FLUORESCENCE STUDY OF THE MACROLIDE PENTAENE ANTIBIOTIC FILIPIN IN AQUEOUS-SOLUTION AND IN A MODEL SYSTEM OF MEMBRANES

被引:30
作者
CASTANHO, MARB [1 ]
PRIETO, MJE [1 ]
机构
[1] CTR QUIM FIS MOLEC,COMPLEXO I-IST,AV ROVISCO PAIS,P-1096 LISBON,PORTUGAL
来源
EUROPEAN JOURNAL OF BIOCHEMISTRY | 1992年 / 207卷 / 01期
关键词
D O I
10.1111/j.1432-1033.1992.tb17029.x
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
The polyene antibiotic filipin (a pentaene) has been studied using photophysical techniques. The polyene self-aggregates in water with a critical micellar concentration of 2-mu-M. Two approaches were used to evaluate the aggregate dimensions: (a) a lower limit of 10 nm for the aggregate radius was obtained from energy transfer experiments; (b) a formula for rationalizing the turbidity spectrum was derived, and from its application a spherical shape of radius about 50 nm was deduced. The low value for the fluorescence anisotropy of the aggregate (r = 0.02) is compatible with a very loose structure, i. e. the chromophore has very efficient depolarization dynamics that is not controlled by the aggregate size. The Stern-Volmer plot of aggregated filipin fluorescence quenching by iodide is non-linear, presenting a downward curvature. A model was used for the interpretation of these data, along with a study of the quenching in transient state; it was concluded that all the components of the decay are affected by the quencher, i.e. the aggregate has a very open structure with respect to the iodide ion. The partition constants of the polyene, K(p), between a model system of membranes (small unilamellar vesicles of dipalmitoylglycerophosphocholine) and the aqueous phase were determined from anisotropy measurements; the values obtained were K(p) (gel phase) = (3.4 +/- 0.8) x 10(3) and K(p) (liquid crystal phase) = (7.7 +/- 2.2) x 10(2). The observation that the polyene incorporation is efficient is at variance with the belief that the presence of sterols are essential for the interaction of polyene antibiotics with membranes [for review see Bolard, J. (1986) Biochim. Biophys. Acta 864, 257 - 304].
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页码:125 / 134
页数:10
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