HeavyPeptides, from Thermo Electron Corp., are isotopically-labeled, non-radioactive custom peptides for Mass Spectrometry (MS) and Nuclear Magnetic Resonance (NMR) Spectroscopy applications. They can be used as sequence-identical internal weight standards for quantitation of proteins and protein mixtures. HeavyPeptide AQUA kits can now be prepared with covalent modifications, such as phosphorylation, which are chemically identical to naturally occurring post-translational modifications (PTMs). The kits provide precision of ۯ% for techniques where there is a need for absolute quantification. Phosphorylation modification is also available on the HeavyPeptide BASIC range, which provides a suitable platform for high-throughput, pre-quantitative screening and relative quantification. Thermo Electron Corp.800-532-4752 www.thermo.com