Externally adjusted Rayleigh aperture for the Spinco model E ultracentrifuge

Abstract

The use of the Rayleigh interference optical system in analytical ultracentrifugation has found an ever-increasing popularity since it was first demonstrated by Richards and Schachman (1) that it can provide an extremely precise record of refractive index differences as a function of radius within the centrifuge cell. As theoretical and experimental developments in this field have imposed increased demands for accurate optical alignment, provisions have been made available as standard equipment on the Spinco model E ultracentrifuge for precise and flexible adjustability of the Rayleigh optical components to allow fulfillment of alignment criteria by incremental photographic determination of optimal settings (2). The currently available Rayleigh aperture assembly has provisions for transverse and rotational adjustment. However, it is not accessible during centrifugation required to provide gradients in the cell used in many procedures of rotational alignment, so that incremental adjustment for photographic examination of fringe patterns as a function of angle becomes a time-consuming operation. In this communication, we describe a procedure for minimal modification of existing Spinco components which removes this restriction and ensures rapid and reproducible rotational alignment of the Rayleigh aperture.