Dean R T, Hunt J V, Grant A J, Yamamoto Y, Niki E
Heart Research Institute, Camperdown, Sydney, N.S.W., Australia.
Free Radic Biol Med. 1991;11(2):161-8. doi: 10.1016/0891-5849(91)90167-2.
Free radicals were generated at known rates in the aqueous phase (by means of 2,2'-azobis (2-amidinopropane) dihydrochloride [AAPH]) and in a membranous (lipid) phase (by means of 2,2'-azobis (2,4-dimethylvaleronitrile [AMVN]). A soluble protein (bovine serum albumin: BSA), and membranes of lysed mitochondria containing radioactively labeled monoamine oxidase (MAO), were exposed to the resultant radical fluxes. Antioxidants were added to the system, either in the aqueous phase (Trolox) or in a liposomal membrane phase (alpha-tocopherol). Protein damage was assessed as tryptophan oxidation and conformational changes in tryptophan fluorescence of the soluble protein, BSA, and as fragmentation of both BSA and monoamine oxidase. Radicals generated in the aqueous phase, by AAPH, were effective in damaging BSA and MAO. Radicals generated within the liposome membrane phase (by AMVN) were less effective against BSA than those deriving from AAPH. Liposomal AMVN radicals could damage MAO, present in a separate membranous phase, though again, less effectively than could AAPH-derived radicals. BSA could be protected by Trolox, the aqueous soluble antioxidant, but hardly by tocopherol itself. Damage to MAO was limited by Trolox, and also by the hydrophobic antioxidant, tocopherol. Damaging reactions due to radicals generated in a membrane phase were significantly accelerated when the membrane was peroxidizable (soybean phosphatidylcholine) rather than nonperoxidizable (saturated dimyristoyl phosphatidylcholine). Thus lipid radicals also played some role in protein damage in these systems. BSA was attacked similarly in the presence or absence of liposomes by AAPH. Correspondingly, BSA could inhibit the peroxidation of liposomes induced by AAPH and less efficiently that induced by AMVN.(ABSTRACT TRUNCATED AT 250 WORDS)
自由基在水相中以已知速率产生（通过2,2'-偶氮二（2-脒基丙烷）二盐酸盐[AAPH]），并在膜（脂质）相中产生（通过2,2'-偶氮二（2,4-二甲基戊腈）[AMVN]）。将一种可溶性蛋白质（牛血清白蛋白：BSA）以及含有放射性标记单胺氧化酶（MAO）的裂解线粒体膜暴露于产生的自由基通量中。抗氧化剂被添加到系统中，要么在水相中（生育三烯酚），要么在脂质体膜相中（α-生育酚）。蛋白质损伤通过色氨酸氧化以及可溶性蛋白质BSA色氨酸荧光的构象变化来评估，同时也通过BSA和单胺氧化酶的片段化来评估。由AAPH在水相中产生的自由基对BSA和MAO具有损伤作用。在脂质体膜相中（由AMVN产生）产生的自由基对BSA的损伤作用比对源自AAPH的自由基的损伤作用小。脂质体AMVN自由基可以损伤存在于单独膜相中的MAO，不过同样比源自AAPH的自由基损伤作用小。BSA可以受到水溶性抗氧化剂生育三烯酚的保护，但几乎不受生育酚本身的保护。MAO的损伤受到生育三烯酚以及疏水性抗氧化剂生育酚的限制。当膜可过氧化（大豆磷脂酰胆碱）而非不可过氧化（饱和二肉豆蔻酰磷脂酰胆碱）时，膜相中产生的自由基引起的损伤反应会显著加速。因此，脂质自由基在这些系统中的蛋白质损伤中也起到了一定作用。在有或没有脂质体存在的情况下，AAPH对BSA的攻击方式相似。相应地，BSA可以抑制由AAPH诱导的脂质体过氧化，对由AMVN诱导的脂质体过氧化的抑制作用则较弱。（摘要截选至250词）
