Acid-base titration of melanocortin peptides: Evidence of Trp rotational conformers interconversion

Acid-base titration of melanocortin peptides: Evidence of Trp rotational conformers interconversion

Autor Fernandez, R. M. Google Scholar
Vieira, RFF Google Scholar
Nakaie, C. R. Google Scholar
Lamy, M. T. Google Scholar
Ito, A. S. Google Scholar
Instituição Universidade de São Paulo (USP)
Universidade Federal de São Paulo (UNIFESP)
Resumo Tryptophan time-resolved fluorescence was used to monitor acid-base titration properties of alpha-melanocyte stimulating hormone (alpha-MSH) and the biologically more potent analog [Nle(4), D-Phe(7)]alpha -MSH (NDP-MSH), labeled or not with the paramagnetic amino acid probe 2,2,6,6-tetramthylpiperidine-N-oxyl-4-amino-4-carboxylic acid (Toac). Global analysis of fluorescence decay profiles measured in the pH range between 2.0 and 11.0 showed that, for each peptide, the data could be well fitted to three lifetimes whose values remained constant. the less populated short lifetime component changed little with pH and was ascribed to Trp g+ chi(1) rotamer, in which electron transfer deactivation predominates over fluorescence. the long and intermediate lifetime preexponential factors interconverted along that pH interval and the result was interpreted as due to interconversion between Trp g- and trans chi(1) rotamers, driven by conformational changes promoted by modifications in the ionization state of side-chain residues. the differences in the extent of interconversion in alpha-MSH and NDP-MSH are indicative of structural differences between the peptides, while titration curves suggest structural similarities between each peptide and its Toac-labeled species, in aqueous solution. Though less sensitive than fluorescence, the Toac electron spin resonance (ESR) isotropic hyperfine splitting parameter can also monitor the titration of side-chain residues located relatively far from the probe. (C) 2005 Wiley Periodicals, Inc.
Palavra-chave pH titration
Trp
time-resolved fluorescence
melanocortins
Toac
electron spin resonance
alpha-melanocyte stimulating hormone
NDP-MSH
Idioma Inglês
Data de publicação 2005-01-01
Publicado em Biopolymers. Hoboken: John Wiley & Sons Inc, v. 80, n. 5, p. 643-650, 2005.
ISSN 0006-3525 (Sherpa/Romeo, fator de impacto)
Publicador Wiley-Blackwell
Extensão 643-650
Fonte http://dx.doi.org/10.1002/bip.20210
Direito de acesso Acesso restrito
Tipo Artigo
Web of Science WOS:000232334800004
Endereço permanente http://repositorio.unifesp.br/handle/11600/28069

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