Braun G, Lelkes P I, Nir S
Biochim Biophys Acta. 1985 Feb 14;812(3):688-94. doi: 10.1016/0005-2736(85)90262-7.
Small unilamellar vesicles composed of phosphatidylserine (PS) and cholesterol at various ratios were employed in studying the effect of cholesterol on Ca2+-induced vesicle aggregation and fusion using the Tb/dipicolinic acid assay. The leakage of preencapsulated Tb3+ was also measured. The analysis of the data provided estimates for the rate of aggregation C11, and the rate of fusion per se, f11. An increase in cholesterol contents results in a decrease in C11 values. Similarly, aggregation of PS/cholesterol vesicles is slower than that of PS vesicles in the presence of 650 mM NaCl. With 100 or 200 mM NaCl, the overall fusion rate of PS/cholesterol vesicles is slower than that of PS vesicles; the rate being reduced by an increase in cholesterol contents. With 600 mM NaCl, the overall fusion rate of PS/cholesterol 9:1 vesicles is faster than that of PS vesicles, and results are well-simulated by assuming no delay in vesicle aggregation up to dimers. Emerging f11 values are larger in PS/cholesterol than in PS vesicles. An analysis of fusion kinetics of several lipid concentrations shows that f11 values of PS/cholesterol 3:1 vesicles are 5-times larger than those of PS vesicles, when fusion occurs in a medium containing 200 mM NaCl and 1.5 mM Ca2+. The increase in Na+ concentration from 100 to 200 mM, or 600 mM results in a 50- or 150-fold reduction in f11 values of PS vesicles. It is suggested that incorporation of cholesterol in PS vesicles results in enhancement of Ca2+-induced fusogenic capacity.
使用由不同比例的磷脂酰丝氨酸（PS）和胆固醇组成的小单层囊泡，通过Tb/二吡啶甲酸测定法研究胆固醇对Ca2+诱导的囊泡聚集和融合的影响。还测量了预先包封的Tb3+的泄漏情况。数据分析提供了聚集速率C11和融合本身的速率f11的估计值。胆固醇含量的增加导致C11值降低。同样，在650 mM NaCl存在下，PS/胆固醇囊泡的聚集比PS囊泡慢。在100或200 mM NaCl时，PS/胆固醇囊泡的总体融合速率比PS囊泡慢；该速率因胆固醇含量的增加而降低。在600 mM NaCl时，PS/胆固醇9:1囊泡的总体融合速率比PS囊泡快，并且通过假设直到二聚体的囊泡聚集没有延迟可以很好地模拟结果。PS/胆固醇中的f11值比PS囊泡中的大。对几种脂质浓度的融合动力学分析表明，当在含有200 mM NaCl和1.5 mM Ca2+的介质中发生融合时，PS/胆固醇3:1囊泡的f11值比PS囊泡大5倍。Na+浓度从100 mM增加到200 mM或600 mM会导致PS囊泡的f11值降低50倍或150倍。有人认为，在PS囊泡中掺入胆固醇会增强Ca2+诱导的融合能力。
