Analytical Ultracentrifugation - Solution Interaction Analysis Systems (sIA)
Because of its ability to quantitate the size and shape of macromolecules in solution, one of the most powerful methods for characterization of macromolecular interactions is Solution Interaction Analysis (sIA) in the Optima™ XL-A and XL-I analytical ultracentrifuges.
Characterize Reversible Associations
Thermodynamic properties are most often obtained from Equilibrium Sedimentation Methods, in which data obtained from a steady-state solute gradient is fit to mathematical models describing various states of Reversible Associations. It is advantageous to analyze data from equilibrium distributions created at different speeds. Using the Windows*-based user interface, methods can be created and stored to automate changes in temperature, rotor speed, and frequency of data collection. Using the 6-channel centerpiece in the An-50 Ti Rotor, up to 21 samples can be quickly characterized; up to 28 samples can be characterized using the 8-channel centerpiece in the Optima™ XL-I.
Rapid Determination of Stoichiometry
Hydrodynamic properties, (such as s, D, mass, and shape) are typically characterized by Sedimentation Velocity Methods in which a moving sample boundary is measured as a function of time. The rapid data capture rate of the Rayleigh Interference Optical System on the Optima™ XL-I is ideal for measuring the rapidly moving boundary of large molecular complexes. The g(s*) Data Analysis Method, one of many supplied with the instrument, also provides accurate Mw,app and Stoichiometry Calculations from velocity data.
"Based on our experiences, we can provide a very compelling case that the XL-A has had an impact on our research activity that is rarely achieved through acquisition of an instrumental or technical capability." --Jeffrey Hansen, Ph.D. Department of Biochemistry, University of Texas, Health Science Center, San Antonio
Easy Sample Preparation
As little as 15 µL of sample is required for Solution Interaction Analysis (sIA). Simply inject the sample and reference solutions into opposing positions in the cell assembly and place the assembly into the instrument. Run up to 28 different sample/reference pairs in a single run with the An-50 Ti Rotor. Each sample may have a different set of solute/solvent conditions (pH, ionic strength, concentration) to provide a maximum amount of data in as little as 2 hours. Afterwards, the sample is easily recovered for use in complementary characterization techniques.
The 8-position An-50 Ti Rotor can accommodate up to 28 samples using 8-channel centerpieces on the Optima™ XL-I, 21 samples using the 6-channel centerpieces on the XL-A, and up to 7 samples using standard Double-Sector centerpieces.
Flexible Instrument Setup
Run parameters and data acquisition modes are easily and quickly entered and stored in the Windows*-based operating system. Develop and store custom methods that automatically change analysis conditions and data acquisition modes.
Multiple Detection Systems
Choose the Optima™ XL-A with Scanning UV/Vis or the Optima XL-I with both Scanning UV/Vis and Rayleigh Interference Optics. The Scanning UV/Vis detection system provides sensitivity for low-concentration work, and selectivity for optimizing detection based on the analyte's maximum absorbance. The Optima XL-A can be upgraded to add Rayleigh Interference capability. Rayleigh Interference detection measures the change in refractive index resulting from changes in analyte concentration. This provides increased accuracy and the ability to examine a greater concentration range with a wider selection of samples. The Optima XL-I is equipped with both detection systems and can collect data from both simultaneously to provide the broadest spectrum of data for sIA.