Abstract
The amino acid sequence of vanillin-binding site of transient receptor potential vanilloid type 1 from rat, Leu544–Tyr553, was extracted and hybridized with His-tag. The hexadecamer invariant chain peptide, Leu-Ala-Met-Gly-Trp-Thr-Asn-Met-Leu-Tyr-His-His-His-His-His-His (VBH), was prepared by solid-phase peptide synthesis. Circular dichroic spectral measurements determined the α-helix content to be 17%, which was consistent to that of short peptides. In a combined use of thiol-derivatized nitrilotriacetic acid (s-NTA) monolayers, the His-tag successfully attached the whole peptide on gold substrate surfaces through Ni2+-chelation (ΓVBH = 224 ± 120 pmol cm-2, n = 8). Moreover, various surface analyses including atomic force microscopy imaging, FT-IR spectroscopy, and quartz-crystal microgravimetry (QCM) revealed self-assembly (SA) of VBH at the S-NTA monolayer surfaces. QCM measurements also showed that vanillin, the major component of natural vanilla flavoring, binds to VBH SAs (Kapp = 2.7 × 103 M–1). The affinity of host–guest binding remains limited but possesses a certain degree of selectivity; for cases of structural analogs that give a pleasant flavor, acetophenone showed rather weak affinity (Kapp = 2.8 × 102 M–1) whereas 4-heptanone did not bind at all. With these results VBH was concluded to be useful in vanillin sensing as a supramolecular affinity host.
