The present invention relates to methods for coupling labels to particular target moieties. The coupling reactions of the present invention use temporal spacing of the reactants through phase change (i.e. by rapid freezing) to control the initiation and termination of reaction. This process results in a simplified and improved method for linking labels to specific binding moieties using N-hydroxysuccinimide chemistry. The present invention further relates to kits comprising all necessary components to easily and rapidly make protein conjugates.
