Conjugates of a cargo molecule with a transporter molecule are disclosed, where the cargo molecule and the transporter molecule are linked covalently by a releasable linker. The cargo of the conjugate can be a biologically active agent or a reporter molecule. The transporter modulates the transport of the cargo across a biological barrier (e.g., a cell membrane) compared to the transport of the unconjugated cargo. Releasable linkers suitable for rapid and facile conjugation to various types of cargo and transporters are also disclosed, along with methods for using the linkers in the synthesis of conjugates.
