Patent ID: 8133709

Claim:
A method of labeling a carrier molecule, comprising: a) providing a bonding partner comprising the carrier molecule and a target sequence, and b) contacting the bonding partner with a biarsenical molecule under conditions wherein the biarsenical molecule reacts with the target sequence, wherein the target sequence comprises Cys-Cys-X 1 -X 1 -X 2 -X 1 -X 3 -X 1 -X 1 -Cys-X 1 -Cys-X 2 (SEQ. ID NO: 3), wherein: X 1 is an amino acid having a non-polar side chain, X 2 is an amino acid having a basic side chain, and X 3 is an amino acid having a non-ionic polar side chain, and wherein the biarsenical molecule has the formula: and tautomers, anhydrides, and salts thereof; wherein: each X 1 or X 2 is independently Cl, Br, I, OR a , or SR a , or X 1 and X 2 together with the arsenic atom form a ring having the formula: R a is H, C 1 -C 4 alkyl, CH 2 CH 2 OH, CH 2 COOH, or CN; Z is 1,2-ethanediyl, 1,2-propanediyl, 2,3-butanediyl, 1,3-propanediyl, 1,2 benzenediyl, 4-methyl-1,2-benzenediyl, 1,2-cyclopentanediyl, 1,2-cyclohexanediyl, 3-hydroxy-1,2-propanediyl, 3-sulfo-1,2-propanediyl, or 1,2-bis(carboxy)-1,2-ethanediyl; Y 1 and Y 2 are each independently H or CH 3 , or Y 1 and Y 2 together form a ring such that the biarsenical molecule has the formula wherein: M is O, S, CH 2 , C(CH 3 ) 2 , or NH; R 1 and R 2 are each independently OR a , OAc, NR a R b , or H; R 3 and R 4 are each independently H, F, Cl, Br, I, OR a , or R a ; or R 1 together with R 3 , or R 2 together with R 4 , or both, form a ring in which (i) one of R 1 or R 3 is C 2 -C 3 alkyl and the other is NR a and (ii) one of R 2 and R 4 is C 2 -C 3 alkyl and the other is NR a ; R b is H, C 1 -C 4 alkyl, CH 2 CH 2 OH, CH 2 COOH, or CN; Q is CR a R b , CR a OR b , C═O, or a spirolactone having the formula: wherein the Spiro linkage is formed at C 1 .