Through-bond energy transfer cassettes based on a fluorescein donor component electronically conjugated to rhodamine-like acceptors have been designed and synthesized. They absorb strongly at 488 nm (Ar-laser emission) and efficiently transfer the energy to the acceptor component that emits strongly. Further, the cassettes are more stable to photobleaching than fluorescein, making them potentially more suitable for single-molecule detection methods than fluorescein itself. These studies form the basis for improved detection of chain-terminated DNA in high-throughput sequencing and other applications in biotechnology.