Synthesis and characterization of (1 ‐ 13C) Phe9 gramicidin A. Effects of side chain variations

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Abstract
The synthesis of (1‐13C)‐Phe9‐gramicidin (90% enriched) was carried out by the solid phase method. The peptide was removed from the resin by treatment with ethanolamine, deblocked, formylated and purified by preparative t.l.c. to obtain the gramicidin analog in an overall yield of 24%. The peptide was verified and characterized by high pressure liquid chromatography, carbon‐13 nuclear magnetic resonance, circular dichroism and single channel currents. Single channel conductances were found to be similar to those of (1‐13C)‐Phe11‐GB but significantly lower than that of gramicidin A. When this gramicidin analog was incubated with phospholipid, the characteristic channel spectrum was not obtained and interaction with sodium ion was not observed. A possible explanation for this behavior is discussed.