The invention relates to a method for determining the conformational state of a protein, comprising the steps of: a) providing a first binding partner which is capable of binding to the protein in a manner dependent on the conformational state of the protein and which generates a signal in a manner dependent on the binding of the first binding partner to the protein; and b) contacting the protein with the first binding partner and determining the conformational state of the protein by assessing the labelling of the protein by the binding of the first binding partner.