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. Author manuscript; available in PMC: 2012 Jul 20.
Published in final edited form as: Bioconjug Chem. 2011 Jun 16;22(7):1270–1278. doi: 10.1021/bc1004284

Table 1.

Binding Data of Heterobivalent Ligands Tested for Cross-Linking in HEK293/hMC4R/tCCK-2R (hMC4R > CCK-2R)a

no. linker linker length (atoms) estimated linker length (Å) IC50 (nM) of CCK(6)b
fold increase IC50 (nM) of MSH(7)b
fold increase
CCK-2Rc dual expressione hMC4Rd dual expressione
5a -[PG]3- 18 ≤13 11 (8.3–15) 1.4 (1.0–2.0) 8 11 (8.9–12) 1300 (880–1900) 0
5b -[PG]6- 36 ≤25 46 (40–52) 2.3 (1.8–2.9) 20 110 (85–140) 1000 (690–1500) 0.1
5c -[PG]9- 54 ≤35 320 (240–420) 170 (130–240) 2 460 (250–850) 530 (180–1500) 0.9
5d -[PG]12- 72 ≤45 50 (43–58) 6.9 (5.6–8.6) 7 28 (23–33) 980 (250–3900) 0
5e -[PG]15 90 ≤55 230 (190–290) 55 (43–70) 4 680 (310–1500) 3500 (1300–9500) 0.2
8a -PEGO- 20 ≤18 11 (9.0–13) 0.50 (0.31–0.82) 22 28 (22–34) 250 (210–300) 0.1
8b -PEGO-PEGO- 40 ≤36 50 (41–62) 4.5 (3.4–5.8) 11 60 (49–75) 320 (260–400) 0.2
12a -PEGO-[PG]3-PEGO- 58 ≤46 150 (120–180) 6.3 (5.0–7.9) 24 390 (89–1700) 1600 (560–4700) 0.2
12b -PEGO-[PG]6-PEGO- 76 ≤56 72 (56–94) 20 (15–26) 4 230 (160–340) 21 (17–27) 11
12c -PEGO-[PG]12-PEGO- 112 ≤76 130 (110–150) 38 (29–50) 3 10 (6.7–16) 32 (25–39) 0.3
12d -PEGO-[PG]18-PEGO- 148 ≤96 160 (130–200) 93 (78–110) 2 35 (26–47) 28 (21–40) 1.3
a

The IC50 values of Ac-MSH(7)-NH2 and Ac-CCK(6)-NH2 are 39 ± 4 nM and 26 ± 4 nM, respectively. “Fold Increase” is the ratio of IC50 values between single- and dual-expressing cell lines.

b

IC50 concentration in nM from at least 4 independent experiments reported. Values in parentheses represent the 95% confidence intervals of the IC50 values.

c

Binding data from competition with Eu-DTPA-CCK-8 (unsulfated) against CCK-2R expressing cells.

d

Binding data from competition with Eu-DTPA-NDP-α-MSH against hMC4R expressing cells.

e

Binding data from competition with either Eu-DTPA-CCK-8 (unsulfated) or Eu-DTPA-NDP-α-MSH against cells expressing both CCK-2R and hMC4R.