The peptides were synthesized using a PS3 automatic synthesizer (Protein Technologies Inc, Tucson, AZ) and labeled with Cy5.5, a near-infrared red (NIR) fluorophore (cyanine5.5 NHS ester, #27020; Lumiprobe, Hunt Valley, MD ), on the C-terminus using a GGGSK linker (14 (link)). The peptides were purified to >99% by HPLC and lyophilized for storage at −80 °C.