Patent ID: 7217575

Claim:
A single-layer protein system, comprising: (i) a protein being an avidin-type molecule selected from the group comprising native egg-white avidin, recombinant avidin, deglycosylated avidins, bacterial streptavidin, recombinant streptavidin, truncated streptavidin and other derivatives of said avidin-type molecules; (ii) two ligands I and II which bind with different affinities at the same binding site of said protein, wherein said ligand I is 4′-hydroxyazobenzone-2-carboxylic acid (HABA) or a HABA derivative, which is the low affinity ligand, and said ligand II is biotin, which is the high affinity ligand; and (iii) a molecule that recognizes the low affinity ligand I, wherein said molecule is an anti-HABA antibody or a biotinylated anti-HABA antibody, wherein in said single-layer protein system the high affinity ligand II is buried within the binding site of the protein (i) and the low affinity ligand I is covalently bound to the protein and associated with the molecule (iii) that recognizes it.