Abstract:
A device and method enables rapid gel casting and two-dimensional electrophoresis of a gel matrix. Agarose gel liquid is poured directly onto a flat metal surface for rapid instant formation of gel matrix. An open frame without bottom plastic anchors the gel matrix for easy handling. Electric pathways are reserved to 4 sides of the gel matrix, which permits the gel matrix being used in 2 orientations.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates in general to devices and methods of gel electrophoresis, and in particular, to devices and methods of gel casting in submarine gel electrophoresis.  
       BACKGROUND OF THE INVENTION  
       [0002]     Gel electrophoresis is one of the most frequently utilized tools for biomedical researches and industries. In gel electrophoresis, samples are loaded into a plurality of sample wells of a gel matrix. Charged molecules in loaded samples migrate from sample wells into gel matrix when electric field being applied. Different molecules migrate in different rates and appear as distinguishable bands in gel matrix. By placement of gel matrix, gel devices and methods have been classified into horizontal gel electrophoresis and vertical gel electrophoresis. Submarine gel electrophoresis is one of the most popular formats of horizontal gel electrophoresis. In which gel matrix is completely immersed under running buffer.  
         [0003]     Agarose is the most popular gelling chemical utilized in submarine gel electrophoresis. In gel casting, the first step is to boil gel solution for dissolving agarose powder. Then the hot agarose gel liquid cools down slowly and solidifies as gel matrix.  
         [0004]     As a liquid, hot agarose gel solution flows randomly. To control gel dimension, a variety of gel trays and gel casting stands has been used to establish a sealed enclosure for holding the gel liquid. A typical gel tray is made with plastics in “U” shape having a flat bottom and 2 longitudinal sidewalls. Two open ends of the gel tray are reserved as electric pathways of gel matrix to electrodes of a submarine gel apparatus. During gel casting, the two open ends are sealed by tape or casting stand. Gel liquid leakage is sometimes a problem when the sealing fails. To overcome leaking problem, Hsu, in U.S. Pat. No. 6,576,109, teaches a leaking free device for gel casting using a gel tray, stop members, and stop plates.  
         [0005]     In applications, gel electrophoresis projects vary from time to time. For a PCR sample screening experiment, for example, a gel tray with extra wide width and short length is desired. In genome project, a gel tray with extra long length is essential. To meet such diversified needs, many sets of gel electrophoresis systems will be accumulated in laboratories. One set for one purpose only.  
         [0006]     After decades with the tradition of using gel tray in submarine gel electrophoresis, some basic questions are forgotten:  
         [0007]     Why gel trays are used in only one orientation? 
         [0008]     Why gel trays have to be sealed for gel casting? 
         [0009]     Why wasting time in slow cooling down of gel liquid? 
         [0010]     These basic questions lead to the creation of open frame gel casting, a unique concept and strategy different from current understanding of gel casting.  
         [0011]     Frame is a simple rectangular structure existing in our daily life, such as picture frames on the wall. In submarine gel electrophoresis field, White et al, in U.S. Pat. No. 6,106,686, teaches a frame to seat over a precast gel matrix during electrophoresis process to prevent gel slab from floating. White et al limits, unfortunately, his frame within electrophoresis process only and fails to discover novel function of a frame for gel casting. White et al emphasizes in claims that his frame support member should seat on top of the gel slab without penetrating or lacerating the gel slab. White et al also fails to explain how to manufacture his precast gel. White et al further fails to teach his gel slab for 2-orientation electrophoresis.  
         [0012]     In brief, current understanding of gel casting is limited within the concept of using gel trays and sealing means for submarine gel electrophoresis.  
       SUMMARY OF THE INVENTION  
       [0013]     It is, therefore, an object of the invention to introduce a simple concept and strategy for generating novel device and method of gel casting in submarine gel electrophoresis. The advantages of the device and method are:  
         [0000]     (1) It works faster. Hot agarose gel liquid solidifies instantly on metal plate.  
         [0000]     (2) It gains flexibility. One casting device used to form either a portrait gel or a landscape gel.  
         [0000]     (3) It simplifies gel casting device and operation. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]      FIG. 1  is a perspective view of an embodiment of the invention.  
         [0015]      FIG. 2  is a cross sectional view of an enlarged diagram illustrating an anchoring structure of the embodiment during gel casting.  
         [0016]      FIG. 3  is a perspective view of a gel matrix being hooked onto the embodiment.  
         [0017]      FIG. 4  is a cross sectional view of a submarine gel apparatus using the embodiment.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0018]     In general life when water spills on a flat clean glass, we can see water drops in random and irregular shape. The thickness of water drops is usually about 4-5 mm retained by action of liquid surface tension. In submarine gel casting, the thickness of gel matrix is also about 4-5 mm. This similarity comparison implies that liquid surface tension could be utilized for gel casting in submarine gel electrophoresis.  
         [0019]     However, random water spill method is not acceptable for gel casting because gel matrix with certain dimension is required. After testing, it is found that a simple open frame over the flat glass will satisfy the dimension requirement. The open frame is simply placed on the glass. Gaps between the open frame and glass should allow the spilt water to flow away from the open frame. In fact, spilt water stays within the open frame even though gaps are not sealed. A capillary attraction force is generated onto the spilt water by the open frame. This force traps spilt water from flowing away. It indicates that a gel matrix can be formed in such a simply way without using gel trays and sealing means.  
         [0020]      FIG. 1  shows a perspective view of open frame  10  for gel casting. Open frame  10  has only 4 side arms similar to a picture frame in rectangular shape. The length of short arms  12  and long arms  13  are determined by application desires. Popular gel sizes are, for example, 12 cm×8 cm and 10 cm×6 cm. A plurality of anchor structure  16  is extended from bottom edge of 4 side arms. Gaps  18  are reserved as open spaces between neighbor units of anchoring structure  16 .  
         [0021]     Anchoring structure  16 , an essential element, is illustrated in  FIG. 2  enlarged diagram. Each unit of anchoring structure  16  has a big base  28  and narrow neck  22 . For general applications, each unit is built with a length 6 mm and a height 5 mm. Its width reduces from 3 mm at base  28  to 1.5 mm at neck  22 , which makes base  28  bigger than neck  22 .  
         [0022]     To cast a gel, open frame  10  is first placed on a flat surface  26  with anchoring structure  16  pointing to flat surface  26 . Gel liquid  29  in a certain volume is then poured into open frame  10  to immerse all anchoring structure  16 . After solidification, gel liquid  29  becomes gel matrix  24 . Gel matrix  24  is hooked onto open frame  10  along its perimeter. The joint is secured from accidental detachment because base  28  is bigger than neck  22 . Now gel matrix  24  can be handled in the way similar to a conventional gel in a gel tray, even though there is no bottom plastic sheet to support gel matrix  24 , as shown in  FIG. 3 . To further enhance the strength of joining force, more units of anchoring structure  16  can be installed. Base  28  in different shape can also provide extra hooking power. In general, enough hooking strength can be obtained by installing  1  unit of anchoring structure  16  in every 1 cm distance along side arms of open frame  10 .  
         [0023]     Flat surface  26  provides support to open frame  10  and receive gel liquid  29  during gel casting. After gel casting, flat surface  26  form the bottom face of gel matrix  24 . When starting electrophoresis, open frame  10 , together with hooked gel matrix  24 , is separated from flat surface  26  and placed in submarine gel apparatus  42 . That is, flat surface  26  has no function during electrophoresis, which enables the first improvement of the invention: Rapid gel casting.  
         [0024]     In conventional gel casting, gel tray bottom has to be electric insulated, usually plastics, because it is used for both gel casting and electrophoresis in electric field. A plastic has poor property of thermal transfer. In contrast, flat surface  26  is used only for gel casting. A metal plate can be used to replace plastics. In the embodiment, flat surface  26  is an aluminum plate, a potent heat sink, in a size 30 cm×20 cm×1 cm. Hot agarose gel liquid is poured onto the metal plate in direct contact. Heat transfers instantly from gel liquid  29  to flat surface  26 . The waiting time of gel cooling is dramatically reduced.  
         [0025]     A functional requirement to gel matrix  24  is its electric pathway in electrophoresis via buffer solution. A conventional gel in gel tray can only be used in one orientation because two longitudinal sidewalls of gel tray insulate its electric pathways. Open frame  10  provides electric pathways to every edges of gel matrix  24  via gaps  18  and open spaces between base  28  and bottom of submarine gel apparatus  42 . Because gel matrix  24  has no plastic sheet underneath, its bottom face is open and immersed in buffer  40  when placed to submarine gel apparatus  42 .  
         [0026]     During gel casting, gel liquid  29  flows across gaps  18  to form exposed edge of gel matrix  24 , as shown in  FIG. 3 . Edges of gel matrix  24  will contact buffer  40  directly in submarine gel apparatus  42 , as shown in  FIG. 4 . This structure makes the second improvement feasible: Two-dimensional electrophoresis.  
         [0027]     To cast a long length gel for genome project, a plurality of sample wells  13  is formed in parallel with short arms  12 , as shown in  FIG. 3 . To cast a wide and short gel for PCR project, sample wells  13  can be formed in another orientation, in parallel with long arm  14 . The entire open top of open frame  10  allows free access of well forming combs into gel liquid  29  in both orientations. After gel casting, open frame  10  with gel matrix  24  is placed in submarine gel apparatus  42  in a proper orientation for electrophoresis. To fit inside submarine gel apparatus  42  for both orientations, the length of long arm  14  of open frame  10  should be equal or smaller than the internal size of buffer tank of submarine gel apparatus  42 .  
         [0028]     The capacity of two-dimensional electrophoresis is meaningful for precast gels.  FIG. 5   a  shows a frame member  54  holding a precast gel  50 . Two rows of sample wells,  48  and  52  in perpendicular angle, are formed along two edges of precast gel  50 . Users have the freedom to use precast gel  50  in either a landscape gel format or a portrait gel format, as shown in  FIGS. 5   a  and  5   b  respectively. Arrow  58  indicates sample migration direction in electrophoresis.  
         [0029]     Although the description above contains specifications, it will apparent to who&#39;s skilled in the art that a number of other variations and modifications may be made in this invention without departing from its spirit and scope. Open frame  10 , for example, can be altered in numerous ways using plastic molding method. Flat surface  26  can be replaced by bench top to support open frame  10  for gel casting. Gel liquid  29  can be replaced by acrylamide gel solution. Anchoring structure  16  can be omitted when open frame  10  is used to generate hooking force. Thus, the description as set out above should not be constructed as limiting the scope of the invention but as merely providing illustration of the presently preferred embodiment of the invention.