The United States of America As Represented by the Secretary of

The United States of America As Represented by the Department of Health

Arun K Attri

James V Sullivan

Allen P Minton

Paul Fitze

An apparatus for sequentially fractionating a centrifuge tube includes a capillary tube and a means for applying positive pressure. The capillary tube has an O-ring at the lower end thereof. As the capillary tube is placed within the centrifuge tube, the O-ring forms a seal within the tube. Movement of the capillary tube within the centrifuge tube places the liquid in the centrifuge tube under pressure, thus forcing the liquid to flow up through the capillary tube and into a chamber. A chase fluid is then pumped horizontally through the chamber to force the liquid therein through an exit port and into a fraction collector. The apparatus and method of the present invention may be entirely automated and controlled by a single microprocessor.

Method and apparatus for sequential fractionation

An automated system for measuring the concentration gradient of centrifuged solute and directly calculating the molecular weight and/or sedimentation coefficient of an optically absorbing solute. Monochromatic light passes through a stationary slit and a previously centrifuged sample in a tube while the tube is moved vertically at a uniform rate by a platform which is driven by a motor and gearing, including a gear nut which drives a vertical screw attached to the platform. The transmitted light impinges on a photodetector which provides absorbance readings. This provides data of absorbance vs. time through the scanning cycle, which is processed digitally. A microcomputer is used to calculate the molecular weight and/or sedimentation coefficient from this data. The centrifuge tube is supported in a transparent cuvette containing a black plastic adaptor block which conformably receives the tube and supports it in upright position, allowing the light beam to pass through opposite vertical slot portions in the block. The cuvette rests on the platform, which is moved vertically relative to the slit defining the fixed beam path. A microswitch is operated at the upper limit of travel to stop the drive motor. The motor is external to the housing in which the optical components and the sample tube are located. The external motor is coupled by a flexible shaft to the drive gearing. Alternatively, a stepping motor may be employed instead of a synchronous motor to move the centrifuge tube in an incremental fashion rather than at uniform velocity.

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Bethesda, MD, United States of America

Arun K Attri