Design concepts in absorbance optical systems for analytical ultracentrifugation

Abstract

Analytical ultracentrifugation is a powerful technique for analyzing particles in solution, and has proved valuable for a wide range of applications in chemistry, biochemistry and material sciences for many years. The field is presently seeing a resurgence of instrument development from commercial and academic groups. To date, no modern optical modeling techniques have ever been applied to the basic imaging properties of the optical system in analytical ultracentrifugation. In this manuscript we provide a contextual framework for the application of such techniques, including an overview of the essential optical principles. The existing commercial and open source detection systems are evaluated for imaging performance, highlighting the limitations of chromatic aberration for broadband acquisitions. These results are the inspiration for a new mirror-based design, free of chromatic aberration. Our findings present a path forward for continued development in imaging and detector technology, where improved data quality will now push the limits of detection and resolution of analytical ultracentrifugation for years to come.

Binary Colloidal Nanoparticles with a Large Size Ratio in Analytical Ultracentrifugation

“…In a typical sedimentation–diffusion equilibrium (AUC‐SE) experiment, a 3 μl sample and reference were separately injected into the two channels of an AUC cell of 1.5 mm path length. The AUC cell was then placed into a custom‐made Multi‐Wavelength Analytical Ultracentrifuge (MWL‐AUC). The measurement settings: Temperature 25 °C; wavelength range 350–700 nm.…”

Practical Aspects of Multiwavelength Analytical Ultracentrifugation

“…Setting the iris opening to slightly before an intensity drop is observed has been found to yield good results in practice. Further detail on the effects of numerical aperture and optical imaging systems are discussed in Pearson et al [9].…”

“…Early design iterations of the open-source MWL-AUC hardware featured lens-based illumination and imaging optics. The integration of mirror-based illumination and imaging optics, free of chromatic aberration, has been described recently and is the subject of the alignment and focusing protocol in the following discussion [2,9]. In addition to the open-source MWL-AUC mirror optics hardware detailed here, a commercial spin-off version of the detector has been introduced by Nanolytics © of Potsdam [10].…”

ICCD camera technology with constant illumination source and possibilities for application in multiwavelength analytical ultracentrifugation

“…Spot-focused illumination is equivalent to the confocal type optics described previously for Open AUC MWL detectors. 4,9 A schematic of the test setup is illustrated in the ESI Fig. 2.…”

“…4 Compact imaging optics were designed based off the concept of mirror imaging optics published previously. 4,9 The design details and basic imaging tests are provided in ESI Fig. 3 and 4.…”