Imperforate bowl: centrifugal separators – Including plurality of miniature bowls distrubuted about... – Having bowls – or holders therefor – pivotaby attached to...
Reexamination Certificate
2000-01-28
2001-02-27
Cooley, Charles E. (Department: 1723)
Imperforate bowl: centrifugal separators
Including plurality of miniature bowls distrubuted about...
Having bowls, or holders therefor, pivotaby attached to...
C494S037000
Reexamination Certificate
active
06193642
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to improvements in high throughput assays of chemical compounds, cells, proteins and the like. More particularly, the present invention provides an improved centrifugation bucket for use in a plate to plate transfer apparatus for transferring small volumes of materials from small well plates having a large plurality of wells, such as presently existing 1536-well plates, or for performing separations, filtrations or the like in a similar context.
BACKGROUND OF THE INVENTION
To find lead compounds for drug discovery programs, large numbers of compounds are often screened for their activity as enzyme inhibitors or receptor agonists/antagonists. Large libraries of compounds are needed for such screening. As a result of developments in this field, it is now possible to simultaneously produce combinatorial libraries containing hundreds of thousands of small molecules for screening. With the availability of such libraries, however, has come a need for large scale, rapid screening methods. In the context of these methods, it has proven advantageous to perform a plate to plate transfer employing the 1536-well plate described in PCT Application Ser. No. PCT/US98/00494 entitled Multi-Well Plate, filed Jan. 8, 1998 and incorporated by reference herein, or employing other plates containing a large number of samples in a large number of low volume wells. Such plates are secured in a facing alignment in a centrifugation bucket and centrifuged to effect transfer.
When two plates are secured in a centrifugation bucket, an interstice exists at the contact surface between the plates, providing a possible path for liquid flow between the plates and along the surfaces of the plates. Capillary action contributes to this flow. Also contributing to this flow are force components produced during centrifugation which act parallel to the interstice between the plates. Liquid flow along the surfaces of the plates is highly undesirable because it allows contamination of the contents of one well by liquid lowing from another well, and because it allows loss of material as liquid flows out of the lates through the interstice between the plates.
In a typical centrifugation bucket of the prior art, the centrifugation bucket is mounted on a centrifuge rotor by a hinge, allowing the bucket to pivot about a single axis in response to the forces of centrifugation. This allows the plates to be held parallel to the axis of rotation of the centrifuge once operational speed has been achieved. The only force produced by centrifugation during this time is a force acting normal to the surfaces of the plates. However, during starting and stopping of the centrifuge, tangential force components exist which act parallel to the surfaces of the plates and thus parallel to the interstice between the plates. These forces exist while the centrifuge accelerates from rest to its operating speed, and while the centrifuge decelerates from its operating speed to a resting position, and are produced by changes in rotational speed. The tangential forces tend to produce flow of liquid in the interstice between the plates and parallel to the surfaces of the plates. This presents a risk of contamination and loss of material.
As noted above, a typical centrifugation bucket according to the prior art comprises a yoke which is free to pivot around a single hinge. When the centrifugation bucket is at rest, the yoke is in a resting horizontal position. When the centrifugation bucket is placed in a centrifuge and is accelerated to operating speed, the yoke swings upward under the influence of the centrifugal forces produced by the rotation of the centrifuge, and is held parallel to the axis of rotation by these centrifugal forces. The force produced by centrifugation under these circumstances is the normal force, which acts perpendicular to the plates. However, as the centrifuge is accelerated or decelerated, tangential forces acting parallel to the surfaces of the plates also materialize, and contribute to liquid flow between the plates. Because the centrifugation bucket pivots about a single hinge, it lacks sufficient freedom of movement to respond to both the normal force and the tangential force exerted during the centrifuging process.
There exists, therefore, a need in the art for an improved centrifugation bucket for use in centrifuging multi-well plates, which allows the plates to pivot so as to allow maximization of forces acting perpendicular to the plates and minimization of forces acting parallel to the plates.
Summary of the Invention
A centrifugation bucket according to one aspect of the present invention includes a yoke suitable for attachment to a centrifuge rotor by a first hinge providing a primary axis of rotation. A platform for holding microwell plates is attached to the yoke by a second hinge or connector providing a secondary axis of rotation. The yoke pivots about the primary axis of rotation in response to the normal forces exerted on the centrifugation bucket as the rotor accelerates and decelerates. At the same time, tangential forces act to pivot the platform about the secondary axis of rotation such that force components acting normal to the platform are maximized and other force components are minimized.
A more complete understanding of the present invention, as well as further features and advantages of the invention, will be apparent from the following Detailed Description and the accompanying drawings.
REFERENCES:
patent: 2604261 (1952-07-01), Silverstolpe
patent: 3028075 (1962-04-01), Blum
patent: 3674198 (1972-07-01), Eberle
patent: 5816998 (1998-10-01), Silverstolpe et al.
Cooley Charles E.
Law Offices of Peter H. Priest, PLLC
Pharmacopeia Inc.
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