Table 1.
m/z (M + 1)
|
TLC Rfb |
||||||
---|---|---|---|---|---|---|---|
No. | Sequence | Calculated | Observed (ESI) | HPLC retention time (min)a | 1 | 2 | 3 |
1 | c[CO-m-C6H4-CO-His-D-Phe-Arg-Trp-Lys]-NH2 | 902.4426 | 902.4440 | 14.12 | 0.56 | 0.10 | 0.68 |
2 | c[CO-p-C6H4-CO-His-D-Phe-Arg-Trp-Lys]-NH2 | 902.4426 | 902.4518 | 15.26 | 0.53 | 0.04 | 0.61 |
3 | c[CO-2,6-pyridine-CO-His-D-Phe-Arg-Trp-Lys]-NH2 | 903.4378 | 903.4237 | 14.37 | 0.64 | 0.11 | 0.67 |
4 | c[CO-2,3-pyrazine-CO-His-D-Phe-Arg-Trp-Lys]-NH2 | 904.4331 | 904.4195 | 14.38 | 0.58 | 0.04 | 0.60 |
5 | c[CO-cis-CH=CH-CO-His-D-Phe-Arg-Trp-Lys]-NH2 | 852.4269 | 852.4312 | 12.87 | 0.63 | 0.05 | 0.66 |
6 | c[CO-(CH2)4-CO-His-D-Phe-Arg-Trp-Lys]-NH2 | 882.4739 | 882.4685 | 12.39 | 0.61 | 0.05 | 0.63 |
7 | c[CO-(CH2)5-CO-His-D-Phe-Arg-Trp-Lys]-NH2 | 896.4895 | 896.4908 | 12.46 | 0.65 | 0.06 | 0.65 |
8 | c[CO-m-C6H4-CO-His-D-Nal(2′)-Arg-Trp-Lys]-NH2 | 952.4582 | 952.4563 | 16.50 | 0.71 | 0.11 | 0.70 |
9 | c[CO-p-C6H4-CO-His-D-Nal(2′)-Arg-Trp-Lys]-NH2 | 952.4582 | 952.4618 | 16.98 | 0.62 | 0.06 | 0.69 |
10 | c[CO-2,6-pyridine-CO-His-D-Nal(2′)-Arg-Trp-Lys]-NH2 | 953.4535 | 953.4491 | 16.52 | 0.71 | 0.14 | 0.69 |
11 | c[CO-2,3-pyrazine-CO-His-D-Nal(2′)-Arg-Trp-Lys]-NH2 | 954.4487 | 954.4502 | 15.21 | 0.41 | 0.07 | 0.69 |
12 | c[CO-cis-CH=CH-CO-His-D-Nal(2′)-Arg-Trp-Lys]-NH2 | 902.4426 | 902.4474 | 14.63 | 0.66 | 0.06 | 0.69 |
13 | c[CO-(CH2)4-CO-His-D-Nal(2′)-Arg-Trp-Lys]-NH2 | 932.4895 | 932.4916 | 14.42 | 0.64 | 0.05 | 0.66 |
14 | c[CO-(CH2)5-CO-His-D-Nal(2′)-Arg-Trp-Lys]-NH2 | 946.5052 | 946.4997 | 14.23 | 0.69 | 0.11 | 0.68 |
15 | H-c[Glu-His-D-Nal(2′)-Arg-Trp-Lys]-NH2 | 933.4848 | 933.4884 | 13.33 | 0.55 | 0.03 | 0.59 |
16 | Ac-c[Glu-His-D-Nal(2′)-Arg-Trp-Lys]-NH2 | 975.4952 | 975.4921 | 15.51 | 0.63 | 0.06 | 0.67 |
α-MSH, α-melanocyte-stimulating hormone; HPLC, high-performance liquid chromatography; TLC, thin-layer chromatography; ESI, electrospray ionization.
HPLC column: Vydac 218TP104, 250 × 4.6 mm, 10 μm, 300 Å; HPLC solvent A, 0.1% trifluoroacetic acid in water; solvent B, acetonitrile; gradient: 10–90% B in A over 40 min, flow rate 1.0 mL/min.
TLC system 1: ethyl acetate/acetic acid/water/pyridine (5:1:3:5); TLC system 2: n-propanol/acetic acid/water (10:1:1); TLC system 3: n-butanol/acetic acid/water/pyridine (5:1:4:5).