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. 2012 Nov 8;7(11):e49070. doi: 10.1371/journal.pone.0049070

Figure 1. Synthesis and FTIR spectra of KV1 polypeptide.

Figure 1

A. Membrane-spanning topology of Shaker Kv channel. Colored regions denote domains within the KV1 polypeptide (green, S4, S5 and S6; blue, S4–S5 linker) and the ID peptide (red). B. The three short peptides (numbered 1, 2 & 3) joined by solid-phase fragment condensation synthesis to construct the 119-residue KV1 polypeptide. Primary structure, proposed structural/functional domains and S4 positive charges are indicated. C. Schematic representation of solid phase fragment condensation synthesis of the KV1 polypeptide: (1) First protected 40-residue fragment is assembled on solid support; (2) α-amino group is deprotected; (3) Second protected 40-residue fragment reacts; (4) Deprotection is repeated; (5) Third protected 39-residue fragment reacts (6) Full-length KV1 polypeptide is deprotected and cleaved from support. ▪ = protecting group; • = side chain protecting group; Λ = linker to solid support. D. Second derivative FTIR spectrum of KV1 polypeptide (10 mg/ml) in 25 mM SDS at 30°C. Peptide was solubilized by simple mixing with SDS in deuterated PBS. E. Second derivative FTIR spectrum of KV1 polypeptide (10 mg/ml) in 25 mM SDS at 30°C. Peptide was prepared as a thin-film, then reconstituted by adding a thin film of SDS, before solubilization in deuterated PBS. F. Second derivative FTIR spectrum of KV1 polypeptide (10 mg/ml) in 50 mg/ml lysophosphatidylcholine (LPC) at 30°C. Peptide was prepared as a thin-film, then reconstituted by adding a thin film of LPC, before solubilization in deuterated PBS. G. Second derivative FTIR spectrum of KV1 polypeptide (10 mg/ml) in 50 mg/ml DMPC at 30°C. Peptide was prepared as a thin-film, then reconstituted by adding a thin film of DMPC, before solubilization in deuterated PBS.