Synthesis of the Model Peptides of the AGSGAG and minTBP-1 motifs.
To examine the binding mechanism of silk-TBP on the surface of TiO2 nonoparticles, the model peptides of the AGSGAG and minTBP-1 motifs, i.e., RKLPDA (minTBP-1) , (AGSGAG)2, AGSGAGGRKLPDAGGAGSGAG (Silk-TBP), and AGSG[1-13C]AGGRKLPD[3-13C]AGGAGSGAG (13C Silk-TBP) were synthesized in a stepwise fashion on Fmoc-amino acid-PEG-PS resin by a Pioneer Peptide Synthesis System (PE Biosystems, USA) using Fmoc solid phase method in our laboratory (Asakura et al., 2005; Asakura & Yao, 2002; Yu Suzuki et al., 2010; Yao et al., 2004). The purity was more than 95%, as verified by high-performance liquid chromatography and 13C solution NMR. The [1-13C]Ala (99.9%13C enrichment) and [3-13C]Ala (99.9% 13C enrichment) were purchased from Cambridge Isotopes Laboratories, Andover, MA, USA.