Department of Physical Chemistry - Interfacial Phenomena, Faculty of Chemistry, Maria Curie-Sklodowska University, Lublin, Poland.
Chem Phys Lipids. 2012 Apr;165(3):302-10. doi: 10.1016/j.chemphyslip.2012.02.003. Epub 2012 Feb 27.
The Langmuir-Blodgett (LB) method was applied and a few series of advancing and receding contact angles measurements as a function of time were performed to examine stability of model phospholipid monolayers during their contact with water, formamide and diiodomethane droplets. The studied monolayer was single-component saturated phospholipid 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) transferred onto mica surface. When the time of the contact angle measurements is prolonged in these systems, some changes in the DPPC layer structure occur due to the contact with probing liquid, especially water, which is reflected in the changes of measured contact angle. Generally, with increasing time of the droplet contact with DPPC monolayer the contact angle decreases. Some correlation between the contact angle decrease and molecular rearrangements of initially hydrophobic DPPC monolayer is observed if it comes into contact with water. On the other hand, the contact angle completed within the first few seconds can faithfully reflect the original structure of the layer, and thus its energetic state, because during this time the structure changes are insignificant. Basing on the measured contact angles the monolayer's apparent surface free energy and its components, corresponding to different contact times of the droplets, were calculated. These results are helpful for better characterization of the processes taking place in the phospholipid layers being in contact with polar (water and formamide) and nonpolar (diiodomethane) liquids.
采用 Langmuir-Blodgett（LB）方法，进行了一系列前进和后退接触角测量作为时间的函数，以检查模型磷脂单层在与水、甲酰胺和二碘甲烷液滴接触时的稳定性。研究的单层是单一组分饱和磷脂 1,2-二棕榈酰-sn-甘油-3-磷酸胆碱（DPPC）转移到云母表面上。当在这些系统中延长接触角测量时间时，由于与探测液体（特别是水）接触，DPPC 层结构会发生一些变化，这反映在测量接触角的变化上。通常，随着液滴滴在 DPPC 单层上的接触时间的增加，接触角减小。如果 DPPC 单层最初与水接触，则会观察到接触角下降与分子重排之间的某些相关性。另一方面，在最初的几秒钟内完成的接触角可以忠实地反映层的原始结构及其能量状态，因为在这段时间内结构变化不显著。基于测量的接触角，计算了单层的表观表面自由能及其组成部分，这些组成部分对应于液滴滴落的不同接触时间。这些结果有助于更好地描述与极性（水和甲酰胺）和非极性（二碘甲烷）液体接触的磷脂层中发生的过程。
