Molecular sensor for nmr/mri based on analyte-dependent spectral changes of temporarily encapsulated hyperpolarized 129xe

A precursor or a molecular sensor selected from:

• A) a precursor for a molecular sensor for determining analyte concentrations and/or measuring analyte concentration changes
• comprising
• (a) a host for an active nucleus,
• wherein said host enables at least a transient binding of said active nucleus that produces a detectable NMR signal when the sensor binds to the analyte,
• (b) an NMR-modulating moiety,
• wherein said NMR-modulating moiety changes the resonance frequency or the chemical exchange saturation transfer (CEST) signal of the active nucleus-host complex,
• and
• (c) an interaction moiety,
• wherein said interaction moiety specifically responds to an environment parameter, an analyte or a target molecule that binds the analyte
• or said interaction moiety specifically binds to a target molecule in an analyte-dependent manner,
• wherein the analyte is a metal a peptide or a protein, wherein the NMR-modulating moiety (b) and the interaction moiety (c) reversibly suppress, or are capable of reversibly suppressing, a CEST signal from the otherwise accessible host by a specific conformation of the NMR-modulating moiety (b) in the host vicinity, and an interaction of the interaction moiety (c) with a target molecule in an analyte-dependent manner unsuppresses the CEST-signal;
• and
• B) a molecular sensor for determining analyte concentrations and/or measuring analyte concentration changes in a cell,
• comprising
• an active nucleus,
• and said precursor of part A),
• wherein the analyte is a metal or a peptide or a protein.