Evaluation of pH at Charged Lipid/Water Interfaces by Heterodyne-Detected Electronic Sum Frequency Generation.
Although the interface pH at a biological membrane is important for biological processes at the membrane, there has been no systematic study to evaluate it. We apply novel interface-selective nonlinear spectroscopy to the evaluation of the pH at model biological membranes (lipid/water interfaces). It is clearly shown that the pH at the charged lipid/water interfaces is substantially deviated from the bulk pH. The pH at the lipid/water interface is higher than that in the bulk when the head group of the lipid is positively charged, whereas the pH at the lipid/water interface is lower when the lipid has a negatively charged head group.
†Molecular Spectroscopy Laboratory, RIKEN, Wako, Saitama 351-0198, Japan.
Achintya
A
Kundu
†Molecular Spectroscopy Laboratory, RIKEN, Wako, Saitama 351-0198, Japan.
Shoichi
S
Yamaguchi
†Molecular Spectroscopy Laboratory, RIKEN, Wako, Saitama 351-0198, Japan.|‡Ultrafast Spectroscopy Research Team, RIKEN Center for Advanced Photonics (RAP), Wako, Saitama 351-0198, Japan.
Tahei
T
Tahara
charged lipid; heterodyne detection; lipid/water interface; pH; sum frequency generation