Chemistry: electrical and wave energy – Processes and products – Electrophoresis or electro-osmosis processes and electrolyte...
Reexamination Certificate
2000-05-25
2003-04-15
Nguyen, Nam (Department: 1753)
Chemistry: electrical and wave energy
Processes and products
Electrophoresis or electro-osmosis processes and electrolyte...
C204S604000
Reexamination Certificate
active
06547943
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a capillary electrophoresis system and method. Specifically, the invention relates to a capillary electrophoresis system and method that provides multiple simultaneous analysis of a sample by positioning first ends of a plurality of capillaries in a single container such that the plurality of capillaries provide simultaneous electrophoretic analysis for a sample in the container.
BACKGROUND OF THE INVENTION
Electrophoresis is a well-known technique for separating small amount of macromolecules. Increasingly, electrophoresis has become an indispensable tool for the biotechnology and other industries and is used extensively in a variety of applications, including the separation, identification and preparation of samples of nucleic acids, proteins and carbohydrates. Of increasing interest in the broader field of electrophoresis is capillary electrophoresis (CE), where particular entities of species are moved through a medium in an electrophoretic channel of capillary dimensions under the influence of an applied electric field. In some applications, the medium in the capillary electrophoretic channel is a buffer. Oftentimes, however, the medium is a gel which acts as a sieving matrix to help retard and separate the individual molecules as they migrate through the capillary channel.
Capillary electrophoresis is typically performed using fused silica capillary tubes. The tubes may have inner channel diameters in the range of about 20-1000 micro-meters or microns (&mgr;m). Capillary electrophoresis is generally employed to analyze an extremely small quantity of samples, such as proteins or nucleic acids. Other benefits of CE include rapid run time and high separation efficiency. A capillary electrophoresis system or apparatus usually charges a glass capillary having an inner diameter of not more than 100 &mgr;m with a migration medium such as buffer or gel, introduces a sample into an end of the capillary, and applies a high voltage across the capillary to separate molecules based on differences in charge-to-size ratio. Since capillaries have large surface area relative to their small volume, resulting in high cooling efficiency, high voltages can be applied in analyzing small quantities of samples at high speed and in high resolution.
To illustrate a capillary electrophoresis process, one may take the example of DNA sequencing using gel capillary electrophoresis. Prior to the electrophoresis analysis, the DNA sample is prepared, using well-known methods, so that a solution of DNA fragments of all possible lengths corresponding to the same total sequential order is obtained, with each fragment terminated with a tag label corresponding to the identity of the given terminal base.
The separation process employs a capillary tube filled with conductive gel. To introduce the sample, one end of the capillary channel is placed into the DNA reaction vial. After a small amount of sample enters the capillary end, both capillary ends are then placed in separate buffer solutions. A voltage potential is then applied across the capillary tube. The voltage drop causes the DNA sample to migrate from one end of the capillary to the other. Differences in the migration rates of the DNA fragments cause the sample to separate into bands of similar-length fragments. As the bands traverse the capillary channel, the bands are typically read at some point along the channel using one of several detection techniques.
Usually, multiple DNA preparation reactions are performed in a commercially available micro-titre tray having many separate low-volume wells, each holding on the order of 200-1000 micro-liters (&mgr;L). The micro-titre trays come in standard sizes. In the biotech industry, the currently preferred micro-titre tray has a rectangular array comprising 8 rows of 12 columns of wells. The centers of adjacent wells found in a single row are separated by approximately 0.9 cm, although this figure may vary by one or two tenths of a millimeter. The same holds for the spacing between adjacent wells in a single column. The rectangular array of
96
wells has a footprint within an area less than 7.5 cm×11 cm.
Miniaturization has allowed more wells to be accommodated in a single micro-titre tray having the same footprint. New trays having four times the density of wells within the same footprint have already been introduced and are fast becoming the industry standard. Thus, these new trays have 16 rows and 24 columns with an adjacent well spacing of approximately 0.45 cm.
Various attempts have been made to perform multiple capillary electrophoresis simultaneously. For example, U.S. Pat. No. 6,027,627 to Li et al., the contents of which are incorporated by reference, discloses an automatic electrophoretic system which employs a capillary cartridge having a plurality of capillary tubes. The cartridge has a first array of capillary ends projecting from one side of a plate. The first array of capillary ends are spaced apart in substantially the same manner as the wells of a micro-titer tray of standard size. This allows one to simultaneously perform capillary electrophoresis on samples present in each of the wells of the tray.
U.S. Pat. No. 6,048,444 to Takahashi et al., the contents of which are incorporated by reference, discloses a capillary electrophoresis apparatus having a plurality of capillaries which are filled with migration medium and have first ends into which samples are injected and second ends from which components included in the samples are eluted. The apparatus further comprises a sheath flow cell in which the second ends are arranged in a straight line at first predetermined intervals and are terminated; means for flowing a buffer solution in the sheath flow cell from the lower part of the sheath flow cell to the upper part of the sheath flow cell; and means for detecting a component eluted from each of the capillaries in the sheath cell near the second ends.
U.S. Pat. No. 6,054,032 to Haddad et al., the contents of which are incorporated by reference, discloses a capillary electrophoresis array that includes a plurality of capillary tubes arranged adjacent each other in a generally longitudinal orientation with each of the tubes having an inlet end, an outlet end, and internal diameter no greater than about 100 microns; and a registration assembly in which adjacent tubes are held in place with a fixed lateral spacing relative to each other at both the inlet and the outlet ends of the tubes. The array is flexible along the length of the tubes.
Despite these progresses, the efficiency and reliability of capillary electrophoresis is still in need of improvement in various aspects. One particular problem is that, in many cases, and often for unknown reason, a run of capillary electrophoresis for a sample would simply fail, resulting in the waste of time and materials. Although this problem could be alleviated somewhat by running multiple analysis for the sample, in many situations, there is simply not enough sample, or the samples are too expensive, to do so using available prior art methods. Furthermore, in other situations, more electrophoresis data for a sample is desirable to achieve reliable results.
SUMMARY OF THE INVENTION
The invention provides a capillary electrophoresis system for providing simultaneous multiple analysis of a sample. The system comprises: at least one assembly of capillaries comprising a plurality of capillaries having first and second capillary ends and being held in a spaced relationship relative to one another at a point proximate to the first capillary ends, a cross-section of the first capillary ends defining a minimum bounding polygon having a footprint with a major dimension; and a container comprising at least one compartment having an opening and a bottom, and configured to hold a single body of liquid; wherein the assembly is positioned such that its first ends extend through the opening and into the at least one compartment to thereby simultaneously contact a single body of liquid, when said liquid is
Kane Thomas E.
Qingbo Li
Nguyen Nam
Pennie & Edmonds LLP
Spectrumedix LLC
Starsiak Jr. John S.
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