes: G01N27