Table 1.
Physico-chemical properties and sst1-5 binding affinities (IC50s, nM) of the analogues and control peptide ODT-8 (1)
| ID# | Compound | Purity | MSc | IC50 nmd | Number of atoms in the cycle | ||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| HPLCa | CZEb | Mcalc | M+Hobs | sst1 | sst2 | sst3 | sst4 | sst5 | |||
| Somatostatin-28 (SRIF-28) | 99 | 99 | 3145.45 | 3146.46 | 3.2 ± 0.3 (16) | 2.6 ± 0.3 (18) | 3.8 ± 0.6 (16) | 3.4 ± 0.3 (16) | 3.2 ± 0.5 (16) | 38 | |
| 1* | ODT-8 [H-c(Cys3-Phe6-Phe7-dTrp8-Lys9-Thr10-Phe11-Cys14)-OH] (SRIF numbering) | 95 | 98 | 1078.45 | 1078.90 | 27 ± 3.4 (4) | 41 ± 8.7 (6) | 13 ± 3.2 (4) | 1.8 ± 0.7 (4) | 46 ± 27 (3) | 26 |
| 2 | [dCys3]-ODT-8 | 99 | 99 | 1078.44 | 1079.48 | 14 (11; 17) | 14.5 (15; 14) | 4.5 (4.4; 4.6) | 1.0 (1.2; 0.8) | 9.5 (11; 7.9) | 26 |
| 3* | [dCys14]-ODT-8 | 99 | 99 | 1078.44 | 1079.23 | >1K (2) | 18 (17; 19) | 18.5 (20; 17) | 8.2 (9; 7.3) | 27 (29; 24) | 26 |
| 4 | [dCys3, dCys14]-ODT-8 | 99 | 99 | 1078.44 | 1079.36 | >1K (2) | 11 (9; 12) | 6.3 (6; 6.6) | 2.6 (2.8; 2.4) | 8.7 (8.6; 8.8) | 26 |
| 5 | Ac-ODT-8 | 99 | 99 | 1120.45 | 1121.29 | 22 ± 8.8 (3) | 49 ± 9 (4) | 7.1 ± 0.9 (3) | 1.3 ± 0.2 (4) | 26 ± 12 (3) | 26 |
| 6 | [dCys3]Ac-ODT-8 | 99 | 97 | 1120.45 | 1121.23 | 16 (19; 13) | 8.0 (6.4; 8.6) | 19 (7.8; 30) | 0.7 ± 0.1 (3) | 9.1 (8.9; 9.3) | 26 |
| 7 | [dCys14]Ac-ODT-8 | 99 | 99 | 1120.45 | 1121.26 | >1000 (4) | 4.9 (5.3; 4.4) | 12 (5.5; 18) | 4.5 (4.7; 4.3) | 11 (12; 10) | 26 |
| 8 | [dCys3, dCys14]Ac-ODT-8 | 99 | 99 | 1120.45 | 1121.43 | >1000 (4) | 9 (11; 7) | 15 (11; 18) | 3.25 (3.3; 3.2) | 7.4 (6.2; 8.5) | 26 |
| 9 | [Ncy3]Ac-ODT-8 | 97 | 98 | 1106.44 | 1107.20 | 79 (107; 50) | 33 (39; 26) | 6.0 (3.9; 8) | 1.9 ± 0.6 (3) | 9.0 (5.9; 12) | 25 |
| 10 | [dNcy3]Ac-ODT-8 | 99 | 97 | 1106.44 | 1107.23 | 416 ± 126 (4) | 42 ± 11 (5) | 14 ± 2.6 (4) | 3.1 ± 0.9 (5) | 46 ± 16 (4) | 25 |
| 11 | [Ncy14]Ac-ODT-8 | 99 | 98 | 1106.44 | 1107.18 | 358 (540; 175) | 41 (36; 45) | 20 (13; 26) | 2.0 ± 0.5 (3) | 50 (39; 61) | 25 |
| 12 | [dNcy14]Ac-ODT-8 | 98 | 99 | 1106.44 | 1107.18 | >1000 (4) | 5.4 (3.6; 7.1) | 53 (22; 83) | 6.0 (8.1; 3.9) | 82 (38; 126) | 25 |
| 13 | [dCys3, Ncy14]Ac-ODT-8 | 97 | 96 | 1106.44 | 1107.48 | 540 ± 171 (3) | 18.5 (18; 19) | 30 (31; 29) | 1.5 ± 0.5 (3) | 51 (84; 18) | 25 |
| 14 | [dCys3, dNcy14]Ac-ODT-8 | 99 | 99 | 1106.44 | 1107.48 | >1000 (4) | 4.8 (4.3; 5.3) | 36 (45; 27) | 3 ± 0.8 (3) | 17 (25; 9.8) | 25 |
| 15 | [Ncy3, dCys14]Ac-ODT-8 | 99 | 99 | 1106.44 | 1107.44 | >1000 (4) | 11 (9; 13) | 69 (21; 117) | 4.4 (5.1; 3.6) | 50 (15; 85) | 25 |
| 16 | [dNcy3, dCys14]Ac-ODT-8 | 97 | 97 | 1106.44 | 1107.45 | >1000 (5) | 13 ± 2.7 (5) | 28 ± 6.1 (4) | 5.0 ± 0.6 (4) | 50 ± 7.9 (3) | 25 |
| 17 | [Ncy3, dNcy14]Ac-ODT-8 | 97 | 98 | 1092.42 | 1093.39 | >1000 (4) | 3.9 (6.2; 1.3) | 50 (84; 16) | 2.6 ± 0.7 (3) | 60 (93; 26) | 24 |
| 18* | [dNcy3, Ncy14]Ac-ODT-8 | 96 | 99 | 1092.42 | 1093.58 | >1000 (2) | 109 ± 8.5 (3) | 45 (32; 58) | 2.7 ± 0.3 (3) | 107 (163; 51) | 24 |
| 19* | [Ncy3, Ncy14]Ac-ODT-8 | 99 | 99 | 1092.42 | 1093.37 | 302 (381; 222) | 34 (32; 36) | 19 (16; 22) | 1.6 ± 0.2 (3) | 57 (73; 40) | 24 |
| 20 | [dNcy3, dNcy14]Ac-ODT-8 | 94 | 99 | 1092.42 | 1093.53 | >1000 (4) | 13 ± 2.5 (3) | 31 (23; 38) | 2.2 ± 0.6 (3) | 21 (29; 12) | 24 |
| 21* | [Hcy3]-Ac-ODT-8 | 97 | 98 | 1134.47 | 1135.88 | 96 (103; 89) | 6.5 (6.1; 6.9) | 38 (59; 17) | 0.9 (0.61; 1.1) | 28 (17; 38) | 27 |
| 22 | [DHcy3]-Ac-ODT-8 | 98 | 99 | 1134.47 | 1135.64 | 218 (306; 130) | 40 (48; 32) | 69 (74; 63) | 1.4 (1.3; 1.5) | 90 (57; 122) | 27 |
3D NMR structures of these analogues are presented in this paper.
Percent purity determined by HPLC using buffer system: A = TEAP (pH 2.5) and B = 60% CH3CN/40% A with a gradient slope of 1% B/min, at flow rate of 0.2 mL/min on a Vydac C18 column (0.21 × 15 cm, 5-μm particle size, 300 Å pore size). Detection at 214 nM.
Capillary zone electrophoresis (CZE) was done using a Beckman P/ACE System 2050 controlled by an IBM Personal System/2 Model 50Z and using a ChromJet integrator. Field strength of 15 kV at 30 °C, mobile phase: 100 mM sodium phosphate (85:15, H2O:CH3CN) pH 2.50, on a Supelco P175 capillary (363 μm OD × 75 μm ID × 50 cm length). Detection at 214 nM.
The calculated m/z of the monoisotope compared with the observed [M + H]+ monoisotopic mass.
The IC50 values (nM) were derived from competitive radioligand displacement assays reflecting the affinities of the analogues for the cloned somatostatin receptors using the non-selective 125I-[Leu8,DTrp22,Tyr25]SRIF-28, as the radioligand. Mean value ± SEM when N ≥ 3 (shown in parenthesis). In the other cases, mean is shown with single values in parenthesis.