Detergent-mediated cryoprotection: Optimizing freezing and storage conditions for G protein-coupled receptors

Cryoprotection is a widely employed approach in biophysical research for preserving protein integrity during storage and experimental analysis. While cryoconditions are generally considered optimal for preserving proteins, the freezing process can significantly alter solution properties, leading to protein denaturation or aggregation. To mitigate these detrimental effects, various cryoprotectants, such as glycerol or carbohydrates, are used. Membrane proteins, however, present unique challenges due to their reliance on specific lipid-like environments for structural integrity and function. While established protocols are optimized for soluble proteins, the cryoprotection of membrane proteins remains poorly understood, often necessitating researchers to avoid freezing these proteins in their studies. Here, we investigate and optimize freezing conditions for membrane proteins, focusing on A2A adenosine receptor (A_2AAR)-a representative G protein-coupled receptor (GPCR)-known for its environmental sensitivity. Our findings demonstrate that the appropriate detergent environment provides protection against cryogenic damage, enabling the successful freezing and long-term storage of GPCRs, preserving their structural and functional integrity.