To test the affinity between protein A and multiple small molecules.

Technical difficulties

· The wild-type protein A tends to precipitate upon addition of high concentrations of reducing agents, rendering it unsuitable for SPR testing.

· The protein gradually loses activity during the testing process.

Solution

· By analyzing the protein sequence, truncating the protein, and introducing mutations to surface cysteine residues, a stable protein was obtained.

· Initially, protein A was immobilized on the chip via amino coupling, but during the testing process, the protein gradually lost activity. Subsequently, protein capture was achieved using anti-His antibodies to immobilize the protein on the chip, ensuring its activity throughout the testing process.

Results