Abstract
Broadband SFG spectroscopy is shown to offer considerable advantages over scanning systems in terms of signal-to-noise ratios when probing well-formed single-component supported lipid bilayers formed from zwitterionic lipids with PC headgroups. The SFG spectra obtained from bilayers formed from DOPC, POPC, DLPC, DMPC, DPPC and DSPC show a common peak at ∼2980 cm-1, which is subject to interference between the C-H and the O-H stretches from the aqueous phase, while membranes having transition temperatures above the laboratory temperature produce SFG spectra with at least two additional peaks, one at ∼2920 cm-1 and another at ∼2880 cm-1. The results validate spectroscopic and structural data from SFG experiments utilizing asymmetric bilayers in which one leaflet differs from the other in the extent of deuteration. Differences in H2O-D2O exchange experiments reveal that the lineshapes of the broadband SFG spectra are significantly influenced by interference from OH oscillators in the aqueous phase, even when those oscillators are not probed by the incident infrared light in our broadband setup. In the absence of spectral interference from the OH stretches of the solvent, the alkyl chain terminal methyl group of the bilayer is found to be tilted at an angle of 15° to 35° from the surface normal.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 3063-3072 |
| Number of pages | 10 |
| Journal | Physical Chemistry Chemical Physics |
| Volume | 20 |
| Issue number | 5 |
| DOIs | |
| State | Published - Feb 7 2018 |
Funding
This research was made possible by the National Science Foundation Center for Chemical Innovation on Sustainable Nanomaterials (CSN) under Grant No. CHE-1503408. FMG gratefully acknowledges support from the Alexander von Humboldt Foundation. HMC and ACM gratefully acknowledge support through the NSF Graduate Research Fellowship Program. The research utilizing the Zetasizer Nano was performed in the Keck-II facility of NUANCE Center at Northwestern University. The NUANCE Center is supported by NSEC (NSF EEC-0647560), MRSEC (NSF DMR-1121262), the Keck Foundation, the State of Illinois, and Northwestern University. Fluorescence imaging was performed at the Biological Imaging Facility at Northwestern University, which acknowledges support from the Northwestern University Chemistry of Life Processes Institute and the North-western University Office for Research. Part of the research was performed at the Environmental Molecular Sciences Laboratory (EMSL), a national scientific user facility sponsored by the Department of Energy’s Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory. LF was the William Wiley postdoctoral fellow at EMSL, Yun Zhang was an Alternate Sponsored Fellow (ASF) at PNNL, and HFW was a chief scientist of the Physical & Computational Sciences Directorate at PNNL during this work. This research was made possible by the National Science Foundation Center for Chemical Innovation on Sustainable Nanomaterials (CSN) under Grant No. CHE-1503408. FMG gratefully acknowledges support from the Alexander von Humboldt Foundation. HMC and ACM gratefully acknowledge support through the NSF Graduate Research Fellowship Program. The research utilizing the Zetasizer Nano was performed in the Keck-II facility of NUANCE Center at Northwestern University. The NUANCE Center is supported by NSEC (NSF EEC-0647560), MRSEC (NSF DMR-1121262), the Keck Foundation, the State of Illinois, and Northwestern University. Fluorescence imaging was performed at the Biological Imaging Facility at Northwestern University, which acknowledges support from the Northwestern University Chemistry of Life Processes Institute and the Northwestern University Office for Research. Part of the research was performed at the Environmental Molecular Sciences Laboratory (EMSL), a national scientific user facility sponsored by the Department of Energy's Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory. LF was the William Wiley postdoctoral fellow at EMSL, Yun Zhang was an Alternate Sponsored Fellow (ASF) at PNNL, and HFW was a chief scientist of the Physical & Computational Sciences Directorate at PNNL during this work.
ASJC Scopus subject areas
- General Physics and Astronomy
- Physical and Theoretical Chemistry