Fluorescent dyes and their uses as biomarkers

A nucleotide of the formula:

• wherein B is a purine, deazapurine or pyrimidine;
• L is a cleavable linker;
• R′ is monophosphate, diphosphate or triphosphate;
• R″ is a 3′-OH blocking group;
• R′″ is H or OH;
• and
• Dye is of the structure:
• or a salt or mesomeric form thereof,
• wherein each R1, R1′ and R2 is independently selected from the group consisting of H, alkyl, substituted alkyl, alkoxy, alkenyl, alkynyl, haloalkyl, haloalkoxy, alkoxyalkyl, amino, aminoalkyl, aminosulfonyl, halo, cyano, hydroxy, hydroxyalkyl, heteroalkyl, C-carboxy, O-carboxy, C-amido, N-amido, nitro, sulfonyl, sulfo, sulfino, sulfonate, sulfonyl halide, S-sulfonamido, and N-sulfonamido;
• alternatively, R1 and R1′ together and with the atoms to which they are attached form a ring or ring system selected from the group consisting of optionally substituted carbocyclyl, optionally substituted aryl, optionally substituted heteroaryl, and optionally substituted heterocyclyl;
• each R3 and R4 is independently selected from the group consisting of H, alkyl, substituted alkyl, alkenyl, alkynyl, aminoalkyl, haloalkyl, heteroalkyl, alkoxyalkyl, sulfo, optionally substituted aryl, optionally substituted heteroaryl, optionally substituted carbocyclyl, and optionally substituted heterocyclyl;
• alternatively, R1 and R3 together with the atoms to which they are attached form a ring or ring system selected from the group consisting of optionally substituted 5-10 membered heteroaryl or optionally substituted 5-10 membered heterocyclyl;
• alternatively, R2 and R4 together with the atoms to which they are attached form a ring or ring system selected from the group consisting of optionally substituted 5-10 membered heteroaryl and optionally substituted 5-10 membered heterocyclyl;
• RHet is a 5-10 membered heteroaryl optionally substituted with one or more R5;
• each R5 and R6 is independently selected from the group consisting of alkyl, substituted alkyl, alkoxy, alkenyl, alkynyl, haloalkyl, haloalkoxy, alkoxyalkyl, amino, aminoalkyl, aminosulfonyl, halo, cyano, hydroxy, hydroxyalkyl, heteroalkyl, C-carboxy, O-carboxy, C-amido, N-amido, nitro, sulfonyl, sulfo, sulfino, sulfonate, sulfonyl halide, S-sulfonamido, and N-sulfonamido;
• Y is O or NH;
• and
• n is an integer of 0 to 4.