Chakrabarti A C, Veiro J A, Wong N S, Wheeler J J, Cullis P R
Department of Biochemistry, University of British Columbia, Vancouver, Canada.
Biochim Biophys Acta. 1992 Jul 27;1108(2):233-9. doi: 10.1016/0005-2736(92)90030-p.
Previous work (Veiro and Cullis (1990) Biochim. Biophys. Acta 1025, 109-115) has shown that Ca2+ can be accumulated into large unilamellar vesicles (LUVs) in the presence of a transmembrane pH gradient (inside acidic) and the Ca(2+)-ionophore A23187. Here, the ability of A23187 to mediate the uptake of iron and barium into LUVs has been investigated. It is shown that under appropriate conditions of temperature and A23187 concentration, iron (in the form of Fe2+) can be accumulated into EPC and DSPC/cholesterol (55:45; mol/mol) LUVs with an acidic interior. This uptake is dependent on the internal buffer concentration, with maximum levels of uptake in the range of 300 nmol of cation per mumol lipid. The DSPC-cholesterol LUV systems exhibit superior retention properties compared to the EPC systems. It is demonstrated that Ba2+ can also be loaded by similar methods. It is also shown that the maximally loaded Fe(2+)- and Ba(2+)-containing LUVs exhibit increased densities. This is expressed by enhanced gravimetric properties, as an increased proportion of the loaded LUVs can be pelleted by low speed centrifugation, and by enhanced electron densities, in that the Ba(2+)-loaded systems can be directly visualized employing cryo-electron microscopy.
先前的研究工作（Veiro和Cullis（1990年），《生物化学与生物物理学学报》1025卷，109 - 115页）表明，在存在跨膜pH梯度（内部呈酸性）和Ca(2 +)-离子载体A23187的情况下，Ca2 +可被积累到大型单层囊泡（LUVs）中。在此，研究了A23187介导铁和钡进入LUVs的能力。结果表明，在适当的温度和A23187浓度条件下，铁（以Fe2 +形式）可被积累到内部呈酸性的EPC和DSPC/胆固醇（55:45；摩尔/摩尔）LUVs中。这种摄取依赖于内部缓冲液浓度，摄取的最大水平在每微摩尔脂质300纳摩尔阳离子的范围内。与EPC系统相比，DSPC - 胆固醇LUV系统表现出更好的保留特性。已证明Ba2 +也可通过类似方法加载。还表明，最大负载量的含Fe(2 +)-和Ba(2 +)-的LUVs表现出密度增加。这通过增强的重量特性来体现，即更多比例的负载LUVs可通过低速离心沉淀，并且通过增强的电子密度来体现，因为加载Ba(2 +)的系统可通过冷冻电子显微镜直接观察到。
