Chemistry: electrical and wave energy – Apparatus – Electrophoretic or electro-osmotic apparatus
Reexamination Certificate
1998-03-23
2001-01-30
Warden, Jill (Department: 1743)
Chemistry: electrical and wave energy
Apparatus
Electrophoretic or electro-osmotic apparatus
C204S618000, C425S451900
Reexamination Certificate
active
06179980
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention concerns a device for use in electrophoresis.
2. Description of the Background Art
In an electrophoresis process a gel is subjected to a high electric tension on at least two sides. The applied tension results in migration of the molecules in the gel, a shorter or longer distance depending on, for example, the electric charge of the molecules. Hereby the movement direction of the molecules is always perpendicular to the equipotential lines, i.e. lines having the same potential in the gel. Totally decisive for a reliable result in respect of detection of separated molecules, is that the equipotential lines are straight and parallel, since otherwise erroneous detection occurs. Possible leaks from the gel enclosure thus result in electric contact between the gel and a liquid bath put under tension, resulting in sideward current leaks, curved equipotential lines and “curved migration” of molecules.
While forming the gel in the gel enclosure, it is further essential to obtain as homogeneous and even thick a gel as possible since also variations in the gel thickness result in undesired deviations from accurate equipotential line paths.
Known devices of the previously mentioned kind unfortunately suffer from the above discussed problems at a smaller or greater extent. As examples of devices which to date are used for clamping gel slab assemblies, those may be mentioned which clamp together the gel unit using screw fasteners, whereby a number of screw means which are distributed over the side edge are arranged to exert the desired pressing force. These previously known devices, however, have not satisfactory solved the problems in question, since an inherent adjustment variation exists because of the individually tightened screw means. This is also the case if the screws, as in certain cases, have been tightened with a torque indicator.
Another known device is applied by two jaw portions being pressed over the edge of the gel assembly by means of an eccentric mechanism. Also this device, however, suffers from problems related to exerting even pressure. A further problem is that of sideward movement, which may occur in connection with the tightening of the eccentric, and which may result in an undesired mutual sideward movement between the glass plates which are parts of the assembly. A further problem is insufficient clamping force, which results in the above discussed sideward leakage, particularly when forming the gel.
U.S. Pat. No. 4,035,377 concerns a slab gel electrophoresis apparatus having clamps of the paper clamp type for holding the plates together. The lengths of the clamping portions are such that an untrained person by mistake can apply the clamping force inside the spacing strips. The clamps are applied by a lateral movement over the plates, leading to possibility of inexact positioning and force distribution. The large dimensions of the clamps makes it necessary to remove some of them when carrying out the electrophoresis process.
SUMMARY OF THE INVENTION
It is an object of this invention to provide a device which solves the above discussed problems in a simple, reliable, space saving and cost effective manner.
In this way, a device is provided that is simple to manufacture, that may be applied also by untrained personnel and still achieve accurately directed clamping force of a desired magnitude. It is further assured that pressing is exerted within the width of a spacing strip, which is essential, since pressure on the non-conductive transparent plates beside a spacing strip, i.e. over the actual gel enclosure, results in a bending movement on at least one of the plates and thus an undesired deformation of the gel enclosure. By the clamping means being dimensioned to deliver the desired clamping force in the applied position, problems related to erroneous tightening, unevenness, etc. are avoided. The exact clamping force to be exerted is easily tested by a person skilled in the art.
Different materials may be used for the clamping means. Stainless steel is preferred but also other metals may come into question as well as certain synthetic materials, particularly reinforced ones, such as so-called construction plastic materials.
The feature that one of the shank portions constitutes a hinge portion for cooperation with a groove-like recess in a supporting frame of the gel slab assembly, simplified orientation and mounting of the clamping means, particularly in electrophoresis systems according to the state of the art where the frame is provided with a groove-like recess.
It should be noted that this invention concerns continuous detection during the migration of the molecules in an equipment using laser-beams in as thin a gel slab as possible, typically 0.3-0.5 mm, which raises far stricter demands with respect to tightness of the assembly. This because of curved migration being even more critical in thin gel slabs. Leaks due to uneven force distribution result in curved equipotential lines and may lead to poor results. This is accentuated in an electrophoresis system relating to this invention.
The invention brings about the possibility of simplified manufacture of the clamping means using in per se known, conventional methods. Plate material means initially slab or band shaped metal material, and as indicated above, stainless steel is preferred.
The invention provides further facilitated handling and ensures that a necessary clamping force is safely obtained which is distributed along the edge of the assembly. In this way the risk of applying a wrong number of clamping means onto the assembly is eliminated.
The invention also concerns electrophoresis systems. Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
REFERENCES:
patent: 3256577 (1966-06-01), Bright
patent: 4035377 (1977-07-01), Detroy
patent: 4518476 (1985-05-01), Delony et al.
patent: 4817253 (1989-04-01), Harmatuik et al.
patent: 4820398 (1989-04-01), Yamato
patent: 4985128 (1991-01-01), Ebersole et al.
Amersham Pharmacia Biotech AB
Birch & Stewart Kolasch & Birch, LLP
Noguerola Alex
Warden Jill
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