Capture compounds, collections thereof and methods for analyzing the proteome and complex compositions

A capture compound of formula:

• wherein:
• X is a reactivity function that covalently binds to amino acid side chains of proteins;
• Y, the selectivity function, interacts non-covalently with proteins and modulates one or more of the affinity, steric properties and electronic properties of the capture compound thereby increasing selectivity of the binding by X to the amino acid side chains of the proteins, whereby X covalently binds to fewer side chains of the proteins when Y is present than in its absence;
• Q permits separation or immobilization of the capture compound and is selected from among biotin, 6-His, an oligonucleotide, BODIPY, an adhesive peptide, and peptide nucleic acid (PNA);
• Z is a trityl derivative for presenting functional moieties X, Y and Q;
• and Z has the formula:
• any two of moieties Q, X and Y are attached to the phenyl rings, and the remaining moiety is attached to the central carbon atom;
• wherein one or more of X, Y or Q is optionally attached to a spacer moiety.