ASSESSING THE MOLECULAR-STRUCTURE OF ALKANETHIOL MONOLAYERS IN HYBRIDBILAYER-MEMBRANES WITH VIBRATIONAL SPECTROSCOPIES

Hybrid bilayer membranes (HBMs), consisting of a lipid monolayer cover ing a self-assembled alkanethiol monolayer on a metal surface, are use ful models for studying the structure and function of cell membranes. Surface-enhanced Raman spectroscopy (SERS) and reflection absorption i nfrared spectroscopy (RAIRS) are used to study HBMs with various alkan ethiol and lipid components. Together, these two techniques clearly in dicate that the lipid forms a well-ordered, non-interdigitated layer o n the alkanethiol with the head groups of the lipids oriented away fro m the metal surface. Both techniques reveal that the formation of an H EM produces small changes in the alkanethiols, which are similar to th ose caused by a reduction in temperature, indicative of an increase in order. The small magnitude of the perturbations in the alkanethiol mo nolayer upon addition of the lipid layer will simplify the further stu dy of HBMs.