Sample preparation for photolysis

The first step in an actual photoaffinity labeling experiment is to allow the ligand to bind to its receptor. In most cases the experimenter wishes to 

The reversible binding of a ligand to a receptor a hypothetical case (Kj = I 6 M) 

Receptor concentration (pM) Total ligand concentration M) % Total ligand bound to receptor % Receptor sites occupied 

Occasionally, the poor solubility of the reagent in aqueous solution is a problem. It usually proves possible to circumvent this difficulty by adding the ligand to the solution of receptor in a small amount of an organic solvent that is miscible with water such as ethanol, dioxane, dimethylsulfoxide or 

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