Compositions comprising a dehalogenase substrate and a radionuclide and methods of use

A method to label a cell, comprising:

• contacting a cell comprising a mutant dehalogenase with a dehalogenase substrate which comprises a radionuclide,
• wherein the mutant dehalogenase comprises at least one amino acid substitution relative to a corresponding wild-type dehalogenase, wherein at least one amino acid substitution results in the mutant dehalogenase forming a bond with the substrate which is more stable than the bond formed between the corresponding wild-type dehalogenase and the substrate, wherein at least one amino acid substitution in the mutant dehalogenase is a substitution at an amino acid residue in the corresponding wild-type dehalogenase that is associated with activating a water molecule which cleaves a bond formed between the corresponding wild-type dehalogenase and the substrate or at an amino acid residue in the corresponding wild-type dehalogenase that forms an ester intermediate with the substrate,
• wherein the substrate is a compound of formula (I):
• R-linker-A-X, wherein R comprises the radionuclide, the linker is a multiatom straight or branched chain including C, N, S and/or O, wherein A-X is a substrate for the dehalogenase, wherein A is (CH2)n and n=2-10, and X is a halogen.

A method to detect or determine the presence or amount of a mutant dehalogenase, comprising:

• a) contacting a mutant dehalogenase with a dehalogenase substrate which comprises a radionuclide, wherein the mutant dehalogenase comprises at least one amino acid substitution relative to a corresponding wild-type dehalogenase, wherein the at least one amino acid substitution results in the mutant dehalogenase forming a bond with the substrate which is more stable than the bond formed between the corresponding wild-type dehalogenase and the substrate, wherein the at least one amino acid substitution in the mutant dehalogenase is a substitution at an amino acid residue in the corresponding wild-type dehalogenase that is associated with activating a water molecule which cleaves the bond formed between the corresponding wild-type dehalogenase and the substrate or at an amino acid residue in the corresponding wild-type dehalogenase that forms an ester intermediate with the substrate, wherein the substrate is a compound of formula (I):
• R-linker-A-X, wherein R comprises the radionuclide, the linker is a multiatom straight or branched chain including C, N, S and/or O, wherein A-X is a substrate for the dehalogenase, wherein A is (CH2)n and n=2-10, and X is a halogen;
• and
• b) detecting or determining the presence or amount of the contrast agent, thereby detecting or determining the presence or amount of the mutant dehalogenase.