Cover Picture: Fluorogenic Sequencing Using Halogen‐Fluorescein‐Labeled Nucleotides (ChemBioChem 8/2015)

The cover picture shows the fluorogenic sequencing-by-synthesis process. Nonfluorescent terminal phosphate-labeled fluorogenic nucleotides (TPFLNs) release fluorophores upon incorporation by polymerase and phosphate digestion by phosphatase. Polymerase incorporates the matched (correct Watson–Crick pairing) fluorogenic bases onto the DNA template with annealed primers and rejects mismatched TPLFNs, thereby affording sequencing information. A new class of halogen-modified fluorescein derivatives has been developed for red-shifting the fluorescence emission to longer wavelength, thereby eliminating spectral overlap between the fluorogenic emission and the background fluorescence of the sequencing chip. For more details, see the communication by H. Duan, Y. Huang and co-workers on p. 1153 ff.