Click and analyze: The titled probe was synthesized by conjugating a sulfonyl fluoride and azido unit using click chemistry to give SF-Eu, which can react specifically with serine (Ser) in the active site of serine protease (SP). Combination of the method with 153Eu-isotope dilution ICP/MS enables absolute protein quantification of active SPs in biological samples using only one 153Eu(NO3)3 isotopic standard. Copyright 漏 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
