Investigations of water structure at the solid/liquid interface in the presence of supported lipid bilayers by vibrational sum frequency spectroscopy

The structure of water was investigated at the quartz/water interface in the presence of supported lipid bilayers (SLBs) by the use of infrared-visible sum frequency spectroscopy. By varying the pH of the bulk solution and the charge on the SLB, changes in both ice-like and water-like peaks were observed in the OH stretch region with respect to the plain quartz/water interface. The oscillator strengths were most affected by applying charged SLBs, rather than bilayers that did not contain a net charge. Time-dependent studies of the ice-like peak intensity at pH 5.6 during the fusion of lipid vesicles to the bare quartz surfaces revealed that the formation rate of a negatively charged SLB was much slower than that of positively charged and neutral SLBs.