Biomolecular Structure at Interfaces Measured by Infrared Spectroscopy


Curtis W. Meuse Biomolecular Materials Group, National Institute of Standards and Technology (NIST)

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Cell membranes have many important biological functions such as controlling signal transduction and molecular transport between the inside and outside of cells.a

aThe specification of commercial products in this article is for clarity only and does not constitute endorsement by the National Institute of Standards and Technology.

A greater understanding of the structures and functions of the cell membrane components involved in signal transduction and/or molecular transport could be used to improve the delivery and specificity of pharmaceuticals.

Cell membranes are complex and dynamic structures generally described in terms of the “fluid mosaic” model. Like any theory, the “fluid mosaic” theory is still being refined. One way refinements are being tested is using nanotechnology to assemble biological and/or biomimetic components into membrane mimics to help clarify our understanding of cell membrane processes.

This article describes measurements characterizing a particular mimetic called a hybrid bilayer membrane (HBM). HBMs are surface-supported bilayers composed of a monolayer of alkanethiol, which is tightly bound to the surface through a strong association between sulfur and gold, and a second noncovalently bound monolayer of phospholipid. The nanometer-size scale of the membrane components makes the construction and characterization of these mimetic membranes dependant on sophisticated measurement technologies. Hybrid bilayers are analytically addressable by a wide range of surface analytical techniques such as surface plasmon resonance, impedance analysis, electrochemistry, infrared spectroscopy, atomic force microscopy, ellipsometry, and neutron reflectivity. While information from the spontaneously formed hybrid bilayers can be cross-referenced between different independent experiments, it is often desirable to obtain as much information as possible from a single technique. This article reviews the different types of information that can be obtained by using infrared spectroscopy to study the interfacial structures of hybrid bilayer membranes.