Department of Physics, University of Nevada, Reno, NV 89557, USA.
Biopolymers. 2010 May;93(5):403-17. doi: 10.1002/bip.21382.
Vibrational spectroscopic techniques such as near-infrared (NIR), Fourier transform infrared (FTIR), and Raman spectroscopy are valuable diagnostic tools that can be used to elucidate comprehensive structural information of numerous biological samples. In this review article, we have highlighted the advantages of nanotechnology and biophotonics in conjunction with vibrational spectroscopic techniques in order to understand the various aspects of new kind of synthetic biopolymers termed as polyethylene glycol (PEG)ylated lipids. In contrast to conventional phospholipids, these novel lipids spontaneously form liposomes or nanovesicles upon hydration, without the supply of external activation energy. The amphiphiles considered in this study differ in their hydrophobic acyl chain length and contain different units of PEG hydrophilic headgroups. We have further explored the thermotropic phase behaviors and associated changes in the conformational order/disorder of such lipids by using variable-temperature FTIR and Raman spectroscopy. Phase transition temperature profiles and correlation between various spectral indicators have been identified by either monitoring the shifts in the vibrational peak positions or plotting vibrational peak intensity ratios in the C--H stretching region as a function of temperature. To supplement our observations of phase transformations, a thermodynamic approach known as differential scanning calorimetry (DSC) has been applied and revealed a good agreement with the infrared and Raman spectroscopic data. Finally, the investigation of thermal properties of lipids is extremely crucial for numerous purposes, thus the results obtained in this work may find application in a wide variety of studies including the development of PEGylated lipid based drug and substances delivery vehicles.
振动光谱技术，如近红外（NIR）、傅里叶变换红外（FTIR）和拉曼光谱，是有价值的诊断工具，可用于阐明众多生物样本的综合结构信息。在这篇综述文章中，我们强调了纳米技术和生物光子学与振动光谱技术相结合的优势，以了解新型合成生物聚合物——聚乙二醇（PEG）化脂质的各个方面。与传统的磷脂不同，这些新型脂质在水合时会自发形成脂质体或纳米囊泡，而不需要外部激活能的供应。本研究中考虑的两亲物在其疏水酰基链长度上有所不同，并含有不同单元的 PEG 亲水头部基团。我们进一步通过使用变温 FTIR 和拉曼光谱研究了这种脂质的热致相行为和构象有序/无序的相关变化。通过监测振动峰位置的移动或绘制 C-H 伸缩区域振动峰强度比随温度的变化，确定了相变温度曲线和各种光谱指标之间的相关性。为了补充我们对相变的观察，应用了一种称为差示扫描量热法（DSC）的热力学方法，并且与红外和拉曼光谱数据吻合良好。最后，脂质热性质的研究对于许多目的都非常重要，因此，这项工作的结果可能会在广泛的研究中得到应用，包括基于 PEG 化脂质的药物和物质传递载体的开发。
