| 主权项 |
1. A linker unit comprising, a center core, a plurality of linking arms, and optionally a coupling arm, wherein,
the center core comprises, (1) a first polypeptide comprising a plurality of lysine (K) residues, wherein each K residue and its next K residue are separated by a filler sequence comprising glycine (G) and serine (S) residues, and the number of K residues ranges from 2 to 15; or (2) a second polypeptide comprising the sequence of (Xaa-K)n, where Xaa is a PEGylated amino acid having 2 to 12 repeats of ethylene glycol (EG) unit, and n is an integral from 2 to 15; the plurality of linking arms are respectively linked to the K residues of the center core, each of the plurality of linking arms has a maleimide group at its free terminus; and the amino acid residue at the N- or C-terminus of the center core has an azide or an alkyne group; or the amino acid residue at the N- or C-terminus of the center core is a cysteine residue, and the thiol group of the cysteine residue is linked with the coupling arm having the azide, the alkyne, a tetrazine or a strained alkyne group at the free terminus of the coupling arm. |
