Synthesis of a Fluorescent Probe for Sensing Multiple Protein States

Abstract

We synthesized solvatochromic thiol‐reactive fluorescent probes 6FM‐M and 7AFM‐M possessing two‐band emission. 7AFM‐M was designed to have a smaller dipole moment than 6FM‐M and as a result it showed better separation of the two emission bands. Both probes were used to label a cysteine mutant of α‐synuclein (αSyn), a presynaptic neuronal protein associated with Parkinson's disease. We investigated the ability of the probes to sense αSyn binding to lipid membranes and αSyn fibrillization, and compared their sensitivity with that of one‐band solvatochromic probes. We found that while all the tested probes can discriminate two αSyn states, only the 7AFM‐M probe is able to clearly discriminate all three protein states of αSyn: unstructured, membrane‐bound and fibrillar αSyn. Finally, using αSyn labelled with 7AFM‐M, we demonstrated that high density of αSyn on lipid membranes may lead to the partial membrane destruction with a formation of lipoprotein particles.