Dielectric properties of adsorption/ionization site of pentachlorophenol in lipid membranes.
Dielectric properties of adsorption/ionization site of pentachlorophenol in lipid membranes.
复制标题
脂膜中五氯苯酚吸附/电离位点的介电特性。
DOI：
10.1016/0005-2736(87)90141-6
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发表时间：
1987
期刊：
影响因子：
--
通讯作者：
Hsu,K
中科院分区：
文献类型：
--
作者：
Smejtek,P;Barstad,AW;Hsu,K
The results of three complementary studies focused on characterization of the local environment of the common pesticide pentachlorophenol (PCP) adsorbed to phosphatidylcholine (PC) and phosphatidylglycerol (PG) membranes are reported. The effect of cholesterol (Chol) was examined. These studies included: (1) Measurements of solvatochromic shifts of the ultraviolet absorption spectra of PCP in membranes and in polar non-hydrogen-bonding (a red shift) and hydrogen-bonding (a blue shift) solvents. Pi-pi∗transition energies were analyzed in terms of the dielectric cavity models of (a) Onsager, (b) Block-Walker, which includes dielectric saturation, and (c) a soft dipole model of Suppan, which accounts for PCP's polarizability. The estimates of dielectric constant of the PCP adsorption site yielded 8.1–8.7 for the PC and 16.8–20.1 for PG membranes. Solvatochromic effects indicate hydrogen bonding between the membrane-bound ionized PCP molecule and water, which is enhanced by the presence of cholesterol. (2) Determinations of the pKaof PCP adsorbed to PC, PG, PC/Chol, PG/Chol membranes and dissolved in dioxane-water solutions of a known dielectric constant. The pKavalue of PCP adsorbed to membranes was always greater than the standard pKavalue and it increased with the membrane's negative charge. The pKavalue sequence in 0.1 M Kcl was 6.68 (PG), 6.32 (PG/Chol = 70:30 mole fractions), 5.97 (PC), and 5.75 (PC/Chol = 70:30). The intrinsic pKavalues of PCP in membranes were 5.2–5.4 (PG) and 5.5–6.0 (PC). Estimates of the dielectric constant of PCP's ionization site in membranes yielded 10–22 (PC) and 27–37 (PG). Cholesterol facilitated the release of the hydrogen ion from membrane-bound PCP. (3) Measurements of pH dependence of PCP-induced membrane electrical conductivity. pH values of conductivity maxima were always greater than the standard pKaof PCP, and their sequence corresponded to that of the pKavalues of membrane-bound PCP. The anomalous properties of PCP as a Class 2 uncoupler are due to PCP's lipophilic character. In response to a low dielectric constant of the adsorption/ionization site, the physicochemical characteristics of PCP adsorbed to membranes are different from the standard values - a fact that needs to be taken into account in the development of models of PCP's toxicity.
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DOI：
--
发表时间：
1978
期刊：
Biochimica et Biophysica Acta
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DOI：
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发表时间：
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