AUTOXIDATION OF MODEL MEMBRANES - THE KINETICS AND MECHANISM OF AUTOXIDATION OF MIXED PHOSPHOLIPID-BILAYERS
AUTOXIDATION OF MODEL MEMBRANES - THE KINETICS AND MECHANISM OF AUTOXIDATION OF MIXED PHOSPHOLIPID-BILAYERS
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DOI：
10.1139/v87-423
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发表时间：
1987-11-01
影响因子：
1.1
通讯作者：
LOCKE, SJ
中科院分区：
文献类型：
--
作者：
BARCLAY, LRC;BASKIN, KA;LOCKE, SJ
可氧化的二亚油酰磷脂酰胆碱（DLPC）与饱和磷脂（二肉豆蔻酰，DMPC，和二棕榈酰磷脂酰胆碱，DPPC）的双层混合物的自氧化动力学遵循经典的自氧化速率定律：-d[O 2]/dt =kp/2kt 1/2[RH] Ri 1/2。底物[RH]中的动力学顺序被认为是统一的脂质溶性引发剂，偶氮二-2，4-二甲基戊腈（ADVN），并通过水溶性偶氮二（2-脒基丙烷··HCl）（ABAP）引发的过氧化反应。链引发速率的动力学顺序，Ri，被认为是一半的ADVN，光化学分解，和ABAP的引发。单层DLPC脂质体的氧化能力（kp/2kt 1/2 = 0.232 M-1/2 s-1/2）是多层DLPC脂质体氧化能力（kp/2kt 1/2 = 0.116 M-1/2 s-1/2）的2倍。对ABAP引发的混合DLPC + DPPC脂质体自氧化过程中形成的氢过氧化物的分析显示，顺式、反式与反式、反式几何异构体氢过氧化物的比例与[DLPC]之间呈线性趋势，与均相系统提出的过氧化机制一致。混合双层膜的~（31）P NMR谱用于区分DLPC + DPPC的非均相和均相混合物。在氧化的各个阶段所采取的这种光谱表明，DLPC的双层结构被保存至少到动力学研究中使用的氧化的10%的程度。在高得多的氧化转化率，光谱表明层状结构的变化。
Kinetics of autoxidation of bilayer mixtures of oxidizable dilinoleoylphosphatidylcholine (DLPC) with saturated phospholipids as solvents (dimyristoyl-, DMPC, and dipalmitoyl-phosphatidylcholine, DPPC) follow the classical rate law of autoxidation: -d[O2]/dt =kp/2kt1/2[RH]Ri1/2. The kinetic order in substrate [RH] was found to be unity for peroxidation initiated by a lipid-soluble initiator, azobis-2,4-dimethylvaleronitrile (ADVN), and by the water-soluble azobis(2-amidinopropane.cntdot.HCl) (ABAP). The kinetic order in rate of chain initiation, Ri, was found to be one-half for both initiation by ADVN, photochemically decomposed, and by ABAP. The oxidizability of unilamellar DLPC liposomes (kp/2kt1/2 = 0.232 M-1/2 s-1/2) is twice that of multilamellar DLPC (kp/2kt1/2 = 0.116 M-1/2 s-1/2). Analysis of the hydroperoxides formed during ABAP-initiated autoxidations of mixed DLPC + DPPC liposomes showed a linear trend between the ratio of cis, trans to trans, trans geometrical isomeric hydroperoxides and [DLPC], consistent with the peroxidation mechanism proposed for homogeneous systems. 31P nmr spectra of mixed bilayers were used to distinguish between heterogeneous and homogeneous mixtures of DLPC + DPPC. Such spectra taken at various stages of oxidation indicate that the bilayer structure of DLPC is preserved at least to the 10% extent of oxidation used in kinetic studies. At much higher oxidative conversion, the spectra indicate changes in lamellar structures.