GUVs Melt Like LUVs: The Large Heat Capacity of MLVs Is Not Due to Large Size or Small Curvature
GUVs Melt Like LUVs: The Large Heat Capacity of MLVs Is Not Due to Large Size or Small Curvature
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DOI：
10.1016/j.bpj.2015.04.034
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发表时间：
2015-06-02
影响因子：
3.4
通讯作者：
Almeida, Paulo F.
中科院分区：
文献类型：
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作者：
Kreutzberger, Mark A.;Tejada, Emmanuel;Almeida, Paulo F.
与大单层囊泡（LUV）和多层囊泡（MLV）的主要相变相关的过量热容函数（Δ C-p）非常不同。可能有两种解释。首先，囊泡大小（曲率）的差异导致膜中不同的凝胶-流体相互作用;这些相互作用对相变的协同性有很大的影响。第二，当它们经历凝胶-流体转变时，在MLV中的双层之间存在通信;这种通信导致MLV中的双层的相变的热力学耦合，因此，在转变的协同性中明显增加。为了验证这些假设，进行差示扫描量热法对纯二棕榈酰磷脂酰胆碱的巨大单层囊泡（GUV）。GUV的Delta C-p曲线被发现类似于小得多的LUV。GUV和LUV中的转变比MLV中的转变宽得多（半宽度类似于1.5摄氏度）（类似于0.1摄氏度）。GUV和LUV的这种相似性表明它们的大小对相变中的凝胶-流体相互作用几乎没有影响。结果表明，在MLV的双层跃迁之间的耦合是负责在熔化的明显较高的协同性。
The excess heat capacity functions (Delta C-p) associated with the main phase transition of large unilamellar vesicles (LUVs) and multilamellar vesicles (MLVs) are very different. Two explanations are possible. First, the difference in vesicle size (curvature) results in different gel-fluid interactions in the membrane; those interactions have a large effect on the cooperativity of the phase transition. Second, there is communication between the bilayers in an MLV when they undergo the gel-fluid transition; this communication results in thermodynamic coupling of the phase transitions of the bilayers in the MLV and, consequently, in an apparent increase in the cooperativity of the transition. To test these hypotheses, differential scanning calorimetry was performed on giant unilamellar vesicles (GUVs) of pure dipalmitoylphosphatidylcholine. The Delta C-p curve of GUVs was found to resemble that of the much smaller LUVs. The transition in GUVs and LUVs is much broader (half-width similar to 1.5 degrees C) than in MLVs (similar to 0.1 degrees C). This similarity in GUVs and LUVs indicates that their size has little effect on gel-fluid interactions in the phase transition. The result suggests that coupling between the transitions in the bilayers of an MLV is responsible for their apparent higher cooperativity in melting.