One- and Two-DimensionallH NMR Study of the Substance P Fragment ARG-PRO-LYS-PRO

Abstract
The Substance P fragment Arg1Pro2-Lys3-Pro4 (SP1–4) has been extensively investigated by means of proton nuclear magnetic resonance at 400 MHz. The combined application of different 2D techniques and a comparison of SP1–4 with its derivative SPM-amide allowed the complete and unambiguous assignment of the proton NMR spectrum. Conformational data obtained from the different NMR parameters are compared with theoretical calculations. The results suggest that SP1–4 exists, at the chosen experimental conditions, as a stretched molecule.