Table 1. Peptide Sequences and NTS₁R Affinities of 1–9, 11, and 12, as Well as Stabilities of 1–9, 11, and 12 in Human Plasma/PBS (1:2 v/v) (37 °C).

			% intact peptide in plasmab after the specified incubation times:
compd	sequence	Ki [nM] NTS1Ra	10 min	30 min	1 h	2 h	6 h	24 h	48 h
1	Arg-Arg-Pro-Tyr-Ile-Leu	0.33 [0.35, 0.31] (lit. 0.14c)	23.1 ± 0.2	n.d.	<1	n.d.	n.d.	<1	<1
2	Arg-Arg-Pro-Tyr-Tle-Leu	1.17 [1.17, 1.17]	10.8 ± 0.5	n.d.	<1	n.d.	n.d.	<1	<1
3	N(Me)-Arg-Arg-Pro-Tyr-Ile-Leu	0.223 ± 0.005(lit. 0.29d)	92.1 ± 0.1	88.2 ± 0.2	79.7 ± 0.1	70.8 ± 0.1	n.d.	n.d.	n.d.
4	Arg-N(Me)-Arg-Pro-Tyr-Ile-Leu	0.29 ± 0.03(lit. 0.51e)	>99	93.6 ± 0.1	83.7 ± 0.3	66.4 ± 0.1	n.d.	n.d.	n.d.
5	Arg-Arg-Pro-N(Me)-Tyr-Ile-Leu	>1,000(lit. 5,100e)	22.9 ± 0.2	<1	<1	<1	n.d.	n.d.	n.d.
6	Arg-Arg-Pro-Tyr-N(Me)-Ile-Leu	60 ± 5(lit. 160e)	2.6 ± 0.5	<1	<1	<1	n.d.	n.d.	n.d.
7	N(Me)-Arg-Arg-Pro-Tyr-Tle-Leu	0.88 ± 0.13	n.d.	n.d.	>99	n.d.	>99	98.3 ± 0.8	86.8 ± 0.3
8	Arg-N(Me)-Arg-Pro-Tyr-Tle-Leu	1.6 ± 0.1	n.d.	n.d.	>99	n.d.	>99	>99	>99
9	Arg-Arg-Pro-Tyr-Ile-N(Me)-Leu	880 ± 260(lit. 190e)	39.9 ± 0.9	<1	<1	<1	n.d.	n.d.	n.d.
11	Propionyl-Arg-Arg-Pro-Tyr-Ile-Leu	1.0 ± 0.2	>99	84.0 ± 0.1	71.8 ± 0.2	32.4 ± 0.1	n.d.	n.d.	n.d.
12	Propionyl-Arg-Arg-Pro-Tyr-Tle-Leu	18 ± 2	n.d.	n.d.	>99	n.d.	>99	>99	92.5 ± 0.9

^aDetermined by radioligand competition binding with [³H]13 at HT-29 cells; mean values from two (1, 2), three (3, 4) or four (6–9, 11, 12) independent experiments, each performed in triplicate (for n > 2 K_i values are given ± SEM; in the case of n = 2 individual K_i values are given in square brackets).

^bThe initial concentration of the peptides in plasma/PBS (1:2 v/v) was 100 μM; presented are mean values ± SEM from three independent experiments (SEM not given if no decomposition was observed).

^cKeller et al.⁴²

^dOrwig et al.³⁴

^eHärterich et al.³³ n.d. = not determined.