RESUMO
Two analogues of the 29 amino acid sequence of human growth hormone-releasing hormone, namely [Nle27]hGH-RH(1-29)-NH2 and [Orn(12,21),Nle27]hGH-RH(1-29)-NH2, have been synthesized and subjected to digestion by trypsin. The course of degradation was followed using RP-HPLC and ESI-MS. Several intermediates and final products of degradation were identified and conclusions regarding the rate of cleavages at different positions occupied by Lys and Arg residues were drawn. The analogue containing ornithine was found to be less susceptible to hydrolysis by trypsin: the 12-13 and 21-22 peptide bonds were completely resistant to the cleavage. The results show that by replacing Lys with Orn, a possibility exists to design new peptides, which could be more stable in biological fluids.
Assuntos
Hormônio Liberador de Hormônio do Crescimento/metabolismo , Lisina/química , Ornitina/química , Fragmentos de Peptídeos/metabolismo , Tripsina/metabolismo , Sequência de Aminoácidos , Arginina/química , Cromatografia Líquida de Alta Pressão , Hormônio Liberador de Hormônio do Crescimento/química , Humanos , Hidrólise , Dados de Sequência Molecular , Biossíntese Peptídica , Fragmentos de Peptídeos/química , Peptídeos/química , Espectrometria de Massas por Ionização por Electrospray , Fatores de TempoRESUMO
Proton NMR and FTIR measurements have shown that the formation of stable, interbase hydrogen-bonded species of 5'-GMP in aqueous solutions of the tetramethylammonium salt can occur without the subsequent formation of ordered, slowly-exchanging structures or base stacking. Analysis of the NMR data is in agreement with an equilibrium mixture of monomers, dimers and cyclic tetramers. The association constants and amino proton chemical shifts are reported for these species. This is the first report that the cyclic tetramer structure exists as a discrete species in 5'-GMP solutions.
