METHOD AND ARRANGEMENT IN A GEL ELECTROPHORESIS APPARATUS

Abstract: In a gel electrophoresis apparatus having a light source (7), whose light beam (6) is to be introduced into an electrophoresis gel (1) through one of its lateral edges to enable detection of at least one component which is migrating in the electrophoresis gel (1) and which is labelled with a fluorescent substance, a means (8, 9) is adapted to sweep the laser beam (6) back and forth across said one lateral edge of the electrophoresis gel (1) to introduce the light beam into the electrophoresis gel (1) at different points of incidence, and a sensor (13, 14, 15) is adapted to measure the intensity of the light beam (6) introduced at said different points of incidence after that, it at least partially, has passed through the electrophoresis gel (1), and to lock the light beam (6) at the point of incidence at which the highest light intensity is measured.

Description: METHOD AND ARRANGEMENT IN A GEL ELECTROPHORESIS APPARATUS TECHNICAL FIELD The invention relates to a method and an arrangement in a gel electrophoresis apparatus having a light source whose light beam is to be introduced into an electrophoresis gel through one of its lateral edges to enable detection of at least one component which is migrating in the electrophoresis gel and which is labelled with a fluorescent substance. BACKGROUND OF THE INVENTION A problem with gel electrophoresis apparatuses, wherein a light beam, e.g. a laser beam, is introduced into the gel through one of its lateral edges, is that the light source, e.g. the laser, in connection with a gel change, has to be finely adjusted anew so that the light beam always ends up in the middle of the gel in order to give a maximum light dispersion in the gel without being guided in the glass plates located on either side of the gel which would reduce the possibility to detect the migrating components considerably. So far, this fine adjustment has been carried out manually in that the dispersion of light in the gel has been visually observed and that, hereby, it has been decided how the light source, i.e. the laser, should be directed in order to give the best possible dispersion of light in the gel. However, such a manual adjustment of the laser is difficult to carry out and, consequently, there is a certain uncertainty concerning whether the laser is optimally directed or not. BRIEF DESCRIPTION OF THE INVENTION The object of the invention is to eliminate the manual fine adjustment mentioned above and instead bring about a gel electrophoresis apparatus in which the fine adjustment is done automatically. forth across said one lateral edge of the electrophoresis gel to introduce the light beam into the electrophoresis gel at different points of incidence, that the intensity of the light beam introduced at said different points of incidence is measured after that it, at least partially, has passed through the electrophoresis gel, and that the light beam is locked at the point of incidence at which the highest intensity is measured. The object is attained by means of the arrangement according to the invention, mainly, in that a means is adapted to sweep the light beam back and forth across said one lateral edge of the electrophoresis gel to introduce the light beam into the electrophoresis gel at different points of incidence, and that a sensor is adapted to measure the intensity of the light beam introduced at said different points of incidence after that it, at least partially, has passed through the electrophoresis gel, and to lock the light beam at the point of incidence at which the highest intensity is measured. BRIEF DESCRIPTION OF THE DRAWING The invention will be described in more detail below with reference to the appended drawing on which the single figure, Fig. 1, schematically shows a block diagram of an embodiment of an arrangement according to the invention at an electrophoresis gel, a top end view thereof being shown. DESCRIPTION OF PREFERRED EMBODIMENTS Fig. 1 shows a top end view of a vertical electrophoresis gel 1 between glass plates 2 and 3 which are separated by means of spacers 4 and 5 which both are translucent in the embodiment shown. The shown gel 1 is intended for separation of a mixture of components, e.g. nucleic acids, and is, in a manner known per se, connected to an upper buffer liquid container (not shown) and a lower buffer liquid container (not shown) of an electrophoresis apparatus. Upon separation of nucleic acids, e.g. for sequencing, the samples thereof, labelled with fluorescent substances, are applied at the top end of the gel 1. Thereafter, the sample components migrate downwards in the gel 1 under influence of an electric field. At a predetermined location along the gel 1, a light beam which is a laser beam 6 in the embodiment shown, is introduced through the translucent spacer 4, and into the gel 1 through one of its lateral edges in order to enable detection of the above-mentioned samples migrating in the gel 1 by means of detectors (not shown) . In the embodiment shown, the laser beam 6 is generated by a laser 7 and introduced into the gel 1 by means of a mirror 8. To automatically adjust the laser beam 6 to give a maximum light-intensity in the gel 1, according to the invention, a motor 9 is provided to move the mirror 8 back and forth across the lateral edge of the gel 1 as indicated by arrow 10 in order to sweep the laser beam 6 back and forth across the lateral edge of the spacer 4 and, thereby, the gel 1 as indicated by means of arrow 11 in order to introduce the laser beam 6 into the gel 1 at different points of incidence. The motor 9 for moving the mirror 8 is actuated by means of a control unit 12 which is provided with a starting button (not shown) . The laser beam 6 coming from the mirror 8 passes through the gel 1 and exits, in the embodiment shown, from the gel 1 through its other lateral edge via the translucent spacer 5. In order to decide when the laser beam 6 is optimally directed, i.e. for which point of incidence the laser beam 6, exiting from the gel 1, exhibits a light-intensity maximum, a sensor 13 is provided at the other lateral edge of the gel 1, which sensor 13 is adapted to measure the light-intensity of the laser beam 6 during the sweeping motion of the laser beam 6, and produce a signal which is proportional to the light-intensity, and which is supplied to the control unit 12 which in its turn is adapted to stop the motor 9 and, thereby, the mirror 8 in the position for which the sensor 13 has measured the highest light-intensity of the laser beam 6. Hereby, the laser beam 6 is automatically set to the point of incidence for which the laser light, exiting from the gel 1, exhibits a light-intensity maximum. Gel electrophoresis apparatuses are also known, in which the laser beam is introduced into the gel from the laser via a spacer without any mirror. In such an embodiment, the motor corresponding to the motor 9 shown in the drawing, has to be adapted to move the laser instead of the mirror in order to introduce the laser beam at different points of incidence across one of the lateral edges of the gel. Above this, this embodiment (not shown) corresponds to the embodiment shown on the drawing. Measuring or sensing the light-intensity of the laser beam 6 does not necessarily have to be carried out in the manner shown on the drawing, i.e. with the sensor 13 located at the other lateral edge of the gel 1. As indicated by means of sensors represented by blocks 14 and 15, according to another embodiment, the sensor 14 can e.g. be adapted to measure the intensity of the light that is scattered by the spacer 5 in case this spacer is opaque, while the sensor 15, in accordance with a further embodiment, can be adapted to measure the intensity of the light scattered in the gel 1 after that the laser beam, at least partially, has passed through the gel 1. Thus, by means of the arrangement according to the invention, a gel electrophoresis apparatus has been obtained, in which the adjustment of the point of incidence of the laser beam 6 into the gel 1 is done automatically to give a maximum light-intensity in the gel 1.

Claims: CLAIMS 1. A method in a gel electrophoresis apparatus having a light source (7) whose light beam (6) is to be introduced into an electrophoresis gel (1) through one of its lateral edges to enable detection of at least one component which is migrating in the electrophoresis gel (1) and which is labelled with a fluorescent substance, characterized in - that the light beam (6) is swept back and forth across said one lateral edge of the electrophoresis gel (1) to introduce the light beam (6) into the electrophoresis gel (1) at different points of incidence, - that the intensity of the light beam (6) introduced at said different points of incidence, is measured after that it, at least partially, has passed through the electrophoresis gel (1) , and - that the light beam (6) is locked at the point of incidence at which the highest intensity is measured. 2. The method according to claim 1, wherein the light beam (6) is introduced into the electrophoresis gel (1) by means of a mirror (8) , characterized in that the mirror (8) is moved in order to sweep the light beam (6) across said one lateral edge of the electrophoresis gel (1) . 3. The method according to claim 1, characterized in that the light source is moved in order to sweep the light beam (6) across said one lateral edge of the electrophoresis gel (1) • 4. An arrangement in a gel electrophoresis apparatus having a light source (7) whose light beam (6) is to be introduced into an electrophoresis gel (1) through one of its lateral edges to enable detection of at least one component which is migrating in the electrophoresis gel (1) and which is labelled with a fluorescent substance, characterized in - that a means (8, 9) is adapted to sweep the light beam (6) back and forth across said one lateral edge of the electrophoresis gel (1) to introduce the light beam (6) into the electrophoresis gel (1) at different points of incidence, and - that a sensor (13, 14, 15) is adapted to measure the intensity of the light beam (6) introduced at said different points of incidence after that it, at least partially, has passed through the electrophoresis gel (1) , and to lock the light beam (6) at the point of incidence at which the highest intensity is measured. 5. The arrangement according to claim 4, wherein the light beam (6) is introduced into the electrophoresis gel (1) by means of a mirror (8), characterized in that said means is a mirror moving means (9) adapted to move the mirror (8) in order to sweep the light beam (6) across said one lateral edge of the electrophoresis gel (1) . 6. The arrangement according to claim 4, characterized in that said means is a light source moving means adapted to move the light source in order to sweep the light beam (6) across said one lateral edge of the electrophoresis gel (1) • 7. Arrangement according to any one of claims 4 to 6, characterized in that the sensor (13) is provided at the opposite lateral edge of the electrophoresis gel (1) in order to measure the intensity of the light beam (6) after that it has passed through the electrophoresis gel (1) . 8. The arrangement according to any one of claims 4 to 6, wherein the electrophoresis gel (1) is provided between glass plates (2, 3) which are separated by means of spacers (4, 5) along both lateral edges of the electrophoresis gel (1) , the spacer (4) through which the light beam (6) is introduced into the electrophoresis gel (1) being translucent, characterized in that the opposite spacer (5) is opaque and that the sensor (14) is adapted to measure the intensity of the light scattered by this spacer (5) . 9. The arrangement according to any one of claims 4 to 6, characterized in that the sensor (15) is adapted to measure the intensity of the light scattered by the electrophoresis gel (1) . 10. The arrangement according to any one of claims 4 to 9, characterized in that the light beam (6) is a laser beam.

Inventors: ANDERSSON BENGT GOERAN, SOWA STEFAN, ANDERSSON, BENGT, GOERAN, SOWA, STEFAN
Applicants: ANDERSSON BENGT GOERAN, PHARMACIA BIOTECH AB, SOWA STEFAN, ANDERSSON, BENGT, GOERAN, SOWA, STEFAN
Application year: 1995
Main classification: G01N27
IPC codes: G01N27