Improvements in the Air-Driven Ultracentrifuge for Molecular Sedimentation

A description is given of the following improvements in an air-driven ultracentrifuge intended for molecular sedimentation: (1) A driving mechanism equipped (A) with reversing air jets that provide for smooth and rapid stopping and (B) with spring compression screws for adjustment to eliminate vibrations. (2) A head which makes it possible to centrifuge considerable volumes of solution in a field sufficiently great to concentrate and crystallize large protein molecules. (3) The use of a high pressure mercury arc in place of the usual direct-current lamp as light source for both absorption and refractive index measurements. (4) A device for automatically taking the series of photographs needed for determinations of rate of sedimentation.