Scheme 2. Conjugation of the branched BBB-shuttle peptides to GFP via the formation of (a) a thioether linker or (b) a disulphide bridge. Spectra corresponding to the deconvoluted masses for the conjugates. For GFP-THRre_2m calc. MW = 32413 Da and found MW = 32414 Da; and for GFP-THRre_2c calc. MW = 32496 Da and found MW = 32492 Da. The same reactions were performed with the peptides containing one copy of the BBB-shuttle, obtaining GFP-THRre_1m and GFP-THRre_1c (Fig. S2†). DTNB = 5,5′-dithiobis-(2-nitrobenzoic acid).
