Nucleic acid-polypeptide compositions and uses thereof

An oligonucleotide comprising a compound of Formula (IIa) at one of the termini:

• wherein;
• each R1 is independently substituted or unsubstituted C1-C6 alkyl, substituted or unsubstituted C1-C6 fluoroalkyl, or substituted or unsubstituted C1-C6 heteroalkyl;
• L1 is a bond, substituted or unsubstituted C1-C5 alkylene, substituted or unsubstituted C2-C5 alkenylene, or substituted or unsubstituted C2-C5 alkynylene;
• L2 is a bond, O, S, NR3, substituted or unsubstituted C4-C7 cycloalkylene, substituted or unsubstituted C4-C7 heterocycloalkylene, substituted or unsubstituted C5-C8 arylene, or substituted or unsubstituted C4-C8 heteroarylene;
• wherein R3, when present, is selected from hydrogen, unsubstituted or substituted C1-C6 alkyl, unsubstituted or substituted C1-C6 fluoroalkyl, unsubstituted or substituted C1-C6 heteroalkyl, unsubstituted or substituted monocyclic carbocycle, and unsubstituted or substituted monocyclic heterocycle;
• L3 is a bond, substituted or unsubstituted C1-C5 alkylene, substituted or unsubstituted C2-C5 alkenylene, or substituted or unsubstituted C2-C5 alkynylene;
• J is an internucleotide linking group linking to the adjacent nucleotide of the oligonucleotide;
• and
• wherein at least two of L1, L2 and L3 are not a bond.