We found a match
Your institution may have rights to this item. Sign in to continue.
- Title
Synthesis and biological properties of p-azidophenylalanine<sup>13</sup>-β-melanotropin, a potent photoaffinity label for MSH receptors.
- Authors
Eberle, Alex N.; De Graan, Pierre N. E.; Hübscher, Willy
- Abstract
p-Azidophenylalanine13-α-melantropin ([Pap13]-α-MSH) was synthesized in homogeneous solution by the fragment condensation method, and its biological activity was determined in three different assay systems. The pigment-dispersing activity relative to α-MSH was 65%, measured with melanophores of Rana pipiens or of Xenopus laevis tadpoles. The tyrosinase-stimulating activity was 50%, determined with cultured mouse melanoma cells. UV. irradiation of solutions containing ≤10−4M[Pap13]-α-MSH at 338 nm (intensity: 10−3 W · cm−2) led to complete photolysis of the photolabel within <20 min. Under these conditions [Pap13]-α-MSH was covalently inserted into MSH-receptors which produced a longlasting pigment dispersion in Xenopus melanphores (see [3]). The extent of this prolonged stimulation depended on the hormone concentration used during photolysis. 1.8·10−9M [Pap13]-α-MSH which produced a full initial response failed to prolong the effect, whereas 1.2·10−8M hormone caused irreversible stimulation. It appears that only about 10% of the initially occupied receptors were covalently labelled because the log dose response curve was shifted to ∼ 10x higher concentration after a 200 min wash period: EC50 immediately after photolysis was 6 · 10−10M; after 200 min EC50 increased to ∼8·10−9M.
- Publication
Helvetica Chimica Acta, 1981, Vol 64, Issue 8, p2645
- ISSN
0018-019X
- Publication type
Article
- DOI
10.1002/hlca.19810640823