Note: Descriptions are shown in the official language in which they were submitted.
CA 02837319 2013-12-19
Compartmentalized gel-electrophoresis apparatus
Field of the invention:
The present invention relates to electrophoresis and more particularly to a
design that improves
the versatility and convenience of using electrophoretic devices.
Background:
Electrophoresis is a commonly employed technique that applies an electric
field to separate
desired molecules based on some of their properties, which includes (but is
not necessarily limited
to) their size, charge or binding affinity. In particular, electrophoresis of
multiple samples is
normally performed on a porous gel medium. The gel medium is normally immersed
in a liquid
(and in particular, buffers for biological applications). During
electrophoresis, a current is run
through the apparatus and forces molecules to migrate from one side of the gel
to another. Each
type of molecule will migrate at a different rate based on their chemical
properties. Gels are
usually run with a reference ladder to identify the size of the loaded
molecules after the
electrophoretic process.
Normally, multiple gels are run with the same conditions within the same
container. One cannot
stop the gel when it has already started running if one wants to add more
samples to the same gel.
Doing so would make the comparison of the newly loaded samples to the
reference ladder
inaccurate.
Another common phenomenon is that some experiments (e.g. protein
purifications) take multiple
days to complete and something could go wrong early on in the experiment
before you can check.
If left unchecked until near the end of the experiment, this could end up
wasting time, money and
reagents.
1
CA 02837319 2013-12-19
Rather than waiting until the end of the experiment to perform
electrophoresis, one can perform
electrophoresis more in "real time". In other words, one can simply start the
electrophoretic
process after obtaining a few samples, rather than waiting until near the end
of the experiment
where one has a lot more samples. In addition, one can also run multiple gels
independently and
can start or stop the electrophoretic process at any time without interrupting
the other gel runs
within the main electrophoretic unit. Furthermore, one can run multiple gels
with different
compositions or different running buffers, thereby eliminating the need to use
extra space or
additional electrophoresis units.
Prior art:
The current improvements on gel electrophoresis apparatuses are intended to
accommodate a
different scope of experiments. Examples of such improvements are:
1) EP 0644420 A2, Method and apparatus for gel electrophoresis
Inventors: Chand ran R. Sabanayagam, George M. Holzwarth, Eric H. Lai
The invention employs two or more electric fields in a single gel. According
to this invention, which
is defined as Multiple-Zone Pulsed-Field Gel Electrophoresis (MZPFGE), the
electric field is set to
different values in two or more spatially distinct regions of the gel.
2) EP 1230258 Al, Multi-compartment electrophoresis
Inventors: Ben Herbert, Pier Giorgio Righetti
A multi-compartment electrolyser design is used to prefractionate complex
protein mixtures, for
use prior to the implementation of 2-D maps; it helps to remove proteins
present in large excess in
a cell lysate or in body fluids.
3) WO 1992016830 Al, Segmented electrophoretic separation system useful for
lipid profiling
Inventors: Technology Inc Assay, Joyce Chang, Charles R Manning, Leroy 1 Pinto
2
CA 02837319 2013-12-19
The device comprises of a plurality of gel matrixes, defining a liquid pathway
upon which a
directional electrophoretic gradient can be imposed. The gel matrices are in
serial relationship and
preferably are of a successively decreasing pore size.
4) WO 2005098408 Al, Multi function gel electrophoresis and apparatus
Inventors: Charles B Scott, John Victor Mcknight, Steven., Elliott
The invention enables the user to perform electrophoretic separation and
electroblotting in the
same system. Also provided are means to efficiently exchange heat within the
system.
5) US 20040195103 Al, Vertical slab gel electrophoresis cell and method
therefor
Inventor: Deming Zhou
An improved vertical slab gel electrophoresis cell and method for performing
electrophoresis
vertically within uprightly oriented slab shaped gel matrixes.
While these references may be adequate for their intended purpose, there is
still a need for an
apparatus that allows compartmentalization of gel cassettes with different gel
conditions and
different buffers during electrophoresis. There is also a need to
simultaneously and independently
run different gel cassettes, and to allow the addition and removal of gel
cassettes without
disturbing the electrophoresis process of other gel cassettes. All the
features detailed in the prior
arts are compatible with the proposed invention, including the advantage of
the plurality of slots
(which is exclusive to our apparatus). Therefore, there is still a need for
improving the
electrophoretic apparatus design to make the electrophoretic device more
versatile.
3
CA 02837319 2013-12-19
Summary:
The factors noted in the background suggest that the current design of
electrophoretic apparatus
is robust. However, the design lacks versatility to accommodate the problems
mentioned in the
background. The present invention allows separate subunits (also referred to
as "cassettes" in the
invention description), in the main electrophoretic apparatus to be run
simultaneously and
independently. The addition or removal of one or more subunits at any time
will not disturb the
progress of other subunits that are within the main apparatus. It is also not
mandatory to
completely occupy every subunit slot ("cassette socket") in the main
apparatus, as the
electrophoretic process will still run properly. These features of the present
invention also allow
multiple users to share the main electrophoretic apparatus without consuming
additional space
(e.g. extra power supply units and extra electrophoretic chambers) because
each subunit is
independently run.
Gels with different compositions could be run in each subunit with different
liquid buffer solutions
(depending on the person operating the gel and what type of experiment is
performed). Since each
subunit can contain a small volume of liquid buffer solution, less buffer will
be used per run (as
opposed to electrophoretic runs in the current commercial electrophoretic
chambers). However,
smaller volumes of buffer will usually be unable to mitigate excessive heating
of the gel during
electrophoresis, so a heat exchanger is usually necessary for cooling the
subunits during
electrophoresis. This heat exchanger will allow the flow of a desired fluid
(e.g. water) through the
back of the main electrophoretic apparatus.
Additional features and advantages of the present invention will become more
apparent from the
detailed description that follows, taken in conjunction with the accompanying
drawings.
4
CA 02837319 2013-12-19
Brief Description of Drawings
Figure 1 is a front view of the present invention's main apparatus.
Figure 2 is a side view of the present invention's main apparatus.
Figure 3 is a front view of the subunit that accompanies the main apparatus.
Figure 4 is a side view of the subunit that accompanies the main apparatus.
Figure 5 is a top view of the subunit that accompanies the main apparatus.
Description
While the features and principles that characterize this invention and
distinguish it over the prior
art may be implemented in a variety of ways and embodied in a variety of
constructions, the
invention as a whole can best be understood by examination of a specific
example. One such
example is depicted in the drawings.
Figure 1 depicts the front view of the main electrophoretic apparatus 1 of the
invention. This
apparatus can accommodate a plurality of slots, cassette sockets 3, that can
accommodate gel
cassettes 14. These gel cassettes are further depicted in Figure 3, Figure 4
and Figure 5. The main
electrophoretic apparatus 1 comprises of a lid 2, an anode 6 and a cathode 7,
both of which are
attached to the lid 2 and connected to a power supply 8. The cathode carries
the negative charge
and the anode carries the positive charge. While the power supply is active,
electrons enter
through the cathode 7, travel through the cathode conductive wire 4 and into
any inserted gel
cassettes via the current conduction strips 5. The electrons will then exit
into the anode conductive
wire 11 and exit through the anode 6. Because an active power supply will
produce heat
throughout the system, a coolant will flow into the coolant inlet 9 and out of
the coolant outlet 10
during electrophoresis.
CA 02837319 2013-12-19
The heat exchanger design is illustrated further in a side view of the main
electrophoretic
apparatus in Figure 2. There are a series of tubes that carries the coolant
into the apparatus: the
coolant inlet 9 and tubes 12 that carry coolant into the plane of the page,
and the coolant outlet 10
and tubes 13 that carry coolant in the opposite direction of the inlet tubes
(i.e. out of the plane of
the page). In other words, pipes that carry coolant into the page are marked
by a bold "X" in Figure
2, while pipes that carry coolant out of the plane of the page are marked by a
bold dot in Figure 2.
Figure 2 also illustrates that the cassette socket 3 does not extend all the
way from the front to the
back of the main electrophoretic apparatus 1. Instead, the cassette socket
only occupies part of the
effective side dimension of the main apparatus. The rest of the side dimension
is occupied by the
heat exchanger.
Figure 3 depicts the front view of the gel cassette 14 of the invention that
is intended to fit into the
cassette sockets 3 (mentioned in Figure 1). A gel 15 with three gel wells 16
is placed into the gel
cassette. The gel is held together by a back glass gel plate 19 and a front
glass gel plate 20 as
shown in Figure 4. The gel plates are securely held in place with a holder 22.
The gels in each
cassette could be of different composition.
The gel cassette has a conductive strip 18 attached to the bottom of the
cassette and attached to
the gel cassette lid 17. The conductive strip 18 connects to the current
conductive strips 5 when
the gel cassette is inserted into the cassette sockets of the main
electrophoretic apparatus. The
conductive strip 18 actually extends a bit deeper into the gel cassette as
shown in Figure 4. This
ensures that the electric current will flow through the entire gel cassette
and gel, so long as there
is enough buffer to make contact with both the top and bottom conductive
strips. The inside of the
gel cassette is then filled with liquid buffer solution 21. The liquid buffer
solutions can differ in
composition among each gel cassette. Figure 5 further is a top view of the gel
cassette and further
helps in conceptualizing the gel cassette design.
6
CA 02837319 2013-12-19
The invention can be used for multiple applications. One mode of carrying out
the invention would
be with SDS-PAGE verification of a protein purification process. Aliquots at
each stage of the
protein purification process will be taken and ran via SDS-PAGE to confirm
that the protein
purification was successful. Protein purification processes often require more
than one day to
complete. There is always a possibility of human error occurring during the
protein purification
process. If there is an error early in the process and this error is not
caught early on, one can waste
reagents and time.
Protein purification processes often use affinity chromatography in
conjunction with a fusion
protein. The fusion protein typically contains the protein of interest
attached to a protein tag
("fusion tag") that has high affinity for a certain type of chromatography
column. Usually one
would elute the protein after binding the protein to the column with an
elution buffer. This elution
buffer would contain a compound that has a higher affinity for the
chromatography column than
the protein. One example of an error that could occur is if the lab personnel
used an incorrect
elution buffer to elute the protein. Typically, one would cleave the fusion
tag off after elution and
this process takes place for 12 or more hours to ensure complete cleavage. The
protein usually
undergoes further purification, e.g. via fast protein liquid chromatography
(FPLC) and FPLC runs
consume a lot of buffer solution and time. If this error were caught on the
first day instead of the
second day, then the amount of wasted time and reagents would be substantially
less.
7
