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Watching individual molecules flex within lipid membranes using SERS.



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Taylor, Richard W 
Benz, Felix 
Sigle, Daniel O 
Bowman, Richard W 
Bao, Peng 


Interrogating individual molecules within bio-membranes is key to deepening our understanding of biological processes essential for life. Using Raman spectroscopy to map molecular vibrations is ideal to non-destructively 'fingerprint' biomolecules for dynamic information on their molecular structure, composition and conformation. Such tag-free tracking of molecules within lipid bio-membranes can directly connect structure and function. In this paper, stable co-assembly with gold nano-components in a 'nanoparticle-on-mirror' geometry strongly enhances the local optical field and reduces the volume probed to a few nm(3), enabling repeated measurements for many tens of minutes on the same molecules. The intense gap plasmons are assembled around model bio-membranes providing molecular identification of the diffusing lipids. Our experiments clearly evidence measurement of individual lipids flexing through telltale rapid correlated vibrational shifts and intensity fluctuations in the Raman spectrum. These track molecules that undergo bending and conformational changes within the probe volume, through their interactions with the environment. This technique allows for in situ high-speed single-molecule investigations of the molecules embedded within lipid bio-membranes. It thus offers a new way to investigate the hidden dynamics of cell membranes important to a myriad of life processes.



Fatty Acids, Monounsaturated, Gold, Lipid Bilayers, Metal Nanoparticles, Phosphatidylcholines, Quaternary Ammonium Compounds, Spectrum Analysis, Raman

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Springer Science and Business Media LLC
Engineering and Physical Sciences Research Council (EP/G060649/1)
European Research Council (320503)
Engineering and Physical Sciences Research Council (EP/L027151/1)
Biotechnology and Biological Sciences Research Council (BB/I022686/1)
We acknowledge financial support from EPSRC grant EP/G060649/1, EP/I012060/1, ERC grant LINASS 320503. FB acknowledges support from the Winton Programme for the Physics of Sustainability.