Electrophoretic mobility equation for protein with molecular shape and charge multipole effects

Area of Science:

• Biophysics
• Physical Chemistry
• Protein Science

Background:

• Electrophoretic mobility is crucial for protein analysis.
• Existing models often simplify protein shape and charge distribution.
• Accurate prediction requires considering complex molecular properties.

Purpose of the Study:

• To develop a simple yet comprehensive formula for free solution electrophoretic mobility of proteins.
• To incorporate molecular shape and charge distribution effects into mobility calculations.
• To validate the model using protein atomic coordinate data.

Main Methods:

• Utilized a deformed sphere model for protein molecular shape.
• Represented charge distribution using net charge, charge dipole, and charge quadrupole.
• Derived a new electrophoretic mobility equation based on these parameters.
• Calculated hydrodynamic radius from atomic coordinate data.

Main Results:

• The derived formula includes molecular shape and charge distribution effects.
• Charge dipole was found to have no impact on protein mobility.
• Charge quadrupole, combined with surface equation coefficients, influences mobility.
• The model accurately predicts protein hydrodynamic radius from atomic data.
• The simplified equation reduces to the Henry equation when charge quadrupole is negligible.

Conclusions:

• The new formula provides a more accurate prediction of protein electrophoretic mobility.
• The deformed sphere model effectively captures protein hydrodynamic radius.
• This approach enhances the understanding of protein electrophoresis and behavior in solution.