Collective Chain Dynamics in Lipid Bilayers by Inelastic X-Ray Scattering
We investigated the application of inelastic x-ray scattering (IXS) to lipid bilayers. This technique directly measures the dynamic structure factor S(q,{omega}) which is the space-time Fourier transform of the electron density correlation function of the measured system. For a multiatomic system, the analysis of S(q,{omega}) is usually complicated. But for multiple bilayers of lipid, S(q,{omega}) is dominated by chain-chain correlations within individual bilayers. Thus IXS provides a unique probe for the collective dynamics of lipid chains in a bilayer that cannot be obtained by any other method. IXS of dimyristoyl phosphatidylcholine and dimyristoyl phosphatidylcholine + cholesterol at two different concentrations were measured. S(q,{omega}) was analyzed by three-mode hydrodynamic equations, including a thermal diffusive mode and two propagating acoustic modes. We obtained the dispersion curves for the phonons that represent the collective in-plane excitations of lipid chains. The effect of cholesterol on chain dynamics was detected. Our analysis shows the importance of having a high instrument resolution as well as the requirement of sufficient signal-to-noise ratio to obtain meaningful results from such an IXS experiment. The requirement on signal-to-noise also applies to molecular dynamics simulations.
- Research Organization:
- Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS); Rice Univ.; Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- W-31-109-ENG-38
- OSTI ID:
- 15004074
- Journal Information:
- Biophysical Journal, Vol. 84, Issue 6; Related Information: Jun. 2003; ISSN 0006-3495
- Publisher:
- Elsevier
- Country of Publication:
- United States
- Language:
- ENGLISH
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