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SUMMARYNorleucine''-substance P and 4-chlorophenylalanine 7;8-Norleucine 11 -. .substance P were synthesized by fragment condensation. Phel H/7*8-norleuc 7 r i e l l -substance P was obtained by catalytic tritiation of the precursor geptide with a specific radioactivity of 27 Cilmole and full biological activity.Recently we reported the tritium labelling of the modified 3 * partial sequence of substance P, acetyl-Lys-Phel HI-Phe-Gly-Leu-NleNH2, by catalytic tritiation of the corresponding synthetic Cpa-containing precursor peptide 111. The labelled peptide was purified using preparative paper electrophoresis and possessed a specific radioactivity of 23 Ci/mmole 111 -a surprisingly high labelling rate for the tritiation of a 4-chlorophenylalanine peptide. The labelled compound had high biological activity in vivo but in receptor studies no specific binding

CD spectra of substance P (SP) and its C‐terminal partial sequences have been measured in diluted aqueous solution including variation of hydrogen ion concentration. In the far u.v. region there is an overlapping of the amide CD absorption by the CD of the phenylalanine residue aromatic side chains (217–220 nm). This complex CD absorption is reduced during changes from acidic to alkaline pH, especially in those cases where a phenylalanine residue is at the N‐terminus of the peptide chain. These CD changes dependent on pH are due more to charge effects on the aromatic chromophores than to substantial conformational changes. However, solvation effects on the conformational features of SP peptides caused by the deprotonation of the amino groups have to be taken into account. CD and potentiometric titrations indicate that the N‐terminal α‐amino groups of the SP peptides in general are freely accessible to the solvent. Our studies did not give any evidence of the occurrence of ordered structures of SP peptides in diluted aqueous solution.

Zur Untersuchung des Einflusses von Modifikationen der Polyamidkette auf die Konformation und die biologische Aktivität des Oxytocins wurden 9‐NHGly‐OT‐, 9‐Azgly‐OT und 5‐Azasn‐OT synthetisiert. Zur Synthese des C‐terminalen Hexapeptides wurden aktivierte Tripeptidester eingesetzt. Die 3 + 6‐Azidsynthese erwies sich auch hier einer 6 + 3‐Synthese überlegen.

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