Orientation of 4'-Dihexylamino-4-Sulfoazobenzene Interacting with Phospholipid Monolayers Probed by Heterodyne-Detected Vibrational Sum Frequency Generation Spectroscopy
Related Experiment Video
Updated: Jul 6, 2026

Atomic Force Microscopy Imaging and Force Spectroscopy of Supported Lipid Bilayers
Published on: July 22, 2015
Masato Kondoh1, Ryosuke Shinoda1, Atsuya Momotake1
1Department of Chemistry, Graduate School of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba 305-8571, Japan.
Abstract:
Understanding the molecular-level interactions between membrane-binding dyes and lipid membranes is critical for advancing cellular imaging techniques. In this study, we applied heterodyne-detected vibrational sum frequency generation (HD-VSFG) spectroscopy to investigate the interaction between a water-soluble dye, 4'-dihexylamino-4-sulfoazobenzene (DHASA), and a Langmuir monolayer of the phospholipid, 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) at air/aqueous solution interfaces. HD-VSFG revealed a characteristic vibrational band around 1600 cm-1 from a phenyl ring stretching mode of DHASA when interacting with DPPC monolayers. This band was absent in both the spectrum of the air/DHASA aqueous solution interface without DPPC monolayers and that of DPPC monolayers on pure water, confirming its origin from the specific DHASA-DPPC interaction. Notably the 1600 cm-1 band intensity decreased with increasing DPPC surface density, suggesting that DHASA is incorporated into the DPPC monolayers with a preferred orientation at low densities but is excluded as density increases─a finding with significant implications for optimizing membrane-staining dye performance. Through polarization-dependent measurement, we determined that DHASA adopts a preferred orientation where the azobenzene moiety tilts approximately 45° from the interface normal, with the alkyl chains pointing toward the air phase, providing structural insights that may be informative for the future development of membrane-staining dyes.
More Related Videos
07:11Dissipative Microgravimetry to Study the Binding Dynamics of the Phospholipid Binding Protein Annexin A2 to Solid-supported Lipid Bilayers Using a Quartz Resonator
Published on: November 1, 2018
09:43Interfacial Molecular-level Structures of Polymers and Biomacromolecules Revealed via Sum Frequency Generation Vibrational Spectroscopy
Published on: August 13, 2019
Related Concept Videos
¹H NMR: Complex Splitting
Splitting diagrams or splitting tree diagrams are routinely used to depict such complex couplings. While drawing splitting diagrams, the splitting with the larger coupling constant is usually applied first.
¹H NMR of Conformationally Flexible Molecules: Temporal Resolution
NMR Spectroscopy of Benzene Derivatives
NMR Spectroscopy: Chemical Shift Overview
For instance, the proton...
¹H NMR Signal Integration: Overview
Spin–Spin Coupling Constant: Overview
Qualitatively, any spin plus-half nucleus polarizes the spins of its electrons to the minus-half state. Consequently, the paired electron in the hydrogen–carbon bond must have a...