PHOTOINDUCED DIFFUSION OF METHYL VIOLOGEN ACROSS ANIONIC SURFACTANT VESICLE BILAYERS
PHOTOINDUCED DIFFUSION OF METHYL VIOLOGEN ACROSS ANIONIC SURFACTANT VESICLE BILAYERS
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DOI：
10.1021/ja00341a013
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发表时间：
1983-01-01
影响因子：
15
通讯作者：
FENDLER, JH
中科院分区：
文献类型：
--
作者：
LEE, LYC;HURST, JK;FENDLER, JH
不对称组织的双十六烷基磷酸（DHP）囊泡含有无机光敏剂绑定到外表面和甲基紫精双阳离子，电子受体，绑定到内表面上的强酸阳离子交换树脂或葡聚糖凝胶上的色谱法制备。后一种方法被证明是上级的，因为可以避免操作过程中出现的不稳定介质条件。囊泡的完整性，证实了光子相关光谱，光谱和超滤测量。在外部电子供体的存在下，用可见光连续照射引起形成还原紫精自由基;还原的速率和程度通过在水性介质中存在羟胺缓冲液而显著增强。通过添加DHP膜不可渗透的还原剂连二亚硫酸钠，照射后的囊泡悬浮液的检查显示，MV 2+从囊泡内表面到囊泡外表面发生了广泛的扩散。低于30 ℃时，MV 2+跨双层的被动扩散不会以明显的速率发生，但高于30 ℃时，在胺缓冲液的存在下，跨膜扩散很快。紫精还原的机制似乎涉及受体的光诱导跨膜扩散，随后与结合在同一囊泡表面的光敏剂反应。
Asymmetrically organized dihexadecylphosphate (DHP) vesicles containing inorganic photosensitizers bound to the outer surface and methyl viologen dication, an electron acceptor, bound to the inner surface were prepared by chromatography on strong-acid cation-exchange resins or dextran gels. The latter method proved superior because destabilizing medium conditions arising during manipulative procedures could be avoided. Vesicle integrity was confirmed by photon correlation spectroscopy, optical spectroscopy, and ultrafiltration measurements. Continuous illumination with visible light in the presence of external electron donors gave rise to formation of reduced viologen radical; the rate and extent of reduction were markedly enhanced by the presence of hydroxylic amine buffers in the aqueous medium. Examinationof vesicle suspensions after illumination by additionof the DHP membrane-impermeable reductant, sodium dithionite, revealed that extensive diffusion of MV2+ from the inner to outer vesicle surface had occurred. Below 30 C passive diffusion of MV2+ across the bilayer does not occur at an appreciable rate, but above30 C in the presence of the amine buffers, transmembrane diffusion is rapid. The mechanism for viologen reduction appears to involve photoinduced transmembrane diffusion of acceptor followedby reaction with photosensitizer bound to the same vesicle surface.