A compound having a structure according to Formula I: wherein each Z is independently selected from O and S; L 3 is substituted or unsubstituted heteroalkyl; and R 19, R 20, R 21 and R 22 are independently selected from H, hydroxy, carboxy, amine, amide, ester and a linker; L 1, L 2, L 4 and L 5 are independently selected from substituted or unsubstituted alkyl, substituted or unsubstituted heteroalkyl, substituted or unsubstituted cycloalkyl, substituted or unsubstituted heterocycloalkyl, substituted or unsubstituted aryl and substituted or unsubstituted heteroaryl; at least one of L 1, L 2, L 3, L 4 and L 5 comprises -L 11 -X, wherein L 11 is selected from a bond, acyl, substituted or unsubstituted alkyl, substituted or unsubstituted heteroalkyl, substituted or unsubstituted cycloalkyl, substituted or unsubstituted heterocycloalkyl, substituted or unsubstituted aryl and substituted or unsubstituted heteroaryl; and X is a reactive functional group; A 1, A 2, A 3 and A 4 are each independently: wherein each R 1 is independently selected from H, an enzymatically labile group, a hydrolytically labile group, a metabolically labile group, a photolytic group and a single negative charge; and each R 5 and R 6 is independently selected from H, substituted or unsubstituted alkyl, substituted or unsubstituted heteroalkyl, halogen, CN, CF 3, acyl, -SO 2 NR 17 R 18, -NR 17 R 18, -OR 17, - S 2 R 17, -COOR 17, -S 2 OR 17, -OC R 17, -C NR 17 R 18, -NR 17 C R 18, -NR 17 SO 2 R 18, and -NO 2, wherein R 5 and R 6 are optionally joined to form a ring system which is a member selected from substituted or unsubstituted cycloalkyl, substituted or unsubstituted heterocycloalkyl, substituted or unsubstituted aryl and substituted or unsubstituted heteroaryl; and R 17 and R 18 are independently selected from H, substituted or unsubstituted alkyl, substituted or unsubstituted heteroalkyl, substituted or unsubstituted cycloalkyl, substituted or unsubstituted heterocycloalkyl, substituted or unsubstituted aryl and substituted or unsubstituted heteroaryl; R 17 and R 18, together with the atoms to which they are attached, are optionally joined to form a 5- to 7-membered ring. wherein each Z is independently selected from O and S; L 3 is substituted or unsubstituted heteroalkyl; and R 19, R 20, R 21 and R 22 are independently selected from H, hydroxy, carboxy, amine, amide, ester and a linker; L 1, L 2, L 4 and L 5 are independently selected from substituted or unsubstituted alkyl, substituted or unsubstituted heteroalkyl, substituted or unsubstituted cycloalkyl, substituted or unsubstituted heterocycloalkyl, substituted or unsubstituted aryl and substituted or unsubstituted heteroaryl; at least one of L 1, L 2, L 3, L 4 and L 5 comprises -L 11 -X, wherein L 11 is selected from a bond, acyl, substituted or unsubstituted alkyl, substituted or unsubstituted heteroalkyl, substituted or unsubstituted cycloalkyl, substituted or unsubstituted heterocycloalkyl, substituted or unsubstituted aryl and substituted or unsubstituted heteroaryl; and X is a reactive functional group; A 1, A 2, A 3 and A 4 are each independently: wherein each R 1 is independently selected from H, an enzymatically labile group, a hydrolytically labile group, a metabolically labile group, a photolytic group and a single negative charge; and each R 5 and R 6 is independently selected from H, substituted or unsubstituted alkyl, substituted or unsubstituted heteroalkyl, halogen, CN, CF 3, acyl, -SO 2 NR 17 R 18, -NR 17 R 18, -OR 17, - S 2 R 17, -COOR 17, -S 2 OR 17, -OC R 17, -C NR 17 R 18, -NR 17 C R 18, -NR 17 SO 2 R 18, and -NO 2, wherein R 5 and R 6 are optionally joined to form a ring system which is a member selected from substituted or unsubstituted cycloalkyl, substituted or unsubstituted heterocycloalkyl, substituted or unsubstituted aryl and substituted or unsubstituted heteroaryl; and R 17 and R 18 are independently selected from H, substituted or unsubstituted alkyl, substituted or unsubstituted heteroalkyl, substituted or unsubstituted cycloalkyl, substituted or unsubstituted heterocycloalkyl, substituted or unsubstituted aryl and substituted or unsubstituted heteroaryl; R 17 and R 18, together with the atoms to which they are attached, are optionally joined to form a 5- to 7-membered ring.