Novel compounds consisting of a nucleotide triphosphate labeled with a PEG linker and various terminal groups attached to the gamma-phosphate of the nucleotide were constructed for use in efforts to produce a new class of DNA sequencer. The stability of these novel compounds was investigated to determine their utility as sequencing reagents. Hydrolysis rate constants were measured for both the natural nucleoside triphosphate dATP and novel dATP derivatives. The gamma-labeled dATP was approximately 20-fold more stable to hydrolysis than dATP.