Fluorescent Hydrophobic Probes Based on Intramolecular Charge Transfer State for Sensitive Protein Detection in Solution

New hydrophobic intramolecular charge transfer probes, comprising an aminostyryl and a cyanopyranyl moieties, were developed for sensitive protein quantification in solution. The probes exhibited dramatic increase of fluorescence quantum yields with accompanying blue-shift of the emission when bound to protein–sodium dodecyl sulfate (SDS) complexes. Using this emission enhancement, the synthesized probes were successfully applied for determining protein concentrations in solution.