title: The behavior of oxonol dyes in phospholipid dispersions.
abstract: The interaction of a class of oxonol dyes with sonicated phospholipid vesicles was followed optically. The spectra of vesicle-associated dyes resemble those found for the dyes in organic solvents, indicating that the oxonols occupy a hydrophobic region of the membrane. At equilibrium the affinity of the oxonols for the vesicles depends on the structure of the dye, the physical and chemical composition of the vesicles, and the ionic strength of the medium. The oxonols occupy soybean lipid vesicles to a level of 147.9 +/- 17.1 nmol/mg lipid with a dye membrane dissociation constant of 3.33 +/- 0.54 muM. The interaction of the oxonols with soybean lipid vesicles is biphasic. The fast phase has a second order rate constant of 9.04 +/- 0.36 x 10(6)M(-1) s(-1) and the number of "fast" binding sites, 68 +/- 8 nmol/mg lipid, was determined from the ratio of the second order rate constants obtained with lipid and with dye in excess. The dissociation of oxonols from soybean lipid vesicles is also biphasic, and the fast process has a rate constant of 17 +/- 2 s(-1), yielding a dissociation constant for the fast sites (k(-1)/k(2)) of 1.88 +/- 0.15 muM. The slow phases of oxonol association with, and release from, soybean lipid vesicles are not second order and have half times of between 0.2 and 5 min, depending on the physical and chemical composition of the membrane lipids. The amplitudes of the slow phases are sensitive to the composition of the aqueous media on each side of the vesicle membranes, which suggests that the slow processes represent the permeation of the membrane by the oxonols. The importance of the properties of the oxonol dyes in the interpretation of their behavior in natural membranes is discussed.
mesh_terms: D000475:Alkenes / Q000378:metabolism*; D002784:Cholesterol / Q000378:metabolism; D005456:Fluorescent Dyes / Q000378:metabolism*; D007555:Isoxazoles / Q000378:metabolism*; D007700:Kinetics; D008051:Lipid Bilayers / Q000378:metabolism*; D010080:Oxazoles / Q000378:metabolism*; D010743:Phospholipids / Q000378:metabolism*; D011663:Pulmonary Surfactants / Q000378:metabolism; D013010:Sonication; D013053:Spectrophotometry
chemical_list: D000475:Alkenes; D005456:Fluorescent Dyes; D007555:Isoxazoles; D008051:Lipid Bilayers; D010080:Oxazoles; D010743:Phospholipids; D011663:Pulmonary Surfactants; C018622:oxonol dyes (isoxazole); D002784:Cholesterol
references.citation: Biochem J. 1961 Aug;80:324-32
references.pmid: 13785321
references.citation: Biochemistry. 1976 Nov 16;15(23):5094-105
references.pmid: 990268
references.citation: J Membr Biol. 1976 Jun 30;27(4):317-34
references.pmid: 787526
references.citation: J Biol Chem. 1977 Dec 10;252(23):8459-63
references.pmid: 21873
references.citation: Biophys Struct Mech. 1977 Sep 28;3(3-4):275-89
references.pmid: 901914
references.citation: J Membr Biol. 1977 May 6;33(1-2):63-108
references.pmid: 864687
references.citation: J Membr Biol. 1977 May 6;33(1-2):141-83
references.pmid: 864685
references.citation: J Membr Biol. 1977 May 6;33(1-2):109-40
references.pmid: 864684
references.citation: Biochem J. 1977 Feb 1;161(2):293-302
references.pmid: 849264
references.citation: J Membr Biol. 1974;19(1):1-36
references.pmid: 4431037
references.citation: Biochim Biophys Acta. 1974 Mar 15;339(2):157-63
references.pmid: 4857150
references.citation: Biochim Biophys Acta. 1975 Jan 28;375(2):186-208
references.pmid: 235977
references.citation: Q Rev Biophys. 1975 May;8(2):185-235
references.pmid: 1103214
references.citation: Biochemistry. 1974 Jul 30;13(16):3315-30
references.pmid: 4842277
references.citation: Biochem J. 1974 Jun;139(3):721-30
references.pmid: 4854389
references.citation: J Biol Chem. 1972 Oct 10;247(19):6071-5
references.pmid: 4651644
references.citation: Biochemistry. 1976 May 4;15(9):1941-8
references.pmid: 946770
references.citation: Eur J Biochem. 1971 Jan;18(2):258-73
references.pmid: 5541509
references.citation: Biochem J. 1970 Feb;116(4):721-31
references.pmid: 5435498
references.citation: Biochemistry. 1969 Jan;8(1):344-52
references.pmid: 5777332
references.citation: J Biol Chem. 1968 May 10;243(9):2337-48
references.pmid: 5648435