Detecting Phase Transitions in Phosphatidylcholine Vesicles by Raman Microscopy and Self-Modeling Curve Resolution

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• 作者：Christopher B. Fox ; Rory H. Uibel ; Joel M. Harris
• 刊名：Journal of Physical Chemistry B
• 出版年：2007
• 出版时间：October 4, 2007
• 年：2007
• 卷：111
• 期：39
• 页码：11428 - 11436
• 全文大小：279K
• 年卷期：v.111,no.39(October 4, 2007)
• ISSN：1520-5207

文摘

The study of phospholipid phase transitions is important for understanding drug- and protein-membraneinteractions as well as other phenomena such as trans-membrane diffusion and vesicle fusion. A temperature-controlled stage on a confocal Raman microscope has allowed phase transitions in optically trapped phospholipidvesicles to be monitored. Raman spectra were acquired and analyzed using self-modeling curve resolution,a multivariate statistical analysis technique. This method revealed the subtle spectral changes indicative ofsub- and pretransitions and main transitions in vesicles composed of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC). The Raman scattering results were compared to differential scanning calorimetry(DSC) experiments and found to be in good agreement. This method of observing lipid phase transitionprofiles requires little sample preparation and a minimal amount of lipid (0.1 nmol) for an experiment. Theconformational changes of the phospholipid molecules occurring during phase transitions are elucidated fromthe Raman spectroscopy results. The evolution of chain decoupling, rotational disorder, and gauche defectsin the lipid acyl chains as a function of temperature is described.