5-fluoro-D,L-tryptophan as a dual NMR and fluorescent probe of α-synuclein.

Analysis of conventional proton nuclear magnetic resonance (NMR) experiments on intrinsically disordered proteins (IDPs) is challenging because of the highly flexible and multiple rapidly exchanging conformations typifying this class of proteins. One method to circumvent some of these difficulties is to incorporate nonnative fluorine ((19)F) nuclei at specific sites within the polypeptide. (19)F NMR is particularly suitable for characterization of unfolded structures because (19)F chemical shifts are highly sensitive to local environments and conformations. Furthermore, the incorporation of fluorine analogs of fluorescent amino acids such as 5-fluoro-D: ,L: -tryptophan (5FW) allows for complementary studies of protein microenvironment via fluorescence spectroscopy. Herein, we describe methods to produce, purify, characterize, and perform steady-state fluorescence and 1D NMR experiments on 5FW analogs of the IDP α-synuclein.