Rink amide mbha resin

All peptides were synthesized on rink-amide-MBHA resin purchased from Peptides International (Louisville, KY, USA). Fmoc-protected amino acid residues were purchased from CreoSalus (Louisville, KY, USA). Peptides were synthesized using standard Fmoc-chemistry on solid phase using a Focus XC autosynthesizer from Aapptec (Louisville, KY, USA). The 5(6)-carboxyfluorescein tag, from Sigma-Aldrich (St. Louis, MO, USA), was conjugated manually on resin using HBTU chemistry. Peptides containing the nitrobenzyl (NB) cage group were synthesized as previously described.^{7 (link)} Crude peptides were cleaved from resin using a mixture of 95% trifluoroacetic acid (TFA), 2.5% triisopropylsilane (TIS), and 2.5% water, before purification by an Agilent Prep-Star HPLC instrument (Santa Clara, CA, USA) equipped with an Agilent Zorbax SB C-18 analytical column (Santa Clara, CA, USA). A mixture of water (0.1% TFA) and acetonitrile (0.1% TFA) in a linear gradient (5–50% acetonitrile in 45 min) was used as a mobile phase during HPLC. The molecular weights of the purified peptides were verified using matrix assisted laser desorption/ionization time-of-flight (MALDI-TOF) MS on a Bruker UltrafleXtreme (Billerica, MA, USA) (Table S1). The peptide conformation was studied by Circular Dichroism (CD) on a Jasco J-1500 CD spectrometer (Easton, MD, USA) following a previously reported protocol.^{7 (link)}