Yingtai:How To Determine The Molecular Weight of A Molecule During Ultracentrifugation?

Yingtai: How To Determine The Molecular Weight of A Molecule During Ultracentrifugation?

In the process of ultracentrifugation, determining the molecular weight of a molecule is primarily achieved using the sedimentation equilibrium equation. This equation is based on the principle that the sedimentation velocity and the diffusion velocity of a molecule reach equilibrium under the influence of centrifugal force.

Here are the general steps for determining molecular weight:

1. Establish the Sedimentation Equilibrium Equation:

  Under centrifugal force, molecules move towards the outer side of the centrifuge rotor. Simultaneously, molecules also diffuse towards the inner side. When these two processes reach equilibrium, the net movement of the molecules is zero.

2. Measure Concentration Distribution:

  During ultracentrifugation, the concentration distribution of the molecules is monitored in real-time using optical systems (such as absorbance, interference, or fluorescence detectors). These systems measure how the concentration of the molecules changes over time and with centrifugal force.

3. Data Processing:

  The measured concentration distribution data is substituted into the sedimentation equilibrium equation. Molecular weight is determined by solving this equation through numerical integration or fitting methods.

  Typically, software tools are used to analyze experimental data and extract information about molecular weight.

4. Calibration and Verification:

  During data analysis, calibration factors such as the density and viscosity of the solvent, the shape of the molecule, and solvent effects need to be considered.

  The accuracy of the experimental results can be verified by comparing them with known molecular weight standards.

By following these steps, molecular weight can be accurately determined using ultracentrifugation technology. This method is especially useful for determining the molecular weight of large molecules (such as proteins, nucleic acids, etc.) as it provides high resolution and precision.