Methods for target molecule detection using siderophores and related compositions

A method for determining the presence of a target molecule in a biological sample at physiological pH, comprising:

• (a) contacting a biological sample with a capture agent at physiological pH, the capture agent comprising a hydroxamate siderophore complexed with a transition metal cation as a binding moiety, under conditions wherein the binding moiety of the capture agent is capable of selectively binding a target molecule to form a target molecule-capture agent complex, wherein the target molecule is selected from the group consisting of a phosphorylated molecule, a nitrotyrosine-containing molecule and a sulfated molecule, and
• (b) detecting formation of the target molecule-capture agent complex in the biological sample at physiological pH, thereby determining the presence of the target molecule in the biological sample;
• wherein the biological sample is not washed or purified prior to detecting formation of the target molecule-capture agent complex in the biological sample.