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INTERACTION OF THE PEPTIDE HORMONE ADRENOCORTICOTROPIC ACTH(l‐24), WITH A MEMBRANE MODEL SYSTEM: A FLUORESCENCE STUDY *
Author(s) -
Moreno M. J.,
Prieto M.
Publication year - 1993
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1993.tb02314.x
Subject(s) - chemistry , fluorescence , membrane , peptide , dipalmitoylphosphatidylcholine , fluorescence anisotropy , vesicle , tryptophan , aqueous solution , fluorescence spectroscopy , quenching (fluorescence) , förster resonance energy transfer , photochemistry , biophysics , phosphatidylcholine , amino acid , organic chemistry , biochemistry , phospholipid , biology , physics , quantum mechanics
The peptide hormone adrenocorticotropin and a related peptide were studied in solution and in interaction with a model system of membranes (small unilamellar vesicles of dipalmitoylphosphatidylcholine and 17% dimyristoylphosphatidylglycerol) via fluorescence spectroscopy. In aqueous solution, intramolecular distances between the fluorescent residues R(Tyr 2 ‐Trp 9 ) = 9.2 Å and R(Trp 9 ‐Tyr 23 ) 18 Å were obtained, in agreement with molecular models. Interaction of the peptide with the negatively charged membrane is evident from the alteration of the Trp photophysical parameters (quantum yield, fluorescence spectra and anisotropy), with a partition constant between the lipidic and aqueous phase of K p =1–2 times 10 3 . The existence of two populations of Trp in the membrane, which are distinctly accessed by acrylamide, was concluded from the tryptophan fluorescence quenching study; the two fractions are located near the membrane interface as inferred from its fluorescence quenching by the 5‐doxylstearate and 16‐doxylstearate lipophilic quenchers. This result is further supported by energy transfer experiments to the 3‐(9‐anthroyloxyl)stearic acid and 12‐(9‐anthroyloxyl)stearic acid probes.