Simultaneous rapid estimation of sedimentation coefficient and molecular weight

Area of Science:

• Biophysical Chemistry
• Macromolecular Science
• Analytical Ultracentrifugation

Background:

• Sedimentation velocity experiments are crucial for characterizing macromolecules.
• Simultaneous estimation of sedimentation (s) and diffusion (D) coefficients can provide comprehensive molecular information.
• Traditional methods may require extensive data or specific experimental conditions.

Purpose of the Study:

• To develop and validate a method for simultaneous estimation of s and D from the early phase of sedimentation velocity experiments.
• To determine optimal experimental parameters for accurate s and D determination.
• To assess the applicability of the method to various globular macromolecules.

Main Methods:

• Analysis of concentration (C) versus radial position (r) data using nonlinear least squares.
• Application of an approximate solution to the Lamm equation.
• Testing with simulated noisy data and experimental data from ribonuclease, ovalbumin, and somatostatin dodecylsulfate.

Main Results:

• The method successfully estimates both s and D simultaneously from early sedimentation data.
• Optimal estimation occurs within specific ranges of dimensionless parameters: 0.002-0.01 for (= 2D/(s.omega(2).r(a)(2))) and < 0.04 for tau(= 2 somega(2)t).
• Accurate estimation is achievable for globular macromolecules (10^4 to 10^6 daltons) using data from the first 3000-5000 seconds.

Conclusions:

• Early data from sedimentation velocity experiments can be efficiently utilized for simultaneous s and D estimation.
• The described method offers a time-saving approach for macromolecular characterization.
• Appropriate selection of rotor speed is key to optimizing the estimation of both coefficients.