Improved low pH bicelle system for orienting macromolecules over a wide temperature range

Area of Science:

• Biophysical chemistry
• Structural biology
• Macromolecular science

Background:

• Bicelle systems are crucial for protein structure determination using NMR spectroscopy.
• Existing bicelle formulations often lack stability in acidic environments, limiting their application.
• Acidic conditions are necessary for studying certain proteins and their interactions.

Purpose of the Study:

• To develop a novel bicelle system with enhanced chemical stability at low pH.
• To demonstrate the utility of this new system for inducing protein alignment under acidic conditions.
• To facilitate the measurement of residual dipolar couplings (RDCs) for acid-loving macromolecules.

Main Methods:

• Preparation and characterization of a novel bicelle system composed of 1,2-di-O-dodecyl-sn-glycero-3-phosphocholine (DIODPC) and 3-(chloramidopropyl)dimethylammonio-2-hydroxyl-1-propane sulfonate (CHAPSO).
• Determination of the optimal DIODPC/CHAPSO molar ratio (4.3:1) for magnetic orientation.
• Assessment of chemical stability across a pH range from 6.5 down to 1.0.
• Induction of protein alignment and measurement of residual dipolar couplings (RDCs) for rusticyanin at pH 2.1.

Main Results:

• The novel DIODPC/CHAPSO bicelle system achieves magnetic orientation at pH values as low as 1.0.
• The bicelles exhibit significant chemical stability in highly acidic media.
• Large residual dipolar couplings were measured for rusticyanin, confirming effective protein alignment.
• The system proved particularly useful for macromolecules requiring very acidic conditions.

Conclusions:

• The DIODPC/CHAPSO bicelle system offers a robust solution for protein alignment in acidic environments.
• This advancement expands the applicability of RDC measurements to a broader range of biological macromolecules.
• The developed system is a valuable tool for structural biology research under challenging pH conditions.