Methods and compositions for labeling nucleic acids

A nucleic acid polymer comprising at least one first nucleotide analogue attached to a first label and at least one second nucleotide analogue attached to a second label, wherein said nucleic acid polymer is prepared by a method of dually labeling a nucleic acid polymer, comprising steps of:

• providing a nucleic acid polymer comprising at least one first nucleotide analogue that comprises a first reactive unsaturated group and at least one second nucleotide analogue that comprises a second reactive unsaturated group;
• contacting the nucleic acid polymer with a first reagent comprising a third reactive unsaturated group attached to a first label, such that a [3+2] cycloaddition occurs between the first and third unsaturated groups;
• and
• contacting the nucleic acid polymer with a second reagent comprising a fourth reactive unsaturated group attached to a second label, such that a [3+2] cycloaddition occurs between the second and fourth unsaturated groups.

A kit for dually labeling a nucleic acid polymer, comprising

• at least one first nucleoside analogue that comprises a first reactive unsaturated group;
• at least one second nucleoside analogue that comprises a second reactive unsaturated group;
• a first reagent comprising a third reactive unsaturated group attached to a first label;
• and
• a second reagent comprising a fourth reactive unsaturated group attached to a second label;
• wherein the first reactive unsaturated group comprises a first 1,3-dipole, the third reactive unsaturated group comprises a first dipolarophile, and the first and third reactive unsaturated groups can react via [3+2] cycloaddition and wherein the second reactive unsaturated group comprises a second dipolarophile, the fourth reactive unsaturated group comprises a second 1,3-dipole, and the second and fourth reactive unsaturated groups can react via [3+2] cycloaddition, or
• wherein the first reactive unsaturated group comprises a first dipolarophile, the third reactive unsaturated group comprises a first 1,3-dipole, and the first and third reactive unsaturated groups can react via [3+2] cycloaddition and wherein the second reactive unsaturated group comprises a second 1,3-dipole, the fourth reactive unsaturated group comprises a second dipolarophile, and the second and fourth reactive unsaturated groups can react via [3+2] cycloaddition.