Effect of divalent cations on DMPC/DHPC bicelle formation and alignment

Area of Science:

• Biophysics
• Structural Biology
• Biochemistry

Background:

• Divalent cations are crucial for biomolecule activity and structural studies.
• Bicelle mixtures are valuable for NMR-based structure determination but sensitive to solution components.
• Cholesterol sulfate-stabilized DMPC/DHPC bicelles are common membrane mimetics.

Purpose of the Study:

• To investigate the impact of varying concentrations of Ca(2+), Mg(2+), Zn(2+), and Cd(2+) on DMPC/DHPC bicelles.
• To understand how divalent cations affect the phase behavior and magnetic alignment of bicelle media.

Main Methods:

• Preparation of bicelle mixtures containing DMPC, DHPC, and cholesterol sulfate.
• Systematic addition of increasing concentrations of four divalent cations (Ca2+, Mg2+, Zn2+, Cd2+).
• Analysis of the magnetically aligned phase behavior using solution-state NMR.

Main Results:

• Low concentrations of all tested divalent cations were tolerated with minimal disruption.
• Higher concentrations of Zn(2+) and Cd(2+) disrupted the magnetically aligned bicelle phase.
• Higher concentrations of Ca(2+) and Mg(2+) resulted in more strongly oriented bicelle phases.

Conclusions:

• Divalent cations influence the stability and orientation of bicelle media.
• Specific divalent cations can be used to modulate bicelle phase behavior for NMR studies.
• This offers a method to control orienting media for protein and nucleic acid structure determination.