Department of Earth and Space Science, Osaka University, 1-1 Machikaneyama-cho, Toyonaka, Osaka 560-0043, Japan; Taki Chemical Co., Ltd., 346 Miyanishi, Harima-cho, Kako-gun, Hyogo 675-0145, Japan.
Department of Earth and Space Science, Osaka University, 1-1 Machikaneyama-cho, Toyonaka, Osaka 560-0043, Japan.
Spectrochim Acta A Mol Biomol Spectrosc. 2020 Mar 5;228:117779. doi: 10.1016/j.saa.2019.117779. Epub 2019 Nov 9.
Adsorption of water to a phospholipid (lecithin) and a ceramide were studied by IR microspectroscopy equipped with a humidity control system and quartz crystal microbalance (QCM). The water weight ratios increase up to 12.2 wt% for lecithin and 1.2 wt% for ceramide at RH ~80%, with linear correlations with infrared OH (+NH) band areas. For lecithin, the 1230 cm band (PO) and the 1735 cm band (CO) shift to lower wavenumbers, while the 1060 cm band (PO, POC) shift to higher wavenumber with RH. Band areas of phosphates (1230 and 1060 cm) increase with RH showing positive relations with the band area of bound water. Bound water molecules with shorter H bonds might be bound to these phosphate groups. Band areas of aliphatic CHs are negatively correlated with the increasing adsorption of free water. Free water molecules with longer H bonds might interact loosely with aliphatic chains of lecithin. For ceramide, only the 1045 cm band (CO) shows a small red shift at higher RHs than 60%, indicating adsorption of bound water to CO bonds. Amounts of water molecules adsorbed to ceramide are very limited due to few adsorption of free water.
采用配备湿度控制系统和石英晶体微天平 (QCM) 的红外微光谱仪研究了水对磷脂 (卵磷脂) 和神经酰胺的吸附。在 RH~80%左右时，水的重量比增加到卵磷脂的 12.2 wt%和神经酰胺的 1.2 wt%，与红外 OH（+NH）带面积呈线性相关。对于卵磷脂，1230 cm 带（PO）和 1735 cm 带（CO）向低波数移动，而 1060 cm 带（PO、POC）随 RH 向高波数移动。磷酸盐（1230 和 1060 cm）的带面积随 RH 增加而增加，与结合水的带面积呈正相关。具有较短氢键的结合水分子可能与这些磷酸基团结合。脂肪族 CHs 的带面积与游离水的吸附增加呈负相关。具有较长氢键的游离水分子可能与卵磷脂的脂肪链松散相互作用。对于神经酰胺，只有在 RH 高于 60%时，1045 cm 带（CO）才会出现较小的红移，表明结合水吸附到 CO 键上。由于游离水的吸附量有限，神经酰胺吸附的水分子数量非常有限。
