Residualizing linkers and uses thereof

A conjugate comprising a polypeptide linked to a detection agent, the conjugate having the structure:

• or a salt thereof,
• wherein A-NH— is a polypeptide;
• L1 and L2 are independently absent, optionally substituted C1-C6 alkyl, optionally substituted C1-C6 heteroalkyl optionally substituted C3-C10 cycloalkyl, optionally substituted aryl, optionally substituted C2-C100 polyethylene glycol;
• L3 is absent or optionally substituted C1-C6 alkyl;
• m is 0 or 1;
• R1 is hydrogen and R2 is —CH2CO2H or —CH2CH2CO2H, or R is —CH2CO2H or —CH2CH2CO2H and R2 is hydrogen;
• each R3 and R4 is hydrogen or R3 and R4 combine to form C═O;
• n is 0 or 1;
• o is 3;
• R5 is hydrogen or L4-B;
• R6 and R7 are independently hydrogen, optionally substituted C1-C6 heteroalkyl, or L4-B;
• L4 is optionally substituted C1-C6 alkyl, or optionally substituted C1-C6 heteroalkyl;
• B is an organic moiety comprising a detection agent;
• at least one of L1 and L2 is present and when L1 or L2 is absent, m is 0;
• and one and only one of R5, R6, and R7 is L4-B,
• wherein B has the structure:
• in which R8 is a radionuclide selected from the group consisting of 18F, 75Br, 76Br, 77Br, 123I, 124I, 125I, 131I, and 211At:
• or
• B has the structure:
• to which a metal is chelated.