title: Fluorescence spectroscopy of small peptides interacting with microheterogeneous micelles.
abstract: Many peptides containing tryptophan have therapeutic uses and can be studied by their fluorescent properties. The biological activity of these peptides involves interactions with many cellular components and micelles can function as carriers inside organisms. We report results from the interaction of small peptides containing tryptophan with several microheterogeneous systems: sodium dodecyl sulphate (SDS) micelles; sodium dodecyl sulphate-poly(ethylene oxide) (SDS-PEO) aggregates; and neutral polymeric micelles. We observed that specific parameters, such as wavelength of maximum emission and fluorescence anisotropy, could be used to ascertain the occurrence of interactions. Affinity constants were determined from changes in the intensity of emission while structural modifications in rotameric conformations were verified from time-resolved measurements. Information about the location and diffusion of peptides in the microheterogeneous systems were obtained from tryptophan emission quenching experiments using N-alkylpyridinium ions. The results show the importance of electrostatic and hydrophobic effects, and of the ionization state of charged residues, in the presence of anionic and amphiphilic SDS in the microheterogeneous systems. Conformational stability of peptides is best preserved in the interaction with the neutral polymeric micelles.
authors.affiliation: Departamento de Física e Matemática, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Av Bandeirantes 3900, 14040-901 Ribeirão Preto, SP, Brazil.
authors.forename: Ana Paula
authors.initials: AP
authors.lastname: Romani
authors.forename: Cassia Alessandra
authors.initials: CA
authors.lastname: Marquezin
authors.forename: Amando Siuiti
authors.initials: AS
authors.lastname: Ito
mesh_terms: D004151:Dipeptides / Q000737:chemistry / Q000378:metabolism*; D005454:Fluorescence Polarization / Q000379:methods; D008823:Micelles; D011092:Polyethylene Glycols / Q000737:chemistry / Q000378:metabolism*; D012967:Sodium Dodecyl Sulfate / Q000737:chemistry / Q000378:metabolism*; D013050:Spectrometry, Fluorescence / Q000379:methods; D014364:Tryptophan / Q000737:chemistry
chemical_list: D004151:Dipeptides; D008823:Micelles; D012967:Sodium Dodecyl Sulfate; D011092:Polyethylene Glycols; D014364:Tryptophan