Abstract: The present subject matter provides a capillary viscometer for use in measuring concentration and shear dependence of the viscosity of macromolecular solutions. In one embodiment the device can automatically make serial dilutions of a single initial sample and record viscosity measurements across wide concentration ranges without changing samples. The device and associated methods can be used to rapidly and accurately assay solute stability and potentially solute-solute interactions in solutions of proteins and other macromolecules of pharmaceutical interest over a wide range of concentrations, including those corresponding to pharmaceutical formulations.

Abstract: A method of controlled centrifugation including automatic determination (before or during a centrifugation run) of the time to reach "completion" (within specified limits, depending on the criteria adopted) of a centrifugal separation. By simulation, the sample solute concentration distributions are determined and examined periodically. Centrifugation completion is deemed to have been reached based on certain predetermined criteria relating to spatial changes in the sample solute concentration distributions between successive examinations. The positions of the end points of the concentration distributions or band edges of the sample solutes (transitions from regions of sample solutes to regions of no sample solutes) are determined to facilitate resolving spatial changes of the concentration distributions.

Abstract: A process and apparatus for predicting the time and position dependent concentration of macromolecules of differing species in a gradient forming solution during centrifugation is disclosed. A mathematical model of the time dependent behavior of gradient forming solutes in a centrifugal field, based upon the underlying physical principles governing sedimentation and diffusion is formulated. The simplifying approximation is made that the wall effects may be ignored, and that the transport of solute may be treated as a one dimensional process with forces dependent only upon the radial distance. A sedimentation diffusion (Lamm) equation in one dimension is numerically integrated. The sedimentation diffusion equation (Lamm equation) for each macrosolute is solved concurrently with that for the gradient forming solute, utilizing the experimentally based density dependent sedimentation coefficient. The equations are solved for incremental time periods for the centrifuged samples in successive radial segments.

Abstract: 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.

Abstract: 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.