School of Physics and Astronomy, University of Leeds, Leeds, UK.
Faraday Discuss. 2013;161:91-111; discussion 113-50. doi: 10.1039/c2fd20119d.
In this paper, we demonstrate that it is possible to observe many aspects of critical phenomena in supported lipid bilayers using atomic force microscopy (AFM) with the aid of stable and precise temperature control. The regions of criticality were determined by accurately measuring and calculating phase diagrams for the 2 phase L(d)-L(o) region, and tracking how it moves with temperature, then increasing the sampling density around the estimated critical regions. Compositional fluctuations were observed above the critical temperature (T(c)) and characterised using a spatial correlation function. From this analysis, the phase transition was found to be most closely described by the 2D Ising model, showing it is a critical transition. Below T(c) roughening of the domain boundaries occurred due to the reduction in line tension close to the critical point. Smaller scale density fluctuations were also detected just below T(c). At T(c), we believe we have observed fluctuations on length scales greater than 10 microm. The region of critically fluctuating 10-100 nm nanodomains has been found to extend a considerable distance above T(c) to temperatures within the biological range, and seem to be an ideal candidate for the actual structure of lipid rafts in cell membranes. Although evidence for this idea has recently emerged, this is the first direct evidence for nanoscale domains in the critical region.
在本文中，我们通过原子力显微镜（AFM）和稳定、精确的温度控制证明，在支撑的脂质双层中观察到许多临界现象是可能的。通过准确测量和计算两相 L(d)-L(o)区域的相图，并跟踪其随温度的移动，然后增加估计的临界区域周围的采样密度，确定了临界区域。在临界温度（T(c)）以上观察到了组成波动，并使用空间相关函数进行了特征描述。通过该分析发现，相变最接近二维伊辛模型，表明它是一个临界相变。在 T(c)以下，由于接近临界点时线张力的减小，畴边界发生了粗化。在 T(c)以下，还检测到较小尺度的密度波动。在 T(c)时，我们相信我们已经观察到了大于 10 微米的长度尺度上的波动。临界波动的 10-100nm 纳米域区域已经在 T(c)以上的相当大的温度范围内被发现，并且似乎是细胞膜中脂质筏实际结构的理想候选者。尽管最近出现了支持这一观点的证据，但这是临界区域中纳米域的第一个直接证据。
