A new one-lane, four-dye DNA sequencing method was developed which is based on time-resolved detection and identification of fluorescently labeled primers. For fluorescent labels, we used two newly synthesized rhodamine derivatives (MR200-1, JA169), a new oxazine derivative (JA242), and a commercially available cyanine dye (CY5). The dye fluorescence was excited by a pulsed diode laser emitting at 630 nm. The fluorescence decay was detected by an avalanche photodiode using a single-filter system. The dyes used here, so-called multiplex dyes, can be distinguished and identified via their fluorescence decay patterns. The DNA fragments were labeled at the primer using linkers of various lengths and positions. For separation of the enzymatically generated DNA fragments, capillary gel electrophoresis (CGE) with a 5% linear polyacrylamide gel was employed. On covalent attachment to oligonucleotides, the dyes exhibit fluorescence decay times of 3.7 (MR200-1), 2.9 (JA169), 2.4 (JA242), and 1.6 ns (CY5) measured during CGE. The CGE mobility of the labeled DNA fragments could be controlled and nearly equalized by the coupling position and the linker length. First, time-resolved, one-lane, four-dye DNA sequencing runs in CGE are presented. The sequence information of 660 bp was determined with a probability of correct classification of > 90%. This result was obtained directly from the raw data without any of the mobility corrections that are necessary with other methods.

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Two 3′‐modified and three base‐modified ddNTPs were synthesized and tested with several DNA polymerases for incorporation activity. Starting from 3′‐azido‐3′‐deoxythymidine (AZT; 1), we were able to produce 3′‐deoxy‐3′‐isocyanato‐thymidine and 3′‐deoxy‐3′‐isothiocyanatothymidine (3 and 4, resp.) in a rapid synthesis based on the solid‐support approach (Scheme 1). These 3′‐functionalities could be used to attach a spacer molecule via urea and thiourea groups, respectively. Since the thus‐obtained tethered nucleotides 7 and 8 can be used to label with fluorescent dyes (cf. Scheme 5), they are convenient building blocks for practical applications in DNA sequencing. Furthermore, we synthesized, via 14 (Scheme 2), 17 (Scheme 3), and 19 (Scheme 4), the N4‐modified dideoxycytidine 5′‐triphosphate dye derivatives 22, 23, and 24, respectively, with different lengths of linkers between the base residue and the dye (Scheme 5). Base‐specific termination for the derivatives 22 and 24 was demonstrated (Fig. 2a and 2b).

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