ISSN:
0006-3525
Keywords:
melittin
;
dansylcadaverine-melittin
;
dansylcadaverine-substance P
;
peptide-lipid interaction
;
thermodynamic treatment
;
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
A thermodynamic approach is proposed to quantitatively analyze the binding isotherms of peptides to model membranes as a function of one adjustable parameter, the actual peptide charge in solution zp+. The main features of this approach are a theoretical expression for the partition coefficient calculated from the molar free energies of the peptide in the aqueous and lipid phases, an equation proposed by S. Stankowski [(1991) Biophysical Journal, Vol. 60, p. 341] to evaluate the activity coefficient of the peptide in the lipid phase, and the Debye-Hückle equation that quantifies the activity coefficient of the peptide in the aqueous phase. To assess the validity of this approach we have studied, by means of steady-state fluorescence spectroscopy, the interaction of basic amphipathic peptides such as melittin and its dansylcadaverine analogue (DNC-melittin), as well as a new fluorescent analogue of substance P, SP (DNC-SP) with neutral phospholipid membranes. A consistent quantitative analysis of each binding curve was achieved. The zp+ values obtained were always found to be lower than the physical charge of the peptide. These zp+ values can be rationalized by considering that the peptide charged groups are strongly associated with counterions in buffer solution at a given ionic strength. The partition coefficients theoretically derived using the zp+ values were in agreement with those deduced from the Gouy-Chapman formalism. Ultimately, from the zp+ values the molar free energies for the free and lipid-bound states of the peptides have been calculated. © 1997 John Wiley & Sons, Inc. Biopoly 42: 169-181, 1997
Additional Material:
6 Ill.
Type of Medium:
Electronic Resource
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