A luminescent receptor with affinity for N-terminal histidine in peptides in aqueous solution.
Crown ethers of suitable size are the perfect artificial host compounds for ammonium ion binding, but the rather low affinity in aqueous solution prevents their use at physiological conditions. We report here the synthesis and properties of a luminescent benzo crown ether with a pendant copper imidodiacetic acid complex, which coordinates with high affinity to histidine. The emission intensity of the benzo crown ether increases significantly in the presence of ammonium ions in methanol. At physiological conditions in buffered water at pH 7.5 these interactions are too weak to be detected. If an ammonium ion and an imidazole moiety are present in the analyte, such as in His-Lys-OMe or His-OMe, high binding affinity in aqueous solution is restored. The binding event is signaled by an increase in emission intensity, which can even be observed with the naked eye. This allows the selective detection of small peptides containing N-terminal histidine or histidine among all other amino acids at physiological conditions.
Kruppa
Michael
M
Institut für Organische Chemie, Universität Regensburg, D-93040 Regensburg, Germany.
Mandl
Christian
C
Miltschitzky
Stefan
S
König
Burkhard
B
D003300:Copper / Q000737:chemistry; D043844:Crown Ethers / Q000737:chemistry*; D006639:Histidine / Q000737:chemistry*; D007098:Imino Acids / Q000737:chemistry; D049408:Luminescent Agents / Q000737:chemistry*; D008958:Models, Molecular; D010455:Peptides / Q000737:chemistry*; D011485:Protein Binding; D012996:Solutions; D014867:Water / Q000737:chemistry
D043844:Crown Ethers; D007098:Imino Acids; D049408:Luminescent Agents; D010455:Peptides; D012996:Solutions; D014867:Water; D006639:Histidine; D003300:Copper; C008109:iminodiacetic acid