Acyclovir triphosphate sodium is a labeled modified deoxyoligonucleotide (dNTP) that can release pyrophosphate to produce fluorescence and has special applications in gene synthesis and sequencing[1].
References
[1] Innis MA, et al. DNA sequencing with Thermus aquaticus DNA polymerase and direct sequencing of polymerase chain reaction-amplified DNA. Proc Natl Acad Sci U S A. 1988 Dec;85(24):9436-40. DOI:10.1073/pnas.85.24.9436